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
  • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
  • C02F1/4691—Capacitive deionisation
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
• • 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
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/103—Arsenic compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/12—Halogens or halogen-containing compounds
  • C02F2101/14—Fluorine or fluorine-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/16—Nitrogen compounds, e.g. ammonia
  • C02F2101/163—Nitrates
• • 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
  • C02F2103/003—Wastewater from hospitals, laboratories and the like, heavily contaminated by pathogenic microorganisms
• • 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
  • C02F2103/02—Non-contaminated water, e.g. for industrial water supply
  • C02F2103/023—Water in cooling circuits
• • 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
  • C02F2103/02—Non-contaminated water, e.g. for industrial water supply
  • C02F2103/04—Non-contaminated water, e.g. for industrial water supply for obtaining ultra-pure water
• • 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
  • C02F2103/06—Contaminated groundwater or leachate
• • 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
  • C02F2103/10—Nature of the water, waste water, sewage or sludge to be treated from quarries or from mining activities
• • 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
  • C02F2103/26—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof
  • C02F2103/28—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof from the paper or cellulose industry
• • 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
  • C02F2103/42—Nature of the water, waste water, sewage or sludge to be treated from bathing facilities, e.g. swimming pools
• • 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
  • C02F2201/4618—Supplying or removing reactants or electrolyte
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/22—Electrodes
  • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/22—Electrodes
  • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
  • H01G11/28—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features arranged or disposed on a current collector; Layers or phases between electrodes and current collectors, e.g. adhesives
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/22—Electrodes
  • H01G11/30—Electrodes characterised by their material
  • H01G11/32—Carbon-based
  • H01G11/38—Carbon pastes or blends; Binders or additives therein

Definitions

• the invention relates to a method to prepare a coated current collector electrode for a flow through capacitor, the method comprising:
• a method for water purification is by capacitive deionisation, using an apparatus provided with a flow through capacitor (FTC) for removal of ions in water.
• the FTC functions as an electrically regenerable cell for capacitive deionisation.
• ions are removed from an electrolyte and are held in electric double layers at the electrodes.
• the electrodes can be (partially) electrically regenerated to desorb such previously removed ions without adding chemicals.
• the apparatus for removal of ions comprises one or more pairs of spaced apart electrodes (each pair of electrodes comprising a cathode and an anode) and a spacer, separating the electrodes and allowing water to flow between the electrodes.
• the electrodes are provided with current collectors or backing layers and a high surface area material, such as e.g. carbon, which may be used to store removed ions.
• the current collectors may be in direct contact with the high surface area material.
• Current collectors are electrically conductive and transport charge in and out of the electrodes and into the high surface area material.
• a charge barrier may be placed adjacent to an electrode of the flow-through capacitor.
• the term charge barrier refers to a layer of material which is permeable or semipermeable for ions and is capable of holding an electric charge. Ions with opposite charge as the charge barrier charge can pass the charge barrier material, whereas ions of similar charge as the charge of the charge barrier cannot pass or only partially pass the charge barrier material. Ions of similar charge as the charge barrier material are therefore contained or trapped either in e.g. the electrode compartment and/or in the spacer compartment.
• the charge barrier is often made from an ion exchange material.
• a charge barrier may allow an increase in ionic efficiency, which in turn allows energy efficient ion removal.
• International patent publication WO 2010/131951 discloses a method for preparing a coated current collector for an electrode for a flow through capacitor.
• the method comprises preparing an anode coated current collector using water as a solvent.
• the coated current collectors may be dried in an oven, which may result in a significant reduction in electrode thickness. This way dense electrodes can be obtained by drying the carbon coatings at elevated temperatures.
• Some solvent may be normally retained in the carbon coated current collector after this has been dried in an oven. In fact the retention of solvent in the carbon coated current collector is often beneficial, because it prevents cracking of the carbon coated electrode. Nevertheless, there may be some further drying if the current collectors are stored and/or transported. This further drying may influence the flexibility of the current collectors such that cracks may appear in the carbon coated current collectors for example when they are bended. Cracks may have a negative influence on the working of the carbon coated current collectors and in general cracks should be avoided.
• a coated current collector electrode for a flow through capacitor comprising:
• a preparing a coating paste comprising by weight %:
• the first boiling point is larger than 120 ° C at 1 atm.
• the first solvent may be chosen to have a high boiling point and may not evaporate. In this way it is assured that during storage and/or transport enough of the first solvent will remain in the coated current collector to avoid cracking of the coated current collector.
• the first solvent may be present in 20-40 weight %, or 25-35 weight %, based on the total paste.
• the first solvent may be glycerol, glycerol has a low toxicity so that leaching of the glycerol will not contaminate water in contact with the coated current collector.
• the glycerol may be a food grade glycerol such that the coated current collector electrode may be used for drinking water applications.
• Glycerol has a boiling temperature of 290° Celsius at 1 atm. (please check) and therefore will not evaporate from the coated electrode during transport and storage.
• the first solvent may be a glycol.
• the second solvent may be water with a boiling point of 100 ° C at 1 atm.
• the coating composition with water as a solvent is quite well known such that the coating may not need much adaptation to different solvents. Remaining water in the current collector will not contaminate water in contact with the coated current collector during use.
• the coating paste may be applied by paste-, blade-, dip- spray- or spin coating or by gravure roll coating, extrusion coating or by lamination or screen printing.
• the coated current collector may be used in an apparatus for removal of ions, the apparatus being provided with a housing, the apparatus comprising:
• a water inlet for water entering an interior of the housing a water outlet for letting water out of the interior of the housing;
• a spacer for separating the coated current collectors and allowing water to flow in between the coated current collectors.
• the coated current collector further comprises: 15 - 80 weight % of a first solvent having a boiling temperature at atmospheric pressure larger than 120°C at 1 atm.
• Figure 1 shows a schematic cross-section of an apparatus for removal of ions
• Figure 2a shows a detail enlargement of the stack 3 of figure 1 ;
• Figure 2b shows a detail of figure 1 ;
• Figure 3 shows a prior art and a glycerol electrode being photographed every 30 minutes to show the effects of drying
• Figure 4 shows the cracks in the prior art electrode after being dried for 120 minutes.
• Figure 5 shows the roughness average of 24 electrodes.
• FIG 1 shows a schematic cross-section of an apparatus for removal of ions 1 produced with a method according to the invention with a part of the housing removed.
• the apparatus may comprise twelve flow through capacitor stacks 3.
• the flow through capacitor stack 3 may be provided with repeating units of a first electrode 4 (see figure 2a, which is an enlargement of a stack), a spacer 8, and a second electrode 6.
• the first electrode 4 may be provided with a first current collector 5, (see figure 1 ) which may be bundled together with a first connector 1 1 .
• the second electrode 6 may be provided with a second current collectors 9, which may equally be bundled together on the other side of the apparatus with the second connector 10.
• the first connector 1 1 (see figure 2b, which is a partial enlargement of figure 1 ) may be used to clamp the first current collectors 5 together.
• the current collectors 5, 9 and the first connector 1 1 and the second connector 10 may be made of the same material e.g. carbon (e.g. graphite) to lower the electrical resistivity between the current collectors 5, 9 and the connectors 1 1 , 10.
• the first connector 1 1 may be provided with inserts 15 e.g. from a metal, such as, for example copper.
• the inserts 15 may be screwed in the first connector 1 1 so as to assure low electrical resistivity between the insert 15 and the first connector 1 1 .
• the power terminal 27 is a construction that is connected to both the power supply and one or more connectors 10, 1 1 .
• the power terminal 27 may be fixed into the upper and/or bottom part 22, 24 and /or any other part of the housing.
• the power terminal 27 may be provided with a rail e.g. rod 17 made of, for example, metal e.g. copper to electrically connect all the first connectors 1 1 via their inserts 15 to a power source (not shown).
• the first connector 1 1 and the insert 15 may be provided with an opening for the rod 17.
• the inserts 15 and the rod 17 may be shielded of from the water inside the apparatus by e.g. resin, glue or a paste which functions as a water barrier.
• the resin, glue or a paste or any other water shielding material may optionally be applied to the hollow parts 19 of the connector 1 1 after compression of the stack.
• a tray 13 may be provided to help manufacturing one stack 3 and assembling the stacks 3 together in a housing 21 of the apparatus. Within the housing the stacks 3 may be compressed between the top and bottom part 22, 24. The top part 23 of the housing 21 is provided with a feed-through allowing the rod 17 to make a connection with a power source. This way electrical charge can enter the first electrode via the first current collector 5 and also leave the electrode again, e.g. during regeneration of the electrodes. Water may be provided to an interior of the apparatus via a water inlet 26 the water is allowed to flow around the flow through capacitor stacks 3 and may enter the stacks via the spacers.
• the flow through capacitor stack 3 is provided with a hole in the middle of the stack.
• a circular tube 29 is provided in the hole and via the space between the hole and the tube the water may flow to an outlet 30.
• the interior of the tube 29 may be provided with a nut 35 and threaded bar 33 which may help to compress the electrodes in the stacks 3 and for compressing the stacks 3 between the upper and bottom part 22, 24 of the housing 21 .
• Compressing may occur during production of the apparatus, or optionally during maintenance. By compressing all the stacks at once it may be assured that the compression force is very similar or even equal for each stack and at the same time equally or homogeneously distributed over the surface of the electrodes.
• a first electrode comprising a first current collector 5 may be provided in the tray 13.
• a spacer may be located on top of the first electrode; and a second electrode may be put on top of the spacer.
• a spacer may be put on top of the second electrode followed by another first electrode. This may be repeated until for example 10 first and second electrode units are provided in the stack 3 held by the tray 13 each first electrode separated from a second electrode with a spacer.
• a connector part 1 1 may be located on top of the current collectors 5 and a metal insert 15 may be screwed from the other side of the stack 3 through the tray 13 and the first current collectors 5 to fix the stack 3 to the tray 13.
• the tray 13 and the stack 3 may be connected to the rod 17 of the first power terminal 27 by sliding the insert 15 over the rod 17 to allow a good electrical contact.
• the hole in the insert 15 may be of such a size that it allows for good electrical contact between the insert 15 and the rod 17 and at the same time allowing the insert 15 to slide over the rod 17.
• the connector 1 1 may be pressed on the tray 13 with the current collector 5 or multiple current collectors 5 in between the connector 1 1 and the tray 13 by screwing of the insert 15 in the connector part 1 1 .
• the pressure on the connector part 15 and the current collector may be less than 100 Bar, preferably less than 50 Bar, more preferably less than 20 Bar and most preferably around 10 Bar.
• stacks 3 can be connected to the rod 17 and the stacks 3 may be connected in a similar way to the second connector 10.
• a force may be exerted on the stacks 3 with the nut 35 and threaded bar 33 via the upper and bottom part 22, 24 so as to compress the first and second electrode in a first direction parallel to the length of the threaded bar 33 which is perpendicular to the main surface of the electrode.
• the force may exert a pressure on the stack of less than 5 Bar, preferably less than 3 Bar.
• the first and second connector 1 1 , 10 allow for movement of the first and second current collector 5, 9 along the rod 17, 18 in the first direction such that the current collectors are not damaged by the compression force on the stack 3.
• the movements may be in the order of 0,05 to 10% of the height of the multiple stacks 3 in the first direction.
• a resin or grease may be provided along or through the first and /or second connector 1 1 , 10 in the hollow parts 19 of the connectors 10 , 1 1.
• the resin after hardening fixes the position of the connectors 10, 1 1 and may protect the (metal) inserts 15 and rod 17 from corrosion.
• the apparatus may be operated with the following steps:
• releasing ions from the electrodes by releasing electrical charge from the capacitor via the controller.
• a method to prepare a coated current collector electrode for a flow through capacitor comprises:
• a preparing a coating paste comprising by weight %:
• the carbon in the coating comprises activated carbon, and optionally any other carbon material, such as carbon black.
• the activated carbon may be steam activated or chemically activated carbon, preferably steam activated carbon, such as DLC A Supra Eur (ex Norit).
• the carbon preferably has a specific surface area of at least 500 m2/g, preferably at least 1000 m2/g, more preferable at least 1500 m2/g.
• the anode and cathode may even be made out of different carbon materials. The higher the carbon surface area is, the higher is the ion storage capacity of the current collector.
• the specific surface area of carbon may for instance be measured by the B.E.T. method, as commonly used in the art.
• the carbon may be present in the coating in a concentration of at least 50%, preferably at least 60%, more preferable at least 70%, or even at least 75% by weight of the dry coating.
• the composition generally does not contain more than 98.5% by weight of the dry coating of carbon.
• the binder may be mixable with carbon material.
• the binder is a water based adhesive.
• Binder systems may be selected for their ability to wet the carbon particle or current collector materials, or surfactants or other agents may be added to the binder mixture to better wet the carbon particles or graphite foil.
• a dispersant or a dispersing agent is a surface active substance which may be added to the carbon coating paste to improve the dispersion of the carbon particles and by preventing them from settling and clumping throughout manufacture, storage, application and film formation.
• a dispersants may also be added to the carbon coating paste to stabilize the binder or improve the dispersion of the binder, especially for binders that are water based adhesives.
• a dispersant may be any type of surfactant or any type of emulsifier and may be selected on the basis of the hydrophilic-lipophilic balance number.
• the dispersants may be synthetic detergents, soaps, polymeric surfactants or any type of uncharged polymers, especially water soluble polymers or any mixtures thereof.
• Detergent surfactants can be anionic, cationic or nonionic or mixtures thereof.
• Surfactants may be sodium dodecyl sulphate, alkyl benzene sulphonate or alkyl ethoxylate and amine oxide surfactants.
• Dispersants that are used in the inkjet or paint and coating industry, such as Solsperse® and and Disperbyk® and many others may also be used.
• the dispersant may also be a polyelectrolyte.
• a polyelectrolyte may also be added in addition to a dispersant, because that makes it possible to optimize both the electrolyte and the dispersant independent of each other.
• the optimal amount of polyelectrolyte may be different than the optimal amount of dispersant and by optimizing them independently the dispersant and the polyelectrolyte may be present in the optimal amounts.
• uncharged polymers are polyethylene oxide, polyethylene glycol and polyvinyl pyrrolidone (PVP, e.g. the Luvitec® range or the PVP range from International Speciality Products (ISP).
• PVP polyvinyl pyrrolidone
• Suitable commercial binder materials may be polyacrylic based binders such as the FastbondTM range from 3MTM.
• the binder may be present in the coating in a concentration of at least 1 %, preferably at least 2%, more preferable at least 5% by weight of the dry coating.
• the binder is preferably present in the coating in a concentration of less than 50%, preferably less than 40%, more preferably less than 30%, even more preferably less than 20%, still more preferably less than 15% by weight of the dry coating.
• a polyelectrolyte may be added.
• the polyelectrolyte may be both anionic or cationic.
• the carbon electrodes containing the polyelectrolytes can be used in FTC cells that are built either with or without ion selective membranes.
• anionic or cationic polyelectrolytes can be used for both the anode and the cathode.
• mixtures of anionic and cationic polyelectrolytes can be used as well as zwitterionic polymers for both the anode and the cathode. Nevertheless, it is preferred to use cationic polyelectrolytes for the anode and anionic polyelectrolytes for the cathode to obtain an increase in ion storage capacity.
• Suitable cationic polyelectrolytes in the context of the present invention are for example nitrogen based polyelectrolytes.
• Commercially available polyelectrolytes of this type are poly ethylene imines, such as Lupasol ® (ex BASF), polyquaterniums, such as the Merquat ® polyquaterniums (ex Nalco), poly amines, and poly vinyl pyridine and its derivatives.
• polyethylene imines such as Lupasol ® (ex BASF)
• polyquaterniums such as the Merquat ® polyquaterniums (ex Nalco)
• poly amines poly amines
• poly vinyl pyridine and its derivatives such as cationic polyacrylamides, such as Accepta (ex Accepta).
• Suitable anionic polyelectrolytes are sulphonated polymers and carboxylated polymers, and mixtures thereof.
• Commercially available anionic polyelectrolytes are polystyrene sulfonate, such as Flexan ® (ex National Starch) and Polycarboxylates, such as the SokolanTM series (ex Basf)
• Both the cationic and anionic polyelectrolytes preferably have a molecular weight of at least 200 D, more preferably at least 500 D, still more preferably at least 1000 D.
• the molecular weight is preferably not more than 5,000,000 D, preferably less than 100,000 D, still more preferably less than 10,000 D.
• the polyelectrolytes can be homodisperse or polydisperse covering a broad molecular weight range.
• the polyelectrolyte may be present in the coating in a concentration of at least 0.5%, preferably at least 1 %, more preferable at least 2% or even at least 4% by weight of the dry coating.
• the polyelectrolyte is preferably present in a concentration of not more than 30%, preferably not more than 20%, more preferably not more than 15%, or even less than 10% by weight of the dry coating.
• the amount of carbon and polyelectrolyte may be adjusted so as to balance the capacitance of the anode and cathode electrodes. In practice this means that more polyelectrolyte and/or carbon may be used for the anode than for the cathode electrode.
• the solvents, suitable for mixing the coating paste may be 10 - 50 weight %, preferably 20-40 weight %, more preferably 25-35 weight % based on the total paste of a first solvent having a first boiling point; and, 10 - 50 weight %, preferably 20-40 weight %, more preferably 25-35 weight % based on the total paste of a second solvent having a second boiling point.
• the first solvent may be an alcohol, such as a polyol for example a triol such as as glycerol or a dyol such as ethylene glycol.
• the glycerol can be a food grade glycerol so that the electrode can be used in an apparatus for drinking water.
• the first boiling point of the first solvent is larger than 120 ° C at 1 atm.
• the second solvent may be a water and the second boiling point may be 100 ° C at 1 atm.
• the second boiling point of the second solvent is lower than the first boiling point of the first solvent.
• the second solvent is generally evaporated from the paste in order to form a solid coating on the current collector.
• the evaporation may for instance be achieved by exposure to air (ambient or heated).
• the coating preferably contains less than 50% solvent, more preferably less than 30%, still more preferably less than 10% of the second solvent.
• the first solvent may remain in the solid coating on the current collector until the electrode in use will be flushed with water and the first solvent may be flushed away.
• the present invention provides a method for preparing a coated current collector, comprising the steps of:
• Drying the coated current collector may be done at a temperature range from 15°C, preferably 30°C to 120°C.
• the carbon paste may be applied by paste-, blade-, dip- spray- or spin coating as single layers or multiple layers as well as by gravure roll coating, extrusion coating or by lamination or screen printing.
• the screen printing process consists of forcing the carbon paste through a stencil covered substrate, e.g. grafoil ® or through a wire mesh which has been mounted in a sturdy frame. In this case the carbon paste only goes through the open areas of the stencil and is deposited onto a printing substrate, e.g. grafoil ®, positioned below the frame.
• Manual screen printing can be accomplished with only a few simple items: a sturdy frame, screen fabric, stencils, squeegees, and carbon paste. Automatic press equipment can be used which would greatly speed up the process.
• the current collector sheets may be coated on both sides with the carbon paste.
• the dry electrode made by the method of the invention, as coated onto the current collector generally has a thickness of at least 50, preferably at least about 100, more preferably at least about 200 micrometer; and preferably less than 1000, more preferably less than 750 micrometer.
• Current collector preferably at least about 100, more preferably at least about 200 micrometer; and preferably less than 1000, more preferably less than 750 micrometer.
• the current collector may be any common type of current collector.
• the material of which the current collector is made is a conducting material. Suitable materials are e.g. carbon, such as graphite, or carbon mixtures with a high graphite content, metal, such as copper, titanium, platinum, (stainless) steel, nickel and aluminium.
• the current collector is generally in the form of a sheet. Such sheet is herein defined to be suitable to transport at least 33 Amps/m 2 and up to 2000 Amps/m 2 .
• a surface of graphite foil such surface may be corona treated, plasma etched, chemically or mechanically abraded or oxidized to enhance binder adhesion.
• the thickness of a graphite current collector then typically becomes from 100 to 1000 micrometer, generally 200 to 500 micrometer.
• Charge barriers have been disclosed in US 6,709,560 for use in FTC.
• the present invention provides as an embodiment a coated current collector, as disclosed herein above, further comprising a charge barrier applied to the electrode coating layer, the charge barrier comprising a membrane, selective for anions or cations, the charge barrier being applied to the electrode coating layer as a further coating layer or as a laminate layer.
• the invention provides a system comprising the coated current collector according to the invention, comprising carbon, binder and polyelectrolyte, in combination with a separate conventional charge barrier as disclosed in US 6,709,560.
• Suitable membrane materials may be homogeneous or heterogeneous.
• Suitable membrane materials comprise anion exchange and/or cation exchange membrane materials, preferably ion exchange materials comprising strongly dissociating anionic groups and/or strongly dissociating cationic groups.
• examples of such membrane materials are NeoseptaTM range materials (ex Tokuyama), the range of PC-SATMand PC-SKTM(ex PCA GmbH), ion exchange membrane materials ex Fumatec, ion exchange membrane materials RalexTM (ex Mega) or the ExcellionTM range of heterogeneous membrane material ex Snowpure).
• the coated current collectors are especially useful in FTC devices that require low system cost for example in domestic appliances such as coffee makers, espresso machines, washing machines, dish washers, refrigerators with ice or water dispensers, steam irons, etc, where the removal of hardness ions such as calcium and magnesium, as well as other ions is beneficial. They can also be used for residential water treatment such as point of use devices as well as point of entry devices for whole households. These electrodes can also be used for commercial and industrial applications, e.g. water treatment in agriculture (e.g. treatment of ground water and surface water), boiler water, cooling towers, process water, pulp and paper, laboratory water, waste water treatment, mining as well as for the production of ultra pure water. Finally the electrodes may be used for the removal of problem ions such as nitrate in e.g. swimming pools and arsenic and/or fluoride in e.g.
• Glycerol electrodes have no cracks or surface defects due to oven drying.
• the electrodes are also flexible and can be bended, this way the electrodes can be produced in roles.
• Another advantage is that the electrode thickness of glycerol electrodes can be larger, which results in a higher ion storage capacity of the electrodes in the FTC apparatus.
• a standard and a glycerol electrode were put on a table at a room temperature (20°C) being photographed (the prior art electrode is in the background and the glycerol electrode in the foreground of the picture) every 30 minutes from figure 3a (initial), figure 3b (after 30 minutes), figure 3c (after 60 minutes), figure 3d (after 90 minutes), and figure 3f (after 120 minutes).
• the prior art electrode was soaked in water right after punching so as to prevent drying before the start of the experiment; on the other hand the glycerol electrode had already been exposed to air for six months.
• Figure 4 discloses the cracks in the prior art electrode after being dried for 120 minutes to ambient temperatures and after they have been subsequently flattened. Electrode handling time increases from about 20 minutes for the prior art electrode to nearly infinite for the glycerol electrode. That gives the next benefits:
• FIG. 5 shows the roughness average of 24 electrodes.
• Glycerol electrode G according to an embodiment of the invention is 25% less rough than standard electrodes S according to the prior art. This improves the contact between electrode and membrane during stack building which improves the quality of the apparatus for deionizing water.

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• Chemical & Material Sciences (AREA)
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• Water Supply & Treatment (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
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• Engineering & Computer Science (AREA)
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• Electric Double-Layer Capacitors Or The Like (AREA)
• Water Treatment By Electricity Or Magnetism (AREA)

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• 2014
  • 2014-07-02 EP EP14175475.4A patent/EP2962996B8/en active Active
• 2015
  • 2015-07-01 CN CN201580036359.7A patent/CN106795014B/zh active Active
  • 2015-07-01 JP JP2017519992A patent/JP2017527438A/ja active Pending
  • 2015-07-01 EP EP15733450.9A patent/EP3164364A2/en active Pending
  • 2015-07-01 WO PCT/EP2015/065029 patent/WO2016001325A2/en not_active Ceased
  • 2015-07-01 US US15/320,744 patent/US10759682B2/en active Active

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