U.S. patent application number 12/450784 was filed with the patent office on 2010-05-06 for methods and apparatus for electrodeionization.
This patent application is currently assigned to Trovion Pte. LTD.. Invention is credited to John M. Riviello.
Application Number | 20100108521 12/450784 |
Document ID | / |
Family ID | 39875807 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100108521 |
Kind Code |
A1 |
Riviello; John M. |
May 6, 2010 |
METHODS AND APPARATUS FOR ELECTRODEIONIZATION
Abstract
The present invention relates generally to the deionization of
liquids through the use of electrodeionization methods and
apparatuses. The apparatuses may be configured to minimize the
fouling of the electrode chambers and to provide continuous
regeneration of the ion exchange materials. The apparatuses may be
configured according to the desired levels of deionization for
anions, cations, or both. Finally, methods are presented for
various uses of the apparatuses.
Inventors: |
Riviello; John M.; (Los
Gatos, CA) |
Correspondence
Address: |
MICHAELSON & ASSOCIATES
P.O. BOX 8489
RED BANK
NJ
07701-8489
US
|
Assignee: |
Trovion Pte. LTD.
Singapore
SG
|
Family ID: |
39875807 |
Appl. No.: |
12/450784 |
Filed: |
April 17, 2008 |
PCT Filed: |
April 17, 2008 |
PCT NO: |
PCT/US2008/004930 |
371 Date: |
October 13, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60925249 |
Apr 19, 2007 |
|
|
|
Current U.S.
Class: |
204/632 |
Current CPC
Class: |
B01D 61/485 20130101;
C02F 1/4695 20130101; B01D 2313/30 20130101; B01D 2313/28 20130101;
B01D 61/48 20130101; B01D 61/44 20130101 |
Class at
Publication: |
204/632 |
International
Class: |
B01D 61/46 20060101
B01D061/46 |
Claims
1. An electrodeionization apparatus comprising: a. an anode chamber
101 including an anode therein; b. a first anion membrane 102
contiguous with the anode chamber 101; c. an anion depletion
chamber 103 contiguous with the first anion membrane 102, the anion
depletion chamber including therein anion exchange materials; d. a
second anion membrane 104 contiguous with the anion depletion
chamber 103; e. a composite bed depletion chamber 105 contiguous
with the second anion membrane 104, the composite bed concentrate
chamber including therein one of a doped anion exchange material,
or a doped cation exchange material; f. a first cation membrane 106
contiguous with the composite bed concentrate chamber 105; g. a
cation depletion chamber 107 contiguous with the first cation
membrane 106, the cation depletion chamber including therein cation
exchange materials; h. a second cation membrane 108 contiguous with
the cation depletion chamber 107; and i. a cathode chamber 109
contiguous with the second cation membrane 108 including a cathode
therein.
2. An electrodeionization apparatus comprising: a. an anode chamber
201, including an anode therein; b. a first anion membrane 202
contiguous with the anode chamber 201; c. an anodic composite bed
depletion chamber 203 contiguous with the first anion membrane 202,
the anodic composite bed depletion chamber including therein one of
a mixed ion exchange material, or a doped anion exchange material,
or a doped cation exchange material; d. a first cation membrane 204
contiguous with the anodic composite bed depletion chamber 203; e.
a cation depletion chamber 205 contiguous with the first cation
membrane 204, the cation depletion chamber including therein cation
exchange materials; f. a second cation membrane 206 contiguous with
the cation depletion chamber 205; g. a composite bed concentrate
chamber 207 contiguous with the second cation membrane 206, the
composite bed concentrate chamber including therein one of a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material; h. a second anion membrane 208
contiguous with the composite bed concentrate chamber 207; i. an
anion depletion chamber 209 contiguous with the second anion
membrane 208, the anion depletion chamber including therein anion
exchange materials; j. a third anion membrane 210 contiguous with
the anion depletion chamber 209; k. a cathodic composite bed
depletion chamber 211 contiguous with the third anion membrane 210,
the cathodic composite bed depletion chamber including therein one
of a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material; l. a third cation
membrane 212 contiguous with the cathodic composite bed depletion
chamber 211; and m. a cathode chamber 213 contiguous with the third
cation membrane 212, the cathode chamber including therein a
cathode.
3. An electrodeionization apparatus comprising: a. an anode chamber
220 including an anode chamber therein; b. a first cation membrane
221 contiguous with the anode chamber 220; c. an anodic composite
bed concentrate chamber 222 contiguous with the first cation
membrane 221, the anodic composite bed concentrate chamber
including therein one of a mixed ion exchange material, or a doped
anion exchange material, or a doped cation exchange material; d. a
first anion membrane 223 contiguous with the anodic composite bed
concentrate chamber 222; e. an anion depletion chamber 224
contiguous with the first anion membrane 223, the anion depletion
chamber including therein anion exchange materials; f. a second
anion membrane 225 contiguous with the anion depletion chamber 224;
g. a composite bed depletion chamber 226 contiguous with the second
anion membrane 225, the composite bed concentrate including therein
one of a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material; h. a second cation
membrane 227 contiguous with the composite bed depletion chamber
226; i. a cation depletion chamber 228 contiguous with the second
cation membrane 227, the cation depletion chamber including therein
cation exchange materials; j. a third cation membrane 229
contiguous with the cation depletion chamber 228; k. a cathodic
composite bed concentrate chamber 230 contiguous with the third
cation membrane 229, the cathodic composite bed concentrate chamber
including therein one of a mixed ion exchange material, or a doped
anion exchange material, or a doped cation exchange material; l. a
third anion membrane 231 contiguous with the cathodic composite bed
concentrate chamber 230; and m. a cathode chamber 232 contiguous
with the third anion membrane 231 including a cathode therein.
4. An electrodeionization apparatus comprising: a. an anode chamber
240 including an anode therein; b. a first cation membrane 241
contiguous with the anode chamber 240; c. a anodic concentrate
chamber 242 contiguous with the first cation membrane 241, the
anodic concentrate chamber including therein one of a homogeneous
volume of anion exchange material, or a homogeneous volume of
cation exchange material, or a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange material;
d. a first anion membrane 243 contiguous with the anodic
concentrate chamber 242; e. an anion depletion chamber 244
contiguous with the first anion membrane 243, the anion depletion
chamber including therein anion exchange materials; f. a second
anion membrane 245 contiguous with the anion depletion chamber 244;
g. a composite bed depletion chamber 246 contiguous with the second
anion membrane 245, the composite bed depletion chamber including
therein one of a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material; h. a second
cation membrane 247 contiguous with the composite bed depletion
chamber 246; i. a cation depletion chamber 248 contiguous with the
second cation membrane 247, the cation depletion chamber including
therein cation exchange materials; j. a third cation membrane 249
contiguous with the cation depletion chamber 248; k. an cathodic
concentrate chamber 250 contiguous with the third cation membrane
249, the cathodic concentrate chamber including therein one of a
homogeneous volume of anion exchange material, or a homogeneous
volume of cation exchange material, or a mixed ion exchange
material, or a doped anion exchange material, or a doped cation
exchange material; l. a third anion membrane 251 contiguous with
the cathodic concentrate chamber 250; and m. a cathode chamber 252
contiguous with the third anion membrane 251 including a cathode
therein.
5. An electrodeionization apparatus comprising: a. an anode chamber
301 including an anode therein; b. a first anion membrane 302
contiguous with the anode chamber 301; c. an anodic composite bed
depletion chamber 303 contiguous with the first anion membrane 302,
the anodic composite bed depletion chamber including therein one of
a mixed ion exchange material, or a doped anion exchange material,
or a doped cation exchange material; d. a first cation membrane 304
contiguous with the anodic composite bed depletion chamber 303; e.
a cation depletion chamber 305 contiguous with the first cation
membrane 304, the cation depletion chamber including therein cation
exchange materials; f. a second cation membrane 306 contiguous with
the cation depletion chamber 305; g. a composite bed concentrate
chamber 307 contiguous with the second cation membrane 306, the
composite bed concentrate chamber including therein one of a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material; h. a second anion membrane 308
contiguous with the composite bed concentrate chamber 307; i. an
anion depletion chamber 309 contiguous with the second anion
membrane 308, the anion depletion chamber including therein anion
exchange materials; j. a third anion membrane 310 contiguous with
the anion depletion chamber 309; and k. a cathode chamber 311
contiguous with the third cation membrane 310 including a cathode
therein.
6. An electrodeionization apparatus comprising: a. an anode chamber
320 including an anode therein; b. a first anion membrane 321
contiguous with the anode chamber 320; c. an anion depletion
chamber 322 contiguous with the first anion membrane 321, the anion
depletion chamber including therein anion exchange materials; d. a
second anion membrane 323 contiguous with the anion depletion
chamber 322; e. a composite bed depletion chamber 324 contiguous
with the second anion membrane 323, the composite bed depletion
chamber including therein one of a mixed ion exchange material, or
a doped anion exchange material, or a doped cation exchange
material; f. a first cation membrane 325 contiguous with the
composite bed depletion chamber 324; g. a cation depletion chamber
326 contiguous with the first cation membrane 325, the cation
depletion chamber including therein cation exchange materials; h. a
second cation membrane 327 contiguous with the cation depletion
chamber 326; i. a cathodic composite bed concentrate chamber 328
contiguous with the second cation membrane 327, the cathodic
composite bed concentrate chamber including therein a mixed ion
exchange material, or a doped anion exchange material, or a doped
cation exchange material; j. a third anion membrane 329 contiguous
with the cathodic composite bed concentrate chamber 328; and k. a
cathode chamber 330 contiguous with the third anion membrane 329
including a cathode therein.
7. An electrodeionization apparatus comprising: a. an anode chamber
340 including an anode therein; b. a first anion membrane 341
contiguous with the anode chamber 340; c. an anion depletion
chamber 342 contiguous with the first anion membrane 341, the anion
depletion chamber including therein anion exchange materials; d. a
second anion membrane 343 contiguous with the anion depletion
chamber 342; e. a composite bed depletion chamber 344 contiguous
with the second anion membrane 343, the composite bed depletion
chamber including therein one of a mixed ion exchange material, or
a doped anion exchange material, or a doped cation exchange
material; f. a first cation membrane 345 contiguous with the
composite bed depletion chamber 344; g. a cation depletion chamber
346 contiguous with the first cation membrane 345, the cation
depletion chamber including therein cation exchange materials; h. a
second cation membrane 347 contiguous with the cation depletion
chamber 346; i. an cathodic concentrate chamber 348 contiguous with
the second cation membrane 347, the cathodic concentrate chamber
including therein one of a homogeneous volume of anion exchange
material, or a homogeneous volume of cation exchange material, or a
mixed ion exchange material, or a doped anion exchange material, or
a doped cation exchange material; j. a third anion membrane 349
contiguous with the cathodic concentrate chamber 348; and k. a
cathode chamber 350 contiguous with the third anion membrane 349
including a cathode therein.
8. An electrodeionization apparatus comprising: a. an anode chamber
401 including an anode therein; b. a first cation membrane 402
contiguous with the anode chamber 401; c. a cation depletion
chamber 403 contiguous with the first cation membrane 402, the
cation depletion chamber including therein cation exchange
materials; d. a second cation membrane 404 contiguous with the
cation depletion chamber 403; e. a composite bed concentrate
chamber 405 contiguous with the second cation membrane 404, the
composite bed concentrate chamber including therein one of a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material; f. a first anion membrane 406
contiguous with the composite bed concentrate chamber 405; g. an
anion depletion chamber 407 contiguous with the first anion
membrane 406, the anion depletion chamber including therein anion
exchange materials; h. a second anion membrane 408 contiguous with
the anion depletion chamber 407; i. a cathodic composite bed
depletion chamber 409 contiguous with the second anion membrane
408, the cathodic composite bed depletion chamber including therein
one of a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material; j. a third cation
membrane 410 contiguous with the cathodic composite bed depletion
chamber 409; and k. a cathode chamber 411 contiguous with the third
cation membrane 410 including a cathode therein.
9. An electrodeionization apparatus comprising: a. an anode chamber
420 including an anode; b. a first cation membrane 421 contiguous
with the anode chamber 420; c. an anodic composite bed concentrate
chamber 422 contiguous with the first cation membrane 421, the
anodic composite bed concentrate chamber including therein one of a
mixed ion exchange material, or a doped anion exchange material, or
a doped cation exchange material; d. a first anion membrane 423
contiguous with the anodic composite bed concentrate chamber 422;
e. an anion depletion chamber 424 contiguous with the first anion
membrane 423, the anion depletion chamber including therein anion
exchange materials; f. a second anion membrane 425 contiguous with
the anion depletion chamber 424; g. a composite bed depletion
chamber 426 contiguous with the second anon membrane 425, the
composite bed depletion chamber including therein one of a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material; h. a second cation membrane 427
contiguous with the composite bed depletion chamber 426; i. an
cation depletion chamber 428 contiguous with the second cation
membrane 427, the cation depletion chamber including therein cation
exchange materials; j. a third cation membrane 429 contiguous with
the cation depletion chamber 428; and k. a cathode chamber 430
contiguous with the third cation membrane 429 including a
cathode.
10. An electrodeionization apparatus comprising: a. an anode
chamber 440 including an anode therein; b. a first cation membrane
441 contiguous with the anode chamber 440; c. an anodic concentrate
chamber 442 contiguous with the first cation membrane 441, the
anodic concentrate chamber including therein one of a homogeneous
volume of anion exchange material, or a homogeneous volume of
cation exchange material, or a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange material;
d. a first anion membrane 443 contiguous with the anodic
concentrate chamber 442; e. an anion depletion chamber 444
contiguous with the first anion membrane 443, the anion depletion
chamber including therein anion exchange materials; f. a second
anion membrane 445 contiguous with the anion depletion chamber 444;
g. a composite bed depletion chamber 446 contiguous with the second
anion membrane 445, the composite bed depletion chamber including
therein one of a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material; h. a second
cation membrane 447 contiguous with the composite bed depletion
chamber 446; i. an cation depletion chamber 448 contiguous with the
second cation membrane 447, the cation depletion chamber including
therein cation exchange materials; j. a third cation membrane 449
contiguous with the cation depletion chamber 448; and k. a cathode
chamber 450 contiguous with the third cation membrane 449 including
a cathode therein.
11. An electrodeionization apparatus comprising: a. an anode
chamber 501 including an anode therein; b. a first anion membrane
502 contiguous with the anode chamber 501; c. an anion depletion
chamber 503 contiguous with the first anion membrane 502, the anion
depletion chamber including therein anion exchange materials; d. a
second anion membrane 504 contiguous with the anion depletion
chamber 503; e. a cathodic composite bed depletion chamber 505
contiguous with the second anion membrane 504, the cathodic
composite bed depletion chamber including therein one of a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material; f. a cation membrane 506 contiguous
with the composite bed depletion chamber 505; and g. a cathode
chamber 507 contiguous with the cation membrane 506 including a
cathode therein.
12. An electrodeionization apparatus comprising: a. an anode
chamber 601 including an anode; b. a first anion membrane 602
contiguous with the anode chamber 601; c. an anodic composite bed
depletion chamber 603 contiguous with the first anion membrane 602,
the anodic composite bed depletion chamber including therein one of
a mixed ion exchange material, or a doped anion exchange material,
or a doped cation exchange material; d. a first cation membrane 604
contiguous with the anodic composite bed depletion chamber 603; e.
a cation depletion chamber 605 contiguous with the first cation
membrane 604, the cation depletion chamber including therein cation
exchange materials; f. a second cation membrane 606 contiguous with
the cation depletion chamber 605; and g. a cathode chamber 607
contiguous with the second cation membrane 606 including a cathode
therein.
13. An electrodeionization apparatus comprising: a. an anode
chamber 701 including an anode therein; b. a first cation membrane
702 contiguous with the anode chamber; c. a cation depletion
chamber 703 contiguous with the first cation membrane 702, the
cation depletion chamber including therein cation exchange
materials; d. a second cation membrane 704 contiguous with the
cathodic composite bed depletion chamber 703; e. a composite bed
concentrate chamber 705 contiguous with the second cation membrane
704, the composite bed concentrate chamber including therein one of
a mixed ion exchange material, or a doped anion exchange material,
or a doped cation exchange material; f. an anion membrane 706
contiguous with the composite bed concentrate chamber 705; g. a
cathodic composite bed depletion chamber 707 contiguous with the
anion membrane 706, the cathodic composite bed depletion chamber
including therein one of a mixed ion exchange material, or a doped
anion exchange material, or a doped cation exchange material; h. a
third cation membrane 708 contiguous with the cation composite bed
depletion chamber 707; and i. a cathode chamber 709 contiguous with
the third cation membrane 708 including a cathode therein.
14. An electrodeionization apparatus comprising: a. an anode
chamber 801 including an anode therein; b. a first anion membrane
802 contiguous with the anode chamber 801; c. an anodic composite
bed depletion chamber 803 contiguous with the first anion membrane
802, the anodic composite bed depletion chamber including therein
one of a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material; d. a cation membrane
804 contiguous with the anodic composite bed depletion chamber 803;
e. a composite bed concentrate chamber 805 contiguous with the
cation membrane 804, the composite bed concentrate chamber
including therein one of a mixed ion exchange material, or a doped
anion exchange material, or a doped cation exchange material; f. a
second anion membrane 806 contiguous with the composite bed
concentrate chamber 805; g. an anion depletion chamber 807
contiguous with the second anion membrane 806, the anion depletion
chamber including therein anion exchange materials; h. a third
anion membrane 808 contiguous with the anion depletion chamber 807;
and a cathode chamber 809 contiguous with the third cation membrane
808 including a cathode therein.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to the field of
deionization of liquids, in particular to water purification
through deionization. More specifically, the present invention
pertains to electrodeionization (EDI) apparatuses and various
methods of using the same, directing liquid through the apparatuses
in different ways to achieve different deionization
characteristics.
BACKGROUND OF THE INVENTION
[0002] Electrodeionization (EDI) is known in the art as a process
which removes ionized species from liquids, such as water, using
electrically active media and an electric potential to influence
ion transport. Examples of electrically active media comprise ion
exchange materials and ion exchange membranes. In general "ion
exchange materials" denotes solid (perhaps highly porous) materials
that, when brought into contact with a liquid, cause ions in the
liquid to be interchanged with ions in the exchange material. "Ion
exchange membrane" or "ion selective membrane" generally denotes a
membrane porous to some ions, perhaps containing ion exchange
sites, and useful for controlling the flow of ions across the
membrane, typically permitting the passage of some types of ions
while blocking others. In general, ion exchange membranes
selectively permit the transport of some types of ions and not
others, and also block the passage of the bulk liquid carrying the
ions. A combination of ion selective membranes and ion exchange
materials are sandwiched between two electrodes (anode (+) and
cathode (-)) under a direct current (DC) electric field to remove
ions from the liquid. The electric field may be applied in a
continuous manner or may be applied in an intermittent manner.
Cationic exchange materials (or cation materials for short) can be
used to remove positively charged ions, such as calcium, magnesium,
sodium, among others, replacing them with hydronium (H.sub.3O.sup.+
or H.sup.+) ions. Anionic exchange materials (or anion materials
for short) can be used to remove negatively charged ions, such as
chloride, nitrate, silica, among others, replacing them with
hydroxide ions. The hydronium and hydroxide ions may subsequently
be united to form water molecules. Eventually, the ion exchange
materials become saturated with contaminant ions and become less
effective at treating the liquid. Once these materials are
significantly contaminated, high-purity liquid flowing past them
may acquire trace amounts of contaminant ions by "displacement
effects." In conventional deionization, the saturated (or
exhausted) ion exchange media must be chemically recharged or
regenerated periodically with a strong acid (for cation materials)
or a strong base (for anion materials). The process of regenerating
the ion exchange media with concentrated solutions of strong acids
or strong bases presents considerable cost, time, safety, and waste
disposal issues.
[0003] Continuous electrodeionization (CEDI), a subset of EDI, uses
a combination of ion exchange materials and ion exchange membranes,
and direct current in a manner so as to continuously deionize
liquids and also to eliminate the need to chemically regenerate the
ion exchange media. The "continuous" label of CEDI applies to the
condition wherein the electric field may be applied to the
apparatus in a continuous manner while product liquid is being
produced. CEDI includes processes such as continuous deionization,
filled cell electrodialysis, or electrodiaresis. The ionic
transport properties of electrically active media are an important
separation parameter.
[0004] In the EDI apparatus illustrated FIG. 1, contaminant ions
migrate through the ion depletion chambers 103, 107 and into the
electrode chambers 101, 109. The ion exchange materials in the
composite bed depletion chamber 105, anion depletion chamber 103
and cation depletion chamber 107 are regenerated by water splitting
in the composite bed depletion chamber 105. Hydronium produced from
water splitting migrates towards the cathode passing though the
cation exchange membrane 106 of the composite bed depletion chamber
105, into the cation depletion chamber 107 and ultimately into the
cathode chamber 109. Similarly, hydroxide produced from water
splitting migrates towards the anode passing though the anion
exchange membrane 104 of the composite bed depletion chamber 105,
into the anion depletion chamber 103 and ultimately into the anode
chamber 101. Electrochemically produced hydronium, which results
from oxidation of water at the anode, maintains electroneutrality
as hydroxide and contaminant anions migrate into the anode chamber.
Similarly, electrochemically produced hydroxide, which results from
the reduction of water at the cathode, maintains electroneutrality
as hydronium and contaminant cations migrate into the cathode
chamber. In the apparatus illustrated in FIG. 1, the feed water
hardness must be less than about 1-2 parts-per-million (ppm) (as
CaCO.sub.3), otherwise precipitation of calcium as calcium
carbonate or magnesium as magnesium hydroxide may occur in the
cathode chamber causing an increase in device resistance or an
increase in the backpressure, decreased flow, and potential
plugging in the apparatus. By flowing the electrode rinse first
through the anode chamber and then through the cathode chamber, the
hardness problem may be reduced since the anode electrode rinse is
slightly acidic and thus will help minimize precipitation of
calcium carbonate and magnesium hydroxide. Still, feed water with
hardness above several ppm (as CaCO.sub.3) can cause problems in
the apparatus. Another potential problem with this apparatus can
occur in the anode chamber. Common anions such as chloride and
nitrate can be oxidized in the anode chamber to form
electrochemically active species (ClO.sub.2 and NO.sub.2,
respectively). These electrochemically active species can damage
the ion exchange material in the anode chamber resulting in
decreased lifetime of the EDI apparatus.
[0005] Thus, there is a need for an EDI apparatus which reduces or
overcomes problems arising from electrode fouling by precipitation
or damage to the ion exchange materials of the electrode
compartment by electrochemically active compounds (such as
oxidizers) while maintaining some or all of the advantages of
homogeneous-material ion depletion chambers.
[0006] FIG. 1 illustrates an EDI apparatus that may be used for
"general purpose" liquid deionization. The apparatus comprises
three ion depletion chambers, 103, 105, 107, and two electrode
chambers, 101, 109, separated by four ion exchange membranes, 102,
104, 106, and 108. This configuration offers improved deionization
capability but may add additional complexity or cost for
applications where the deionization requirement is selective. For
some applications, the required water purity may require the
exhaustive removal of anions or cations, but not both. This is the
case in many forms of chemical analysis where a specific element or
ion or a group of elements or ions are of interest. For example, in
ion chromatography, either anions or cations are typically analyzed
using different chemistries. For anion analysis by ion
chromatography, the water used to prepare eluent or dilute samples
or standards should be free of all anions as any anion in the water
will likely manifest itself and either affect calibration (non-zero
intercept) or compromise detection by increasing background
conductivity. Other examples requiring feed water sources free from
specific ions are silicate analyzers, sodium analyzers or phosphate
analyzers as typically used to monitor high purity water. In these
applications, the primary requirement is that the feed water has
concentrations of the analyte(s) at or near the lowest possible
levels, typically sub-ppb (part-per-billion) or ppt
(part-per-trillion). Since many of these analyzers are used on-line
(continuous analysis), it is desirable to have a continuous, highly
purified feed water source for the analyzer. Currently, there are
no commercially available water purifiers which can easily
interface with analytical instruments and supply feed water with
extremely low contaminant levels of the analyte ions. Therefore,
there is a need for a simple, cost-effective EDI apparatus that may
be devoted to a specific purpose.
SUMMARY OF THE INVENTION
[0007] Accordingly and advantageously the present invention
discloses methods and apparatuses that may address one or more of
the issues discussed above. In some embodiments of the present
invention, a composite bed concentrate chamber is used to collect
and remove the contaminant ions from the liquid. The contaminant
ions are hindered from entering the electrode chambers, thus
reducing the electrode fouling associated with conventional EDI
apparatuses.
[0008] In other embodiments of the present invention, the ion
exchange efficiency of chambers including homogeneous ion exchange
materials may be combined with the benefits of chambers or layers
including composite anion-cation ion exchange materials to produce
liquids with very low concentrations of contaminant ions. In some
embodiments of the present invention, the interface between
adjacent layers may be transverse to the applied electric field. In
some embodiments of the present invention, the interface between
adjacent layers may be parallel to the applied electric field.
[0009] These and other advantages are achieved in accordance with
the present invention as described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. The drawings are not to scale and
the relative dimensions of various elements in the drawings are
depicted schematically and not to scale.
[0011] In the configurations disclosed below, liquid streams flow
through the electrode chambers and "concentrate" chambers. In the
following configurations, the electrode chambers may act as
concentrate chambers or as a source of hydronium and hydroxide ions
for regeneration of the ion exchange materials. As concentrate
chambers, contaminant ions may eventually migrate into the
electrode chambers (under the force of the applied electric field)
and may be removed from the electrode chamber by a liquid flow
stream. The electrode chamber flow streams may typically be
directed to waste. For simplicity of the drawings, the electrode
chamber and concentrate chamber rinse streams are not shown.
[0012] The techniques of the present invention may be readily
understood by considering the following detailed description in
conjunction with the accompanying drawings, in which:
[0013] FIG. 1 is a schematic representation of an EDI
configuration.
[0014] FIG. 2A-2D are schematic representations of EDI
configurations of embodiments of the present invention.
[0015] FIG. 3A-3C are schematic representations of EDI
configurations of embodiments of the present invention.
[0016] FIG. 4A-4C are schematic representations of EDI
configurations of embodiments of the present invention.
[0017] FIG. 5 is a schematic representation of an EDI configuration
of one embodiment of the present invention.
[0018] FIG. 6 is a schematic representation of an EDI configuration
of one embodiment of the present invention.
[0019] FIG. 7 is a schematic representation of an EDI configuration
of one embodiment of the present invention.
[0020] FIG. 8 is a schematic representation of an EDI configuration
of one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Abbreviations and Definitions
[0021] The following abbreviations and definitions are used
herein:
[0022] The abbreviation "EDI"=electrodeionization;
[0023] The abbreviation "CEDI"=continuous electrodeionization;
[0024] The abbreviation "IC"=ion chromatography;
[0025] The abbreviation "AM"=anion exchange membrane;
[0026] The abbreviation "CM"=cation exchange membrane;
[0027] The term "applied electric field" is understood to be the
electric field arising from a voltage applied between the anode and
the cathode within the EDI apparatus.
[0028] In FIGS. 1-8, the anode chamber has been labeled as "anode"
for brevity.
[0029] In FIGS. 1-8, the cathode chamber has been labeled as
"cathode" for brevity.
[0030] The term "depletion chamber" is defined as a chamber through
which the product liquid stream flows during one of the steps of
the process. A depletion chamber may be filled with one of a
homogeneous volume of anion exchange material, or a homogeneous
volume of cation exchange material, or a mixed ion exchange
material, or a doped anion exchange material, or a doped cation
exchange material, or may be comprised of "layers" of various ion
exchange materials.
[0031] The abbreviation "LDC"=layered depletion chamber which is a
specific type of "depletion chamber" and is defined as a chamber
that comprises "layers" of various ion exchange materials wherein
the liquid to be processed flows through the layers in a sequential
manner.
[0032] The term "concentrate chamber" is defined as a chamber
wherein the product liquid stream does not flow. Typical examples
of a concentrate chamber include an electrode chamber (either anode
or cathode), an anodic concentrate chamber (a chamber located
adjacent to the anode chamber and separated therefrom by an ion
exchange membrane), or a cathodic concentrate chamber (a chamber
located adjacent to the cathode chamber and separated therefrom by
an ion exchange membrane), or a central concentrate chamber
(wherein the concentrate chamber is not adjacent to an electrode
chamber), among others. Typically, in some embodiments of the
present invention, the electrode chambers (either anode or
cathode), are not filled with ion exchange material. A concentrate
chamber may be filled with a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange
material.
[0033] The term "mixed ion exchange material" is defined as a
mixture of anion and cation exchange materials wherein the anion
exchange material is responsible for about 50% of the total ion
exchange capacity and the cation exchange material is responsible
for about 50% of the total ion exchange capacity. The term "mixed
ion exchange material" also refers to a chamber that contains a
mixture of anion and cation exchange materials wherein the anion
exchange material is responsible for a range of about 40% to about
60% of the total ion exchange capacity and the cation exchange
material is responsible for the balance of the total ion exchange
capacity. This definition is meant to be consistent with the
conventional understanding of a "mixed bed" as containing a 50/50
mixture of anion/cation ion exchange materials as well as a small
range, typically from .about.40% to .about.60% on either side of
the 50/50 mixture.
[0034] The abbreviation "ACC"=anodic concentrate chamber which is
defined as a concentrate chamber adjacent to the anode and
separated from the anode by an ion exchange membrane. The ACC may
contain a homogeneous volume of anion exchange material, or a
homogeneous volume of cation exchange material, or a mixed ion
exchange material, or a doped anion exchange material, or a doped
cation exchange material. This is a chamber wherein the product
liquid stream does not flow.
[0035] The abbreviation "CCC"=cathodic concentrate chamber which is
defined as a concentrate chamber adjacent to the cathode and
separated from the cathode by an ion exchange membrane. The CCC may
contain a homogeneous volume of anion exchange material, or a
homogeneous volume of cation exchange material, or a mixed ion
exchange material, or a doped anion exchange material, or a doped
cation exchange material. This is a chamber wherein the product
liquid stream does not flow.
[0036] The abbreviation "ADC"=anion depletion chamber is defined as
a chamber that includes therein a homogeneous volume of anion
exchange material. These chambers have been labeled as "anion bed"
in the legend of FIGS. 1-8 for brevity.
[0037] The abbreviation "CDC"=cation depletion chamber is defined
as a chamber that includes therein a homogeneous volume of cation
exchange material. These chambers have been labeled as "cation bed"
in the legend of FIGS. 1-8 for brevity.
[0038] The abbreviation "CBCC"=composite bed concentrate chamber. A
composite bed concentrate chamber may be filled with a mixed ion
exchange material, or a doped anion exchange material, or a doped
cation exchange material.
[0039] The abbreviation "ACBCC"=anodic composite bed concentrate
chamber is defined as the composite bed concentrate chamber
adjacent to the anode and separated from the anode by an ion
exchange membrane. The ion exchange membrane may be an AM or a CM.
The ACBCC chamber may be filled with a mixed ion exchange material,
or a doped anion exchange material, or a doped cation exchange
material.
[0040] The abbreviation "CCBCC"=cathodic composite bed concentrate
chamber is defined as the composite bed concentrate chamber
adjacent to the cathode and separated from the cathode by an ion
exchange membrane. The ion exchange membrane may be an AM or a CM.
The CCBCC chamber may be filled with a mixed ion exchange material,
a doped anion exchange material, or a doped cation exchange
material.
[0041] The abbreviation "ACBDC"=anodic composite bed depletion
chamber is defined as the composite bed depletion chamber adjacent
to the anode and separated from the anode by an ion exchange
membrane. The ion exchange membrane may be an AM or a CM. The ACBDC
chamber may be filled with a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange
material.
[0042] The abbreviation "CCBDC"=cathodic composite bed depletion
chamber is defined as the composite bed depletion chamber adjacent
to the cathode and separated from the cathode by an ion exchange
membrane. The ion exchange membrane may be an AM or a CM. The CCBDC
chamber may be filled with a mixed ion exchange material, a doped
anion exchange material, or a doped cation exchange material.
[0043] The abbreviation "CBDC"=composite bed depletion chamber is
defined as the composite bed depletion chamber that is not adjacent
to either the cathode chamber or the anode chamber. The CBDC
chamber may be filled with a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange
material.
[0044] The terms "dopant" and "doping agent" refer to a material
that is added to another material. In EDI, a dopant may include
materials such as an inert material, an electrically active non-ion
exchange material (for example, a metal material), ion exchange
materials, or mixtures thereof. Typically, ion exchange material,
such as anion exchange materials or cation exchange materials is
added to a volume of the opposite ion exchange materials to adjust
the electrical conductivity. In some instances, doping of ion
exchange materials facilitate the transport of contaminant ions or
may provide for water splitting which can produce regenerant ions
(hydronium and hydroxide).
[0045] The term "doped cation exchange material" is defined as a
composite of anion and cation exchange materials wherein the cation
exchange material is responsible for at least about 60% of the
total ion exchange capacity and the remainder of the total ion
exchange capacity is contributed by anion exchange material. That
is, the mixture is primarily a cation exchange material. This
definition is meant to distinguish a "doped cation exchange
material" from the conventional understanding of a "mixed ion
exchange bed" (or material)". That is, "mixed ion exchange material
(or bed)" is used herein to denote a bed having approximately equal
cation and anion ion exchange capacities (typically equal to within
about .+-.10%) while "doped cation exchange material" denotes an
ion exchange material in which cation exchange clearly predominates
and the anion exchange material is a "dopant" or minority
contributor. The doped cation exchange materials may be
advantageous in that they can be used to alter the conductivity
through the EDI apparatus and improve the performance of the EDI
apparatus.
[0046] The term "doped anion exchange material" is defined in a
complimentary manner to "doped cation exchange material" described
above. That is, "doped anion exchange material" is a composite of
anion and cation exchange materials wherein the anion exchange
material is responsible for at least about 60% of the total ion
exchange capacity and the remainder of the total ion exchange
capacity is contributed by the cation exchange material. That is,
the mixture is primarily an anion exchange material. This
definition is meant to distinguish a "doped anion exchange
material" from the conventional understanding of a "mixed ion
exchange bed". The doped anion exchange materials may be
advantageous in that they can be used to alter the conductivity
through the EDI apparatus and improve the performance of the EDI
apparatus.
[0047] The terms "hard" and "hardness" when used in reference to
water, indicates water that contains concentrations (typically
expressed in parts-per-million, (ppm)) of various minerals, such as
calcium and magnesium carbonates, bicarbonates, sulfates, or
chlorides. The presence of such dissolved minerals typically arises
from prolonged contact with rocky substrates and soils. Such
hardness in water tends to discolor, scale, and corrode
materials.
[0048] The term "scale" refers to a solid deposit on a surface in
contact with a liquid in which the deposit includes mineral
compounds present in the liquid, e.g., calcium carbonate.
[0049] The term "water splitting" refers to the hydrolysis of water
to hydronium and hydroxide ions, which occurs at the interface of
anion exchange materials and cation exchange materials in the
presence of an electric potential. This is not a true
electrochemical process, and differs from the electrolysis of water
at an electrode in that water splitting does not produce hydrogen
or oxygen gas whereas conventional electrolysis of water produces
both gases.
[0050] The terms "eluant" and "eluent" refer to a substance used to
effect the separation of ions from a separation column in an
elution process. Examples of eluents include, but are not limited
to, an acid or a base.
[0051] The term "elution" refers to the process of using an eluent
to extract ions from a separation column.
[0052] The term "eluate" refers to the product or substance that is
separated from a column in an elution process.
[0053] After considering the following description, those skilled
in the art will clearly realize that the teachings of the invention
can be readily utilized in liquid purification, specifically
deionization, through the use of various EDI apparatuses and
methods in various ways.
[0054] Two earlier patent applications are assigned to the Assignee
of the present invention and describe five chambered EDI
apparatuses. One is entitled "Method of Ion Chromatography wherein
a Specialized Electrodeionization Apparatus is Used" (application
Ser. No. 11/403,737) and published as US 2006/0231404. The other is
entitled "Chambered Electrodeionization Apparatus with Uniform
Current Density, and Method of Use" (application Ser. No.
11/403,734 and published as US 2006/0231403). The entire contents
of both applications are hereby incorporated herein by reference in
their entirety.
[0055] A related patent application filed concurrently herewith and
entitled "Methods and Apparatus for Electrodeionization Utilizing
Layered Chambers" is assigned to the Assignee of the present
invention. The entire contents of this application are hereby
incorporated herein by reference in its entirety.
[0056] The types of ion exchange materials that are typically of
the most interest for the deionizations described herein are strong
acid cation exchange materials and strong base anion exchange
materials. The strong acid cation exchange material advantageously
has a sulfonate-type ion exchange site (or functional group) while
the anion exchange material typically has a quaternary amine ion
exchange site (or functional group). There are different types of
cation and anion exchange materials which are not inherently
excluded from use in connection with the deionizations described
herein, but one type of cation exchange material and one type of
anion exchange material as described are typically found to provide
adequate performance in practice and are generally used.
[0057] If the anion exchange material and cation exchange material
are mixed in the desired ratio of substantially equal cation and
anion exchange capacities, this is referred to as a "mixed" bed.
This comports with the conventional understanding of a "mixed bed
ion exchange material" as an ion exchange material that has
approximately equal anion and cation exchange capacity with one
type of anion exchange material and one type of cation exchange
material. This is typically achieved by mixing a cation exchange
material (typically a cation exchange resin) with an anion exchange
material (typically an anion exchange resin) in a ratio such that
the cation and anion exchange capacities of the final mixture are
roughly equal. In practice, it is usually not feasible to achieve
precise equality but commonly the range of anion capacity in the
mixed bed can be about 40%-60% with the remaining capacity as
cation capacity.
[0058] The "composite bed" concept as used herein relates to a
composite as a mixture of a cation exchange material and an anion
exchange material without reference to the proportions of each.
That is, in a composite bed the ion exchange capacity ratio could
range from about 1% to about 99% of either material, and the
balance comprising the opposite material type. Generally, three
types of composite beds are considered: [0059] 1. A "mixed bed"
where the ratio of anion to cation ion exchange capacity is
approximately 1:1 with a range of about 10% (that is, 40%-60% of
either cation or anion capacity). [0060] 2. A "doped" anion bed
where the anion capacity is at least about 60% and the remaining
ion exchange capacity is cation. [0061] 3. A "doped" cation bed
where the cation capacity is at least about 60% and the remaining
ion exchange capacity is anion.
[0062] Simply put, as the proportion of cation exchange material
P.sub.c in a "composite bed" is increased from about 1% to about
99% we encounter first the particular type of composite bed called
a "doped anion bed" for P.sub.c less than about 40%. A "mixed bed"
is produced for P.sub.c greater than about 40% and less than about
60%, and a "doped cation bed" for P.sub.C greater than about
60%.
[0063] The EDI apparatus shown in FIG. 1 is an example of an EDI
apparatus, which comprises five discreet membrane bound chambers in
electrical communication (although other embodiments can have more
than five chambers). The apparatus illustrated in FIG. 1 comprises
an anode chamber 101 separated from an ADC 103 by a first AM 102.
The anode chamber 101 includes therein an anode that is typically
in electrical contact with the first AM 102. The ADC 103 typically
includes therein a homogeneous volume of anion exchange material. A
composite bed depletion chamber (or simply CBDC) 105 may be placed
on the cathode-side of the ADC 103. The ADC 103 and the CBDC 105
may be separated by a second AM 104. The CBDC 105 may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The doped anion
exchange material, or doped cation exchange material versions may
be advantageous in that they can be used to alter the conductivity
through the EDI apparatus and improve the performance of the EDI
apparatus. A CDC 107 may be placed on the cathode-side of the CBDC
105. The CBDC 105 and the CDC 107 may be separated by a first CM
106. The CDC 107 typically includes therein a homogeneous volume of
cation exchange material. The CDC 107 may be separated from the
cathode chamber 109 by a second CM 108. The cathode chamber 109
includes therein a cathode that is typically in electrical contact
with the second CM 108. When additional (more than five) membrane
bound chambers are present, they may be typically present in pairs
of additional homogeneous anion and cation depletion chambers,
which may be added next to existing like chambers, which are
present between an electrode and the CBDC 105. An electrical
current runs through the EDI apparatus transverse to the membranes,
conventionally from left to right for the apparatus depicted in
FIG. 1 as the direction of flow of positive charges.
[0064] Each CDC may be bounded by two cation exchange membranes and
typically includes a volume of homogeneous cation exchange
material. The cation exchange material may comprise cation exchange
resins, cation exchange particles, cation exchange fibers, cation
exchange screens, cation exchange monoliths, and combinations
thereof. Typically, the cation exchange material may be a volume of
homogeneous cation exchange resin.
[0065] The CBDC may be bounded by a cation exchange membrane from a
CDC and an anion exchange membrane from an ADC, and the chamber may
contain a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The ion exchange
material may comprise ion exchange resins, ion exchange particles,
ion exchange fibers, ion exchange screens, ion exchange monoliths,
and combinations thereof.
[0066] Each ADC may be bounded by two anion exchange membranes and
typically includes a volume of homogeneous anion exchange material.
The anion exchange material may comprise anion exchange resins,
anion exchange particles, anion exchange fibers, anion exchange
screens, anion exchange monoliths, and combinations thereof.
Typically, the anion exchange material may be a volume of
homogeneous anion exchange resin.
[0067] The ion exchange membranes used in the CEDI apparatuses to
practice some embodiments of the present invention work by passive
transfer and not reactive chemistry. They may contain functional
sites, which allow for the exchange of ions. The transfer of ions
through the ion exchange membrane is based upon the charge of the
ion. The ion exchange membranes may readily admit small ions but
resist the passage of bulk liquid for example. Ion exchange
membranes may be anion exchange membranes (AM) or cation exchange
membranes (CM), wherein they are selective to anions or cations
respectively. An AM may transport anions through the membrane, but
the membrane prevents the bulk flow of liquid from one side of the
membrane to the other. A CM may transport cations through the
membrane, but the membrane prevents the bulk flow of liquid from
one side of the membrane to the other. A property common to both
types of membranes is that they must be conductive so that ions may
migrate through the ion exchange membrane towards their respective
electrodes.
[0068] An example of an anion exchange membrane is a microporous
copolymer of styrene and divinylbenzene that has been
chloromethylated and then the pendant --CH.sub.2Cl groups that were
introduced to the aromatic rings were then quaternized with a
tertiary amine R.sub.1R.sub.2R.sub.3N where R.sub.1, R.sub.2, and
R.sub.3 represent organic groups and may represent different
organic groups or may represent the same organic group. This
results in a membrane which may be a strong base anion exchanger.
In some cases, the anion exchange membrane may also contain a
binder polymer or an inert fabric. An example of an anion exchange
membrane that may be used in connection with some embodiments of
the present invention is the AMI-7001S membrane (a product of
Membranes International, Glen Rock, N.J.). Other anion exchange
membranes which provide a strong base anion exchanger may also be
used.
[0069] An example of a cation exchange membrane is a microporous
copolymer of styrene and divinylbenzene that has undergone
sulfonation, resulting in the monosubstitution of --SO.sub.3H
groups on the aromatic rings of the copolymer. This results in a
membrane which may be a strong acid cation exchanger. In some
cases, the cation exchange membrane may also contain a binder
polymer or an inert fabric. An example of a cation exchange
membrane that may be used in connection with some embodiments of
the present invention is the CMI-7000S membrane (a product of
Membranes International, Glen Rock, N.J.). Other cation exchange
membranes which provide a strong acid cation exchanger may also be
used.
[0070] The ion exchange materials used in the EDI apparatuses of
the kind used to practice some embodiments of the present invention
may contain functional sites, which allow for the exchange of ions.
The interaction between ions and the ion exchange materials is
based upon the charge of the ion. The ion exchange materials may
readily admit small ions and molecules but resist the intrusion of
species of even a few hundred atomic mass units. Ion exchange
materials may be anion exchange materials or cation exchange
materials, wherein they are selective to anions or cations
respectively.
[0071] An example of an anion exchange resin is a microporous
copolymer of styrene and divinylbenzene that has been
chloromethylated and then the pendant --CH.sub.2Cl groups that were
introduced to the aromatic rings were then quaternized with a
tertiary amine R.sub.1R.sub.2R.sub.3N where R.sub.1, R.sub.2, and
R.sub.3 represent organic groups and may represent different
organic groups or may represent the same organic group. This
results in a resin which may be a strong base anion exchanger.
There are several commercially available resins of this type. One
example of an anion exchange resin that may be used is the Dowex
1.times.4 (200 mesh) resin (a product of Dow Chemical Company,
Midland, Mich.), which contains 4% divinylbenzene and is in the
ionic form Cl.sup.-. Other anion exchange resins which provide a
strong base anion exchanger may also be used.
[0072] An example of a cation exchange resin is a microporous
copolymer of styrene and divinylbenzene that has undergone
sulfonation, resulting in the monosubstitution of --SO.sub.3H
groups on the aromatic rings of the copolymer. This results in a
resin which may be a strong acid cation exchanger. There are
several commercially available resins of this type. One example of
a cation exchange resin that may be used is the Dowex 50W.times.4
(200 mesh) resin (a product of Dow Chemical Company, Midland,
Mich.), which contains 4% divinylbenzene and is in the ionic form
H.sup.+. Other cation exchange resins which provide a strong acid
cation exchanger may also be used.
[0073] The CBDC may serve two functions, among others. First, when
an electric field is applied, water splitting occurs wherever anion
and cation exchange materials are in direct contact with one
another. Water splitting occurs where a cation and anion exchange
material contact one another, or where a cation exchange material
contacts an anion exchange membrane, or where an anion exchange
material contacts a cation exchange membrane. Water splitting
results in the production of hydroxide and hydronium, which serve
to maintain the anion exchange material in the hydroxide form and
the cation exchange material in the hydronium form, respectively.
As well as keeping the ion exchange materials of the CBDC fully
regenerated, the hydroxide and hydronium formed at the ion exchange
material/ion exchange membrane interfaces of the CBDC serve to
provide hydroxide for the at least one ADC(s) and hydronium for the
at least one CDC(s).
[0074] A second function of the CBDC may be to remove from the feed
water, the few remaining (if any) anions not removed by the ADC and
the few remaining (if any) cations not removed by the CDC. Ion
transport in a composite bed ion exchange material relies on both
water splitting as well as electrophoretic migration of the ion
through the material. Water splitting may displace contaminant ions
from the ion exchange material. These contaminant ions may be
driven through the composite ion exchange material bed of the CBDC
towards their respective electrode chambers. Thus, contaminant
cations may be driven through the CBDC, through a CM, through the
CDC(s), and through a CM, to the cathode chamber. Likewise,
contaminant anions may be driven through the CBDC, through an AM,
through the ADC(s), and through an AM, to the anode chamber.
[0075] Water splitting generates hydronium and hydroxide ions which
may be used to regenerate ion exchange materials. Under the force
of an applied electric field, water splitting can occur at the
junction of anion and cation exchange materials. These junctions
occur in the CBDC, since this chamber contains both anion and
cation exchange materials and membranes. Hydronium from the CBDC
may travel through the CM to the CDC, thus regenerating the cation
exchange materials found within. Likewise, hydroxide from the CBDC
may travel through the AM to the ADC, thus regenerating the anion
exchange materials found within.
[0076] The following discussion will describe the movement of ions
through the CBDC. For this discussion, it will be assumed that the
CBDC is filled with ion exchange particles. An example of such ion
exchange particles includes ion exchange resins. For a contaminant
ion to be removed from the CBDC, the contaminant ion must either
come in contact with the respective membrane or be retained by an
ion exchange material particle in contact with a like ion exchange
membrane (cation material-cation membrane or anion material-anion
membrane). An ion that is in an ion exchange material particle and
electrophoretically migrating through the ion exchange material can
only move to the next like particle (anion or cation exchange) if
the two particles are in contact with one another, or if the
contaminant ion leaves the ion exchange material particle as a
result of water splitting. Since the CBDC contains a mixture of
anion and cation exchange materials, it is statistically unlikely,
for the typical densities of materials used in practice, that there
will be a continuous path of like material particles of any
significant distance, thus, electrophoretic migration in the
central chamber is advantageously accompanied by displacement and
retention (caused by water splitting) for efficient ion removal.
This is in contrast to the mechanism of ion removal in the ADC and
CDC where no water splitting occurs (since these chambers contain
only one type of ion exchange material). In the ADC and CDC,
contaminant ions may be removed by electrophoretic migration
through the material bed to and through the ion exchange membrane
and ultimately to the electrode chamber.
[0077] For example, chloride retained by the anion exchange
material of the CBDC may be displaced by water splitting. The
hydroxide ions formed from water splitting may displace the
contaminant anions (for example Cl.sup.-) from the anion exchange
material and the chloride goes into solution where it is "paired"
with hydronium ions from the water splitting reaction. The
contaminant Cl.sup.- (as hydrochloric acid, HCl) may now move
through the composite material bed where it may be retained again
by anion exchange, where the displacement-retention mechanisms
continue to occur. Eventually, the contaminant Cl.sup.- may come in
contact with an anion exchange material particle that is in contact
with the anion exchange membrane, and the contaminant Cl.sup.- ion
may be passed through the AM into the ADC.
[0078] The analogous situation occurs for a cation contaminant. For
example, sodium retained by the cation exchange material of the
CBDC may be displaced by water splitting. The hydronium ions formed
from water splitting may displace the contaminant cations (for
example Na.sup.+) from the cation exchange material and the cation
goes into solution where it is "paired" with hydroxide ions from
the water splitting reaction. The contaminant Na.sup.+ (as sodium
hydroxide, NaOH) may now move through the composite material bed
where it may be retained again by cation exchange, where the
displacement-retention mechanisms continue to occur. Eventually,
the contaminant Na.sup.+ may come in contact with a cation exchange
material particle that is in contact with the cation exchange
membrane, and thus the contaminant Na.sup.+ ion may be passed
through the cation membrane into the CDC.
[0079] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 1 comprises first causing the
liquid to be deionized to flow through the CDC 107. The CDC 107 may
be capable of removing cations. The CDC 107 typically includes
therein cation exchange materials and may be effective at removing
the contaminant cations. The cations may be allowed to pass through
a second CM 108 and into the cathode chamber 109. The contaminant
cations may be removed from the system in the cathode chamber 109.
The cations cannot travel toward the anode because of the influence
of the applied electric field. Therefore, the cations may be
effectively contained in the cathode chamber 109 until they are
flushed from the system by the waste liquid stream that removes
ions from the cathode chamber 109. The anions are attracted toward
the anode under the influence of the applied electric field but
will not be allowed to pass through a first CM 106 into the
adjacent CBDC 105. Therefore, the anions will be retained in the
liquid. The liquid exiting the CDC 107 has a reduced level of
cations relative to the in-coming liquid stream.
[0080] Following passage through 107, the liquid is then flowed
through the ADC 103. The ADC 103 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 102 and into
the anode chamber 101. The contaminant anions may be removed from
the system in the anode chamber 101. The cations are not allowed to
pass through a second AM 104 that defines the cathode-side of the
ADC 103. The anions cannot travel toward the cathode because of the
influence of the applied electric field. Therefore, the anions are
effectively contained in the anode chamber 101 until they are
flushed from the system by the waste liquid stream that removes
ions from the anode chamber 101. Any remaining cations are largely
unaffected while passing through the ADC 103. The liquid exiting
the ADC 103 may be largely free of anionic contamination.
[0081] Following passage through 103, the liquid is then flowed
through the CBDC 105. The CBDC 105 may be capable of effectively
removing any remaining cations or anions from the liquid stream.
The anions are attracted to the anode under the influence of the
applied electric field and may be allowed to pass through a second
AM 104 and into the ADC 103. The contaminant anions may be removed
from the system in the anode chamber 101. One benefit of this
configuration is that this prevents fouling and scaling of the
anode chamber 101 since the anions cannot react with cations to
form insoluble scaling materials (i.e., CaCO.sub.3, Mg(OH).sub.2,
etc.). The anions cannot travel toward the cathode because of the
influence of the applied electric field. Therefore, the anions may
be effectively removed in the ADC 103 or contained in the anode
chamber 101 until they are flushed from the system by the waste
liquid stream that removes ions from the anode chamber 101. The
cations are attracted to the cathode under the influence of the
applied electric field and may be allowed to pass through a first
CM 106 and into the CDC 107. The contaminant cations may be removed
from the system in the cathode chamber 109. The cations cannot
travel toward the anode because of the influence of the applied
electric field. Therefore, the cations may be effectively removed
in the CDC 107 or contained in the cathode chamber 109 until they
are flushed from the system by the waste liquid stream that removes
ions from the cathode chamber 109.
[0082] Water splitting occurs in the CBDC 105 since it may include
therein a composite of anion and cation exchange materials. The
water splitting in the CBDC 105 serves to regenerate the second AM
104 that separates the CBDC 105 from the ADC 103 as well as the
first CM 106 that separates the CBDC 105 from the adjacent CDC 107.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and enter the adjacent CDC 107 where they
may be effective in regenerating the cation exchange material
contained therein. Additionally, hydroxide ions generated by the
water splitting are attracted to the anode and enter the adjacent
ADC 103 where they may be effective in regenerating the anion
exchange material contained therein.
Example 1
[0083] An EDI device as shown in FIG. 1 was constructed using
machined high density polyethylene hardware to retain the
electrodes, membranes and material. In this example, the device was
substantially cylindrical in shape with a substantially circular
cross-section. Other shapes and cross-sections are feasible, but
circular was convenient for this example. The internal flow
dimensions of the ADC 103 were 1.27 cm in diameter and 3.81 cm in
length. The internal flow dimensions of the CBDC 105 were 1.27 cm
in diameter and 1.27 cm in length. The internal flow dimensions of
the CDC 107 were 1.27 cm in diameter and 3.81 cm in length.
[0084] The anode chamber 101, for this example, contained platinum
gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). In
contact with the anode and separating the anode chamber from the
ADC was an anion exchange membrane 102 (AMI-7001S, a product of
Membranes International, Glen Rock, N.J.). The ADC was filled with
an anion exchange resin (DOWEX.TM. 1.times.4 (200 mesh), a product
of The Dow Chemical Company, Midland, Mich.). An anion membrane 104
separated the ADC from the CBDC 105. The CBDC contained a doped
anion material bed. The doped anion material bed consisted of a
composite of an anion exchange resin (DOWEX.TM. 1.times.4 (200
mesh), a product of The Dow Chemical Company, Midland, Mich.) and a
cation exchange resin (DOWEX.TM. 50W.times.4 (200 mesh), a product
of The Dow Chemical Company, Midland, Mich.) with an ion exchange
capacity ratio of 3:1 anion to cation. The cation and anion
exchange resins were in the hydronium and hydroxide forms,
respectively. Separating the CDC 107 from the CBDC was a cation
exchange membrane 106 (CMI-7000, a product of Membranes
International, Glen Rock, N.J.). The CDC was filled with a cation
exchange resin (DOWEX.TM. 50W.times.4 (200 mesh), a product of The
Dow Chemical Company, Midland, Mich.). The CDC was separated from
the cathode chamber 109 by a cation membrane 108 (CMI-7000, a
product of Membranes International, Glen Rock, N.J.). The cathode
compartment contained platinum gauze electrodes (Unique Wire
Weaving Inc, Hillside, N.J.). The cathode was in direct contact
with the cation membrane 108 separating the CDC and cathode
chamber. A pump (GP40, a product of Dionex, Sunnyvale, Calif.) was
used to deliver reverse osmosis (RO) quality water (specific
conductance 15.1 .mu.S/cm, S=Siemens) at a flow rate of 2.0 mL/min
to the EDI device shown in FIG. 1. A conductivity detector (CD20, a
product of Dionex, Sunnyvale, Calif.) with a flow cell was used for
the conductivity measurements. From the pump, the RO water flow was
directed to the CDC 107, then to the ADC 103, then to the CBDC 105
and then to the flow-through conductivity cell. A peristaltic pump
(MASTERFLEX LS, a product of the Cole-Parmer company, Vernon Hills,
IL) was used to deliver deionized water at a flow rate of 2.0
mL/min to the anode chamber and then to the cathode chamber and
then to waste.
[0085] Initially, the conductance of the water exiting the EDI
device was 8.3 .mu.S/cm. Using a laboratory power supply, (E3612A,
a product of Agilent, Santa Clara, Calif.) a constant current of 40
mA was applied and the initial voltage was 42V. Gas evolution was
observed immediately from the anode and cathode chambers. The
initial background conductivity of the product water increased to
85 .mu.S/cm and over a 1 hour period the conductivity decreased to
1.2 .mu.S/cm. The EDI device was allowed to operate continuously
for 7 days. The data in Table 1 shows results for the device of
FIG. 1.
TABLE-US-00001 TABLE 1 Conductance Measurements vs. Time
Conductivity Hours Voltage (.mu.S/cm) 0.0 0.0 8.3 1 37 1.2 2 33
0.91 10 40 0.10 24 32 0.088 48 26 0.065 72 24 0.061 96 25 0.059 120
25 0.058 144 27 0.057 168 29 0.060
[0086] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
1 comprises first causing the liquid to be deionized to flow
through the ADC 103. The ADC 103 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 102 and into
the anode chamber 101. The contaminant anions may be removed from
the system in the anode chamber 101. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions are effectively contained in the anode
chamber 101 until they are flushed from the system by the waste
liquid stream that removes ions from the anode chamber 101. Any
cations are largely unaffected while passing through the ADC 103.
The liquid exiting the ADC 103 may be largely free of anionic
contamination.
[0087] Following passage through 103, the liquid is then flowed
through the CDC 107. The CDC 107 may be capable of removing
cations. The CDC 107 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a second CM 108 and into
the cathode chamber 109. The contaminant cations may be removed
from the system in the cathode chamber 109. The cations cannot
travel toward the anode because of the influence of the applied
electric field. Therefore, the cations may be effectively contained
in the cathode chamber 109 until they are flushed from the system
by the waste liquid stream that removes ions from the cathode
chamber 109. The anions are attracted toward the anode under the
influence of the applied electric field but will not be allowed to
pass through a first CM 106 into the adjacent CBDC 105. Therefore,
the anions will be retained in the liquid. The liquid exiting the
CDC 107 has a reduced level of cations relative to the in-coming
liquid stream.
[0088] Following passage through 107, the liquid is then flowed
through the CBDC 105. The CBDC 105 may be capable of effectively
removing any remaining cations or anions from the liquid stream.
The anions are attracted to the anode under the influence of the
applied electric field and may be allowed to pass through a second
AM 104 and into the ADC 103. The contaminant anions may be removed
from the system in the anode chamber 101. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
103 or contained in the anode chamber 101 until they are flushed
from the system by the waste liquid stream that removes ions from
the anode chamber 101. The cations are attracted to the cathode
under the influence of the applied electric field and may be
allowed to pass through a first CM 106 and into the CDC 107. The
contaminant cations may be removed from the system in the cathode
chamber 109. One benefit of this configuration is that this
prevents fouling and scaling of the cathode chamber 109 since the
cations cannot react with anions to form insoluble scaling
materials (i.e., CaCO.sub.3, Mg(OH).sub.2, etc.). The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
removed in the CDC 107 or contained in the cathode chamber 109
until they are flushed from the system by the waste liquid stream
that removes ions from the cathode chamber 109.
[0089] Water splitting occurs in the CBDC 105 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 105 serves to regenerate the second AM 104 that
separates the CBDC 105 from the ADC 103 as well as the first CM 106
that separates the CBDC 105 from the adjacent CDC 107.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and enter the adjacent CDC 107 where they
may be effective in regenerating the cation exchange material
contained therein. Additionally, hydroxide ions generated by the
water splitting are attracted to the anode and enter the adjacent
ADC 103 where they may be effective in regenerating the anion
exchange material contained therein.
[0090] An alternative EDI apparatus is illustrated in FIGS. 2A and
2B. In this apparatus, composite bed depletion chambers may be
placed adjacent to the anode and cathode chambers and separated
from the electrode chambers by an AM and a CM, respectively. The
composite bed depletion chamber adjacent to the anode will be
defined as the anodic composite bed depletion chamber (ACBDC). The
composite bed depletion chamber adjacent to the cathode will be
defined as the cathodic composite bed depletion chamber (CCBDC). In
each case, these composite bed depletion chambers may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material.
[0091] The ACBDC and CCBDC depletion chambers may be capable of
removing both anions and cations and may be used as a final
"polishing" bed. In this configuration, the apparatus comprises two
composite bed polishing chambers and most contaminant ions are
received into the composite bed concentrate chamber (CBCC).
Typically in this configuration, the CBCC may include therein a
mixed ion exchange material, or a doped anion exchange material, or
a doped cation exchange material. Depending on the application, the
flow order through the depletion chambers may be varied. Water
splitting occurs in the ACBDC and CCBDC which may contribute to the
regeneration of these chambers as well as to the regeneration of
the anion and cation depletion chambers.
[0092] The apparatus illustrated in FIG. 2A and FIG. 2B comprises
an anode chamber 201 including an anode therein. An ACBDC 203 may
be placed on the cathode-side of the anode chamber. The anode
chamber and the ACBDC may be separated by a first AM 202. The ACBDC
may include therein a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. A CDC 205
may be placed on the cathode-side of the ACBDC. The ACBDC and the
CDC may be separated by a first CM 204. The CDC typically includes
therein a homogeneous volume of cation exchange material. A CBCC
207 may be placed on the cathode-side of the CDC. The CDC and the
CBCC may be separated by a second CM 206. The CBCC may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. An ADC 209 may be
placed on the cathode-side of the CBCC. The CBCC and the ADC may be
separated by a second AM 208. The ADC typically includes therein a
homogeneous volume of anion exchange material. A CCBDC 211 may be
placed on the cathode-side of the ADC. The ADC and the CCBDC may be
separated by a third AM 210. The CCBDC may include therein a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material. The CCBDC may be separated from a
cathode chamber 213 by a third CM 212. The cathode chamber includes
a cathode therein. The apparatus as illustrated in FIG. 2A and FIG.
2B may be operated in continuous mode or in intermittent mode.
[0093] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIGS. 2A and 2B, makes use of the flow
path depicted in FIG. 2A, and comprises first causing the liquid to
be deionized to flow through the ACBDC 203. The ACBDC 203 may be
capable of removing both anions and cations. The anions are
attracted to the adjacent anode chamber 201 under the influence of
the applied electric field and may be allowed to pass through a
first AM 202 and may be removed from the liquid. The cations are
attracted toward the cathode under the influence of the applied
electric field and may be allowed to pass through a first CM 204
into the adjacent CDC 205. The CDC 205 typically includes therein
cation exchange materials and may be effective at removing the
contaminant cations. The cations may be allowed to pass through a
second CM 206 and into the CBCC 207. The contaminant cations may be
removed from the system in the CBCC 207. The cations are not
allowed to pass through a second AM 208 that defines the
cathode-side of the CBCC 207. The cations cannot travel toward the
anode because of the influence of the applied electric field.
Therefore, the cations may be effectively contained in the CBCC 207
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 207. The liquid exiting the ACBDC
203 has a reduced level of both anions and cations relative to the
in-coming liquid stream.
[0094] Water splitting occurs in the ACBDC 203 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the ACBDC 203 serves to regenerate the first AM 202 that
separates the ACBDC 203 from the anode chamber 201 as well as the
first CM 204 that separates the ACBDC 203 from the adjacent CDC
205. Additionally, hydronium ions generated by the water splitting
are attracted to the cathode and enter the adjacent CDC 205 where
they may be effective in regenerating the cation exchange material
contained therein.
[0095] Following passage through 203, the liquid is then flowed
through the CDC 205. The CDC 205 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a second CM 206
and into the CBCC 207. The contaminant cations may be removed from
the system in the CBCC 207. The cations are not allowed to pass
through a second AM 208 that defines the cathode-side of the CBCC
207. The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations are
effectively contained in the CBCC 207 until they are flushed from
the system by the waste liquid stream that removes ions from the
CBCC 207. Anions are largely unaffected while passing through the
CDC 205. The liquid exiting the CDC 205 may be largely free of
cationic contamination.
[0096] Following passage through 205, the liquid is then flowed
through the ADC 209. The ADC 209 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a second AM 208 and into
the CBCC 207. The contaminant anions may be removed from the system
in the CBCC 207. The anions are not allowed to pass through a
second CM 206 that defines the anode-side of the CBCC 207 and into
the CDC 205. One benefit of this configuration is that this
prevents fouling and scaling of the cathode chamber 213 since the
anions cannot react with cations to form insoluble scaling
materials (i.e., CaCO.sub.3, Mg(OH).sub.2, etc.). The anions cannot
travel toward the cathode because of the influence of the applied
electric field. Therefore, the anions may be effectively removed in
the ADC 209 or contained in the CBCC 207 until they are flushed
from the system by the waste liquid stream that removes ions from
the CBCC 207. Cations are largely unaffected while passing through
the ADC 209. The liquid exiting the ADC 209 may be largely free of
anionic contamination.
[0097] Following passage through 209, the liquid is then flowed
through the CCBDC 211. The CCBDC 211 may be capable of removing
both anions and cations. The cations are attracted to the adjacent
cathode chamber 213 under the influence of the applied electric
field and may be allowed to pass through a third CM 212 and may be
removed from the liquid. The anions are attracted toward the anode
under the influence of the applied electric field and may be
allowed to pass through a third AM 210 into the adjacent ADC 209.
The ADC 209 typically includes therein anion exchange materials and
may be effective at removing the contaminant anions. The anions may
be allowed to pass through a second AM 208 and into the CBCC 207.
The contaminant anions may be removed from the system in the CBCC
207. The anions are not allowed to pass through a second CM 206
that defines the anode-side of the CBCC 207. The anions cannot
travel toward the cathode because of the influence of the applied
electric field. Therefore, the anions may be effectively removed in
the ADC 209 or contained in the CBCC 207 until they are flushed
from the system by the waste liquid stream that removes ions from
the CBCC 207. The liquid exiting the CCBDC 211 may have a reduced
level of both anions and cations relative to the in-coming liquid
stream.
[0098] Water splitting occurs in the CCBDC 211 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CCBDC 211 serves to regenerate the third CM 212 that
separates the CCBDC 211 from the cathode chamber 213 as well as the
third AM 210 that separates the CCBDC 211 from the adjacent ADC
209. Additionally, hydroxide ions generated by the water splitting
are attracted to the anode and enter the adjacent ADC 209 where
they may be effective in regenerating the anion exchange material
contained therein.
[0099] The apparatus and method of use illustrated in FIG. 2A
address the cathode fouling and ion exchange degradation problems
common in convention EDI apparatuses since the cathode chamber may
not receive the contaminant ions and water splitting in the
composite bed depletion chambers generates hydronium and hydroxide
ions for the regeneration of the anion membranes, cation membranes,
anion exchange materials, and the cation exchange materials.
[0100] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIGS.
2A and 2B comprises reversing the flow depicted in FIG. 2A and
first causing the liquid to be deionized to flow through the CCBDC
211. The CCBDC 211 may be capable of removing both anions and
cations. The cations are attracted to the adjacent cathode chamber
213 under the influence of the applied electric field and may be
allowed to pass through a third CM 211 and may be removed from the
liquid. The anions are attracted toward the anode under the
influence of the applied electric field and may be allowed to pass
through a third AM 210 into the adjacent ADC 209. The ADC 209
typically includes therein anion exchange materials and may be
effective at removing the contaminant anions. The anions may be
allowed to pass through a second AM 208 and into the CBCC 207. The
contaminant anions may be removed from the system in the CBCC 207.
The anions are not allowed to pass through a second CM 206 that
defines the anode-side of the CBCC 207. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
209 or contained in the CBCC 207 until they are flushed from the
system by the waste liquid stream that removes ions from the CBCC
207. The liquid exiting the CCBDC 211 may have a reduced level of
both anions and cations relative to the in-coming liquid
stream.
[0101] Water splitting occurs in the CCBDC 211 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CCBDC 211 serves to regenerate the third CM 212 that
separates the CCBDC 211 from the cathode chamber 213 as well as the
third AM 210 that separates the CCBDC 211 from the adjacent ADC
209. Additionally, hydroxide ions generated by the water splitting
are attracted to the anode and enter the adjacent ADC 209 where
they may be effective in regenerating the anion exchange material
contained therein.
[0102] Following passage through 211, the liquid is then flowed
through the ADC 209. The ADC 209 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a second AM 208 and into
the CBCC 207. The contaminant anions may be removed from the system
in the CBCC 207. The anions are not allowed to pass through a
second CM 206 that defines the anode-side of the CBCC 207 and into
the CDC 205. The anions cannot travel toward the cathode because of
the influence of the applied electric field. Therefore, the anions
may be effectively removed in the ADC 209 or contained in the CBCC
207 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 207. Cations are largely
unaffected while passing through the ADC 209. The liquid exiting
the ADC 209 may be largely free of anionic contamination.
[0103] Following passage through 209, the liquid is then flowed
through the CDC 205. The CDC 205 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a second CM 206
and into the CBCC 207. The contaminant cations may be removed from
the system in the CBCC 207. The cations are not allowed to pass
through a second AM 208 that defines the cathode-side of the CBCC
207. The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations are
effectively contained in the CBCC 207 until they are flushed from
the system by the waste liquid stream that removes ions from the
CBCC 207. Anions are largely unaffected while passing through the
CDC 205. The liquid exiting the CDC 205 may be largely free of
cationic contamination.
[0104] Following passage through 205, the liquid is then flowed
through the ACBDC 203. The ACBDC 203 may be capable of removing
both anions and cations. The anions are attracted to the adjacent
anode chamber 201 under the influence of the applied electric field
and may be allowed to pass through a first AM 202 and may be
removed from the liquid. The cations are attracted toward the
cathode under the influence of the applied electric field and may
be allowed to pass through a first CM 204 into the adjacent CDC
205. The CDC 205 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a second CM 206 and into
the CBCC 207. The contaminant cations may be removed from the
system in the CBCC 207. The cations are not allowed to pass through
a second AM 208 that defines the cathode-side of the CBCC 207. The
cations cannot travel toward the anode because of the influence of
the applied electric field. Therefore, the cations may be
effectively contained in the CBCC 207 until they are flushed from
the system by the waste liquid stream that removes ions from the
CBCC 207. The liquid exiting the ACBDC 203 has a reduced level of
both anions and cations relative to the in-coming liquid
stream.
[0105] Water splitting occurs in the ACBDC 203 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the ACBDC 203 serves to regenerate the first AM 202 that
separates the ACBDC 203 from the anode chamber 201 as well as the
first CM 204 that separates the ACBDC 203 from the adjacent CDC
205. Additionally, hydronium ions generated by the water splitting
are attracted to the cathode and enter the adjacent CDC 205 where
they may be effective in regenerating the cation exchange material
contained therein.
[0106] The apparatus and methods of use illustrated in FIG. 2A
address the anode fouling and ion exchange degradation problems
common in convention EDI apparatuses since the anode chamber may
not receive the contaminant ions and water splitting in the
composite bed depletion chambers generates hydronium and hydroxide
ions for the regeneration of the anion membranes, cation membranes,
anion exchange materials, and the cation exchange materials.
[0107] Another method for performing electrodeionization utilizing
the apparatus as illustrated in FIGS. 2A and 2B, makes use of the
flow path depicted in FIG. 2B, and comprises first causing the
liquid to be deionized to flow through the CDC 205. The CDC 205 may
be capable of effectively removing contaminant cations from the
liquid stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a second CM 206 and into the CBCC 207. The contaminant
cations may be removed from the system in the CBCC 207. The cations
are not allowed to pass through a second AM 208 that defines the
cathode-side of the CBCC 207. The cations cannot travel toward the
anode because of the influence of the applied electric field.
Therefore, the cations may be effectively contained in the CBCC 207
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 207. Anions are largely unaffected
while passing through the CDC 205. The liquid exiting the CDC 205
may be largely free of cationic contamination.
[0108] Following the passage through 205, the liquid is then flowed
through the ADC 209. The ADC 209 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a second AM 208 and into
the CBCC 207. The contaminant anions may be removed from the system
in the CBCC 207. The anions are not allowed to pass through a
second CM 206 that defines the anode-side of the CBCC 207 and into
the CDC 205. One benefit of this configuration is that the majority
of anions may be removed into the CBCC 207 thus preventing the
formation of oxidants such as ClO.sub.2 in the anode chamber (from
contaminant chloride) which may damage the ion exchange membranes.
The anions cannot travel toward the cathode because of the
influence of the applied electric field. Therefore, the anions may
be effectively removed in the ADC 209 or contained in the CBCC 207
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 207. Cations are largely unaffected
while passing through the ADC 209. The liquid exiting the ADC 209
may be largely free of anionic contamination.
[0109] Following the passage through 209, the liquid is then flowed
through the CCBDC 211. The CCBDC 211 may be capable of removing
both anions and cations. The cations are attracted to the adjacent
cathode chamber 213 under the influence of the applied electric
field and may be allowed to pass through a third CM 212 and may be
removed from the liquid. The anions are attracted toward the anode
under the influence of the applied electric field and may be
allowed to pass through a third AM 210 into the adjacent ADC 209.
The ADC 209 typically includes therein anion exchange materials and
may be effective at removing the contaminant anions. The anions may
be allowed to pass through a second AM 208 and into the CBCC 207.
The contaminant anions may be removed from the system in the CBCC
207. The anions are not allowed to pass through a second CM 206
that defines the anode-side of the CBCC 207. The anions cannot
travel toward the cathode because of the influence of the applied
electric field. Therefore, the anions may be effectively removed in
the ADC 209 or contained in the CBCC 207 until they are flushed
from the system by the waste liquid stream that removes ions from
the CBCC 207. The liquid exiting the CCBDC 211 may have a reduced
level of both anions and cations relative to the in-coming liquid
stream.
[0110] Water splitting occurs in the CCBDC 211 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CCBDC 211 serves to regenerate the third CM 212 that
separates the CCBDC 211 from the cathode chamber 213 as well as the
third AM 210 that separates the CCBDC 211 from the adjacent ADC
209. Additionally, hydroxide ions generated by the water splitting
are attracted to the anode and enter the adjacent ADC 209 where
they may be effective in regenerating the anion exchange material
contained therein.
[0111] Following the passage through 211, the liquid is then flowed
through the ACBDC 203. The ACBDC 203 may be capable of removing
both anions and cations.
[0112] The anions are attracted to the adjacent anode chamber 201
under the influence of the applied electric field and may be
allowed to pass through a first AM 202 and may be removed from the
liquid. The cations are attracted toward the cathode under the
influence of the applied electric field and may be allowed to pass
through a first CM 204 into the adjacent CDC 205. The CDC 205
typically includes therein cation exchange materials and may be
effective at removing the contaminant cations. The cations may be
allowed to pass through a second CM 206 and into the CBCC 207. The
contaminant cations may be removed from the system in the CBCC 207.
The cations are not allowed to pass through a second AM 208 that
defines the cathode-side of the CBCC 207. The cations cannot travel
toward the anode because of the influence of the applied electric
field. Therefore, the cations may be effectively contained in the
CBCC 207 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 207. The liquid exiting the
ACBDC 203 may have a reduced level of both anions and cations
relative to the in-coming liquid stream.
[0113] Water splitting occurs in the ACBDC 203 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the ACBDC 203 serves to regenerate the first AM 202 that
separates the ACBDC 203 from the anode chamber 201 as well as the
first CM 204 that separates the ACBDC 203 from the adjacent CDC
205. Additionally, hydronium ions generated by the water splitting
are attracted to the cathode and enter the adjacent CDC 205 where
they may be effective in regenerating the cation exchange material
contained therein.
[0114] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
2B comprises first causing the liquid to be deionized to flow
through the ADC 209. The ADC 209 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a second AM 208 and into
the CBCC 207. The contaminant anions may be removed from the system
in the CBCC 207. The anions are not allowed to pass through a
second CM 206 that defines the anode-side of the CBCC 207 and into
the CDC 205. One benefit of this configuration is that the majority
of anions may be removed into the CBCC 207 thus preventing the
formation of oxidants such as ClO.sub.2 in the anode chamber (from
contaminant chloride) which may damage the ion exchange membranes.
The anions cannot travel toward the cathode because of the
influence of the applied electric field. Therefore, the anions may
be effectively removed in the ADC 209 or contained in the CBCC 207
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 207. Cations are largely unaffected
while passing through the ADC 209. The liquid exiting the ADC 209
may be largely free of anionic contamination.
[0115] Following the passage through 209, the liquid is then flowed
through the CDC 205. The CDC 205 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a second CM 206
and into the CBCC 207. The contaminant cations may be removed from
the system in the CBCC 207. The cations are not allowed to pass
through a second AM 208 that defines the cathode-side of the CBCC
207. The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations may
be effectively contained in the CBCC 207 until they are flushed
from the system by the waste liquid stream that removes ions from
the CBCC 207. Anions are largely unaffected while passing through
the CDC 205. The liquid exiting the CDC 205 may be largely free of
cationic contamination.
[0116] Following the passage through 205, the liquid is then flowed
through the ACBDC 203. The ACBDC 203 may be capable of removing
both anions and cations. The anions are attracted to the adjacent
anode chamber 201 under the influence of the applied electric field
and may be allowed to pass through a first AM 202 and may be
removed from the liquid. The cations are attracted toward the
cathode under the influence of the applied electric field and may
be allowed to pass through a first CM 204 into the adjacent CDC
205. The CDC 205 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a second CM 206 and into
the CBCC 207. The contaminant cations may be removed from the
system in the CBCC 207. The cations are not allowed to pass through
a second AM 208 that defines the cathode-side of the CBCC 207. The
cations cannot travel toward the anode because of the influence of
the applied electric field. Therefore, the cations may be
effectively contained in the CBCC 207 until they are flushed from
the system by the waste liquid stream that removes ions from the
CBCC 207. The liquid exiting the ACBDC 203 may have a reduced level
of both anions and cations relative to the in-coming liquid
stream.
[0117] Water splitting occurs in the ACBDC 203 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the ACBDC 203 serves to regenerate the first AM 202 that
separates the ACBDC 203 from the anode chamber 201 as well as the
first CM 204 that separates the ACBDC 203 from the adjacent CDC
205. Additionally, hydronium ions generated by the water splitting
are attracted to the cathode and enter the adjacent CDC 205 where
they may be effective in regenerating the cation exchange material
contained therein.
[0118] Following the passage through 203, the liquid is then flowed
through the CCBDC 211. The CCBDC 211 may be capable of removing
both anions and cations. The cations are attracted to the adjacent
cathode chamber 213 under the influence of the applied electric
field and may be allowed to pass through a third CM 212 and may be
removed from the liquid. The anions are attracted toward the anode
under the influence of the applied electric field and may be
allowed to pass through a third AM 210 into the adjacent ADC 209.
The ADC 209 typically includes therein anion exchange materials and
may be effective at removing the contaminant anions. The anions may
be allowed to pass through a second AM 208 and into the CBCC 207.
The contaminant anions may be removed from the system in the CBCC
207. The anions are not allowed to pass through a second CM 206
that defines the anode-side of the CBCC 207. The anions cannot
travel toward the cathode because of the influence of the applied
electric field. Therefore, the anions may be effectively removed in
the ADC 209 or contained in the CBCC 207 until they are flushed
from the system by the waste liquid stream that removes ions from
the CBCC 207. The liquid exiting the CCBDC 211 may have a reduced
level of both anions and cations relative to the in-coming liquid
stream.
[0119] Water splitting occurs in the CCBDC 211 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CCBDC 211 serves to regenerate the third CM 212 that
separates the CCBDC 211 from the cathode chamber 213 as well as the
third AM 210 that separates the CCBDC 211 from the adjacent ADC
209. Additionally, hydroxide ions generated by the water splitting
are attracted to the anode and enter the adjacent ADC 209 where
they may be effective in regenerating the anion exchange material
contained therein.
Example 2
[0120] An EDI device as shown in FIG. 2B was constructed using
machined high density polyethylene hardware to retain the
electrodes, membranes and resin. The internal flow dimensions of
the ACBDC 203 were 1.27 cm in diameter and 1.27 cm in length. The
ADC 205 was 1.27 cm in diameter and 3.81 cm in length. The internal
flow dimensions of the CBCC 207 were 1.27 cm in diameter and 1.27
cm in length. The internal flow dimensions of the CDC 209 were 1.27
cm in diameter and 3.81 cm in length. The internal flow dimensions
of the CCBDC 211 were 1.27 cm in diameter and 1.27 cm in
length.
[0121] The anode chamber 201, for this example, contained platinum
gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). In
contact with the anode and separating the anode chamber 201 from
the ACBDC 203 was an anion exchange membrane 202 (AMI-7001S, a
product of Membranes International, Glen Rock, N.J.). The ACBDC
contained a homogenous mixture of cation exchange resin (DOWEX.TM.
50W.times.4 (200 mesh), a product of The Dow Chemical Company,
Midland, Mich.) and anion exchange resin (DOWEX.TM. 1.times.4 (200
mesh), a product of The Dow Chemical Company, Midland, Mich.) in
the hydronium and hydroxide forms, respectively. The ion exchange
capacity ratio of anion to cation was 1:1 (a mixed bed). Separating
the ACBDC 203 from the CDC 205 was a cation exchange membrane 204
(CMI-7000, a product of Membranes International, Glen Rock, N.J.).
The CDC was filled with a cation exchange resin (DOWEX.TM.
50W.times.4 (200 mesh), a product of The Dow Chemical Company,
Midland, Mich.). Separating the CDC 205 from the CBCC 207 was a
cation exchange membrane 206 (CMI-7000, a product of Membranes
International, Glen Rock, N.J.). The CBCC chamber contained a
homogenous mixture of cation exchange resin (DOWEX.TM. 50W.times.4
(200 mesh), a product of The Dow Chemical Company, Midland, Mich.)
and anion exchange resin (DOWEX.TM. 1.times.4 (200 mesh), a product
of The Dow Chemical Company, Midland, Mich.) in the hydronium and
hydroxide forms, respectively. The ion exchange capacity ratio of
anion to cation was 1:1 (a mixed bed). The CBCC 207 was separated
from the ADC 209 by an anion membrane 208 (AMI-7001, a product of
Membranes International, Glen Rock, N.J.). The ADC was filled with
an anion exchange resin (DOWEX.TM. 1.times.4 (200 mesh), a product
of The Dow Chemical Company, Midland, Mich.). The ADC 209 was
separated from the CCBDC 211 by an anion exchange membrane 210
(AMI-7001, a product of Membranes International, Glen Rock, N.J.).
The CCBDC was filled with a homogenous mixture cation exchange
resin (DOWEX.TM. 50W.times.4 (200 mesh), a product of The Dow
Chemical Company, Midland, Mich.) and anion exchange resin
(DOWEX.TM. 1.times.4 (200 mesh), a product of The Dow Chemical
Company, Midland, Mich.) in the hydronium and hydroxide forms,
respectively. The ion exchange capacity ratio of anion to cation
was 1:1 (a mixed bed). Separating the CCBDC 211 from the cathode
chamber 213 was a cation exchange membrane 212 (CMI-7000, a product
of Membranes International, Glen Rock, N.J.). A pump (GP40, a
product of Dionex, Sunnyvale, Calif.) was used to deliver RO
quality water (specific conductance 14.3 .mu.s/cm) at a flow rate
of 3.0 mL/min to the EDI device shown in FIG. 2B. A conductivity
detector (CD20, a product of Dionex, Sunnyvale, Calif.) with a flow
cell was used for the conductivity measurements. From the pump, the
RO water flow was directed to the CDC 205, then to the ADC 209,
then the CCBDC 211, next to the ACBDC 203 and then to the flow
through the conductivity cell. From the conductivity cell, the flow
was directed to the anode chamber 201 and then the cathode chamber
213 and finally to waste.
[0122] Initially, the conductance of the water exiting the EDI
device was 4.8 .mu.S/cm. Using a laboratory power supply (E3612A, a
product of Agilent, Santa Clara, Calif.) a constant current of 20
mA was applied and the initial voltage was 55V. Gas evolution was
observed immediately from the anode and cathode chambers. The
initial background conductivity of the product water increased to
about 60 .mu.S/cm and over a 1 hour period the conductivity
decreased to 0.72 .mu.S/cm. The EDI device was allowed to operate
continuously for 9 days. The data in Table 2 shows results for the
device of FIG. 28.
TABLE-US-00002 TABLE 2 Conductance Measurements vs. Time
Conductivity Hours voltage (.mu.S/cm) 0.0 0.0 4.8 1 51 0.72 2 49
0.21 10 40 0.081 24 32 0.069 48 26 0.071 72 24 0.061 96 25 0.058
120 25 0.058 144 27 0.056 168 29 0.057 192 29 0.057 216 28
0.058
[0123] The apparatus and methods of use illustrated in FIG. 2B
address the electrode fouling and ion exchange degradation problems
since the electrode chambers may not receive the contaminant ions
and water splitting in the composite bed depletion chambers
generates hydronium and hydroxide ions for the regeneration of the
anion membranes, cation membranes, anion exchange materials, and
the cation exchange materials.
[0124] One benefit of the apparatuses and methods illustrated in
FIG. 2A and FIG. 2B is that it may be possible to use "harder"
(i.e., higher levels of mineral compounds) liquids (i.e., water) in
the input stream without damaging the apparatus or degrading the
efficiency of the apparatus. Input liquids which may contain
significant concentrations of calcium, magnesium, and carbonate are
problematic for conventional EDI apparatuses if these cations are
removed directly to the cathode chamber. In the configurations as
illustrated in FIG. 2A and FIG. 2B, the cations may be removed to
the CBCC at the center of the apparatus and thereby reduces the
scaling within the cathode chamber.
[0125] FIG. 2C illustrates an EDI apparatus that may be equivalent
to FIG. 2A with the polarity of the electric field reversed (i.e.
the anode and cathodes are switched). That is, the path from anode
to cathode in FIG. 2C traverses the same EDI components in the same
order as the path from cathode to anode in FIG. 2A. The apparatus
illustrated in FIG. 2C comprises an anode chamber 220 including an
anode therein. An ACBCC 222 may be placed on the cathode-side of
the anode chamber. The anode chamber and the ACBCC may be separated
by a first CM 221. The ACBCC may include therein a mixed ion
exchange material, or a doped anion exchange material, or a doped
cation exchange material. An ADC 224 may be placed on the
cathode-side of the ACBCC. The ACBCC and the ADC may be separated
by a first AM 223. The ADC typically includes therein a homogeneous
volume of anion exchange material. A CBDC 226 may be placed on the
cathode-side of the ADC. The ADC and the CBDC may be separated by a
second AM 225. The CBDC may include therein a mixed ion exchange
material, or a doped anion exchange material, or a doped cation
exchange material. A CDC 228 may be placed on the cathode-side of
the CBDC. The CBDC and the CDC may be separated by a second CM 227.
The CDC typically includes therein a homogeneous volume of cation
exchange material. A CCBCC 230 may be placed on the cathode-side of
the CDC. The CDC and the CCBCC may be separated by a third CM 229.
The CCBCC may include therein a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange material.
The CCBCC may be separated from a cathode chamber 232 by a third AM
231. The cathode chamber includes a cathode therein. The apparatus
as illustrated in FIG. 2C may be operated in continuous mode or in
intermittent mode.
[0126] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 2C comprises first causing the
liquid to be deionized to flow through the CDC 228. The CDC 228 may
be capable of removing cations. The CDC 228 typically includes
therein cation exchange materials and may be effective at removing
the contaminant cations. The cations may be allowed to pass through
a third CM 229 and into the CCBCC 230. The contaminant cations may
be removed from the system in the CCBCC 230. The cations cannot
travel toward the anode because of the influence of the applied
electric field. Therefore, the cations may be effectively contained
in the CCBCC 230 until they are flushed from the system by the
waste liquid stream that removes ions from the CCBCC 230. The
anions are attracted toward the anode under the influence of the
applied electric field but will not be allowed to pass through a
second CM 227 into the adjacent CBDC 226. Therefore, the anions
will be retained in the liquid. The liquid exiting the CDC 228 has
a reduced level of both cations relative to the in-coming liquid
stream.
[0127] Following the passage through 228, the liquid is then flowed
through the ADC 224. The ADC 224 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 223 and into
the ACBCC 222. The contaminant anions may be removed from the
system in the ACBCC 222. The anions are not allowed to pass through
a first CM 221 that defines the anode-side of the ACBCC 222. The
anions cannot travel toward the cathode because of the influence of
the applied electric field. Therefore, the anions are effectively
contained in the ACBCC 222 until they are flushed from the system
by the waste liquid stream that removes ions from the ACBCC 222.
Any remaining cations are largely unaffected while passing through
the ADC 224. The liquid exiting the ADC 224 may be largely free of
anionic contamination.
[0128] Following the passage through 224, the liquid is then flowed
through the CBDC 226. The CBDC 226 may be capable of effectively
removing any remaining cations or anions from the liquid stream.
The anions are attracted to the anode under the influence of the
applied electric field and may be allowed to pass through a second
AM 225 and into the ADC 224. The contaminant anions may be removed
from the system in the ACBCC 222. The anions are not allowed to
pass through a first CM 221 that defines the anode-side of the
ACBCC 222 and into the anode chamber 220. One benefit of this
configuration is that this prevents fouling and scaling of the
anode chamber 220 since the anions cannot pass through CM 221 and
into the anode chamber 220. The anions cannot travel toward the
cathode because of the influence of the applied electric field.
Therefore, the anions may be effectively removed in the ADC 224 or
contained in the ACBCC 222 until they are flushed from the system
by the waste liquid stream that removes ions from the ACBCC 222.
The cations are attracted to the cathode under the influence of the
applied electric field and may be allowed to pass through a second
CM 227 and into the CDC 228. The contaminant cations may be removed
from the system in the CCBCC 230. The cations are not allowed to
pass through a third AM 231 that defines the cathode-side of the
CCBCC 230 and into the cathode chamber 232. One benefit of this
configuration is that this prevents fouling and scaling of the
cathode chamber 232 since the cations cannot react with anions to
form insoluble scaling materials (i.e., CaCO.sub.3, Mg(OH).sub.2,
etc.). The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations may
be effectively removed in the CDC 228 or contained in the CCBCC 230
until they are flushed from the system by the waste liquid stream
that removes ions from the CCBCC 230. This design also reduces
degradation in the anode chamber since anions do not enter anode
chamber 220.
[0129] Water splitting occurs in the CBDC 226 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 226 serves to regenerate the second AM 225 that
separates the CBDC 226 from the ADC 224 as well as the second CM
227 that separates the CBDC 226 from the adjacent CDC 228.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and enter the adjacent CDC 228 where they
may be effective in regenerating the cation exchange material
contained therein and CM 229. Additionally, hydroxide ions
generated by the water splitting are attracted to the anode and
enter the adjacent ADC 224 where they may be effective in
regenerating the anion exchange material contained therein and AM
223.
[0130] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
2C comprises first causing the liquid to be deionized to flow
through the ADC. The ADC 224 may be capable of effectively removing
contaminant anions from the liquid stream. The anions are attracted
to the anode under the influence of the applied electric field and
may be allowed to pass through a first AM 223 and into the ACBCC
222. The contaminant anions may be removed from the system in the
ACBCC 222. The anions are not allowed to pass through a first CM
221 that defines the anode-side of the ACBCC 222. The anions cannot
travel toward the cathode because of the influence of the applied
electric field. Therefore, the anions are effectively contained in
the ACBCC 222 until they are flushed from the system by the waste
liquid stream that removes ions from the ACBCC 222. Any remaining
cations are largely unaffected while passing through the ADC 224.
The liquid exiting the ADC 224 may be largely free of anionic
contamination.
[0131] Following the passage through 224, the liquid is then flowed
through the CDC 228. The CDC 228 may be capable of removing
cations. The CDC 228 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a third CM 229 and into
the CCBCC 230. The contaminant cations may be removed from the
system in the CCBCC 230. The cations cannot travel toward the anode
because of the influence of the applied electric field. Therefore,
the cations may be effectively contained in the CCBCC 230 until
they are flushed from the system by the waste liquid stream that
removes ions from the CCBCC 230. The anions are attracted toward
the anode under the influence of the applied electric field but
will not be allowed to pass through a second CM 227 into the
adjacent CBDC 226. Therefore, the anions will be retained in the
liquid. The liquid exiting the CDC 228 has a reduced level of both
cations and anions relative to the in-coming liquid stream.
[0132] Following the passage through 228, the liquid is then flowed
through the CBDC 226. The CBDC 226 may be capable of effectively
removing any remaining cations or anions from the liquid stream.
The anions are attracted to the anode under the influence of the
applied electric field and may be allowed to pass through a second
AM 225 and into the ADC 224 and continue through AM 223 into the
ACBCC 222. The contaminant anions may be removed from the system in
the ACBCC 222. The anions are not allowed to pass through a first
CM 221 that defines the anode-side of the ACBCC 222 and into the
anode chamber 220. One benefit of this configuration is that this
prevents fouling and scaling of the anode chamber 220 since the
anions cannot pass through CM 221 and enter the anode chamber 220.
The anions cannot travel toward the cathode because of the
influence of the applied electric field. Therefore, the anions may
be effectively removed in the ADC 224 or contained in the ACBCC 222
until they are flushed from the system by the waste liquid stream
that removes ions from the ACBCC 222. The cations are attracted to
the cathode under the influence of the applied electric field and
may be allowed to pass through a second CM 227 and into the CDC 228
and continue through CM 229 into the CCBCC 230. The contaminant
cations may be removed from the system in the CCBCC 230. The
cations are not allowed to pass through a third AM 231 that defines
the cathode-side of the CCBCC 230 and into the cathode chamber 232.
One benefit of this configuration is that this prevents fouling and
scaling of the cathode chamber 232 since the cations cannot react
with anions to form insoluble scaling materials (i.e., CaCO.sub.3,
Mg(OH).sub.2, etc.). The cations cannot travel toward the anode
because of the influence of the applied electric field. Therefore,
the cations may be effectively removed in the CDC 228 or contained
in the CCBCC 230 until they are flushed from the system by the
waste liquid stream that removes ions from the CCBCC 230.
[0133] Water splitting occurs in the CBDC 226 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 226 serves to regenerate the second AM 225 that
separates the CBDC 226 from the ADC 224 as well as the second CM
227 that separates the CBDC 226 from the adjacent CDC 228.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and enter the adjacent CDC 228 where they
may be effective in regenerating the cation exchange material
contained therein and CM 229. Additionally, hydroxide ions
generated by the water splitting are attracted to the anode and
enter the adjacent ADC 224 where they may be effective in,
regenerating the anion exchange material contained therein and AM
223.
[0134] FIG. 2D illustrates an EDI apparatus that is similar to FIG.
2C except that the ACBCC chamber has been replaced with an ACC and
the CCBCC has been replaced with a CCC. The apparatus illustrated
in FIG. 2D comprises an anode chamber 240 including an anode
therein. An ACC 242 may be placed on the cathode-side of the anode
chamber. The anode chamber and the ACC may be separated by a first
CM 241. The ACC typically includes therein a homogeneous volume of
anion exchange material, or a homogeneous volume of cation exchange
material, or a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. An ADC 244
may be placed on the cathode-side of the ACC. The ACC and the ADC
may be separated by a first AM 243. The ADC may include therein a
homogeneous volume of anion exchange material. A CBDC 246 may be
placed on the cathode-side of the ADC. The ADC and the CBDC may be
separated by a second AM 245. The CBDC may include therein a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material. A CDC 248 may be placed on the
cathode-side of the CBDC. The CBDC and the CDC may be separated by
a second CM 247. The CDC typically includes therein a homogeneous
volume of cation exchange material. A CCC 250 may be placed on the
cathode-side of the CDC. The CDC and the CCC may be separated by a
third CM 249. The CCC may include therein a homogeneous volume of
anion exchange material, or a homogeneous volume of cation exchange
material, or a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. The CCC may
be separated from a cathode chamber 252 by a third AM 251. The
cathode chamber includes a cathode therein. The apparatus as
illustrated in FIG. 2D may be operated in continuous mode or in
intermittent mode.
[0135] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 2D comprises first causing the
liquid to be deionized to flow through the CDC 248. The CDC 248 may
be capable of removing cations. The CDC 248 typically includes
therein cation exchange materials and may be effective at removing
the contaminant cations. The cations may be allowed to pass through
a third CM 249 and into the CCC 250. The contaminant cations may be
removed from the system in the CCC 250. The cations cannot travel
toward the anode because of the influence of the applied electric
field. Therefore, the cations may be effectively contained in the
CCC 250 until they are flushed from the system by the waste liquid
stream that removes ions from the CCC 250. The anions are attracted
toward the anode under the influence of the applied electric field
but will not be allowed to pass through a second CM 247 into the
adjacent CBDC 246. Therefore, the anions will be retained in the
liquid. The liquid exiting the CDC 248 has a reduced level of
cations relative to the in-coming liquid stream.
[0136] Following the passage through 248, the liquid is then flowed
through the ADC 244. The ADC 244 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 243 and into
the ACC 242. The contaminant anions may be removed from the system
in the ACC 242. The anions are not allowed to pass through a first
CM 241 that defines the anode-side of the ACC 242. The anions
cannot travel toward the cathode because of the influence of the
applied electric field. Therefore, the anions are effectively
contained in the ACC 242 until they are flushed from the system by
the waste liquid stream that removes ions from the ACC 242. Any
remaining cations are largely unaffected while passing through the
ADC 244. The liquid exiting the ADC 244 may be largely free of
anionic contamination.
[0137] Following the passage through 244, the liquid is then flowed
through the CBDC 246. The CBDC 246 may be capable of effectively
removing any remaining cations or anions from the liquid stream.
The anions are attracted to the anode under the influence of the
applied electric field and may be allowed to pass through a second
AM 245 and into the ADC 244. The contaminant anions may be removed
from the system in the ACC 242. The anions are not allowed to pass
through a first CM 241 that defines the anode-side of the ACC 242
and into the anode chamber 240. One benefit of this configuration
is that this prevents fouling and scaling of the anode chamber 240
since the anions cannot react with cations to form insoluble
scaling materials (i.e., CaCO.sub.3, Mg(OH).sub.2, etc.). The
anions cannot travel toward the cathode because of the influence of
the applied electric field. Therefore, the anions may be
effectively removed in the ADC 244 or contained in the ACC 242
until they are flushed from the system by the waste liquid stream
that removes ions from the ACC 242. The cations are attracted to
the cathode under the influence of the applied electric field and
may be allowed to pass through a second CM 247 and into the CDC
248. The contaminant cations may be removed from the system in the
CCC 250. The cations are not allowed to pass through a third AM 251
that defines the cathode-side of the CCC 250 and into the cathode
chamber 252. One benefit of this configuration is that this
prevents fouling and scaling of the cathode chamber 252 since the
cations cannot react with anions to form insoluble scaling
materials (i.e., CaCO.sub.3, Mg(OH).sub.2, etc.). The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
removed in the CDC 248 or contained in the CCC 250 until they are
flushed from the system by the waste liquid stream that removes
ions from the CCC 250.
[0138] Water splitting occurs in the CBDC 246 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 246 serves to regenerate the second AM 245 that
separates the CBDC 246 from the ADC 244 as well as the second CM
247 that separates the CBDC 246 from the adjacent CDC 248.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and enter the adjacent CDC 248 where they
may be effective in regenerating the cation exchange material
contained therein. Additionally, hydroxide ions generated by the
water splitting are attracted to the anode and enter the adjacent
ADC 244 where they may be effective in regenerating the anion
exchange material contained therein.
[0139] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
2D comprises first causing the liquid to be deionized to flow
through the ADC. The ADC 244 may be capable of effectively removing
contaminant anions from the liquid stream. The anions are attracted
to the anode under the influence of the applied electric field and
may be allowed to pass through a first AM 243 and into the ACC 242.
The contaminant anions may be removed from the system in the ACC
242. The anions are not allowed to pass through a first CM 241 that
defines the anode-side of the ACC 242. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions are effectively contained in the ACC
242 until they are flushed from the system by the waste liquid
stream that removes ions from the ACC 242. Any remaining cations
are largely unaffected while passing through the ADC 244. The
liquid exiting the ADC 244 may be largely free of anionic
contamination.
[0140] Following the passage through 244, the liquid is then flowed
through the CDC 248. The CDC 248 may be capable of removing
cations. The CDC 248 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a third CM 249 and into
the CCC 250. The contaminant cations may be removed from the system
in the CCC 250. The cations cannot travel toward the anode because
of the influence of the applied electric field. Therefore, the
cations may be effectively contained in the CCC 250 until they are
flushed from the system by the waste liquid stream that removes
ions from the CCC 250. The anions are attracted toward the anode
under the influence of the applied electric field but will not be
allowed to pass through a second CM 247 into the adjacent CBDC 246.
Therefore, the anions will be retained in the liquid. The liquid
exiting the CDC 248 has a reduced level of both cations relative to
the in-coming liquid stream.
[0141] Following the passage through 248, the liquid is then flowed
through the CBDC 246. The CBDC 246 may be capable of effectively
removing any remaining cations or anions from the liquid stream.
The anions are attracted to the anode under the influence of the
applied electric field and may be allowed to pass through a second
AM 245 and into the ADC 244. The contaminant anions may be removed
from the system in the ACC 242. The anions are not allowed to pass
through a first CM 241 that defines the anode-side of the ACC 242
and into the anode chamber 240. One benefit of this configuration
is that this prevents fouling and scaling of the anode chamber 240
since the anions cannot react with cations to form insoluble
scaling materials (i.e., CaCO.sub.3, Mg(OH).sub.2, etc.). The
anions cannot travel toward the cathode because of the influence of
the applied electric field. Therefore, the anions may be
effectively removed in the ADC 244 or contained in the ACC 242
until they are flushed from the system by the waste liquid stream
that removes ions from the ACC 242. The cations are attracted to
the cathode under the influence of the applied electric field and
may be allowed to pass through a second CM 247 and into the CDC
248. The contaminant cations may be removed from the system in the
CCC 250. The cations are not allowed to pass through a third AM 251
that defines the cathode-side of the CCC 250 and into the cathode
chamber 252. One benefit of this configuration is that this
prevents fouling and scaling of the cathode chamber 252 since the
cations cannot react with anions to form insoluble scaling
materials (i.e., CaCO.sub.3, Mg(OH).sub.2, etc.). The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
removed in the CDC 248 or contained in the CCC 250 until they are
flushed from the system by the waste liquid stream that removes
ions from the CCC 250.
[0142] Water splitting occurs in the CBDC 246 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 246 serves to regenerate the second AM 245 that
separates the CBDC 246 from the ADC 244 as well as the second CM
247 that separates the CBDC 246 from the adjacent CDC 248.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and enter the adjacent CDC 248 where they
may be effective in regenerating the cation exchange material
contained therein. Additionally, hydroxide ions generated by the
water splitting are attracted to the anode and enter the adjacent
ADC 244 where they may be effective in regenerating the anion
exchange material contained therein.
[0143] The apparatus and method of use illustrated in FIGS. 2A-D
address the cathode fouling and ion exchange degradation problems
common in conventional EDI apparatuses since the cathode and anode
chambers may not receive the contaminant ions and water splitting
in the composite or doped bed depletion chambers generates
hydronium and hydroxide ions for the regeneration of the anion
membranes, cation membranes, anion exchange materials, and the
cation exchange materials.
[0144] By removing the CCBDC and the CM adjacent to the cathode
from the apparatus of FIG. 2A and FIG. 2B, an apparatus, with the
advantages of minimal electrode fouling or electrode degradation is
illustrated schematically in FIG. 3A. An ACBDC 303 may be placed on
the cathode-side of the anode chamber 301. The anode chamber 301
and the ACBDC 303 may be separated by a first AM 302. The ACBDC may
include therein a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. A CDC 305
may be placed on the cathode-side of the ACBDC 303. The ACBDC 303
and the CDC 305 may be separated by a first CM 304. The CDC
typically includes therein a homogeneous volume of cation exchange
material. A CBCC 307 may be placed on the cathode-side of the CDC
305. The CDC 305 and the CBCC 307 may be separated by a second CM
306. The CBCC may include therein a mixed ion exchange material, or
a doped anion exchange material, or a doped cation exchange
material. An ADC 309 may be placed on the cathode-side of the CBCC
307. The CBCC 307 and the ADC 309 may be separated by a second AM
308. The ADC typically includes therein a homogeneous volume of
anion exchange material. The ADC 309 may be separated from a
cathode chamber 311 by a third AM 310. The cathode chamber includes
a cathode therein.
[0145] In FIG. 3A, the majority of the contaminant ions may be
drawn into the CBCC 307. The ACBDC 303 may serve as the final ion
depletion chamber. As the product liquid passes through the ACBDC
303, residual contaminant anions may be removed into the anode
chamber 301. Since the majority of contaminant anions may be
removed by the ADC 309, the trace amounts of residual anions
removed by the ACBDC 303 and into the anode chamber 301 will not
cause significant electrode degradation. The apparatus as
illustrated in FIG. 3A may be operated in continuous mode or in
intermittent mode.
[0146] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 3A comprises first causing the
liquid to be deionized to flow through the CDC 305. The CDC may be
capable of effectively removing contaminant cations from the liquid
stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a second cation exchange membrane 306 and into the CBCC
307. The contaminant cations may be removed from the system in the
CBCC 307. The cations are not allowed to pass through a second AM
308 that defines the cathode-side of the CBCC 307. The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
contained in the CBCC 307 until they are flushed from the system by
the waste liquid stream that removes ions from the CBCC 307. The
liquid exiting the CDC 305 may be largely free of cationic
contamination.
[0147] Following the passage through 305, the liquid is then flowed
through the ADC 309. The ADC 309 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a second anion exchange
membrane 308 and into the CBCC 307. The contaminant anions may be
removed from the system in the CBCC 307. The anions are not allowed
to pass through a second CM 306 that defines the anode-side of the
CBCC 307 and into the CDC 305. One benefit of this configuration is
that this prevents degradation of the anode chamber 301 since
anions cannot enter the anode chamber. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
309 or contained in the CBCC 307 until they are flushed from the
system by the waste liquid stream that removes ions from the CBCC
307. The liquid exiting the ADC 309 may be largely free of anionic
contamination.
[0148] Following the passage through 309, the liquid is then flowed
through the ACBDC 303. The ACBDC 303 may be capable of removing
both anions and cations. The remaining anions are attracted to the
adjacent anode chamber 301 under the influence of the applied
electric field and may be allowed to pass through a first AM 302
and may be removed from the liquid. The remaining cations are
attracted toward the cathode under the influence of the applied
electric field and may be allowed to pass through a first CM 304
into the adjacent CDC 305. The CDC 305 typically includes therein
cation exchange materials and may be effective at removing the
contaminant cations. The cations may be allowed to pass through a
second cation exchange membrane 306 and into the CBCC 307. The
contaminant cations may be removed from the system in the CBCC 307.
The cations are not allowed to pass through a second AM 308 that
defines the cathode-side of the CBCC 307. The cations cannot travel
toward the anode because of the influence of the applied electric
field. Therefore, the cations may be effectively contained in the
CBCC 307 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 307. The liquid exiting the
ACBDC 303 may have a reduced level of both anions and cations
relative to the in-coming liquid stream.
[0149] Water splitting occurs in the ACBDC 303 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the ACBDC 303 may serve to regenerate the first AM 302 that
separates the ACBDC 303 from the anode chamber 301 as well as the
first CM 304 that separates the ACBDC 303 from the adjacent CDC
305. Additionally, hydronium ions generated by the water splitting
are attracted to the cathode and may enter the adjacent CDC 305
where they may be effective in regenerating the cation exchange
material contained therein.
[0150] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
3A comprises first causing the liquid to be deionized to flow
through the ADC 309. The ADC 309 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a second AM 308 and into
the CBCC 307. The contaminant anions may be removed from the system
in the CBCC 307. The anions are not allowed to pass through a
second CM 306 that defines the anode-side of the CBCC 307 and into
the CDC 305. The anions cannot travel toward the cathode because of
the influence of the applied electric field. Therefore, the anions
may be effectively removed in the ADC 309 or contained in the CBCC
307 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 307. The liquid exiting the
ADC 309 may be largely free of anionic contamination.
[0151] Following the passage through 309, the liquid is then flowed
through the CDC 305. The CDC 305 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a second CM 306
and into the CBCC 307. The contaminant cations may be removed from
the system in the CBCC 307. The cations are not allowed to pass
through a second AM 308 that defines the cathode-side of the CBCC
307. The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations may
be effectively contained in the CBCC 307 until they are flushed
from the system by the waste liquid stream that removes ions from
the CBCC 307. The liquid exiting the CDC 305 may be largely free of
cationic contamination.
[0152] Following the passage through 305, the liquid is then flowed
through the ACBDC 303. The ACBDC 303 may be capable of removing
both anions and cations. The remaining anions are attracted to the
adjacent anode chamber 301 under the influence of the applied
electric field and may be allowed to pass through a first AM 302
and may be removed from the liquid. The remaining cations are
attracted toward the cathode under the influence of the applied
electric field and may be allowed to pass through a first CM 304
into the adjacent CDC 305. The CDC 305 typically includes therein
cation exchange materials and may be effective at removing the
contaminant cations. The cations may be allowed to pass through a
second CM 306 and into the CBCC 307. The contaminant cations may be
removed from the system in the CBCC 307. The cations are not
allowed to pass through a second AM 308 that defines the
cathode-side of the CBCC 307. The cations cannot travel toward the
anode because of the influence of the applied electric field.
Therefore, the cations may be effectively contained in the CBCC 307
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 307. The liquid exiting the ACBDC
303 may have a reduced level of both anions and cations relative to
the in-coming liquid stream.
[0153] Water splitting occurs in the ACBDC 303 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the ACBDC 303 may serve to regenerate the AM 302 that separates
the ACBDC 303 from the anode chamber 301 as well as the first CM
304 that separates the ACBDC 303 from the adjacent CDC 305.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and may enter the adjacent CDC 305 where
they may be effective in regenerating the cation exchange material
contained therein.
[0154] FIG. 3B illustrates an EDI apparatus that may be equivalent
to FIG. 3A with the polarity of the electric field reversed (i.e.
the anode and cathodes are switched). That is, the path from anode
to cathode in FIG. 3B traverses the same EDI components in the same
order as the path from cathode to anode in FIG. 3A. The apparatus
illustrated in FIG. 3B comprises an anode chamber 320. The anode
chamber includes an anode therein. An ADC 322 may be placed on the
cathode-side of the anode chamber 320. The anode chamber 320 and
the ADC 322 may be separated by a first AM 321. The ADC typically
includes therein a homogeneous volume of anion exchange material. A
CBDC 324 may be placed on the cathode-side of the ADC 322. The ADC
322 and the CBDC 324 may be separated by a second AM 323. The CBDC
may include therein a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. A CDC 326
may be placed on the cathode-side of the CBDC 324. The CBDC 324 and
the CDC 326 may be separated by a first CM 325. The CDC typically
includes therein a homogeneous volume of cation exchange material.
A CCBCC 328 may be placed on the cathode-side of the CDC 326. The
CDC 326 may be separated from the CCBCC 328 by a second CM 327. The
CCBCC 328 may include therein a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange material.
The CCBCC 328 may be separated from the cathode chamber 330 by a
third AM 329. The cathode chamber includes a cathode therein.
[0155] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 3B comprises first causing the
liquid to be deionized to flow through the CDC 326. The CDC may be
capable of effectively removing contaminant cations from the liquid
stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a second cation exchange membrane 327 and into the CCBCC
328. The contaminant cations may be removed from the system in the
CCBCC 328. The cations are not allowed to pass through a third AM
329 that defines the cathode-side of the CCBCC 328. The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
contained in the CCBCC 328 until they are flushed from the system
by the waste liquid stream that removes ions from the CCBCC 328.
The liquid exiting the CDC 326 may be largely free of cationic
contamination.
[0156] Following the passage through 326, the liquid is then flowed
through the ADC 322. The ADC 322 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 321 and into
the anode chamber 320. The contaminant anions may be removed from
the system in the anode chamber 320. The cations are not allowed to
pass through a second AM 323 that defines the cathode-side of the
ADC 322 and into the CBDC 324. The anions cannot travel toward the
cathode because of the influence of the applied electric field.
Therefore, the anions may be effectively removed in the ADC 322.
The liquid exiting the ADC 322 may be largely free of anionic
contamination.
[0157] Following the passage through 322, the liquid is then flowed
through the CBDC 324. The CBDC 324 may be capable of removing both
anions and cations. The remaining anions are attracted to the
adjacent ADC 322 under the influence of the applied electric field
and may be allowed to pass through a second AM 323 and may be
removed from the liquid. The remaining cations are attracted toward
the cathode under the influence of the applied electric field and
may be allowed to pass through a first CM 325 into the adjacent CDC
326. The CDC 326 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a second cation exchange
membrane 327 and into the CCBCC 328. The contaminant cations may be
removed from the system in the CCBCC 328. The cations are not
allowed to pass through a third AM 329 that defines the
cathode-side of the CCBCC 328. The cations cannot travel toward the
anode because of the influence of the applied electric field.
Therefore, the cations may be effectively contained in the CCBCC
328 until they are flushed from the system by the waste liquid
stream that removes ions from the CCBCC 328. The liquid exiting the
CBDC 324 may have a reduced level of both anions and cations
relative to the in-coming liquid stream.
[0158] Water splitting occurs in the CBDC 324 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 324 may serve to regenerate the second AM 323 that
separates the ADC 322 from the CBDC 324 as well as the first CM 325
that separates the CBDC 324 from the adjacent CDC 326. Hydroxide
ions generated by the water splitting are attracted to the anode
and may enter the adjacent ADC 322 where they may be effective in
regenerating the anion exchange material contained therein.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and may enter the adjacent CDC 326 where
they may be effective in regenerating the cation exchange material
contained therein.
[0159] In FIG. 3B, cations may be drawn into the CCBCC 328 and are
removed from the system by the waste liquid stream. The CBDC 324
may serve as the final ion depletion chamber. The apparatus as
illustrated in FIG. 3B may be operated in continuous mode or in
intermittent mode.
[0160] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
3B comprises first causing the liquid to be deionized to flow
through the ADC 322. The ADC 322 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 321 and into
the anode chamber 320. The contaminant anions may be removed from
the system in the anode chamber 320. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
322 or contained in the anode chamber 320 until they are flushed
from the system by the waste liquid stream that removes ions from
the anode chamber 320. The liquid exiting the ADC 322 may be
largely free of anionic contamination.
[0161] Following the passage through 322, the liquid is then flowed
through the CDC 326. The CDC 326 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a second CM 327
and into the CCBCC 328. The contaminant cations may be removed from
the system in the CCBCC 328. The cations are not allowed to pass
through a third AM 329 that defines the cathode-side of the CCBCC
328. The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations may
be effectively contained in the CCBCC 328 until they are flushed
from the system by the waste liquid stream that removes ions from
the CCBCC 328. The liquid exiting the CDC 326 may be largely free
of cationic contamination.
[0162] Following the passage through 326, the liquid is then flowed
through the CBDC 324. The CBDC 324 may be capable of removing both
anions and cations. The remaining anions are attracted to the
adjacent ADC 322 under the influence of the applied electric field
and may be allowed to pass through a second AM 321 and may be
removed from the liquid. The remaining anions may then pass through
AM 321 and into anode chamber 320. The remaining cations are
attracted toward the cathode under the influence of the applied
electric field and may be allowed to pass through a first CM 325
into the adjacent CDC 326. The CDC 326 typically includes therein
cation exchange materials and may be effective at removing the
contaminant cations. The cations may be allowed to pass through a
second CM 327 and into the CCBCC 328. The contaminant cations may
be removed from the system in the CCBCC 328. The cations are not
allowed to pass through a third AM 329 that defines the
cathode-side of the CCBCC 328. The cations cannot travel toward the
anode because of the influence of the applied electric field.
Therefore, the cations may be effectively contained in the CCBCC
328 until they are flushed from the system by the waste liquid
stream that removes ions from the CCBCC 328. The liquid exiting the
CBDC 324 may have a reduced level of both anions and cations
relative to the in-coming liquid stream.
[0163] Water splitting occurs in the CBDC 324 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 324 may serve to regenerate the second AM 323 that
separates the CBDC 324 from the ADC 322 and AM 321 as well as the
first CM 325 that separates the CBDC 324 from the adjacent CDC 326
and CM 327. Hydroxide ions generated by the water splitting are
attracted to the anode and may enter the adjacent ADC 322 where
they may be effective in regenerating the anion exchange material
contained therein. Additionally, hydronium ions generated by the
water splitting are attracted to the cathode and may enter the
adjacent CDC 326 where they may be effective in regenerating the
cation exchange material contained therein.
[0164] The apparatus illustrated in FIG. 3C comprises an anode
chamber 340. The anode chamber includes an anode therein. An ADC
342 may be placed on the cathode-side of the anode chamber 340. The
anode chamber 340 and the ADC 342 may be separated by a first AM
341. The ADC typically includes therein a homogeneous volume of
anion exchange material. A CBDC 344 may be placed on the
cathode-side of the ADC 342. The ADC 342 and the CBDC 344 may be
separated by a second AM 343. The CBDC may include therein a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material. A CDC 346 may be placed on the
cathode-side of the CBDC 344. The CBDC 344 and the CDC 346 may be
separated by a first CM 345. The CDC typically includes therein a
homogeneous volume of cation exchange material. A CCC 348 may be
placed on the cathode-side of the CDC 346. The CDC 346 may be
separated from the CCC 348 by a second CM 347. The CCC 348 may
include therein a homogeneous volume of anion exchange material, or
a homogeneous volume of cation exchange material, or a mixed ion
exchange material, or a doped anion exchange material, or a doped
cation exchange material. The CCC 348 may be separated from the
cathode chamber 350 by a third AM 349. The cathode chamber includes
a cathode therein.
[0165] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 3C comprises first causing the
liquid to be deionized to flow through the CDC 346. The CDC may be
capable of effectively removing contaminant cations from the liquid
stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a second cation exchange membrane 347 and into the CCC 348.
The contaminant cations may be removed from the system in the CCC
348. The cations are not allowed to pass through a third AM 349
that defines the cathode-side of the CCC 348. The cations cannot
travel toward the anode because of the influence of the applied
electric field. Therefore, the cations may be effectively contained
in the CCC 348 until they are flushed from the system by the waste
liquid stream that removes ions from the CCC 348. The liquid
exiting the CDC 346 may be largely free of cationic
contamination.
[0166] Following the passage through 346, the liquid is then flowed
through the ADC 342. The ADC 342 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 341 and into
the anode chamber 340. The contaminant anions may be removed from
the system in the anode chamber 340. The cations are not allowed to
pass through a second AM 343 that defines the cathode-side of the
ADC 342 and into the CBDC 344. The anions cannot travel toward the
cathode because of the influence of the applied electric field.
Therefore, the anions may be effectively removed in the ADC 342.
The liquid exiting the ADC 342 may be largely free of anionic
contamination.
[0167] Following the passage through 342, the liquid is then flowed
through the CBDC 344. The CBDC 344 may be capable of removing both
anions and cations. The remaining anions are attracted to the
adjacent ADC 342 under the influence of the applied electric field
and may be allowed to pass through a second AM 343 into ADC 342 and
may pass through AM 341 into anode chamber 340 and may be removed
from the liquid. The remaining cations are attracted toward the
cathode under the influence of the applied electric field and may
be allowed to pass through a first CM 345 into the adjacent CDC
346. The CDC 346 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a second CM 347 and into
the CCC 348. The contaminant cations may be removed from the system
in the CCC 348. The cations are not allowed to pass through a third
AM 349 that defines the cathode-side of the CCC 348. The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
contained in the CCC 348 until they are flushed from the system by
the waste liquid stream that removes ions from the CCC 348. The
liquid exiting the CBDC 344 may have a reduced level of both anions
and cations relative to the in-coming liquid stream.
[0168] Water splitting occurs in the CBDC 344 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 344 may serve to regenerate the second AM 343 that
separates the first ADC 342 from the CBDC 344 as well as the first
CM 345 that separates the CBDC 344 from the adjacent CDC 346.
Hydroxide ions generated by the water splitting are attracted to
the anode and may enter the adjacent ADC first 342 where they may
be effective in regenerating the anion exchange material contained
therein. Additionally, hydronium ions generated by the water
splitting are attracted to the cathode and may enter the adjacent
CDC 346 where they may be effective in regenerating the cation
exchange material contained therein.
[0169] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
3C comprises first causing the liquid to be deionized to flow
through the ADC 342. The ADC 342 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 341 and into
the anode chamber 340. The contaminant anions may be removed from
the system in the anode chamber 340. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
342 or contained in the anode chamber 340 until they are flushed
from the system by the waste liquid stream that removes ions from
the anode chamber 340. The liquid exiting the ADC 342 may be
largely free of anionic contamination.
[0170] Following the passage through 342, the liquid is then flowed
through the CDC 346. The CDC 346 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a second CM 347
and into the CCC 348. The contaminant cations may be removed from
the system in the CCC 348. The cations are not allowed to pass
through a third AM 349 that defines the cathode-side of the CCC
348. The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations may
be effectively contained in the CCC 348 until they are flushed from
the system by the waste liquid stream that removes ions from the
CCC 348. The liquid exiting the CDC 346 may be largely free of
cationic contamination.
[0171] Following the passage through 346, the liquid is then flowed
through the CBDC 344. The CBDC 344 may be capable of removing both
anions and cations. The remaining anions are attracted to the
adjacent ADC 342 under the influence of the applied electric field
and may be allowed to pass through a second AM 343 and may be
removed from the liquid. The remaining cations are attracted toward
the cathode under the influence of the applied electric field and
may be allowed to pass through a first CM 345 into the adjacent CDC
346. The CDC 346 typically includes therein cation exchange
materials and may be effective at removing the contaminant cations.
The cations may be allowed to pass through a second CM 347 and into
the CCC 348. The contaminant cations may be removed from the system
in the CCC 348. The cations are not allowed to pass through a third
AM 349 that defines the cathode-side of the CCC 348. The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
contained in the CCC 348 until they are flushed from the system by
the waste liquid stream that removes ions from the CCC 348. The
liquid exiting the CBDC 344 may have a reduced level of both anions
and cations relative to the in-coming liquid stream.
[0172] Water splitting occurs in the CBDC 344 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 344 may serve to regenerate the second AM 343 that
separates the CBDC 344 from the ADC 342 as well as the first CM 345
that separates the CBDC 344 from the adjacent CDC 346. Hydroxide
ions generated by the water splitting are attracted to the anode
and may enter the adjacent ADC 342 where they may be effective in
regenerating the anion exchange material contained therein.
Additionally, hydronium ions generated by the water splitting are
attracted to the cathode and may enter the adjacent CDC 346 where
they may be effective in regenerating the cation exchange material
contained therein.
[0173] The apparatus and methods of use illustrated in FIG. 3A-C
address the electrode fouling and ion exchange degradation problems
since the electrode chambers receive a reduced quantity of the
contaminant ions and water splitting in the composite bed depletion
chambers generates hydronium and hydroxide ions for the
regeneration of the anion membranes, cation membranes, and the
cation exchange materials. As was discussed for the apparatus
illustrated in FIG. 2A and FIG. 2B, the CBCC 207 may be used to
remove the cations and thus minimizes scaling in the cathode
chamber.
[0174] Similar apparatuses to FIG. 3A-C are illustrated in FIGS.
4A-C. In the apparatus illustrated in FIG. 4A, the ACBDC and the AM
adjacent to the anode from the apparatus of FIG. 2A and FIG. 2B
have been removed.
[0175] The apparatus illustrated in FIG. 4A comprises an anode
chamber 401. A CDC 403 may be placed on the cathode-side of the
anode chamber 401. The anode chamber 401 and the CDC 403 may be
separated by a first CM 402. The CDC 403 typically includes therein
a homogeneous volume of cation exchange material. A CBCC 405 may be
placed on the cathode-side of the CDC 403. The CDC 403 and the CBCC
405 may be separated by a second CM 404. The CBCC 405 may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. An ADC 407 may be
placed on the cathode-side of the CBCC 405. The CBCC 405 and the
ADC 407 may be separated by a first AM 406. The ADC 407 typically
includes therein a homogeneous volume of anion exchange material. A
CCBDC 409 may be placed on the cathode-side of the ADC 407. The ADC
407 and the CCBDC 409 may be separated by a second AM 408. The
CCBDC 409 may include therein a mixed ion exchange material, or a
doped anion exchange material, or a doped cation exchange material.
The CCBDC 409 may be separated from a cathode chamber 411 by a
third CM 410. The cathode chamber includes a cathode therein.
[0176] This results in an apparatus with the advantages of minimal
electrode fouling or electrode degradation. The CCBDC 409 may act
as the final ion depletion chamber for the product liquid. Most
contaminant ions may be removed into the CBCC 405. Any cations
present in the product liquid after the ADC 407 may be removed by
the CCBDC 409 and exit into the cathode chamber. Since the quantity
of cations being removed into the cathode chamber may be very
small, scaling in the cathode chamber may be insignificant.
[0177] The apparatus illustrated in FIG. 4A is also advantageous
when deionizing liquids with high concentrations of chloride ions.
In conventional EDI apparatuses where the anions may be removed
through the anode chamber, oxidation may occur wherein chloride may
be oxidized to chlorine, chlorite, and hypochlorite among others.
This may cause degradation of the EDI apparatus. The configuration
as illustrated in FIG. 4A may remove the majority of the anions
through the CBCC chamber, thus resolving the issues present in most
conventional EDI apparatuses. The apparatus as illustrated in FIG.
4A may be operated in continuous mode or in intermittent mode.
[0178] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 4A comprises first causing the
liquid to be deionized to flow through the CDC 403. The CDC 403 may
be capable of effectively removing contaminant cations from the
liquid stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a second CM 404 and into the CBCC 405. The contaminant
cations may be removed from the system in the CBCC 405. The cations
are not allowed to pass through a first AM 406 that defines the
cathode-side of the CBCC 405. The cations cannot travel toward the
anode because of the influence of the applied electric field.
Therefore, the cations may be effectively contained in the CBCC 405
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 405. The liquid exiting the CDC 403
may be largely free of cationic contamination.
[0179] Following the passage through 403, the liquid is then flowed
through the ADC 407. The ADC 407 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 406 and into
the CBCC 405. The contaminant anions may be removed from the system
in the CBCC 405. The anions are not allowed to pass through a
second CM 404 that defines the anode-side of the CBCC 405 and into
the CDC 403. The anions cannot travel toward the cathode because of
the influence of the applied electric field. Therefore, the anions
may be effectively removed in the ADC 407 or contained in the CBCC
405 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 405. The liquid exiting the
ADC 407 may be largely free of anionic contamination.
[0180] Following the passage through 407, the liquid is then flowed
through the CCBDC 409. The CCBDC 409 may be capable of removing
both anions and cations. The remaining cations are attracted to the
adjacent cathode chamber 411 under the influence of the applied
electric field and may be allowed to pass through a third CM 410
and may be removed from the liquid. The remaining anions are
attracted toward the anode under the influence of the applied
electric field and may be allowed to pass through a second AM 408
into the adjacent ADC 407. The ADC 407 typically includes therein
anion exchange materials and may be effective at retaining the
contaminant anions. The anions may be allowed to pass through a
first AM 406 and into the CBCC 405. The contaminant anions may be
removed from the system in the CBCC 405. The anions are not allowed
to pass through a second CM 404 that defines the anode-side of the
CBCC 405. The anions cannot travel toward the cathode because of
the influence of the applied electric field. Therefore, the anions
may be effectively removed in the ADC 407 or contained in the CBCC
405 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 405. The liquid exiting the
CCBDC 409 may have a reduced level of both anions and cations
relative to the in-coming liquid stream.
[0181] Water splitting occurs in the CCBDC 409 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CCBDC 409 may serve to regenerate the third CM 410 that
separates the CCBDC 409 from the cathode chamber 411 as well as the
second AM 408 that separates the CCBDC 409 from the adjacent ADC
407. Additionally, hydroxide ions generated by the water splitting
are attracted to the anode and enter the adjacent ADC 407 where
they may be effective in regenerating the anion exchange material
contained therein.
[0182] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
4A comprises first causing the liquid to be deionized to flow
through the ADC 407. The ADC 407 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 406 and into
the CBCC 405. The contaminant anions may be removed from the system
in the CBCC 405. The anions are not allowed to pass through a
second CM 404 that defines the anode-side of the CBCC 405 and into
the CDC 403. The anions cannot travel toward the cathode because of
the influence of the applied electric field. Therefore, the anions
may be effectively removed in the ADC 407 or contained in the CBCC
405 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 405. The liquid exiting the
ADC 407 may be largely free of anionic contamination.
[0183] Following the passage through 407, the liquid is then flowed
through the CDC 403. The CDC 403 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a second CM 404
and into the CBCC 405. The contaminant cations may be removed from
the system in the CBCC 405. The cations are not allowed to pass
through a first AM 406 that defines the cathode-side of the CBCC
405. The cations cannot travel toward the anode because of the
influence of the applied electric field. Therefore, the cations may
be effectively contained in the CBCC 405 until they are flushed
from the system by the waste liquid stream that removes ions from
the CBCC 405. The liquid exiting the CDC 403 may be largely free of
cationic contamination.
[0184] Following the passage through 403, the liquid is then flowed
through the CCBDC 409. The CCBDC 409 may be capable of removing
both anions and cations. The remaining cations are attracted to the
adjacent cathode chamber 411 under the influence of the applied
electric field and may be allowed to pass through a third CM 410
and may be removed from the liquid. The remaining anions are
attracted toward the anode under the influence of the applied
electric field and may be allowed to pass through a second AM 408
into the adjacent ADC 407. The ADC 407 typically includes therein
anion exchange materials and may be effective at retaining the
contaminant anions. The anions may be allowed to pass through a
first AM 406 and into the CBCC 405. The contaminant anions may be
removed from the system in the CBCC 405. The anions are not allowed
to pass through a second CM 404 that defines the anode-side of the
CBCC 405. The anions cannot travel toward the cathode because of
the influence of the applied electric field. Therefore, the anions
may be effectively removed in the ADC 407 or contained in the CBCC
405 until they are flushed from the system by the waste liquid
stream that removes ions from the CBCC 405. The liquid exiting the
CCBDC 409 may have a reduced level of both anions and cations
relative to the in-coming liquid stream.
[0185] Water splitting occurs in the CCBDC 409 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CCBDC 409 may serve to regenerate the third CM 410 that
separates the CCBDC 409 from the cathode chamber as well as the
second AM 408 that separates the CCBDC 409 from the adjacent ADC
407. Additionally, hydroxide ions generated by the water splitting
are attracted to the anode and enter the adjacent ADC 407 where
they may be effective in regenerating the anion exchange material
contained therein.
Example 3
[0186] An EDI device as shown in FIG. 4A was constructed using
machined high density polyethylene hardware to retain the
electrodes, membranes and resin. The internal flow dimensions of
the ADC 407 were 1.27 cm in diameter and 3.81 cm in length. The
internal flow dimensions of the CBCC 405 were 1.27 cm in diameter
and 1.27 cm in length. The internal flow dimensions of the CDC 403
were 1.27 cm in diameter and 3.81 cm in length. The internal flow
dimensions of the CCBDC 409 were 1.27 cm (diameter) and 1.27 cm
(length). All cation materials were in the hydronium form and all
anion materials were in the hydroxide form.
[0187] The anode chamber 401, for this example, contained platinum
gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). In
contact with the anode and separating the anode chamber 401 from
the ADC 403 was a cation exchange membrane 402 (CMI-7000, a product
of Membranes International, Glen Rock, N.J.). The CDC 403 was
filled with a cation exchange resin (DOWEX.TM. 50W.times.4 (200
mesh), a product of The Dow Chemical Company, Midland, Mich.).
Separating the CDC 403 from the CBCC 405 was a cation exchange
membrane 404 (CMI-7000, a product of Membranes International, Glen
Rock, N.J.). The CBCC 405 chamber contained a mixture of cation
exchange resin (DOWEX.TM. 50W.times.4 (200 mesh), a product of The
Dow Chemical Company, Midland, Mich.) and anion exchange resin
(DOWEX.TM. 1.times.4 (200 mesh), a product of The Dow Chemical
Company, Midland, Mich.). The ion exchange capacity ratio of anion
to cation was 1:1 (a mixed bed). The cation resin and anion resin
were in the in the hydronium and hydroxide forms, respectively. The
CBCC 405 was separated from the ADC 407 by an anion membrane 406
(AMI-7001, a product of Membranes International, Glen Rock, N.J.).
The ADC 407 was filled with an anion exchange resin (DOWEX.TM.
1.times.4 (200 mesh), a product of The Dow Chemical Company,
Midland, Mich.). The ADC 407 was separated from the CCBDC 409 by an
anion exchange membrane 408 (AMI-7001, a product of Membranes
International, Glen Rock, N.J.). The CCBDC 409 was filled contains
a mixture of cation exchange resin (DOWEX.TM. 50W.times.4 (200
mesh), a product of The Dow Chemical Company, Midland, Mich.) and
anion exchange resin (DOWEX.TM. 1.times.4 (200 mesh), a product of
The Dow Chemical Company, Midland, Mich.) in the hydronium and
hydroxide forms, respectively. The ion exchange capacity ratio of
anion to cation was 1:2 (a doped cation bed). Separating the CCBDC
409 from the cathode chamber 411 was a cation exchange membrane 410
(CMI-7000, a product of Membranes International, Glen Rock, N.J.).
A pump (GP40, a product of Dionex, Sunnyvale, Calif.) was use to
deliver RO quality water (specific conductance 10.7 .mu.s/cm) at a
flow rate of 2.0 mL/min to the EDI device shown in FIG. 4. A
conductivity detector (CD20, a product of Dionex, Sunnyvale,
Calif.) with a flow cell was used for the conductivity
measurements. From the pump, the RO water flow was directed to the
CDC 403, then to the ADC 407, next to the CCBDC 409 and then to the
flow through conductivity cell. From the conductivity cell, the
flow was directed to the anode chamber 401 and then the cathode
chamber 411 and finally to waste.
[0188] Initially, the conductance of the water exiting the EDI
device was 2.2 .mu.S/cm. Using a laboratory power supply (E3612A, a
product of Agilent, Santa Clara, Calif.) a constant current of 40
mA was applied and the initial voltage was 48V. Gas evolution was
observed immediately from the anode and cathode chambers. The
initial background conductivity of the product water increased to
48 .mu.S/cm and over a 1 hour period the conductivity decreased to
0.67 .mu.S/cm. The EDI device was allowed to operate continuously
for 9 days. The data in Table 3 shows results for the device of
FIG. 4.
TABLE-US-00003 TABLE 3 Conductance Measurements vs. Time
Conductivity Hours Voltage (.mu.S/cm) 0.0 0.0 2.2 1 41 0.67 2 37
0.23 10 32 0.079 24 20 0.062 48 22 0.071 72 24 0.059 96 24 0.055
120 26 0.055 144 27 0.056 168 26 0.055 192 27 0.055 216 28
0.057
[0189] FIG. 4B illustrates an EDI apparatus that may be equivalent
to FIG. 4A with the polarity of the electric field reversed (i.e.
the anode and cathodes are switched). That is, the path from anode
to cathode in FIG. 4B traverses the same EDI components in the same
order as the path from cathode to anode in FIG. 4A. The apparatus
illustrated in FIG. 4B comprises an anode chamber 420. The anode
chamber includes an anode therein. An ACBCC 422 may be placed on
the cathode-side of the anode chamber 420. The anode chamber 420
and the ACBCC 422 may be separated by a first CM 421. The ACBCC 422
may include therein a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. An ADC 424
may be placed on the cathode-side of the ACBCC 422. The ACBCC 422
and the ADC 424 may be separated by a first AM 423. The ADC 424
typically includes therein a homogeneous volume of anion exchange
material. A CBDC 426 may be placed on the cathode-side of the ADC
424. The ADC 424 and the CBDC 426 may be separated by a second AM
425. The CBDC 426 may include therein a mixed ion exchange
material, or a doped anion exchange material, or a doped cation
exchange material. A CDC 428 may be placed on the cathode-side of
the CBDC 426. The CBDC 426 and the CDC 428 may be separated by a
second CM 427. The CDC 428 typically includes therein a homogeneous
volume of cation exchange material. The CDC 428 may be separated
from a cathode chamber 430 by a third CM 429. The cathode chamber
includes a cathode therein.
[0190] This results in an apparatus with the advantages of minimal
anode fouling or anode degradation. The CBDC 426 may act as the
final ion depletion chamber for the product liquid. Most
contaminant anions may be removed into the ACBCC 422. Any cations
present in the product liquid after the CDC 428 may be removed by
the CBDC 426.
[0191] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 4B comprises first causing the
liquid to be deionized to flow through the CDC 428. The CDC 428 may
be capable of effectively removing contaminant cations from the
liquid stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a third CM 429 and into the cathode chamber 430. The
contaminant cations may be removed from the system in the cathode
chamber 430. The cations cannot travel toward the anode because of
the influence of the applied electric field. Therefore, the cations
may be effectively contained in the cathode chamber 430 until they
are flushed from the system by the waste liquid stream that removes
ions from the cathode chamber 430. The liquid exiting the CDC 428
may be largely free of cationic contamination.
[0192] Following the passage through 428, the liquid is then flowed
through the ADC 424. The ADC 424 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 423 and into
the ACBCC 422. The contaminant anions may be removed from the
system in the ACBCC 422. The anions are not allowed to pass through
a first CM 421 that defines the anode-side of the ACBCC 422 and
into the anode chamber 420. The anions cannot travel toward the
cathode because of the influence of the applied electric field.
Therefore, the anions may be effectively removed in the ADC 424 or
contained in the ACBCC 422 until they are flushed from the system
by the waste liquid stream that removes ions from the ACBCC 422.
The liquid exiting the ADC 424 may be largely free of anionic
contamination.
[0193] Following the passage through 424, the liquid is then flowed
through the CBDC 426. The CBDC 426 may be capable of removing both
anions and cations. The remaining cations are attracted to the
cathode chamber 430 under the influence of the applied electric
field and may be allowed to pass through a second CM 427 and into
the CDC 428. The remaining anions are attracted toward the anode
under the influence of the applied electric field and may be
allowed to pass through a second AM 425 into the adjacent ADC 424.
The ADC 424 typically includes therein anion exchange materials and
may be effective at retaining the contaminant anions. The anions
may be allowed to pass through a first AM 423 and into the ACBCC
422. The contaminant anions may be removed from the system in the
ACBCC 422. The anions are not allowed to pass through a first CM
421 that defines the anode-side of the ACBCC 422. The anions cannot
travel toward the cathode because of the influence of the applied
electric field. Therefore, the anions may be effectively removed in
the ADC 424 or contained in the ACBCC 422 until they are flushed
from the system by the waste liquid stream that removes ions from
the ACBCC 422. The liquid exiting the CBDC 426 may have a reduced
level of both anions and cations relative to the in-coming liquid
stream.
[0194] Water splitting occurs in the CBDC 426 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 426 may serve to regenerate the second CM 427 that
separates the CBDC 426 from the CDC 428 as well as the second AM
425 that separates the CBDC 426 from the adjacent ADC 424.
Hydroxide ions generated by the water splitting are attracted to
the anode and enter the adjacent ADC 424 where they may be
effective in regenerating the anion exchange material contained
therein. Additionally, hydronium ions generated by the water
splitting are attracted to the cathode and may enter the adjacent
CDC 428 where they may be effective in regenerating the cation
exchange material contained therein.
[0195] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
4B comprises first causing the liquid to be deionized to flow
through the ADC 424. The ADC 424 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 423 and into
the ACBCC 422. The contaminant anions may be removed from the
system in the ACBCC 422. The anions are not allowed to pass through
a first CM 421 that defines the anode-side of the ACBCC 422 and
into the anode chamber 420. The anions cannot travel toward the
cathode because of the influence of the applied electric field.
Therefore, the anions may be effectively removed in the ADC 424 or
contained in the ACBCC 422 until they are flushed from the system
by the waste liquid stream that removes ions from the ACBCC 422.
The liquid exiting the ADC 424 may be largely free of anionic
contamination.
[0196] Following the passage through 424, the liquid is then flowed
through the CDC 428. The CDC 428 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a third CM 429
and into the cathode chamber 430. The contaminant cations may be
removed from the system in the cathode chamber 430. The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
contained in the cathode chamber 430 until they are flushed from
the system by the waste liquid stream that removes ions from the
cathode chamber 430. The liquid exiting the CDC 428 may be largely
free of cationic contamination.
[0197] Following the passage through 428, the liquid is then flowed
through the CBDC 426. The CBDC 426 may be capable of removing both
anions and cations. The remaining cations are attracted to the
cathode under the influence of the applied electric field and may
be allowed to pass through a second CM 427 and into the adjacent
CDC 428. The remaining anions are attracted toward the anode under
the influence of the applied electric field and may be allowed to
pass through a second AM 425 into the adjacent ADC 424. The ADC 424
typically includes therein anion exchange materials and may be
effective at retaining the contaminant anions. The anions may be
allowed to pass through a first AM 423 and into the ACBCC 422. The
contaminant anions may be removed from the system in the ACBCC 422.
The anions are not allowed to pass through a first CM 421 that
defines the anode-side of the ACBCC 422. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
424 or contained in the ACBCC 422 until they are flushed from the
system by the waste liquid stream that removes ions from the ACBCC
422. The liquid exiting the CBDC 426 may have a reduced level of
both anions and cations relative to the in-coming liquid
stream.
[0198] Water splitting occurs in the CBDC 426 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 426 may serve to regenerate the second CM 427 that
separates the CBDC 426 from the CDC 428 as well as the second AM
425 that separates the CBDC 426 from the adjacent ADC 424.
Additionally, hydroxide ions generated by the water splitting are
attracted to the anode and enter the adjacent ADC 424 where they
may be effective in regenerating the anion exchange material
contained therein. Additionally, hydronium ions generated by the
water splitting are attracted to the cathode and may enter the
adjacent CDC 428 where they may be effective in regenerating the
cation exchange material contained therein.
[0199] The apparatus illustrated in FIG. 4C comprises an anode
chamber 440. The anode chamber includes an anode therein. An ACC
442 may be placed on the cathode-side of the anode chamber 440. The
anode chamber 440 and the ACC 442 may be separated by a first CM
441. The ACC 442 may include therein a homogeneous volume of anion
exchange material, or a homogeneous volume of cation exchange
material, or a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. An ADC 444
may be placed on the cathode-side of the ACC 442. The ACC 442 and
the ADC 444 may be separated by a first AM 443. The ADC 444
typically includes therein a homogeneous volume of anion exchange
material. A CBDC 446 may be placed on the cathode-side of the ADC
444. The ADC 444 and the CBDC 446 may be separated by a second AM
445. The CBDC 446 may include therein a mixed ion exchange
material, or a doped anion exchange material, or a doped cation
exchange material. A CDC 448 may be placed on the cathode-side of
the CBDC 446. The CBDC 446 and the CDC 448 may be separated by a
second CM 447. The CDC 448 typically includes therein a homogeneous
volume of cation exchange material. The CDC 448 may be separated
from a cathode chamber 450 by a third CM 449. The cathode chamber
includes a cathode therein.
[0200] This results in an apparatus with the advantages of minimal
anode fouling or anode degradation. The CBDC 446 may act as the
final ion depletion chamber for the product liquid. Most
contaminant anions may be removed into the ACC 442. Any cations
present in the product liquid after the CDC 448 may be removed by
the CBDC 446.
[0201] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 4C comprises first causing the
liquid to be deionized to flow through the CDC 448. The CDC 448 may
be capable of effectively removing contaminant cations from the
liquid stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a third CM 449 and into the cathode chamber 450. The
contaminant cations may be removed from the system in the cathode
chamber 450. The cations cannot travel toward the anode because of
the influence of the applied electric field. Therefore, the cations
may be effectively contained in the cathode chamber 450 until they
are flushed from the system by the waste liquid stream that removes
ions from the cathode chamber 450. The liquid exiting the CDC 448
may be largely free of cationic contamination.
[0202] Following the passage through 448, the liquid is then flowed
through the ADC 444. The ADC 444 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 443 and into
the ACC 442. The contaminant anions may be removed from the system
in the ACC 442. The anions are not allowed to pass through a first
CM 441 that defines the anode-side of the ACC 442 and into the
anode chamber 440. The anions cannot travel toward the cathode
because of the influence of the applied electric field. Therefore,
the anions may be effectively removed in the ADC 444 or contained
in the ACC 442 until they are flushed from the system by the waste
liquid stream that removes ions from the ACC 442. The liquid
exiting the ADC 444 may be largely free of anionic
contamination.
[0203] Following the passage through 444, the liquid is then flowed
through the CBDC 446. The CBDC 446 may be capable of removing both
anions and cations. The remaining cations are attracted to the
cathode under the influence of the applied electric field and may
be allowed to pass through a second CM 447 and into the CDC 448.
The remaining anions are attracted toward the anode under the
influence of the applied electric field and may be allowed to pass
through a second AM 445 into the adjacent ADC 444. The ADC 444
typically includes therein anion exchange materials and may be
effective at retaining the contaminant anions. The anions may be
allowed to pass through a first AM 443 and into the ACC 442. The
contaminant anions may be removed from the system in the ACC 442.
The anions are not allowed to pass through a first CM 441 that
defines the anode-side of the ACC 442. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
444 or contained in the ACC 442 until they are flushed from the
system by the waste liquid stream that removes ions from the ACC
442. The liquid exiting the CBDC 446 may have a reduced level of
both anions and cations relative to the in-coming liquid
stream.
[0204] Water splitting occurs in the CBDC 446 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 446 may serve to regenerate the second CM 447 that
separates the CBDC 446 from the CDC 448 as well as the second AM
445 that separates the CBDC 446 from the adjacent ADC 444.
Hydroxide ions generated by the water splitting are attracted to
the anode and enter the adjacent ADC 444 where they may be
effective in regenerating the anion exchange material contained
therein. Additionally, hydronium ions generated by the water
splitting are attracted to the cathode and may enter the adjacent
CDC 448 where they may be effective in regenerating the cation
exchange material contained therein.
[0205] Another method (not shown) for performing
electrodeionization utilizing the apparatus as illustrated in FIG.
4C comprises first causing the liquid to be deionized to flow
through the ADC 444. The ADC 444 may be capable of effectively
removing contaminant anions from the liquid stream. The anions are
attracted to the anode under the influence of the applied electric
field and may be allowed to pass through a first AM 443 and into
the ACC 442. The contaminant anions may be removed from the system
in the ACC 442. The anions are not allowed to pass through a first
CM 441 that defines the anode-side of the ACC 442 and into the
anode chamber 440. The anions cannot travel toward the cathode
because of the influence of the applied electric field. Therefore,
the anions may be effectively removed in the ADC 444 or contained
in the ACC 442 until they are flushed from the system by the waste
liquid stream that removes ions from the ACC 442. The liquid
exiting the ADC 444 may be largely free of anionic
contamination.
[0206] Following the passage through 444, the liquid is then flowed
through the CDC 448. The CDC 448 may be capable of effectively
removing contaminant cations from the liquid stream. The cations
are attracted to the cathode under the influence of the applied
electric field and may be allowed to pass through a third CM 449
and into the cathode chamber 450. The contaminant cations may be
removed from the system in the cathode chamber 450. The cations
cannot travel toward the anode because of the influence of the
applied electric field. Therefore, the cations may be effectively
contained in the cathode chamber 450 until they are flushed from
the system by the waste liquid stream that removes ions from the
cathode chamber 450. The liquid exiting the CDC 448 may be largely
free of cationic contamination.
[0207] Following the passage through 448, the liquid is then flowed
through the CBDC 446. The CBDC 446 may be capable of removing both
anions and cations. The remaining cations are attracted to the
cathode under the influence of the applied electric field and may
be allowed to pass through a second CM 447 and into the adjacent
CDC 448. The remaining anions are attracted toward the anode under
the influence of the applied electric field and may be allowed to
pass through a second AM 445 into the adjacent ADC 444. The ADC 444
typically includes therein anion exchange materials and may be
effective at retaining the contaminant anions. The anions may be
allowed to pass through a first AM 443 and into the ACC 442. The
contaminant anions may be removed from the system in the ACC 442.
The anions are not allowed to pass through a first CM 441 that
defines the anode-side of the ACC 442. The anions cannot travel
toward the cathode because of the influence of the applied electric
field. Therefore, the anions may be effectively removed in the ADC
444 or contained in the ACC 442 until they are flushed from the
system by the waste liquid stream that removes ions from the ACC
442. The liquid exiting the CBDC 446 may have a reduced level of
both anions and cations relative to the in-coming liquid
stream.
[0208] Water splitting occurs in the CBDC 446 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CBDC 446 may serve to regenerate the second CM 447 that
separates the CBDC 446 from the CDC 448 as well as the second AM
445 that separates the CBDC 446 from the adjacent ADC 444.
Additionally, hydroxide ions generated by the water splitting are
attracted to the anode and enter the adjacent ADC 444 where they
may be effective in regenerating the anion exchange material
contained therein. Additionally, hydronium ions generated by the
water splitting are attracted to the cathode and may enter the
adjacent CDC 448 where they may be effective in regenerating the
cation exchange material contained therein.
[0209] The apparatus and methods of use illustrated in FIGS. 4A-C
address the electrode fouling and ion exchange degradation problems
since the electrode chambers may receive a reduced quantity of the
contaminant ions and water splitting in the composite bed depletion
chambers generates hydronium and hydroxide ions for the
regeneration of the anion membranes, cation membranes, anion
exchange materials, and the cation exchange materials.
[0210] In summary, the EDI apparatuses shown in FIGS. 2, 3, and 4
offer the advantages of homogeneous ion depletion chambers for
enhanced ion removal, at least one composite bed depletion chamber
for the final removal ("polishing") of trace ionic contaminants, at
least one concentrate chamber for removal of ions, reduced
electrode fouling or chemical degradation of ion exchange materials
in the vicinity of the electrodes, and a simple design requiring
only a single pair of electrodes.
[0211] In some applications, it may be desirable to remove a
selective group of ions such as anion or cations, but the complete
removal of both types of ions is not required. In this case, a
simplified apparatus may be employed. The following discussion
describes dual depletion chamber electrodeionization apparatuses
which may be particularly configured for selective ion removal and
may be interfaced directly to chemical analyzers or other
analytical instrumentation.
[0212] Previously, multi depletion chamber apparatuses for the
production of ultra pure liquid were discussed. These apparatuses
comprised three or more discreet ion depletion chambers. In these
configurations, these apparatuses combined the advantages of
homogeneous ion exchange beds for enhanced ion removal, composite
ion exchange bed(s) for the final removal of trace ionic
contaminants, concentrate chamber(s) for removal of ions, and a
simple design requiring only a single pair of electrodes. The
apparatuses in the previous discussion contained at least one
cation, at least one anion, at least one composite depletion, and
at least one concentrate chambers.
[0213] Another embodiment of the present invention is illustrated
in FIG. 5. The apparatus illustrated in FIG. 5 comprises an anode
chamber 501 including an anode therein. An ADC 503 may be placed on
the cathode-side of the anode chamber 501. The anode chamber 501
and the ADC 503 may be separated by a first AM 502. The ADC 503
typically includes therein a homogeneous volume of anion exchange
material. A CCBDC 505 may be placed on the cathode-side of the ADC
503. The CCBDC 505 and the ADC 503 may be separated by a second AM
504. The CCBDC 505 may include therein a mixed ion exchange
material, or a doped anion exchange material, or a doped cation
exchange material. The CCBDC 505 may be separated from a cathode
chamber 507 by a CM 506. The cathode chamber 507 typically includes
a cathode therein. The apparatus as illustrated in FIG. 5 may be
operated in continuous mode or in intermittent mode.
[0214] A method for performing electrodeionization utilizing the
apparatus is illustrated in FIG. 5. The liquid may be initially
directed through the ADC 503. The ADC 503 typically includes
therein an inlet and an outlet port. The inlet and outlet ports may
be configured so that the liquid may travel through substantially
all of the length of the ADC 503. The inlet port is positioned
closest to the first AM 502 to minimize the distance the anions
must travel under the force of the electric field into the anode
chamber 501. This typically maximizes the interaction between the
liquid and the anion exchange material. The ADC 503 may remove most
of the anions from the liquid. The anions will be attracted toward
the anode by the applied electric field. The anions may be allowed
to pass through the first AM 502 and into the anode chamber 501
where they may be removed by the waste stream used to flush the
anode chamber 501. Cations will be retained within the liquid.
Although the cations will be attracted toward the cathode by the
applied electric field, they will not be allowed to pass through
the second AM 504 of the cathode-side of the ADC 503.
[0215] Following the passage through 503, the liquid then passes
through the CCBDC 505 where both anions and cations may be removed
from the liquid. The cations will be attracted toward the cathode
by the applied electric field. The cations may pass through the CM
506 and into the cathode chamber 507 where they may be removed from
the system. The anions will be attracted toward the anode by the
applied electric field. The anions may pass through the second AM
504, through the ADC 503, through the first AM 502 and into the
anode chamber 501 where they may be removed from the system. The
apparatus of FIG. 5 may produce liquid with significantly reduced
levels of anions and reduced levels of cations.
[0216] The CM 506, ADC 503, first AM 502, and second AM 504
illustrated in FIG. 5 may be regenerated by water splitting that
occurs within the CCBDC 505. Hydroxide ions will be attracted
toward the anode by the applied electric field and may regenerate
the ADC 503, first AM 502, and second AM 504 as they travel toward
the anode. The CM 506 may be regenerated by water splitting that
occurs within the CCBDC 505. Hydronium ions will be attracted
toward the cathode by the applied electric field and may regenerate
the CM 506 as they travel toward the cathode.
[0217] The apparatus as illustrated in FIG. 5 is thus capable of
being used in a manner that renders it suitable for deionization,
especially anion removal, for low ionic strength liquids. Examples
of low ionic strength liquids include water that has received
reverse osmosis, distillation, or prior deionization treatment. The
apparatus as illustrated in FIG. 5 is thus capable of producing a
liquid with very low concentrations of anions and thus may be
suitable for purifying liquids for use in analytical techniques
such as ion chromatography, inductively coupled plasma mass
spectrometry, and atomic absorption spectroscopy, among others.
[0218] Another embodiment of the present invention is illustrated
in FIG. 6. The apparatus illustrated in FIG. 6 comprises an anode
chamber 601 including an anode therein. An ACBDC 603 may be placed
on the cathode-side of the anode chamber 601. The anode chamber 601
and the ACBDC 603 may be separated by an AM 602. The ACBDC 603 may
include therein a mixed ion exchange material, or a doped anion
exchange material, or a doped cation exchange material. A CDC 605
may be placed on the cathode-side of the ACBDC 603. The CDC 605 and
the ACBDC 603 may be separated by a first CM 604. The CDC 605
typically includes therein a homogeneous volume of cation exchange
material. The CDC 605 may be separated from a cathode chamber 607
by a second CM 606. The cathode chamber 607 typically includes a
cathode therein. The apparatus as illustrated in FIG. 6 may be
operated in continuous mode or in intermittent mode.
[0219] A method for performing electrodeionization utilizing the
apparatus is illustrated in FIG. 6. The liquid may be initially
directed through the CDC 605. The CDC 605 typically includes
therein an inlet and an outlet port. The inlet and outlet ports are
configured so that the liquid may travel through substantially all
of the length of the CDC 605. The inlet port is positioned closest
to the second CM 606 to minimize the distance the cations must
travel under the force of the electric field into the cathode
chamber 607. This typically maximizes the interaction between the
liquid and the cation exchange material. The CDC 605 may remove
most of the cations from the liquid. The cations will be attracted
toward the cathode by the applied electric field. The cations may
be allowed to pass through the second CM 606 and into the cathode
chamber 607 where they may be removed by the waste stream used to
flush the cathode chamber 607. Anions will be retained within the
liquid. Although the anions will be attracted toward the anode by
the applied electric field, they will not be allowed to pass
through the first CM 604 on the anode-side of the CDC 605.
[0220] Following the passage through 605, the liquid then passes
through the ACBDC 603 where both anions and cations may be removed
from the liquid. The cations will be attracted toward the cathode
by the applied electric field. The cations may pass through the
first CM 604, through the CDC 605, through the second CM 606 and
into the cathode chamber 607 where they may be removed from the
system. The anions will be attracted toward the anode by the
applied electric field. The anions may pass through the AM 602 and
into the anode chamber 601 where they may be removed from the
system. The apparatus of FIG. 6 may produce liquid with
significantly reduced levels of cations and reduced levels of
anions.
[0221] The AM 602, CDC 605, first CM 604, and second CM 606
illustrated in FIG. 6 may be regenerated by water splitting that
occurs within the ACBDC 603. Hydronium ions will be attracted
toward the cathode by the applied electric field and may regenerate
the first CM 604, CDC 605, and second CM 606 as they travel toward
the cathode. The AM 602 may be regenerated by water splitting that
occurs within the ACBDC 603. Hydroxide ions will be attracted
toward the anode by the applied electric field and may regenerate
the AM 602 as they travel toward the anode.
[0222] The apparatus as illustrated in FIG. 6 is thus capable of
being used in a manner that renders it suitable for deionization,
especially cation removal, for low ionic strength liquids. Examples
of low ionic strength liquids include water that has received
reverse osmosis, distillation, or prior deionization treatment. The
apparatus as illustrated in FIG. 6 is thus capable of producing a
liquid with very low concentrations of cations and thus may be
suitable for purifying liquids for use in analytical techniques
such as ion chromatography, inductively coupled plasma mass
spectrometry, and atomic absorption spectroscopy, among others.
[0223] FIG. 7 illustrates an EDI apparatus comprising two ion
depletion chambers, a concentrate chamber, an anode chamber, and a
cathode chamber. The two electrode chambers and the concentrate
chamber have a flow of waste stream liquid used to flush the
contaminant ions from the chambers. The apparatus illustrated in
FIG. 7 comprises an anode chamber 701 including an anode therein. A
CDC 703 may be placed on the cathode-side of the anode chamber 701.
The anode chamber 701 and the CDC 703 may be separated by a first
CM 702. The CDC 703 typically includes therein a homogeneous volume
of cation exchange material. A CBCC 705 may be placed on the
cathode-side of the CDC 703. The CDC 703 and the CBCC 705 may be
separated by a second CM 704. The CBCC 705 may include therein a
mixed ion exchange material, or a doped anion exchange material, or
a doped cation exchange material. A CCBDC 707 may be placed on the
cathode-side of the CBCC 705. The CBCC 705 and the CCBDC 707 may be
separated by an AM 706. The CCBDC 707 may include therein a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material. The CCBDC 707 may be separated from
a cathode chamber 709 by a third CM 708. The cathode chamber 709
typically includes a cathode therein. The apparatus as illustrated
in FIG. 7 may be operated in continuous mode or in intermittent
mode.
[0224] This results in an apparatus with the advantages of minimal
electrode fouling or electrode degradation. The CCBDC 707 may act
as the final ion depletion chamber for the product liquid. Most
contaminant ions may be removed into the CBCC 705. Any cations
present in the product liquid after the CDC may be removed by the
CCBDC 707 and exit into the cathode chamber. Since the quantity of
cations being removed into the cathode chamber may be very small,
scaling in the cathode chamber may be insignificant.
[0225] The apparatus illustrated in FIG. 7 is also advantageous
when deionizing liquids with high concentrations of chloride ions.
In conventional EDI apparatuses where the anions may be removed
through the anode chamber, oxidation may occur wherein chloride may
be oxidized to chlorine, chlorite, and hypochlorite among others.
This may cause degradation of the EDI apparatus. The configuration
as illustrated in FIG. 7 may remove the majority of the anions
through the CBCC chamber, thus resolving the issues present in most
conventional EDI apparatuses.
[0226] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 7 comprises first causing the
liquid to be deionized to flow through the CDC 703. The interaction
between the liquid and the CDC 703 may be maximized by placing the
inlet to the CDC 703 near the second CM 704 and the outlet of the
CDC 703 near the first CM 702. Alternatively, the inlet port may be
positioned closest to the second CM 704 to minimize the distance
the cations must travel under the force of the electric field into
the CBCC. This causes the liquid to traverse the length of the CDC
703 as it flows from the inlet to the outlet. The CDC 703 may be
capable of effectively removing contaminant cations from the liquid
stream. The cations are attracted to the cathode under the
influence of the applied electric field and may be allowed to pass
through a second CM 704 and into the CBCC 705. The contaminant
cations may be removed from the system in the CBCC 705. The cations
are not allowed to pass through an AM 706 that defines the
cathode-side of the CBCC 705. The cations cannot travel toward the
anode because of the influence of the applied electric field.
Therefore, the cations may be effectively contained in the CBCC 705
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 705. The liquid exiting the CDC 703
may be largely free of cationic contamination.
[0227] Following the passage through 703, the liquid is then flowed
through the CCBDC 707. The interaction between the liquid and the
CCBDC 707 may be maximized by placing the inlet to the CCBDC 707
near the AM 706 and the outlet of the CCBDC 707 near the third CM
708. This causes the liquid to traverse the length of the CCBDC 707
as it flows from the inlet to the outlet. The inlet port is
positioned closest to the AM 706 to minimize the distance the
anions must travel under the force of the electric field into the
CBCC chamber 705. The CCBDC 707 may be capable of removing both
anions and cations. The remaining cations are attracted to the
adjacent cathode chamber 709 under the influence of the applied
electric field and may be allowed to pass through a third CM 708
and may be removed from the liquid. The anions are attracted toward
the anode under the influence of the applied electric field and may
be allowed to pass through an AM 706 into the adjacent CBCC 705.
The contaminant anions may be removed from the system in the CBCC
705. The anions are not allowed to pass through a second CM 704
that defines the anode-side of the CBCC 705. The anions cannot
travel toward the cathode because of the influence of the applied
electric field. Therefore, the anions may be effectively removed in
the CBCC 705 until they are flushed from the system by the waste
liquid stream that removes ions from the CBCC 705. The liquid
exiting the CCBDC 707 may have a reduced level of both anions and
cations relative to the in-coming liquid stream.
[0228] Water splitting occurs in the CCBDC 707 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the CCBDC 707 may serve to regenerate the third CM 708 that
separates the CCBDC 707 from the cathode chamber 709 as well as the
AM 706 that separates the CCBDC 707 from the adjacent CBCC 705.
[0229] The apparatus and method of use illustrated in FIG. 7
address the electrode fouling and ion exchange degradation problems
since the electrode chambers may receive a reduced quantity of the
contaminant ions and water splitting in the composite bed depletion
chambers generates hydronium and hydroxide ions for the
regeneration of the anion membranes, and cation membranes.
[0230] FIG. 8 illustrates an EDI apparatus comprising two ion
depletion chambers, a concentrate chamber, an anode chamber, and a
cathode chamber. The two electrode chambers and the concentrate
chamber have a flow of waste stream liquid used to flush the
contaminant ions from the chambers. The apparatus illustrated in
FIG. 8 comprises an anode chamber 801 including an anode therein.
An ACBDC 803 may be placed on the cathode-side of the anode chamber
801. The anode chamber 801 and the ACBDC 803 may be separated by a
first AM 802. The ACBDC 803 may include therein a mixed ion
exchange material, or a doped anion exchange material, or a doped
cation exchange material. A CBCC 805 may be placed on the
cathode-side of the ACBDC 803. The ACBDC 803 and the CBCC 805 may
be separated by a CM 804. The CBCC 805 may include therein a mixed
ion exchange material, or a doped anion exchange material, or a
doped cation exchange material. An ADC 807 may be placed on the
cathode-side of the CBCC 805. The CBCC 805 and the ADC 807 may be
separated by a second AM 806. The ADC 807 typically includes
therein a homogeneous volume of anion exchange material. The ADC
807 may be separated from a cathode chamber 809 by a third AM 808.
The cathode chamber 809 typically includes a cathode therein. The
apparatus as illustrated in FIG. 8 may be operated in continuous
mode or in intermittent mode.
[0231] In FIG. 8, the majority of the contaminant ions may be drawn
into the CBCC 805. The ACBDC 803 may serve as the final ion
depletion chamber. As the product liquid passes through the ACBDC
803, residual contaminant anions may be removed into the anode
chamber 801. Since the majority of contaminant anions may be
removed by the ADC 807, the trace amounts of residual anions
removed by the ACBDC 803 and into the anode chamber 801 will not
cause significant electrode degradation.
[0232] A method for performing electrodeionization utilizing the
apparatus as illustrated in FIG. 8 comprises first causing the
liquid to be deionized to flow through the ADC 807. The interaction
between the liquid and the ADC 807 may be maximized by placing the
inlet to the ADC 807 near the second AM 806 and the outlet of the
ADC 807 near the third AM 808. This causes the liquid to traverse
the length of the ADC 807 as it flows from the inlet to the outlet.
The ADC 807 may be capable of effectively removing contaminant
anions from the liquid stream. The anions are attracted to the
anode under the influence of the applied electric field and may be
allowed to pass through a second AM 806 and into the CBCC 805. The
contaminant anions may be removed from the system in the CBCC 805.
The anions are not allowed to pass through a CM 804 that defines
the anode-side of the CBCC 805. The anions cannot travel toward the
cathode because of the influence of the applied electric field.
Therefore, the anions may be effectively contained in the CBCC 805
until they are flushed from the system by the waste liquid stream
that removes ions from the CBCC 805. The liquid exiting the ADC 807
may be largely free of anionic contamination.
[0233] Following the passage through 807, the liquid is then flowed
through the ACBDC 803. The interaction between the liquid and the
ACBDC 803 may be maximized by placing the inlet to the ACBDC 803
near the CM 804 and the outlet of the ACBDC 803 near the first AM
802. This causes the liquid to traverse the length of the ACBDC 803
as it flows from the inlet to the outlet. The ACBDC 803 may be
capable of removing both anions and cations. The remaining anions
are attracted to the adjacent anode chamber 801 under the influence
of the applied electric field and may be allowed to pass through a
first AM 802 and may be removed from the liquid. The cations are
attracted toward the cathode under the influence of the applied
electric field and may be allowed to pass through a CM 804 into the
adjacent CBCC 805. The contaminant cations may be removed from the
system in the CBCC 805. The cations are not allowed to pass through
a second AM 806 that defines the cathode-side of the CBCC 805. The
cations cannot travel toward the anode because of the influence of
the applied electric field. Therefore, the cations may be
effectively removed in the CBCC 805 until they are flushed from the
system by the waste liquid stream that removes ions from the CBCC
805. The liquid exiting the ACBDC 803 may have a reduced level of
both anions and cations relative to the in-coming liquid
stream.
[0234] Water splitting occurs in the ACBDC 803 since it may include
therein a mixed ion exchange material, or a doped anion exchange
material, or a doped cation exchange material. The water splitting
in the ACBDC 803 may serve to regenerate the first AM 802 that
separates the ACBDC 803 from the anode chamber 801 as well as the
CM 804 that separates the ACBDC 803 from the adjacent CBCC 805.
[0235] The apparatus and method of use illustrated in FIG. 8
address the electrode fouling and ion exchange degradation problems
since the electrode chambers may receive a reduced quantity of the
contaminant ions and water splitting in the composite bed depletion
chambers generates hydronium and hydroxide ions for the
regeneration of the anion membranes, and cation membranes.
[0236] The foregoing descriptions of exemplary embodiments of the
present invention have been presented for the purpose of
illustration and description. They are not intended to be
exhaustive or to limit the present invention to the precise forms
disclosed, and obviously many modifications, embodiments, and
variations are possible in light of the above teaching.
* * * * *