JP5341715B2 - Ion adsorption apparatus and method for removing ionic substances - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for removing ionic substance which can exhibit sufficient ion removing power by means of self electric power generation without requiring large equipment, does not cause secondary contamination due to solvent and facilitates the treatment of a material to be adsorbed, and to provide a method of removing ionic substance using the device for removing ionic substance. <P>SOLUTION: The ion adsorption device includes an electrode made of an collector in which a semiconductor photocatalytic film and an electrolyte adsorptive conductive material are tightly adhered to each other. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a self-powered ion adsorption device using light energy and a method for removing an ionic substance using the same. This ion adsorption device can be used for purposes such as water purification.

  In recent years, it has become a problem that various substances contained in wastewater cause environmental pollution. Conventionally, environmental pollution has been reduced by lowering the concentration at the time of discharge, but it is important to reduce the final discharged substances, and emission regulations are clearly moving in that direction It is no exaggeration to say.

  As a method for removing ionic substances contained in the solution, when the concentration of ions is high, an appropriate metal ion or anion, for example, an alkaline earth metal ion or carbonate ion, is added to form an insoluble salt, which is filtered In general, a method for reducing the concentration of anions contained in a solution by removing insoluble salts is generally used. However, although it is an insoluble salt, there is no salt that does not have solubility at all, and depending on the composition component in the solution, it may not be insoluble, and the ion concentration cannot be sufficiently reduced.

  Conventionally, as a method for reducing the concentration of ions contained in a solution, a method by physical adsorption using a porous material such as activated carbon (see Patent Document 1), a method by chemical adsorption using an ion exchange resin (Patent Document) 2) is known. As a method of removing metal contaminants in water using electrolytic adsorption, a method of combining with an ion exchange resin or the like or using a single electrochemical removal step is known (see Patent Document 3).

  On the other hand, as a method for electrochemically removing an ionic substance, a liquid processing method using a flat plate-shaped liquid passing type electric double layer capacitor is known (see Patent Document 4). Furthermore, from the viewpoint of preventing the deposition of scale on the surface of the collector electrode, a method of desalting by passing the liquid vertically through the activated carbon layer has been proposed (see Patent Document 5).

JP 2003-1112917 A JP 11-235594 A JP-A-6-121978 JP-A-6-325983 JP 2004-97915 A

  However, with porous materials such as activated carbon, it is not possible to preferentially adsorb only ionic substances, and other substances are adsorbed, the adsorption rate of ionic substances decreases, and the actual adsorption ability cannot be exhibited. In the chemical adsorption of ion exchange resins, there are problems such as high costs due to low durability such as removal of ion exchange groups of the ion exchange resin and attention to contamination due to decomposed resin components. Moreover, in the method disclosed in Patent Document 3, it is difficult to say that sufficient removal capability is exhibited in addition to the complexity of combining with an ion exchange resin or the like. In the method disclosed in Patent Document 4, it is difficult to avoid the deposition of scale on the surface of the collector electrode as time passes.

  On the other hand, the method disclosed in Patent Document 5 prevents the deposition of scale on the surface of the collector electrode, and is expected to be effective in that respect. However, in this method, it is necessary to supply electric energy from other sources, and there is a problem in that it is large in equipment and requires a complicated mechanism. Therefore, an object of the present invention is to remove an ionic substance that does not require a large facility, exhibits sufficient ion removal capability by self-power generation, has no secondary contamination of the solvent, and can easily treat the adsorbate. It is an object of the present invention to provide a method for removing an ionic substance using the above.

  The present inventor has completed the present invention through intensive studies. According to the present invention, the following is provided.

[1] An ion adsorption apparatus including an electrode made of a current collector in which a semiconductor photocatalyst film and an electrolyte adsorbing conductive material are in close contact.
[2] A method for removing an ionic substance using the ion adsorption apparatus according to [1].
[3] The method for removing an ionic substance according to [2], wherein electric power is supplied using sunlight.
[4] The method for removing an ionic substance according to [2] or [3], wherein the ion removal capability is recovered by discharging adsorbed ions by discharging or applying a reverse voltage when the ion removal capability of the ion adsorption apparatus is reduced.

  According to the present invention, the above-described object can be achieved by using an electrode integrated with a semiconductor photocatalyst that is photoexcited in an ion adsorption apparatus.

It is a figure which shows the outline of the ion adsorption system using a solar cell. It is a figure which shows an example of the ion adsorption apparatus of this invention. It is a figure which shows the other example of the ion adsorption apparatus of this invention.

  The semiconductor photocatalyst used in the present invention is not particularly limited, and examples thereof include titanium oxide, zinc oxide, iron oxide, tin oxide, and tungsten oxide. Preferable examples include titanium oxide, zinc oxide, tungsten oxide and the like, and titanium oxide and zinc oxide are more preferable from the viewpoint of cost and economy. By employing a semiconductor photocatalyst made of an oxide, an ion adsorption device can be manufactured without using a high-purity material, which is industrially advantageous. These can be used alone or in combination. Examples of the composite mode include use of a mixture of two or more semiconductor photocatalysts and preparation of a plurality of single semiconductor photocatalyst layers to form a laminated structure. Further, in the present invention, since the power generation part and the ion adsorber are united, the structure is simpler than the system combining the solar cell 1 and the ion adsorber 2 as shown in FIG. In addition to the advantage of being less, since no transparent electrode is used in the photovoltaic part, there is no need to use expensive noble metals or rare metals, and further, the degradation of the transparent electrode proceeds due to the pH of the solution in which ions are dissolved. It has the merit that the problem can be solved.

  From the viewpoint of charge separation efficiency by photoexcitation and cost, it is preferable to use titanium oxide. As the titanium oxide, divalent to tetravalent titanium oxides can be used. These may be used alone or in combination. From the viewpoint of electrical conductivity, it is more preferable to use trivalent to tetravalent titanium oxide.

  The method for forming the semiconductor photocatalyst is not particularly limited as long as it is a method capable of obtaining adhesion with the current collector. For example, a semiconductor photocatalyst sol solution can be applied and heated to make it adhere, or a ceramic can be formed by changing to a semiconductor photocatalyst during film formation by a method such as plasma spraying or arc spraying. It is also possible to form a film by a cold spray method in which a semiconductor photocatalyst is formed as it is. These may be formed by a single method or may be combined to form a laminated film.

  The resistance (sheet resistance) in the thickness direction of the semiconductor photocatalyst film is preferably in the range of 0.1 to 1000 Ω / □ in order to efficiently use the current generated by photovoltaic power generation.

  The material of the current collector is not particularly limited, and a metal current collector such as aluminum, iron, nickel, platinum, silver, gold, copper, and molybdenum, and a non-metal current collector such as a carbon electrode can be used.

  The shape of the current collector is not particularly limited, and may be a thin film shape, a plate shape, or a rod shape. In order to secure an area as a photovoltaic cell, a thin film or a plate is preferable.

  The electrolyte adsorptive conductive material used in the present invention is not particularly limited, and the above-described semiconductor photocatalyst, carbon material, and the like can be used. As the carbon material, graphite, activated carbon or the like can be used. In consideration of the surface area, conductivity, and price, it is preferable to use an activated carbon molded body.

The activated carbon molded body may be a nonwoven fabric made of fibrous activated carbon, woven fabric, or felt, and the activated carbon fine powder is made into a sheet using PTFE or the like as a binder together with a carbon black-based conductive material such as ketjen black or acetylene black. You may use what was shape | molded. The surface area of the activated carbon affects the storage capacity because it is an ion adsorption area. That is, the larger the surface area of the activated carbon, the better, but the larger the surface area, the lower the electrical conductivity of the activated carbon. The surface area of the activated carbon is preferably 400 to 5000 m ² / g.

  The bonding method is not particularly limited, but it is necessary to use a method that does not impair the conductivity. Therefore, a method such as pressure bonding to the current collector, arc spraying to the current collector, adhesion by thermal spraying such as plasma spraying, or the like can be used, or a conductive adhesive can also be used. You may adhere | attach with electroconductive tapes, such as a carbon tape. Furthermore, a current collector can be produced on the electrolyte-adsorbing conductive material by an arc spraying method, a plasma spraying method, or the like to provide adhesion. From the standpoint of adhesion to the current collector and not blocking the pores of the conductive material layer, it is preferable to use a conductive adhesive or a conductive tape. As the conductive adhesive, a paste in which a conductive substance such as carbon, silver, or polyaniline is dispersed in a thermosetting resin material such as an acrylic resin, a phenol resin, or an epoxy resin can be used. From the viewpoint of interfacial resistance and deterioration during energization, it is preferable to use a paste in which a carbon material such as graphite powder, graphene, or carbon black (for example, ketjen black or acetylene black) is dispersed. Further, as a solvent for the dispersion paste, a water-soluble organic solvent such as butyrolactone and N-methylpyrrolidone, water can be used. The use of water that does not cause blockage is preferred.

  In the present invention, in order to make the ion adsorption apparatus compact, an insulating separator is placed between the electrodes, and a plurality of electrodes can be brought into close contact with each other via the separator.

  The material of the separator is not particularly limited as long as it is ion-permeable and hydrophilic, and a fiber sheet material, a multi-porous polymer film-like sheet material, a particle-containing sheet material, and the like can be used. In consideration of liquid permeability and stretchability, it is preferable to use a fiber sheet material or a particle-containing sheet material, and a felt-like or paper-like one is preferred.

  As a material constituting the separator, a hydroxyl group-containing polymer material such as cellulose, tencel, polyvinyl alcohol, and ethylene polyvinyl alcohol copolymer can be used. In addition, a hydrophilic material obtained by immersing a water-repellent material such as polyethylene or polypropylene with fluorine, plasma, fuming sulfuric acid, or the like, or a material having a hydrophilic functional group such as polyacrylic acid or polymethacrylic acid can be used. It is preferable to use a material selected from a hydroxyl group-containing polymer material in consideration of the fact that ions to be separated are adsorbed more than necessary, and the ion permeability is lowered and the flexibility of the material is avoided.

  An outline of the ion adsorption apparatus of the present invention is shown in FIG. The ion adsorption apparatus of the present invention includes a photovoltaic electrode 14 composed of a current collector 12 in which a semiconductor photocatalyst film 11 and an electrolyte adsorbing conductive material 13 are in close contact as an essential component. In FIG. 2, the current collector 12 is composed of a mesh, and is devised to reduce the weight of the electrode. In the ion adsorption apparatus of the present invention, electrons are emitted from the semiconductor photocatalyst film 11 that has received the light 10 such as sunlight, and the electrons move to the current collector 12. As a result, the surface of the semiconductor photocatalyst film 11 is positively charged and the electrolyte-adsorbing conductive material 13 is negatively charged. Therefore, among the electrolytes present in the housing 15, anions adhere to the surface of the semiconductor photocatalyst film 11. Then, the cation adheres to the surface of the electrolyte adsorptive conductive material 13. By connecting the current collector 12 to another current collector (counter electrode) 16 via a load 17 such as a conducting wire, electrons move to the current collector (counter electrode) 16. In this case, negative ions adhere to the photovoltaic electrode 14 formed of the current collector 12 in which the semiconductor photocatalyst film 11 and the electrolyte adsorbing conductive material 13 are in close contact, and positive ions adhere to the current collector (counter electrode) 16. FIG. 3 is a view showing an aspect in which the electrolyte adsorbing conductive material 18 is further adhered to the current collector 16. In the embodiment of FIG. 3, the electrolyte adsorbing conductive material is in close contact with both electrodes, so that the electrolyte adsorption efficiency is very high.

  As can be seen from the above description, the counter electrode is not an essential component in the ion adsorption apparatus of the present invention.

  According to the ionic substance removing device of the present invention, as a cationic component, alkali metal ions such as lithium, sodium and potassium, alkaline earth metal ions such as magnesium, calcium and barium, and typical metals such as aluminum, gallium and indium Transition metal ions such as ions, nickel, copper, iron, cobalt, zinc, palladium, platinum, gold, silver, rhodium, ruthenium, osmium, iridium, rare earth metal ions such as cerium, praseodymium, thulium, terbium, europium, etc. It is possible to adsorb and remove metal ion species and organic cationic compounds such as cationic complexes containing these metals, ammonium and phosphonium.

  In addition, as anion components, halogen ions such as chlorine, bromine and iodine, sulfuric acid, sulfurous acid, nitric acid, phosphoric acid, phosphorous acid, mineral acid ions such as boric acid, chloric acid and hypochlorous acid, tetrafluoroborane, hexafluoroborane, Complex ions such as tetrafluorophosphine can be removed by adsorption. A mixture of a liquid containing a cationic component and a liquid containing an anionic component can also be applied.

  The ion adsorption apparatus according to the present invention may be used in a form in which a solution for removing ions by adsorption is contained in a sealed container or in an open container such as a beaker, or a solution for removing ions by adsorption. You may use it in the form installed in the flow path.

  The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

Example 1
A titanium oxide film having a film thickness of 100 μm was formed as a semiconductor photocatalyst film by atmospheric pressure plasma spraying at a particle speed of 450 m / S using Toho titanium rutile titanium oxide particles having an average particle diameter of 2 μm on a 3 mm thick copper plate. At this time, the resistance in the film thickness direction was 30Ω / □. This copper plate was cut into a 30 mm square and the sprayed surface was a 20 mm square. Photoexcitation by adhering a 20mm square activated carbon cloth (Kuraray Chemical Co., Ltd., Cractive CH) as an electrolyte-adsorbing conductive material to the opposite side of this sprayed surface with a conductive carbon tape ( # 15-1095 conductive carbon double-sided tape manufactured by Oken Shoji Co., Ltd.). It was set as the emitting electrode. Cut the copper plate that was not sprayed in the same way, and bonded 20mm square of activated carbon cloth (Kuraray Chemical's Cractive CH) with conductive carbon tape (# 15-1095 conductive carbon double-sided tape manufactured by Oken Shoji Co., Ltd.) ) Filter paper (Advantech 5A) was sandwiched between both copper plates, and they were placed so that they did not touch each other. Both electrodes were wired with a copper wire, immersed in 50 g of a 12.7 wt% sodium chloride aqueous solution (sodium ion concentration 5.0 wt%), and allowed to stand under sunlight for 3 hours. When the sodium ion concentration of the aqueous sodium chloride solution after standing was determined by cation chromatography, it was found to be 2.1% by weight. From this result, it can be seen that this apparatus functions as an ion adsorption apparatus.

Example 2
The same procedure as in Example 1 was performed except that the sodium chloride aqueous solution was replaced with a 1.3 wt% magnesium hydroxide aqueous solution (magnesium ion concentration 0.5 wt%), and the magnesium ion concentration was 0.1 wt% by cation chromatography. Observed that it has declined.

Example 3
The same procedure as in Example 1 was conducted except that the sodium chloride aqueous solution was replaced with a 1400 ppm aqueous solution of sodium borate anhydride obtained by calcining sodium borate decahydrate at 300 ° C. (sodium ion concentration 320 ppm, borate ion concentration 1080 ppm). It was observed that the sodium ion concentration was 19 ppm by cation chromatography and the borate ion concentration was 27 ppm by anion chromatography.

Comparative Example 1
The same procedure as in Example 1 was carried out except that the semiconductor photocatalyst film was not laid, but the sodium ion concentration after standing for 3 hours under sunlight was 4.8% by weight.

Comparative Example 2
The same procedure as in Example 2 was conducted except that the semiconductor photocatalyst film was not laid, but the magnesium ion concentration after standing for 3 hours under sunlight was 0.4% by weight.

Comparative Example 3
The same procedure as in Example 3 was performed except that the semiconductor photocatalyst film was not laid, but the sodium ion concentration after standing for 3 hours under sunlight was 195 ppm, and the borate ion concentration was 960 ppm.

Example 4
A titanium oxide film having a thickness of 100 μm was formed on a 3 mm thick copper plate by atmospheric pressure plasma spraying at a particle speed of 450 m / S using anatase titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd. having an average particle size of 0.1 μm. At this time, the resistance in the film thickness direction was 27Ω / □. This copper plate was cut into a 30 mm square and the sprayed surface was a 20 mm square. On the opposite side of the sprayed surface, an activated carbon cloth (Kuraray Chemical Co., Ltd., Clastic CH) 20 mm square was adhered with a conductive carbon tape (Oken Shoji Co., Ltd. # 15-1095 conductive carbon double-sided tape) to form a photo-excited electrode. Cut the copper plate that was not sprayed in the same way, and bonded 20mm square of activated carbon cloth (Kuraray Chemical's Cractive CH) with conductive carbon tape (# 15-1095 conductive carbon double-sided tape manufactured by Oken Shoji Co., Ltd.) ) Filter paper (Advantech 5A) was sandwiched between both copper plates, and they were placed so that they did not touch each other. Both electrodes were wired with a copper wire, immersed in 50 g of a 12.7 wt% sodium chloride aqueous solution (sodium ion concentration 5.0 wt%), and allowed to stand under sunlight for 3 hours. When the sodium ion concentration of the aqueous sodium chloride solution after standing was determined by cation chromatography, it was found to be 1.7% by weight. From this result, it can be seen that this apparatus functions as an ion adsorption apparatus.

Comparative Example 4
On a 3 mm thick copper plate, anatase titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd. with an average particle size of 0.1 μm and polytetrafluoroethylene (manufactured by Mitsui DuPont Fluorochemicals, Teflon (registered trademark) 6J) in mass ratio of 95: 5 Were mixed, kneaded and stretched, and bonded as a 100 μm thick titanium oxide sheet with conductive carbon tape (# 15-1095 conductive carbon double-sided tape manufactured by Oken Shoji Co., Ltd.). At this time, the resistance in the film thickness direction was 23000 Ω / □. This copper plate was cut into 30 mm square. A 20 mm square activated carbon cloth (Kuraray Chemical Co., Ltd., Cractive CH) is bonded to the opposite side of this titanium oxide-containing resin layer with a conductive carbon tape (# 15-1095 conductive carbon double-sided tape, manufactured by Oken Shoji Co., Ltd.) It was. Cut the unsprayed copper plate in the same way, and bond 20 mm square of activated carbon cloth (Kuraray Chemical's Cractive CH) with conductive carbon tape (# 15-1095 conductive carbon double-sided tape manufactured by Oken Shoji Co., Ltd.) to obtain an adsorption electrode. It was. Filter paper (Advantech 5A) was sandwiched between both copper plates, and they were placed so that they did not touch each other. Both electrodes were wired with a copper wire, immersed in 50 g of a 12.7 wt% sodium chloride aqueous solution (sodium ion concentration 5.0 wt%), and allowed to stand under sunlight for 3 hours. When the sodium ion concentration of the aqueous sodium chloride solution after standing was determined by cation chromatography, it was found to be 4.8% by weight. From this result, when using a layer of a mixture of titanium oxide particles and resin instead of the semiconductor photocatalyst film, the adhesion between the titanium oxide and the current collector is not sufficient, the conductivity is remarkably low, It was found that the function as an ion adsorption device cannot be exhibited unless a sensitizer such as a dye is present.

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Ion adsorber 10 Light, such as sunlight 11 Semiconductor photocatalyst film | membrane 12 Current collector 13 Electrolyte adsorptive conductive material 14 Photovoltaic electrode 15 Housing 16 Current collector (counter electrode)
17 Loads such as conducting wires 18 Electrolytic adsorptive conductive material

Claims (5)

Comprising a photo-excited emission electrode comprising a current collector, a semiconductor photocatalyst film adhered to one side surface of the current collector, and an electrolyte-adsorbing conductive material adhered to the other side surface of the current collector . Self-powered ion adsorption device that adsorbs ions in solution . The self-power generation ion adsorption device according to claim 1, further comprising a counter electrode. The self-power generation type ion adsorption apparatus according to claim 2, wherein the counter electrode is an adsorption electrode formed by bringing a current collector and an electrolyte-adsorbing conductive material into close contact with at least one side surface of the current collector. A method for removing an ionic substance using the self-powered ion adsorption apparatus according to any one of claims 1 to 3 . The ion removal ability is recovered by releasing ions adsorbed on the semiconductor photocatalyst film or the electrolyte-adsorbing conductive material by discharging or applying a reverse voltage when the ion removal ability of the self-powered ion adsorption device is reduced. Item 5. A method for removing an ionic substance according to Item 4 .