JP7333561B2 - Heterogeneous Fenton reaction catalyst, method for producing heterogeneous Fenton reaction catalyst, and method for decomposing organic matter - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act (1) On February 20, 2019, at the graduation thesis presentation of the School of Environmental and Urban Engineering, Kansai University, "Organic reaction by Fenton reaction using Fe-based layered double hydroxide (2) On March 1, 2019, in the Proceedings of the 99th Annual Meeting of the Chemical Society of Japan, "Effective decomposition of organic pollutants (3) At the 99th Spring Annual Meeting of the Chemical Society of Japan on March 19, 2019 Presentation titled "Development of Iron-Based Layered Double Hydroxide Enabling Effective Decomposition and Detoxification of Organic Pollutants"

TECHNICAL FIELD The present invention relates to a heterogeneous Fenton reaction catalyst, a method for producing a heterogeneous Fenton reaction catalyst, and a method for decomposing organic matter.

The Fenton reaction is a reaction that generates hydroxyl radicals from hydrogen peroxide using divalent iron as a catalyst. Iron ions (Fe ²⁺ and Fe ³⁺ ) are widely known as catalysts for the Fenton reaction, ie Fenton reaction catalysts. By using this, hydroxy 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 the strong oxidizing power can be used for, for example, sterilization and decomposition of organic substances (hazardous substances, persistent contaminants, etc.). Therefore, the Fenton reaction is expected to be applied to various fields as one of the clean methods with less environmental load.

Conventionally, the Fenton reaction is generally a homogeneous Fenton reaction using 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 on heterogeneous Fenton reactions using solid iron catalysts in water. As a technique using the heterogeneous Fenton reaction, for example, in Patent Document 1, a catalyst metal-supporting support in which a catalyst metal such as iron is supported on an inorganic support such as zeolite is used. A method for treating organic-containing water is described.

JP 2014-198286 A

For example, in the treatment of wastewater containing oxidizable organic substances as harmful substances and pollutants, when the homogeneous Fenton reaction is used to oxidatively decompose the organic substances in the wastewater, the iron (II) ion used as a catalyst is Since the resulting water-soluble iron(II) salt is transient, it is usually necessary to add the iron(II) salt continuously. 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 unavoidable, and It will occur in relatively large quantities.

On the other hand, when utilizing the heterogeneous Fenton reaction, unlike the transient decomposition technique using a water-soluble iron(II) salt as the iron catalyst in the homogeneous Fenton reaction, a solid iron catalyst can be used repeatedly, the amount of sludge containing compounds derived from the iron catalyst can be reduced. Moreover, in this case, the amount of the chemical (for example, a flocculant, etc.) used for insolubilization for removing the iron catalyst as sludge can also be reduced. Therefore, the heterogeneous Fenton reaction is considered preferable to the homogeneous Fenton reaction in that the catalyst can be easily reused.

However, the heterogeneous Fenton reaction, which uses a solid catalyst, is less efficient than the homogeneous Fenton reaction using a water-soluble iron salt that produces iron ions in water. Therefore, the actual situation is that there is still room for improvement in the catalyst used for the heterogeneous Fenton reaction.

Accordingly, the present invention aims to provide a heterogeneous Fenton reaction catalyst with better catalytic performance.

The present inventors have made intensive studies with the aim of providing the heterogeneous Fenton reaction catalyst described above, and as a result, a layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions and a layered double hydroxide thereof We have found that the amorphous composite hydroxide obtained after the hydroxide structure collapses is useful as a heterogeneous Fenton reaction catalyst. Then, the present inventors have found that the catalyst performance is further improved by further incorporating a specific inorganic oxide into the layered double hydroxide and/or the amorphous composite hydroxide, resulting in the present invention.

From the group consisting of layered double hydroxides and/or amorphous composite hydroxides containing divalent iron ions, trivalent metal ions, and anions, silicon dioxide, titanium dioxide, and aluminum oxide A heterogeneous Fenton reaction catalyst is provided that includes a composite containing at least one selected inorganic oxide.

According to the present invention, a heterogeneous Fenton reaction catalyst with better catalytic performance can be provided.

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

1. Heterogeneous Fenton Reaction Catalyst The heterogeneous Fenton reaction catalyst of one embodiment of the present invention (hereinafter sometimes simply referred to as "heterogeneous Fenton reaction catalyst") comprises bivalent iron ions (Fe ²⁺ ), Composites containing layered double hydroxides and/or amorphous composite hydroxides containing trivalent metal ions and anions, and specific inorganic oxides. The specific inorganic oxide is at least one selected from the group consisting of silicon dioxide, titanium dioxide and aluminum oxide.

The mode of arrangement of the divalent iron ions, the trivalent metal ions, and the anions in the layered double hydroxide is not particularly limited, and any arrangement mode that constitutes the layered double hydroxide can be adopted. A layered double hydroxide has a structure in which a basic layer containing a hydroxide and an intermediate layer containing anions and interlayer water are alternately laminated. and trivalent metal ions are located in the base layer and anions are located in the intermediate layer. The crystal structure of the basic layer is not particularly limited, and any crystal structure can be adopted according to the types of divalent iron ions and trivalent metal ions, the synthesis method, and the like. Layered double hydroxides are amorphous composite hydroxides in which bivalent iron ions, trivalent metal ions, and anions are arranged close to each other even after the layered structure is destroyed by firing treatment, chemical reaction, etc. is formed. Therefore, the composite (and the heterogeneous Fenton reaction catalyst containing it) should contain at least one of the layered double hydroxide and the amorphous composite hydroxide. Since the amorphous composite hydroxide is also originally a layered double hydroxide, in the following description, "layered double hydroxide and/or amorphous composite hydroxide" will be simply referred to as "layered It is sometimes described as "double hydroxide".

The layout of the specific inorganic oxide in the composite can adopt a layout in which the specific inorganic oxide is composited with the layered double hydroxide. From such an arrangement mode, the layered double hydroxide can be called a layered double hydroxide compounded with a specific inorganic oxide (an inorganic oxide compound layered double hydroxide). The specific inorganic oxide in the composite is preferably arranged in such a manner that it is covered with the layered double hydroxide at a position in contact with the layered double hydroxide. As a mode of arrangement of the specific inorganic oxide and the layered double hydroxide in the composite, a state in which the layered double hydroxide is attached around the specific inorganic oxide is more preferable. Such a composite can be obtained, for example, by producing a layered double hydroxide in the presence of a specific inorganic oxide.

In one aspect of the composite, a layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions represented by the following general formula (A) is integrated with a specific inorganic oxide. It is preferable to adopt a configuration that In 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 zero.
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 form a layered double hydroxide together with the divalent iron ion. Examples of trivalent metal ions include trivalent aluminum ions, trivalent vanadium ions, trivalent cerium ions, trivalent lanthanide ions represented by trivalent lanthanum, trivalent iron ions, trivalent chromium ions, and trivalent cobalt. ions, trivalent indium ions, trivalent gallium ions, trivalent scandium ions, trivalent yttrium ions, 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 vanadium ions, and trivalent metal ions are more preferred. Examples include lanthanide ions (preferably trivalent cerium ions), more preferably trivalent aluminum ions and trivalent vanadium ions, and particularly preferably trivalent aluminum ions. Trivalent metal ions may be used singly or in combination of two or more.

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

The anion is not particularly limited as long as it can form 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 strong acid anions such as perbromate ions; and weak acid anions such as carbonate ions, hydrogen carbonate ions, phosphate ions, hydrogen phosphate ions, and carboxylate ions (such as acetate ions). Among these, from the viewpoint of activity as a heterogeneous Fenton reaction catalyst, anions of strong acids are preferable, and among them, sulfate ions, nitrate ions, halogen ions, etc. are more preferable, and sulfate ions, nitrate ions, chloride ions, etc. is more preferred, and sulfate ion is even more preferred. Anions may be used singly 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 to divalent iron ions and the valence of anions. Typically, when the number of moles of a trivalent metal ion is defined as X and the number of valences of an anion is defined as N, the number of moles of anion is X/N.

Although not wishing to be limiting, when the heterogeneous Fenton reaction catalyst and hydrogen peroxide are brought into contact, the peroxide species generated by the reaction between the anion and hydrogen peroxide is 2 in the layered double hydroxide. It greatly contributes to the Fenton reaction on valence iron ions, and combined with the structure of the layered double hydroxide (it is thought that the divalent iron ions and anions are arranged close to each other), the efficiency of the Fenton reaction is further enhanced. it is conceivable that.

Silicon dioxide (SiO ₂ ), titanium dioxide (TiO ₂ ), and aluminum oxide (Al ₂ O ₃ ) are used for layered double hydroxides containing divalent iron ions, trivalent metal ions, and anions described above. It is a component that can further improve the catalytic performance. When the heterogeneous Fenton reaction catalyst contains at least one inorganic oxide selected from the group consisting of SiO ₂ , TiO ₂ , and Al ₂ O ₃ and does not contain those specific inorganic oxides Compared to , the organic substance decomposition performance is better. SiO ₂ and TiO ₂ are more preferable as the inorganic oxides from the viewpoint of catalytic performance and organic substance decomposition performance.

From the viewpoint of further improving catalytic performance and further improving organic substance decomposition performance, the molar ratio of the inorganic oxide to the divalent iron ion in the layered double hydroxide and/or amorphous composite hydroxide is 0.01. ~2 is preferred. The range of this molar ratio is more preferably 0.05 or more, more preferably 0.1 or more, more preferably 1.5 or less, and even more preferably 1 or less.

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

The average particle size of the composite is not particularly limited. Smaller particles are desirable from the viewpoint of Fenton reaction efficiency. The average particle size of the layered double hydroxide constituting the composite is preferably, for example, 10 nm to 5000 nm. The particles may be granulated into, for example, platelets, spheres, rods, and polyhedra for ease of manipulation, and may be applied to solid surfaces. The average particle diameter of the granulated particles is preferably 1 mm to 50 mm, for example.

The heterogeneous Fenton reaction catalyst may consist of only a composite (layered double hydroxide and specific inorganic oxide) or may contain other substances. Other substances include, for example, impurities that are unavoidably mixed in when producing the layered double hydroxide, other inorganic substances, and amorphous composite hydroxide obtained after the structure of the layered double hydroxide collapses. etc. The other substance may be integrated with the layered double hydroxide or separate from the layered double hydroxide.

The content of the composite is, for example, 50% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more with respect to the total mass (100% by mass) of the heterogeneous Fenton reaction catalyst. can be The upper limit of this content can be, for example, 99.9% by mass, 99% by mass, or 97% by mass.

In one aspect, the heterogeneous Fenton reaction catalyst is preferably used together with hydrogen peroxide and used to decompose organic substances by radicals generated by contact with hydrogen peroxide. By bringing the heterogeneous Fenton reaction catalyst into contact with hydrogen peroxide, radicals can be generated and organic substances can be decomposed by the radicals. For this reason, composites and heterogeneous Fenton reaction catalysts containing them are radical generation catalysts, radical generation ability imparting agents, radical generation ability improving agents, organic matter decomposition catalysts, organic matter decomposition imparting agents, organic matter decomposition improvement agents, etc. can also be used as

In one aspect, the heterogeneous Fenton reaction catalyst is more preferably used by being brought into contact with hydrogen peroxide under irradiation conditions of light in the region from ultraviolet rays to infrared rays. Since the heterogeneous Fenton reaction catalyst contains a specific inorganic oxide, contacting the heterogeneous Fenton reaction catalyst with hydrogen peroxide under the above light irradiation conditions makes it easier to generate radicals. The radicals make it easier to decompose organic substances. From this point of view, the light is preferably at least one of ultraviolet light and visible light such as sunlight. The wavelength of light is preferably 200 to 3000 nm, more preferably 200 to 900 nm, even more preferably 300 to 700 nm.

2. Next, as a suitable method for producing the heterogeneous Fenton reaction catalyst described above, a method for producing a heterogeneous Fenton reaction catalyst according to one embodiment of the present invention (hereinafter simply referred to as It may be described as a “method for producing a heterogeneous Fenton reaction catalyst”).

This method for producing a heterogeneous Fenton reaction catalyst includes at least one selected from the group consisting of salts of divalent iron ions and anions; salts of trivalent metal ions and anions; silicon dioxide, titanium dioxide, and aluminum oxide. and water; adjusting the pH of the mixture to 3 to 14 at 25° C. to obtain a suspension, divalent iron ion, trivalent metal ion , and obtaining a composite containing an anion-containing layered double hydroxide and/or amorphous composite hydroxide, and the inorganic oxide. Thereby, a heterogeneous Fenton reaction catalyst containing the composite can be produced.

By "preparing the 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 ions, trivalent metal ions, anions, and specific inorganic oxides used in "preparing the mixture" are the same as those described in "1. Heterogeneous Fenton reaction catalyst" above. .

The salt of a ferrous ion and an anion (ferric salt) used for preparing the mixture varies depending on the type of anion employed in the layered double hydroxide, but examples thereof include FeCl ₂ , FeF ₂ and FeBr _{2 .} , FeI ₂ , FeSO ₄ , Fe(NO ₃ ) 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 a trivalent metal ion and an anion (trivalent metal salt) used for preparing the mixture varies depending on the type of anion employed in the layered double hydroxide, but examples thereof include AlCl ₃ , AlF ₃ and AlBr _{3 .} , _AlI3 , _Al2 ( _SO4 ) ₃ , Al( _NO3 ) ₃ , _VCl3 , _VF3 , VBr3, _{VI3 , V2} ( _SO4 ) ₃ , V( _NO3 ) ₃ , CeCl3 _, CeF ₃ , _CeBr3 , _CeI3 , _Ce2 ( _SO4 ) ₃ , Ce( _NO3 ) ₃ , FeCl3 _{, FeF3} , _FeBr3 , _FeI3 , _Fe2 ( _SO4 ) ₃ , Fe( _NO3 ) _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 and trivalent metal (divalent iron: trivalent metal) is not particularly limited as long as it is a molar ratio that allows synthesizing a layered double hydroxide. The molar ratio of bivalent iron and trivalent metal (bivalent 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 (divalent iron salt) or a salt of a trivalent metal ion and an anion (trivalent metal salt). It is preferably an 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 with respect to 100% by mass of the liquid medium of the reaction liquid.

Layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions as solids from the suspension by "obtaining a suspension" in the method for producing a heterogeneous Fenton reaction catalyst, and / Or a composite containing an amorphous composite hydroxide and a specific inorganic oxide can be obtained. A suspension can be obtained by adjusting the pH of the above mixture (reaction solution) to 3-14. The pH value of the above-mentioned mixture when obtaining this suspension is a value at 25° C., but the temperature of the mixture when obtaining the suspension is not particularly limited. °C), preferably in the range of 15 to 30°C.

A known pH adjuster can be used to adjust the pH of the mixture (reaction solution). Examples of the pH adjuster include alkalis such as sodium hydroxide and calcium hydroxide, and acids such as hydrochloric acid and sulfuric acid. 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 facilitating the formation of precipitates in the mixture (reaction solution) and making it easier to obtain the suspension. is more preferable, and adjusting to 7 to 14 is even more preferable.

In this method for producing a heterogeneous Fenton reaction catalyst, after the suspension is obtained, even at room temperature, the suspension is converted from the layered double hydroxide and / or amorphous composite hydroxide and the specific inorganic oxidation A composite containing the substance can be obtained. On the other hand, from the viewpoint of increasing the crystallinity of the layered double hydroxide in the resulting composite, the suspension is preferably heat-treated, more preferably hydrothermally treated. As a result, the temperature applied to the suspension is preferably 20 to 200 ° C., more preferably 60 to 140 ° C., more preferably 100 to 140 ° C., from the viewpoint of easy synthesis of the layered double hydroxide. It is even more preferable to have When the suspension is heated by hydrothermal treatment or the like, the heating time is, for example, preferably 1 to 100 hours, preferably 12 to 72 hours, from the viewpoint of easily obtaining a layered double hydroxide. is more preferred, and 12 to 48 hours is even more preferred.

A solid complex can be obtained from the suspension obtained as described above. At this time, the suspension is preferably filtered or washed with water, and then dried under reduced pressure. The obtained substance (composite containing layered double hydroxide and specific inorganic oxide) can be used as a heterogeneous Fenton reaction catalyst as it is or mixed with other substances.

In addition, if necessary, it can be confirmed that the heterogeneous Fenton reaction catalyst contains a layered double hydroxide according to or according to a known method. For example, a powder X-ray diffraction pattern can be obtained to determine whether or not layered double hydroxide peaks are included.

3. Method for Decomposing Organic Substances As described above, the heterogeneous Fenton reaction catalyst of one embodiment of the present invention described in detail above can be used in a radical generation method including contacting with hydrogen peroxide in one aspect thereof. Therefore, it can be used in the following method for decomposing organic matter. That is, the method for decomposing organic matter according to one embodiment of the present invention (hereinafter sometimes simply referred to as “method for decomposing organic matter”) comprises contacting the aforementioned heterogeneous Fenton reaction catalyst with hydrogen peroxide. generating radicals; and contacting the radicals with the organic matter to be decomposed.

Radicals generated by contact of the heterogeneous Fenton reaction catalyst with hydrogen peroxide are not particularly limited, but are considered to be mainly hydroxyl radicals. The mode of contact between the heterogeneous Fenton reaction catalyst and hydrogen peroxide is not particularly limited as long as radicals are generated by their contact. The heterogeneous Fenton reaction catalyst and hydrogen peroxide can be contacted, 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, it can be carried out 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 composite is, for example, preferably 0.001 to 10% by mass, and 0.01 to 2% by mass. is more preferable, and 0.05 to 0.5% by mass is even more preferable. Further, when the catalyst is molded and filled in the reactor, the concentration of the heterogeneous Fenton reaction catalyst in water is preferably 1 to 50% by mass, for example, 2 to 20% in terms of the concentration of the composite. % by mass is more preferred. The concentration of hydrogen peroxide in water before the reaction is not particularly limited, and is, for example, preferably 0.1 to 500 mmol/L, more preferably 1 to 200 mmol/L, and 1 to 100 mmol/L. more preferably 2 to 20 mmol/L.

The mode of contact between the radicals and the organic substance to be decomposed is not particularly limited. The contact between the radical and the organic substance can be carried out, for example, by mixing the heterogeneous Fenton reaction catalyst, hydrogen peroxide and the organic substance. Also, the contact between the radicals and the organic matter can usually be carried out in the presence of water, for example, in water containing a heterogeneous Fenton reaction catalyst, hydrogen peroxide, and an organic matter. In this case, radicals (hydroxy radicals) are generated from hydrogen peroxide in the water by the action of the heterogeneous Fenton reaction catalyst, and the radicals can be brought into contact with organic matter. 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 substances 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. is more preferred.

The temperature during contact between the heterogeneous Fenton reaction catalyst and hydrogen peroxide is not particularly limited as long as the temperature allows the Fenton reaction to proceed. These temperatures are, for example, preferably 0 to 100°C, more preferably 10 to 50°C, even more preferably 15 to 40°C. The contact time is not particularly limited as long as a certain amount of radicals are generated, and is, for example, 1 minute to 3 hours, preferably 15 minutes to 2 hours.

One aspect of the method for decomposing organic matter is preferably employed in a method (water treatment method) for treating water containing organic matter to be decomposed (water to be treated). This water treatment method preferably includes contacting water to be treated containing organic matter, a heterogeneous Fenton reaction catalyst, and hydrogen peroxide. As a result, the heterogeneous Fenton reaction catalyst and hydrogen peroxide are brought into contact with each other in the water to be treated, and radicals can be generated from hydrogen peroxide by the action of the heterogeneous Fenton reaction catalyst. It can be brought into contact with treated water. Further, as a result, the generated radicals can be brought into contact with organic substances in the water to be treated, and the organic substances can be oxidatively decomposed by the radicals. In the present specification, the water to be treated means 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. be done.

The manner of contact between the water to be treated, the heterogeneous Fenton reaction catalyst, and hydrogen peroxide (contact between the water to be treated and radicals) is not particularly limited. For example, by mixing the water to be treated, a heterogeneous Fenton reaction catalyst, and hydrogen peroxide, they can be brought into contact with each other, and their contact can be carried out in a predetermined tank (reaction tank). Suitably, hydrogen peroxide and a heterogeneous Fenton reaction catalyst can be added to the water to be treated containing organic matter to bring them into contact. Further, as another more preferable aspect, the heterogeneous Fenton reaction catalyst is supported on a carrier and fixed in a reaction tank, and in the reaction tank, the water to be treated and the heterogeneous system The Fenton reaction catalyst can be contacted with hydrogen peroxide. For example, it can be configured such that the water to be treated is transferred to a reaction tank in which a carrier (catalyst carrier) on which a heterogeneous Fenton reaction catalyst is supported is installed, and the reaction tank (inside the reaction tank It can be configured to add hydrogen peroxide to the water to be treated).

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

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 dissolved in a solution and used. Therefore, the method for decomposing organic matter of the present 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 catalysts (specific heterogeneous Fenton reaction catalysts) repeatedly. In addition, this leads to the ability to suppress the generation of sludge containing compounds derived from the catalyst, and the ability to suppress the use of insolubilizing agents (such as flocculants) for removing the catalyst as sludge. . Therefore, it can be expected to realize a useful water treatment method with reduced sludge disposal costs and catalyst costs. From the viewpoint of easily obtaining these effects, the heterogeneous Fenton reaction catalyst is preferably used in a state in which it is supported and fixed on the carrier described above.

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, dioxin contaminants, and the like.

Organic aliphatic substances can be cyclic, acyclic, saturated or unsaturated hydrocarbons. These hydrocarbons are cyclic or acyclic alkanes and alkenes, preferably chlorinated, halogenated cyclic or acyclic alkanes and alkenes, saturated and/or unsaturated aliphatic and/or cycloaliphatic Formula 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 fatty substance may also have a hydroxy group such as an alcohol, a carboxyl group such as a fatty acid, or an oxyacid such as a sulfonic acid, It may be an oxygen-containing compound such as an ether group such as dioxane, and may contain elements other than carbon, hydrogen, and oxygen (eg, nitrogen, sulfur, etc.).

The organic aliphatic material is preferably trichloropropane, preferably 1,2,3-trichloropropane, chloropropenol, preferably 2-chloro-2-propen-1-ol, dichloropropene, preferably 1,3-dichloropropane. 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 of the} approximate _{formulas C6H10Cl2O2 , C6H12Cl2O , C6H9Cl3O2 , C6H11Cl3O2 , acrolein} , _{methylglycidyl} 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 aromatics contain at least one ring of aromatic character. They are preferably halogenated aromatic hydrocarbons containing at least one ring of aromaticity and one halogen atom. Halogen may be selected from fluorine, chlorine, bromine, iodine, preferably chlorine. The aromatic ring may be mononuclear or polynuclear, preferably mononuclear. Organic aromatic substances are preferably selected from mono-, di-, tri-, tetra-, penta- and hexachlorobenzenes and/or naphthalenes, and mixtures thereof. The organic aromatic substance is preferably monochlorobenzene. The organic aromatic substance may also have a hydroxy group such as phenol, a carboxy group such as benzoic acid, or an oxyacid such as benzenesulfonic acid. It may contain elements other than carbon, hydrogen, and oxygen (such as nitrogen and sulfur) and may contain chain structures such as alkylbenzene sulfonic acids.

Dioxin contaminants include, for example, halogenated dibenzodioxins, halogenated dibenzofurans, PCBs (in particular, coplanar PCBs in which chlorine atoms are substituted at positions other than the ortho position), and the like.

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, 1,2,3,4,6,7,8-heptachlorodibenzofuran, 1,2,3,4,6,7,8,9-octachlorodibenzofuran and the like.

Examples of PCBs (especially coplanar PCBs with chlorine atoms substituted in positions 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.

As described above, one embodiment of the present invention can adopt the following configuration.
[1] Selected from the group consisting of layered double hydroxides and/or amorphous composite hydroxides containing divalent iron ions, trivalent metal ions, and anions, and silicon dioxide, titanium dioxide, and aluminum oxide A heterogeneous Fenton reaction catalyst comprising a composite containing at least one inorganic oxide and at least one inorganic oxide.
[2] The above-mentioned [1], wherein the molar ratio of the inorganic oxide to the ferric ion in the layered double hydroxide and/or the amorphous composite hydroxide is 0.01 to 2. Heterogeneous Fenton reaction catalyst.
[3] The heterogeneous Fenton reaction catalyst according to the above [1] or [2], which is used together with hydrogen peroxide and used for decomposing organic substances by radicals generated by contact with the hydrogen peroxide.
[4] The heterogeneous Fenton reaction catalyst according to the above [3], which is used in contact with the hydrogen peroxide under irradiation conditions of light in the region from ultraviolet rays to infrared rays.
[5] a salt of a divalent iron ion and an anion; a salt of a trivalent metal ion and an anion; at least one inorganic oxide selected from the group consisting of silicon dioxide, titanium dioxide, and aluminum oxide; and adjusting the pH of said mixture to 3 to 14 at 25° C. to obtain a suspension containing said divalent iron ions, said trivalent metal ions, and said anions obtaining a composite containing a layered double hydroxide and/or an amorphous composite hydroxide and the inorganic oxide; producing a heterogeneous Fenton reaction catalyst containing the composite; Method.
[6] The method for producing a heterogeneous Fenton reaction catalyst according to [5] above, which comprises hydrothermally treating the suspension after obtaining the suspension.
[7] Contacting the heterogeneous Fenton reaction catalyst according to any one of [1] to [4] above with hydrogen peroxide to generate radicals; and contacting the radicals with an organic substance to be decomposed. a method of decomposing organic matter, comprising:

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>
(Production example 1)
Contains iron (II) sulfate (FeSO ₄ ), aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), titanium dioxide (TiO ₂ ) powder (manufactured by Ishihara Sangyo Co., Ltd., trade name “ST-01”), and pure water A mixture (molar ratio (Fe ²⁺ : Al ³⁺ : TiO ₂ ) = 2:1:2, FeSO ₄ concentration = 200 mmol/L, Al ₂ (SO ₄ ) ₃ concentration = 100 mmol/L, TiO ₂ concentration = 200 mmol/L ) was prepared. While this liquid mixture was stirred at 1500 rpm, a 5 mol/L sodium hydroxide (NaOH) aqueous solution was added to the mixture to adjust the pH of the mixture to 10 at 25° C. to obtain a suspension. Then, the mixture (suspension) was hydrothermally treated at 120° C. for 24 hours, filtered, washed with pure water, and dried under reduced pressure. Thus, a layered double hydroxide containing divalent iron ions, trivalent aluminum ions, and sulfate ions (SO ₄ ^2- type Fe(II)-Al(III)-layered double hydroxide), A composite containing titanium dioxide (TiO ₂ composite system layered double hydroxide) was prepared. The resulting composite (TiO ₂ composite layered double hydroxide) was observed with an SEM and confirmed to have a particle size of 10 to 5000 nm. Moreover, powder X-ray diffraction (XRD) was performed, and it was confirmed that a layered double hydroxide peak was present in the XRD pattern.

(Production example 2)
Compared with Production _{Example 1, layered double hydroxide (SO 2 -type} ^Fe (II)-Al(III)-layered double hydroxide) was prepared. The resulting layered double hydroxide was observed with an SEM and confirmed to have a particle size of 10 to 5000 nm. Moreover, powder X-ray diffraction (XRD) was performed, and it was confirmed that a layered double hydroxide peak was present in the XRD pattern.

(Production example 3)
_{A mixture} ( _mol A ratio (Fe ²⁺ :Al ³⁺ :SiO ₂ )=1:0.5:0.01, FeCl ₂ concentration=200 mmol/L, AlCl ₃ concentration=100 mmol/L, SiO ₂ concentration=2 mmol/L) was prepared. While this liquid mixture was stirred at 1500 rpm, a 5 mol/L sodium hydroxide (NaOH) aqueous solution was added to the mixture to adjust the pH of the mixture to 10 at 25° C. to obtain a suspension. The mixture (suspension) was then hydrothermally treated at 120° C. for 24 hours, filtered, washed with water, and dried under reduced pressure. In this way, a 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 ( _Si02 composite-based layered double hydroxide) was prepared. The obtained composite (SiO ₂ composite system layered double hydroxide) was observed with an SEM and confirmed to have a particle size of 10 to 5000 nm. Moreover, powder X-ray diffraction (XRD) was performed, and it was confirmed that a layered double hydroxide peak was present in the XRD pattern.

(Production Examples 4-7)
Layered _double hydroxide (Cl ^- type Fe(II)-Al(III )-layered double hydroxide) and silicon dioxide (SiO ₂ composite system layered double hydroxide) were prepared. Specifically, in Production Example 4, a mixture containing FeCl ₂ , AlCl ₃ , SiO ₂ powder, and pure water (molar ratio (Fe ²⁺ :Al ³⁺ :SiO ₂ )=1:0.5:0.1 , FeCl ₂ concentration = 200 mmol/L, AlCl ₃ concentration = 100 mmol/L, SiO ₂ concentration = 20 mmol/L). Further, in Production Example 5, a mixture containing FeCl ₂ , AlCl ₃ , SiO ₂ powder, and pure water (molar ratio (Fe ²⁺ : Al ³⁺ : SiO ₂ )=1:0.5:0.5, FeCl ₂ concentration = 200 mmol/L, AlCl ₃ concentration = 100 mmol/L, SiO ₂ concentration = 100 mmol/L). In Production Example 6, a mixture containing FeCl ₂ , AlCl ₃ , SiO ₂ powder, and pure water (molar ratio (Fe ²⁺ : Al ³⁺ : SiO ₂ ) = 1:0.5:0.87, FeCl ₂ concentration = 200 mmol/L, AlCl ₃ concentration=100 mmol/L, SiO ₂ concentration=174 mmol/L). Furthermore, in Production Example 7, a mixture containing FeCl ₂ , AlCl ₃ , SiO ₂ powder, and pure water (molar ratio (Fe ²⁺ : Al ³⁺ : SiO ₂ )=1:0.5:1.00, FeCl ₂ concentration = 200 mmol/L, AlCl ₃ concentration = 100 mmol/L, SiO ₂ concentration = 200 mmol/L). Each of the obtained composites (SiO ₂ composite system layered double hydroxide) was observed with an SEM and confirmed to have a particle size of 10 to 5000 nm. Moreover, powder X-ray diffraction (XRD) was performed, and it was confirmed that a layered double hydroxide peak was present in the XRD pattern.

(Production Example 8)
A mixture containing FeCl ₂ , AlCl ₃ , TiO ₂ powder (manufactured by Ishihara Sangyo Co., Ltd., trade name “ST-01”) and pure water (molar 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). While this liquid mixture was stirred at 1500 rpm, a 5 mol/L sodium hydroxide (NaOH) aqueous solution was added to the mixture to adjust the pH of the mixture to 10 at 25° C. to obtain a suspension. The mixture (suspension) was then hydrothermally treated at 120° C. for 24 hours, filtered, washed with water, and dried under reduced pressure. In this way, a 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 titanium (TiO ₂ composite system layered double hydroxide) was prepared. The resulting composite (TiO ₂ composite layered double hydroxide) was observed with an SEM and confirmed to have a particle size of 10 to 5000 nm. Moreover, powder X-ray diffraction (XRD) was performed, and it was confirmed that a layered double hydroxide peak was present in the XRD pattern.

(Production Example 9)
A mixture containing FeCl ₂ , AlCl ₃ , aluminum oxide (Al ₂ O ₃ ) powder (manufactured by MERCK, trade name “Aluminiumoxide”), and pure water (molar ratio (Fe ²⁺ : Al ³⁺ : 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). While this liquid mixture was stirred at 1500 rpm, a 5 mol/L sodium hydroxide (NaOH) aqueous solution was added to the mixture to adjust the pH of the mixture to 10 at 25° C. to obtain a suspension. The mixture (suspension) was then hydrothermally treated at 120° C. for 24 hours, filtered, washed with water, and dried under reduced pressure. In this way, layered double hydroxides containing divalent iron ions, trivalent aluminum ions, and chloride ions (Cl ^- type Fe(II)-Al(III)-layered double hydroxides) and oxidized A composite containing aluminum (an Al ₂ O ₃ composite layered double hydroxide) was prepared. The resulting composite (layered double hydroxide of Al ₂ O ₃ composite system) was observed with an SEM and confirmed to have a particle size of 10 to 5000 nm. Moreover, powder X-ray diffraction (XRD) was performed, and it was confirmed that a layered double hydroxide peak was present in the XRD pattern.

(Production Example 10)
Compared with Production Example 3, layered double hydroxide (Cl ^- type Fe(II)-Al(III)-layered double hydroxide was prepared in the same manner as in Production Example 3 except that _SiO powder was not used. oxide) was prepared. The resulting layered double hydroxide was observed with an SEM and confirmed to have a particle size of 10 to 5000 nm. Moreover, powder X-ray diffraction (XRD) was performed, and it was confirmed that a layered double hydroxide peak was present in the XRD pattern.

(Manufacturing example a)
In Production Example 1, the same procedure as in Production Example 1 except that the pH of the mixture when obtaining the suspension was adjusted to 10 was changed to pH 7 (Production Example a1) and pH 11 (Production Example a2). performed the operation. According to these production examples as well, a layered double hydroxide containing divalent iron ions, trivalent aluminum ions, and sulfate ions (SO ₄ ^2- type Fe(II)-Al(III)-layered double hydroxide) and titanium dioxide (TiO ₂ composite system layered double hydroxide) was obtained.

(Manufacturing example b)
In Production Example 7, the same procedure as in Production Example 7 except that the pH of the mixture when obtaining the suspension was adjusted to 10 was changed to pH 7 (Production Example b1) and pH 11 (Production Example b2). performed the operation. According to these production examples, layered double hydroxides containing divalent iron ions, trivalent aluminum ions, and chloride ions (Cl ^- type Fe(II)-Al(III)-layered double hydroxides) and , and silicon dioxide (SiO ₂ composite layered double hydroxide) was obtained.

(Manufacturing example c)
Production Example 7 and Production Example 7, except that "aluminum chloride (AlCl ₃ )" in Production Example 7 was changed to vanadium chloride (VCl ₃ ; Production Example c1) and cerium chloride (CeCl ₃ ; Production Example c2), respectively. A similar operation was performed. According ^{to these} production examples, composite compounds (SiO ₂ composite It was confirmed that a layered double hydroxide of the system) was obtained.

(Manufacturing example d)
Production Example 8 and Production Example 8, except that "aluminum chloride (AlCl ₃ )" in Production Example 8 was changed to vanadium chloride (VCl ₃ ; Production Example d1) and cerium chloride (CeCl ₃ ; Production Example d2), respectively. A similar operation was performed. According to these ^production examples ^, a composite (TiO ₂ composite It was confirmed that a layered double hydroxide of the system) was obtained.

<Test Example 1: Organic substance decomposition test 1>
For each of the composite (TiO ₂ composite system layered double hydroxide) prepared in Production Example 1 and the layered double hydroxide prepared in Production Example 2, they were used as heterogeneous Fenton reaction catalyst samples, and organic substances A test was conducted to confirm the decomposition performance (catalytic performance) of As the organic substance, phenol or sodium dodecylbenzenesulfonate (hereinafter sometimes abbreviated as “C12LAS-Na”) was used. The details will be described below.

(Test Example 1-1)
In a beaker, 60 mg of the composite (TiO ₂ composite system layered double hydroxide) prepared in Production Example 1 and water are put as a heterogeneous Fenton reaction catalyst sample, and a water suspension containing them (heterogeneous system ) 40 mL was prepared. 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, and the temperature range of 25±1° C. was added in the beaker. The mixture was stirred for 60 minutes to react. The aqueous suspension after the reaction was filtered with a 0.2 μm membrane filter, and after removing H ₂ O ₂ by adding sodium hydrogen sulfite, the oxygen demand in the filtrate ( Oxygen consumption by potassium dichromate; COD _Cr (mg/L)) was measured.

(Test Example 1-2)
Test Example 1-1 except that the “composite (TiO ₂ composite layered double hydroxide) prepared in Production Example 1” was changed to the layered double hydroxide prepared in Production Example 2. COD _Cr (mg/L) was measured in the same manner as in 1-1.

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

(Test Example 1-4)
The “composite (TiO ₂ composite layered double hydroxide) prepared in Production Example 1” in Test Example 1-1 was changed to the layered double hydroxide prepared in Production Example 2, and Test Example 1 In the same manner as in Test Example 1-1, COD _Cr (mg/L) was measured.

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

Table 1 shows the COD _Cr removal rate results obtained in Test Example 1 above. Table 1 also shows the molar ratio (Fe ²⁺ : Al ³⁺ : TiO ₂ ) and the molar ratio of TiO ₂ to divalent iron ions (TiO ₂ /Fe ²⁺ ) in the layered double hydroxide used in each test example. show.

From the results of Test Example 1, it was found that the layered double hydroxide containing divalent iron ions, trivalent metal ions (Al ³⁺ ), and anions accelerates the decomposition reaction of phenol and sodium dodecylbenzenesulfonate. confirmed. Furthermore, it was confirmed that the decomposition reaction of phenol and sodium dodecylbenzenesulfonate is further accelerated by a composite material containing the layered double hydroxide and TiO ₂ (TiO ₂ composite layered double hydroxide). . This indicates that the composite containing the layered double hydroxide and TiO ₂ (TiO ₂ composite system layered double hydroxide) further promotes radical generation as a heterogeneous Fenton reaction catalyst. Admitted. Accordingly, it can be said that the above composite (TiO ₂ composite layered double hydroxide) can be expected to be used as a heterogeneous Fenton reaction catalyst for decomposing various organic substances.

Note that the above-described effects of the composite (TiO ₂ composite layered double hydroxide) obtained in Production Example 1 can be obtained by using each of the composites obtained in Production Example a above instead of the composite. Although this was also observed in the case of using the composite obtained in Production Example 1, it was better.

<Test Example 2: Organic substance decomposition test 2>
For each of the composites (inorganic oxide composite layered double hydroxide) prepared in Production Examples 3 to 9 and the layered double hydroxide prepared in Production Example 10, they were used as a heterogeneous Fenton reaction catalyst sample. A test was conducted to confirm the decomposition performance of organic matter (catalytic performance). Phenol was used as the organic substance to be decomposed. The details will be described below.

(Test Example 2-1)
As a heterogeneous Fenton reaction catalyst sample, 30 mg of the composite (SiO ₂ composite system layered double hydroxide) prepared in Production Example 3 and water are added, and 20 mL of an aqueous suspension (heterogeneous system) containing them is prepared. did. 20 μmol (1 mmol/L) of phenol and 600 μmol (30 mmol/L) of hydrogen peroxide (H ₂ O ₂ ) were added to this aqueous suspension, and the mixture was stirred at 30° C. for 60 minutes to react. When the phenol is completely decomposed by the reaction, carbon dioxide (CO ₂ ) is produced, as in the reaction formula example: C ₆ H ₅ OH + 14H ₂ O ₂ → 6CO ₂ + 17H ₂ O. ₂ was quantified by gas chromatography (GC) under the conditions shown below. This quantification was performed every 0, 15, 30, 45, and 60 minutes after initiation of the above reaction (addition of phenol and H ₂ O ₂ ).
(GC measurement conditions)
・ Measuring device: Product name “GC-8A” (manufactured by Shimadzu Corporation)
・ Column: Product name “Porapak Q” (manufactured by GL Sciences Co., Ltd.)
・Injection volume: 0.5mL
・Inlet temperature: 100°C
・Column temperature: 60°C
・Carrier gas: helium (flow rate 20 mL/min)
・Detector: TCD
・Detector temperature: 100°C

In addition, based on the quantitative value of the amount of _CO2 obtained by the above GC, the conversion rate from phenol to _CO2 ( _CO2 conversion rate (%)) at each elapsed time described above was calculated based on the following formula. .
Formula: _CO2 conversion rate (%) = [ _CO2 quantitative value after reaction (μmol) / (6 × amount of phenol before reaction (20 μmol))] × 100

(Test Examples 2-2 to 2-5)
In Test Examples 2-2 to 2-5, the “composite (SiO ₂ composite layered double hydroxide) prepared in Production Example 3” in Test Example 2-1 was prepared in Production Examples 4 to 7, respectively. The same test as in Test Example 2-1 was performed, except that a composite (SiO ₂ composite layered double hydroxide) was used, and the CO ₂ conversion rate was calculated.

(Test Example 2-6)
The “composite (SiO ₂ composite layered double hydroxide) prepared in Production Example 3” in Test Example 2-1 was replaced with the composite (TiO ₂ composite layered double hydroxide) prepared in Production Example 8. , the amount of water added to the complex was changed, the amount of the prepared water suspension (heterogeneous system) was changed from 20 mL to 30 mL, and the water suspension contained phenol and H ₂ O During the reaction for 60 minutes after adding ₂ , the same test as in Test Example 2-1 was performed except that the reaction system (water suspension) was irradiated with simulated sunlight from the side of the reaction vessel. , the _CO2 conversion was calculated. As the simulated sunlight, a solar simulator (model "XES-40S2-CE" manufactured by Sannaga Electric Manufacturing Co., Ltd., light intensity: AM-1.5G (100 mW/cm ² )) was used.

(Test Example 2-7)
The “composite (SiO ₂ composite layered double hydroxide) prepared in Production Example 3” in Test Example 2-1 was replaced with the composite (Al ₂ O ₃ composite layered double hydroxide) prepared in Production Example 9. The same test as in Test Example 2-1 was performed, except that the material was changed to a substance), and the CO ₂ conversion rate was calculated.

(Test Example 2-8)
The “composite (SiO ₂ composite layered double hydroxide) prepared in Production Example 3” in Test Example 2-1 was replaced with the composite (SiO ₂ composite layered double hydroxide) prepared in Production Example 7. , the amount of water added to the complex was changed, the amount of the prepared water suspension (heterogeneous system) was changed from 20 mL to 30 mL, and the water suspension contained phenol and H ₂ O During the reaction for 60 minutes after adding ₂ , the reaction system (water suspension) was irradiated with simulated sunlight from the side of the reaction vessel in the same manner as in Test Example 2-6. A test similar to 2-1 was performed to calculate the CO ₂ conversion rate.

(Test Example 2-9)
Test Example 2-1 except that the “composite (SiO ₂ composite layered double hydroxide) prepared in Production Example 3” was changed to the layered double hydroxide prepared in Production Example 10. A test similar to 2-1 was performed to calculate the CO ₂ conversion rate.

Table 2 shows the CO ₂ conversion rate results obtained in Test Example 2 (Test Examples 2-1 to 2-9). Table 2 shows the composite inorganic oxide species (SiO ₂ , TiO ₂ or Al ₂ O ₃ ) and molar ratios (Fe ²⁺ : Al ³⁺ : SiO ₂ , TiO) in the layered double hydroxides used in each test example. ₂ , or Al ₂ O ₃ ) are also shown.

From the results of Test Example 2, the layered double hydroxide containing divalent iron ions, trivalent metal ions (Al ³⁺ ), and anions accelerates the decomposition reaction of phenol, and can be decomposed to CO ₂ . confirmed. Furthermore, a composite (inorganic oxide composite layered double hydroxide) containing the layered double hydroxide and a specific inorganic oxide (SiO ₂ , TiO ₂ , Al ₂ O ₃ ), that is, 2 A layered double hydroxide containing valence iron, Al ³⁺ , an anion, and a specific inorganic oxide (layered double hydroxide of a specific inorganic oxide composite system) further promotes the decomposition reaction of phenol, resulting in CO ₂ A higher conversion rate was confirmed. From this, the composite containing the layered double hydroxide and a specific inorganic oxide (layered double hydroxide of inorganic oxide composite system) further promotes radical generation as a heterogeneous Fenton reaction catalyst. It was recognized that

In addition, the above-described effects of the composite ( _SiO composite-based layered double hydroxide) and the like obtained in Production Example 7 were obtained in the above-mentioned Production Examples b and c instead of the composite. Although this was also observed when using each of the composites, it was better when using the composite obtained in Production Example 7.

Further, from the results of Test Examples 2-6 and 2-8, the composite (inorganic oxide composite layered double hydroxide) was irradiated with H ₂ It was found that the organic matter decomposition performance was further improved by using it in contact with O ₂ . This effect was also observed when using each of the composites obtained in Production Examples d and c, but when using each of the composites obtained in Production Examples 8 and 7, the was better.

From the results of Test Example 2 above, it can be expected that the layered double hydroxide of the specific inorganic oxide composite system can be used as a heterogeneous Fenton reaction catalyst to decompose various organic substances. I can say.

Claims (9)

A composite containing a layered double hydroxide containing divalent iron ions, trivalent metal ions, and anions, and at least one inorganic oxide selected from the group consisting of silicon dioxide, titanium dioxide, and aluminum oxide A heterogeneous Fenton reaction catalyst comprising a compound. 2. The heterogeneous Fenton reaction catalyst according to claim 1, wherein the molar ratio of said inorganic oxide to divalent iron ions in said layered double hydroxide is 0.01-2. 3. The heterogeneous Fenton reaction catalyst according to claim 1 or 2, 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 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. 5. Any one of claims 1 to 4, wherein the molar ratio of the divalent iron ions and the trivalent metal ions in the layered double hydroxide (bivalent iron ions:trivalent metal ions) is 2:1 to 4:1. 2. The heterogeneous Fenton reaction catalyst according to claim 1 . 6. The heterogeneous Fenton reaction catalyst according to any one of claims 1 to 5, which is used together with hydrogen peroxide and used for decomposing organic substances by radicals generated by contact with the hydrogen peroxide. 7. The heterogeneous Fenton reaction catalyst according to claim 6 , which is used by being brought into contact with the hydrogen peroxide under irradiation conditions of light in the region from ultraviolet rays to infrared rays. a salt of a divalent iron ion and an anion; a salt of a trivalent metal ion and an anion; at least one inorganic oxide selected from the group consisting of silicon dioxide, titanium dioxide, and aluminum oxide; and a mixture containing water and
Adjusting the pH of the mixture at 25 ° C. to 7 to 14 to obtain a suspension , and after obtaining the suspension, subjecting the suspension to hydrothermal treatment , obtaining a composite containing the layered double hydroxide containing the trivalent metal ion and the anion, and the inorganic oxide; producing a heterogeneous Fenton reaction catalyst containing the composite; Method. contacting the heterogeneous Fenton reaction catalyst according to any one of claims 1 to 6 with hydrogen peroxide to generate radicals; and contacting the radicals with an organic substance to be decomposed;
A method of decomposing organic matter, comprising: