U.S. patent application number 14/069997 was filed with the patent office on 2015-05-07 for electrostatic removal of colloidal, soluble and insoluble materials from a fluid.
This patent application is currently assigned to KX Techologies LLC. The applicant listed for this patent is KX Techologies LLC. Invention is credited to Rezan Kareem, Andrew Lombardo.
Application Number | 20150122719 14/069997 |
Document ID | / |
Family ID | 53004957 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150122719 |
Kind Code |
A1 |
Lombardo; Andrew ; et
al. |
May 7, 2015 |
ELECTROSTATIC REMOVAL OF COLLOIDAL, SOLUBLE AND INSOLUBLE MATERIALS
FROM A FLUID
Abstract
A filter that contains an adsorbent to remove the soluble
portion of the contaminant, and then some form of electrostatic
attraction additive. The electrostatic attraction additive would
serve to pull the colloidal and particulate portion of the
contaminant out of fluid, which could be held indefinitely, or be
used to hold while the contaminant is allowed to solubilize and
then be removed by the adsorbent. The electrostatic attraction
additive could either be positively or negatively charged depending
on the surface charge of the particulates that are in the fluid,
and includes particles or fibers charged with charged polymers,
zeolites, cation or anion exchange resin, powdered alumina, or
nano-alumina.
Inventors: |
Lombardo; Andrew; (West
Haven, CT) ; Kareem; Rezan; (Bridgeport, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KX Techologies LLC |
West Haven |
CT |
US |
|
|
Assignee: |
KX Techologies LLC
West Haven
CT
|
Family ID: |
53004957 |
Appl. No.: |
14/069997 |
Filed: |
November 1, 2013 |
Current U.S.
Class: |
210/287 ;
210/335; 210/435 |
Current CPC
Class: |
B01D 39/1615 20130101;
B01D 39/04 20130101; C02F 1/42 20130101; C02F 1/288 20130101; B01D
2239/0435 20130101; B03C 5/02 20130101; B01D 39/1638 20130101; B01D
39/1623 20130101; B01D 39/06 20130101; C02F 1/283 20130101; C02F
2101/20 20130101; C02F 1/285 20130101; C02F 2303/04 20130101 |
Class at
Publication: |
210/287 ;
210/435; 210/335 |
International
Class: |
B03C 5/02 20060101
B03C005/02; B01D 39/16 20060101 B01D039/16 |
Claims
1. A filter for removing soluble, colloidal, and insoluble material
from a fluid comprising: a container for receiving ingress fluid,
and for securing and introducing filter media to said fluid; a
treated filter media for filtering soluble material from said
fluid, said treated filter media including an electrostatic
attraction additive, such that said colloidal particles are
retained through electrostatic attraction within said treated
filter media until becoming soluble in said fluid, and subsequently
passing through the remainder of said filter media, thereby being
removed by said filter media.
2. The filter of claim 1 wherein said electrostatic attraction
additive includes particles or fibers charged with charged
polymers, zeolites, cation or anion exchange resin, powdered
alumina, or nano-alumina, or any combination thereof.
3. The filter media of claim 2 wherein said electrostatic
attraction additive includes charged fibers or charged carbon
filter core with polyDADMAC.
4. The filter media of claim 1 wherein a sufficient amount of said
electrostatic attraction additive necessary to remove said
colloidal material is a combination of a charge on said treated
filter media material, a charge of said colloidal material, a mass
of said colloidal material being removed, a pore size of said
treated filter media, and a flow rate or face velocity of said
colloidal material through said treated filter media.
5. The filter of claim 1 including having fibrillated nanofibers as
one of said filter media.
6. The filter of claim 5 wherein said fibrillated nanofibers
includes cellulose or acrylic compositions.
7. The filter of claim 5 wherein said fibrillated nanofibers
comprise at least one pleated sheet of filter material.
8. The filter of claim 1 including having ion exchange beads,
powder, resins, an adsorbent, zeolites, or carbon as said filter
media.
9. A filter for removing soluble, colloidal, and insoluble material
from a fluid comprising: a container for receiving ingress fluid,
and for securing and introducing filter media to said fluid; a
first treated filter media, treated with an electrostatic
attraction additive for capturing said colloidal material; a second
filter media in fluid communication with said first treated filter
media, for filtering said soluble material from said fluid and from
soluble colloidal material initially electrostatically trapped by
said first treated filter media.
10. The filter of claim 9 wherein said electrostatic attraction
additive includes particles or fibers charged with charged
polymers, zeolites, cation or anion exchange resin, powdered
alumina, or nano-alumina, or any combination thereof.
11. The filter media of claim 10 wherein said electrostatic
attraction additive includes charged fibers or charged carbon
filter core with polyDADMAC.
12. A filter for removing soluble, colloidal, and insoluble
material from a fluid comprising: a container for receiving ingress
fluid, and for securing and introducing filter media to said fluid;
a first treated filter media, treated with an electrostatic
attraction additive for capturing said colloidal material; a second
filter media in fluid communication with said first treated filter
media, for filtering said soluble material from said fluid and from
soluble colloidal material initially electrostatically trapped by
said first treated filter media; and a third filter media adjacent
to, and in fluid communication with, said second filter media
wherein said second and third filter media create a physical
barrier for said colloidal material at their interface for
capturing said colloidal particles; said colloidal particles being
retained by said first treated filter media through electrostatic
attraction, and retained at said interface until becoming soluble
in said fluid, subsequently passing through said interface, and
being removed by said second or third filter media, or both second
and third filter media.
13. The filter of claim 12 wherein said electrostatic attraction
additive includes particles or fibers charged with charged
polymers, zeolites, cation or anion exchange resin, powdered
alumina, or nano-alumina, or any combination thereof.
14. The filter media of claim 13 wherein said electrostatic
attraction additive includes charged fibers or charged carbon
filter core with polyDADMAC.
15. The filter of claim 12 including having fibrillated nanofibers
as one of said filter media.
16. The filter of claim 15 wherein said fibrillated nanofibers
includes cellulose or acrylic compositions.
17. The filter of claim 15 wherein said fibrillated nanofibers
comprise at least one pleated sheet of filter material.
18. The filter media of claim 12 wherein a sufficient amount of
said electrostatic attraction additive necessary to remove said
colloidal material is a combination of a charge on said treated
filter media material, a charge of said colloidal material, a mass
of said colloidal material being removed, a pore size of said
treated filter media, and a flow rate or face velocity of said
colloidal material through said treated filter media.
19. A filter for removing soluble, colloidal, and insoluble
material from a fluid comprising: a container for receiving ingress
fluid, and for securing and introducing filter media to said fluid;
a first treated filter media, for filtering said soluble material
from said fluid and from soluble colloidal material a second filter
media in fluid communication with said first treated filter media
treated with an electrostatic attraction additive for capturing
said colloidal material; and a third filter media adjacent to, and
in fluid communication with, said second filter media wherein said
third filter media removes any remaining soluble material from the
fluid; said colloidal particles being retained by said second
treated filter media through electrostatic attraction, and retained
at said interface until becoming soluble in said fluid,
subsequently passing through said interface, and being removed by
said second or third filter media, or both second and third filter
media.
20. The filter of claim 19 wherein said electrostatic attraction
additive includes particles or fibers charged with charged
polymers, zeolites, cation or anion exchange resin, powdered
alumina, or nano-alumina, or any combination thereof.
21. The filter media of claim 20 wherein said electrostatic
attraction additive includes charged fibers or charged carbon
filter core with polyDADMAC.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a filter for removing
colloidal, soluble, and insoluble materials from a fluid using an
adsorbent to remove the soluble portion of the contaminant, and the
addition of an electrostatic attraction additive to extract the
colloidal and particulate portion of the contaminant out of the
fluid, which could be held indefinitely, or at least while the
contaminant is allowed to solubilize, at which point it is then
removed by the adsorbent.
[0003] 2. Description of Related Art
[0004] Certain water treatment applications are characterized by
the need to remove both dissolved and suspended or colloidal
materials. Although it has been used in numerous consumer products,
toxic metals, such as lead, is known to be harmful to human health
if inhaled or ingested. Important sources of toxic metal exposure
include: ambient air, soil and dust (both inside and outside the
home), food (which can be contaminated by toxic metals in the air
or in food containers), and water (from the corrosion of plumbing).
Materials such as ion exchange resins and reverse osmosis membranes
effectively reduce or fully remove dissolved ionic species.
[0005] Particulate lead at high pH exists primarily as colloidal
lead carbonates. These colloidal particulate solids can be
physically removed if the filter media provides for a fine enough
mesh that can also accommodate pressure differentials.
[0006] It is known to separate particles, such as dirt and dust
particles from a fluid flow using mechanical filters, such as foam
filters, cyclonic separators, and electrostatic separators where
dust particles are charged and then attracted to another oppositely
charged surface for collection. This is the common use of
electrostatic filters.
[0007] Known electrostatic filters include factional electrostatic
filters and electret medium filters. Examples of such filters are
described in EP0815788, U.S. Pat. No. 7,179,314, and U.S. Pat. No.
6,482,252.
[0008] Electrostatic filters are commonly used for air filtration.
In typical electrostatic filter operation, a safe static charge is
produced by forcing air across the filter. This static charge
attracts and traps airborne particles into the filter.
Electrostatic air filters generally work by sieving materials via
fibers that are designed such that when air flows through them they
acquire static charges. Other fibers acquire negative charges and
the charges draw materials in a similar fashion as being drawn by
magnets. Afterwards, filtration takes place leaving the materials
on the surface of the filter.
[0009] In an alternative embodiment to mechanical filters for fine
particle filtration of fluids, including dielectric fluids, fluid
is made to pass through a number of electrodes which are
alternately charged with relatively high positive and negative
voltages. Porous filter material is placed between the electrodes
for trapping the particulates. Particulates, when subjected to the
electric fields created by the application of voltage to the
electrodes, are filtered in one of two possible ways. The filter
material itself may be charged with the particulates being
attracted to the filter material itself. More likely, however, the
particulates are charged, either positively or negatively,
depending on their composition, and the oppositely charged
particles will be attracted to each other and eventually form
larger particulate clusters which will be large enough to be
trapped in the filter material. Whenever enough clusters form to
effectively block the filter, or produce an undesirable pressure
drop, the filter must be replaced.
[0010] Although electrostatic filters have been known in the art
for some time for air filtration, there remains a need in the art
for improved filtration regarding the removal of soluble and
colloidal, non-soluble particles in a fluid, and untested at
present, electrostatic filters may play a role in this removal.
SUMMARY OF THE INVENTION
[0011] Bearing in mind the problems and deficiencies of the prior
art, it is therefore an object of the present invention to provide
a filter for removing soluble, colloidal, and insoluble particles
from a fluid.
[0012] It is another object of the present invention to provide a
filter for removing soluble, colloidal, and insoluble material in a
high pH fluid environment using electrostatic attraction
forces.
[0013] It is yet another object of the present invention to provide
a filter for removing soluble, colloidal, and insoluble material in
a high pH fluid environment using fibrillated nanofibers as one of
the filter media and electrostatic attraction forces.
[0014] It is another object of the present invention to provide a
filter for removing soluble, colloidal, and insoluble lead from a
fluid treated to drinking water specifications using multiple
filter media where at least one filter media includes an
electrostatic attraction additive.
[0015] The above and other objects, which will be apparent to those
skilled in the art, are achieved in the present invention which is
directed to a filter for removing soluble, colloidal, and insoluble
material from a fluid comprising: a container for receiving ingress
fluid, and for securing and introducing filter media to the fluid;
a treated filter media for filtering soluble material from the
fluid, the treated filter media including an electrostatic
attraction additive, such that the colloidal particles are retained
through electrostatic attraction within the treated filter media
until becoming soluble in the fluid, and subsequently passing
through the remainder of the filter media, thereby being removed by
the filter media.
[0016] The electrostatic attraction additive may include particles
or fibers charged with charged polymers, zeolites, cation or anion
exchange resin, powdered alumina, or nano-alumina, or any
combination thereof.
[0017] In one embodiment, the electrostatic attraction additive may
include charged fibers or charged carbon or other charged particles
with polyDADMAC.
[0018] A sufficient amount of the electrostatic attraction additive
necessary to remove charged colloidal material is analytically
derived from a combination of a charge on the treated filter media
material, a charge of the colloidal material, a mass of the
colloidal material being removed, a pore size of the treated filter
media, and a flow rate or face velocity of the colloidal material
through the treated filter media.
[0019] The filter of claim 1 including having fibrillated
nanofibers as one of the filter media. The fibrillated nanofibers
may comprise cellulose or acrylic compositions. The fibrillated
nanofibers may also be fabricated into at least one pleated sheet
of filter material.
[0020] In a second aspect, the present invention is directed to a
filter for removing soluble, colloidal, and insoluble material from
a fluid comprising: a container for receiving ingress fluid, and
for securing and introducing filter media to the fluid; a first
treated filter media, treated with an electrostatic attraction
additive for capturing the colloidal material; a second filter
media in fluid communication with the first treated filter media,
for filtering the soluble material from the fluid and from soluble
colloidal material initially electrostatically trapped by the first
treated filter media.
[0021] In a third aspect, the present invention is directed to a
filter for removing soluble, colloidal, and insoluble material from
a fluid comprising: a container for receiving ingress fluid, and
for securing and introducing filter media to the fluid; a first
treated filter media, treated with an electrostatic attraction
additive for capturing the colloidal material; a second filter
media in fluid communication with the first treated filter media,
for filtering the soluble material from the fluid and from soluble
colloidal material initially electrostatically trapped by the first
treated filter media; and a third filter media adjacent to, and in
fluid communication with, the second filter media wherein the
second and third filter media create a physical barrier for the
colloidal material at their interface for capturing the colloidal
particles; the colloidal particles being retained by the first
treated filter media through electrostatic attraction, and retained
at the interface until becoming soluble in the fluid, subsequently
passing through the interface, and being removed by the second or
third filter media, or both second and third filter media.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The features of the invention believed to be novel and the
elements characteristic of the invention are set forth with
particularity in the appended claims. The figures are for
illustration purposes only and are not drawn to scale. The
invention itself, however, both as to organization and method of
operation, may best be understood by reference to the detailed
description which follows taken in conjunction with the
accompanying drawings in which:
[0023] FIG. 1 is a cross-sectional view of treated filter media of
the present invention for removing soluble and colloidal material
from a fluid;
[0024] FIG. 2 is a cross-sectional view of a two layered filter
media, one layer employing an electrostatic attraction additive,
and a second layer forming a carbon or fiber based filter media
without an electrostatic attraction additive;
[0025] FIG. 3 is a cross-sectional view of a multilayer filter
media depicting a first filter layer and a second filter layer
separated by an electrostatic attraction additive layer, where the
filter media layers are designed in tandem to remove soluble lead
from treated challenge water;
[0026] FIG. 4 depicts two tables, Table I and Table II, where Table
I represents the filtration results of high pH lead treated water,
formulated pursuant to the NSF pH 8.5 protocol, which includes both
soluble lead and particulate lead, and Table II represents
filtration results of high pH lead treated water through a treated
CSF0 filter media layer soaked in RODI water;
[0027] FIG. 5 depicts a graph of the effluent concentration against
the total gallons filtered for the treated and untreated examples
of FIG. 4; and
[0028] FIGS. 6A and 6B depict scanning electron microscope images
of charged filter media of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0029] In describing the preferred embodiment of the present
invention, reference will be made herein to FIGS. 1-6 of the
drawings in which like numerals refer to like features of the
invention.
[0030] The present invention teaches a filter that contains an
adsorbent to remove the soluble portion of a contaminant in the
form of electrostatic attraction additive. The electrostatic
attraction additive serves to pull the colloidal and particulate
portion of the contaminant out of fluid, which could be held
indefinitely, or be used to hold while the contaminant is allowed
to solubilize and then be removed by the adsorbent. The
electrostatic attraction additive could either be positive or
negatively charged depending on the surface charge of the
particulates that are in the fluid. The electrostatic attraction
additive could be, but is not limited to, particles or fibers
charged with charged polymers, zeolites, cation or anion exchange
resin, powdered alumina, nano alumina, and the like.
[0031] In the prior art, the solution to the problem is being taken
care of either by extending the contact time greatly, or using a
mixture of size exclusion, and soluble adsorbents. However, the
size exclusion can severely limit the pore area as well as the flow
rate of a filter depending on the size of the particulates trying
to be removed. Utilizing an electrostatic filtering technique in
combination with other filter media would allow for more open pore
structures in the filters as the particulates would be removed by
the electrostatic attraction and not pore size.
[0032] The requirements for the removal of colloidal lead are
dictated in part by a recent aggressive NSF lead protocol, which
requires the removal of lead in low pH treated challenge water, as
well as high pH treated challenge water. Although the NSF/ANSI
protocol is a governing procedure in the industry for contaminant
removal in drinking water, it is not the only procedure, and the
present invention can be adjusted to accommodate other contaminant
removal protocols that may be different or more or less stringent
than the NSF/ANSI standard.
[0033] In the governing NSF test, about 100 parts-per-billion (ppb)
of soluble lead is introduced in treated challenge water. Another
50 parts per billion are added as insoluble lead. The lead particle
sizes are on the order of 0.1 to 1.2 microns. Generally, particles
on the order of 1 micron or less will remain in suspension.
[0034] In one embodiment, as shown in FIG. 1, a filter 10
comprising a filter media 12 is introduced to treat challenged
water 14. In this example, the treated challenged water 14 includes
colloidal, soluble, and insoluble charged lead particles (Pb+), and
the invention is capable of accommodating other types of charged
particle contaminants. Filter media 12 is typically of a pleated
fabrication, although other filter media configurations are not
precluded. Filter media 12 generally incorporates a microporous
structure that provides colloidal interception capability using an
appropriate pore structure, charge material, chemical treatment, or
a combination thereof. The microporous structure may comprise an
array of active particles that have a specific pore structure, as
well as adsorbent and/or absorbent properties. The array can be a
solid composite block, a monolith, a ceramic candle, or a
flat-sheet composite of bonded or immobilized particles formed into
a coherent medium, all of which may use a binder or supporting
bonding material. These particle arrays may be made through
processes known in the art such as, for example, extrusion,
molding, or slip casting. Flat sheet composites can be made through
processes known in the art such as, for example, papermaking
processes, melt blown processes, air laid process, or woven
processes. For desirable results, the microporous material is
capable of having a mean flow path on the order of 2 microns,
although having a particular mean flow path is not a condition
precedent for practicing the present invention.
[0035] Fibers may also be used as the core filter media. These
fibers may comprise organic polymeric fibers that are capable of
being fibrillated. Fibrillated fibers are generally advantageous
due to their exceptionally fine dimensions and potentially low
cost. Such fibrillated fibers include, but are not limited to,
polymers such as polyamide, acrylic, acrylonitrile; liquid crystal
polymers such as VECTRAN.RTM. from Kuraray Co., Ltd., of Japan, and
ZYLON.RTM. from Toyo Boseki Kabushiki Kaisha Corporation of Japan,
and the like, ion-exchange resins, engineered resins, cellulose,
rayon, ramie, wool, silk, glass, metal, ceramic, other fibrous
materials, or combinations thereof, or a combination of fibers with
particulate media such as, but not limited to, activated carbon,
activated alumina, zeolites, diatomaceous earth, silicates,
aluminosilicates, titanates, bone char, calcium hydroxyapatite,
manganese oxides, iron oxides, magnesia, perlite, talc, polymeric
particulates, clay, iodated resins, ion exchange resins, ceramics,
super absorbent polymers (SAPs), and combinations thereof.
Combinations of organic and inorganic fibers and/or whiskers,
whether fibrillated or not, are contemplated and within the scope
of the invention. For example, glass, ceramic, metal fibers, or
polymeric fibers may be used separately or together. In one
embodiment, fibrillated lyocell fibers, such as LYOCELL BY
LENZING.RTM. from Lenzing Aktiengesellschaft Corporation of
Austria, are employed due to their exceptionally fine dimensions
and potentially low cost.
[0036] The core filter media may also be in the form of a flat
sheet media, potentially made from fibers, or combinations of
fibers and particulate media, which may ultimately be rolled,
layered, and/or pleated for enhanced filtering applications. The
sheets, in turn, may be layered, wrapped, or fabricated into
flow-through forms. The pleated membranes may be utilized as made
or further fabricated into cartridge filters alone or in
combination with other materials.
[0037] The charged or cationic material may be a colloid, a small
charged molecule, or a linear or branched polymer having positively
charged atoms along the length of the polymer chain having a
counter ion associated therewith.
[0038] If the cationic material is a polymer, the charge density
may be greater than about 1 charged atom per about every 20
Angstroms, specifically greater than about 1 charged atom per about
every 12 Angstroms, and more specifically greater than about 1
charged atom per about every 10 Angstroms of molecular length. The
cationic material consistently provides a highly positively charged
surface to the microporous structure as determined by a streaming
or zeta potential analyzer, whether in a high or low pH
environment. Zeta or streaming potentials of the microporous
structure after treatment with a high molecular weight charged
polymer are generally greater than about +6 millivolts, and often
up to about +23 millivolts at a range of pH levels.
[0039] The cationic material generally suitable for use includes,
but is not limited to, quaternized amines, quaternized amides,
quaternary ammonium salts, quaternized imides, benzalkonium
compounds, biguanides, cationic aminosilicon compounds, cationic
cellulose derivatives, cationic starches, quaternized polyglycol
amine condensates, quaternized collagen polypeptides, cationic
chitin derivatives, cationic guar gum, colloids such as cationic
melamine-formaldehyde acid colloids, inorganic treated silica
colloids, polyamide-epichlorohydrin resin, alumina, activated
alumina, nanoalumina cationic acrylamides, polymers and copolymers
thereof, combinations thereof, and the like.
[0040] The unique structure of fibrillated fibers allow much higher
loading of these water treatment materials than can be achieved
with current technology. The loading materials include, but are not
limited to, synthetic organic and inorganic ion exchangers,
zeolites, carbon, adsorbents, and metal oxides, such as titanium
oxide, metal hydroxides, and other filter aids. In inorganic ion
exchangers, cation charges are swapped out for particulates in
water, and in the ion exchange, the positive charge of, for
example, a sodium ion pulls out the cations, which is distinctly
different than electrostatic absorption.
[0041] These materials are generally capable of removing
contaminants from the treated, challenged water; however, they are
not well suited for certain colloidal, soluble, and insoluble
contaminants since the contact time remains limited, especially in
gravity flow applications. In order to achieve sufficient contact
time for captured colloidal and soluble contaminants, an additive
16 having electrostatic properties is combined with filter media
12. The electrostatic attraction additive would serve to pull the
colloidal and particulate portion of the contaminant out of
fluid.
[0042] The fundamental law of electrostatics is that the force
between two charged particles is directly proportional to the
product of their charges and inversely proportional to the square
of the distance between them.
[0043] The fundamental equation of electrostatics is Coulomb's law,
which describes the force between two point charges. The magnitude
of the electrostatic force (in Newtons) between point charges
Q.sub.1 and Q.sub.2 (in coulombs) is directly proportional to the
product of the magnitudes of each charge and inversely proportional
to the surface area of a sphere whose radius is equal to the
distance (in meters) between the charges:
F = Q 1 Q 2 4 .pi. r 2 o ##EQU00001##
[0044] where, .di-elect cons..sub.o is the permittivity of free
space, 1/[.mu..sub.oc.sub.o.sup.2]=8.854187871 (10.sup.-12)
[0045] By the physics of electrostatic charges, the colloidal and
particulate portion of the contaminant may be electrostatically
bound within the filter media indefinitely, or held until the
contaminant is allowed to solubilize and then be removed by the
adsorbent.
[0046] As stated previously, the electrostatic attraction additive
could either be positive or negatively charged depending on the
surface charge of the particulates that are in the fluid. The
electrostatic attraction additive could be, but is not limited to,
particles or fibers charged with charged polymers, zeolites, cation
or anion exchange resin, powdered alumina, nano-alumina, and the
like. The electrostatic attraction additive may be combined with
filter media, or added as a separate layer as depicted in FIG. 2.
The electrostatic attraction additive may be added to fibers by
charging the fibers or carbon filter core with a polymer, such as
polyDADMAC or other additives.
[0047] Referring to FIG. 2, again using a gravity flow model as an
illustrative example, although the present invention is not to be
so limited, filter 20 is exposed to treated challenge water 22
meeting the NSF requirements. Treated challenged water 22 flows
into filter media 24 along with an electrostatic attraction
additive layer 26.
[0048] In this configuration it is further possible to combine
physical barrier attributes of the prior art, although not a
prerequisite for the implementation of the present invention, that
is, allowing the interface region 28 between filter media 24 and
electrostatic attraction additive layer 26 provide a physical
barrier to insoluble, colloidal, and soluble lead, thereby further
retaining the non-dissolved contaminants at the barrier interface
until such time as the contaminants may become soluble and filtered
by filter media 24. This barrier would be in addition to, and in
conjunction with, the suspension of the contaminants by the
electrostatic attractive additive of layer 26.
[0049] Conversely, in the current embodiment, interface region 28
need not be the result a physical barrier that impedes filtration;
rather, an advantage of the present invention is that no such
barrier is necessitated--and unwanted pressure drops are not
realized. This is because the present invention allows for more
open pore structures in the filters, with the particulates being
removed by electrostatic attraction and not pore size.
[0050] In FIG. 3, a multilayer filter media is presented depicting
a first filter layer 32 and a second filter layer 36 separated by
an electrostatic attraction additive layer 34. The filter media
layers are designed in tandem to predominantly to remove soluble
lead from treated challenge water.
[0051] When NSF treated challenge water 38 passes through filter
media layer 32, appreciable amounts of contaminants are removed,
particularly soluble contaminants. Some insoluble and colloidal
contaminants may be suspended in filter media 32; however,
depending upon the looseness of the pore structure, most insoluble
and colloidal contaminants will pass through to electrostatic
attraction additive layer 34. The electrostatic attraction of the
positive particulate lead contaminants (Pb+) stops the travel of
particulate lead, and prohibits particulate lead from passing
through to filtration media 36. The particulate or colloidal lead
is trapped within electrostatic attraction additive layer 26. The
predisposition of particulate or colloidal lead is ultimately to
transform into soluble solution through absorption. Consequently,
the treated challenge water becomes soluble with lead by
solubilizing the colloidal lead until all of the particulate lead
trapped within electrostatic attraction additive layer 34 is
absorbed into the treated challenge water. Once absorbed into the
treated challenged water, the particulate lead is removed by
filtration media 36.
[0052] In the closest prior art, U.S. Pat. No. 8,002,990 issued to
Schroeder on Aug. 23, 2011, titled, "USES OF FIBRILLATED NANOFIBERS
AND THE REMOVAL OF SOLUBLE, COLLOIDAL, AND INSOLUBLE PARTICLES FROM
A FLUID," two filter media create a physical non-soluble particle
barrier at their interface for capturing colloidal and non-soluble
particles, that when retained at the interface, become soluble over
time in the fluid, and are subsequently removed by the second
filter media. This filter media construct forming a physical
barrier for the non-soluble particles is not required in the
present invention. The physical attributes at the interface between
the filter layers are no longer governed by their ability to create
a physical barrier. Rather, electrostatic attraction additive layer
34 attracts and holds the charged non-soluble particles until they
become soluble over time. In the present invention, there is no
need for a filter media to create a physical size exclusion
barrier; that is, form a physical barrier for stopping non-soluble
particles from flowing through the filter media.
[0053] Thus, in the present invention, filter media 12 of FIG. 1,
filter media 26 of FIG. 2, and filter media 34 of FIG. 3, are
non-physical filter media, insomuch as each is not chiefly designed
to stop physical (colloidal) lead particles. Such filter media may
be formed from impregnated paper, although other forms of filter
media may be used provided the filter media is predominantly a
soluble filter media.
[0054] The use of electrostatic attraction to hold onto particles
and colloids as opposed to physical size exclusion may allow the
use of larger pore diameters to be used, but still remove the small
particles.
[0055] In order to achieve the necessary electrostatic attraction,
it is desirable to have the zeta potential as high as possible for
the treated filter media, and of an opposite charge of the
contaminant material being removed. If it is desirable to remove a
positively charged particle, then the treated filter media would
need a negatively charged surface. For example, a treated filter
media that is treated with polyDADMAC is targeting negatively
charged particles. Thus, the polyDADMAC presents a positive surface
charge. The amount of charge necessary to remove a particle is
dependent on the diameter of the pore, the charge of the particle,
the mass of the particle, and the flow rate. Analytically, an
escape velocity is essentially determined, based on the
aforementioned Coulomb's law.
[0056] Since the attraction force is essentially Mass times
Acceleration (F=ma), the force is a scalar (mass)multiplied by the
second derivative of position, and thus a function of time and
position. If a particle is flowing through a pore at a certain flow
rate, it has a certain time in the pore. Sufficient charge (Q1 of
Coulomb's Law) at a specific pore size (the r in Coulombs law would
be 1/2 the pore diameter and therefore force decreases as the pore
size increases)), is required to remove a specific contaminant
charged particle (Q2 of Coulomb's Law) to create enough force to
pull the particle to the surface of the fiber or filter media
"wall" before it escapes the pore with its forward velocity.
[0057] Consequently, assessing the required amount of electrostatic
attraction additive requires a combination of the charge on the
fiber, the charge of the particle, the mass of the particle that is
being removed, length of the pore, the pore size of the filter
media, and the flow rate or face velocity of the contaminant.
[0058] FIG. 4 depicts two tables, Table I and Table II. Table I
represent the filtration results of high pH lead treated water,
formulated pursuant to the NSF pH 8.5 protocol, which includes both
soluble lead and particulate lead. The treated water is filtered
through an untreated filter media layer, having a Canadian Standard
Freeness of zero (CSF0), soaked in reverse osmosis deionized (RODI)
water. The filter media is untreated insomuch as it is not treated
with an electrostatic attraction additive. Test results show a
reduction of contaminants on the order of 77% to 79%. The results
indicate that the untreated filter cannot remove all the lead from
the water, in part because the filter media is not removing the
particulate portion of the solution.
[0059] Table II represents filtration results of high pH lead
treated water through a treated CSF0 filter media layer soaked in
RODI water. The filter media is cellulose based media charged with
polyDADMAC. The polyDADMAC establishes the electrostatic attraction
forces sufficient to suspend the particulate lead. When the filter
media is treated with the electrostatic attraction additive, the
reduction in contaminants is on the order of 95% to 99%,
significantly greater than the untreated test case.
[0060] FIG. 5 depicts a graph 40 of the effluent concentration
against the total gallons filtered for the treated and untreated
examples above. Effluent concentration of the untreated filter
media, depicted by line 42, is substantially higher than the
concentration resulting from the treated filter media, as
represented by line 44. A failure point for the NSF test of 10 ppb
is indicated by line 46.
[0061] FIGS. 6A and 6B depict scanning electron microscope images
of charged filter media of the present invention. A soluble heavy
metal absorbent 50 is interspersed with carbon particles 52 and
charged fibers 54. In these exemplary SEM images, the surfaces of
the fiber in the filter media are charged positive.
[0062] The present invention provides for a filter that contains an
adsorbent to remove the soluble portion of the contaminant, and
then some form of electrostatic attraction additive. The
electrostatic attraction additive would serve to pull the colloidal
and particulate portion of the contaminant out of fluid, which
could be held indefinitely, or be used to hold while the
contaminant is allowed to solubilize and then be removed by the
adsorbent. The electrostatic attraction additive could either be
positively or negatively charged depending on the surface charge of
the particulates that are in the fluid. The electrostatic
attraction additive could be, but not limited to, particles or
fibers charged with charged polymers, zeolites, cation or anion
exchange resin, powdered alumina, nano alumina, and the like.
[0063] Utilizing this method would allow for more open pore
structures in the filters as the particulates would be removed by
the electrostatic attraction and not by pore size.
[0064] While the present invention has been particularly described,
in conjunction with a specific preferred embodiment, it is evident
that many alternatives, modifications and variations will be
apparent to those skilled in the art in light of the foregoing
description. It is therefore contemplated that the appended claims
will embrace any such alternatives, modifications and variations as
falling within the true scope and spirit of the present
invention.
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