U.S. patent application number 11/558078 was filed with the patent office on 2007-04-26 for method and system for decreasing molybdenum and/or tungsten concentration in aqueous solutions.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Brian Charles Blakey, Angelo Anthony Bracco, Bang Mo Kim, James Rulon Young Rawson.
Application Number | 20070090036 11/558078 |
Document ID | / |
Family ID | 34972525 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070090036 |
Kind Code |
A1 |
Blakey; Brian Charles ; et
al. |
April 26, 2007 |
METHOD AND SYSTEM FOR DECREASING MOLYBDENUM AND/OR TUNGSTEN
CONCENTRATION IN AQUEOUS SOLUTIONS
Abstract
A method and system for decreasing the concentration of at least
one metal in an aqueous solution. The metal may be molybdenum,
tungsten, or both. An aqueous solution is introduced into at least
one reaction zone, and at least one source of hydroxide ions is
provided into the at least one reaction zone in an amount
sufficient to precipitate at least some of the mass of the at least
one metal. The aqueous solution includes a mass of the at least one
metal and a mass of at least one reducing agent. The at least one
reducing agent includes at least ferrous iron from at least one
source of the at least one reducing agent. A composition of
tungsten ferrite or molybdenum tungsten ferrite may be formed. The
method may be used for purifying water, for the refining of metals,
or to facilitate a chemical analytical determination.
Inventors: |
Blakey; Brian Charles;
(Houston, TX) ; Rawson; James Rulon Young;
(Clifton Park, NY) ; Kim; Bang Mo; (Schenectady,
NY) ; Bracco; Angelo Anthony; (Albany, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
12345
|
Family ID: |
34972525 |
Appl. No.: |
11/558078 |
Filed: |
November 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10873598 |
Jun 23, 2004 |
|
|
|
11558078 |
Nov 9, 2006 |
|
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Current U.S.
Class: |
210/205 ; 423/54;
423/55 |
Current CPC
Class: |
C02F 1/66 20130101; C02F
1/705 20130101; C02F 2101/20 20130101; C02F 1/5245 20130101; C02F
2103/06 20130101; Y10S 210/912 20130101; C02F 1/488 20130101 |
Class at
Publication: |
210/205 ;
423/055; 423/054 |
International
Class: |
C02F 1/52 20060101
C02F001/52 |
Claims
1-19. (canceled)
20. A water purification system comprising at least one reactor
having at least one reaction zone and configured to receive an
aqueous solution in said at least one reaction zone, said aqueous
solution comprising: a) at least one metal comprising molybdenum or
tungsten; and b) at least one reducing agent comprising at least
ferrous iron; wherein said at least one reactor is configured to
receive at least one source of hydroxide ions into said at least
one reaction zone in an amount sufficient to precipitate at least
some of said mass of said at least one metal.
21. The system of claim 20, wherein said source of said at least
one reducing agent is selected from a group consisting of ferrous
sulfate, ferrous chloride, metallic iron, and combinations
thereof.
22. The system of claim 20, wherein said at least one metal
comprises said molybdenum.
23. The system of claim 22, wherein the mass of said ferrous iron
in said aqueous solution is at least about three times the mass of
said molybdenum that is desired to be precipitated from said
aqueous solution.
24. The system of claim 22, wherein the mass of said ferrous iron
in said aqueous solution is at least about six times the mass of
said molybdenum that is desired to be precipitated from said
aqueous solution.
25. The system of claim 20, wherein said at least one metal
comprises said tungsten.
26. The system of claim 25, wherein the mass of said ferrous iron
in said aqueous solution is at least about 1.5 times the mass of
said tungsten that is desired to be precipitated from said aqueous
solution.
27. The system of claim 25, wherein the mass of said ferrous iron
in said aqueous solution is at least about three times the mass of
said tungsten that is desired to be precipitated from said aqueous
solution.
28. The system of claim 20, wherein said at least one reaction zone
is maintained at a pH in a range from about 6 to about 14.
29. The system of claim 20, wherein said at least one reaction zone
is maintained at a temperature in a range from about 0.degree. C.
to about 100.degree. C.
30. The system of claim 20, wherein said at least one reactor is
selected from a group consisting of a continuous tank reactor, a
continuous tubular reactor, a batch reactor, or combinations
thereof.
31. The system of claim 20, wherein said at least one source of
hydroxide ions is selected from a group consisting of sodium
hydroxide, potassium hydroxide, magnesium hydroxide, calcium
hydroxide, magnesium oxide, calcium oxide, calcium carbonate,
potassium carbonate, or combinations thereof.
32. The system of claim 20, wherein a byproduct of the
precipitation is a compound comprising said at least one metal.
33. The system of claim 32, further comprising at least one
recovery device for recovering at least some of said compound.
34. The system of claim 33, wherein said at least one recovery
device comprises a device for settling, filtration, centrifugation,
magnetic separation, or combinations thereof.
35. The system of claim 20, wherein said at least one metal
comprises said tungsten and said molybdenum.
36-38. (canceled)
Description
BACKGROUND
[0001] The invention generally relates to a method and a system for
decreasing the concentration of molybdenum, tungsten, or both in
aqueous solutions, and more particularly for precipitating
molybdenum, tungsten, or both from aqueous solutions.
[0002] A need exists for decreasing the concentration of dissolved
molybdenum and/or dissolved tungsten in aqueous solutions for
several different purposes. Examples of some purposes include the
purification of wastewater, groundwater, drinking water and process
plant water, the refining of metals and the facilitation of
chemical analytical determinations.
[0003] Although a variety of existing processes are known for
decreasing the concentration of molybdenum in aqueous solutions,
the existing processes suffer from one or more disadvantages.
Existing processes for decreasing the concentration of molybdenum
in aqueous solutions often require expensive chemical reagents,
excessive quantities of chemical reagents and/or toxic chemical
reagents. Examples of known processes include co-precipitation with
ferric hydroxide, ferrous hydroxide ammonium molybdate
precipitation, molybdenum sulfide precipitation and precipitation
using organic compounds (see Dannenberg et al., "Molybdenum Removal
from Concentrator Waste Water", U.S. Bureau of Mines Report, July
1982, U.S. Pat. No. 4,211,753 to Pemsler and Litchfield; Beckstead
et al., "Precipitation of Molybdenum Sulfide from Aqueous
Solution", JOURNAL OF METALS, July 1985 and Heininger and Meloan,
"A Selective Reagent for the Removal and Recovery of Chromate,
Molybdate, Tungstate, and Vanadate from Aqueous Solution",
SEPARATION SCIENCE AND TECHNOLOGY, 27, 1992, pp. 663-669).
[0004] Other examples of known processes to decrease the
concentration of molybdenum in aqueous solutions do not involve
precipitation, such as ion exchange and adsorption (see, e.g., U.S.
Pat. No. 3,55,126 to Oberhofer; Wing et al. "Preparation of
Insoluble Cationic Starches and their Use in Heavy Metal Anion
Removal", JOURNAL OF APPLIED POLYMER SCIENCE, 22, 1978, pp.
1405-1416; Zhao et al., "Removal of Molybdate and Arsenate from
Aqueous Solutions by Flotation", SEPARATION SCIENCE AND TECHNOLOGY,
31, 1996, pp. 769-785).
[0005] Few processes are known for decreasing the concentration of
tungsten in aqueous solutions.
[0006] There exists a need for a method and a system for decreasing
the concentration of molybdenum and/or tungsten in aqueous
solutions that have at least one of the following advantages: no
requirement for expensive chemical reagents, no requirement for
excessive quantities of chemical reagents and no requirement for
toxic chemical reagents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 illustrates a water purification system in accordance
with an exemplary embodiment of the invention.
[0008] FIG. 2 illustrates a method for decreasing the concentration
of a metal in an aqueous solution.
SUMMARY
[0009] An embodiment of the invention provides a method for
decreasing the concentration of at least one metal in an aqueous
solution. The metal may be molybdenum, tungsten, or both. The
method includes providing an aqueous solution into at least one
reaction zone, and providing at least one source of hydroxide ions
into the at least one reaction zone in an amount sufficient to
precipitate at least some of the mass of the at least one metal.
The aqueous solution includes a mass of the at least one metal and
a mass of at least one reducing agent. The at least one reducing
agent includes at least ferrous iron from at least one source of
the at least one reducing agent.
[0010] Another embodiment provides a composition comprising
tungsten ferrite. Another embodiment provides a composition
comprising molybdenum tungsten ferrite.
[0011] Another embodiment provides a water purification system,
wherein purification includes decreasing the concentration of at
least one metal. The water comprises wastewater, groundwater,
drinking water, and/or process water. The water purification system
comprises at least one reactor having at least one reaction zone
and configured to receive an aqueous solution into a reaction zone
and at least one source of hydroxide ions into the reaction zone in
an amount sufficient to precipitate at least some of the mass of
the at least one metal. The aqueous solution comprises: (i) a mass
of at least one metal comprising molybdenum or tungsten; and (ii) a
mass of at least one reducing agent comprising at least ferrous
iron.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0012] Reference will now be made in detail to the embodiments of
the invention which are illustrated in the accompanying figures and
examples.
[0013] An embodiment of the invention provides a water purification
system, wherein purification includes decreasing the concentration
of at least one metal. The water may include wastewater,
groundwater, drinking water, and/or process water. The metal may be
molybdenum, tungsten, or both. FIG. 1 is an illustration of a water
purification system 101 in accordance with an exemplary embodiment
of the invention. Water purification system 101 includes at least
one reactor 110, which includes at least one reaction zone 120.
Reaction zone 120 is configured to receive an aqueous solution and
to receive at least one source of hydroxide (OH.sup.-) ions in an
amount sufficient to precipitate at least some of the mass of the
metal. The aqueous solution includes (i) a mass of the metal and
(ii) a mass of at least one reducing agent. The reducing agent
includes at least ferrous iron from at least one source of the
reducing agent.
[0014] The source of the reducing agent includes, but is not
limited to, ferrous sulfate, ferrous chloride, metallic iron, or
combinations thereof. An example of the reducing agent is ferrous
iron. The mass of the ferrous iron, serving as the reducing agent,
may be at least about three times the mass of the molybdenum that
is desired to be precipitated from the aqueous solution. As another
example, the mass of the ferrous iron may be at least about six
times the mass of the molybdenum that is desired to be precipitated
from the aqueous solution.
[0015] Further, the mass of the ferrous iron, serving as the
reducing agent, may be at least about 1.5 times the mass of
tungsten that is desired to be precipitated from the aqueous
solution. As another example, the mass of the ferrous iron may be
at least about three times the mass of the tungsten that is desired
to be precipitated from the aqueous solution.
[0016] The reaction zone 120 may be maintained at a pH in a range
from about 6 to about 14.
[0017] The reaction zone 120 may be maintained at a temperature in
a range from about 0.degree. C. to about 100.degree. C.
[0018] For illustration and not limitation, the reaction zone 120
may be in one or more reactors 110. Each reactor 110 may be a
continuous tank reactor, a continuous tubular reactor, a batch
reactor, or combinations thereof.
[0019] The source of OH.sup.- ions includes, but is not limited to,
sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium
hydroxide, magnesium oxide, calcium oxide, calcium carbonate,
potassium carbonate, or combinations thereof. Furthermore, the
source of OH.sup.- ions may include other sources.
[0020] The water purification system 101 may optionally form a
compound 140 having at least some mass of the metal. The compound
140 is formed as the mass of the metal is precipitated.
Furthermore, the water purification system 101 may optionally
include at least one recovery device 130 for recovering the
compound 140. The recovery device 130 may include a device for
settling 132, filtration 134, centrifugation 136, magnetic
separation 138, or combinations thereof.
[0021] With reference to FIG. 2, next will be described a method
for decreasing the concentration of at least one metal in an
aqueous solution. The metal may be molybdenum, tungsten, or both.
The method includes at Step 200 providing an aqueous solution into
at least one reaction zone, and at Step 205, providing at least one
source of hydroxide ions into the at least one reaction zone in an
amount sufficient to precipitate at least some of the mass of the
at least one metal. The aqueous solution includes a mass of the
metal and a mass of the reducing agent. The reducing agent includes
at least ferrous iron from at least one source of reducing
agent.
[0022] The method of precipitating molybdenum and/or tungsten may
be utilized for the purpose of purifying water, for refining
metals, or for facilitating a chemical analytical
determination.
[0023] The method may be used to form a compound having some mass
of the metal. The compounds that may be formed by the method
include tungsten ferrite (Fe.sub.2WO.sub.4) and molybdenum tungsten
ferrite (Fe.sub.2(Mo, W)O.sub.4).
[0024] Certain aspects of the invention are illustrated in the
following Examples 1 through 10. The following examples are
included for the purpose of exemplification and are not to be
construed as limiting the scope of the present invention.
EXAMPLE 1
[0025] In this example, an aqueous solution of sodium molybdate was
delivered into the reaction zone of a one liter stirred tank
reactor, as was a small volume of an aqueous solution of ferrous
sulfate containing 50 grams of ferrous iron per liter. The volume
of the solution in the reaction zone was approximately 950
milliliters. The concentration of molybdenum in the solution in the
reaction zone was initially about 227 milligrams per liter and the
ratio of the mass of ferrous iron to the mass of molybdenum in the
reaction zone was initially about 3.2. The reactor was heated to
maintain the temperature of the reaction zone at approximately
30.degree. C. The pH of the reaction zone was then raised to and
maintained at approximately 9.7 by delivering into the reaction
zone small volumes of an aqueous solution containing one mole of
sodium hydroxide per liter. A sample was taken from the reaction
zone approximately 20 minutes after adding the sodium hydroxide
solution, and the sample was filtered using a 0.45-micron membrane
filter. The concentration of molybdenum in the filtrate was
measured using inductively coupled plasma emission spectroscopy,
and the percentage of molybdenum precipitated from solution was
determined to be 83. The results are summarized in Table 1.
EXAMPLE 2
[0026] This example was conducted in a manner similar to that of
Example 1 except that the temperature of the reaction zone was
maintained at approximately 60.degree. C. The percentage of
molybdenum precipitated from solution was determined to be 89. The
results are summarized in Table 1.
COMPARATIVE EXAMPLE A
[0027] This comparative example was conducted in a manner similar
to that of Example 2 except that ferrous iron was not added. The
percentage of molybdenum precipitated from solution was determined
to be zero. The results are summarized in Table 1.
EXAMPLE 3
[0028] This example was conducted in a manner similar to that of
Example 1 except that the ratio of the mass of ferrous iron to the
mass of molybdenum was initially about 9.4, and the pH was
maintained at approximately 7.5. The percentage of molybdenum
precipitated from solution was determined to be 78. The results are
summarized in Table 1.
EXAMPLE 4
[0029] This example was conducted in a manner similar to that of
Example 1 except that the temperature was maintained at
approximately 90.degree. C. and the pH was maintained at
approximately 7.5. The percentage of molybdenum precipitated from
solution was determined to be 99. The results are summarized in
Table 1.
EXAMPLE 5
[0030] This example was conducted in a manner similar to that of
Example 2 except that the concentration of molybdenum in the
solution in the reaction zone was initially about 4.9 milligrams
per liter, the ratio of the mass of ferrous iron to the mass of
molybdenum in the reaction zone was initially about 6.0, and the pH
was maintained at approximately 8.5. The percentage of molybdenum
precipitated from solution was determined to be 76. The results are
summarized in Table 1.
EXAMPLE 6
[0031] This example was conducted in a manner similar to that of
Example 4 except that the concentration of molybdenum in the
solution in the reaction zone was initially about 0.46 milligrams
per liter, and the ratio of the mass of ferrous iron to the mass of
molybdenum in the reaction zone was initially about 35. The
percentage of molybdenum precipitated from solution was determined
to be 57. The results are summarized in Table 1 TABLE-US-00001
TABLE 1 Percentage of molybdenum Initial concentration precipitated
from solution of molybdenum Initial ferrous iron-to- Temperature 20
minutes after addition of Example (milligrams per liter) molybdenum
mass ratio (.degree. C.) pH sodium hydroxide solution 1 227 3.2 30
9.7 83 2 219 3.1 60 9.5 89 Comparative 246 0.0 60 9.5 0 Example A 3
230 9.4 30 7.5 78 4 233 3.6 90 7.5 99 5 4.9 6.0 60 8.5 76 6 0.46 35
90 7.5 57
EXAMPLE 7
[0032] In this example, an aqueous solution of sodium molybdate,
containing approximately 243 milligrams of molybdenum per liter,
was delivered into a reaction zone in a one-liter continuous
stirred tank reactor at a rate of approximately 38 milliliters per
minute. An aqueous solution of ferrous sulfate, containing 50 grams
of ferrous iron per liter, was also delivered into the reaction
zone so that the ratio of the mass of ferrous iron delivered into
the reaction zone to the mass of molybdenum delivered into the
reaction zone was about 8.7. An aqueous solution containing 2 moles
sodium hydroxide per liter was also delivered to the reaction zone
to control the pH of the reaction zone at approximately 8.5. The
volume of fluid in the reaction zone was approximately 1200
milliliters, and the residence time of fluid in the reaction zone
was about 30 minutes. The reaction zone was maintained at a
temperature of approximately 20.degree. C. A sample of the fluid
exiting the reactor was taken after at least three reaction zone
volumes had been displaced by solution entering the reactor, and
the sample was filtered using a 0.45-micron membrane filter. The
concentration of molybdenum in the filtrate was measured using
inductively coupled plasma emission spectroscopy and the percentage
of molybdenum precipitated from solution was determined to be 98.
The results are summarized in Table 2.
EXAMPLE 8
[0033] This example was conducted in a manner similar to that of
Example 7 except that the temperature was maintained at
approximately 60.degree. C. The percentage of molybdenum
precipitated from solution was determined to be 98. The results are
summarized in Table 2. TABLE-US-00002 TABLE 2 Initial concentration
Ferrous iron-to- Residence of molybdenum molybdenum mass ratio time
Temperature Percentage of molybdenum Example (milligrams per liter)
fed into reaction zone (minutes) (.degree. C.) pH precipitated from
solution 7 243 8.7 30 20 8.5 98 8 247 8.3 30 60 8.5 98
EXAMPLE 9
[0034] In this example, an aqueous solution of sodium tungstate,
containing approximately 22 milligrams of tungsten per liter, was
delivered into a reaction zone in a one liter continuous stirred
tank reactor at a rate of approximately 39 milliliters per minute.
An aqueous solution of ferrous sulfate, containing 50 grams of
ferrous iron per liter, was also delivered into the reaction zone
so that the ratio of the mass of ferrous iron delivered into the
reaction zone to the mass of tungsten delivered into the reaction
zone was about 32.0. An aqueous solution containing two moles
sodium hydroxide per liter was also delivered to the reaction zone
to control the pH at approximately 9.0. The volume of the fluid in
the reaction zone was approximately 1200 milliliters, and the
residence time of fluid in the reaction zone was approximately 30
minutes. The reaction zone was maintained at a temperature of
approximately 20.degree. C. A sample of the fluid exiting the
reactor was taken after at least three reaction zone volumes had
been displaced by solution entering the reactor, and the sample was
filtered using a 0.45-micron membrane filter. The concentration of
tungsten in the filtrate was measured using inductively coupled
plasma emission spectroscopy and the percentage of tungsten
precipitated from solution was determined to be 64. The results are
summarized in Table 3.
EXAMPLE 10
[0035] This example was conducted in a manner similar to that of
Example 9 except that ratio of the mass of ferrous iron to the mass
of tungsten was about 13.0, the temperature was maintained at
approximately 60.degree. C., and the pH was controlled at
approximately 8.5. The percentage of tungsten precipitated from
solution was determined to be 98. The results are summarized in
Table 3. TABLE-US-00003 TABLE 3 Initial concentration Ferrous
iron-to- Residence of tungsten tungsten mass ratio time Temperature
Percentage of tungsten Example (milligrams per liter) fed into
reaction zone (minutes) (.degree. C.) pH precipitated from solution
9 22 32 30 20 9.0 64 10 22 13 30 60 8.5 98
[0036] Certain aspects of this invention have been illustrated in
the above Examples 1 through 10 for the purpose of exemplification
and are not to be construed as limiting the scope of the invention.
For illustration and not limitation, aspects of the invention
encompass when the metal includes molybdenum and the reducing agent
includes ferrous iron. For example, the mass of ferrous iron was at
least about three times the mass of the molybdenum that is desired
to be precipitated from the aqueous solution. As another example,
the mass of the ferrous iron may be at least about six times the
mass of the molybdenum that is desired to be precipitated from the
aqueous solution.
[0037] While the invention has been described in detail in
connection with only a limited number of aspects, it should be
readily understood that the invention is not limited to such
disclosed aspects. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
* * * * *