JP7361333B2 - How to decompose organic matter - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Law (1) On February 20, 2019, at the graduation thesis presentation of the School of Environmental and Urban Engineering, Kansai University (2) On March 1, 2019, in the proceedings of the 99th Spring Annual Meeting of the Chemical Society of Japan, a public interest incorporated association entitled "Effective decomposition of organic pollutants and detoxification" was presented. Presented under the title "Development of iron-based layered double hydroxide that enables detoxification" (3) At the lecture of the 99th Spring Annual Meeting of the Chemical Society of Japan on March 19, 2019. Presentation titled "Development of iron-based layered double hydroxide that enables effective decomposition and detoxification of organic pollutants"

The present invention relates to a method for decomposing organic matter.

The Fenton reaction is a reaction in which hydroxyl radicals are generated from hydrogen peroxide using divalent iron as a catalyst. Iron ions (Fe ²⁺ and Fe ³⁺ ) are widely known as catalysts for Fenton reactions, ie, Fenton reaction catalysts. By using this, hydroxyl radicals (.OH) can be generated as represented by the following reaction formulas (1) and (2).
Fe ²⁺ + H ₂ O ₂ → Fe ³⁺ + ・OH + OH ⁻ (1)
Fe ³⁺ + H ₂ O ₂ → Fe ²⁺ + ・O ₂ ^- + 2H ⁺ (2)

Hydroxy radicals have a strong oxidizing power, and by utilizing this strong oxidizing power, it is possible to perform, for example, sterilization, decomposition of organic substances (toxic substances, hard-to-decompose pollutants, etc.), and the like. Therefore, the Fenton reaction is expected to be applied to various fields as a clean method with low environmental impact.

Conventionally, the Fenton reaction is generally a homogeneous Fenton reaction that uses a water-soluble iron (II) salt (for example, iron (II) sulfate) that produces iron (II) ions in water. On the other hand, there are few reports of heterogeneous Fenton reactions using solid iron catalysts in water. As a technique using a heterogeneous Fenton reaction, for example, Patent Document 1 describes a method of non-biodegradation by a heterogeneous Fenton reaction using a catalytic metal supported carrier in which a catalytic metal such as iron is supported on an inorganic carrier such as zeolite. A method for treating water containing organic matter is described.

Japanese Patent Application Publication No. 2014-198286

For example, when treating wastewater containing oxidizable organic matter as a hazardous substance or pollutant, when the homogeneous Fenton reaction is used to oxidize and decompose the organic matter in the wastewater, iron (II) ions used as a catalyst are Since the resulting water-soluble iron(II) salt is transient, it is usually necessary to continuously add the iron(II) salt. Therefore, in this case, iron (II) ions remain in the wastewater, and in order to insolubilize and remove them, sludge containing insolubilized iron compounds derived from the iron catalyst is inevitably produced, and This will occur in relatively large amounts.

On the other hand, when using the heterogeneous Fenton reaction, unlike the transient decomposition technology that uses a water-soluble iron(II) salt as the iron catalyst in the homogeneous Fenton reaction, a solid iron catalyst is used. Since it can be used repeatedly, the amount of sludge that contains compounds derived from iron catalysts can be reduced. Furthermore, in this case, the amount of chemicals (for example, flocculants, etc.) used for insolubilization to remove the iron catalyst as sludge can also be suppressed. Therefore, the heterogeneous Fenton reaction is considered to be more desirable than the homogeneous Fenton reaction in that it is easier to reuse the catalyst. However, because the heterogeneous Fenton reaction uses a solid catalyst, it is less efficient than the homogeneous Fenton reaction, which uses a water-soluble iron salt that produces iron ions in water.

Therefore, when decomposing organic substances using the heterogeneous Fenton reaction, it would be a useful method if the catalytic performance of the heterogeneous Fenton reaction catalyst used for the reaction could be improved.

Therefore, the present invention aims to provide a method for decomposing organic substances that can efficiently decompose organic substances by improving the catalytic performance of the heterogeneous Fenton reaction catalyst. .

As a result of intensive research aimed at providing a method for decomposing organic matter as described above, the present inventors have discovered layered double hydroxides containing divalent iron ions, trivalent metal ions, and anions, and their layered double hydroxides. We have found that the amorphous composite hydroxide obtained after the structure of the material collapses is useful as a catalyst for the heterogeneous Fenton reaction. The inventors have discovered that catalytic performance can be improved by bringing the heterogeneous Fenton reaction catalyst into contact with hydrogen peroxide under conditions of irradiation with light in the range from ultraviolet to infrared rays, leading to the present invention.

The present invention provides a heterogeneous Fenton reaction catalyst containing a layered double hydroxide and/or an amorphous composite hydroxide containing divalent iron ions, trivalent metal ions, and anions, and hydrogen peroxide. Provided is a method for decomposing an organic substance, the method comprising: generating radicals by contacting them under irradiation conditions with light in the range from ultraviolet to infrared; and contacting the radicals with an organic substance to be decomposed. .

According to the present invention, it is possible to provide a method for decomposing organic substances that can efficiently decompose organic substances by improving the catalyst performance when decomposing organic substances using a heterogeneous Fenton reaction catalyst.

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. In this specification, the expressions "contain" and "comprising" include the concepts of "containing", "comprising", "consisting essentially" and "consisting only". Moreover, in this specification, "and/or" is a term that includes both "and" and "or." That is, A and/or B includes three meanings among A and B: only A, only B, and both A and B.

<Method for decomposing organic matter>
A method for decomposing organic matter according to an embodiment of the present invention (hereinafter sometimes simply referred to as "method for decomposing organic matter") is a layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions. A heterogeneous Fenton reaction catalyst containing a compound and/or an amorphous composite hydroxide is brought into contact with hydrogen peroxide under irradiation conditions of light in the range from ultraviolet to infrared to generate radicals. and bringing the radical into contact with the organic matter to be decomposed.

Since the above-mentioned specific heterogeneous Fenton reaction catalyst contains a specific layered double hydroxide and/or amorphous composite hydroxide, by bringing the heterogeneous Fenton reaction catalyst into contact with hydrogen peroxide, , can generate radicals. Although this radical is not particularly limited, it is believed that it is primarily a hydroxyl radical. In the organic matter decomposition method of the present embodiment, the specific heterogeneous Fenton reaction catalyst and hydrogen peroxide are brought into contact with each other under irradiation conditions of light in the range from ultraviolet to infrared rays. It is possible to further improve the catalytic performance of the Fenton-based Fenton reaction catalyst. This further increases the ability to generate radicals through contact with hydrogen peroxide, and by bringing the radicals into contact with the organic matter, it becomes possible to efficiently decompose the organic matter.

When bringing the heterogeneous Fenton reaction catalyst into contact with hydrogen peroxide, the irradiation conditions for light in the range from ultraviolet rays to infrared rays are particularly important if it is possible to improve the catalytic performance of the heterogeneous Fenton reaction catalyst. Not restricted. For this light irradiation, a light irradiation device that is capable of irradiating light in a range from ultraviolet to infrared rays and that includes a light irradiation section and a control panel can be used. Since light in the range from ultraviolet rays to infrared rays is used, light with a wavelength of more than 1 nm and less than 1 mm can be used. From the viewpoint of the activity of the heterogeneous Fenton reaction catalyst, the light is preferably at least one of ultraviolet light and visible light, such as sunlight. Furthermore, the wavelength of the light is preferably 200 to 3000 nm, more preferably 200 to 900 nm, even more preferably 300 to 700 nm.

The mode of contact between the heterogeneous Fenton reaction catalyst and hydrogen peroxide is not particularly limited as long as radicals are generated by the contact. The heterogeneous Fenton reaction catalyst and hydrogen peroxide can be brought into contact, for example, by mixing the heterogeneous Fenton reaction catalyst and hydrogen peroxide. Further, the contact between the heterogeneous Fenton reaction catalyst and hydrogen peroxide can usually be carried out in the presence of water, for example, in water containing the heterogeneous Fenton reaction catalyst and hydrogen peroxide. . The concentration of the heterogeneous Fenton reaction catalyst in the water is not particularly limited, and the concentration as the layered double hydroxide is preferably 0.001 to 10% by mass, and 0.01 to 2% by mass. %, and even more preferably 0.05 to 0.5% by mass. Further, when the catalyst is molded and filled into the reaction apparatus, the concentration of the heterogeneous Fenton reaction catalyst in water is preferably 1 to 50% by mass as the layered double hydroxide, for example, More preferably, it is 2 to 20% by mass. The concentration of hydrogen peroxide in water before the reaction is not particularly limited, and for example, it is preferably 0.1 to 500 mmol/L, more preferably 1 to 200 mmol/L, and 1 to 100 mmol/L. It is more preferable that it be present, and even more preferably that it be 2 to 20 mmol/L.

The mode of contact between the radical and the organic substance to be decomposed is not particularly limited. The contact between the radical and the organic substance can be performed, for example, by mixing the heterogeneous Fenton reaction catalyst, hydrogen peroxide, and the organic substance. Further, the contact between the radical and the organic substance can usually be carried out in the presence of water, for example, in water containing a heterogeneous Fenton reaction catalyst, hydrogen peroxide, and the organic substance. In this case, in the water, radicals (hydroxy radicals) are generated from hydrogen peroxide by the action of the heterogeneous Fenton reaction catalyst, and the radicals can be brought into contact with the organic substance. The concentration of the heterogeneous Fenton reaction catalyst in water and the concentration of hydrogen peroxide before the reaction are the same as above. The concentration of organic matter in water is not particularly limited, and for example, it is preferably 0.001 to 1000 mmol/L, more preferably 0.01 to 100 mmol/L, and 0.1 to 10 mmol/L. It is even more preferable.

The temperature at which the heterogeneous Fenton reaction catalyst and hydrogen peroxide are brought into contact is not particularly limited as long as the temperature allows the Fenton reaction to proceed. The temperature thereof is, for example, preferably 0 to 100°C, more preferably 10 to 50°C, even more preferably 15 to 40°C. Further, the contact time is not particularly limited as long as it is long enough to generate a certain amount of radicals, and is, for example, 1 minute to 3 hours, preferably 15 minutes to 2 hours.

The method for decomposing organic matter can be suitably employed as one aspect thereof in a method (water treatment method) for treating water (water to be treated) containing an organic matter to be decomposed. This water treatment method preferably includes contacting the water to be treated containing organic matter, a heterogeneous Fenton reaction catalyst, and hydrogen peroxide. As a result, by bringing the heterogeneous Fenton reaction catalyst into contact with hydrogen peroxide in the water to be treated, radicals can be generated from hydrogen peroxide by the action of the heterogeneous Fenton reaction catalyst, and the radicals and the It can be brought into contact with treated water. Moreover, thereby, the generated radicals can be brought into contact with the organic matter in the water to be treated, and the organic matter can be oxidized and decomposed by the radicals. In this specification, the term "water to be treated" refers to water to be treated, that is, water to be treated, and is not particularly limited as long as it contains organic matter. Examples include wastewater containing organic matter. It will be done.

The mode of contact between the water to be treated, the heterogeneous Fenton reaction catalyst, and hydrogen peroxide (the contact between the water to be treated and radicals) is not particularly limited. For example, by mixing the water to be treated, the heterogeneous Fenton reaction catalyst, and hydrogen peroxide, they can be brought into contact, and the contact can be performed in a predetermined tank (reaction tank). Preferably, hydrogen peroxide and a heterogeneous Fenton reaction catalyst can be brought into contact with the water to be treated containing organic matter by adding the hydrogen peroxide and the heterogeneous Fenton reaction catalyst. In addition, as another more preferable embodiment, the heterogeneous Fenton reaction catalyst is supported on a carrier and kept in a fixed state in a reaction tank, and in the reaction tank, the heterogeneous The Fenton reaction catalyst and hydrogen peroxide can be contacted. For example, the water to be treated can be configured to be transferred to a reaction tank in which a carrier carrying a heterogeneous Fenton reaction catalyst (catalyst carrier) is installed. Hydrogen peroxide can be added to the water to be treated.

In addition, in the above-mentioned water treatment method, a pH adjustment tank may be installed in either or both of the front stage and the rear stage of the reaction tank to adjust the pH of the water to be treated or the water in the treatment process. Further, a solid-liquid separator may be installed at the rear of the reaction tank (if a pH adjustment tank is further provided at the rear stage, the pH adjustment tank). For example, when suspended solids containing layered double hydroxide are generated in water in a heterogeneous Fenton reaction catalyst used for oxidative decomposition of organic matter, treatment using a solid-liquid separator (solid-liquid separation treatment) , suspended solids can be removed. On the other hand, as described above, if the heterogeneous Fenton reaction catalyst is supported on a carrier and retained in the reaction tank in a fixed state, the solid-liquid separation treatment described above can be made unnecessary.

When the method for decomposing organic matter includes contacting a heterogeneous Fenton reaction catalyst with hydrogen peroxide in water, such as in the water treatment method described above, the above-mentioned light irradiation may be carried out, for example, in water (for example, when the above-mentioned reaction The reaction may be carried out by an internal illumination method using a light irradiation section provided outside the reaction tank (for example, outside the reaction tank) or by an external illumination method using a light irradiation section provided outside (for example, outside the reaction tank). In addition, in both internally illuminated and externally illuminated systems, if the light irradiation section can irradiate light onto water, which is the place where the heterogeneous Fenton reaction catalyst and hydrogen peroxide come into contact, the light irradiation section can It may be provided on any of the upper side, the bottom side, and the side side, and light may be irradiated from any of them.

A specific heterogeneous Fenton reaction catalyst used in a method for decomposing organic matter is a heterogeneous catalyst that is used in a solid phase, unlike a homogeneous catalyst that is used after being dissolved in a solution. Therefore, the organic matter decomposition method of this embodiment is a homogeneous system that requires continuous addition of a water-soluble iron (II) salt that produces iron (II) ions in water as a catalyst in order to decompose organic matter. Unlike transient techniques using Fenton reaction catalysts, it is possible to use the catalyst repeatedly (certain heterogeneous Fenton reaction catalysts). In addition, this also makes it possible to suppress the generation of sludge containing compounds derived from the catalyst, and to suppress the use of insolubilizing agents (such as flocculants) to remove the catalyst as sludge. . Therefore, it is expected that a useful water treatment method with reduced sludge disposal costs and catalyst costs will be realized. From the viewpoint of easily obtaining these effects, it is preferable that the heterogeneous Fenton reaction catalyst is used in a state where it is supported and fixed on the above-mentioned carrier.

The organic substance to be decomposed in the organic substance decomposition method is not particularly limited as long as it is an organic compound that can be decomposed by radicals. Examples of such organic substances include organic aliphatic substances, organic aromatic substances, and dioxin contaminants.

Organic aliphatic substances can be cyclic, acyclic, saturated or unsaturated hydrocarbons. These hydrocarbons include cyclic or acyclic alkanes and alkenes, preferably chlorinated, halogenated cyclic or acyclic alkanes and alkenes, saturated and/or unsaturated aliphatic and/or cycloaliphatic ethers, preferably chlorinated, saturated and/or unsaturated halogenated aliphatic and/or cycloaliphatic ethers, alcohols and preferably chlorinated halogenated alcohols, ketones and preferably chlorinated Halogenated ketones, aldehydes and preferably chlorinated halogenated aldehydes, and/or carboxylic acids and preferably chlorinated halogenated carboxylic acids. The organic aliphatic substance may also have a hydroxy group like an alcohol, a carboxy group like a fatty acid, or an oxyacid like a sulfonic acid. It may be an oxygen-containing compound including an ether group, such as dioxane, and may contain elements other than carbon, hydrogen, and oxygen (for example, nitrogen and sulfur).

The organic aliphatic substance is preferably trichloropropane, preferably 1,2,3-trichloropropane, chloropropenol, preferably 2-chloro-2-propen-1-ol, dichloropropene, preferably 1,3-dichloro Propene cis and 1,3-dichloropropene trans, dichloropropane, preferably 1,3-dichloropropane, dichloropropanol, preferably 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol , monochloropropanediol, more preferably 2-chloro-1,3-propanediol and 3-chloro-1,2-propanediol, 2-chloro-1-propanol, 1-chloro-2-propanol, chloroethanol, chloro Ethers, more preferably chloroethers, acrolein, methylglycidyl of the approximate formula C ₆ H ₁₀ Cl ₂ O ₂ , C ₆ H ₁₂ Cl ₂ O, C ₆ H ₉ Cl ₃ O ₂ , C ₆ H ₁₁ Cl ₃ O ₂ Ether, chloroacetone, methanol, glycerol, ethylene glycol, propylene glycol, butane-1,2-diol, hydroxyacetone, glyceraldehyde, formaldehyde, acetaldehyde, acrolein, formic acid, glycolic acid, acetic acid, propionic acid, lactic acid, succinic acid , oxalic acid, dichloroacetic acid, glycidol, epichlorohydrin, ethylene oxide, propylene oxide, butylene oxide and mixtures thereof.

Organic aromatic substances contain at least one ring of aromatic character. They are preferably halogenated aromatic hydrocarbons containing at least one ring of aromatic character and one halogen atom. The halogen may be selected from fluorine, chlorine, bromine, iodine, preferably chlorine. The aromatic ring may be mononuclear or polynuclear, preferably mononuclear. The organic aromatic substance is preferably selected from mono-, di-, tri-, tetra-, penta- and hexachlorobenzene and/or naphthalene, and mixtures thereof. The organic aromatic substance is preferably monochlorobenzene. Organic aromatic substances may also have hydroxy groups, such as phenol, carboxy groups, such as benzoic acid, or oxyacids, such as benzenesulfonic acid. Often, it may contain elements other than carbon, hydrogen, and oxygen (such as nitrogen and sulfur), and it may also contain a chain structure like alkylbenzenesulfonic acid.

Examples of dioxin contaminants include halogenated dibenzodioxins, halogenated dibenzofurans, and PCBs (particularly coplanar PCBs in which a chlorine atom is substituted at a position other than the ortho position).

Examples of halogenated dibenzodioxins include 2,3,7,8-tetrachlorodibenzo-P-dioxin, 1,2,3,7,8-pentachlorodibenzo-P-dioxin, 1,2,3, 4,7,8-hexachlorodibenzo-P-dioxin, 1,2,3,4,6,7,8-heptachlorodibenzo-P-dioxin, 1,2,3,4,6,7,8,9 -octachlorodibenzo-P-dioxin and the like.

Examples of halogenated dibenzofurans include 2,3,7,8-tetrachlorodibenzofuran, 1,2,3,7,8-pentachlorodibenzofuran, 1,2,3,4,7,8-hexachlorodibenzofuran, Examples include 1,2,3,4,6,7,8-heptachlorodibenzofuran and 1,2,3,4,6,7,8,9-octachlorodibenzofuran.

Examples of PCBs (especially coplanar PCBs with a chlorine atom substituted at a position other than the ortho position) include 3,3',4,4',5-tetrachlorobiphenyl, 3,3',4,4',5 -pentachlorobiphenyl, 3,3',4,4',5,5'-hexachlorobiphenyl and the like.

(Heterogeneous Fenton reaction catalyst)
The heterogeneous Fenton reaction catalyst used in the organic substance decomposition method of this embodiment is a layered double hydroxide and/or an amorphous composite containing divalent iron ions (Fe ²⁺ ), trivalent metal ions, and anions. Contains hydroxide. When this heterogeneous Fenton reaction catalyst is used in contact with hydrogen peroxide, radicals are generated from the hydrogen peroxide, and the radicals can decompose organic substances. From this, this heterogeneous Fenton reaction catalyst can function as a radical generation catalyst, a radical generation ability imparting agent, a radical generation ability improving agent, an organic substance decomposition catalyst, an organic substance decomposition ability imparting agent, an organic substance decomposition ability improving agent, etc. .

The arrangement of divalent iron ions, trivalent metal ions, and anions in the layered double hydroxide is not particularly limited, and any arrangement that constitutes the layered double hydroxide can be adopted. Layered double hydroxide has a structure in which a basic layer containing hydroxide and an intermediate layer containing anion and interlayer water are alternately laminated, and in one embodiment, typically, divalent iron ions and trivalent metal ions are placed in the base layer, and anions are placed in the intermediate layer. The crystal structure of the basic layer is not particularly limited, and can take a crystal structure depending on the types of divalent iron ions and trivalent metal ions, the synthesis method, etc. Layered double hydroxide is an amorphous composite hydroxide in which divalent iron ions, trivalent metal ions, and anions are arranged in close proximity even after the layered structure is destroyed by firing treatment, chemical reaction, etc. is formed. Therefore, the heterogeneous Fenton reaction catalyst may include at least one of a layered double hydroxide and an amorphous composite hydroxide. Since amorphous composite hydroxide is originally a layered double hydroxide, in this specification, "layered double hydroxide and/or amorphous composite hydroxide" is simply referred to as " Sometimes referred to as "layered double hydroxide."

In one embodiment, the layered double hydroxide can typically be represented by the following general formula (A). In the general formula (A), M ³⁺ represents a trivalent metal ion, A ^n- represents an n-valent anion, x represents a real number satisfying 0<x<1, and y represents a real number greater than 0.
General formula (A): [(Fe ²⁺ ) _1-x (M ³⁺ ) _x (OH) ₂ ][(A ^n- ) _x/n・yH ₂ O]

The trivalent metal ion (M ³⁺ ) is not particularly limited as long as it can constitute a layered double hydroxide together with divalent iron ions. Examples of trivalent metal ions include trivalent lanthanide ions such as trivalent aluminum ions, trivalent vanadium ions, trivalent cerium ions, trivalent lanthanum, trivalent iron ions, trivalent chromium ions, and trivalent cobalt. ion, trivalent indium ion, trivalent gallium ion, trivalent scandium ion, trivalent yttrium ion, trivalent manganese, trivalent arsenic, trivalent molybdenum, trivalent ruthenium, trivalent rhodium, trivalent antimony, trivalent gold, and trivalent bismuth. Among these, from the viewpoint of activity as a heterogeneous Fenton reaction catalyst, in one embodiment, trivalent metal ions other than iron ions are preferred, and trivalent aluminum ions, trivalent vanadium ions, trivalent metal ions, and trivalent metal ions are more preferred. Examples include valent lanthanoid ions (preferably trivalent cerium ions), more preferably trivalent aluminum ions, trivalent vanadium ions, etc., and particularly preferably trivalent aluminum ions. The trivalent metal ions may be used alone or in combination of two or more.

The molar ratio of divalent iron ions and trivalent metal ions in the layered double hydroxide (divalent iron ions:trivalent metal ions) is not particularly limited as long as it is a molar ratio that allows formation of the layered double hydroxide. . The molar ratio (divalent iron ion:trivalent metal ion) is preferably 2:1 to 4:1, more preferably 2:1 to 3:1. By increasing the number of moles of trivalent metal ions relative to divalent iron ions, more anions can be retained.

The anion is not particularly limited as long as it can constitute a layered double hydroxide. Examples of anions include sulfate ions, nitrate ions, halogen ions (fluoride ions, chloride ions, bromide ions, iodide ions, etc.), chlorate ions, bromate ions, iodate ions, perchlorate ions, and Examples include strong acid anions such as perbromate ions; weak acid anions such as carbonate ions, hydrogen carbonate ions, phosphate ions, hydrogen phosphate ions, and carboxylic acid ions (acetate ions, etc.). Among these, from the viewpoint of activity as a heterogeneous Fenton reaction catalyst, strong acid anions are preferred, with sulfate ions, nitrate ions, halogen ions, etc. being more preferred, and sulfate ions, nitrate ions, chloride ions, etc. is more preferred, and sulfate ion is even more preferred. The anion may be used alone or in combination of two or more.

The number of moles of anions in the layered double hydroxide can take an appropriate value depending on the number of moles of trivalent metal ions relative to divalent iron ions and the valence of the anions. Typically, when the number of moles of the trivalent metal ion is defined as X and the valence of the anion is defined as N, the number of moles of the anion is X/N.

Although I do not wish to give a restrictive interpretation, when a heterogeneous Fenton reaction catalyst is brought into contact with hydrogen peroxide, the peroxide species generated by the reaction between the anion and hydrogen peroxide are It greatly contributes to the Fenton reaction on valent iron ions, and together with the layered double hydroxide structure (the divalent iron ions and anions are thought to be arranged in close proximity), the efficiency of the Fenton reaction is further increased. it is conceivable that.

The heterogeneous Fenton reaction catalyst comprises the layered double hydroxide and/or amorphous composite hydroxide, and at least one inorganic oxide selected from the group consisting of silicon dioxide, titanium dioxide, and aluminum oxide. It is preferable to include a composite containing the following. Silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), and aluminum oxide (Al ₂ O ₃ ) are different from the above-mentioned layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions. , is a component that can further improve catalyst performance. By using a heterogeneous Fenton reaction catalyst containing a composite containing these specific inorganic oxides and layered double hydroxides in contact with hydrogen peroxide under the above-mentioned light irradiation conditions, organic matter can be further enhanced. It becomes possible to decompose efficiently. From this viewpoint, as the inorganic oxide, SiO ₂ and TiO ₂ are more preferable, and TiO ₂ is even more preferable.

The arrangement of the specific inorganic oxide in the composite may be such that the specific inorganic oxide is combined with a layered double hydroxide, and is represented by the general formula (A) above. It is preferable to adopt a structure in which the layered double hydroxide and the specific inorganic oxide are integrated. From this aspect, the layered double hydroxide can be referred to as a layered double hydroxide composited with a specific inorganic oxide (layered double hydroxide of an inorganic oxide composite system). It is more preferable that the specific inorganic oxide in the composite is disposed at a position in contact with the layered double hydroxide in such a manner that it is covered with the layered double hydroxide. As for the arrangement of the specific inorganic oxide and the layered double hydroxide in the composite, it is more preferable that the layered double hydroxide is attached around the specific inorganic oxide. Such a composite can be obtained, for example, by producing a layered double hydroxide in the presence of a specific inorganic oxide.

From the perspective of further improving catalyst performance and organic matter decomposition performance, the molar ratio of the above inorganic oxide to divalent iron ions in the layered double hydroxide and/or amorphous composite hydroxide is 0.01. -2 is preferable. The range of this molar ratio is more preferably 0.05 or more, even more preferably 0.1 or more, more preferably 1.5 or less, and even more preferably 1 or less.

The particle shapes of the layered double hydroxide, the specific inorganic oxide, and the composite containing them are not particularly limited. Examples of the particle shape include plate, spherical, rod, and polyhedral shapes.

The average particle size of the layered double hydroxide and the composite containing it and a specific inorganic oxide is not particularly limited. From the standpoint of Fenton reaction efficiency, smaller particles are desirable. The average particle diameter of the layered double hydroxide is preferably, for example, 10 nm to 5000 nm. For ease of handling, these particles may be granulated into, for example, plate-like, spherical, rod-like, polyhedral, etc. shapes, or may be applied to a solid surface. The average particle diameter of the granulated particles is preferably 1 mm to 50 mm, for example.

The heterogeneous Fenton reaction catalyst may consist only of layered double hydroxides, or may consist only of composites (layered double hydroxides and specific inorganic oxides); It may also contain other substances. Other substances include, for example, impurities that are inevitably mixed in when producing layered double hydroxide, other inorganic substances, and amorphous composite hydroxide obtained after the layered double hydroxide structure collapses. etc. The other substance may be integrated with the layered double hydroxide or may be separated from the layered double hydroxide.

The content of layered double hydroxide and/or amorphous composite hydroxide, or a composite containing them and a specific inorganic oxide, is based on the total mass (100% by mass) of the heterogeneous Fenton reaction catalyst. For example, the content can be 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. The upper limit of this content can be, for example, 99.9% by mass, 99% by mass, or 97% by mass.

(Method for producing heterogeneous Fenton reaction catalyst)
The method for producing the above-described heterogeneous Fenton reaction catalyst is not particularly limited. For example, preparing a mixture containing a salt of a divalent iron ion and an anion; a salt of a trivalent metal ion and an anion; and water; adjusting the pH of the mixture at 25°C to 3 to 14; It is possible to produce a heterogeneous Fenton reaction catalyst by a production method that involves obtaining a suspension.

By "preparing a mixture" in the method for producing a heterogeneous Fenton reaction catalyst, a reaction solution of the components contained in the mixture can be obtained. The divalent iron ion, trivalent metal ion, and anion used in "preparing the mixture" are as described above. Moreover, the mixture can also further contain the above-mentioned specific inorganic oxide.

The salt of divalent iron ions and anions used in the preparation of the mixture (divalent iron salt) varies depending on the type of anion employed in the layered double hydroxide, and examples thereof include FeCl ₂ , FeF ₂ , FeBr ₂ , _FeI2 , _FeSO4 , and Fe( _NO3 ) ₂ . One type of these divalent iron salts may be used alone, or two or more types may be used in combination. The concentration of the divalent iron salt in the mixture (reaction solution) is not particularly limited, but can be, for example, 0.2 to 2000 mmol/L, preferably 2 to 1000 mmol/L, more preferably 4 to 400 mmol/L. , more preferably 20 to 200 mmol/L.

The salt of trivalent metal ion and anion used for preparing the mixture (trivalent metal salt) varies depending on the type of anion employed in the layered double hydroxide, but for example, AlCl ₃ , AlF ₃ , AlBr ₃ , AlI ₃ , Al ₂ (SO ₄ ) ₃ , Al(NO ₃ ) ₃ , VCl ₃ , VF ₃ , VBr ₃ , VI ₃ , V ₂ (SO ₄ ) ₃ , V(NO ₃ ) ₃ , CeCl ₃ , CeF ₃ , CeBr ₃ , CeI ₃ , Ce ₂ (SO ₄ ) ₃ , Ce(NO ₃ ) ₃ , FeCl ₃ , FeF ₃ , FeBr ₃ , FeI ₃ , Fe ₂ (SO ₄ ) ₃ , Fe(NO ₃ ) _3, etc. can be mentioned. One type of these trivalent metal salts may be used alone, or two or more types may be used in combination. The concentration of the trivalent metal salt in the mixture (reaction solution) is not particularly limited, but can be, for example, 0.1 to 1000 mmol/L, preferably 1 to 500 mmol/L, more preferably 2 to 200 mmol/L. , more preferably 10 to 100 mmol/L.

The molar ratio of divalent iron to trivalent metal (divalent iron: trivalent metal) is not particularly limited as long as it is a molar ratio that allows synthesis of a layered double hydroxide. The molar ratio of divalent iron to trivalent metal (divalent iron:trivalent metal) is preferably 2:1 to 4:1, more preferably 2:1 to 3:1.

The liquid medium of the mixture (reaction liquid) is not particularly limited as long as it contains water. The mixture (reaction liquid) may contain a solvent other than water as a liquid medium. For example, the liquid medium is preferably a solvent for a salt of a divalent iron ion and an anion (a divalent iron salt) or a salt of a trivalent metal ion and an anion (a trivalent metal salt). When using an inorganic oxide dispersion medium, it is preferable to use an inorganic oxide dispersion medium. The content of water can be, for example, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, based on 100% by mass of the liquid medium of the reaction solution.

By "obtaining a suspension" in the method for producing a heterogeneous Fenton reaction catalyst, a layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions as solids from the suspension, and /Or an amorphous composite hydroxide can be obtained. In addition, by further containing the above-mentioned specific inorganic oxide in the mixture to obtain a suspension, the above-mentioned layered double hydroxide and/or amorphous composite water can be obtained as a solid content from the suspension. A composite containing an oxide and a specific inorganic oxide can be obtained. The suspension can be obtained by adjusting the pH of the above-mentioned mixture (reaction liquid) at 25° C. to 3 to 14. Note that the pH value of the above-mentioned mixture when obtaining this suspension is the value at 25°C, but the temperature of the mixture when obtaining the suspension is not particularly limited, and is, for example, room temperature (5 to 35°C). ℃), preferably in the range of 15 to 30℃.

When adjusting the pH of the mixture (reaction liquid), a known pH adjuster can be used. Examples of the pH adjuster include alkalis such as sodium hydroxide and calcium hydroxide, acids such as hydrochloric acid and sulfuric acid, and it is preferable to use alkalis and acids in the form of aqueous solutions. When obtaining a suspension, the pH of the mixture (reaction solution) at 25°C should be adjusted to 5 to 14 from the viewpoint of making it easier to obtain a suspension due to the formation of precipitates in the mixture (reaction solution). is more preferable, and it is even more preferable to adjust it to 7 to 14.

In this method for producing a heterogeneous Fenton reaction catalyst, after obtaining the above suspension, layered double hydroxide and/or amorphous composite hydroxide and specific inorganic When an oxide is used, the above composite can be obtained. On the other hand, from the viewpoint of increasing the crystallinity of the obtained layered double hydroxide, the suspension is preferably subjected to heat treatment, and more preferably hydrothermally treated. Accordingly, the temperature at which the suspension is applied is preferably 20 to 200°C, more preferably 60 to 140°C, and 100 to 140°C from the viewpoint of easy synthesis of the layered double hydroxide. It is even more preferable that there be. When heating the suspension by hydrothermal treatment etc., the heating time is preferably from 1 to 100 hours, and from 12 to 72 hours, from the viewpoint of easily obtaining a layered double hydroxide. is more preferable, and even more preferably 12 to 48 hours.

From the suspension obtained as described above, a solid layered double hydroxide or the above-mentioned composite can be obtained when a specific inorganic oxide is used. At this time, it is preferable to filter the suspension or wash it with water, and after that, it is more preferable to dry it under reduced pressure. The obtained substance (layered double hydroxide or a composite containing it and a specific inorganic oxide) can be used as a heterogeneous Fenton reaction catalyst as it is or mixed with other substances. .

Further, if necessary, it can be confirmed that a layered double hydroxide is contained in the heterogeneous Fenton reaction catalyst according to or in accordance with a known method. For example, it is possible to obtain a powder X-ray diffraction pattern and check whether a peak of layered double hydroxide is included.

As described above, one embodiment of the present invention can have the following configuration.
[1] A heterogeneous Fenton reaction catalyst containing a layered double hydroxide and/or an amorphous composite hydroxide containing divalent iron ions, trivalent metal ions, and anions, and hydrogen peroxide, A method for decomposing an organic substance, the method comprising: generating radicals by contacting the organic substance under irradiation conditions with light in the range from ultraviolet to infrared; and contacting the radical with an organic substance to be decomposed.
[2] The method for decomposing organic matter according to [1] above, wherein the light includes at least one of ultraviolet rays and visible rays.
[3] The heterogeneous Fenton reaction catalyst comprises the layered double hydroxide and/or the amorphous composite hydroxide, and at least one member selected from the group consisting of silicon dioxide, titanium dioxide, and aluminum oxide. The method for decomposing an organic substance according to [1] or [2] above, comprising a composite containing an inorganic oxide.
[4] The organic substance according to any one of [1] to [3] above, which includes contacting the radical with the organic substance by bringing the radical into contact with the water to be treated containing the organic substance. How to disassemble.
[5] Bringing the treated water containing organic matter, the heterogeneous Fenton reaction catalyst, and the hydrogen peroxide into contact under the light irradiation conditions to generate the radicals in the treated water. and bringing the radicals into contact with the organic matter in the water to be treated, according to any one of [1] to [4] above.

Hereinafter, one embodiment of the present invention will be described in more detail with reference to test examples, but the present invention is not limited to the following test examples.

<Production of layered double hydroxide>
(Manufacturing example 1)
A mixture containing iron(II) sulfate (FeSO ₄ ), aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), and pure water (molar ratio (Fe ²⁺ :Al ³⁺ )=1:0.5, FeSO ₄ concentration= 200 mmol/L, Al ₂ (SO ₄ ) ₃ concentration = 100 mmol/L). While stirring this liquid mixture at 1500 rpm, a 5 mol/L aqueous sodium hydroxide (NaOH) solution was added to the mixture to adjust the pH of the mixture to 10 at 25° C. to obtain a suspension. Next, the mixture (suspension) was hydrothermally treated at 120° C. for 24 hours, filtered and washed with pure water, and dried under reduced pressure. In this way, a layered double hydroxide (SO ₄ ^2- type Fe(II)-Al(III)-layered double hydroxide) containing divalent iron ions, trivalent aluminum ions, and sulfate ions was prepared. did. The obtained layered double hydroxide was observed by SEM and confirmed to have a particle size of 10 to 5000 nm. Powder X-ray diffraction (XRD) was also performed, and it was confirmed that a layered double hydroxide peak existed in the XRD pattern.

(Manufacturing example 2)
A mixture containing iron(II) chloride (FeCl ₂ ), aluminum chloride (AlCl ₃ ), and pure water (molar ratio (Fe ²⁺ :Al ³⁺ )=1:0.5, FeCl ₂ concentration=200 mmol/L, AlCl ₃ concentration = 100 mmol/L) was prepared. While stirring this liquid mixture at 1500 rpm, a 5 mol/L aqueous sodium hydroxide (NaOH) solution was added to the mixture to adjust the pH of the mixture to 10 at 25° C. to obtain a suspension. Next, the mixture (suspension) was hydrothermally treated at 120° C. for 24 hours, filtered and washed with pure water, and dried under reduced pressure. In this way, a layered double hydroxide (Cl ^-type Fe(II)-Al(III)-layered double hydroxide) containing divalent iron ions, trivalent aluminum ions, and chloride ions was prepared. . The obtained layered double hydroxide was observed by SEM and confirmed to have a particle size of 10 to 5000 nm. Powder X-ray diffraction (XRD) was also performed, and it was confirmed that a layered double hydroxide peak existed in the XRD pattern.

(Manufacturing example 3)
The preparation of the mixture in Production Example 2 was performed using a mixture (mol) containing FeCl ₂ , AlCl ₃ , and pure water as well as titanium dioxide (TiO ₂ ) powder (manufactured by Ishihara Sangyo Co., Ltd., trade name "ST-01"). The ratio (Fe ²⁺ :Al ³⁺ :TiO ₂ )=1:0.5:1, FeCl ₂ concentration=200 mmol/L, AlCl ₃ concentration=100 mmol/L, TiO ₂ concentration=200 mmol/L) was changed. The same procedure as in Production Example 2 was carried out except for the above. In this way, layered double hydroxide containing divalent iron ions, trivalent aluminum ions, and chloride ions (Cl-type Fe(II)-Al(III)-layered double hydroxide) and dioxide A composite compound containing titanium (TiO ₂ composite layered double hydroxide) was prepared. The obtained composite (TiO ₂ composite layered double hydroxide) was observed by SEM and was confirmed to have a particle size of 10 to 5000 nm. Powder X-ray diffraction (XRD) was also performed, and it was confirmed that a layered double hydroxide peak existed in the XRD pattern.

(Manufacturing example 4)
_{A mixture (} molar The ratio (Fe ²⁺ :Al ³⁺ :SiO ₂ )=1:0.5:1, FeCl ₂ concentration=200 mmol/L, AlCl ₃ concentration=100 mmol/L, SiO ₂ concentration=200 mmol/L) was prepared. While stirring this liquid mixture at 1500 rpm, a 5 mol/L aqueous sodium hydroxide (NaOH) solution was added to the mixture to adjust the pH of the mixture to 10 at 25° C. to obtain a suspension. Next, the mixture (suspension) was hydrothermally treated at 120° C. for 24 hours, filtered and washed with water, and dried under reduced pressure. In this way, layered double hydroxide containing divalent iron ions, trivalent aluminum ions, and chloride ions (Cl-type Fe(II)-Al(III)-layered double hydroxide) and dioxide A composite containing silicon (SiO ₂ composite layered double hydroxide) was prepared. The obtained composite (SiO ₂ composite-based layered double hydroxide) was observed by SEM and was confirmed to have a particle size of 10 to 5000 nm. Powder X-ray diffraction (XRD) was also performed, and it was confirmed that a layered double hydroxide peak existed in the XRD pattern.

(Manufacturing example a)
The same procedure as in Production Example 1 was carried out, except that the pH of the mixture when obtaining the suspension was changed to pH 7 (Production Example a1) and pH 11 (Production Example A2) in Production Example 1. performed the operation. It was confirmed that layered double hydroxides containing divalent iron ions, trivalent aluminum ions, and sulfate ions were obtained also in these production examples.

(Manufacturing example b)
In Production Example 2, the same procedure as Production Example 2 was carried out, except that the pH of the mixture when obtaining the suspension was adjusted to 10, which was changed to pH 7 (Production Example b1) and pH 11 (Production Example b2). performed the operation. It was confirmed that layered double hydroxides containing divalent iron ions, trivalent aluminum ions, and chloride ions were obtained also in these production examples.

(Production example c)
Production Example 2 except that "aluminum chloride (AlCl ₃ )" in Production Example 2 was changed to vanadium chloride (VCl ₃ ; Production Example c1) and cerium chloride (CeCl ₃ ; Production Example c2), respectively. A similar operation was performed. It was confirmed that these production examples produced layered double hydroxides containing divalent iron ions, trivalent metal ions (V ³⁺ or Ce ³⁺ ), and chloride ions.

(Manufacturing example d)
The same operations as in Production Example 3 were carried out, except that "AlCl ₃ " in Production Example 3 was changed to vanadium chloride (VCl ₃ ; Production Example d1) and cerium chloride (CeCl ₃ ; Production Example d2), respectively. went. According to these production examples, a composite compound (TiO 2 composite) containing a layered double hydroxide containing divalent iron ions, trivalent metal ions (V ³⁺ or Ce ³⁺ ), and chloride ions, and _titanium dioxide was produced. It was confirmed that a layered double hydroxide (layered double hydroxide) was obtained.

(Manufacturing example e)
The "titanium dioxide (TiO ₂ ) powder" in Production Example 3 was changed to aluminum oxide (Al ₂ O ₃ ) powder (manufactured by MERCK, trade name "Aluminiumoxid") and the mixture (molar ratio (Fe ²⁺ :Al ³⁺ : Production Example 3 except that Al ₂ O ₃ ) = 1:0.5:1, FeCl ₂ concentration = 200 mmol/L, AlCl ₃ concentration = 100 mmol/L, Al ₂ O ₃ concentration = 200 mmol/L). The same operation was performed. According to this production example, a layered double hydroxide containing divalent iron ions, trivalent aluminum ions, and chloride ions, and a composite containing aluminum oxide (layered double hydroxide of Al ₂ O ₃ composite system) ) was confirmed to have been obtained.

<Test Example 1: Organic substance decomposition test 1>
The layered double hydroxide produced in Production Example 1 was used as a heterogeneous Fenton reaction catalyst sample, and a test was conducted to confirm the organic matter decomposition performance (catalytic performance). As the organic substance, phenol or sodium dodecylbenzenesulfonate (hereinafter sometimes abbreviated as "C12LAS-Na") was used. The details will be explained below.

(Test example 1-1)
As a heterogeneous Fenton reaction catalyst sample, 60 mg of the layered double hydroxide produced in Production Example 1 and water were placed in a beaker to prepare 40 mL of an aqueous suspension (heterogeneous) containing them. 0.04 mmol (1 mmol/L) of phenol and 1.2 mmol (30 mmol/L) of hydrogen peroxide (H ₂ O ₂ ) were added to the water suspension in this beaker. In addition, a UV irradiation device ("LED light source controller CL-1501" and "365nm LED head unit (CL-H1-365-9-1)") was installed at a height of 5 cm above the liquid level in the beaker, Asahi Spectroscopic Co., Ltd. ) was fixed. Then, while irradiating the liquid in the beaker with ultraviolet light (UV; light intensity 544 mW/cm ² ) with a wavelength of 365 nm using the UV irradiation device, the beaker is immersed in a water bath, and the beaker is heated using a magnetic stirrer and a stirrer. The solution was stirred for 60 minutes at 25±1°C to react. After the reaction water suspension was filtered through a 0.2 μm membrane filter and H ₂ O ₂ was removed by adding sodium bisulfite, the oxygen demand in the filtrate ( Oxygen consumption by potassium dichromate (COD _Cr (mg/L)) was measured.

(Test example 1-2)
COD _Cr (mg/L) was measured in the same manner as Test Example 1-1 except that the "ultraviolet light" in Test Example 1-1 was not irradiated.

(Test example 1-3)
The procedure was the same as Test Example 1-1, except that "phenol 0.04 mmol (1 mmol/L)" in Test Example 1-1 was changed to "sodium dodecylbenzenesulfonate 0.01 mmol (0.25 mmol/L)". COD _Cr (mg/L) was measured.

(Test example 1-4)
The fact that "ultraviolet rays" in Test Example 1-1 was not irradiated, and "phenol 0.04 mmol (1 mmol/L)" in Test Example 1-1 was replaced with "sodium dodecylbenzenesulfonate 0.01 mmol (0.25 mmol/L)" COD _Cr (mg/L) was measured in the same manner as in Test Example 1-1, except for changing to L).

Each COD _Cr measurement value (post-reaction COD _Cr ) obtained in Test Example 1 (Test Examples 1-1 to 1-4) above and the COD _Cr measurement value before the decomposition reaction in each test example (pre-reaction COD _Cr ) Based on the following formula, the COD _Cr removal rate (%) was calculated. COD _Cr before reaction is obtained by adding phenol or sodium dodecylbenzenesulfonate to an aqueous suspension containing 60 mg of layered double hydroxide and water, and then adding the aqueous suspension before adding hydrogen peroxide to a 0.2 μm membrane. This is the value obtained by measuring COD _Cr in the filtrate after filtration with a filter. In addition, the pre-reaction COD _Cr was 234 mg/L in Test Examples 1-1 and 1-2 due to phenol, and in Test Examples 1-3 and 1-4, it was caused by sodium dodecylbenzenesulfonate. Therefore, it was 178 mg/L.
Formula: COD _Cr removal rate (%) = [(COD _Cr (mg/L) before reaction - COD _Cr (mg/L) after reaction)/COD _Cr (mg/L) before reaction] x 100

Table 1 shows the results of each COD _Cr removal rate obtained in Test Example 1 above. Table 1 also shows the molar ratio (Fe ²⁺ :Al ³⁺ ) of the layered double hydroxide used in each test example, the presence or absence of UV irradiation, and the organic matter to be decomposed.

From the results of Test Example 1, it was found that phenol and sodium dodecylbenzenesulfonate were produced by contacting hydrogen peroxide with a layered double hydroxide containing divalent iron ions, trivalent metal ions (Al ³⁺ ), and anions. It was confirmed that the decomposition reaction of Furthermore, it was confirmed that the decomposition reaction of phenol and sodium dodecylbenzenesulfonate was further accelerated by bringing the layered double hydroxide and hydrogen peroxide into contact under ultraviolet irradiation conditions. From this, it was confirmed that radical generation was further promoted by bringing the layered double hydroxide as a heterogeneous Fenton reaction catalyst into contact with hydrogen peroxide under ultraviolet irradiation conditions. . Therefore, it can be said that a method capable of further promoting the generation of such radicals is expected to be used for the decomposition of various organic substances.

The above-mentioned effects of the layered double hydroxide obtained in Production Example 1 are obtained when each of the layered double hydroxides obtained in Production Example a above is used instead of the layered double hydroxide. However, the case where the layered double hydroxide obtained in Production Example 1 was used was better.

<Test Example 2: Organic substance decomposition test 2>
Regarding the layered double hydroxide produced in Production Example 2 and each composite compound produced in Production Examples 3 and 4 (TiO ₂ composite layered double hydroxide, SiO ₂ composite layered double hydroxide), was used as a heterogeneous Fenton reaction catalyst sample, and a test was conducted to confirm the decomposition performance (catalytic performance) of organic matter. Phenol was used as the organic substance to be decomposed. The details will be explained below.

(Test Example 2-1)
In a transparent reaction container, 30 mg of the layered double hydroxide produced in Production Example 2 and water were placed as a heterogeneous Fenton reaction catalyst sample, to prepare 30 mL of an aqueous suspension (heterogeneous) containing them. To this water suspension were added 20 μmol (0.67 mmol/L) of phenol and 600 μmol (20 mmol/L) of hydrogen peroxide (H ₂ O ₂ ). On the other hand, a solar simulator (manufactured by San-ei Electric Manufacturing Co., Ltd., model "XES-40S2-CE", light intensity: AM-1.5G (100 mW/cm ² )) was installed on the side of the reaction vessel. Then, while irradiating the water suspension in the reaction container with simulated sunlight from the solar simulator from the side of the reaction container, the water suspension was stirred at 30° C. for 60 minutes to react. When phenol is completely decomposed by the reaction, carbon dioxide (CO ₂ ) is produced, as shown in the reaction formula example: C ₆ H ₅ OH + 14H ₂ O ₂ → 6CO ₂ + 17H ₂ O. _Two amounts were determined by gas chromatography (GC) under the conditions shown below. This quantitative determination was performed at each elapsed time of 0, 15, 30, 45, and 60 minutes from the start of _the reaction (addition of phenol and _H2O2 ).
(GC measurement conditions)
・Measuring device: Product name “GC-8A” (manufactured by Shimadzu Corporation)
・Column: Product name “Porapak Q” (manufactured by GL Sciences, Inc.)
・Injection volume: 0.5mL
・Inlet temperature: 100℃
・Column temperature: 60℃
・Carrier gas: Helium (flow rate 20mL/min)
・Detector: TCD
・Detector temperature: 100℃

In addition, based on the quantitative value of the amount of CO ₂ obtained by the above GC, the conversion rate from phenol to CO ₂ (CO ₂ conversion rate (%)) at each elapsed time mentioned above was calculated based on the following formula. .
Formula: CO ₂ conversion rate (%) = [CO ₂ quantitative value after reaction (μmol) / (6 x amount of phenol before reaction (20 μmol))] x 100

(Test example 2-2)
The same test as in Test Example 2-1 was conducted, except that the "simulated sunlight" in Test Example 2-1 was not irradiated, and the CO ₂ conversion rate was calculated.

(Test example 2-3)
Test Example 2-1 except that the "layered double hydroxide produced in Production Example 2" was changed to the composite compound (TiO ₂ composite layered double hydroxide) produced in Production Example 3. A test similar to 2-1 was conducted to calculate the CO ₂ conversion rate.

(Test Example 2-4)
Test Example 2-1 except that the "layered double hydroxide produced in Production Example 2" was changed to the composite compound (SiO ₂ composite layered double hydroxide) produced in Production Example 4. A test similar to 2-1 was conducted to calculate the CO ₂ conversion rate.

(Test Example 2-5)
For reference, except for changing the "layered double hydroxide produced in Production Example 2" in Test Example 2-1 to titanium dioxide (TiO ₂ ; manufactured by Ishihara Sangyo Co., Ltd., product name "ST-01"). A test similar to Test Example 2-1 was conducted to calculate the CO ₂ conversion rate.

Table 2 shows the results of each CO ₂ conversion rate obtained in Test Example 2 (Test Examples 2-1 to 2-5). Table 2 also shows the molar ratio (Fe ²⁺ :Al ³⁺ :TiO ₂ or SiO ₂ ) in the layered double hydroxide used in each test example, and the presence or absence of simulated sunlight irradiation.

The results of Test Example 2 indicate that the layered double hydroxide containing divalent iron ions, trivalent metal ions (Al ³⁺ ), and anions promotes the decomposition reaction of phenol and can decompose it to _CO2 . confirmed. Furthermore, it was confirmed that by bringing the layered double hydroxide and hydrogen peroxide into contact under conditions of irradiation with simulated sunlight, the decomposition reaction of phenol was further promoted and the CO ₂ conversion rate was further increased. Therefore, by bringing the layered double hydroxide as a heterogeneous Fenton reaction catalyst into contact with hydrogen peroxide under irradiation conditions of light containing at least one of ultraviolet rays and visible rays, radical generation can be suppressed. It was recognized that further progress was being made. Therefore, it can be said that a method capable of further promoting the generation of such radicals is expected to be used for the decomposition of various organic substances.

The above-mentioned effects of the layered double hydroxide obtained in Production Example 2 can be obtained by using each of the layered double hydroxides obtained in Production Example b and Production Example C described above instead of the layered double hydroxide. Although this was also observed when using the layered double hydroxide obtained in Production Example 2, it was better when the layered double hydroxide obtained in Production Example 2 was used.

In addition, from the results of Test Example 2-3 and Test Example 2-4, it was found that a composite containing a layered double hydroxide and a specific inorganic oxide (TiO ₂ , SiO ₂ ) (layered composite of TiO ₂ composite system) It was found that the organic matter decomposition performance was further improved by using hydroxide (SiO ₂ composite layered double hydroxide). This effect was also observed when each of the composites obtained in Production Example d above was used, and when the composite obtained in Production Example e above was used, but Production Example 3 and Production Example The results were better when each of the composites obtained in step 4 was used.

Claims (7)

A heterogeneous Fenton reaction catalyst containing a layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions and hydrogen peroxide are irradiated with light including at least one of ultraviolet rays and visible rays. contacting the radicals with an organic substance to be decomposed;
including;
A method for decomposing an organic substance, wherein the trivalent metal ion is at least one selected from the group consisting of trivalent aluminum ions, trivalent vanadium ions, and trivalent cerium ions. The heterogeneous Fenton reaction catalyst includes a composite of the layered double hydroxide and at least one inorganic oxide selected from the group consisting of silicon dioxide, titanium dioxide, and aluminum oxide. Item 1. The method for decomposing organic matter according to item 1 . The layered double hydroxide is a layered double hydroxide represented by the following general formula (A),
3. The method for decomposing an organic substance according to claim 2, wherein the composite has a structure in which the layered double hydroxide represented by the general formula (A) and the inorganic oxide are integrated.
General formula (A): [(Fe ²⁺ ) _1-x (M ³⁺ ) _x (OH) ₂ ][(A ^n- ) _x/n ・yH ₂ O]
(In general formula (A), M ³⁺ represents the trivalent metal ion, and A ^n- represents the n-valent anion, x represents a real number satisfying 0<x<1, and y represents a real number greater than 0. ) The method for decomposing organic matter according to any one of claims 1 to 3, wherein the anion is at least one selected from the group consisting of sulfate ions, nitrate ions, and halogen ions. Any one of claims 1 to 4, wherein the molar ratio of the divalent iron ion to the trivalent metal ion (divalent iron ion:trivalent metal ion) in the layered double hydroxide is 2:1 to 4:1. The method for decomposing organic matter according to item 1. The method for decomposing organic matter according to any one of claims 1 to 5 , comprising bringing the radicals into contact with the organic matter by bringing the radicals into contact with the water to be treated containing the organic matter. Bringing the treated water containing organic matter, the heterogeneous Fenton reaction catalyst, and the hydrogen peroxide into contact under the light irradiation conditions to generate the radicals in the treated water; and The method for decomposing an organic substance according to any one of claims 1 to 6 , comprising bringing the radical and the organic substance into contact in the water to be treated.