Heavy water separation catalyst and method for producing same, heavy water separation cell, and heavy water separation device

Abstract

To provide a heavy water separation catalyst having a high separation factor α and a heavy water separation apparatus.SOLUTION: The catalyst for separating heavy water contains γ -FeOOH. The heavy water separation device 1 includes an anion exchange membrane 4, and an anode catalytic layer 6 and a cathode catalytic layer 8 provided on both sides of the anion exchange membrane 4, respectively, and by using the above-described catalysts as the material of the cathode catalytic layer 8, it is possible to increase the separation factor α to 10 or more, the separation factor α indicating that the decomposition of H2O occurs more preferentially than the decomposition of HOD or HOT containing deuterium or tritium due to the isotopic effect.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a catalyst for heavy water separation using an anion exchange membrane and an AEM-type water electrolysis method, a method for producing the same, a heavy water separation cell, and a heavy water separation device. [Background technology]

[0002] Patent Document 1 proposes a method for electrolytically concentrating heavy water. In this method, an alkali is added to radioactive waste water containing deuterium and tritium to form an electrolyte. While circulating this electrolyte, electrolysis is performed between an anode and a cathode placed on either side of a diaphragm. This utilizes the phenomenon in which the decomposition reaction of HO occurs preferentially over the decomposition reactions of HOD and HOT due to the isotope effect, thereby concentrating deuterium and tritium in the electrolyte. The diaphragm is a cation exchange membrane made of a polypropylene film or a PTFE film. The anode is an Fe base or an Fe base plated with Ni, and the cathode is a Ni base or a Ni base coated with an active cathode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-29921 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method for electrolytic enrichment of heavy water disclosed in Patent Document 1, the separation factor α, which is a measure indicating that the decomposition of HO occurs preferentially over the decomposition of HOD and HOT due to the isotope effect, is relatively small, and there has been a demand for a higher separation factor α to improve the efficiency of electrolytic enrichment of heavy water. Increasing the separation factor α is also important to reduce the power consumption and costs required for electrolytic enrichment of heavy water. Separation factor α=([H] / [D]gas) / ([H] / [D]liq) [H] / [D]gas = H / D ratio in evolved gas [H] / [D]liq = H / D ratio in the electrolyte before electrolysis [Means for solving the problem]

[0005] In order to solve the above problems, the present invention has the following aspects. [1] A catalyst for heavy water separation according to a first aspect of the present invention is characterized by containing γ-FeOOH. According to this heavy water separation catalyst, when used as a material for the cathode catalyst layer in a heavy water separation device that performs AEM-type water electrolysis and has an anion exchange membrane and an anode catalyst layer and a cathode catalyst layer provided on either side of the anion exchange membrane, it is possible to increase the separation coefficient α, which indicates that the decomposition of HO occurs preferentially over the decomposition of HOD and HOT due to the isotope effect, thereby increasing the separation efficiency of heavy water and reducing the power consumption and costs required for electrolytic concentration of heavy water.

[0006] The mass of the γ-FeOOH relative to the total mass of the heavy water separation catalyst is not limited, but is preferably 10 to 100 mass%, and may be 20 to 90 mass%. In this specification, when "A to B units" is expressed, it means "not less than A units and not more than B units" unless otherwise specified.

[0007] [2] The catalyst for heavy water separation according to the second aspect is the catalyst according to the first aspect, characterized in that it is in the form of powder with an average particle size of 0.05 to 500 μm. The heavy water separation catalyst of aspect 2 has a large specific surface area, which makes it possible to enhance the efficiency of heavy water separation. The average particle size is not limited, but may be 0.5 to 100 μm, or 5 to 50 μm.

[0008] [3] A catalyst for heavy water separation according to a third aspect is the catalyst according to the first or second aspect, characterized in that it contains 0.1 to 50 mass % of a solid polymer electrolyte polymer (also called an ionomer, binder, or cast material). According to the catalyst for heavy water separation of Aspect 3, the inclusion of an appropriate amount of solid polymer electrolyte polymer facilitates the formation and shaping of the catalyst layer, and also ensures the ion permeability of the catalyst layer after membrane formation, thereby facilitating the enhancement of heavy water separation efficiency. The content of the solid polymer electrolyte polymer is not limited, but may be, for example, 1 to 30 mass %, or even 5 to 20 mass %, so as to enable shaping without inhibiting catalytic action.

[0009] [4] A method for producing a catalyst for heavy water separation according to a fourth aspect includes the steps of: mixing iron powder, water, and a solid polymer electrolyte polymer (also referred to as an ionomer, binder, or cast material) to obtain a mixture; and applying the mixture to the surface of a support and then heating the mixture in an oxygen-containing atmosphere at 60 to 150°C to oxidize the iron powder under relatively mild conditions, thereby producing a catalyst for heavy water separation containing γ-FeOOH. The heating time is not limited, but may be, for example, 0.1 to 1 hour. According to the method for producing a catalyst for heavy water separation of the fourth aspect, the surface of the iron powder can be appropriately oxidized to generate γ-FeOOH, and a catalyst for heavy water separation with a high separation factor α can be obtained.

[0010] [5] A heavy water separation cell according to a fifth aspect includes an anion exchange membrane, an anode catalyst layer and a cathode catalyst layer provided on either side of the anion exchange membrane, and an anode-side gas diffusion layer and a cathode-side gas diffusion layer disposed further outside the anode catalyst layer and the cathode catalyst layer, respectively, and the cathode catalyst layer contains the heavy water separation catalyst according to any one of the first to third aspects. According to the heavy water separation cell of the fifth aspect, it is possible to increase the separation coefficient α of heavy water in an AEM-type water electrolysis method using an anion exchange membrane, thereby increasing the separation efficiency of heavy water.

[0011] [6] A heavy water separation device according to a sixth aspect includes the heavy water separation cell of the fifth aspect, an anode disposed outside the anode-side gas diffusion layer, an anode-side flow path provided in the anode for circulating and supplying an electrolytic solution to the anion exchange membrane through the anode-side gas diffusion layer and the anode catalyst layer and for discharging oxygen gas produced by electrolysis of water in the electrolytic solution, a cathode disposed outside the cathode-side gas diffusion layer, and a cathode-side flow path provided in the cathode for discharging water that has permeated the anion exchange membrane and hydrogen gas produced by electrolysis of the water. According to the heavy water separation device of the sixth aspect, it is possible to increase the separation coefficient α of heavy water in the AEM-type water electrolysis method using an anion exchange membrane, thereby increasing the separation efficiency of heavy water.

[0012] [7] A series-type heavy water separator according to a seventh aspect is characterized in that it comprises a plurality of the heavy water separators according to the sixth aspect, with the anode-side flow paths of these heavy water separators connected in series. According to the series-type heavy water separator of the seventh aspect, the electrolyte in which heavy water has been concentrated in the first-stage heavy water separator can be further concentrated in the second-stage or subsequent heavy water separators, and therefore the height of the separation factor α has an exponential effect, making it possible to obtain high heavy water separation efficiency.

[0013] [8] A parallel-type heavy water separation apparatus according to aspect 8 is characterized in that it has a plurality of heavy water separation apparatuses according to aspect 6, and the anode-side flow paths and the cathode-side flow paths of these heavy water separation apparatuses are connected in parallel. According to the parallel heavy water separation apparatus of the eighth aspect, the amount of electrolyzed water that can be treated within a unit time can be increased, and therefore the efficiency of separating heavy water can be improved. [Effects of the Invention]

[0014] According to the heavy water separation catalyst, its manufacturing method, heavy water separation cell, and heavy water separation apparatus of the present invention, the heavy water separation catalyst contains γ-FeOOH, which makes it possible to increase the separation factor α, which indicates that the decomposition of HO occurs preferentially over the decomposition of HOD and HOT due to the isotope effect, compared to conventionally known catalysts, and to improve the separation efficiency of heavy water. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a heavy water separation apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a front view showing an example of a method for assembling the heavy water separation cell of the first embodiment. [Figure 3] FIG. 4 is a front view showing another example of the method for assembling the heavy water separation cell of the first embodiment. [Figure 4] FIG. 4 is a front view showing another example of the method for assembling the heavy water separation cell of the first embodiment. [Figure 5] FIG. 4 is a front view showing another example of the method for assembling the heavy water separation cell of the first embodiment. [Figure 6] FIG. 4 is a diagram showing a series-type heavy water separation apparatus according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a diagram showing a parallel heavy water separation apparatus according to a third embodiment of the present invention. [Figure 8] 1 is a graph showing the measurement results of the change in current density with respect to electrolysis time in a heavy water separation device according to an embodiment of the present invention. [Figure 9] 1 is a graph showing the measurement results of cell voltage versus current density in a heavy water separation device according to an embodiment of the present invention (denoted as Fe) and a heavy water separation device according to a comparative example (denoted as Ni, Pt / C). [Figure 10] 1 is a graph showing the measurement results of the separation factor α of heavy water in the heavy water separator of an example of the present invention (denoted as Fe) and the heavy water separator of a comparative example (denoted as Ni, Pt / C). [Figure 11]1 is a graph showing the measurement results of the ion current ratio corresponding to the breakdown of hydrogen gas components in a heavy water separation device according to an embodiment of the present invention (denoted as Fe) and a heavy water separation device according to a comparative example (denoted as Ni, Pt / C). [Figure 12] 1 shows measurement results showing the abundance ratio of Fe compounds in the cathode catalyst layers of an example of the present invention and a comparative example, where (a) shows a schematic representation of the measurement points on the outer surface of the catalyst particle, (b) shows a schematic representation of the measurement points inside the catalyst particle, (c) and (d) are graphs showing the results of measuring the abundance ratio of Fe compounds at positions (a) and (b) using pure Fe powder as a comparative example, and (e) and (f) are graphs showing the results of measuring the abundance ratio of Fe compounds at positions (a) and (b) using catalyst particles of an example of the present invention. [Figure 13] 1 is a graph showing a diffraction line profile by X-ray diffraction analysis in an example of the present invention. [Figure 14] FIG. 1 is a schematic diagram showing reaction pathways between various iron oxides. [Figure 15] 1 is an electron microscope photograph showing the surface properties of catalyst particles before an electrolysis experiment in a catalyst for heavy water separation according to an example of the present invention. [Figure 16] 1 is an electron microscope photograph showing the surface properties of catalyst particles after an electrolysis experiment in a catalyst for heavy water separation according to an example of the present invention. [Figure 17] 1 is an electron microscope photograph showing the surface properties of catalyst particles before an electrolysis experiment in a comparative example catalyst using a Ni compound. [Figure 18] 1 is an electron microscope photograph showing the surface properties of catalyst particles after an electrolysis experiment in a comparative example catalyst using a Ni compound. [Figure 19] 1 is an electron microscope photograph showing the surface properties of catalyst particles before and after an electrolysis experiment (no change) in a Pt / C catalyst of a comparative example. [Figure 20] 1 is a graph showing the separation factor α when electrolysis experiments were carried out using γ-FeOOH powder (Example 2), pure iron plate (Comparative Example 4), α-FeOOH powder (Comparative Example 5), and FeO powder (Comparative Example 6) as heavy water separation catalysts. [Figure 21]1 is a graph showing the results of measuring the X-ray count versus 2θ (Coupled Two Theta / Theta) by subjecting the γ-FeOOH powder (Example 2) before the electrolysis experiment to an X-ray diffractometer (XRD). [Figure 22] 1 is a graph showing the results of measuring the X-ray count versus 2θ when the catalyst of Example 2 after the electrolysis experiment was subjected to an X-ray diffractometer (XRD). [Figure 23] 1 is a graph showing the results of measuring the X-ray count versus 2θ when the α-FeOOH powder (Comparative Example 5) before the electrolysis experiment was subjected to an X-ray diffractometer (XRD). [Figure 24] 1 is an electron microscope photograph at 1000x magnification taken by using a scanning electron microscope of γ-FeOOH powder in a reagent state (Example 2). [Figure 25] 1 is a 1000x electron microscope photograph taken by a scanning electron microscope of γ-FeOOH powder (Example 2) supported on a gas diffusion layer before an electrolysis experiment. [Figure 26] 1 is an electron microscope photograph at 1000 magnifications taken by a scanning electron microscope of the catalyst of Example 2 in a state supported on a gas diffusion layer 12 after an electrolysis experiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, each aspect of the embodiment of the present invention will be described in detail. [Heavy water separation catalyst] A catalyst for heavy water separation according to one embodiment of the present invention contains γ-FeOOH (Lepidocrocite).

[0017] Iron oxides can be broadly classified into (1) iron oxide, (2) iron hydroxide, and (3) iron oxyhydroxide, and the following compounds exist: (1) Iron oxide FeO: Iron(II) oxide Fe3O4: Iron (II, III) oxide Fe2O3: Iron(III) oxide α-Fe2O3: α-iron(III) oxide β-Fe2O3: β-iron(III) oxide γ-Fe2O3: γ-iron(III) oxide ε-Fe2O3: ε-iron(III) oxide (2) Oxyhydroxide α-FeOOH: α-iron oxyhydroxide (Goethite) β-FeOOH: β-iron oxyhydroxide (Akaganeite) γ-FeOOH: γ-iron oxyhydroxide (Lepidocrocite) δ-FeOOH: δ-iron oxyhydroxide Fe5HO8·4H2O: Ferrihydrite (3) Hydroxide Fe(OH)2: Iron(II) hydroxide Fe(OH)3: Iron(III) hydroxide

[0018] The present inventors discovered that, among the iron oxides described above, γ-FeOOH (lepidocrocite) exhibits a particularly high separation factor α for heavy water in an AEM-type water electrolysis process using an anion exchange membrane, leading to the present invention. The heavy water separation catalyst of this embodiment may take the form of a powder, a granular or porous mass formed by agglomerating the powder, or a support in which the powder is supported on the surface of a carrier. Furthermore, this heavy water separation catalyst may contain one or more iron oxides other than γ-FeOOH (the above-described (1), (2), and (3)), iron compounds other than oxides, or small amounts of metals other than iron and their compounds.

[0019] The value of the separation factor α is defined by the following formula. It has been found that the catalyst for heavy water separation of the present invention has a higher value of separation factor α than conventionally known catalysts, and can achieve an excellent value of, for example, 10 or more. Separation factor α=([H] / [D]gas) / ([H] / [D]liq) [H] / [D]gas = H / D ratio in evolved gas [H] / [D]liq = H / D ratio in the electrolyte before electrolysis A separation factor α of 10 or more is an extremely high value, even when compared with the conventionally known heavy water separation factors α of other metals shown in Table 1, for example.

[0020] [Table 1] (Source: Electrochemical Reaction Operation and Electrolytic Cell Engineering, by Fumio Hinone (Kagaku Dojin Publishing, 1979)

[0021] This heavy water separation catalyst, when used as a material for the cathode catalyst layer of a heavy water separation device for AEM-type water electrolysis, can increase the separation factor α for heavy water, improve the separation efficiency of heavy water, and reduce the power and cost required for separating heavy water. The mass of γ-FeOOH relative to the total mass of the heavy water separation catalyst is not limited, but may be 10 to 100 mass% or 20 to 90 mass%. Furthermore, the average particle size of the primary particles of the heavy water separation catalyst is not limited, but may be powder with an average particle size of 0.05 to 500 μm.

[0022] When the catalyst for heavy water separation is a powder, the particles may contain metallic iron in the center of the particle, because when a catalyst for heavy water separation is produced by oxidizing metallic iron powder, unreacted metallic iron may remain in the center.

[0023] The catalyst for heavy water separation of this embodiment may contain 0.1 to 50 mass% of a solid polymer electrolyte polymer (also referred to as an ionomer, binder, or cast material) relative to the total mass of the catalyst, including the function of a binder to maintain the shape. Examples of the solid polymer electrolyte polymer include fluorine-based polymer electrolytes containing perfluorosulfonic acid, such as sulfonated tetrafluoroethylene-based fluoropolymer copolymers (trade name "Nafion" by Chemours), and hydrocarbon-based electrolyte polymers, such as sulfonated polyphenylene, alkylsulfonated polybenzimidazole, sulfonated polyethersulfone, and sulfonated polyimide. The content of the solid polymer electrolyte polymer in the catalyst for heavy water separation may be 1 to 30 mass%, or may be 5 to 20 mass%.

[0024] When an appropriate amount of solid polymer electrolyte polymer is contained, the catalyst layer can be easily formed and its shape can be easily maintained, and the ion permeability of the catalyst layer after membrane formation can be increased, which makes it easy to increase the electrolysis efficiency and the heavy water separation efficiency.

[0025] [Method of manufacturing a catalyst for heavy water separation] The method for producing the heavy water separation catalyst includes the steps of: mixing iron powder, water, and, optionally, an organic solvent such as alcohol, and, optionally, the solid polymer electrolyte polymer to obtain a mixture; and heating the mixture in a container or by applying the mixture to the surface of a support at 60 to 150°C in an oxygen-containing atmosphere for 0.1 to 1.0 hours. By oxidizing the iron powder in the presence of moisture under relatively mild conditions, the surface layer of the metallic iron, particularly, is oxidized to γ-FeOOH, producing a powdered heavy water separation catalyst. Figure 14 is a schematic diagram showing the types of iron compounds and their reaction pathways and crystal structures. It is clear that the selection of production conditions is important for obtaining γ-FeOOH.

[0026] According to this method for producing a heavy water separation catalyst, the iron powder can be appropriately oxidized from the surface toward the inside to produce γ-FeOOH, and a heavy water separation catalyst having a high separation factor α for heavy water can be produced easily and at a relatively low production cost.

[0027] The average particle size of the raw iron powder is not limited, but may be determined in accordance with the average particle size of the catalyst for heavy water separation. The oxygen concentration in the oxygen-containing atmosphere for oxidizing the iron powder is not limited, but is preferably 5 to 30% by volume, and may be, for example, air. The water is necessary to moderately promote the oxidation of the iron powder, and is preferably approximately 5 to 30% by mass of the iron powder weight. An organic solvent, such as an alcohol such as 2-propanol, is added to control the evaporation rate of the solvent and to facilitate uniform dispersion of the solid polymer electrolyte polymer in the mixture. The amount is not limited, but may be approximately 0.1 to 10% by mass of the iron powder weight. The heating temperature is not limited, but may be, for example, 80 to 140°C. The heating time is not limited, but may be 0.2 to 0.9 hours. The solid polymer electrolyte polymer may be in the form of a commercially available dispersion or solution.

[0028] The support may be the cathode-side surface of the anion exchange membrane 4 constituting the heavy water separation cell 2 described below, or the cell inner surface of the cathode-side gas diffusion layer 12. In this case, the formed cathode catalyst layer 8 is disposed sandwiched between the anion exchange membrane 4 and the gas diffusion layer 10. 2 to 5 show variations in the method of forming the anode catalyst layer 6 and the cathode catalyst layer 8. In the example of FIG. 2, the anode catalyst layer 6 is formed on the inner surface of the gas diffusion layer 10, and the cathode catalyst layer 8 is formed on the inner surface of the gas diffusion layer 12. In the example of FIG. 3, an anode catalyst layer 6 and a cathode catalyst layer 8 are formed on both sides of an anion exchange membrane 4, respectively. In the example of FIG. 4, an anode catalyst layer 6 is formed on the inner surface of the gas diffusion layer 10, and a cathode catalyst layer 8 is formed on the cathode side of the anion exchange membrane 4. In the example of FIG. 5, an anode catalyst layer 6 is formed on the anode side of the anion exchange membrane 4, and a cathode catalyst layer 8 is formed on the inner surface of the gas diffusion layer 12. Which of the methods shown in FIGS. 2 to 5 is to be adopted can be determined by taking into consideration the ease of application of the catalyst for heavy water separation to the carrier and the oxidation process, as well as the final selectivity coefficient γ.

[0029] [Heavy water separation cell] FIG. 1 is a block diagram showing a heavy water separation apparatus 1 for performing AEM-type water electrolysis, including a heavy water separation cell 2 according to one embodiment of the present invention. The heavy water separation cell 2 includes an anion exchange membrane 4, an anode catalyst layer 6 and a cathode catalyst layer 8 disposed on either side of the anion exchange membrane 4, and an anode-side gas diffusion layer 10 and a cathode-side gas diffusion layer 12 disposed further outward from the anode catalyst layer 6 and the cathode catalyst layer 8, respectively. The cathode catalyst layer 8 is a membrane formed from or containing the heavy water separation catalyst described above. Such a heavy water separation cell 2 can increase the separation factor α of heavy water, thereby improving the separation efficiency of heavy water.

[0030] The material of the anion exchange membrane 4 is not limited, but may be, for example, an AEM in which ion exchange groups such as ammonium and imidazolium cations are added to a hydrocarbon-based main chain skeleton such as polystyrene, polyethersulfone, polyphenylene, or a copolymer polymer to impart anion conductivity. Commercially available AEMs that can be used include Fumasep (product name of Fumatech), Amenion (product name of Ionomr), Sustainion (product name of Dioxide Materials), and A201 (product name of Tokuyama).

[0031] The thickness of the anion exchange membrane 4 is not limited, but may be 5 to 500 μm. Within this range, good ion exchange performance can be obtained while maintaining sufficient mechanical strength. If the anion exchange membrane 4 is too thin, the mechanical strength may be insufficient, and if it is too thick, the ion exchange performance may be relatively reduced. More preferably, the thickness of the anion exchange membrane 4 may be 10 to 100 μm.

[0032] The anode catalyst layer 6 is not limited to any particular material, but may be a membrane formed by dispersing powders of IrO, Pt / C, Ru / C, or the like in a solvent together with a solid polymer electrolyte polymer as a binder, and solidifying the resulting dispersion. The solid polymer electrolyte polymer may be the same as the solid polymer electrolyte polymer used in the cathode catalyst layer 8 described above.

[0033] The cathode catalyst layer 8 is a membrane formed of the above-mentioned heavy water separation catalyst. There are no limitations on the thickness, but it is preferably 50 to 1000 μm, and more preferably 100 to 500 μm.

[0034] The gas diffusion layers 10 and 12 are porous sheets that are electrically conductive and allow gas to pass through, and may be formed of, but are not limited to, carbon paper, carbon cloth, titanium sheet, or the like. As a result, on the anode side, the electrolyte solution 25 supplied through the flow paths 17 and 18 of the bipolar plate 14, which will be described later, passes through the gas diffusion layer 10 and the anode catalyst layer 6 and is supplied to the anion exchange membrane 4. The electrolyte solution 25 containing oxygen gas generated in the anode catalyst layer 6 passes through the gas diffusion layer 10 and is collected via the flow paths 17 and 18 of the bipolar plate 14. On the cathode side, water flowing through the anion exchange membrane 4 is converted into hydrogen gas and OH gas in the cathode catalyst layer 8. - After electrolysis, the generated hydrogen gas and a small amount of water are discharged to the outside of the heavy water separation cell 2 through the gas diffusion layer 12 and the flow paths 18, 17 of the bipolar plate 16, which will be described later. The gas diffusion layers 10, 12 may be made to support corresponding catalysts, respectively, to form the anode catalyst layer 6 and the cathode catalyst layer 8 in a porous state.

[0035] [Heavy water separation equipment] The heavy water separation device 1 of this embodiment comprises the aforementioned heavy water separation cell 2, a bipolar plate 14 (anode) arranged on the outside of the anode-side gas diffusion layer 10, and a bipolar plate 16 (cathode) arranged on the outside of the cathode-side gas diffusion layer 12. In the anode-side bipolar plate 14, a number of slit-shaped flow paths 18 are formed at positions where they abut against the gas diffusion layer 10, and flow paths 17 are formed which communicate with these slit-shaped flow paths 18, with an electrolyte inlet 22 formed at the lower end of the flow path 17 and an oxygen outlet 28 formed at the upper end of the flow path 17. In the cathode-side bipolar plate 16, a number of slit-shaped flow paths 18 are formed in parallel at positions where they abut against the gas diffusion layer 12, and flow paths 17 are formed which communicate with these slit-shaped flow paths 18, and a hydrogen outlet 40 is formed at the upper end of the flow path 17.

[0036] An electrolyte tank 26 is connected to the electrolyte inlet 22 of the bipolar plate 14 via a pump 24, and the electrolyte 25 in the electrolyte tank 26 is pressurized by the pump 24 and supplied from the electrolyte inlet 22 through the flow path 17 in the bipolar plate 14 and through the flow path 18 to the gas diffusion layer 10. The electrolyte 25 that has flowed into the gas diffusion layer 10 flows through the anode catalyst layer 6 to the anion exchange membrane 4, and some of the water flows to the cathode side through the anion exchange membrane 4. On the other hand, OH that has migrated from the cathode side through the anion exchange membrane 4 - The ions are electrolyzed in the anode catalyst layer 6 to generate oxygen gas, which passes through the gas diffusion layer 10, the flow paths 18 and 17, and is discharged from the oxygen outlet 28. The remainder of the electrolyte 25 is also discharged from the oxygen outlet 28.

[0037] The electrolytic solution 25 is obtained by dissolving electrolytes such as KOH, NaOH, and Ba(OH)2 in raw water containing heavy water and tritiated water, and the concentration is not limited, but may be about 0.01 to 5.0 M to maintain device durability while increasing electrolysis efficiency, or may be 0.1 to 1.0 M. The temperature of the electrolytic solution 25 during electrolysis is not limited, but may be 5 to 50°C, or may be 10 to 30°C.

[0038] The oxygen outlet 28 is connected to a gas-liquid separator 32 via a conduit 30, and the heavy water concentrated water mixed with oxygen gas discharged from the oxygen outlet 28 is supplied to the gas-liquid separator 32, where the oxygen gas and heavy water concentrated water 33 are separated. The heavy water concentrated water 33 accumulated in the gas-liquid separator 32 is discharged from an outlet 36 and returned to the electrolyte tank 26. Water is added to the electrolyte tank 26 to dilute the concentrated electrolyte. Oxygen gas is discharged from a conduit 34 of the gas-liquid separator 32 to the next process.

[0039] On the other hand, on the cathode side, the hydrogen outlet 40 of the bipolar plate 16 is connected to a gas-liquid separator 44 via a conduit 42. The hydrogen gas and water discharged from the hydrogen outlet 40 enter the gas-liquid separator 44 through the conduit 42, where the hydrogen gas and water are separated, and the accumulated water is discarded or reused. The hydrogen gas is sent to the next process through a conduit 48. In the example of FIG. 1, a quadrupole mass spectrometer 50 is connected to the end of the conduit 48, and the amounts of deuterium and tritium in the separated hydrogen gas are measured. The smaller the amounts of deuterium and tritium measured by the quadrupole mass spectrometer 50, the larger the separation factor α of the cathode catalyst layer 8.

[0040] The positive electrode of a power supply 20 is connected to bipolar plate 14, and the negative electrode of power supply 20 is connected to bipolar plate 16. When current is applied from power supply 20, the following reaction (1) occurs mainly in anode catalyst layer 6 on the anode side, generating oxygen gas, and the following reaction (2) occurs mainly in cathode catalyst layer 8 on the cathode side, generating hydrogen gas. [Anode reaction] 4OH - → O2 + 2H2O + 4e - (1) [Cathode reaction] 4H2O+4e - → 2H2+4OH - (2)

[0041] The reaction (2) proceeds selectively for HO, which is composed only of hydrogen, and less selectively for DHO, DO, THO, TDO, and TO, which contain deuterium or tritium, in that order. In particular, the cathode catalyst layer 8 using the heavy water separation catalyst of the present invention can increase the separation factor α to 10 or more. Therefore, the heavy water separation device 1 can obtain heavy water enriched water 33 having a higher heavy water content after electrolysis than in the electrolyte 25 before electrolysis. The heavy water concentration further increases if the electrolyte 25 is circulated for a long period of time. By returning the heavy water enriched water 33 to the electrolyte 25 and circulating it through the heavy water separation device 1, the heavy water concentration in the heavy water enriched water 33 can be ultimately increased.

[0042] The amount of current supplied from the power supply 20 is not limited, but is in the range of 0.03 to 1.0 A / cm 2 may be 0.1 to 0.5 A / cm 2 If the amount of current is too small, the electrolysis efficiency will decrease, and if the amount of current is too large, there is a possibility that heat will be generated and the burden on each part of the device will increase.

[0043] [Series type heavy water separator] Fig. 6 is a block diagram showing a series-type heavy water separation apparatus 1A formed by connecting in series the electrolyte paths of the heavy water separation apparatus 1 shown in Fig. 1. This series-type heavy water separation apparatus 1A includes a first-stage heavy water separation cell 2A and a second-stage heavy water separation cell 2B, but it is also possible to have more stages (three or more stages).

[0044] The heavy water concentrate 33A discharged from the gas-liquid separator 32 of the first-stage heavy water separation cell 2A is pressurized by a pump 51 and supplied to the bipolar plate 14 of the second-stage heavy water separation cell 2B through a conduit 52, where the heavy water concentration is further increased in the second-stage heavy water separation cell 2B. As a result, the heavy water concentrate 33B discharged from the oxygen outlet 28 of the second-stage heavy water separation cell 2B has a higher heavy water concentration than the heavy water concentrate 33A from the first stage. By increasing the number of stages in this way, the separation factor α of the cathode catalyst layer 8 has an exponential effect, making it possible to achieve even higher heavy water separation efficiency. The heavy water concentrate 33B can also be circulated by returning it to the electrolyte tank 26 of the first-stage heavy water separation cell 2A through a conduit 54. The other configurations are the same as those shown in FIG. 1.

[0045] [Parallel heavy water separator] Figure 7 is a partial cross-sectional view showing a parallel-type heavy water separation apparatus 1B formed by connecting in parallel the heavy water separation apparatuses 1 shown in Figure 1. This parallel-type heavy water separation apparatus 1B has three heavy water separation apparatuses 1 arranged in parallel, but the number of heavy water separation apparatuses 1 arranged in parallel may be two, four or more.

[0046] This parallel-type heavy water separation apparatus 1B is provided with a common electrolyte inlet 22A communicating with the electrolyte inlets 22 of the bipolar plates 14 of each cell, a common oxygen outlet 28A communicating with the oxygen outlets 28 of the bipolar plates 14 of each cell, and a common hydrogen outlet 40A communicating with the hydrogen outlets 40 of the bipolar plates 16 of each cell. A pair of pressure plates 56 are provided to sandwich the stacked heavy water separation apparatus 1 from both ends in the stacking direction, and multiple bolts 58 are provided to connect the pressure plates 56 to each other. The positive and negative poles of the power source 20 are connected to the bipolar plates 14 and 16 located at both ends of the stacked cells (stack), respectively. In this case, the voltage of the power source 20 is set so that the aforementioned amount of current flows through each cell.

[0047] According to this parallel-type heavy water separation apparatus 1B, the amount of electrolyzed water 25 that can be processed per unit time can be increased in accordance with the number of cells, thereby improving the efficiency of heavy water separation. Furthermore, in the present invention, it is possible to arrange multiple parallel-type heavy water separation apparatuses 1B in series along the electrolyte supply path.

[0048] Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and the configuration of each part can be changed within the scope of the claims. For example, non-essential components of each embodiment can be replaced with well-known components or can be deleted. [Example]

[0049] The effects of the present invention will be demonstrated below by giving examples of the present invention. [Preparation of catalyst ink] 10 mg of iron powder with an average particle size of 20 μm, 500 μL of pure water, 500 μL of 2-propanol, and 24 μL of a commercially available sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (Chemours Corporation, trade name "Nafion") dispersion (polymer concentration: 5% by mass) were mixed and subjected to ultrasonic stirring for 20 minutes to obtain a first catalyst ink.

[0050] [Catalyst for heavy water separation of Example 1] The first catalyst ink was applied to one side of each of two gas diffusion layers 12 using a brush. 5 cm × 5 cm carbon paper was used as the gas diffusion layer 12. One of the gas diffusion layers 12 with the catalyst ink applied was heated to 80°C for 0.3 hours in a drying oven to which air was continuously supplied, and dried. Under these heating conditions, oxidation of the iron powder in the catalyst ink proceeded moderately, and a cathode catalyst layer 8 with an iron compound containing γ-FeOOH adhered to the gas diffusion layer 12 was formed on the gas diffusion layer 12. This was the gas diffusion layer 12 and cathode catalyst layer 8 of Example 1. The first catalyst ink was also applied to a glass petri dish, dried under the same conditions, and the powder was collected, which was used as a sample of Example 1 for X-ray diffraction and SEM observation.

[0051] [Catalyst for heavy water separation of Comparative Example 1] The other gas diffusion layer 12 coated with the first catalyst ink was dried by heating at 80°C for 0.1 hours in a drying oven continuously supplied with nitrogen gas. Because oxidation of the iron powder did not proceed under these heating conditions, a cathode catalyst layer with pure iron powder adhered to it was formed on the gas diffusion layer 12. This was designated the gas diffusion layer 12 and cathode catalyst layer 8 of Comparative Example 1. The first catalyst ink was also applied to the inside of a glass petri dish, dried under the same conditions as in Comparative Example 1, and the powder was collected. This was used as a sample of Comparative Example 1 for X-ray diffraction and SEM observation.

[0052] [Catalyst for heavy water separation of Comparative Example 2] 10 mg of Ni powder with an average particle size of 20 μm, 500 μL of pure water, 500 μL of 2-propanol, and 24 μL of a commercially available sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (Chemours Corporation, trade name "Nafion") dispersion (polymer concentration: 5% by mass) were mixed and subjected to ultrasonic stirring for 20 minutes to obtain a second catalyst ink. The gas diffusion layer 12 coated with the second catalyst ink was dried by heating at 80°C for 0.1 hours in a drying oven to which nitrogen gas was continuously supplied. A cathode catalyst layer with pure Ni powder adhered thereto was formed on the gas diffusion layer 12. This was designated the gas diffusion layer 12 and cathode catalyst layer 8 of Comparative Example 2. The second catalyst ink was also applied to the inside of a glass petri dish, dried under the same conditions as in Comparative Example 2, and the powder was collected. This was used as a sample of Comparative Example 2 for X-ray diffraction and SEM observation.

[0053] [Catalyst for heavy water separation of Comparative Example 3] 3 mg of Pt powder with an average particle size of 5 nm and 7 mg of carbon powder with an average particle size of 50 nm were mixed with 500 μL of pure water, 500 μL of 2-propanol, and 24 μL of a commercially available sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (Chemours Corporation, trade name "Nafion") dispersion (polymer concentration: 5% by mass), and the mixture was subjected to ultrasonic stirring for 20 minutes to obtain a third catalyst ink. The gas diffusion layer 12 coated with the third catalyst ink was dried by heating at 80°C for 0.1 hours in a drying oven to which nitrogen gas was continuously supplied. A cathode catalyst layer with Pt / C powder adhered thereto was formed on the gas diffusion layer 12. This was designated the gas diffusion layer 12 and cathode catalyst layer 8 of Comparative Example 2. Furthermore, the third catalyst ink was applied to the inside of a glass petri dish, dried under the same conditions as in Comparative Example 3, and the powder was collected. This was used as a sample of Comparative Example 3 for X-ray diffraction and SEM observation.

[0054] [Determining the maximum current] The device shown in Figure 1 was actually fabricated, incorporating the cathode catalyst layer 8 and gas diffusion layer 12 of Example 1. The electrolyte 25 was 500 mL of a KOH solution prepared by adding 10 mM KOH to 10 at% D heavy water mixture water to adjust the pH to 12.0. The liquid delivery rate by the pump 24 was 2.1 mL / min. An IrO2 catalyst was used as the anode catalyst layer 6.

[0055] The voltage supplied from the power supply 20 is adjusted to keep the current density between 0 and 0.4 A / cm. 2 Then, the current is gradually changed to 0 A / cm 2 The relationship between time and current density was plotted, and the results are shown in Figure 8. As shown in Figure 8, 2 Since the anion exchange membrane 4 deteriorated when the current density reached 0.4 A / cm, the upper limit of the current density in the following experiments was 0.4 A / cm. 2 It was decided.

[0056] [Measurement of cell voltage versus current density] In the device of FIG. 1, electrolysis experiments were carried out using the cathode catalyst layers 8 of Example 1, Comparative Example 2 (Ni), and Comparative Example 3 (Pt / C). When each catalyst was used, the current density was 0.05 to 0.4 A / cm. 2 The change in cell voltage with respect to the temperature was investigated, and the results are shown in Figure 9. 9, in Comparative Example 2 (Ni), the current density at the same cell voltage was smaller than in Example 1 and Comparative Example 3 (Pt / C), and it was found that it was difficult to increase the current density. With the cathode catalyst layer 8 of Example 1, the cell voltage was higher than in Comparative Example 3 while the current density was low, but the current density was 0.4 A / cm 2 It was found that when the temperature approached 100°C, the temperature was comparable to that of Comparative Example 3.

[0057] [Measurement of separation factor of heavy water] In the device of FIG. 1, electrolysis experiments were carried out using the cathode catalyst layers 8 of Example 1, Comparative Example 2 (Ni), and Comparative Example 3 (Pt / C), and a current density of 0.24 A / cm was obtained using each catalyst. 2 The separation factor α for heavy water was measured when the following conditions were met: The results are shown in Figure 10. 10, the separation factor in Example 1 was approximately 11. On the other hand, the separation factor in Comparative Example 2 (Ni) was approximately 7, and the separation factor in Comparative Example 3 (Pt / C) was approximately 5.8. The high separation factor α in the present invention was demonstrated.

[0058] [Breakdown of hydrogen gas components based on ion current ratio] In the device of FIG. 1, electrolysis experiments were carried out using the cathode catalyst layers 8 of Example 1, Comparative Example 2 (Ni), and Comparative Example 3 (Pt / C), and a current density of 0.24 A / cm was obtained using each catalyst. 2 The hydrogen gas discharged from the conduit 48 under this condition was analyzed by a quadrupole mass spectrometer 50 to measure the breakdown of the hydrogen gas. The results are shown in FIG. 11, in Example 1, 99.0% of the hydrogen gas discharged from conduit 48 was H2, the remaining 1.0% was HD, and almost no D2 was generated. In contrast, in Comparative Example 2 (Ni), 98.4% of the hydrogen gas discharged from conduit 48 was H2, the remaining 1.6% was HD, and a trace amount of D2 was also generated. In Comparative Example 3 (Pt / C), 97.8% of the hydrogen gas discharged from conduit 48 was H2, the remaining 2.1% was HD, and about 0.1% of D2 was also generated. Therefore, it was proven that the cathode catalyst layer 8 of Example 1 can provide high separation performance for heavy water, which is almost consistent with the separation factor α shown in FIG.

[0059] [Comparison of Compositions Between Example 1 and Comparative Example 1 by Auger Electron Spectroscopy (AES)] For the cathode catalyst layer 8 of Example 1 and the cathode catalyst layer 8 of Comparative Example 1, the Fe, Fe on the extreme surface of the catalyst particles was measured by Auger electron spectroscopy (AES) while etching the surface of the catalyst particles with an argon ion beam. 2+ ,Fe 3+ and the amount of Fe, Fe within 85.6 nm from the surface of the catalyst particle. 2+ ,Fe 3+ The amounts of Fe and Fe present were compared. The results are shown in Figure 12. Figure 12(a) shows a schematic diagram of the measurement points on the extreme surface of the catalyst particle. Figure 12(b) shows a schematic diagram of the measurement points inside the catalyst particle. Figures 12(c) and 12(d) show the amounts of Fe and Fe present at the positions (a) and (b), respectively, using a cathode catalyst layer 8 made of Comparative Example 1 (pure Fe). 2+ ,Fe 3+ 12(e) and 12(f) are graphs showing the results of measuring the amounts of Fe, Fe at positions (a) and (b), respectively, using the cathode catalyst layer 8 of Example 1. 2+ ,Fe 3+ 1 is a graph showing the results of measuring the abundance of

[0060] In the cathode catalyst layer 8 of Comparative Example 1, as shown in FIGS. 12(c) and 12(d), Fe was 1.5% on the surface of the catalyst particles, and Fe 2+ 12.0%, Fe 3+ The Fe content was 5.9%, while the Fe content was 60% in the interior of the catalyst particle (at a position 85.6 nm from the surface). 2+ 2%, Fe 3+ It was found that only the very surface was oxidized.

[0061] In contrast, in the cathode catalyst layer 8 of Example 1, as shown in FIGS. 12(e) and 12(f), Fe was 1.0% on the surface of the catalyst particles, and Fe 2+11.0%, Fe 3+ The Fe content was 10.0%, while the Fe content was 6% in the interior of the catalyst particle (at a position 85.6 nm from the surface). 2+ 17%, Fe 3+ The oxidation rate was approximately 13%, which indicated that the catalyst particles were oxidized to their interiors.

[0062] [Composition Test by X-ray Diffraction (XRD) of Example 1] In Example 1, the catalyst powder for heavy water separation obtained in the glass petri dish of Example 1 was subjected to an X-ray diffractometer (XRD) to measure the X-ray counts relative to 2θ (Coupled Two Theta / Theta). The results are shown in Figure 13. As a comparative sample, FeO raw (Ka2 removed) smoothing PDF 70-0714, FeOOH, Iron Hydroxide, CmC21(36) PDF 81-0463, FeO(OH), Goethite, Syn,Pbnm(62) was used. The measurement conditions were as follows: ·X-ray:Cu / 30kV / 10mA 2θ range: 10~80° Detector: High-speed semiconductor detector Filter: 2.5 Divergence slit: 1° Scanning speed: 20° / min Scattering slit 2.5° Step width: 0.05° Receiving slit: 2.5°

[0063] 13, it was shown that γ-FeOOH and α-FeOOH were present as a mixture in the heavy water separation catalyst of Example 1. The mass ratio of γ-FeOOH:α-FeOOH was approximately 1:1.

[0064] [Scanning Electron Microscope (SEM) Photo Measurements Before and After Electrolysis Experiment in Example 1] Using the cathode catalyst layer 8 of Example 1, scanning electron microscope photographs were taken at 10,000x magnification of the catalyst particles before and after the electrolysis experiment. The results are shown in Figure 15 (before the electrolysis experiment) and Figure 16 (after the electrolysis experiment). A comparison of Figure 15 and Figure 16 revealed that the heavy water separation catalyst of Example 1 had many fine protrusions on its surface after the electrolysis experiment, indicating a change in surface properties.

[0065] [Scanning electron microscope (SEM) photographs of Comparative Example 2 (Ni) before and after electrolysis experiment] Scanning electron microscope photographs of the catalyst particles of the cathode catalyst layer 8 of Comparative Example 2 (Ni) were taken at 10,000x magnification before and after the electrolysis experiment. The results are shown in Figure 17 (before the electrolysis experiment) and Figure 18 (after the electrolysis experiment). A comparison of Figures 17 and 18 revealed that the surface properties of the heavy water separation catalyst of Comparative Example 2 (Ni) hardly changed before and after the electrolysis experiment.

[0066] [Scanning electron microscope (SEM) photographs of Comparative Example 3 (Pt / C) before and after electrolysis experiment] Using the cathode catalyst layer 8 of Comparative Example 3 (Pt / C), scanning electron microscope photographs of the catalyst particles were taken at 10,000x magnification before and after the electrolysis experiment. The results are shown in Figure 19 (before the electrolysis experiment). The surface properties of the heavy water separation catalyst of Comparative Example 3 (Pt / C) hardly changed before and after the electrolysis experiment. Therefore, only Figure 19 (before the electrolysis experiment) is shown.

[0067] [Comparative electrolysis experiments using pure γ-FeOOH, Fe, α-FeOOH, and Fe2O3] A similar apparatus to that shown in Figure 1 was assembled using γ-FeOOH powder (Example 2), a pure iron plate (Comparative Example 4), α-FeOOH powder (Comparative Example 5), and Fe2O3 powder (Comparative Example 6), all purchased as high-purity reagents (purity of 99% by mass or higher). A heavy water concentration electrolysis experiment was conducted to measure the separation factor α. The γ-FeOOH powder (Example 2), α-FeOOH powder (Comparative Example 5), and Fe2O3 powder (Comparative Example 6) used in the experiment had an average particle size of 20 μm. Ten milligrams of each powder was mixed with 500 μL of pure water, 500 μL of 2-propanol, and 24 μL of a commercially available sulfonated tetrafluoroethylene-based fluoropolymer copolymer (Chemours, trade name "Nafion") dispersion (polymer concentration: 5% by mass). The mixture was ultrasonically stirred for 20 minutes to prepare catalyst inks. These catalyst inks were applied with a brush to one side of each gas diffusion layer 12, the same as in Example 1, and dried at 80°C in a drying oven in a nitrogen gas atmosphere. Under these heating conditions, the catalyst components in the catalyst inks were not changed. Furthermore, for the pure iron plate (Comparative Example 4), a number of holes were drilled in the pure iron plate to form the cathode catalyst layer 8, and an apparatus similar to that in Example 2 was assembled.

[0068] Next, a current density of 0.24 A / cm was generated using devices incorporating the catalysts γ-FeOOH powder (Example 2), pure iron plate (Comparative Example 4), α-FeOOH powder (Comparative Example 5), and Fe2O3 powder (Comparative Example 6). 2 The separation factor α for heavy water was measured when the following conditions were met: The results are shown in Figure 20. As shown in Figure 20, in Example 2 using γ-FeOOH powder, the separation factor α was approximately 9.5. On the other hand, the separation factor α was approximately 6.2 for the pure iron plate (Comparative Example 4), approximately 5.8 for the α-FeOOH powder (Comparative Example 5), and approximately 5.4 for the Fe2O3 powder (Comparative Example 6). This experiment revealed that γ-FeOOH had the highest separation factor α.

[0069] [Changes in γ-FeOOH powder (Example 2) before and after electrolysis experiment] The γ-FeOOH powder (Example 2) before the electrolysis experiment was subjected to an X-ray diffractometer (XRD) to measure the X-ray count versus 2θ (Coupled Two Theta / Theta). The results are shown in Figure 21. Furthermore, the catalyst powder (Example 2) after the electrolysis experiment was collected from the electrolysis apparatus and similarly subjected to an X-ray diffractometer (XRD) to measure the X-ray count versus 2θ (Coupled Two Theta / Theta). The results are shown in Figure 22. Furthermore, the α-FeOOH powder (Comparative Example 5) before the electrolysis experiment was subjected to an X-ray diffractometer (XRD) to measure the X-ray count versus 2θ (Coupled Two Theta / Theta). The results are shown in Figure 23.

[0070] 21 to 23, it was found that the γ-FeOOH powder (Example 2) before the electrolysis experiment was partially converted to α-FeOOH after the electrolysis experiment. It was found that in order to perform electrolysis while suppressing the conversion to α-FeOOH, it is effective to maintain the environment to which the cathode catalyst layer 8 is exposed as highly reducing as possible.

[0071] An electron microscope photograph at 1000x magnification taken using a scanning electron microscope of the γ-FeOOH powder (Example 2) in a reagent state before the electrolysis experiment is shown in Figure 24. An electron microscope photograph taken under the same conditions of the γ-FeOOH powder (Example 2) in a state supported on the gas diffusion layer 12 before the electrolysis experiment is shown in Figure 25. Furthermore, an electron microscope photograph taken under the same conditions of the same catalyst in a state supported on the gas diffusion layer 12 after the electrolysis experiment is shown in Figure 26.

[0072] A comparison of Figures 24 to 26 revealed that the γ-FeOOH powder (Example 2) before the electrolysis experiment shown in Figures 24 and 25 was a particle with a smooth surface, whereas the same catalyst particle photographed after the electrolysis experiment was in a porous state with many small holes formed therein. From the results of Figures 21 to 26, it was predicted that the catalyst for heavy water separation in the example would be desirably replaced with a new catalyst containing γ-FeOOH after a certain period of operation, in anticipation of the change to α-FeOOH and the formation of porosity. [Industrial Applicability]

[0073] The catalyst for heavy water separation, its manufacturing method, heavy water separation cell, and heavy water separation apparatus according to the present invention can increase the separation factor α, which indicates that the decomposition of HO occurs preferentially over the decomposition of HOD and HOT due to the isotope effect, and can therefore increase the separation efficiency of heavy water. Therefore, the present invention is industrially applicable. [Explanation of symbols]

[0074] 1 Heavy water separation equipment 2 Heavy water separation cell 4 anion exchange membrane 6 anode catalyst layer 8 cathode catalyst layer 10 gas diffusion layer 12 gas diffusion layer 14 bipolar plate 16 Bipolar plate 17 Flow path 18 Channel 1A Series heavy water separator 1B Parallel heavy water separator 20 Power supply 22 electrolyte inlet 24 pump 25 Electrolyte 26 Electrolyte tank 28 oxygen outlet 30 conduit 32 Gas-liquid separator 33 Heavy water concentrate 34 Conduit 36 ​​Outlet 38 Water supply pipe 40 Hydrogen outlet 42 Conduit 44 Gas-liquid separator 46 Water 48 Conduit 50 Quadrupole mass spectrometer 52 Conduit 54 Conduit 56 Pressure Plate 58 volts

Claims

1. A catalyst for heavy water separation, comprising γ-FeOOH.

2. 2. The catalyst for heavy water separation according to claim 1, wherein the catalyst for heavy water separation is a powder having an average particle size of 0.05 to 500 μm.

3. 3. The catalyst for heavy water separation according to claim 1, wherein the solid polyelectrolyte polymer is contained in an amount of 0.1 to 50% by mass of the entire catalyst for heavy water separation.

4. mixing iron powder, water, and a solid polymer electrolyte polymer to obtain a mixture; A method for producing a catalyst for heavy water separation comprising applying the mixture to the surface of a carrier, and then heating the mixture for 0.1 to 1 hour in an oxygen-containing atmosphere at 60 to 150°C to oxidize the iron powder, thereby producing a catalyst for heavy water separation containing γ-FeOOH.

5. an anion exchange membrane; an anode catalyst layer and a cathode catalyst layer provided on either side of the anion exchange membrane; and an anode-side gas diffusion layer and a cathode-side gas diffusion layer disposed further outside the anode catalyst layer and the cathode catalyst layer, respectively; 3. A heavy water separation cell, wherein the cathode catalyst layer contains the heavy water separation catalyst according to claim 1.

6. The heavy water separation cell according to claim 5; an anode disposed on the outside of the anode-side gas diffusion layer; an anode-side flow path provided in the anode, for circulating and supplying an electrolyte solution to the anion exchange membrane through the anode-side gas diffusion layer and the anode catalyst layer, and for discharging oxygen gas generated by electrolysis of water in the electrolyte solution; a cathode disposed on the outer side of the cathode-side gas diffusion layer; a cathode-side flow path provided at the cathode for discharging water that has permeated the anion exchange membrane and hydrogen gas generated by electrolysis of the water;

7. 7. A series-type heavy water separation apparatus comprising a plurality of heavy water separation apparatuses according to claim 6, the anode-side flow paths of the heavy water separation apparatuses being connected in series.

8. 7. A parallel-type heavy water separation apparatus comprising a plurality of heavy water separation apparatuses according to claim 6, the anode-side flow passages and the cathode-side flow passages of the heavy water separation apparatuses being connected in parallel.

Images