Canadian Patents Database / Patent 2444390 Summary

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(12) Patent: (11) CA 2444390
(54) English Title: CHARGE BARRIER FLOW-THROUGH CAPACITOR
(54) French Title: CONDENSATEUR CONTINU A PROTECTION DE CHARGE
(51) International Patent Classification (IPC):
  • H01G 9/004 (2006.01)
  • B01D 61/42 (2006.01)
  • B01D 61/44 (2006.01)
  • B01D 61/52 (2006.01)
  • B01D 61/58 (2006.01)
  • B01D 69/00 (2006.01)
  • B01D 71/00 (2006.01)
  • C25B 13/00 (2006.01)
  • H01G 9/02 (2006.01)
  • H01G 9/04 (2006.01)
  • C02F 1/42 (2006.01)
  • C02F 1/469 (2006.01)
(72) Inventors :
  • ANDELMAN, MARC D. (United States of America)
(73) Owners :
  • VOLTEA, INC. (United States of America)
(71) Applicants :
  • ANDELMAN, MARC D. (United States of America)
(74) Agent: SMART & BIGGAR IP AGENCY CO.
(74) Associate agent:
(45) Issued: 2007-07-03
(86) PCT Filing Date: 2001-04-18
(87) Open to Public Inspection: 2002-10-31
Examination requested: 2003-10-15
(30) Availability of licence: N/A
(30) Language of filing: English

English Abstract




Flow-through capacitors (15) are provided with one or more charge barrier
layers (3). Ions trapped in the pore volume of flow-through capacitors (15)
cause inefficiencies as these ions are expelled during the charge cycle into
the purification path. A charge barrier layer (3) holds these pore volume ions
to one side of a desired flow stream, thereby increasing the efficiency with
which the flow-through capacitor (15) purifies or concentrates ions.


French Abstract

L'invention concerne des condensateurs continus (15) dotés d'une ou de plusieurs couche(s) de protection de charge (3). Les ions piégés dans le volume poreux de condensateurs continus (15) provoquent des déficiences alors que les ions sont expulsés au cours du cycle de charge dans le passage de purification. Une couche de protection de charge (3) retient ces ions de volume poreux d'un côté du flux de passage souhaité, augmentant ainsi l'efficacité avec laquelle le condensateur continu (15) purifie ou concentre les ions.


Note: Claims are shown in the official language in which they were submitted.



CLAIMS:

1. A flow-through capacitor comprising:

(a) a plurality of electrodes comprising an electrode
material having a surface area for electrostatic adsorption
of feed ions;

(b) a pore structure in one or more of said plurality of
electrodes, whereby said electrode is a porous electrode
having a pore volume; and

(c) a first charge barrier material different from said
electrode material, located adjacent to said electrode.


2. The flow-through capacitor of claim 1, wherein the
charge barrier material is characterized by low resistance-
capacitance.


3. The flow-through capacitor of claim 1 or 2,
wherein at least one of the electrodes is an anode and at
least one of the electrodes is a cathode.


4. The flow-through capacitor of claim 1, 2 or 3,
wherein the charge barrier material comprises a first
semipermeable membrane.


5. The flow-through capacitor of claim 4, wherein
said flow-through capacitor further comprises a second
charge barrier material semipermeable membrane, said first
membrane being a cation exchange membrane and said second
membrane being an anion exchange membrane.


6. The flow-through capacitor of claim 5, wherein the
anion exchange membrane is proximal to an anode, and the
cation exchange membrane is proximal to a cathode.


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7. The flow-through capacitor of claim 6, wherein the
locations of the anion and cation exchange membranes
relative to the electrodes are reversed by reversal of
voltage polarity on the electrodes.


8. The flow-through capacitor of claim 5, 6 or 7,
wherein the electrode is operated in the charge cycles of
opposite polarity, separated by discharge cycles.


9. The flow-through capacitor of any one of claims 1
to 8, further comprising a flow channel.


10. The flow-through capacitor of claim 9, wherein the
flow channel is formed by a spacer.


11. The flow-through capacitor of claim 9, wherein the
flow channel is located between one of the electrodes and
the first charge barrier material.


12. The flow-through capacitor of claim 11, further
comprising a second charge barrier material and further
comprising a flow channel located between the first and
second charge barrier materials.


13. The flow-through capacitor of claim 2, wherein the
charge barrier material is an electrically-conductive
membrane with a low resistance-capacitance (RC) time
constant.


14. The flow-through capacitor of claim 13, wherein
the capacitance of the charge barrier material is less than
20 farads/gram.


15. The flow-through capacitor of any one of claims 1
to 14, wherein the charge barrier material is electrically
connected to a first power supply, and at least one of the

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plurality of electrodes is electrically connected to a
second power supply.


16. The flow-through capacitor of any one of claims 1
to 15, wherein the charge barrier material has a voltage and
one or more electrodes of said plurality of electrodes has a
voltage, the charge barrier voltage being greater than the
electrode voltage.


17. The flow-through capacitor of claim 4, further
comprising a second charge barrier material membrane,
wherein the charge barrier membranes are identically-charged
semipermeable membranes, selected from the group consisting
of cation exchange membranes and anion exchange membranes.

18. The flow-through capacitor of any one of claims 1
to 17, wherein the flow-through capacitor comprises a series
resistance of less than 50 ohm cm2.


19. The flow-through capacitor of any one of claims 1
to 18, wherein the flow-through capacitor has a series
resistance to leakage ratio of greater than 100.


20. The flow-through capacitor of any one of claims 1
to 8, wherein the electrodes within a cell of the capacitor
are ionically insulated and connected electrically in
series.


21. The flow-through capacitor of claim 20, further
comprising a flow path adjacent to each of the electrodes.

22. A system comprising the flow-through capacitor of
any one of claims 1 to 21 and a valve.


29



23. The system of claim 22, comprising a means for
allowing fluid in said system to bypass a flow-through
capacitor in said system.


24. The system of claim 22, comprising a means for
directing fluid in said system from said flow-through
capacitor to a second flow-through capacitor in said system.

25. The system of claim 22, 23 or 24, further
comprising a means for monitoring the concentration of ions
in a fluid in said system.


26. The system of any one of claims 22 to 25, further
comprising a means for controlling the concentration of ions
in a fluid in said system.


27. A flow-through capacitor comprising:
(a) a plurality of electrodes; and

(b) a first charge barrier located between two of said
plurality of electrodes, wherein the charge barrier is an
electrically-conductive membrane with a low resistance-
capacitance (RC) time constant material, and wherein the
capacitance of the charge barrier is less than

20 farads/gram.


28. A flow-through capacitor comprising:
(a) a plurality of electrodes; and

(b) a first charge barrier located between two of said
plurality of electrodes, wherein the charge barrier is
electrically connected to a first power supply, and at least
one of the plurality of electrodes is electrically connected
to a second power supply.






29. A flow-through capacitor comprising:
(a) a plurality of electrodes; and

(b) a first charge barrier located between two of said
plurality of electrodes, wherein the flow-through capacitor
comprises a series resistance of less than 50 ohm cm2.


30. A flow-through capacitor comprising:
(a) a plurality of electrodes; and

(b) a first charge barrier located between two of said
plurality of electrodes, wherein the flow-through capacitor
has a series resistance to leakage ratio of greater than
100.


31. A flow-through capacitor comprising:
(a) a plurality of electrodes; and

(b) a first charge barrier located between two of said
plurality of electrodes, wherein the electrodes within a
cell of the flow-through capacitor are ionically insulated
and connected electrically in series.


32. The flow-through capacitor of claim 31, further
comprising a flow path adjacent to each of the electrodes.

33. The flow-through capacitor of claim 1, wherein
said first charge barrier material is a laminate coating on
said electrode material.


34. The flow-through capacitor of claim 33, wherein
said laminate coating is an ion exchange material.



31




35. The flow-through capacitor of claim 33, wherein
said laminate coating is characterized by a low-resistance
capacitance (RC) time constant.


36. The flow-through capacitor of claim 1, wherein
said first charge barrier material is a conductive polymer
sheet material.


37. The flow-through capacitor of claim 1, wherein
said first charge barrier material is material selected from
the group consisting of a fibrous material, a woven
material, and a mesh material.


38. The flow-through capacitor of claim 1, wherein
said first charge barrier material is an aerogel.


39. The flow-through capacitor of claim 1, wherein
said first charge barrier material is a hydrogel.


40. The flow-through capacitor of claim 1, wherein
said first charge barrier material is selected from the
group consisting of a carbon powder material and a graphite
material.


41. The flow-through capacitor of claim 1, wherein
said first charge barrier material infiltrates said at least
a portion of said pore volume of said electrode to form a
combined electrode charge barrier material composite.


42. The flow-through capacitor of claim 1, wherein
said flow-through capacitor comprises a plurality of ion-
depleting and ion-concentrating compartments.


43. The flow-through capacitor of claim 1, wherein
said first charge barrier material is an ion-exchange resin.


32




44. The flow-through capacitor of claim 1, wherein
said first charge barrier material is evenly distributed
throughout said electrode material of one or more of said
plurality of electrodes.


45. The flow-through capacitor of claim 1, wherein
said charge barrier material comprises one or more bipolar
membranes.


46. The flow-through capacitor of claim 1, wherein
said flow-through capacitor has an ionic efficiency of at
least 30%.


47. The flow-through capacitor of claim 1, wherein
said flow-through capacitor has an ionic efficiency of at
least 70%.


48. The flow-through capacitor of claim 1, wherein
said adjacent charge barrier material is within the pore
structure of the electrode.


49. The flow-through capacitor of claim 1, wherein
said adjacent charge barrier material is infiltrated into
the pore structure of the electrode.


50. The flow-through capacitor of claim 1, wherein
said adjacent charge barrier material is a coating layer.

51. The flow-through capacitor of claim 1, wherein
said adjacent charge barrier material is a membrane layer.

52. The flow-through capacitor of claim 1, where said
adjacent charge barrier material is infiltrated into the
pore structure of said porous electrode, said charge barrier
material selected from the group consisting of an ion
exchange polymer and a hydrogel.



33




53. The flow-through capacitor of claim 1, where said
adjacent charge barrier material is a coating blocking the
pore volume of said porous electrode, said charge barrier
material selected from the group consisting of an ion
exchange polymer and a hydrogel.


54. The flow-through capacitor of claim 1, wherein
said pore volume contains pore ions and said electrode has a
ratio of feed ions to pore ions, and wherein said first
charge barrier material increases the ratio of feed ions to
pore ions in said electrode.


55. The flow-through capacitor of claim 1, wherein
said flow-through capacitor has an energy usage of less than
1 joule per coulomb of ionic charge purified.


56. The flow-through capacitor of claim 1, wherein
said flow-through capacitor has an energy usage of less than
0.5 joule per coulomb of ionic charge purified.


57. The flow-through capacitor of claim 1, wherein
said flow-through capacitor has an ionic efficiency of
greater than 50% in the presence of a feed stream having an
ionic concentration of at least 2500 parts per million.


58. The flow-through capacitor of claim 57, wherein
said feed stream has an ionic concentration of at least 6000
parts per million.


59. The flow-through capacitor of claim 3 comprising a
first electric field that is between said anode and cathode,
and further comprising a second electric field that is

within said electrode and inverse to said first electric
field.



34




60. A flow-through capacitor having an ionic
efficiency, said flow-through capacitor comprising:
(a) a plurality of electrodes comprising an electrode

material having a surface area for electrostatic adsorption
of ions;

(b) a pore volume in one or more of said plurality of
electrodes comprising pore volume loss; and

(c) means for enhancing the ionic efficiency of said flow-
through capacitor by compensating for said pore volume loss.

61. A flow-through capacitor comprising:

(a) a plurality of electrodes comprising an electrode
material having a surface area for electrostatic adsorption
of ions;

(b) a pore volume in one or more of said plurality of
electrodes, whereby said pore volume adsorbs and expels pore
volume ions; and

(c) means for reducing said adsorption and expulsion of
pore volume ions.


62. A flow-through capacitor comprising:

(a) a plurality of electrodes comprising an electrode
material having a surface area for electrostatic adsorption
of feed ions;

(b) a pore volume in one or more of said plurality of
electrodes, whereby said pore volume contains pore ions; and
(c) means for providing an excess of feed ions to pore
volume ions.



35




63. The flow-through capacitor of claim 62, further
comprising a feed stream having a flow rate, and means for
altering said flow rate.


64. The flow-through capacitor of claim 62, further
comprising a source of voltage to said flow-through
capacitor, and a means for altering said voltage.


65. The flow-through capacitor of claim 62, further
comprising a means for recovering energy from said flow-
through capacitor.


66. The flow-through capacitor of claim 62, wherein
said flow-through capacitor has a polarity and further
comprises means for reversing said polarity.



36

Note: Descriptions are shown in the official language in which they were submitted.


CA 02444390 2006-06-29
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CHARGE BARRIER FLOW-THROUGH CAPACITOR
Field of the Invention

The invention relates to a flow-through capacitor
for deionizing or decontaminating a fluid.

Background of the Invention

The invention relates to flow-through capacitors
for deionizing solutions, e.g., aqueous solutions, with
improved operation at concentrated solutions, including such
applications as low energy desalination of seawater.

Technologies to deionize water include
electrodeionization and flow-through capacitors. The term
electrodeionization, including electrodialysis and
continuous electrodeionization, has traditionally referred
to a process or device that uses electrodes to transform

electronic current to ionic current by oxidation-reduction
reactions in anolyte and catholyte compartments located at
the anodes and cathodes. Traditionally, the ionic current
has been used for deionization in ion-depleting

compartments, and neither the anolyte chambers, the

catholyte chambers nor the oxidation-reduction products have
participated in the deionization process. In order to avoid
contamination and to allow multiple depletion compartments
between electrodes, the ion-concentrating and ion-depleting
compartments were generally separated from the anolyte and
catholyte compartments. To minimize oxidation-reduction
product formation at the electrodes, electrodeionization
devices typically comprised multiple layers of ion-
concentrating and ion-depleting compartments, bracketed
between pairs of end electrodes.

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One disadvantage of prior art systems is the
energy loss resulting from using multiple compartment layers
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between electrodes, thereby creating an electrical
resistance. This is generally true of prior art
electrodeionization devices and is one characteristic
that differentiates them from flow-through capacitors.
Flow-through capacitors differ in a number of other
ways from electrodeionization as well. One difference is
that flow-through capacitors purify water without
oxidation-reduction reactions. The electrodes
electrostatically adsorb and desorb contaminants, so that
the electrode (anode and cathode) compartments
participate directly in deionization and are located
within one or both of the ion-depleting and ion-
concentrating compartments. The anolyte and catholyte
are partly or largely contained within a porous
electrode. Electronic current is generally not
transmuted by an oxidation-reduction reaction. Instead,
charge is transferred by electrostatic adsorption.
However, flow-through capacitors of the prior art
become energy inefficient and impractical at high ion or
contaminant concentrations. The reason for this is due
to the pore volume in the electrodes. Dissolved
counterion salts present in the pore volume adsorb onto
the electrodes, whereas, pore volume coion salts are
expelled from the electrodes. This has a doubly
deleterious effect. Counterions occupy capacitance
within the electrode. This amount of charge-holding
capacitance is therefore unavailable for purification of
ions from the feed water purification stream. Coions
expelled from the electrodes enter the feed water
purification stream and contaminate it with additional
ions. This effect becomes worse with increased
concentration. The flow-through capacitor is typically
regenerated into liquid of the feed concentration. When
purifying a concentrated liquid, ions are passively
brought over into the pores prior to application of a
voltage or electric current. Once voltage is applied,
these ions are simultaneously adsorbed and expelled
during the purification process. Purification can only
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occur when an excess of feed ions, over and above the pore
volume ions, are adsorbed by the electrodes. This puts an
upper practical limit on the economy of the flow-through
capacitor, typically, in the range of approximately 2500 to

6000 parts per million (ppm). The flow-through capacitor of
the prior art requires both slower flow rates and higher
energy usage. Beyond 6000 ppm, energy usage required is
typically more than 1 joule per coulomb of dissolved ions,
making prior art flow-through capacitors too energy

intensive to be practical. Deionizing seawater, which has
ion concentrations of approximately 35,000 ppm, becomes
impractical to deionize due to energy inefficiency caused by
these pore volume losses. Pore volume losses occur at all
concentrations but get worse at higher concentrations.

Another way to describe pore volume losses is that they
cause diminished ionic efficiency. Ionic efficiency is
defined as the ratio of coulombs of ions purified to
coulombs of electrons utilized.

Thus, a need exists to improve the ionic and

energy efficiency of flow-through capacitors, particularly
when treating solutions with ion concentrations in excess of
2500 ppm. A further need exists for a flow-through
capacitor to purify solutions with an energy usage of less
than 1 joule per coulomb of purified ionic charge. Ionic

efficiency is the coulombs of ionic charge purified per
coulombs of electrons used, and should be 50% or more.
Sturanary of the Invention

According to the present invention, there is
provided a flow-through capacitor comprising: (a) a

plurality of electrodes comprising an electrode material
having a surface area for electrostatic adsorption of feed
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ions; (b) a pore structure in one or more of said plurality
of electrodes, whereby said electrode is a porous electrode
having a pore volume; and (c) a first charge barrier

material different from said electrode material, located
adjacent to said electrode.

Also according to the present invention, there is
provided a flow-through capacitor comprising: (a) a
plurality of electrodes; and (b) a first charge barrier
located between two of said plurality of electrodes, wherein

the charge barrier is an electrically-conductive membrane
with a low resistance-capacitance (RC) time constant
material, and wherein the capacitance of the charge barrier
is less than 20 farads/gram.

According to the present invention, there is

further provided a flow-through capacitor comprising: (a) a
plurality of electrodes; and (b) a first charge barrier
located between two of said plurality of electrodes, wherein
the charge barrier is electrically connected to a first
power supply, and at least one of the plurality of
electrodes is electrically connected to a second power
supply.

According to the present invention, there is
further provided a flow-through capacitor comprising: (a) a
plurality of electrodes; and (b) a first charge barrier

located between two of said plurality of electrodes, wherein
the flow-through capacitor comprises a series resistance of
less than 50 ohm cm2.

According to the present invention, there is
further provided a flow-through capacitor comprising: (a) a
plurality of electrodes; and (b) a first charge barrier

located between two of said plurality of electrodes, wherein
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the flow-through capacitor has a series resistance to
leakage ratio of greater than 100.

According to the present invention, there is
further provided a flow-through capacitor comprising: (a) a
plurality of electrodes; and (b) a first charge barrier

located between two of said plurality of electrodes, wherein
the electrodes within a cell of the flow-through capacitor
are ionically insulated and connected electrically in
series.

According to the present invention, there is
further provided a flow-through capacitor having an ionic
efficiency, said flow-through capacitor comprising: (a) a
plurality of electrodes comprising an electrode material
having a surface area for electrostatic adsorption of ions;

(b) a pore volume in one or more of said plurality of
electrodes comprising pore volume loss; and (c) means for
enhancing the ionic efficiency of said flow-through
capacitor by compensating for said pore volume loss.

According to the present invention, there is

further provided a flow-through capacitor comprising: (a) a
plurality of electrodes comprising an electrode material
having a surface area for electrostatic adsorption of ions;
(b) a pore volume in one or more of said plurality of
electrodes, whereby said pore volume adsorbs and expels pore

volume ions; and (c) means for reducing said adsorption and
expulsion of pore volume ions.

According to the present invention, there is
further provided a flow-through capacitor comprising: (a) a
plurality of electrodes comprising an electrode material

having a surface area for electrostatic adsorption of feed
ions; (b) a pore volume in one or more of said plurality of
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electrodes, whereby said pore volume contains pore ions; and
c) means for providing an excess of feed ions to pore volume
ions.

It has been discovered that a charge barrier

placed adjacent to an electrode of a flow-through capacitor
can compensate for the pore volume losses caused by
adsorption and expulsion of pore volume ions.

Using the charge barrier flow-through capacitor of
the invention, purification of water, including a seawater
concentrated solution, e.g., 35,000 ppm NaCl, has been

observed at an energy level of less than 1 joules per
coulomb ions purified, for example, 0.5 joules per coulomb
ions purified, with an ionic efficiency of over 90%.

As used herein, the term "charge barrier" refers
to a layer of material which is permeable or semipermeable
and is capable of holding an electric charge. Pore ions are
retained, or trapped, on the side of the charge barrier
towards which the like-charged ion, or coion, migrates.

This charge barrier material may be a laminate which has a
conductive low resistance-capacitance (RC) time constant, an
electrode material, or may be a permselective, i.e.,
semipermeable, membrane, for example, a cation or anion
permselective material, such as a cation exchange or anion
exchange membrane. The charge barrier may have a single

polarity, two polarities, or may be bipolar. Generally, a
charge barrier functions by forming a concentrated layer of
ions. The effect of forming a concentrated layer of ions is
what balances out, or compensates for, the losses ordinarily
associated with pore volume ions. This effect allows a

large increase in ionic efficiency, which in turn allows
energy efficient purification of concentrated fluids.

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Description of the Drawings

Fig. 1 is a generalized, schematic view of a flow-
through capacitor of an embodiment of the invention,
illustrating the placement of charge barrier layers,

electrodes, an optional current collector, and a flow
channel spacer.

Fig. 2 is a generalized, schematic view of a flow-
through capacitor of an embodiment of the invention,
containing charge barriers of the same polarity as the

adjacent or underlying electrode, together with a
representation of the ions being purified or concentrated,
and displaying the direction of ion migration in the
electric field.

Fig. 3 represents the flow-through capacitor of
Fig. 2 in the discharge cycle, illustrating the release of
concentrated ions into a flow channel located between the
charge barrier layers.

Fig. 4 is a generalized, schematic view of a flow-
through capacitor of an embodiment of the invention,

containing charge barrier layers of opposite polarity to
that of the adjacent or underlying electrodes, together with
representations of ions being purified or concentrated, and
displaying the direction of ionic migration in the electric
field.

Fig. 5 is a generalized view of the discharge
cycle of the flow-through capacitor of Fig. 4, which
illustrates how a centrally-located flow channel is purified
by virtue of ionic migration through the charge barrier
layers towards the electrodes.

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Fig. 6 is a generalized, schematic view of a
stacked-layer, flow-through capacitor of an embodiment of
the invention.

Fig. 7 is a generally schematic view of a dual-

flow channel, flow-through capacitor of an embodiment of the
invention, with a sealing agent to isolate simultaneously
purified and concentrated fluid streams.

Fig. 8A is a generalized, top schematic view of
the flow-through capacitor of an embodiment of the invention
with transverse flow channels;

Fig. 8B is a front, cross-sectional, generalized
schematic view of the flow-through capacitor of an
embodiment of the invention with transverse flow channels;

Fig. 8C is a top sectional view of the flow-

through capacitor of an embodiment of the invention showing
a charge barrier and a flow spacer;

Fig. 8D is a side sectional, generalized schematic
view of the flow-through capacitor of an embodiment of the
invention with transverse flow channels;

Fig. 9 shows a graph of the data generated from
the flow-through capacitor of an embodiment of the invention
when operated in cycles and is represented by charging and
discharging in polarities according to the sequence depicted
by Figs. 2, 3, 4, and 5;

Fig. 10 is a generalized schematic diagram of the
flow-through capacitor of an embodiment of the invention
showing the attachment of conductive charge barriers to a
separate DC power supply; and

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Fig. 11 is a schematic view of a flow-through
capacitor system of an embodiment of the invention.
Detailed Description

The charge barrier flow-through capacitor of the
invention, the anolyte and catholyte chambers may be
integral with ion-depletion or concentrating chambers, or
they may be separate chambers. The electrodes in flow-
through capacitors are spaced apart or are separated by a
spacer. The spacer may be any ion-permeable,

electronically-nonconductive material, including membranes
and porous and nonporous materials (see U.S. Patent

No. 5,748,437, issued May 5, 1998). The spacer may define a
flow channel (see U.S. Patent No. 5,547,581, issued

August 20, 1996), or may be of a double-layer spacer

material with the flow channel between the layers (as in
U.S. Patent No. 5,748,437). Purification and concentration
may take place in either the spacers, the electrodes, or
both, depending upon the geometry of the flow channel. For
example, in a flow-through capacitor utilizing a double-

space layer as described above, the ion-depleting,
purification, or concentration compartment may be located
between the spacer layers. U.S. Patent

No. 5,192,432, issued March 9, 1993, describes use of a
porous electrode material. In this case, ion depletion or
ion concentration would occur directly in the electrodes
themselves, in order to affect purification or concentration
of a fluid. In both cases, however, the electrodes are
directly involved in the purification process. The
electrodes are used to adsorb or release a charge, and

generally, do not transfer electronic to ionic current by
oxidation-reduction reactions common to electrodeionization
technologies. In either case, no more than a single,

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separately-compartmentalized, concentrating or ion-depleting
layer is required between each set of electrodes.

Therefore, one advantage the flow-through capacitor has over
deionization is that less

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energy is wasted by oxidation-reduction reactions and
there is less internal resistance.
In the flow-through capacitor of the present
invention, the charge barrier may have just one layer or
the charge barrier may have two or more layers. Ion
selective membranes may also be used to select for
particular species of ions of interest. Where the charge
barrier is a permselective membrane, it may be any
membrane, e.g., a nonwoven, a woven, or a semipermeable
sheet material. Examples of materials for use as charge
barriers are available commercially, e.g., Raipore 1010
and 1030, Tokuyama Soda Neosepta CM-1 and AM-
1,(NEOSEPTA is a registered trademark of Tokuyama
Corporation of Mikage-cho Tokuyama City, Yamaguchi
Prefecture Japan) and Selemnion brand anion and cation
exchange membranes. These membranes may be supported by
a web or may be manufactured, cast, or attached
integrally to the electrode material. Bipolar membranes
may also be used.
Where the charge barrier material is a low
resistance-capacitance (RC) time constant material, this
material may be an ionically-permeable, conductive,
porous, or nonporous sheet material, for example,
conductive membranes, conductive polymer sheet materials,
carbon fibrous materials, either in a nonwoven or woven,
e.g., woven cloth form, activated carbon cloths,
nanotubes, carbon or graphite tissue, aerogel, metal mesh
or fibers, perforated graphite or metal foil, activated
carbon, and carbon black sheet materials, including
carbons held together with a polytetrafluoroethylene
(PTFE) binder. These conductive materials may also be
derivatized with the same ionically charged groups common
to anion and cation exchange membranes.
An example of these low RC time constant, conductive
charge barrier material is a low surface area, low
capacitance, carbon black bound with PTFE. For example,
materials with a capacitance of less than 20 farads/gram
or 30 farads/cm2 (as measured in concentrated sulfuric
7


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acid) may be used. A non-electrically conductive, ion-
permeable spacer may be placed between the electrode and the
charge barrier material in order to facilitate formation of
a reverse electric field. In this case, the charge barrier

material may have integral leads, or, may have its own
current ion-permeable collector with leads. These leads may
be hooked up in parallel with the electrode leads or may be
powered by a separate power supply. Optionally, the

separate power supply may be set to a voltage that is higher
than the power supply connected to the electrodes.

In this way, the charge barrier materials contain
a higher voltage than the electrode materials. One
advantage of a discrete power supply is that the charge
barrier materials may remain permanently charged, or may be

charged to a higher voltage than the electrode materials,
thereby enhancing the reverse electric field. It is this
reverse electric field which forms a charge barrier to pore
volume ions, thereby increasing ionic efficiency of the
flow-through capacitor. Alternatively, the same power

supply may be used for both the electrodes and the charge
barrier. Optionally, a resistor may be added to the
electrode lead circuits.

Any electrode of utility in prior art flow-through
capacitors may be used as the underlying electrode material.
For example, small particle size carbons have lower series

resistance. Carbon particles of less than 10 microns, for
example, 1 micron or less, may be formed into an electrode
sheet with PTFE or other binders and calendered or extruded
into sheet electrodes of less than 0.02 inches thick with

low series resistance, less than 40 ohm cm2, where cm2 is the
spacer area.

8


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The charge barrier material may preferably be
combined with the electrode. In this way, the electrode
itself offers structure and strength, so that a thin, weak
charge barrier may be used. For example, a thin coating of

a charge barrier ion exchange material may be applied
directly onto the electrode. Alternatively, the charge
barrier material may be directly infiltrated into the
electrode, especially if the electrode is porous or provided
with holes as in U.S. Patent No. 6,214,204. A preferred

embodiment is to provide a carbon electrode with a secondary
pore structure that is larger than the primary surface area
pores. These large secondary pores may be coated with or
infiltrated with an anion or cation exchange material.

Since the electrodes provide strength, the ion exchange

groups on the charge barrier material may be supported on a
hydrogel, for example polyacrylamide or polysaccharide
material. Suitable ion exchange membrane formulations and
ionic groups may include, for example, perfluorinated films,
NAFIONETM, carboxylate or sulfonate polymers, perfluorinated

sulfonic acid, a mixture of styrene and divinylbenzene,
olefins and polyolefins, or any polymer derivatized with
various ionic groups, including sulfonyl halide, amine,
diamine, aminated polysulfone, carboxyl, sulfate, nitrate,
phosphate, chelating agent, ethylenediaminetetraacetic acid
(EDTA), cyanide, imine, polyethyleneimine, amide,
polysulfone, or any other fixed ionic group may be used as
the charge barrier material. See also, Thomas A. Davis

et al, A First Course In Ion Permeable Membranes (The
Electrochemical Consultancy, Hants, England, 1997).

A particularly preferred embodiment of the present
invention is to combine the charge barrier within the
structure of the electrode. Any electrode material that has

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through holes, or which has a porous structure, may be used.
The porous structure may include a combination of pore
sizes, for example, macropores, micron-sized pores or
larger, combined with meso or micro pores in order to

improve conductivity of ions into the electrode and
accessibility of the surface area. The charge barrier
material may be infiltrated into this pore structure in
order to form a combined electrode-charge barrier material

that may be used as spaced-apart electrodes or with any flow
spacer.

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Fig. 1 shows a generalized drawing of a charge
barrier flow-through capacitor, with electrode 2, charge
barrier 3, spacer 4, and optionally, current collector 1.
An electrode 2 is prepared from a high capacitance
material, preferably with a capacitance of over 1 farad
per gram or 1 farad per cubic centimeter (as measured in
concentrated sulfuric acid). The charge barrier 3 may be
a permselective membrane of either polarity and either
the same polarity as each other or an opposite polarity.
The charge barrier 3 may also be a bipolar membrane. The
charge barrier 3 may also be prepared from an electrode
material with a lower RC time constant than the
underlying electrode 2, and either laminated during
manufacture directly upon and integral to electrode 2, or
simply laid together separately. For the best results,
the electrode material should have an RC time constant
that is at least twice as high as the RC time constant of
the charge barrier 3. In order to improve performance of
the charge barrier 3, the capacitance of the underlying
electrode may be reduced or resistance of the underlying
electrode 2 may be increased relative to the charge
barrier 3 material. Ideally, the electrode 2 RC time
constant may be manipulated by increasing capacitance
more than by increasing resistance, in order to have a
low series resistance, highly energy efficient capacitor.
So that the charge barrier 3 may have a lower RC time
constant than the underlying electrode 2, either
resistance or capacitance of the charge barrier 3 may be
decreased relative to the electrode 2. However, changing
either value will suffice to alter the RC time constant.
During charge of such a laminated electrode 2, with the
lower RC time constant material facing outward to the
flow channel spacer, the outer low RC time constant
electrode 2 charges up first. This creates an inverse
electric field localized within the electrode 2 of the
opposite direction to the electric field between the
anode and cathode electrodes 2. This inverse field holds
pore volume ions trapped within the electrode 2.



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In order to maintain charge neutrality, counterions
migrate into the electrode 2 where they form a
concentrated solution with the trapped coions, thereby
increasing ionic efficiency. Spacer 4 may be prepared
from any material which defines a flow channel, or it may
be simply a space between the anode and cathode pairs of
electrodes 2 that is ionically permeable and electron
insulating, with flow channel 5 defined by the spacer 4,
within the spacer 4, or in the layers between the
spacer 4 and the electrode 2. This flow channel 5 may be
formed by grooves or ribs embossed into either the
spacer 4 or electrode 2. Alternatively, the spacer 4 may
be an open netting, filter, particulate, or screen-
printed material of any geometry that serves to space
apart the electrode 2 layers and allow flow paths S. The
spacer 4 may be a doubled-up layer of material with a
flow path 5 between the layers. It is desirable that the
flow spacer 4 be thin, e.g., under 0.01 inches thick.
Further, it is desirable that doubled-up charge
permselective membranes or membranes and flow spacer
combinations be thin, e.g., under 0.02 inches thick, and
preferably, less than 0.01 inch thick. If the charge
barrier 3 is a permselective membrane, the polarities may
be the same, either negative or positive, or there may be
one of each polarity, i.e., one negative and one
positive. In order to limit series resistance, the
electrodes 2 should also be thin, such as under 0.06 inch
thick, for example, 0.02 inch thick or less. Spacing
between layers should also be thin, such as under 0.06
inch, for example, 0.01 inches or less. It is important
to limit leakage, because this bleeds off the charge
responsible for maintaining a charge barrier.
Leakage resistance of over 100 ohm cm2 is preferred,
such as over 1000 ohm cmZ, and series resistance of under
50 ohm cm2 is preferred, as measured by recording the
instantaneous current upon application of 1 volt to a
cell equilibrated with 0.1 M NaCl. The cm2 in the ohm
cm 2 above refers to the electrode 2 facing area, which is
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the same as the spacer 4 area. The ratio of leakage
resistance to series resistance should be in excess of 100,
such as, for example, in excess of 300.

Electrode 2 materials may be selected for

nonfouling characteristics. For example, activated carbon
tends to absorb organics and many ions passively. Carbon
blacks, which may be selected for use, show less tendency to
adsorb passively a foulant that is causing a problem with
activated carbon electrodes 2. Carbon black may also be

derivatized with fluorine groups in order to make it less
passively adsorptive. However, for treatment of
polyaromatic hydrocarbons, trihalomethane, and other
organics, the passive absorptive behavior may be selected
for in electrode 2. These electrode 2 materials may be

electrochemically destroyed once they are adsorbed
passively. To facilitate passive adsorption, it may be
advantageous to provide flow pores through the current
collector 1 and electrode 2 so that nonionic species may be

exposed to the electrodes 2 by convective flow there
through. Charge barrier 3 material may also be a
permselective membrane, such as a cation, anion, or ion-
specific membrane material.

Flow-through capacitors of the invention may be
electrically connected in series as separate, electrically-
insulated cells. These cells may be built within the same

flat stacked layer or within a spirally-wound layer, flow-
through capacitor. For example, individual cells containing
multiple electrode pairs and other layers may be provided
with an ionically-insulating component on the end of the
electrode 2 stack. This ionically-insulating component may
be electrically conductive so as to form an electrical
series connection from one capacitive layer to the next, on

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opposing sides of this ionically-insulating layer. A number
of cells may be rolled up in concentric spirals in order to
form an electrical series, connected, flow-through capacitor
with parallel fluid flow between the layers. A cell is any
arrangement of layers that includes parallel pairs of

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electrodes 2 with the same voltage. By stacking cells in
series, the voltage is additive across the stack and is
therefore increased in order to take advantage of less
expensive, higher voltage, lower amperage power. For
example, a 480 to 600 volt stack is ideal for use with
power received directly from transmission lines, without
the need for transformers to step down the voltage.
Fig. 2 represents a flow-through capacitor of the
invention incorporating electrode 2 and charge barrier 3.
In this case, the charge barrier 3 either has a lower RC
time constant material than does electrode 2, or the
charge barrier 3 is a permselective membrane of the same
polarity as the adjacent electrode 2. Upon applying
voltage, anions and cations are expelled from the anodes
and cathodes, respectively. The ion movement is shown
in Fig. 2 by the horizontal or bent arrows. These ions
are repelled by and trapped, against charge barrier 3,
which, if made from a low RC time constant material, has
like polarities in the form of electric charges, or, in
the case of a permselective membrane, has like polarities
in the form of bound charges to that of the adjacent
electrode 2. Ions from the flow channel 5, e.g., a
central flow channel, migrate through the permselective
membrane to balance the charge of these trapped ions. As
a result, a concentrated solution of ions forms in the
compartments surrounding electrode 2. Ions are depleted
from the flow channel 5, allowing purified water to exit
the flow channel 5. Counterions already present in the
pore volume electrostatically adsorb on their respective
electrodes 2. Although, this takes up an adsorption
site, the concentrated solution formed by the trapped
ions and by the charge-balancing ions make up for any
loss of adsorption capacity.
In essence, the charge barrier 3 forms an inverse
electric field which keeps coions inside the electrode 2.
In order to balance charge, counterions migrate into the
electrode chamber where they form a concentrated
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solution, thereby, allowing a flow-through capacitor of
improved ionic efficiency, e.g., such as 30 to 99%.
Fig. 3 represents the flow-through capacitor of
Fig. 2 after it is discharged. Desorbed ions, together
with ions that had concentrated in the electrodes 2, are
discharged as a concentrate. A flow channel 5 may be
formed from a spacer component (not shown). Spacer 4 may
be formed from flow patterns directly embossed into the
electrode 2 or from a separate flow channel 5 forming
spacer 4 (shown in Fig. 1), such as, without limitation,
an open netting material, screen-printed protrusions or
ribs, or a nonwoven filter material.
Spacer 4 may be incorporated into one or more flow
channels S. Flow channel 5 may exist as two types, i.e.,
between the charge barrier 3 layers or between the
electrodes 2 and charge barriers 3, or both types of flow
channels 5 may exist at the same time, with each type
isolated from the other type. Two simultaneous types of
flow channels 5 allow for simultaneous purification and
concentration.
Fig. 4 represents a flow-through capacitor with a
double permselective membrane adjacent to the
electrode 2, whereby the adjacent membranes are of
opposite polarity to the electrode 2. This may be
accomplished electronically, merely by reversing the
polarity of the capacitor in Fig. 2, for example, if
operating the capacitor with alternating polarity charge
cycles. In the capacitor of Fig. 4, ions concentrate
into the space between the membranes during application
of a voltage. Flow channels 5 may be incorporated
centrally, or two-sided, or both side and central. A
concentrate is released from the central flow channel 5
during application of a voltage. If the side and central
flow channels 5 are isolated by a gasket or sealing
agent, then purified water may be retrieved from the side
flow channels 5 at the same time that concentrated water
is retrieved from the central flow channel 5.

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In Fig. 5, purified water is collected from the
central flow channel 5. This mechanism is due to the
fact that the discharging capacitor of Fig. 4, with
opposite- charged permselective membranes adjacent to the
electrodes 2, is analogous to the charging capacitor of
Fig. 2, with like-charged permselective electrodes 2
adjacent to the electrodes 2. When the capacitor of
Fig. 4 is discharged, an interesting observation may be
made, discharging counterions become trapped between the
electrode 2 and the membranes, where they draw ions from
the central channel into the side channels in order to
maintain electroneutrality. If isolated side flow
channels 5 were also provided, concentrated fluid may
simultaneously be retrieved.
By incorporating a separate flow channel 5 shown in
Figs. 2 and 4, the flow-through capacitor purifies and
concentrates simultaneously. The flow-through capacitor
of the invention may also have a central flow channel 5
composed of opposite or like-polarity permselective
membranes. In the case of opposite-polarity membranes,
the flow-through capacitor may be cycled with
alternating-charge polarities. This situation is
represented by the charge polarity shown in Fig. 4,
followed by the discharge cycle shown in Fig. 5, followed
by the polarity shown in Fig. 2 (the reverse of Fig. 4),
followed by a discharge cycle. This situation creates
two purification cycles in a row, followed by two
concentration cycles in a row. Therefore, the flow-
through capacitor of the invention may extend
artificially the length of time the cell spends
purifying. Depending upon the orientation of the
membranes, purification or concentration can occur either
upon a voltage rise or a voltage decrease. This differs
markedly from flow-through capacitors of the prior art,
which exhibit purification upon application of voltage
of either polarity, as opposed to a change in voltage,
for example, from negative towards zero.



CA 02444390 2003-10-15
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Fig. 6 shows a stacked-layer capacitor of the
invention. Material layers are arranged around a central
flow hole 8. Material layers may be discs, squares, or
polygons consisting of electrodes 2, charge barriers 3
materials (either lower RC time constant electrode 2
material or permselective membranes of the same or
opposite polarities). Optionally, spacer 4 forms a
central flow path 8. The spacer 4 may be prepared from,
for example, any open netting, nonwoven cloth, loosely
applied particle material, screen-printed protrusions, or
ribs.
Fig. 7 shows a layer capacitor of the invention
modified so as to allow multiple flow paths S. Charge
barriers 3 are prepared with permselective membranes.
Permselective membrane 3 are sealed to electrode 2 in
order to form two alternating flow paths. One flow
path 24 flows between pairs of permselective membranes
and out flow holes 26. The other flow path 25 flows
between electrode 2 and one charge barrier 3, and then
out through separate flow holes 27. This capacitor has
two discrete outlets formed by the seals 9 but does not
require inlets to be separately sealed. Optionally, the
inlets may be separately sealed in order to allow
backwashing. The seal 9 may be accomplished by using,
for example, a washer, gasket, glue, or resin material
that seals layers together. Optionally, the electrode 2
may have an enlarged central hole 10 so that a seal need
only be made between two charge barriers 3, rather than
between a charge barrier 3 and an electrode 2. The
layers of charge barriers 3 and electrodes 2 may be
repeated within a particular cell any number of times.
Typically, where the electrode 2 is an end electrode, it
may be single-sided; whereas, where the electrode 2 is
internal, it may be double-sided, such as on either side
of a current collector 1 within the same cell.
Figs. 8A, 8B, 8C and 8D represent a flow-through
capacitor of the invention comprised of parallel
rectangular layers of electrodes 2, a spacer 4, e.g., a
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flow spacer to allow an electronically-insulated flow
channel 5, located between an electrode 2 and a seal 9,
e.g., a gasket seal to form two sets of isolated,
manifolded flow channels S. The charge barrier 3 may
function as, or together with, the seal 9 gasket. A flow
slot 10 may be cut into one end of charge barrier 3.
This forms a manifold flow channel 23 between two layers
of charge barrier 3. A spacer 4, shown in the inset,
may be placed between the charge barrier layers 3 in
order to form a flow channel S. Containment plate 11 is
part of a cartridge holder that holds the entire flow-
through capacitor cartridge formed of the layers of
charge barrier 3. A second set of flow channels 5,
transverse to the above flow channels 5, is formed
between electrode 2 and charge barrier 3. These flow
channels 5 may be formed from another set of spacers (not
shown) located in this space or may be formed from a
textured pattern embossed directly into either the
electrode 2 or charge barrier 3. A flow channel 5 may be
formed from a netting, a ribbed particulate, a
microprotrusion, or a diamond-shaped pattern, e.g., a
protruding or embossed pattern to form a flow channel 5.
Any of the layers may contain a flow channel 5 or may be
textured, or have openings, pores, or spacers to form a
flow channel 5. The flow pattern may, for example,
consist of 0.001 inch deep grooves in a pattern of 0.005
inch diamonds embossed in a 0.01 inch thick electrode 2.
These transverse flow channels 5 are likewise manifolded
together into common inlets and outlets. In this way,
simultaneously-concentrated and purified fluid streams
may be fed into or collected from the flow-through
capacitor.
Fig. 9 shows a graph of the data obtained from a
capacitor charged in the sequence demonstrated by
charging as shown in Fig. 2, discharging as shown in
Fig. 3, with the polarity of electrode 2 set so as to
charge as shown in Fig. 4, and followed by discharging as
in Fig. 5. Note how in this case, purification occurs
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upon a voltage rise, and concentration occurs upon a
voltage decrease.
Fig. 10 represents an arrangement of layers of
charge barriers 3 in the flow-through capacitor of the
invention where the charge barrier 3 is a conductive
material having a lower RC time constant than the
electrode 2. The ratio of RC time constants of charge
barrier 3 to electrode 2 should be more than a factor of
two, and preferably, more than 4, such as, for example,
10.
Electrode 2 is connected by lead 12 to DC power
source 13. The lead 12 may be integral with the
electrode 2 or may be attached to a separate current
collector layer (not shown), in which case the
electrode 2 may be on both sides of the current
collector. A spacer 4, such as an ionically-conductive,
electrically-insulating spacer or a flow spacer separates
the electrode 2 from the conductive, low RC time constant
charge barrier 3. A separate power source 14 connects
through its lead 12 to the charge barrier 3 in order to
charge the charge barrier 3 to a higher, varying, or
constant voltage than the underlying electrode 2. By
"underlying" is meant in the direction of migration of
cation 6 and anion 7. The anion 7 is held inside the
chamber containing left, negative electrode 2 and
spacer 4. This causes a cation 6 to migrate through the
charge barrier layer 3, where it forms a concentrated
solution in conjunction with anion 7. The opposite
occurs on the other side of the flow-through capacitor.
Fig. 11 represents a stack of flow-through
capacitors 15 with separate purification and
concentration streams. Flow-through capacitors 15 are
fluidly and electrically connected with leads 12 in
series. The DC power source 13 provides the voltage and
selected constant or variable current to the capacitor 15
stack. The controller, logic, and switching
instrument 20 provides alternating-polarity charge cycles
and discharge cycles. Conductivity controller 22
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monitors the outlet fluid concentration of purification
stream 18 to provide data with which to operate logic
instrument 20, and valve component 16, which switch fluid
streams in order to separate waste stream 17 and

purification stream 18. Optionally, the hold-up tank 21
regulates the flow in case purification stream 18 is
variable or intermittent. Optionally, a component 19 may be
placed upstream of the capacitors 15 to pretreat the water.
A component 19, may be any technology known to treat water,

for example, a component for reverse osmosis, micro or ultra
filtration, carbon filtration, flocculation, electrowinning,
or addition of chemicals. For example, it may be desirable
to add chemicals that will presterilize the water, which
chemicals may be further reduced or oxidized to a salt form

by further chemical addition, then removed later in their
salt form from the flow-through capacitor 15. A
pretreatment component 19 may also be used for a post
treatment, by placing it downstream of the flow-through
capacitor in the outlet purification stream 18.

The flow-through capacitors of the invention may
be utilized in any system configuration common to ion
exchange, electrodialysis, or reverse osmosis, or flow-
through capacitors, including bleed and feed, batch, or
continuous processes.

Examples
Example 1

The flow-through capacitor of Fig. 10 is prepared
using electrodes composed of 95% carbon black and 5% of a
polymer PTFE or similar polymer. Charge barriers are

composed of permselective membranes. In the capacitor of
Fig. 10, a cation exchange membrane, such as RaiporeTM 1010
19


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membrane with fixed benzyl sulfonic acid groups, is placed
touching and adjacent to the negative electrode. An anion
exchange membrane, in this case, a RaiporeTM 1030 membrane
with fixed phenyl tetramethyl ammonium groups, is placed

touching and adjacent to the positive electrode. A 0.003
inch thick filtration netting is placed between the two
oppositely-charged permselective membranes and to form the
flow path. The capacitor is charged at constant current, up
to a voltage limit of 1 volt. Seawater flowing between the

membranes is purified to 12%. In order to reach a purity of
99%, several capacitors are used in series or stages with
series flow to reduce the salinity to 6000 ppm. An
additional flow-through capacitor, e.g., a reverse osmosis
series stage may be used to further reduce the remaining

salinity to 250 ppm.
Example 2

The flow-through capacitor of Example 1 is used at
a flow rate of less than 1 ml/minute/gram of carbon, for
example, 0.1 ml/minute/gram of carbon, to achieve greater

than 90% purification of a 35,000 ppm salt solution.
Example 3

The flow-through capacitor of Example 1 is coupled
through an inductor in order to recover energy during
discharge. This energy is used to charge a second capacitor

during its purification cycle. Maximum charging voltage of
both capacitors is kept below 0.7 volts, in order to
minimize energy usage. Capacitors may be charged either at
constant voltage, constant current, or at constantly
increasing voltage, or constantly increasing current.
Optionally, capacitors may be charged in series in order to


CA 02444390 2006-06-29
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increase the voltage for maximum energy recovery and power
supply efficiency.

Example 4

The flow-through capacitor of Fig. il is made by
using activated carbon black as the electrodes. A low RC
time constant material, such as carbon fibers, nanotube
mesh, or low capacitance activated carbon cloth aerogel is
used as a charge barrier material. Water with 5000 ppm
minerals and salts is passed through this device at a flow

rate of less than 20 ml/minute per gram of carbon, with the
flow rate adjusted downwards in order to achieve 95%
purification. The flow rate may be further decreased into
the charge cycle in order to maintain the desired

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level of purification for a longer period of time. Once
the level of purification drops below 80%, the capacitor
is discharged through an energy-recovery circuit. That
energy is added to the energy from the DC power source
and used to charge another capacitor which purifies while
the first capacitor is releasing a concentrated stream of
contaminants.
Example 5
The flow-through capacitor of Example 4 may be
powered by a fuel cell.
Example 6
A flow-through capacitor is made utilizing low
surface area carbon black, in the range between 300 and
900 Brunauer Emmett Teller method (BET), selected for
being less likely to passively adsorb contaminants and
therefore foul the flow path. The charge barrier
materials are NEOSEPTA . The flow arrangement is a dual-
flow channel device as shown in Figs. 7 and 8A, 8B, 8C,
and 8D. One flow channel is formed between and by
spacing apart the two charge barrier materials. A pair
of side flow channels is located on either side of the
central flow channel. These side flow channels are also
formed by placing a spacer between the electrodes and the
charge barrier materials. A membrane that selectively
allows anions to migrate through it (anion permselective,
because it has bound positively-charged ionic groups), is
initially placed on the side of the negative electrode,
with a flow spacer in between. The membrane that
selectively allows cations to migrate through it (cation
permselective, because it has bound negatively-charged
ionic groups). During this charge cycle, purified water
is retrieved from the outlet of the central flow channel.
Simultaneously, concentrated water is retrieved from the
electrode facing side flow channels.
The same flow-through capacitor may subsequently be
discharged. A concentrated solution is recovered from
the central flow channel. The capacitor may be
repeatedly run in this polarity sequence. Alternatively,
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the polarity may be reversed. Reversing the polarity
places the permselective membranes adjacent to the
oppositely-charged electrodes. This means that a
concentrated stream is recovered during the charge cycle
from the central flow channel. Simultaneously, a
purified stream may be recovered from the side flow
channels. Subsequently, the flow-through capacitor may
be discharged. During the discharge cycle,, a purified
liquid is recovered from the central flow stream, and a
concentrated liquid is recovered from the side flow
channels.

Example 7
A flow-through capacitor is made utilizing one
micron small particle size activated carbon powder
electrodes bound together with 5% PTFE binder. The
charge barrier material is a conductive polymer coating
0.001 inch thick. Ten of the charge barriers are
connected in a 7-volt series bank of capacitors.
Seawater of 35,000 ppm is treated to 500 ppm at an energy
usage of 0.7 joules per coulomb. 70% of the energy is
recovered during discharge of the capacitors using
inductive coils to recharge a second bank of capacitors
in series.
Example 8
In a flow-through capacitor using edge plane
graphite with a surface area of 500 square meters per
gram for electrodes, an anion and a cation exchange
membrane are used as charge barriers. An additional pair
of bipolar membranes is placed between the cation or
anion membranes and the electrodes. Flow spacers are
placed between all the above layers, or merely between
the cation and anion exchange membranes. The resulting
cell may be used in any application of bipolar membrane
electrodialysis, but without oxidation reduction
reactions at the electrodes, for example, recovery of
organic acids, proteins, or biological molecules from
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fermentation broths. Another application is the recovery
of SO2 or NO3 from stack gas.
Example 9
A flow-through capacitor is made using an electrode
composed of a high-capacitance electrode material, such
as high-surface-area carbon cloth, or edge plane
graphite, or carbon black particles bound together with
fibrillated PTFE. Membranes selective for transmigration
of cations and anions, respectively, are placed touching
the electrodes. A central flow channel is formed by any
spacing component, including biplanar filtration netting
under 0.01 inches thick, screen-printed protrusions or
ribs, or membranes textured with premanufactured flow
channels in a diamond pattern. The initial charge
sequence is at constant current selected for low I
squared R energy losses, where "I" is amps and "R" is
electrical series resistance. A top charging voltage of
0.6 volts is selected to minimize the amount of energy
required to purify a given amount of ions. The charge
cycles are carried out as follows:

During the first charge cycle, the electrodes are
of the same polarity as the fixed charge inside the
membranes. Coions expelled from the pore volume of the
electrodes are trapped against the membranes. This
causes an amount of counterions in the central flow
channel to migrate through the membranes, where they form
a concentrated solution in the electrode layer. This
counteracts the losses ordinarily caused by adsorption
and expulsion of dissolved pore volume salts. Therefore,
the ionic efficiency, as measured by coulombs of ionic
charge purified divided by coulombs of electronic charge
utilized, is greater than 30%. In this case, for 35,000
ppm salts, ionic efficiency is 85%, and the energy
utilized is 0.35 joules per coulomb of charge.
The next cycle is a discharge cycle in which
concentrated waste is released into a feed stream fed
into the central flow channel and recovered from the
23


CA 02444390 2006-06-29
30309-16

outlet. The next cycle, after discharge, is a reverse
polarity charge. Here, the bound charge on the membranes is
opposite to the electronic charge on the electrodes. Ions
are driven from the electrode across to the adjacent

membrane, but cannot migrate through the second membrane.
Therefore, a concentrated solution forms in the central flow
channel and is released through the outlet. Upon discharge
from this polarity, ions migrate from the central flow

channel back into the electrode chambers, thereby purifying
the feed stream. The subsequent cycle goes back to the
beginning. These cycles can be repeated as many times as
desired. An example of data from the above is shown in
Fig. 9. Fig. 9 shows the underlying usefulness of the
charge cycle in Example 7. Note that two purification

cycles occur in a row. Likewise, two concentration cycles
occur in a row. This doubling up of purification or
concentration artificially extends the length of time the
capacitor is performing a particular purification or
concentration cycle.

Example 10

The flow-through capacitor of Fig. 11 is used to
make ultrapure water of, e.g., 18 megaohms cm. The water
may be pretreated using one or more of a microfilitration
unit, a water softener, and followed by a reverse osmosis
unit. The water may be post treated using, e.g., a
polishing bed of deionization resin. The flow-through
capacitor removes some or all of the dissolved solids from
the deionization bed, thereby prolonging the lifetime of the
deionization bed.

24


CA 02444390 2006-06-29
30309-16

Example 11

The flow-through capacitor of Fig. 11 may be used
to post-treat seawater which has been previously treated by
reverse osmosis. The salinity of the seawater is initially

reduced by reverse osmosis from 35,000 ppm to 10,000 ppm.
Subsequently, treatment with the flow-through capacitor
further reduced the salt concentration to 250 ppm. The
combined use of reverse osmosis and the flow-through
capacitor desalinated seawater for 15 kw

24a


CA 02444390 2003-10-15
WO 02/086195 PCT/US01/12641
hours per thousand gallons, which is a 30% energy savings
compared to using reverse osmosis alone.
Example 12
The flow-through capacitor of the invention may be
used to purify seawater to 500 ppm.
Example 13
Individual flow-through capacitor cells are made
with the following sequence of layers: current collector
layers, such as using 0.005 inch thick graphite foil; an
electrode layer of any capacitance material, for example,
carbon microparticle containing sheet material; a pair of
charge barrier layers consisting of carbon cloth or of an
anion and a cation exchange membrane bracketing a central
flow netting spacer of .005 inch thick polypropylene; a
second electrode layer needed to form a pair; and a
second current collector layer. The current collectors
are ionically insulating but electronically conductive.
Therefore, if a number n of the above sequence of layers
are stacked up as flat sheets, or rolled in concentric
spirals, they will form a series-connected, flow-through
capacitor with single-sided capacitive electrodes facing
outwardly from the current collector. The current
collector forms the ionically-nonconductive boundary
between cells and establishes an electrical series
connection. If the electrode is conductive enough not to
require a current collector, then a thin sheet of plastic
may be used as long as series leads are connected between
cells. The electrode does not need to be single-sided.
Any number of double-sided electrodes connected
electrically in parallel may exist within particular
cells. Each cell may be made with the same capacitance
by matching the construction of each cell. Flow in the
spiral cell may be alongside the layers.
Example 14
Activated carbon particles in the 0.2 to 5 micron
diameter range, conductive ceramic, aerogel, carbon
black, carbon fibers, or nanotubes with a BET of between
300 and 2000, are mixed together with 5% PTFE binder, ion


CA 02444390 2006-06-29
30309-16

exchange resins as a charge barrier, and
carboxymethylcellulose as a plasticizer, and calendered into
a 0.01 thick sheet. These are made separately in anion,
cation, and bipolar versions. Any ion exchange resin known

to be used in ion exchange or electrodialysis membranes may
be used. Ion exchange groups include any strong or weak
acid or base, for example, sulfonic acid or amine groups.
Ionic group support material includes any material used in
ion exchange or membranes, including fluorinated polymers,

divinylbenzene, or styrene polymers, or any other kind of
polymer, zeolite, or ceramic material. The geometry of
construction will be known to those of skill in the art,
including, but not limited to those described in the U.S.
Patent Nos. 5,192,432, 5,415,768, 5,538,611, 5,547,581,

5,620,597, 5,748,437, 5,779,891, and 6,127,474. The
electrodes may be spaced apart or provided with a flow
spacer and an optional current collector in order to form a
charge barrier flow-through capacitor. The advantage of
this example is that the charge barrier material is evenly

distributed throughout the electrode layers, thereby
eliminating extra charge barrier layers, the cost due to
these extra parts, and allowing the electrodes to be spaced
closer together, less than 0.02 inches, for example, which
cuts resistance and increases flow rate of purification.
Monolithic or sintered carbon electrodes may also be used,
for example, electrodes with honeycomb holes incorporated
into the structure may have these holes filled in with ion
exchange resin to effect a combined charge barrier electrode
material.

26

A single figure which represents the drawing illustrating the invention.

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Admin Status

Title Date
Forecasted Issue Date 2007-07-03
(86) PCT Filing Date 2001-04-18
(87) PCT Publication Date 2002-10-31
(85) National Entry 2003-10-15
Examination Requested 2003-10-15
(45) Issued 2007-07-03

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Request for Examination $400.00 2003-10-15
Application Fee $300.00 2003-10-15
Maintenance Fee - Application - New Act 2 2003-04-22 $100.00 2003-10-15
Maintenance Fee - Application - New Act 3 2004-04-19 $100.00 2004-04-16
Maintenance Fee - Application - New Act 4 2005-04-18 $100.00 2005-04-06
Registration of a document - section 124 $100.00 2006-02-08
Maintenance Fee - Application - New Act 5 2006-04-18 $200.00 2006-04-18
Maintenance Fee - Application - New Act 6 2007-04-18 $200.00 2007-04-05
Final Fee $300.00 2007-04-20
Maintenance Fee - Patent - New Act 7 2008-04-18 $200.00 2008-04-15
Maintenance Fee - Patent - New Act 8 2009-04-20 $400.00 2009-04-30
Maintenance Fee - Patent - New Act 9 2010-04-19 $200.00 2010-03-16
Maintenance Fee - Patent - New Act 10 2011-04-18 $250.00 2011-03-09
Maintenance Fee - Patent - New Act 11 2012-04-18 $250.00 2012-03-07
Maintenance Fee - Patent - New Act 12 2013-04-18 $250.00 2013-03-06
Maintenance Fee - Patent - New Act 13 2014-04-22 $250.00 2014-03-06
Maintenance Fee - Patent - New Act 14 2015-04-20 $250.00 2015-03-12
Maintenance Fee - Patent - New Act 15 2016-04-18 $450.00 2016-03-23
Maintenance Fee - Patent - New Act 16 2017-04-18 $450.00 2017-03-31
Maintenance Fee - Patent - New Act 17 2018-04-18 $450.00 2018-03-12
Maintenance Fee - Patent - New Act 18 2019-04-18 $450.00 2019-03-26
Maintenance Fee - Patent - New Act 19 2020-04-20 $450.00 2020-04-17
Registration of a document - section 124 2020-07-23 $100.00 2020-07-23
Current owners on record shown in alphabetical order.
Current Owners on Record
VOLTEA, INC.
Past owners on record shown in alphabetical order.
Past Owners on Record
ANDELMAN, MARC D.
BIOSOURCE, INC.
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Description
Date
(yyyy-mm-dd)
Number of pages Size of Image (KB)
Claims 2003-10-15 2 81
Abstract 2003-10-15 1 61
Drawings 2003-10-15 11 144
Description 2003-10-15 26 1,257
Representative Drawing 2003-10-15 1 33
Cover Page 2004-01-20 1 45
Claims 2006-06-01 10 281
Description 2006-06-01 35 1,298
Claims 2006-06-29 10 314
Description 2006-06-29 35 1,360
Claims 2006-09-22 10 311
Representative Drawing 2007-06-20 1 17
Cover Page 2007-06-20 1 48
PCT 2003-10-15 10 418
Assignment 2003-10-15 2 80
Fees 2004-04-16 1 36
Fees 2010-03-16 1 35
Fees 2005-04-06 1 37
Prosecution-Amendment 2005-12-01 6 257
Assignment 2006-02-08 4 133
Fees 2006-04-18 1 36
Prosecution-Amendment 2006-06-01 42 1,283
Prosecution-Amendment 2006-06-29 33 1,035
Prosecution-Amendment 2006-08-16 2 52
Prosecution-Amendment 2006-09-22 6 216
Correspondence 2007-04-20 1 39
Fees 2007-04-05 1 34
Fees 2008-04-15 1 28
Fees 2009-04-30 2 60
Fees 2013-03-06 1 67
Fees 2014-03-06 2 87
Fees 2015-03-12 2 84
Fees 2016-03-23 2 86
Fees 2017-03-31 2 83
Fees 2018-03-12 1 61
Fees 2020-04-17 6 156
Assignment 2020-07-23 11 784
Correspondence 2020-07-23 3 76
Assignment 2021-04-30 6 180
Correspondence 2021-04-30 3 64