JP2009190016A - Method for preventing and removing biofilm in electrolytic capacitor for water purification - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem occurring in an electrolytic capacitor type deionization technique, which is an energy-saving water purification method effective in reducing a total dissolved solid (TDS) wherein ions are adsorbed or desorbed by an electrode of a flow-through capacitor (FTC), the problem that the electrode performance is deteriorated due to microorganisms in water being a biofilm (slime etc.), contaminant gases or an oxide layer on the electrode, and to prevent and remove without interruption of the operation. <P>SOLUTION: The method solves the problem at a low cost. The gas is discharged with a pump. The biofilm is sterilized immediately before the FTC treatment with electrolyzed ozone produced directly from the water to be treated, and then an adsorbed substance is removed by converting the polarity of the FTC electrode into an anode. When the FTC electrode is initialized, the water to be treated is inexpensively purified using no costly films nor chemicals at all. The generation of the biofilm is also prevented because the ozone is always produced in the FTC. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for preventing contamination of an electrode, which is a component of a capacitor, while using electric double layer capacitor technology to make contaminated water or seawater pure water. Specifically, the present invention relates to the removal of biofilms (biofilms) adhering to the electrode surface that hinder the ion removal rate of capacitors and polluted gases.

There are many ways to reduce ionic contaminants in purifying water. Filtering methods such as filtration membranes and reverse osmosis pressure, ion exchange, resin bed absorption, and the like. All of the above methods use chemicals that are harmful to the human body and the environment to clean and regenerate the membrane and resin, so secondary contamination is a problem. The membrane and the resin are discarded when the original effect is lost, and the processing becomes a problem. In contrast, deionization (CDI) technology using capacitors can reduce the TDS (total dissolved substance concentration) of treated water without using any membranes or chemicals. What is necessary for CDI is an ion adsorption medium and a direct current, which is realized by a flowing water capacitor (FTC). An electrode is made of an adsorbing material such as activated carbon having a large surface area and a metal substrate that becomes a current collector such as titanium, an FTC is assembled, and CDI water purification is performed by repeatedly charging and discharging the FTC. When the time comes for the FTC electrode to lose its original function, its parts, housing, accessories, and expensive titanium metal are all reused and no environmental pollution occurs. In order to cope with a large amount of water treatment capacity such as industrial wastewater, FTC requires a large electrode surface area and a high ion removal capacity. In pursuit of the size of the surface area, many obstacles can occur in the ion adsorption of the FTC electrode. They are electrical shorts, electrical or ion transfer resistances, and are classified as degradation of FTC electrode performance. Electrical shorts can be avoided by FTC design and material selection. When an unintended large current is applied in FTC operation, water generates gas by electrolysis. Although this gas adheres to the electrode or is dispersed in water, this becomes an obstacle to ion adsorption or ion movement, and the performance of the FTC is reduced as ion resistance. However, gas generation can be easily removed by providing a space on the surface of the running water and slowly sucking in and escaping the gas. On the other hand, because of the microorganisms in the water, the surface of the FTC electrode cannot be spared from the generation of biofilm. A biofilm is a structure formed by microorganisms, such as dental plaque and kitchen slime. Within a biofilm, there are various types of microorganisms from anaerobic bacteria to aerobic bacteria. The FTC surface is no exception. Biofilms adhere to the surface of objects by static electricity and hydrogen bonds. Surface area per volume of the FTC module, laminar water passing through the electrodes, and static electricity charged to the FTC are all favorable conditions for biofilm culture. Furthermore, with calcium and magnesium ions present in the water, the biofilm forms a layer as a thick insulator on the surface of the FTC electrode on the cathode side as a mineral adhesion medium. This not only hinders the ion adsorption of the FTC electrode, but also combines the biological biofilm with the mineral mineral, leading to a decrease in the electrical capacity of the FTC module and a malfunction of the electrode itself.

How to treat biofilm is an important issue in water treatment technology. Other techniques, such as using reverse osmosis and electrodialysis membranes, also have biofilm problems. If the pores of the membrane are clogged with biofilm or the like, the water purification ability is completely lost. In addition, since pipes, boilers, and metal parts corrode due to biotechnology, deterioration of air conditioning and water storage devices is a problem. Therefore, control of bacteria and mineral concentration are important. Physical, chemical, and electrolysis methods have been proposed as countermeasures and prevention methods for biofilm formation. US Pat. Nos. 6,821,480 and 6,830,661 (steam) and 7,250,619 (ultraviolet) are physical methods for sterilizing bacteria and the like by steam and ultraviolet rays. There are also three types of chemicals. Antibiotics, insecticides, surfactants. In US Pat. No. 4,929,365, nutrients are used to activate chlorine oxide as an oxidant for sterilization of bacteria. US Pat. No. 7,165,561 proposes biofilm removal by mixing enzyme and surfactant. Yes. In US Pat. No. 6,551,518, corona discharge ozone generation generates chlorine dioxide in water to sterilize. Since ozone is stronger than chlorine dioxide, there is an example in which ozone is used to control the water quality of the cooling tower (US Pat. No. 6,086,772). There are more patents for electrolysis than the other two methods. US Patent 5,312,813 uses low series current for sterilization. US Pat. No. 5,462,644 utilizes the antibiotic action of a surfactant. In US Pat. No. 6,533,942, bactericidal ions of Ag ⁺ and Cu ²⁺ are generated. In US Pat. No. 6,878,287, a bactericidal solution is used. Rather than generating bactericidal chemicals, a direct current alone is more effective in removing biofilms. This is because the electrode oxidizes the biofilm by switching the electrode pole. At this time, the electrode is an anode. Electrode switching prevents biogeneration in the cathode chamber in US Pat. No. 4,115,225. In US Pat. No. 5,589,050, deposits on the electrodialysis membrane are removed. Bacteria and biofilms cannot resist physical treatments such as steam or ultraviolet rays, but they consume energy and take too much time, so they are practical for treating industrial wastewater in real time during running water. There is a problem from the point of view. Both chemical and electrolysis approaches add or produce bactericidal substances. Of the sterilizing substances, ozone is the most powerful and effective.

In general, ozone is generated by corona discharge or silent discharge and is used for sterilization of waste water. In the discharge process, pure water oxygen or dry clean air (condensation generation minus 60 degrees Celsius or less) is used, and an irritating trivalent gas is generated by a dielectric discharge gap of high voltage alternating current (6,000 to 20,000 kilovolts). Nitrogen is also decomposed simultaneously with oxygen decomposition, so that discharge of air generates harmful gases of nitrogen oxides. Furthermore, ozone gas must be melted as fine bubbles in the water to be sterilized. The medium gas, the transport of generated ozone, melting, cooling of the dielectric generator, prevention of harmful gas leakage, etc. are all system control, so the corona discharge type is large and expensive, and the operation and maintenance costs are also high. Compared to this, the electrolytic ozone generation method for electrolyzing water is a relatively new technology, but a pair of electrodes are put in water and ozone is produced with a direct current of 24 volts or less. Since water is a precursor of ozone and becomes gaseous in water, it can solve the problems and limitations caused by corona discharge. Of course, there are problems with electrolytic ozone. The material of the ozone electrode (anode) and the structure of the cell. There are many patents for electrolysis ozone, and US Pat. No. 5,987,407 is typical. This patent requires an ion exchange membrane so that substances generated from the anode and cathode are not mixed in the electrolysis cell. After generating ozone gas, mix with treated water. The ion exchange membrane is not only expensive, but also the membrane is contaminated by particles and the like. Furthermore, this patent is not environmentally acceptable because it uses lead oxide as the material. Other ozone-related patents use platinum (US Pat. No. 6,984,295) or conductive diamond films (US Pat. No. 7,285,194) as catalysts. These catalyst materials are too expensive to satisfy the ozone generation amount and are not practical. In the present invention, the use of materials that are economical and have high ozone generation efficiency and the simple and high-performance cell structure control the generation of microorganisms that occur in the FTC desalting process.

    The primary objective of the present invention is to escape gas from the water that is processed by the FTC form of CDI technology. The FTC (flowing water passage type capacitor) is a module in which a plurality of monopolar or bipolar electrode plates are stacked to pass a direct current. Only a few electrodes are monopolar and the other electrode plates are monopolar. The cause of gas generation is electrolysis of water that contacts the electrode plate in the FTC when energized. Here, hydrogen gas is generated at the cathode and oxygen is generated at the anode. Both gases are difficult to dissolve in water and tend to exist as gases. In order to allow the gas to escape quickly, the water to be treated is injected by pushing it up from the bottom of the FTC, creating a space on the water surface above the FTC. At the same time, an outlet for venting is provided at the top of the module. A method of quickly discharging the gas in water into the air using a fan or a venturi tube will also be added.

The second purpose is to sterilize the treated wastewater with ozone before water treatment by CDI technology, but use low-cost materials other than rare metals (Ru, Pt, Ir and Pd) as anode materials for ozone generation. It is to use. A thick film of tin dioxide doped with bimetal (M-SnO ₂ , M = Sb and Ni) is employed as the electrode plate catalyst. This tin oxide film is formed on the titanium substrate using pyrolysis by using tin, stannic chloride, antimony chloride (IV), and nickel chloride (Il) as low-cost doping materials. Titanium is selected because it is resistant to the severe oxidant corrosion of ozone generation. In addition, the titanium dioxide oxide film on the titanium surface functions as a connection between the titanium substrate and tin dioxide, thereby extending the life of the coating. Although the deposition of a tin oxide film on a titanium substrate takes time, the oxide film itself grows easily on titanium, so there is no limitation on the deposition area and shape. Therefore, the anode can correspond to individual specifications according to the sterilization needs.

A third object is to provide a simple and highly efficient electrolysis cell capable of dynamically changing the sterilizing ability according to a desired treatment amount. A titanium substrate coated with M-SnO ₂ is used as the anode and a stainless steel plate as the cathode. Both electrodes make several small holes in the plate surface to allow water to pass through. The anode and the cathode are arranged opposite to each other, and a plastic screen is sandwiched between them or an electrode is fixed to form a gap. In this way, a plurality of pairs of electrode plates are used to satisfy the required processing capacity. The shape may be a cylindrical shape that allows treated water to pass, or an open type that is directly immersed in water. Oxidants are generated directly in water, eliminating the need to carry ozone and to dissolve in water. The method of the present invention is safe because there is no risk of gas leakage and nitrogen oxides are not generated. Furthermore, since only the electrode pair and the power source are required for ozone generation, it can be provided with very small equipment. The ozone produced here is an ultrafine bubble, so an artificial bubbler is not necessary. In addition to the immediate sterilizing effect of ozone, another sterilizing gas is produced as a secondary product in the generated gas. Hydrogen peroxide from the cathode reaction. The coexistence of ozone and hydrogen peroxide further improves the bactericidal effect in the process of accelerated oxidation (AOP). The electrolyzed ozone of the present invention disinfects microorganisms in water, and at the same time, the biofilm formed on the surface of the electrode in the FTC is depolymerized, that is, chemically decomposed.

In addition, the next purpose of the present invention is to prevent the biofilm formation on the surface of the FTC electrode in advance and to chemically decompose the biofilm already stuck to the surface, which alternately converts the polarity of the electrode during operation. It becomes possible by doing. The CDI operation is to charge and discharge the FTC electrode. First, the electrode is charged to adsorb ions in the water. Then, in order to clean the electrode surface saturated with the adsorbed ions, the process proceeds to the discharge process. Following this regeneration process, the electrode is recharged to enter the desalination cycle. Each time the cycle changes, the polarity of the electrodes is switched, which is done by switching the terminals of the unipolar electrodes connected to the external power supply. Here, the monopolar electrode functions as an anode, and the anode side of the internal bipolar electrode also becomes the anode. Since it is an anode, the oxidation reaction eliminates the adhesion of microorganisms, and can prevent the electrode plate adhesion of inorganic pollutants such as Mg ²⁺ and Ca ²⁺ . In the oxidation process, the bond between carbon and nitrogen is cut off to promote biofilm degradation. On the other hand, the already attached mineral binder is decomposed by oxidation of the anode.

Interest in water, which is a precious resource, has increased due to environmental issues and the social background of energy conservation, and the securing of drinking water and the recycling of water have become important. There are two types of water pollution, one is ionic and the other is neutral. The former is removed electrostatically and the latter is often ionized and can be decomposed by oxidation. The capacitive deionization (CDI) method is a water treatment technique that removes ionized contaminants from various water-soluble liquids. The basis of the CDI water treatment method is a through-flow water capacitor (FTC). TDS (total dissolved solids) is removed from the water using CDI technology using a DC power supply and a charge / discharge cycle. At this time, it is not necessary to carry out pretreatment such as dilution in advance with water, and since there is no use of chemicals or expensive membranes, it is an excellent method that does not cause secondary contamination. Furthermore, since the power consumed by the FTC is recovered and reused at the time of discharging, the CDI method is energy saving. The FTC material has less adverse effects on the environment than filtration membranes and ion exchange membranes. In addition to electrode performance and cell configuration requirements, the way the FTC module operates also affects cost, performance and reliability. During FTC operation, the electrode must be kept in an optimal state and the factors that interfere with ion removal near the electrode must be controlled. As the name suggests, the FTC functions like that in a capacitor structure. The difference is that in the case of a capacitor, the electrolytic solution is sealed, but in FTC, the water to be treated is the electrolytic solution, but the water passes through.

FIG. 1 illustrates an FTC module, in which a plurality of electrodes 10 are accommodated between a cover plate 12 and a bottom plate 14 and fixed with bolts and nuts. The two upper and lower polypropylene cover plates securely fix the electrode group with metal rings. Water drains from 100 inlets to 110 outlets so that the treated water effectively contacts the electrodes. The electrode stack 10 can stack any number of electrode plates without any limitation. In this FTC, an electrode having a diameter of 30 centimeters was used. The electrode has activated carbon attached to the surface of titanium. Activated carbon is made from coal, resin, coconut shell, pitch, and the like. Before the activated carbon coating, the titanium plate is perforated with a special pattern. Holes are drilled in an alternating pattern with adjacent upper and lower electrodes so that the water flow is zigzag. Only a few of the electrode groups are designed to physically connect an external power source. In FIG. 1, two upper and lower electrodes of the electrode group 10 are connected to the positive electrode of the external power source by the positive electrode (A). Similarly, the middle electrode is connected to the negative electrode of the power source by the negative electrode (C). These three electrodes are monopolar electrodes and have only one pole. The other electrode plate of the electrode group 10 can also be selected as a monopolar electrode. The positive electrode shares the positive electrode of the power source, and the negative electrode shares the negative electrode of the power source. The other intermediate electrodes of the electrode group 10 have a negative electrode as a whole, and become two sub-electrode groups that are paired with the positive electrode. Each sub-electrode group is composed of the same number of electrode plates, and all the intermediate electrodes are not physically connected to the external power source, but current from the power source is transmitted. When a direct current from the power source flows through the positive electrode and the negative electrode of the sub-electrode group, the surface of the first intermediate electrode facing the positive electrode side becomes negative due to the current and water conduction. Due to this sensitivity, the back surface of the first intermediate electrode becomes positive. Similarly, the other intermediate electrodes have different polarities on the front and back surfaces. Therefore, the intermediate electrode is bipolar, and each sub-electrode group is connected in series with two monopolar electrodes and a bipolar electrode existing therebetween.

Although CDI technology utilizes low voltage DC power, water is easily electrolyzed by the electric field in the FTC module. The result of water electrolysis can be confirmed by the decrease in pH after the treatment. During the CDI process, hydrogen protons (H ⁺ ) are generated by the generation of oxygen at the anode as per equation.
2H ₂ O → O ₂ + 4H ⁺ + 4e 1
On the other hand, hydroxide ions (OH ⁻ ) are generated along with hydrogen generation at the cathode.
_{2H 2 O + 2e → H 2} + 2OH - 2
As shown in both equations, hydrogen is generated in an amount twice that of hydroxide ions with respect to electrolyzed water molecules. As a result, after neutralizing the hydroxide ions, the remaining hydrogen protons lower the pH of the water during the CDI treatment. Although it depends on the CDI treatment time and operating voltage, the pH concentration changes three times compared to before treatment. However, the generated gas does not cause a fire. On the other hand, if the gas is in water, gas contamination remains due to interference with FTC ion removal. The specific measure of the present invention for removing the gas contamination is solved by providing a space inside the cover plate 22 of the FTC module as shown in FIG. There are two distribution channels in the FTC module. Water flow and gas flow. Water enters through the bottom cover intake 200, passes through the electrode stack 20, and is discharged to the outside from two locations on the side. At the port 220, the water to be treated is sent, and the water that requires repeated CDI treatment is sent from the port 230 to the next FTC module. Since the upper space portion is higher than the water surface, the air or gas in the water is collected in the space portion by the movement of the air venting fan 280 and discharged. By installing a Venturi tube at port 280, the same purpose can be achieved without using power (US Pat. No. 4,603,619). The FTC electrode is saturated due to the adsorption of ions. In this case, the FTC is discharged to release ions from the electrode and refresh. At the time of discharging the FTC, the inside of the FTC module is rinsed with clean water to discharge ions. Finally, compressed air is sent from the port 281 to blow off the remaining moisture. This gas also escapes outside the FTC. By flowing water from the bottom to the top of the FTC module, residual gas can be effectively discharged, and this flow can increase the amount of water that touches the FTC electrode. When flowing from above, there is a high possibility of non-uniformity in contact with the electrodes.

In addition to ionic contamination, microorganisms such as bacteria and germs are also mixed in the sewage. The generation of biofilm can be seen on the cathode side of the FTC just by charging and discharging the FTC several times. That is, a biofilm is produced only on the negative electrode plate and the negative electrode side of the bipolar electrode. The reason why the biofilm is generated immediately is that microorganisms are electrostatically dielectrically applied to the electrode by the electric field generated in the FTC, and the reduction of the cathode helps the generation. Naturally, the non-conductor adsorbs on the electrode, so that the ion adsorption performance of the FTC decreases. If the cathode becomes non-conductive, the paired anode will also fail. Since the electrode stack of FIG. 1 has a bipolar electrode as a connector and a plurality of electrodes are connected in series, the entire stack does not function if the cathode malfunctions. Therefore, the microorganisms in the water should be removed before CDI treatment. Ozone is the most ideal medium for water treatment disinfectants. Ozone brings oxidants directly to the cell walls and nucleic acids of microorganisms, destroying the cell walls. In the water after the microorganisms are destroyed, the causative substance of the biofilm is removed. However, the conventional ozone generation technology (corona discharge or silent discharge) is expensive and expensive to maintain. The raw toxic gas is also needed. However, electrolysis ozone generation does not have the above-mentioned problems. If the anode material has an inexpensive and high performance catalyst, electrolysis ozone generation can accommodate any amount of ozone generation of any scale.

The substance for generating ozone of the present invention is tin dioxide (SnO ₂ ). Pure tin dioxide is an n-type semiconductor and has a forbidden bandwidth of 3.5 eV, but has the following properties. (1) It is chemically and electrochemically stable, (2) its conductivity is increased by mixing impurities, and (3) its oxygen overvoltage is high. This last property is important for electrolysis ozone generation. Since the oxygen overvoltage of tin dioxide is 0.6 volts higher than that of platinum, it can be said that tin dioxide is more efficient if the other conditions are the same. In addition, oxidized materials are much cheaper than precious metals. Although tin dioxide has been used in wastewater treatment in the past (US Pat. Nos. 4,839,007 and 3,627,669), ozone generation and cell design needed improvement. Tin dioxide can be doped with impurities (Sb, Ni, Fe, Ru, Pt, Pd, Rh, Co, etc.). Similarly, nonmetal (F) or the like can be doped. Impurity generation efficiency and life of tin oxide can be improved by adding impurities. In addition to the adoption of the most common dopant, antimony (Sb), in the present invention, another metal nickel (Ni) was added to produce antimony and nickel-added tin dioxide, further increasing the stability of the catalyst. In general, the thick deposition of tin dioxide on a titanium substrate began with a solution of water and alcohol mixed with Sn, Sb and Ni. In terms of atomic weight, the substrate is mixed at a concentration of 0.2 to 2 percent. In the case of coating two kinds of elements, the solution containing the precursor material is coated a plurality of times, followed by thermal drying and thermal decomposition. The solution is converted to a thin film of tin dioxide with Sb—Ni added for every 100 ° C. to 300 ° C. coating and pyrolysis. This is repeated ten times and a thin film having a thickness of 20 to 30 μm is deposited on the titanium substrate. Finally, the titanium with the oxide film can be sintered and crystallized at 500 to 600 degrees Celsius over 30 minutes to 2 hours. Like other valve metals, oxides form naturally on titanium metal surfaces (titanium dioxide). Titanium dioxide protects the metal from corrosion and strengthens the adherence of tin dioxide to the titanium surface. The number of coating and thermal decomposition and its conditions greatly affect the reliability of the anode and the amount of ozone generated. A thicker coat results in a better performing anode. The inventors have discovered the unique properties of the anode with tin dioxide with antimony and nickel addition.
1. The coating of tin dioxide with antimony and nickel on titanium is independent of area and shape.
2. No electrolysis or source gas is required. The water to be treated becomes a precursor of ozone.
3. Using titanium as the anode and the pair of cathodes using stainless steel, ozone can be generated from the treated water as a raw material.
4). There is no need for an ion exchange membrane between the anode and the cathode to increase the amount of ions generated. This membrane is essential when platinum is used for the anode.
5. The ozone bubbles generated here are extremely fine.

In the present invention, as shown in FIG. 3, an ozone generation cell using an anode made of tin dioxide added with antimony and nickel was designed. In this figure, three anodes 31, 33, and 35 are used for the passing water ozone generator. The cathodes 32, 34, and 36 are housed in the housing 320. In FIG. 3, the anode and cathode support walls are made to coincide with the wall surface of the housing 320 for simplification. All the anodes are connected in parallel with the power line A. Similarly, the cathode is connected in parallel with the power supply line C. The two power supply lines A and C are connected to the positive electrode and the negative electrode of the power supply 340. Thus, all electrodes of the ozone generator receive equal energy from the power source 340 as monopolar electrodes. Electrolytic ozone is a low voltage but requires direct current power, so it uses an electric double layer capacitor (EDLC), also known as a supercapacitor, to supply current. EDLC accumulates a large current and can release the current instantly. The greater the current, the greater the amount of ozone. The ozone generator of FIG. 3 can achieve any amount of performance depending on the design. It depends on the combination of electrode configuration, EDLC power, power supply scale, and power supply pulse width modulation (PWM). In FIG. 3, the water stream flows from the upper part 300 to the lower part 310 through the electrodes. However, in the actual ozone generation process, it is more efficient to push the water flow from the lower part to the upper part as in FTC of FIG. In FIG. 3, all the electrodes have a plurality of holes having the same diameter, which is the same as FIG. Further, the actual generator electrode gap is much smaller than shown. Between the anode and cathode (not shown in the figure), a non-conductive ozone-resistant sheet made of mesh, net, screen, etc. made of polypropylene, polyethylene, neoprene, nylon, polytetrafluorethylene, etc. Insert as a gap. Alternatively (illustration is omitted), measures may be taken with nonconductors to prevent electrical shorting and at the same time secure the necessary electrode gap. The electrode gap has an interval of about 0.5 to 5 millimeters to ensure a water flow, and the ozone generation rate is also efficient. In addition to the flowing water pores, the electrode plate may have a shape such as a mesh, a net, or a screen. Using the methods of vapor deposition, pyrolysis and sintering, the Sb—Ni doped SnO ₂ / Ti film is firmly fixed on the electrode plate. The ozone generator of the present invention can be stored in the housing of FIG. Or, even without a housing, the electrode pair and DC power supply alone can serve the purpose. When there is no housing, it can be directly immersed in the treated water, or can be incorporated in the course of the passage. In that case, the number of electrodes may be increased or decreased according to the generation amount. In order to generate ozone, all that is needed is an electric power source in addition to the electrode set. As mentioned earlier, this DC power supply is compact and lightweight consisting of EDLC, power supply and control circuit. The power source may be anything such as a dry battery, secondary battery, solar, 100 volt outlet.

In FIG. 3, since the anode and the cathode are not separated and sealed, oxygen and ozone emitted from the anode react with hydrogen on the cathode side to cause decomposition of ozone. From the viewpoint of water sterilization, it is not necessarily negative, but it is beneficial. This is because hydroxy radicals (● OH) and hydrogen peroxide radicals (● O ₂ H), which are stronger oxidants than ozone, are generated. Actually, the relationship between the mass charge in the MS spectrum of gas phase chromatography / mass spectrometry (GC-MS) was investigated for ozone water in FIG. This mass / charge peak confirms the presence of hydrogen peroxide. The chemical formula is as follows.
2O ₃ + H ₂ → H ₂ O ₂ + 2O ₂ 3
The accelerated oxidation method (AOP) occurs in the coexistence of ozone and peroxidation flutes, and sterilization is more effective than ozone alone. Another advantage of ozonolysis is that the generation method of FIG. 3 consumes substantially all of the generated ozone, so there is no need for a residual gas removal scraper. Because it is minute, it reacts with microorganisms and organic pollutants instantly. Compared to corona discharge ozone generation, it is also an advantage that there is no need to carry gas from the discharge tube.

Substances such as ozone and hydrogen peroxide sterilize microorganisms by oxidation reaction. Since the anode also provides an oxidation reaction, biofilm, Ca ²⁺ and Mg ²⁺ based scales (oxide layers) are not observed on the anode. In the biofilm and scale prevention of the present invention, the roles of the anode side and the cathode side of the FTC electrode are all interchanged. As described above, since the CDI water treatment is to repeatedly charge and discharge the FTC module, the electrode works as follows.
1. Charging mode: A low voltage current is passed through the FTC electrode to create an electric field and absorb ions in the water. Ions are adsorbed on the FTC through which the current passes, and the water is desalted to become fresh water and discharged out of the FTC module.
2. Discharge mode: When the FTC electrode is saturated by ion adsorption, the electrode discharges and stores energy in the EDLC. The FTC is rinsed with water, blown in air, and ready for the next cycle charging mode.
With each new charge mode, the polarity of the FTC electrode is reversed. In FIG. 1, the terminals of the monopolar electrodes of the electrode stack connected to the two poles of the power source are exchanged. When the polarity of the monopolar electrode changes, the polarity on both sides of the bipolar electrode also changes. At each polarity change, one side of each monopolar and bipolar electrode becomes the anode. Not only does the biofilm and the scale not adhere to the anode, but also the biofilm attached to the carbon on the electrode surface is broken by the electrode that has become the anode. The polarity conversion process of the FTC module can be automatically performed by using a logic controller or the like.

This will be described as Example 1. A stack as shown in FIG. 1 is prepared by arranging five electrode plates having a diameter of 30 centimeters. Each electrode is coated with activated carbon on the surface with a titanium plate. Use a pattern that has many holes on the surface but does not overlap the holes in the upper and lower plates. This is because water flows zigzag and passes through more electrode surfaces. As shown in FIG. 1, the five electrodes are firmly fixed by two cover plates, and only the two electrodes at the tip of the electrode amount are physically connected to an external power source. These two sheets are monopolar electrodes. The other three are bipolar electrodes that are connected to the entire stack in series without a cable. Two tap water samples are prepared and passed through this FTC for deionization and water softening purposes. One used pump pressure (less than 2 psi) and the other used no pump. The test conditions are as follows.
Amount of water: 10 liters Processing speed: 3.5 liters per minute Working voltage: 10 volts DC measured value: TDS
In the test, FTC charge and deionization were continuously performed by circulating sample water through an FTC (4 cells of 5 electrodes) module and a water storage tank. TDS was measured at regular intervals and the results are summarized in Table 1.
This data is plotted in FIG. Better results were obtained when the pump was used to vent the gas. If 80 ppm is the hardness for beverages, deionization with a pump has been processed twice as fast as without a pump. Moreover, it can be said that the former improved the quality of the treated water within the same treatment time. In either case, sample water need not be pretreated. During testing, the electricity used is less than 1 ampere, so CDI technology is energy saving.

Example 2 will be described. Measurement of ozone concentration in water is not easy because it quickly decomposes. Since the effects of oxidants are known, redox potential (ORP) is often used as an indicator. ORP measures the degree of antibacterial activity against microorganisms. Platinum or gold is used as the electrode, silver silver chloride electrode is used as the standard electrode, and the ORP probe measures dissolved oxidant in millivolts. OPR is measured in the range of -2,000 to +2,000 mV and correlates with the number of bacteria in the water. For example, water with an OPR of 600 mV means that the pathogenic bacteria in the water have been killed. At 800 mV it is an indicator that all microorganisms have been destroyed. The World Health Organization (WHO) has set 650 mV as the required level of virus inactivation for drinking water. The ORP measurement was used for ozone water generated from the anode of the present invention (Sb—Ni doped SnO ₂ on a titanium substrate). The ozonization conditions are as follows.
Anode: Sb—Ni doped SnO ₂ evaporated titanium substrate, 15 mm × 30 mm × 1 mm
Cathode: 306 stainless steel, 15mm x 30mm x 1mm
Electrode gap: 6-mm thick nylon net Power supply: 15V x 0.1A
Water: 400ml tap water ORP probe was sampled at regular time intervals and the data is displayed in Fig. 5. As indicated by the curve, the initial ORP value is negative, indicating that there are many reducing elements (such as hydrogen). As oxidants are generated, the ORP level is balanced around 1100 mV. This demonstrates that the anode electrode of the present invention generated sufficient ozone to sterilize the microorganisms in the water. At the same time, it was demonstrated that FTC biofilm formation was prevented.

Outline of FTC module Side view of FTC electrode stack, water flow, gas in / out Conceptual diagram of ozone generator for sterilizing treated water TDS data during FTC operation ORP measured value of ozone water when using the anode material of the present invention

Claims (4)

As a component of a flowing water capacitor (FTC) for removing ions in water:
(1) At least one anode electrode with a layer of ion adsorbing material on both sides and physical means connected to the main power supply;
(2) At least one cathode electrode with a layer of ion adsorbing material on both sides and physical means connected to the main power supply;
(3) At least one bipolar electrode located between the anode and the cathode described above. This bipolar electrode also has a layer of ion adsorbing material.
(4) At least one through-hole is formed on the entire surface of the anode, the bipolar electrode, and the cathode so that liquid can pass through them. A certain gap is provided between the anode and the bipolar electrode and between the bipolar electrode and the cathode.
(5) One power source (6) Upper cover plate with gas valve and liquid outlet (7) Bottom cover plate with liquid inlet (8) Two cover plates as described above and all electrode plates as described above Mechanical means for assembling a flow-through capacitor (FTC) by joining together (9) Charging at least one supercapacitor (10) for providing energy to the FTC module and storing energy discharged from the FTC module A circuit having a switch for turning on or off two or more supercapacitors for discharging, and (11) an electric circuit for recovering energy from the current returned from the FTC, and storing the energy in the supercapacitor Electric circuit (12) At least one detector (on-line measurement of liquid status) 3) At least one controller that controls on / off (charge / discharge swing) and energy recovery. (14) Before and after injecting the liquid to be processed into the FTC module, the liquid is oxidized and sterilized in situ. Electrolytic ozone generator for The ion adsorbent used in the FTC according to claim 1 is activated carbon selected from the group of precursors including coal, resin, coconut shell and pitch. The gas valve used in the FTC according to claim 1 is prepared to expel the gas of the FTC module or to extract the gas. The anode of the ozone generator used in the FTC according to claim 1 is used by coating a titanium substrate with tin dioxide doped with antimony and nickel.