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WO2009065023A1 - Systèmes multifonctionnels de filtration et de purification d'eau - Google Patents

Systèmes multifonctionnels de filtration et de purification d'eau Download PDF

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Publication number
WO2009065023A1
WO2009065023A1 PCT/US2008/083615 US2008083615W WO2009065023A1 WO 2009065023 A1 WO2009065023 A1 WO 2009065023A1 US 2008083615 W US2008083615 W US 2008083615W WO 2009065023 A1 WO2009065023 A1 WO 2009065023A1
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WIPO (PCT)
Prior art keywords
electrode
accordance
water
purification system
water purification
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2008/083615
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English (en)
Inventor
Qinbai Fan
Jeremy R. Chervinko
Siem Le
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Quos Inc
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Quos Inc
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Publication date
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Publication of WO2009065023A1 publication Critical patent/WO2009065023A1/fr
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/4604—Treatment of water, waste water, or sewage by electrochemical methods for desalination of seawater or brackish water
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46119—Cleaning the electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46133—Electrodes characterised by the material
    • C02F2001/46138—Electrodes comprising a substrate and a coating
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46152—Electrodes characterised by the shape or form
    • C02F2001/46157—Perforated or foraminous electrodes
    • C02F2001/46161—Porous electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08—Seawater, e.g. for desalination
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2201/00—Apparatus for treatment of water, waste water or sewage
    • C02F2201/46—Apparatus for electrochemical processes
    • C02F2201/461—Electrolysis apparatus
    • C02F2201/46105—Details relating to the electrolytic devices
    • C02F2201/46115—Electrolytic cell with membranes or diaphragms
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2201/00—Apparatus for treatment of water, waste water or sewage
    • C02F2201/46—Apparatus for electrochemical processes
    • C02F2201/461—Electrolysis apparatus
    • C02F2201/46105—Details relating to the electrolytic devices
    • C02F2201/4612—Controlling or monitoring
    • C02F2201/46145—Fluid flow

Definitions

  • This invention relates to an apparatus for water purification. More particularly, this invention relates to a multi-functional apparatus for water purification having the functionalities of ion-exchange, carbon adsorption, electrochemical ionic adsorption and desorption, and microfiltration.
  • the apparatus is capable of removing ionized and non- ionized organic compounds, inorganic ions, particulates and bacteria from wastewater streams in a single unit to produce potable water.
  • Porous carbon-based electrodes with polymer binders function as impurity filters to remove particulate matter, such as ash, sand and high molecular weight compounds, as electrodes to concentrate and remove ionic species, and as adsorbents to remove organic materials and bacteria from the wastewater stream.
  • Known water purification methods include distillation, ion-exchange, carbon adsorption, filtration, ultrafiltration, reverse osmosis, electrodeionization, capacitive deionization, ultraviolet radiation, and combinations thereof.
  • Distillation cannot remove some volatile organics and it consumes large amounts of energy.
  • ion-exchange processes water is percolated through bead-like spherical resin materials. However, the resin materials need to be regenerated and changed frequently.
  • this method does not effectively remove particles, pyrogens, or bacteria.
  • Carbon adsorption processes can remove dissolved organics and chlorine with long life and high capacity; however, fine carbon particles are generated during the process due to corrosion.
  • Micropore membrane filtration removes all particles and microorganisms greater than the pore size of the membrane; however, it cannot remove dissolved inorganics, pyrogens or colloids.
  • the ultrafilter is a tough, thin, selectively permeable membrane that retains most macromolecules above a certain size, including colloids, microorganisms, and pyrogens; however, it will not remove dissolved organics.
  • Reverse osmosis is the most economical method for removing 90 to 99% of all contaminants. Reverse osmosis membranes are capable of rejecting all particles, bacteria, and organics; however, the flow rate and productivity are low. Electrodeionization, which is the subject matter of U.S.
  • Patent 6,824,662 B2 to Liang et al. is a combination of electrodialysis and ion-exchange, resulting in a process which effectively deionizes water while the ion- exchange resins are continuously regenerated by the electric current; however, this method requires pre-purification to remove powders and ash materials. Ultraviolet radiation cannot remove ionized inorganics.
  • Fig. 1 is a diagram showing a capacitive deionization process with carbon aerogel electrodes.
  • salt water is introduced into the cell, the negative electrode (anode) 11 adsorbs positive ions 13 and the positive electrode (cathode) 12 adsorbs negative ions 14.
  • the negative electrode (anode) 11 adsorbs positive ions 13
  • the positive electrode (cathode) 12 adsorbs negative ions 14.
  • the cell is charged, pure water is obtained, and when the cell is discharged, concentrated salt water is removed.
  • pulsed electrical power at voltages from 1.2V to OV is used for different time periods depending on the concentration of the salt water and the activity of the activated carbon.
  • the more accessible surface area the electrode the more ions that can be stored.
  • the main problem with this method is that the electrosorption capacity (salt removal) decreases with cycle life.
  • the invention provides an apparatus for wastewater purification which removes ionized and non-ionized organic materials, inorganic ions, particulates and bacteria in a single unit process.
  • an apparatus for water purification comprising a multi-functional, porous, carbon-based composite electrode comprising a resin (e.g. ion-exchange resin) as a binder, carbon black and/or graphite as active adsorbents, and metal oxides as adsorbent promoters.
  • the porous carbon-based plates may be molded by mixing metal oxides, carbon and/or graphite powders, polymer resin and a bubbling agent, such as ammonium bicarbonate.
  • the resins may be cross-linked for stability and the porosity of the resulting electrode plate may be more than about 50%, for example, about 50% to about 80%, by volume.
  • electrodes for use in water purification which function as electrical field suppliers, ion-exchange resin holders, and colloid powders filters.
  • the positive electrode absorbs negative ions while the negative electrode adsorbs positive ions.
  • electrodes for use in water purification, comprising cellulose or cellulose derivative (e.g., cellulose acetate, cellulose triacetate, hydroxypropyl cellulose, methylcellulose, and cellulose benzoate).
  • the cellulose may be deposited onto the electrode surfaces (e.g., via chemical cross-linking) and/or dispersed within the electrode (e.g., an emulsion which is retained within the electrode by a polymer layer or coating on the electrode surface).
  • an apparatus for water purification comprising a porous anode electrode, a porous cathode electrode, and an electrically non-conductive, fluid permeable separator element disposed between the anode electrode and the cathode electrode.
  • Each of the electrodes comprises graphite, at least one metal oxide, and an ion-exchange, cross-linked, polarizable polymer.
  • One or more of the electrodes may comprise cellulose or a cellulose derivative.
  • the electrodes and separator element are preferably disposed in an electrically nonconductive housing having a wastewater inlet opening and a purified water outlet opening and may be used in a single cell configuration or in a series configuration with additional cell units.
  • the apparatus of this invention may act as a filter, organic and bacteria adsorbent, and also as a desalination system.
  • the apparatus may also be used to concentrate soluble salts from a dilute aqueous solution.
  • One application for the water purification system of this invention may be marine water desalination.
  • a method of removing impurities in water comprising the steps of: applying a voltage to the electrodes of the water purification system described herein; contacting said electrodes with water, whereby impurities in said water are removed by one of said electrodes; and collecting said water from said electrodes.
  • Fig. 1 depicts a conventional capacitive deionization method.
  • FIG. 2 is a schematic diagram showing a single cell compartment for wastewater treatment in accordance with one embodiment of this invention.
  • FIG. 3 is a schematic diagram showing a multi-cell compartment for wastewater treatment in accordance with one embodiment of this invention.
  • FIG. 4 is a schematic diagram showing a two-stage water purification system in accordance with one embodiment of this invention.
  • Fig. 5 schematically depicts microchannels in the porous electrode, as described in Example 8.
  • FIG. 6A is a schematic diagram of a water purification system in accordance with one embodiment of this invention.
  • Fig. 6B schematically depicts voltage changes with electrode couples in series, as shown in the system depicted in Fig. 6A.
  • Fig. 7 schematically depicts a water purification system in which solenoid valves are used for discharge of particulate impurities from the water stream.
  • Fig. 8 is a schematic diagram of a water purification system in accordance with one embodiment of this invention.
  • Fig. 9 is a schematic diagram of an automated water purification apparatus containing the water purification system shown in Fig. 8.
  • Fig. 10 exemplifies an electrode stack in accordance with one embodiment of this invention.
  • Fig. 1 IA depicts a current collector in accordance with one embodiment of this invention.
  • Fig. HB schematically depicts a four-electrode stack in accordance with one embodiment of this invention.
  • Fig. HC depicts a four-electrode stack in accordance with another embodiment of this invention.
  • Fig. 12 schematically depicts assembly of an electrode in the housing of a water purification device as described herein.
  • Fig. 13 shows water permeability as a function of water pressure in a pressure- driven water filtration device.
  • Fig. 14 shows water conductivity as a function of time when ferric nitrate is filtered in a pressure-driven water filtration device.
  • Fig. 15 shows percent salt removal as a function of operating time as described in Example 9.
  • Fig. 16 shows percent salt removal as a function of operating time as described in Example 9.
  • Fig. 17 depicts an electrode comprising a cellulose layer in accordance with one embodiment of the present invention.
  • Fig. 18 shows percent salt removal as a function of the number of operating cycles for an electrode stack as described herein.
  • Fig. 19 depicts a cross-linking reaction of cellulose acetate and formamide.
  • Fig. 20 shows the increased salt removal for a water purification system comprising an expanded graphite electrode compared to a system comprising standard graphite.
  • Fig. 21 shows the comparison of salt removal for a water purification system under varying purge times.
  • Fig. 22 shows percent salt removal as a function of the number of operating cycles for a electrode stack as described herein.
  • the invention provides methods and systems for water purification.
  • Methods and systems described herein are capable of purifying most water streams requiring purification, including but not limited to industrial wastewater, gas and oil field wastewater, and coal mine wastewater, and are well-suited for desalination of salt water.
  • Methods and systems described herein may also be used for purification of drinking water (e.g., removal of ions such as sodium, magnesium, calcium, zinc, and/or lead cations, and/or chloride, sulfate, and/or bromide anions from tap water) and/or purification of industrial waste streams.
  • the system may incorporate electrochemical deionization, microfiltration, carbon adsorption, and ion exchange features to remove organic materials, inorganic materials, bacteria and solid particles.
  • the system may include automated purging of filtered material and particulate buildup for improved efficiency and long term use.
  • the system is often compact, energy efficient, and cost efficient to produce and operate.
  • the invention in one instance provides a water purification system comprising at least two porous carbon-based electrodes, i.e., a porous anode electrode and a porous cathode electrode, with a non-conductive, fluid permeable separator between the two electrodes to prevent excess current flow between the electrodes.
  • the porous electrodes may comprise a carbon-based material (e.g., graphite) for conductivity, at least one oxide (e.g., metal or semi- metal oxide), which may increase water adsorption by the electrode, and at least one resin (e.g., ion-exchange, cross-linked, and/or polarizable polymer) which binds the components of the electrode together and may provide ion-exchange sites for binding ionic compounds in the water stream.
  • the electrodes also comprise one, two, or more elements from Group-14 (e.g., carbon black), carbon fibers, and/or silica.
  • the porous carbon-based electrodes filter particulate matter that is too large to traverse the pores, electrochemically concentrate and sequester ionic species such as inorganic, e.g., metal, ions and ionized organic compounds, and adsorb non-ionized organic materials and bacteria from a water stream.
  • the ion-exchange polymer component of the electrode may also bind ionized compounds in the water stream.
  • the porous electrodes may optionally comprise one or more skin-like layers of polymer binders, which may aid in filtering fine particles.
  • the electrodes contain microchannels through the electrode, covered by a thin layer membrane of the cross-linked polymer at the ends of the microchannels that open to the surface of the electrode or in the interior of the channels.
  • the electrode comprises front and back surfaces
  • the microchannels comprise openings at the front and back electrode surfaces
  • the electrode comprises a thin layer polymeric membrane covering the microchannel openings on the front and back surfaces of the electrode.
  • the thin layer polymeric membranes may act as microfilters, preventing particulate matter that is larger than the microchannels from flowing into the electrode.
  • a water purification system of the invention may include a non-conductive housing with at least one inlet to introduce a water stream to be purified into the housing and an outlet through which purified water exits the housing.
  • the water stream flows from the inlet to the outlet through the porous electrodes and separator.
  • the housing may also include at least one waste outlet, through which particulate materials that are too large to traverse the pores of the electrodes may exit.
  • the water purification system comprises a plurality of unit cells, each of which contains a pair of porous anode and cathode electrodes as described herein with a nonconductive, water permeable separator between the two electrodes.
  • the unit cells may be arranged in series such that a water stream to be purified traverses the cells sequentially, with water of increasing purity being produced as the water stream proceeds through the series of cells.
  • the inlet for such a water purification system may be located upstream from the first electrode through which the water stream travels in the first unit cell, and the outlet for purified water may be located downstream from the last electrode through which the water stream travels in the last unit cell.
  • the water stream travels from the inlet to the outlet through at least one unit cell (i.e., at least one pair of porous electrodes and the separator between the electrodes) of the water purification system.
  • the water stream flows through all of the unit cells of the water purification system.
  • the water purification system includes 2, 3, 4, 5, 6, 7, 8, 9, 10, or more unit cells. In some embodiments, the water purification system includes 2 to 4 unit cells.
  • a water purification system as described herein is operated without applied pressure at the water inlet. In other embodiments, the water purification system is operated with applied pressure at the water inlet. In some embodiments, the water purification system is operated at about 1 to about 40 pounds per square inch, or at about 1 to about 30 pounds per square inch, or at about 1 to about 20 pounds per square inch, or at about 5 to about 30 pounds per square inch, or at about 5 to about 15 pounds per square inch, or at about 5 to about 10 pounds per square inch, or at about 10 to about 15 pounds per square inch.
  • the water purification system is operated at about 5 pounds per square inch, or at about 7.5 pounds per square inch or at about 10 pounds per square inch, or at about 12.5 pounds per square inch, or at about 20 pounds per square inch or at about 30 pounds per square inch, or at about 40 pounds per square inch.
  • the invention provides a method for water purification, including introducing a water stream to be purified into a water purification system as described herein.
  • the water purification system may include a housing having an inlet, an outlet and a flowing water stream.
  • the water stream flows from the inlet to the outlet through at least one unit cell that may include a porous anode electrode, a non-conductive fluid permeable separator, and a cathode electrode.
  • Each porous electrode may contain one, two, or more elements from Group-14 (e.g., exfoliated graphite), at least one oxide (e.g., metal or semi-metal oxide), and at least one polymer (e.g., cross-linked polymer with ion exchange groups).
  • the water stream flows through the electrodes and the separator from the anode to the cathode, or from the cathode to the anode.
  • Particulate matter that is too large to traverse the pores of the electrode may exit the housing through a waste outlet. Ionic, organic, and/or bacterial components of the water stream are retained on the electrodes as the water stream flows through the water purification system, and water exiting the system through the outlet contains reduced amounts of these components than the water stream entering through the inlet.
  • water is purified through a plurality of unit cells arranged in series such that water flows sequentially through the unit cells and the water stream exiting each unit cell contains a reduced amount of ionic, organic, and/or bacterial contamination than the water stream exiting the previous unit cell in the series.
  • FIG. 2 An example of a water purification system in a single cell arrangement in accordance with one embodiment of this invention is shown schematically in Fig. 2.
  • the system comprises a porous cathode electrode 20, a porous anode electrode 21 and an electrically nonconductive, fluid permeable separator element 22 disposed between the anode electrode and the cathode electrode to prevent shorting.
  • Fluid permeable separator element 22 in accordance with one embodiment of this invention is a perforated separator, (e.g., perforated polyethylene or a mesh of polyethylene) having an open area of at least about 60% enabling flow through of the water stream to be purified.
  • perforated separator e.g., perforated polyethylene or a mesh of polyethylene
  • the electrodes and the separator element are disposed within an electrically non-conductive, e.g., plastic, housing 23 which is provided with an inlet opening 24 for introducing the water stream to be purified into the cell for processing, an exhaust waste outlet opening 26 through which particulates separated out of the water stream may be removed, and a purified water outlet opening 25 through which purified water may be removed.
  • an electrically non-conductive, e.g., plastic, housing 23 which is provided with an inlet opening 24 for introducing the water stream to be purified into the cell for processing, an exhaust waste outlet opening 26 through which particulates separated out of the water stream may be removed, and a purified water outlet opening 25 through which purified water may be removed.
  • a water stream to be purified is introduced into the housing through inlet opening 24 disposed near the bottom of housing 23 enabling particles and other solid matter in the water stream filtered out by anode electrode 20 to fall to the bottom of the housing for removal through exhaust waste outlet opening 26.
  • FIG. 3 is a schematic diagram of an example of a water purification system in accordance with one embodiment of this invention comprising a plurality of cell units (i.e., at least two cell units each comprising a pair of porous electrodes with a separator 22 between the electrodes) disposed within a non-conductive housing 30 and arranged for sequential flow of a water stream to be purified through the cells.
  • the water stream is introduced through inlet opening 24 disposed near the bottom of housing 30 into the first cell unit, rises within the cell unit and is forced through the first electrode pair. Particulates within the wastewater fall to the bottom of the housing for removal through exhaust waste outlet opening 26.
  • the water stream Upon rising to the top of the first cell unit, the water stream, which is now substantially devoid of particulates passes through intercell fluid opening 31 into the next cell unit for further treatment.
  • the water stream which becomes successively more purified as it passes through each cell unit, is ultimately passed through purified water outlet opening 25 as substantially pure water.
  • FIG. 4 shows a schematic diagram of a water purification system in accordance with yet another embodiment of this invention having two stages for producing potable water.
  • a water stream to be purified is introduced through inlet opening 24 at the top of a housing and filters through the two stages of cell units, becoming potable water in the process.
  • Fig. 6 A shows a schematic diagram of a water purification system in accordance with another embodiment of this invention.
  • Water to be purified enters the water purification system through an inlet opening 60 at the top of the device and flows through a slot 62 at the bottom of the device to contact a current collector 624.
  • Several electrodes are arranged in series, with non-conductive water permeable spacers 618 separating the electrodes from each other. End electrodes are connected to positive (614) and negative (68) power supplies.
  • the current for such a device remains constant throughout the series of electrodes, but the voltage and water resistance increase from inlet to outlet.
  • Particulate matter may be trapped near the inlet slot 62 and removed by discharge through a waste outlet 66 close to the inlet slot.
  • the purge may be top-down by air or water through the porous electrodes through a purge opening 612 with the electric current turned off, and optionally may be controlled through a actuated valve 610 (e.g., solenoid valve), as depicted in Fig. 6 A.
  • actuated valve 610 e.g., solenoid valve
  • impurities may be released due to the pressure inside the device.
  • Another possible way to release impurities is by pumping air or water from the top to the bottom of the device through valve 708, (or alternatively, from the bottom to the top of the device).
  • the system may be regenerated by purging from 708 to the inlet 704 under a pressure of about 1 to about 40 psi.
  • Purging may employ pressurized air, clean water, filtered salt water with a lower concentration of salt than the concentrated waste, or the internal pressure of the device.
  • a device that operates under pressure shown schematically in Fig. 7, frequent release of waste through a waste outlet is desirable for removal of concentrated impurities. Water may be used to dilute and remove the concentrated waste.
  • Fig. 8 depicts a water purification system in accordance with another embodiment of the current invention.
  • Water to be purified enters an electrode stack through a water inlet port 800 located at the bottom of endplate 810 and flows through an optionally present current collector plate 802.
  • the water is then purified as it travels through electrodes 804 within the electrode system as described herein while a voltage is applied across oppositely charged electrodes.
  • Purified water exits the system through another optionally present graphite current collector plate 802 and is directed to a water outlet port 806 on another endplate 812 for collection or recirculation.
  • the water outlet port may be used as needed during purging wherein fluid (e.g.
  • the system may contain an additional inlet port 808, located on the same endplate 810 as the water inlet port 800, to purge accumulated particulate.
  • the optionally present endplates 810 and 812 (made of, for example, polycarbonate or other injection-moldable plastics) may be used to provide clamping force to the electrode stack assembly (to prevent, for example, water leaks, or damage during handling) and may be clamped together using one or more tie rods 814.
  • the electrodes of the purification system comprises one or more conductive rods (not shown in Fig. 8) oriented perpendicular to and passing through the electrode stack to allow electrical conductivity at the appropriate electrode plates.
  • the rods may be made of, for example, graphite, and may optionally be positioned outside of the electrode stack rather than within the electrode stack.
  • Fig. 9 depicts another embodiment of the present invention, wherein the water purification system 900 described in Fig. 8 is incorporated into an automated continuous water treatment apparatus.
  • Water purification begins with a purification cycle, wherein water from a collection container 926 is directed with a pump 922 through the electrode stack assembly 900 as a voltage is applied by DC power from 930 across the ends of the electrodes 940.
  • present actuator valves 918 and 934 e.g., solenoid valves
  • a salt purge cycle may be used to remove salt accumulated within the electrode stack during purification.
  • positive pressure at the inlet port provided by pump 922 is released (e.g., by turning off the pump) and the voltage supplied by 930 is removed from the stack.
  • An optional second pump 920 may be turned on to withdraw water from the collection container 926 (or optionally, from a separate water source) and direct it through the exit port 904 of the electrode stack. Water entering the exit port 904 then purges accumulated salt from the electrode stack 940 out through the inlet port 902.
  • An actuator valve 934 e.g., solenoid valve
  • a particulate purge cycle may be used to remove solid particulate accumulated at the inlet end of the electrode stack during purification.
  • positive pressure at the inlet port 902 provided by pump 922 may be released (e.g. by turning off the pump) and the voltage supplied by 930 removed from the stack.
  • Actuator valve 916 may be closed and a pump (optionally, pump 920 used during the salt purge cycle) may be turned on to withdraw water from the collection container and direct it through an open actuator valve 918 and to a second inlet port 906 of the electrode assembly 900.
  • Water entering the second inlet port 906 then purges accumulated particulate from the electrode assembly 900 (for example, particulate accumulated between an upstream current collector and the electrode stack) out through the original inlet port.
  • the same optionally present solenoid valve 934 used during the salt purge cycle may be present and configured to direct particulate exiting the original inlet port during the particulate purge cycle into an ejected waste container 924.
  • purification cycles are between about 1 and about 100 minutes in duration, or between about 5 and about 60 minutes, or between about 5 and about 45 minutes, or between about 5 and about 30 minutes, or between about 5 and about 15 minutes, or between about 5 and about 10 minutes, or between about 15 and about 30 minutes, or between about 10 and about 20 minutes.
  • the purification cycle is terminated when the water pressure at the inlet port increases to a predefined level.
  • the purification cycle may terminate when the pressure at the inlet port reaches about 15 pounds per square inch, or about 20 pounds per square inch, or about 25 pounds per square inch, or about 30 pounds per square inch, or about 35 pounds per square inch, or about 40 pounds per square inch, or about 50 pounds per square inch.
  • the purification cycle ends when the electrical resistance of water at the outlet port decreases to a predefined level. In some embodiments, the purification cycle ends when the electrical resistance decreases to below about 1 kohm, or about 2 kohm, or about 5 kohm, or about 10 kohm, or about 20 kohm, or about 50 kohm, or about 100 kohm, or about 200 kohm, or about 500 kohm, or about 1 Mohm, or about 2 Mohm, or about 5 Mohm, or about 10 Mohm, or about 15 Mohm, or about 20 Mohm, or about 50 Mohm.
  • the purification cycle ends when the conductivity of water at the outlet port increases to a predefined level. In some embodiments, the purification cycle ends when the electrical conductivity increases to above about 850 uS, or about 875 uS, or about 900 uS, or about 925 uS, or about 950 uS, or about 975 uS, or about 1000 uS.
  • Duration of the salt purge and particulate purge may vary depending on the type of purification stack being and operating conditions (e.g., the quality of the water source, salt concentration, operating voltage and pressure).
  • Fig. 21 exemplifies the effects on percent salt removal from water when varying the time of salt purge using a four-electrode stack (similar to that described in Fig. HB) wherein each electrode is 7"xll.5", 500 cm 2 active area, coated with cellulose acetate or 14% Nylon solution.
  • the salt purge cycle and the particulate purge cycle are independently between about 5 and about 120 seconds in duration, or about 5 and about 60 seconds, or about 5 and about 30 seconds, or about 5 and about 15 seconds.
  • the salt purge cycle and particulate purge cycle occur simultaneously. In other embodiments, the salt purge and the particulate purge occur independently. In some of these embodiments, the particulate purge cycle occurs about once every 15 minutes, or about once every 30 minutes, or about once every 45 minutes, or about once every 60 minutes, or about once every 90 minutes, or about once every 120 minutes.
  • the salt purge cycle and/or the particulate purge cycle are conducted using a gas.
  • the salt purge cycle and the particulate purge cycle are conducted using purified water.
  • the salt purge cycle and the particulate purge cycle are conducted using impure water.
  • one of the salt purge cycle and the particulate purge cycle is conducted using pure water and the other of the salt purge cycle and the particulate purge cycle are conducted using impure water.
  • the solvent used for the salt purge cycle and the particulate purge cycle is the same. In other embodiments, the solvent used for the salt purge cycle and the particulate purge cycle is different.
  • one or both of the salt purge cycle and the particulate purge cycle is conducted using an inorganic solvent. In some embodiments, one or both of the salt purge cycle and the particulate purge cycle is conducted using a solution comprising an inorganic solvent. In some embodiments, one or both of the salt purge cycle and the particulate purge cycle is conducted using an organic solvent. In some embodiments, one or both of the salt purge cycle and the particulate purge cycle is conducted using solution comprising an organic solvent. In some of these embodiments the inorganic solvent is hydrophilic. In other of these embodiments, the organic solvent is hydrophobic. In some embodiments of the invention, the solvent used in one or both of the salt purge cycle and the particulate purge cycle is intermittently changed to a different solvent.
  • the applied voltage is removed during the salt purge and/or particulate purge cycles.
  • the voltage across the electrode stack is shorted prior to a salt purge and/or particulate purge cycle to prevent residual voltage during the salt purge and/or particulate purge cycles.
  • the applied voltage is reversed during the salt purge and/or particulate purge cycles.
  • the release of the pressure generated during the purification cycle may be used to expel concentrated salt within the system.
  • the stack may be shorted to eliminate any residual voltage across followed by a purge cycle using air to remove remaining salt.
  • a thicker and finer plastic mesh may be used to separate electrodes in the assembly stack. Additionally, sealing of the stack may be improved by first sealing the components individually and then together as an assembled unit.
  • Preventing air from being present in the system while the voltage is applied may prevent areas of high current density.
  • high current density is avoided by applying the voltage after water has started exiting the outlet port.
  • high current density is avoided by using a liquid rather than a gas during the salt purge cycle. Reducing the amount of air within the system may also shorten the purge cycle duration and reduce mixing of wastewater with purified water.
  • an actuator valve e.g., solenoid valve located near the exit port (such as 916 in Fig. 9) is closed while an actuator valve located near the second inlet port (such as 918 in Fig. 9) is open permitting flow through the second inlet port (906) and out through the inlet port (902).
  • an actuator valve located near the second inlet port is closed while an actuator valve located near the exit port is open, permitting flow through the exit port (904) and out through the inlet port (902).
  • both an actuator valve located near the second inlet port (918) and an actuator valve located near the exit port (916) are open, permitting flow through second inlet port (906) and the exit port (904) out through the inlet port (902).
  • a single pump is used for the purification cycle and for both the salt purge cycle and the particulate purge cycle.
  • the single pump is used to pump liquid from an inlet to an outlet during the purification cycle and in a reverse direction for the salt purge cycle and the particulate purge cycle.
  • a single pump is used for the purification cycle and either the salt purge cycle or the particulate purge cycle and a second pump is used for the other of the salt purge cycle or the particulate purge cycle.
  • the apparatus may contain one or more sampling ports (e.g., connected to line 942 in Fig. 9) to collect water for analysis test (such as conductivity, ion concentration, etc.), one or more valves (e.g. needle valve 928 in Fig. 9) may be connected to one or more bypass lines (such as 944 in Fig. 9) to control operating pressure.
  • one or more flowmeters, and/or one or more pressure gauges are included with the apparatus.
  • the apparatus is controlled by an electronic control unit to modulate the duration and frequency of the purification and purge cycles.
  • An electronic control unit may contain a 24 volt DC power supply to operate one or more pumps, and/or an on/off repeat cycle timer.
  • a 4-channel relay may be used to open and close the electrical circuits to one or more pumps, valves, and/or one or more electrode stacks.
  • the voltage supplied to different electrodes within an electrode stack may have a different value.
  • the voltage at one electrode set (such as an electrode pair) may be 2.4V, while the voltage at another electrode set (such as another electrode pair) within the same electrode stack may be 4.8V.
  • the voltage supplied to the electrodes increases as the purification cycle progresses.
  • the voltage supplied to the electrodes increases as the electrical conductivity of water at the leaving the exit port increases.
  • the voltage supplied to the electrodes increases as the resistance of water leaving the exit port decreases.
  • the number of cathode electrodes is equal to the number of anode electrodes (e.g., four cathode electrodes and four anode electrodes). In other embodiments, the number of cathode electrodes is greater than the number of anode electrodes. In other embodiments, the number of anode electrodes is greater than the number of cathode electrodes.
  • the electrodes which provide particle filtration, ionic species concentration and removal, and organic material and bacteria removal, may be carbon-based porous structures.
  • the electrodes may be porous planar structures, i.e., plates, and the separator element is, for example, a perforated plate.
  • the separator element is, for example, a perforated plate.
  • any other configurations of electrodes and separator elements which provide the desired relationship between the electrodes and the separator element, such as tubular or rolled structures, may also be employed, and it is to be understood that such configurations are also considered to be within the scope of the invention claimed herein.
  • the electrodes may be carbon-based porous structures (optionally graphite) for conductivity, and may optionally comprise at least one oxide (e.g. metal oxide) for increasing water adsorption by the electrode, and a polymer (e.g., an ion-exchange, cross-linked, polarizable polymer) for binding the components of the electrode together and for providing mechanical strength to the electrode.
  • the ion-exchange polymer component may also provide ion exchangeable groups on the surface of the electrode for binding ionic components of the water stream.
  • one, two, or more elements from Group- 14 may be added (e.g. carbon black, such as Vulcan XC-72R from Cabot Corporation, to enhance the electrical conductivity of the electrode).
  • the added element may be in the weight percentage of about 5 to about 30 percent, about 5 to about 20 percent, or about 5 to about 10 percent.
  • the electrode may comprise carbon fibers, which may increase the mechanical strength of the electrode and/or silica, which may increase powder mixing uniformity and electrode wettability. In embodiments in which carbon fibers are added, this component is typically included at a weight percentage of about 5 to about 30 percent.
  • this component is typically included at a weight percentage of less than about 5 percent.
  • other metals or semi-metals such as silver or gold, may be added to the electrode that increase the conductivity and/or aid in inactivating microbes.
  • electrodes of the invention comprise exfoliated graphite.
  • Exfoliated graphite is the product of very rapid heating (or flash heating) of graphite intercalation compounds, such as graphite hydrogen sulfate, of relatively large particle diameter (flakes). Vaporization of intercalated substances force the graphite layers apart resulting in an accordion-like shape with an apparent volume typically hundreds of times that of the original graphite flakes.
  • Fig. 20 exemplifies a higher percent salt removal from water when using expanded graphite electrodes compared to standard graphite electrodes (using a four-electrode stack, similar to that described in Fig.
  • a porous electrode as described herein comprises exfoliated graphite in the form of particles less than about 50 ⁇ m in size.
  • the exfoliated graphite may have a surface area of about 500 m 2 /g to about 800 m 2 /g. In some embodiments, the exfoliated graphite may have a surface area of about 700 m 2 /g.
  • the average pore size within the electrode is less than 1 ⁇ m, or less than 0.75 ⁇ m, or less than 0.6 ⁇ m, or less than 0.5 ⁇ m, or greater than 0.05 ⁇ m, or greater than 0.1 ⁇ m, or greater than 0.15 ⁇ m, or greater than 0.2 ⁇ m or greater than 0.25 ⁇ m.
  • the average pore area within the electrode is greater than 10 m 2 /g, or greater than 12 m 2 /g, or greater than 14 m 2 /g, or less than 30 m /g, or less than 28 m /g, or less than 25 m /g.
  • exfoliation of graphite is effected using graphite power (e.g., Superior Graphite Corporation, Chicago) mixed with an HNO 3 /H 2 SO 4 solution (e.g., 1:9 HNC ⁇ H 2 SO 4 v/v).
  • graphite power e.g., Superior Graphite Corporation, Chicago
  • HNO 3 /H 2 SO 4 solution e.g., 1:9 HNC ⁇ H 2 SO 4 v/v.
  • 80 g of graphite power may be mixed with an HNO 3 /H 2 SO 4 solution, and then heated in a 900 to 1000 0 C furnace for 3 minutes.
  • Electrically conductive adsorbent particles may have reactive groups at the particle surface that react with e.g., one or more cross-linking agents, to bind these adsorbent particles into the electrode structure.
  • carbon-based material e.g., exfoliated graphite
  • the cross-links also trap fine carbon black particles in electrodes that contain carbon black, which reduces carbon black erosion.
  • the electrodes comprise at least one resin which may also be used to bind the components of the electrodes into a cohesive structure.
  • the resin has an ion-exchange component, which provides ion-exchange sites on the electrode.
  • the ion-exchange component is a cross-linked, polarizable polymer. Cross-linking of the polarizable polymer is may avoid dissolution of the polymer in the water stream being purified.
  • the resin is a cation exchange resin.
  • the resin is an anion exchange resin.
  • the resin is a mixture of a separate cation exchange resin and a separate anion exchange resin.
  • the resin contains both cation exchange resin and anion exchange resin.
  • Suitable ion-exchange, polarizable polymers include, but are not limited to, polyurethane, polyacrylic acid, sulfonated polystyrene, poly( vinyl alcohol) (PVA), poly(ethylene vinyl alcohol) (PEVA), cross-linked phenolic resin, polyethylene imine (PEI), and combinations thereof.
  • Suitable agents for cross-linking of the polarizable polymers include glyoxal, ketones, such as acetone, aldehydes, such as formaldehyde and glutaraldehyde, methylene amine, amines, imines, amides, and combinations thereof.
  • the resin(s) have an average molecular weight of about 15,000 to about 50,000. In some embodiments, the resin(s) have an average molecular weight of about 30,000.
  • one or more electrodes comprise cellulose and/or a cellulose derivative (e.g., cellulose acetate (CA), cellulose triacetate (CTA), hydroxypropyl cellulose (HPC), methylcellulose, and/or cellulose benzoate (CB)).
  • cellulose and/or a cellulose derivative e.g., cellulose acetate (CA), cellulose triacetate (CTA), hydroxypropyl cellulose (HPC), methylcellulose, and/or cellulose benzoate (CB)
  • Cellulose and cellulose derivatives may aid in removing total dissolved salts (TDS, e.g., NaCl, and (NH 4 ⁇ SO 4 ) and other dissolved species.
  • TDS total dissolved salts
  • the cellulose/cellulose derivative is applied as a thin polymeric membrane or coating which is deposited onto the outside of a carbon-based electrode (e.g., via dip-coating).
  • the cellulose/cellulose derivative (such as the membrane or coating) is cross-linked which may increase the mechanical and chemical stability to allow a greater range of pH and/or temperature operation.
  • a thin membrane or layer of cellulose/cellulose derivative (e.g., cellulose acetate) is cross-linked over a carbon-based electrode which comprises particles such as exfoliated graphite held together with a PEVA, PEI, or polyamide binder (as shown in Fig 17).
  • the thin membrane or layer of cross-linked cellulose/cellulose derivative is between about 50 A to about 1500 A in thickness, or about 25 A to about 175 A in thickness, or about 50 A to about 150 A in thickness, or about 75 A to about 125 A in thickness, or about 100 A in thickness.
  • the surface area and/or surface hydrophilicity of cross-linked cellulose/cellulose derivative is increased (for example, by treatment with a salt solution (e.g., NaCl), a basic solution (e.g., NaOH), or acidic solution (e.g., HNO 3 ) to enhance filtration.
  • a salt solution e.g., NaCl
  • a basic solution e.g., NaOH
  • HNO 3 acidic solution
  • the electrode comprises a cellulose/cellulose derivative (e.g., cellulose acetate (CA), cellulose triacetate (CTA), hydroxypropyl cellulose (HPC), methylcellulose) dispersed and/or embedded within the electrode rather than being deposited and cross-linked onto the carbon-based particles of the electrode as described above.
  • the cellulose/cellulose derivative may be retained within the electrode by a polymer coating on the electrode surfaces (e.g., a thin polymer coating on both large surfaces of the electrode, see 1118A of Figure HC), thus keeping the cellulose/cellulose derivative within the electrode without the need for cross-linking.
  • the electrode comprises cellulose/cellulose derivative within the electrode in an amount less than or greater than about 50%; or about 45%, or about 40%, or about 35%, or about 30%, or about 25%, or about 20%, or about 15%, or about 10%, or about 5%, or about 2%, or about 1%, or about 0.5%.
  • the cellulose/cellulose derivative is in the form of an emulsion which is retained by the polymer coating.
  • an individual electrode comprises both dispersed and/or embedded non-crosslinked cellulose retained within the electrode by a polymer coating as well as a cellulose derivative cross-linked onto the carbon-based electrode.
  • the cellulose derivative cross-linked onto the carbon-based electrode is the polymeric coating retaining some cellulose/cellulose derivative within the electrode.
  • the purification system contains one or more electrodes comprising cellulose/cellulose derivatives in conjunction with one or more electrodes lacking cellulose/cellulose derivatives.
  • the electrode comprising cellulose may remove the majority of salt while the remaining electrodes aid , for example, in removing remaining trace amounts of salt.
  • Fig. HB shows an example of a four electrode stack wherein one electrode, 1116B, comprises a cellulose derivative (e.g., a cross-linked cellulose derivative). Polluted water enters a current collector 1102 (as described herein) through inlet port 1114, wherein the water is directed through the first electrode 1116A.
  • 1116A is a carbon-based electrode as described above, comprising PEVA (e.g., 5 to 10% PEVA with an ethylene content of between 27 to 32% and optional microchannels) and is used to filter untreated liquid (e.g., waste water, sea water, oil and/or gas filled water, or agricultural water).
  • This first electrode may be used to filter/electrochemically remove e.g., particulates, organic macromolecules, bacteria, heavy metal ions, and/or coliforms.
  • the purging system (as described herein) through use of port 1104, may be used at times readily determined by one skilled in the art to purge accumulated matter on the electrode surface. Filtrate passing through electrode 1116A then passes through 1116B.
  • 1116B comprises a cellulose derivative (e.g., cross-linked cellulose acetate) on the surface of a carbon-based electrode (as described herein) and may be used to remove dissolved salts and other soluble matter not retained by 1116A.
  • the filtrate is then passed through the third and fourth carbon- based electrodes, 1116C and 1116D, respectively, which are paired to remove residual ions remaining from the first and second electrodes.
  • Fig. HB illustrates the second electrode in the sequence as comprising the cellulose derivative, other arrangements (such as the first electrode comprising the cellulose derivative) are envisioned.
  • HB may be used in an automated manner (as described herein) with multiple filtration/particulate purge/salt purge cycles for continuous water treatment.
  • Water purification data using a cross-linked cellulose acetate-containing electrode system as described above is shown in Fig. 18.
  • FIG. 11C depicts an example of a four electrode stack wherein one electrode, 1118A, comprises an embedded cellulose derivative in addition to expanded graphite, carbon black, carbon fiber and a PVEOH binder.
  • Polluted water enters a current collector 1134 (as described herein) through inlet port 1132, wherein the water is directed through the first electrode 1118A comprising a cellulose derivative (e.g., cellulose acetate (CA), cellulose triacetate (CTA), hydroxypropyl cellulose (HPC), methylcellulose) which is not cross-linked and is retained within the electrode by polymer coating (e.g., nylon 66) on the electrode edges.
  • a cellulose derivative e.g., cellulose acetate (CA), cellulose triacetate (CTA), hydroxypropyl cellulose (HPC), methylcellulose
  • the polluted water is filtered as it passes through the first electrode and continues through the remaining three electrodes (1118B-D) which may act to remove remaining contaminants from the filtrate before exiting the outlet port 1136.
  • Figure IIC depicts a purification system having four electrodes, in which the first electrode comprises the embedded cellulose derivative, it is to be appreciated that any number of electrodes (e.g., 2, 6, 8, etc.) are contemplated and that the electrode comprising the embedded cellulose derivative may be at any location within the stack (e.g., first, second, third, fourth, last, etc.). Additionally, more than one electrode (e.g., 2, 3, 4, etc.) may comprise the embedded cellulose derivative.
  • the filtration system may comprise both an electrode comprising an embedded cellulose derivative retained within the electrode by a polymer coating (e.g., the first electrode) and one or more electrodes comprising cellulose derivative cross-linked on the electrode surface (e.g., on the second electrode).
  • Figure 22 compares results for percent salt removal from a similar 4-electrodes stack (comprising graphite current collectors, plastic mesh separators, and rubber gaskets) with and without a first electrode comprising cellulose or cellulose derivative (SREA indicates the use of hydroxypropyl cellulose within the first electrode).
  • Figure HC also depicts an alternative purging arrangement which may be particularly useful with filtration systems having an electrode comprising embedded cellulose derivative.
  • the embedded cellulose derivative may be held within an electrode by a polymer coating on the electrode surface. Under a typical arrangement (such as the arrangement shown in Figure HB) this polymer coating may add resistance during purging.
  • an additional purging outlet 1138 may be located downstream of the waste water inlet port 1132.
  • the added port may permit some of the purge flow from the outlet port 1136 during a purge cycle to be directed through one or more of the electrodes lacking polymer coating (electrodes 1118B-D) and out the additional purging outlet 1138, without necessarily requiring the flow to pass through the electrode comprising the polymer coating (1118A).
  • This arrangement may allow sufficient purging of the downstream electrodes (1118B-D) through the additional purging outlet 1138, while also simultaneously permitting particulate purge through the original purging outlet 1130.
  • the purging outlets 1138 and 1130 are open simultaneously during operation of a purge cycle.
  • the purging outlets 1138 and 1130 are open at different times of the purging cycle (e.g., the purging outlet 1138 is opened for one duration while the purging outlet 1130 is closed, then purging outlet 1130 is open during another duration while purging outlet 1138 is closed).
  • the purification system depicted in Fig. HC may be used in an automated manner (as described herein) with multiple filtration/particulate purge/salt purge cycles for continuous water treatment. Data for water purification using an embedded cellulose- containing electrode system as described above is shown in Fig. 22.
  • the electrodes may have hydrophilic properties and, as previously indicated, may optionally have at least one oxide in the electrode for the purpose of increasing water adsorption.
  • the oxide(s) may contribute to hydrophilicity of the electrode. Any oxide that is stable in water may be utilized.
  • the oxide comprises a semimetal (e.g., silica).
  • the oxide is a metal oxide.
  • the oxides range in size from about 0.05 ⁇ m to about 0.5 ⁇ m. Examples of suitable metal oxides include TiO 2 , Al 2 O 3 , and mixtures thereof.
  • impurities such as oily tars and high organic species may collect on the electrode. Such impurities may be removed by periodic back-flushing or purging of the electrode, as described within.
  • the electrodes of this invention may also possess hydrophobic properties. Ions are surrounded by water in aqueous medium. Hydrophobic materials help to expel water, thus expelling ionic impurities.
  • the balance between hydrophilicity and hydrophobicity of the electrode may be controlled, in accordance with one embodiment of this invention, by the appropriate selection of polarizable polymer and cross-linking agent.
  • poly( vinyl alcohol) has fewer -CH 2 - groups than poly(ethylene vinyl alcohol) (PEVA).
  • PEVA poly(ethylene vinyl alcohol)
  • the ethylene group provides hydrophobicity.
  • Certain cross-linking agents such as formaldehyde, have fewer carbon atoms than glutaraldehyde and glyoxal. Generally, as the number of carbon atoms/- CH 2 - groups increases, hydrophobicity increases and hydrophilicity decreases. It has been found that polymers with one (1) to five (5) -CH 2 - groups per e.g., hydroxyl group or other hydrophilic group present in the polymer prior to cross-linking may provide a desirable balance between hydrophilicity and hydrophobicity of the electrode.
  • the electrode contains a hydrophobic content of about 20% to about 50%. In some embodiments, the hydrophilicity is greater than about 60% and the hydrophobicity is less than about 40%. In accordance with one preferred embodiment of this invention, the electrode is provided with a hydrophobicity of up to about 50%. In some embodiments, electrodes comprise at least one hydrophobic group, for example, at least one C-C group, CH-CH group, or CH 2 -CH 2 group in the polymer.
  • Fig. 5 depicts some embodiments wherein porous electrodes as described herein (such as 52) comprise microchannels 50.
  • the microchannels have an average diameter that is greater than average diameter of pores in the electrode.
  • the microchannels have an average diameter that is greater than average diameter of pores in the electrode, but less than the average diameter of particulates carried by the waste or water to be purified.
  • a microchannel may be covered with a water permeable polymeric membrane 54 at each end opening to the surface of the electrode and/or in the interior of the microchannel. In some embodiments, microchannel coverings may be limited to the area at each end opening to the surface of the electrode and formed during fabrication.
  • microchannels may be covered by a separate thin membrane or layer applied following formation of the microchannels.
  • Microchannels may increase water permeability and surface area of the electrode available for ion adsorption by providing better access to additional pores, ion exchange sites, and adsorbents, while the membrane may prevent particulates from passing into or through the microchannels.
  • the microchannels have a larger diameter than the electrode pores. It may be desirable to provide microchannels having a diameter sufficiently large to allow increased water permeability without decreasing ion adsorption.
  • microchannels have diameters from about 0.1 mm to about 1 mm. In some embodiments, microchannels have diameters from about 0.5 mm to about 1 mm.
  • microchannels are spaced about 2 to about 10 mm apart. In one embodiment, microchannels are spaced about 5 mm apart. In some embodiments, the microchannels comprise diameters of about 0.3 to about 0.2 cm with a distance of about 0.5 cm between microchannels In some embodiments, the thin membrane is between about 10 A to about 200 A in thickness, or about 20 A to about 150 A in thickness, or about 50 A to about 125 A in thickness, or about 100 A in thickness.
  • the electrodes may be separator plates described in U.S. Patent No. 5,942,347, the content of which is herein incorporated by reference for all purposes in its entirety.
  • the electrodes as described herein comprise a seal applied to the electrode edges (e.g., water-based acrylic rubber (and other liquid-based polyurethanes), polycarbonate, or silicone). Seals may prevent leaking from the sides of the electrode assembly and/or prevent edge degradation, breaking, and water bypassing while the water purification system is under pressure, as well as providing added stiffness when the electrodes are stacked. The seals may also help distribute pressure during operation to the edges of the electrodes rather than the active area of the electrodes. Applying the seals may be accomplished by dip-coating the electrode edges.
  • a seal applied to the electrode edges e.g., water-based acrylic rubber (and other liquid-based polyurethanes), polycarbonate, or silicone. Seals may prevent leaking from the sides of the electrode assembly and/or prevent edge degradation, breaking, and water bypassing while the water purification system is under pressure, as well as providing added stiffness when the electrodes are stacked. The seals may also help distribute pressure during operation to the edges of the electrodes rather than the active area
  • portions of the electrodes may be coated with one or more non-conducting materials (e.g., polytetrafluoroethylene) to provide electrical insulation.
  • the sealant applied to the edges of the electrode may be sufficiently thick to avoid electrical shorting across electrodes in an electrode stack.
  • Fig. 10 shows one embodiment, wherein the electrodes 106 comprise one or more adjacent gaskets 104 (e.g., one or more silicone foam gaskets) to aid in sealing unevenness of the electrode surface and/or adjacent layer of an electrode stack (e.g., a fluid-permeable separator, such as a mesh).
  • the gasket may be sufficiently thick to avoid electrical shorting across electrodes in an electrode stack.
  • the plates and/or layers of the electrodes stack are sufficiently supported at the center of the electrode stack (e.g., by having adjacent layers in contact with one another) to prevent excessive forces from damaging the water purification system during operation.
  • the electrodes of this invention may be produced by mixing an oxide (e.g., metal oxide) and carbon or exfoliated graphite powders with a polymer resin (polymer solution containing cross-linking agent) and a bubbler, such as ammonium bicarbonate or sodium bicarbonate, and molding (e.g., casting) the mixture at atmospheric pressure and room temperature or an elevated temperature.
  • a polymer resin polymer solution containing cross-linking agent
  • a bubbler such as ammonium bicarbonate or sodium bicarbonate
  • molding e.g., casting
  • the electrode contains about 40% to about 80% porosity, depending on the desired balance of conductivity and mechanical strength.
  • a mixture comprising about 50-60 wt% graphite powders, about 5-20 wt% carbon black, about 7 wt% polymer resin and up to about 10 wt% ammonium bicarbonate molded at room temperature or an elevated temperature, for example, 200 0 C, produces a suitable electrode.
  • the polymer may be cross-linked after evaporation of solvent.
  • an electrode produced as described herein is treated in a hot water bath at about 50 to about 9O 0 C to remove solvent residue and cross-linked catalyst.
  • microchannels are introduced into an electrode of the invention during fabrication.
  • a casted electrode sheet comprising exfoliated graphite, metal oxide, polymeric binder (e.g., PEVA, PVA, or PEI), and/or other materials such as carbon black, silica, and/or carbon fibers, is allowed to dry at room temperature.
  • PEVA polymeric binder
  • small holes to create microchannels are introduced through the entire thickness of the sheet, for example, with pins or laser drills.
  • Liquid polymer e.g., PEVA
  • Electrodes comprising cellulose or cellulose derivatives which coat the carbon- based particles of the electrodes may be fabricated by dip coating an existing electrode with an coating solution and allowing the electrode to dry at room temperature or with applied heat.
  • the coating solution may comprise cellulose and/or cellulose derivative (e.g., cellulose acetate (CA), cellulose triacetate (CTA), and/or cellulose benzoate (CB)), an optional cross- linking agent (e.g., formamide), and a solvent (e.g., acetone).
  • the coating solution comprises between 0 and 10 wt% cellulose/cellulose derivative and between 0 and 10 wt% cross-linking agent.
  • the coating solution contains about 5 wt% cellulose acetate, about 5 wt% formamide, and about 90 wt% acetone.
  • a schematic depicting a cross-linking reaction between free hydroxyl groups of cellulose acetate and formamide is shown in Fig. 19.
  • the deposited cellulose/cellulose derivative coating is treated with a salt solution (e.g., NaCl), a basic solution (e.g., NaOH), or acidic solution (e.g., HNO 3 ) to increase surface area.
  • a salt solution e.g., NaCl
  • a basic solution e.g., NaOH
  • acidic solution e.g., HNO 3
  • the electrode may be soaked in e.g., a 10% NaCl solution or a 0.1 NaOH solution for two hours, then washed with de-ionized water several times.
  • Electrodes comprising cellulose or cellulose derivatives within the electrodes may be fabricated by mixing the cellulose derivative (e.g., hydroxypropyl cellulose, cellulose acetate, and cellulose triacetate) with graphite and carbon, followed by a binder and an optional cross-linking as described in the Examples below.
  • the electrodes are then coated with a polymer (e.g., a non-cellulose polymer, such as nylon 66, polystyrene, and polysulfonic acid (PSA)) to retain cellulose derivative within the electrode composition.
  • a polymer e.g., a non-cellulose polymer, such as nylon 66, polystyrene, and polysulfonic acid (PSA)
  • the water purification system as described herein may comprise a current collector embedded within or contacting the edges of an electrode.
  • the current collector is designed to evenly distribute liquid to the surface of an adjacent electrode for constant pressure at the electrode interface resulting in improved filtration.
  • the current collector is separated from an electrode by one or more layers (e.g., a fluid permeable separator, a silicone foam gasket, or both).
  • a current collector 100 may be located at one end of an electrode stack such that liquid is directed through the current collector prior to distribution to one or more electrodes of the electrode stack.
  • Fig 1 IA shows a front view of a current collector in one embodiment of the current invention.
  • a flat surface 1112 may allow proper sealing with an adjacent electrode and a cavity within the surface.
  • One port 1114 may be used as an inlet wherein liquid may be directed into the cavity of the current collector and evenly delivered to the electrode surface.
  • Fingers 1106 near port 1114 may allow even distribution of water entering the current collector and may also support the area surrounding the port during high pressure operations.
  • Adjacent to port 1104 and 1114 may be dimples 1108 to thoroughly disrupt current flow and aid in preventing areas of high pressure on adjacent plates.
  • Parallel veins 1110 may also aid in distributing incoming water evenly across the entire cavity.
  • An additional port 1104 may be used for purging particulates accumulated on the electrode surface.
  • the current collector may comprise a metal gauze or sheet, such as, for example, stainless steel, nickel, or titanium.
  • the current collector may be constructed of graphite to prevent corrosion.
  • Fig. HB shows one embodiment of the present invention, wherein an upstream current collector 1102 of Fig. 1 IA is located on one end of an electrode stack and a downstream current collector 1120 is located on the opposite end of the electrode stack.
  • the down stream current collector 1120 is shown with an optionally present exit port 1118.
  • the current collector contains multiple inlet and/or outlet ports (such as the additional exit port shown in Fig. HB diagonal to 1118).
  • the water purification system as described herein may contain an electrically nonconductive, fluid permeable separator situated between the porous anode and cathode electrodes.
  • the separator may help maintain flow uniformity (allowing liquid to redistribute between filters and equalize pressure) and prevent electrical short-circuiting during operation of the device.
  • the fluid permeable separator may provide structural support to the electrode stack.
  • the fluid permeable separator element is a non-electron conductive material, such as commercially available perforated plastic sheet, for example perforated polyethylene, polypropylene, plastic mesh, glass fiber paper, other non-electron conductive fiber paper, woven cloth, water permeable anion conductive membrane, or water permeable cation conductive membrane, such as polyamide, polyvinyl alcohol, or polyethylene imine, having an open area of about 40% to about 80%, about 50% to about 70%, or about 60%, enabling flow through of the water stream to be purified.
  • a non-electron conductive material such as commercially available perforated plastic sheet, for example perforated polyethylene, polypropylene, plastic mesh, glass fiber paper, other non-electron conductive fiber paper, woven cloth, water permeable anion conductive membrane, or water permeable cation conductive membrane, such as polyamide, polyvinyl alcohol, or polyethylene imine, having an open area of about 40% to about 80%, about 50% to about 70%
  • the fluid permeable separator 102 may be oriented directly adjacent to an electrode 106, a current collector 100, and/or a gasket 104 (e.g., silicone foam gasket).
  • Gaskets e.g., silicone foam gaskets
  • the water purification system described herein may contain a housing having an inlet port through which water to be purified is introduced into the water purification system, and an outlet port through which purified water exits the system.
  • the housing may be composed of an electrically non-conductive material such as plexiglass, polycarbonate, or polyurethane, which are injection moldable.
  • the housing is a conductive material that is coated with a non-conductive material.
  • the housing may contain an inlet port for introducing the water stream to be purified into the system for processing and a purified water outlet port through which purified water may be removed.
  • the housing also contains an exhaust waste outlet opening through which particulates separated out of the water stream may be removed.
  • the inlet opening and the optional exhaust waste outlet are located upstream from the first porous electrode through which the water stream flows, and the purified water outlet opening is located downstream from the last electrode through which the water stream flows.
  • the inlet opening is located near the bottom of the housing to facilitate removal of particulate and other solid matter in the water stream too large to traverse the pores of the electrodes through an exhaust outlet at the bottom of the housing.
  • the purified water outlet is located at the top of the housing downstream from the last electrode through which the water stream flows.
  • the housing also contains a second inlet port located upstream from the first electrode to introduce a water stream used during a particulate purging process (see 808 in Fig. 8).
  • the housing is comprised of endplates (e.g. plastic endplates) separated by an electrode stack, (see 810 and 812 in Fig. 8).
  • the housing may contain spacers (816 in Fig. 8) between the endplates to prevent leakage through the edges of the electrode stack during standard operation.
  • the housing comprises a means of compressing the electrode stack (e.g., tie rods 814 as depicted in Fig. 8).
  • FIG 12 shows another variation of the invention wherein the electrodes 1204 may be held in place in the housing 1208 with gaskets 1202 and may be sealed at their top and bottom edges with polyurethane or another insulator.
  • some or all material of the water purification system in contact with waste or water is non-metallic to reduce or eliminate corrosion.
  • Table 1 shows a comparison of surface resistance between the electrode produced in accordance with this example and other electrode materials.
  • Two graphite-based porous electrodes were produced using different bubble agents. 8 grams of exfoliated graphite powder and 1 gram of bubble agent (ammonium bicarbonate or sodium bicarbonate) were mixed with 10 grams of water and 10 grams of 10 wt% polyvinyl alcohol, forming a first mixture. 10 grams of water were mixed with 2 grams of 50 wt% glutaraldehyde and 1.5 ml HCl (35 wt%), forming a second mixture. The two mixtures were mixed thoroughly and the resulting mixture was cast to produce a 1/16 in thick sheet. The sheet was cured at room temperature.
  • bubble agent ammonium bicarbonate or sodium bicarbonate
  • Electrodes produced with or without bubble agent were produced as described in Example 2 and tested in a system without applied water pressure. An electrode produced with no bubble agent had low water permeability ( ⁇ 1 ml/min), and the electrode produced with bubble agent exhibited great improvement in permeability (> 20 ml/min). However, the tensile strength of electrodes produced with bubble agents was reduced approximately 20%.
  • Electrode compositions were tested for their ability to remove salt from salt water in a gravity-driven device. 25 to 30% of the salt was removed after filtration. Results with selected electrodes are shown in Table 3. Table 3. Salt Removal with Selected Electrode Compositions
  • the porosity of electrodes was analyzed as a function of PEVA binder concentration. Binder concentrations of 5%, 7.5%, and 10% were used in preparation of the electrodes. The electrodes contained 10% carbon black and 10% carbon fiber. The porosity was tested using the BET (Brunauer, Emmett, and Teller) method to determine electrode properties such as gas uptake, micropore volume (t-plot method), porosity, and pore size distribution via adsorption and desorption isotherms. The results are shown in Table 4. The porosity of the electrode decreased as the amount of binder increased.
  • BET Brunauer, Emmett, and Teller
  • Fig. 14 shows effluent conductivity over time at a pressure of 20 inch H 2 O.
  • the electrode area was approximately 12 cm .
  • Example 8 Porous Graphite-based Electrodes with Microchannels
  • Electrodes were prepared by mixing exfoliated graphite powder with carbon black, metal oxide, and optionally carbon fibers and/or silica. Then, one or more binders, such as PEVA, PVA, and/or PEI were added. The slurry was mixed well. A cross-linking agent was added to the slurry and mixed well. The slurry was cast to a thickness of 0.75 mm. The cast sheet was partially dried at room temperature about 5 to 30 minutes to retain 60 to 80% solvent in the electrode, then punched with pins about 0.3 mm in diameter and about 5 mm apart.
  • binders such as PEVA, PVA, and/or PEI
  • the polymeric binder formed a thin, water permeable membrane at each end of a microchannel as it opened to the surface of the electrode (see Figure 5).
  • the microchannels increase water transport radiance in all directions, and increase the total surface area available for ion adsorption in the porous electrode.
  • the microchannels form saturated zones for ionic adsorption, thus reducing "dead zones" that are difficult for water to enter.
  • a four electrode stack (as shown in Fig. HB) comprising one cellulose acetate electrode described herein was used to test the purification of an aqueous solution of 500 ppm Fe 3+ and 1500 ppm chloride ions.
  • the stack was operated at 30 psig, 4.8 volts, with a resulting current of 150 mA.
  • the outlet flow rate was measured to be 50 GFD.
  • the cycling scheme was 1 minute of purification with 5 seconds of purging. Pure water collection is approximately 77% (see similar results for 0.1% feeed in Fig. 18). While the inlet water had a strong orange color, the outlet water was very pale orange to clear. Twelve samples of the inlet water, rejected water, and outlet water were collected over 8 hours and submitted for analysis. After 30 minutes of operation the resulting outlet water became clearer.
  • Example 11 Porous Graphite-based Electrodes comprising cellulose retained by a polymer coating
  • Cellulose derivative e.g., hydroxypropyl cellulose, cellulose acetate, and cellulose triacetate
  • Electrodes were prepared by mixing exfoliated graphite powder with carbon black, carbon fibers, and the cellulose derivative.
  • a binder such as PVEOH, was added to form a first mixture.
  • a second mixture consisting of l-propanol:deionized water, glutaric dialdehyde, HCl, and 1-propanol was formed, and the two mixtures were mixed together thoroughly and cast as described in example 2A.
  • the finished electrodes have a polymer coating on the electrode to retain cellulose derivative within the electrode.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)

Abstract

L'invention concerne un système de purification d'eau qui comprend une électrode anodique poreuse (21) et une électrode cathodique poreuse (20) comprenant chacune du graphite, au moins un oxyde métallique et un polymère polarisable réticulé échangeur d'ions, et qui comprend facultativement des microcanaux et/ou de la cellulose. Un élément séparateur perméable à un fluide, non conducteur d'électrons (22) est disposé entre les électrodes, ce qui permet aux eaux usées de circuler d'une électrode à l'autre. Les électrodes et le séparateur peuvent être placés à l'intérieur d'un boîtier (23) ayant une ouverture d'entrée d'eaux usées (24) et une ouverture de sortie de déchets (26) et une ouverture de sortie d'eau purifiée (25). De cette manière, les composants du système sont facilement remplacés en cas de besoin.
PCT/US2008/083615 2007-11-14 2008-11-14 Systèmes multifonctionnels de filtration et de purification d'eau Ceased WO2009065023A1 (fr)

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US9969885B2 (en) 2014-07-31 2018-05-15 Kimberly-Clark Worldwide, Inc. Anti-adherent composition
US10028899B2 (en) 2014-07-31 2018-07-24 Kimberly-Clark Worldwide, Inc. Anti-adherent alcohol-based composition
US10238107B2 (en) 2014-07-31 2019-03-26 Kimberly-Clark Worldwide, Inc. Anti-adherent composition
CN111606462A (zh) * 2020-05-29 2020-09-01 安庆丰源化工有限公司 一种高浓度难降解化工废水处理设备
US10988391B2 (en) 2018-12-27 2021-04-27 Robert Bosch Gmbh Desalination electrode
US11168287B2 (en) 2016-05-26 2021-11-09 Kimberly-Clark Worldwide, Inc. Anti-adherent compositions and methods of inhibiting the adherence of microbes to a surface
US11208574B2 (en) 2016-02-26 2021-12-28 Trinseo Europe Gmbh Molded structures of polycarbonate based substrates over molded with silicone rubbers
WO2023275130A1 (fr) 2021-06-29 2023-01-05 Avsalt Ab Électrode de carbone supportée
US11737458B2 (en) 2015-04-01 2023-08-29 Kimberly-Clark Worldwide, Inc. Fibrous substrate for capture of gram negative bacteria
US12037497B2 (en) 2016-01-28 2024-07-16 Kimberly-Clark Worldwide, Inc. Anti-adherent composition against DNA viruses and method of inhibiting the adherence of DNA viruses to a surface
WO2024192215A1 (fr) * 2023-03-14 2024-09-19 PolyJoule, Inc. Électrodes monolithiques à chargement élevé
WO2024218316A1 (fr) * 2023-04-20 2024-10-24 Atomicone B.V. Procédé et dispositif de traitement des eaux et leur utilisation

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WO2001015792A1 (fr) * 1999-08-27 2001-03-08 Corning Incorporated Déionisation d'eau au moyen d'électrodes en carbone activé
JP2003164875A (ja) * 2001-12-04 2003-06-10 Omega:Kk 電解装置
WO2007048772A1 (fr) * 2005-10-28 2007-05-03 Akuatech S.R.L. C02f 1/461 title: nouvelle solution aqueuse de stabilite elevee, electrode comportant un nanorevetement pour la preparation de la solution et procede de fabrication de cette electrode

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WO2001015792A1 (fr) * 1999-08-27 2001-03-08 Corning Incorporated Déionisation d'eau au moyen d'électrodes en carbone activé
JP2003164875A (ja) * 2001-12-04 2003-06-10 Omega:Kk 電解装置
WO2007048772A1 (fr) * 2005-10-28 2007-05-03 Akuatech S.R.L. C02f 1/461 title: nouvelle solution aqueuse de stabilite elevee, electrode comportant un nanorevetement pour la preparation de la solution et procede de fabrication de cette electrode

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9876230B2 (en) * 2011-03-15 2018-01-23 Nano-Nouvelle Pty Ltd Batteries
US20140057169A1 (en) * 2011-03-15 2014-02-27 Nano-Nouvelle Pty Ltd Batteries
US9969885B2 (en) 2014-07-31 2018-05-15 Kimberly-Clark Worldwide, Inc. Anti-adherent composition
US10028899B2 (en) 2014-07-31 2018-07-24 Kimberly-Clark Worldwide, Inc. Anti-adherent alcohol-based composition
US10238107B2 (en) 2014-07-31 2019-03-26 Kimberly-Clark Worldwide, Inc. Anti-adherent composition
US10292916B2 (en) 2014-07-31 2019-05-21 Kimberly-Clark Worldwide, Inc. Anti-adherent alcohol-based composition
US11737458B2 (en) 2015-04-01 2023-08-29 Kimberly-Clark Worldwide, Inc. Fibrous substrate for capture of gram negative bacteria
US12037497B2 (en) 2016-01-28 2024-07-16 Kimberly-Clark Worldwide, Inc. Anti-adherent composition against DNA viruses and method of inhibiting the adherence of DNA viruses to a surface
US11208574B2 (en) 2016-02-26 2021-12-28 Trinseo Europe Gmbh Molded structures of polycarbonate based substrates over molded with silicone rubbers
US11168287B2 (en) 2016-05-26 2021-11-09 Kimberly-Clark Worldwide, Inc. Anti-adherent compositions and methods of inhibiting the adherence of microbes to a surface
US10988391B2 (en) 2018-12-27 2021-04-27 Robert Bosch Gmbh Desalination electrode
CN111606462A (zh) * 2020-05-29 2020-09-01 安庆丰源化工有限公司 一种高浓度难降解化工废水处理设备
WO2023275130A1 (fr) 2021-06-29 2023-01-05 Avsalt Ab Électrode de carbone supportée
WO2024192215A1 (fr) * 2023-03-14 2024-09-19 PolyJoule, Inc. Électrodes monolithiques à chargement élevé
WO2024218316A1 (fr) * 2023-04-20 2024-10-24 Atomicone B.V. Procédé et dispositif de traitement des eaux et leur utilisation
NL2034643B1 (en) * 2023-04-20 2024-10-28 Atomicone B V Method and device for treating water and use thereof

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