TWI490037B - Photocatalyst, process for preparing the same, photocatalyst coating agent, photocatalyst dispersion and photocatalyst article using the same - Google Patents

Description

Photocatalyst and manufacturing method thereof, photocatalyst coating agent using the same, photocatalyst dispersion, and light contact medium

The present invention relates to a photocatalyst and a method for producing the same, and a photocatalyst coating agent, a photocatalyst dispersion, and a photocatalyst using the same. More specifically, it relates to a photocatalyst having excellent catalytic activity by light irradiation such as a white fluorescent lamp.

The photocatalyst is excited by irradiating light having a wavelength of energy higher than the band gap, and exhibits strong catalytic activity. In particular, organic matter, or a part of inorganic substances such as NOx, has a large degree of oxidation and decomposing power, and it is possible to use light with low cost and low environmental load as an energy source, and in recent years, it has progressed to environmental purification or deodorization, antifouling, sterilization, and the like. Application. Moreover, when the photocatalyst is excited, it is found that the surface is hydrophilic and the contact angle with water is lowered; by this action, the application to anti-turbidity and anti-fouling can also be developed. As the photocatalyst, a metal compound such as an oxide or a sulfide is used, and in particular, titanium oxide, zinc oxide or the like having fine particles of high photocatalytic activity is used. Titanium oxide, zinc oxide, etc., the wavelength of the excitation light is in the ultraviolet region of 400 nm. For example, the inside and/or the surface of the titanium oxide particles contains an iron compound such as iron oxide, iron hydroxide or oxyhydroxide iron, and the photocatalytic activity can be enhanced (see Patent Document 1). In addition, the surface of the titanium oxide particles is loaded with fine particles of iron oxide of 10 to 100 Å, and the utilization efficiency of sunlight can be improved (see Patent Document 2). There is also a proposal to support iron oxides such as ferrous oxide, iron oxide, and magnetite on the surface of anatase-type titanium oxide particles, and to obtain high activity by irradiating visible light. (Refer to Patent Document 3).

Patent Document 1: Japanese Patent Publication No. 7-303835

Patent Document 2: Japanese Laid-Open Patent Publication No. Hei 6-39285

Patent Document 3: JP-A-2003-190811

A photocatalyst having photocatalytic activity by visible light irradiation does not require a special light source such as an ultraviolet lamp, and a light source such as a sunlight or a white fluorescent lamp can be used, and the application field of the photocatalyst is expected to be more extensive; Patent Documents 2 and 3 Photocatalyst, photocatalytic activity under the illumination of white fluorescent light is not sufficient. Accordingly, the present invention has an object of providing a photocatalyst having excellent photocatalytic activity and a method for producing the same by irradiation with a white fluorescent lamp or the like.

In the work of the present invention, in order to develop a titanium oxide photocatalyst having excellent activity even in the case of a white fluorescent lamp, it has been intensively studied and found that various iron compounds are used in combination. a light-containing catalyst containing light of a white fluorescent lamp, absorbing light of a wavelength of 400 to 500 nm; a photocatalyst containing such an iron hydroxide and titanium oxide, under the irradiation of light of a white fluorescent lamp, under the same conditions The photocatalyst activity of about 2 times or more was measured as compared with the titanium oxide which does not use the iron oxyhydroxide, and this invention was completed.

That is, the present invention has the following features.

(1) It is a photocatalyst containing at least iron oxyhydroxide and titanium oxide. The titanium oxide exhibits photocatalytic activity by absorbing light of a wavelength of 400 to 500 nm by iron oxyhydroxide. In such a photocatalyst, when irradiating light of a white fluorescent lamp containing light having a wavelength of 400 to 500 nm, the acetaldehyde decomposition reaction rate constant is about twice as high as the acetaldehyde decomposition rate constant of the titanium oxide measured under the same conditions. The above photocatalyst activity.

(2) The method for producing a photocatalyst according to the present invention, wherein at least the basic hydrogen hydride is mixed with titanium oxide, preferably in a vehicle containing titanium oxide containing an alkali metal element and/or an alkaline earth metal element, The reaction is carried out by adding an iron compound, and iron oxyhydroxide is supported on the surface of the particles of the titanium oxide to contain iron oxyhydroxide and titanium oxide.

(3) in a photocatalyst containing at least iron oxyhydroxide and titanium oxide, by using a binder as a photocatalyst coating agent; or by dispersing a dispersing medium as a photocatalyst dispersion; and further containing at least oxygen hydride The photocatalyst of iron oxide and titanium oxide is formed and fixed on the substrate.

The photocatalyst of the present invention has excellent photocatalytic activity under light irradiation such as a white fluorescent lamp having a wavelength of 400 to 500 nm, and does not require a special light source such as an ultraviolet lamp, even indoor illumination such as a fluorescent lamp or sunlight. It can effectively decompose NOx or organic environmental pollutants. The hydrophilic effect can also be expected, and it is suitable for use as a purification material, a deodorizing material, an antifouling material, a sterilizing material, an anti-turbid material, and the like. In addition, low-cost materials such as titanium oxide and iron oxyhydroxide can provide low-cost light touch. Media.

Further, the photocatalyst of the present invention can be used as a liquid composition such as a coating agent or a dispersion, and can be formed as a photo-contacting medium fixed to a substrate, and can be used for imparting antifouling properties or hydrophilic properties. .

[Embodiment of the Invention]

The present invention is a photocatalyst containing at least iron oxyhydroxide and titanium oxide; the titanium oxide exhibits photocatalytic activity by absorbing light having a wavelength of 400 to 500 nm by iron oxyhydroxide. Therefore, the photocatalytic activity is measured by measuring the acetaldehyde decomposition reaction rate constant as an evaluation criterion (refer to evaluation 1 described later) when irradiating light of a white fluorescent lamp containing light having a wavelength of 400 to 500 nm. The activity of the photocatalyst of the present invention thus evaluated is preferably about 2 times or more, more preferably about 5 times or more, based on the activity of the titanium oxide itself measured by the same conditions (as assessed by the acetaldehyde decomposition reaction rate constant). Further preferably, it is about 7 times or more, and most preferably about 10 times or more. The photocatalyst of the present invention preferably contains at least iron oxyhydroxide and titanium oxide, and absorbs light having a wavelength of 400 to 500 nm by ferric oxyhydroxide to exhibit photocatalytic activity of titanium oxide, and iron oxyhydroxide and titanium oxide. The state of engagement of the degree of interaction is preferably such that the state of strong bonding is better. In such a state, it is preferred to mix the iron oxyhydroxide and the titanium oxide, preferably by mixing with a mixer, and it is more preferable to mix the iron oxyhydroxide and the titanium oxide in a suspended state using a stirrer or the like. Preferably, the iron oxyhydroxide is supported on the surface of the particles of titanium oxide. The supported form of the iron oxyhydroxide is not particularly limited; it may be in a state of being adsorbed on the surface of the titanium oxide particles, or may be a titanium oxide particle in the form The surface has a state in which a hydroxyl group and a hydrogen bond are firmly bonded. In the photocatalyst, photocatalyst coating agent, photocatalyst dispersion, and photocontact medium of the present invention, in addition to iron oxyhydroxide and titanium oxide, photocatalytic substances such as zinc oxide and cadmium sulfide, various adsorbents, and the like may be contained. There are no special restrictions.

The iron oxyhydroxide contained in the photocatalyst of the present invention is a compound represented by a chemical formula of FeOOH or Fe ₂ O ₃ ‧nH ₂ O; and crystallinity such as an α state, a β state, or a γ state, or an amorphous form can be used. In particular, α-iron oxyhydroxide has a high absorption effect on light having a wavelength of 400 to 500 nm, and is highly suitable for imparting a photocatalyst having superior activity. The content of the iron oxyhydroxide may be appropriately set, and is preferably in the range of 0.01 to 5% by weight, more preferably 0.05 to 2% by weight, based on the total amount of the iron oxyhydroxide and the titanium oxide. Whether or not the titanium oxide contains or supports iron oxyhydroxide; more specifically, whether or not the alpha oxyhydroxide is contained or supported can be confirmed by, for example, a Moessbauer spectroscopic method or an electron microscope.

The titanium oxide contained in the photocatalyst of the present invention contains anhydrous titanium oxide, hydrous titanium oxide, hydrous titanium oxide, titanium hydroxide, titanic acid, etc. in addition to general titanium oxide; and is anatase or rutile. The crystal form is not particularly limited, and may be amorphous or may be a mixture of the same. Among them, especially those with high crystallinity and high photocatalytic activity are suitable; the wavelength of the excitation light of rutile-type titanium oxide is slightly larger than that of anatase, and the titanium oxide having rutile crystal is more preferable. good. Further, a part of the titanium oxide may be a composite oxide such as an alkali metal titanate or an alkali metal titanate; and the interior of the titanium oxide contains an alkali metal element or an alkaline earth metal element constituting the composite oxide thereof. Therefore, it is extremely suitable. Further, in the titanium oxide, if it does not adversely affect the excitation, it may contain a heterogeneous element selected from one or more selected from the group consisting of V, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, and Au. Or a compound of a different element such as an oxide. The size of the titanium oxide is not limited, and the specific surface area measured by the BET method is preferably in the range of about 10 to 400 m ² /g, more preferably in the range of about 10 to 200 m ² /g, and in the range of 10 to 100 m ² /g. The range is also better, and the range of 30~80m ² /g is most suitable. When the specific surface area is smaller than the above range, the adsorption efficiency of the substance to be treated such as an organic substance or a nitrogen oxide is lowered, and the decomposition efficiency is lowered. Therefore, it is not suitable; when it is too large, it is too fine, and it is difficult to obtain a high crystallinity, which is not suitable.

The particle shape of the titanium oxide is not particularly limited, and a shaped particle such as a true spherical shape, a slightly spherical shape, or an anisotropic shape, or an amorphous particle such as a lumpy block may be used. In particular, when it has an anisotropic shape, superior photocatalytic activity can be easily obtained, and it is preferable. The term "anisotropic shape" as used in the present invention is generally referred to as a spindle-shaped particle, a rod-shaped particle, an acicular particle, a plate-like particle or the like; it means that one primary particle is at a stable state in a stable state. In the plane, the projection image on the plane is held by two parallel lines, and the distance between the parallel lines is the smallest or the short axis diameter w, and the two parallel lines are in the right angle direction. The distance at which the parallel lines hold the particles is the length of the particles or the long axis diameter l, and when the distance held by the surface parallel to the maximum stable surface is the particle height h, the one satisfying l>w≧h is satisfied. The long axis diameter, the short axis diameter, and the height can be obtained by taking the primary particles from an electron microscope photograph by an arithmetic mean of about 1000 particles. The size of the titanium oxide having an anisotropic shape used in the present invention is preferably in the range of 10 to 200 m ² /g, more preferably in the range of 10 to 100 m ² /g, and 30 to 80 m, as measured by the BET method described above. The range of ² / g is most suitable. Such anisotropically shaped particles preferably have an average major axis diameter in the range of 10 to 500 nm and an average minor axis diameter in the range of 1 to 25 nm; wherein the axial ratio (average major axis diameter / average minor axis diameter) The spindle-shaped particles, the rod-shaped particles, and the acicular particles are preferably 1.5 or more; the axial ratio is preferably in the range of 1.5 to 10, and most preferably in the range of 2 to 7.

Further, when a photocatalyst containing titanium oxide and iron oxyhydroxide contains an alkali metal element and/or an alkaline earth metal element, it is excellent in photocatalytic activity. The surface of the titanium oxide particles may have an alkali metal element or an alkaline earth metal element, and may be contained inside as described above; or may be contained in the interior of the iron oxyhydroxide or on the surface of the iron oxyhydroxide. Or it may exist in any two places selected from these. In particular, when the inside and/or the surface of the titanium oxide is contained, the iron oxyhydroxide can be strongly loaded and the like, and it can have excellent photocatalytic activity, and is extremely suitable. Further, a part of the titanium oxide may be a composite oxide of an alkali metal titanate or a metal titanate. The alkali metal elements are sodium, potassium, lithium, and the like. The alkaline earth metal elements are calcium, magnesium, strontium, barium, strontium and the like. Among them, sodium oxyhydroxide is easily formed by the absorption of light having a wavelength of 400 to 500 nm by sodium, which is suitable. The content of the alkali metal element and/or the alkaline earth metal element is equivalent to the content of the iron oxyhydroxide and the titanium oxide in terms of oxide (for example, Na ₂ O, K ₂ O, Li ₂ O, CaO, MgO, BaO, When it is represented by SrO, BeO or the like, it is preferably in the range of 0.01 to 30% by weight, more preferably 0.05 to 15% by weight, and most preferably 0.05 to 5% by weight. The form of the alkali metal element or the alkaline earth metal element may be any one of an ion, a metal, or a compound such as an oxide, a hydroxide or a chloride, and is not particularly limited. Further, the chemical composition of the present invention also includes the content of iron oxyhydroxide and the like, and is an analysis value of all fluorescent X-rays.

Next, in the production of the photocatalyst of the present invention containing at least iron oxyhydroxide and titanium oxide, (a) pre-manufactured iron oxyhydroxide and titanium oxide, using a Hanschel mixer, a Ley blender, and love Mixing machine such as mixer, sputum cabinet, nipple, milk stick, etc.; mixing method using a pulverizing mixer such as a ball mill or a colloid mill; or mixing iron oxyhydroxide and titanium oxide in a suspended state using a mixer (b) a method in which a mixture of a titanium compound and an iron compound and a basic compound described later are mixed and neutralized to carry out a reaction to precipitate both of iron oxyhydroxide and titanium oxide, and (c) is preliminarily produced. In the suspension of titanium oxide, an iron compound is added to carry out a reaction to form iron oxyhydroxide in the presence of titanium oxide, and (d) a titanium compound is added to a suspension of iron oxyhydroxide prepared in advance to carry out a reaction. A method of producing titanium oxide in the presence of iron oxyhydroxide. When these methods are used, photocatalytic substances such as zinc oxide and cadmium sulfide, various adsorbents, and the like may be contained depending on the demand.

When pre-manufacturing iron oxyhydroxide, a basic compound such as sodium hydroxide, potassium hydroxide, ammonia, amine or sodium carbonate may be added to a solution of a ferrous compound such as ferrous sulfate, ferrous nitrate or ferrous chloride. Neutralizing part or all of the ferrous compound; secondly, adjusting the pH and simultaneously feeding air, oxygen, and the like to oxidize; in a solution of an iron compound such as iron sulfate, iron nitrate, or ferric chloride, Adding a basic compound such as sodium hydroxide, potassium hydroxide, ammonia, amine or sodium carbonate to iron the compound, for example, at a temperature of 10 to 70 ° C After the neutralization, the method of aging treatment or heat treatment or hydrothermal treatment is used. When an alkaline sodium compound is used, it is easy to form iron oxyhydroxide which absorbs light of 400 to 500 nm, which is suitable. The ripening treatment in this method is to maintain the neutralization product at a neutralization temperature for a certain period of time to form an iron oxyhydroxide treatment, and the ripening time is preferably 10 minutes to 5 hours. The heat treatment is carried out by neutralizing the product in the range of 50 to 200 ° C in the vehicle, more preferably in the range of 70 to 100 ° C to produce iron oxyhydroxide, and the heating time is preferably 10 minutes to 5 hours. . When the temperature of the heat treatment is lower than 50 ° C, dehydration is difficult in a short time, and it is difficult to sufficiently modify the iron hydroxide to become iron oxyhydroxide, which is extremely unsuitable. In the hydrothermal treatment, the neutralized product is heated in a high temperature and high pressure apparatus such as an autoclave at a temperature of 100 ° C or higher, preferably 150 to 200 ° C, to form iron oxyhydroxide under a water vapor pressure corresponding to the temperature. The heating time is more suitable for 10 minutes to 5 hours. When the temperature of the hydrothermal treatment is higher than 200 ° C, excessive dehydration and easy modification to iron oxide are not suitable. The obtained iron oxyhydroxide can be subjected to an appropriate filtration, washing, drying, or the like by a usual method.

When titanium oxide is previously produced, a well-known method can be used. For example, (1) a method of neutralizing titanium chloride or the like; (2) a method of heating and hydrolyzing titanium sulfate, titanyl sulfate, or the like; (3) a method obtained by the methods (1) and (2) The product is produced by calcination or hydrothermal treatment. Further, titanium oxide having an anisotropic shape may be produced by a known method. For example, a method in which hydrous titanium oxide is treated with a basic sodium compound such as sodium hydroxide, sodium carbonate or sodium oxalate can be treated with hydrochloric acid. Oxidation obtained in this way Titanium-based fine particles, which are so-called spindles, are suitable for use. The obtained titanium oxide can be subjected to an appropriate filtration, washing, drying, or the like using a usual method.

The titanium oxide containing an alkali metal element or an alkaline earth metal element in advance according to the method (B) described later is a titanium oxide obtained by the above method or a titanium oxide precursor described below, and an alkali metal or an alkaline earth metal hydrogen. An oxide, a carbonate, a sulfate, a chloride, an oxide, or the like is preferably obtained by mixing a sodium compound and baking it. The titanium oxide precursor refers to a compound which is formed into titanium oxide by firing. For example, titanium sulfate, titanium sulfate, titanium chloride, titanium alkoxide, and the like. When the hydrous titanium oxide or titanium hydroxide is fired as titanium oxide, the hydrous titanium oxide or titanium hydroxide is a titanium oxide precursor. Further, the titanium oxide containing an alkali metal element or an alkaline earth metal element in advance, in the method (1), neutralizes the titanium oxide with a basic compound of a large excess alkali metal or an alkaline earth metal; more preferably, In a solution of an alkali compound of an alkali metal or an alkaline earth metal, titanium chloride is added to neutralize it. Similarly, the titanium oxide having an anisotropic shape is obtained by treating the aqueous titanium oxide or titanium chloride with a large excess of the sodium compound, preferably by adding the aqueous titanium oxide to the solution of the basic sodium compound. Thereafter, it is obtained by a method of hydrochloric acid treatment. Titanium oxide and sodium having an anisotropic shape obtained by this method are contained in the inside of the particles in an ion state.

The titanium oxide of the present invention is obtained by pre-baking titanium oxide or firing a titanium oxide precursor. The titanium oxide has high crystallinity, and the amount of hydroxyl or water contained therein is moderately decreased, and the photocatalytic activity is further improved. Very suitable. The firing temperature is preferably in the range of 200 to 700 ° C; the firing temperature is lower than this range. When it is around, it is difficult to obtain an improvement effect of photocatalytic activity, and it is not suitable. When it is higher than this range, it is difficult to obtain an improvement effect, and it is easy to cause sintering between the particles of the photocatalyst which is formed or grown, and it is extremely unsuitable. A preferred firing temperature range is from 200 to 600 ° C, and a more preferred range is from 300 to 600 ° C. The firing time, the firing gas atmosphere, and the like can be appropriately set; the firing time is suitably, for example, 1 to 10 hours, and the gas atmosphere is fired in a gas atmosphere of air or an oxygen-containing gas, or nitrogen. It is suitable to carry out in an inert gas atmosphere such as argon.

In the present invention, as described in (c), an iron compound is added to a suspension of titanium oxide prepared in advance to carry out a reaction, and when iron oxyhydroxide is formed in the presence of titanium oxide, oxygen oxide is easily supported on the surface of the titanium oxide particles. Iron oxide, supported iron oxyhydroxide and iron oxide interaction can show superior photocatalytic activity, more suitable. A more preferable method in the method is: (A) adding an iron compound to a medium containing titanium oxide, performing an oxidation or ripening treatment, a heat treatment or a hydrothermal treatment, and (B) using an alkali metal element and/or Or a titanium oxide of an alkaline earth metal element, in contact with an iron compound, neutralizing the iron compound by an alkali metal element or an alkaline earth metal element eluted from the titanium oxide; oxidizing or aging the resultant product, and performing heat treatment or heat treatment Or a hydrothermal treatment, a method of reacting, and (C) a compound containing titanium oxide and an alkali metal element and/or an alkaline earth metal element in a vehicle, and then adding an iron compound for neutralization to oxidize the neutralized product or A method of performing a ripening treatment, a heat treatment or a hydrothermal treatment to carry out a reaction. (B) The method described is that it is not necessary to additionally add a basic compound of a neutralizing agent, and the steps are quite reasonable; it is the most suitable for the present invention. method. Further, according to the method described in (B) and (C), the iron oxyhydroxide may be supported on the surface of the titanium oxide particles and contain an alkali metal element and/or an alkaline earth metal element. Further, in the method (C), an iron compound and an alkali metal element and/or an alkaline earth metal element may be separately added to the vehicle, or may be simultaneously added in parallel.

In the methods (A), (B), and (C) described above, inorganic or organic liquids such as water, alcohol, and toluene can be used as the vehicle liquid, and industrial water treatment is easily suitable. Using a ferrous compound as an iron compound, adding a basic compound such as sodium hydroxide, potassium hydroxide, ammonia, an amine or sodium carbonate to the solution to neutralize part or all of the ferrous compound; then, adjusting the pH, At the same time, a gas such as air or oxygen is supplied for oxidation, and iron hydroxide particles may be loaded with iron hydroxide; when an iron compound is used, a step of not requiring oxidation is particularly suitable. When an aqueous medium is used, it is preferred to use a water-soluble iron compound. The water-soluble iron compound is, for example, iron nitrate, iron sulfate, iron chloride or the like. Alkali metal compound, alkaline earth metal compound, such as hydroxide, carbonate, sulfate, chloride, oxide, etc.; in the photocatalyst of the present invention, the alkali metal element is preferably sodium, and sodium is used. Compounds are more suitable. When the titanium oxide is in contact with the iron compound, the alkali metal element or the alkaline earth metal element contained in the inside or the outside of the titanium oxide particle is easily released, and the reaction with the iron compound can be promoted, and it is preferably carried out under acidic conditions. The pH of the vehicle is preferably 3 or less, more preferably 2 or less. When the pH is adjusted, sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid or the like can be used.

When the product containing titanium oxide and iron oxyhydroxide thus obtained is pulverized, it can be appropriately filtered, washed, dried, etc. by a usual method. Operation; crushing can also be carried out according to demand. Drying is carried out at a temperature at which iron oxyhydroxide is not modified to iron oxide, and is preferably carried out at a temperature of 200 ° C or lower. When filtering and washing, the pH of the vehicle is near neutral, preferably after adjusting the pH to about 7, and the titanium oxide agglomerates to improve the detergency; the unreacted iron in the medium When the compound is present, the iron hydroxide is precipitated, filtered and washed in advance, and the unreacted iron compound is removed and dispersed in the vehicle. Conversely, the pH of the medium is adjusted to the neutral vicinity, and the mixture is filtered and washed. The net is better. As the neutralizing agent, a basic alkali metal compound such as a hydroxide or a carbonate, a basic alkaline earth metal compound, or ammonia, an amine or the like can be used. The vehicle is dispersed and used, preferably water.

When the photocatalyst of the present invention is actually used in the photocatalytic reaction, it is convenient to form the photocatalyst and granulate as a molded body by fixing it to a substrate according to the demand. The substrate is formed of various materials such as metal, ceramic tile, porous body, cement, concrete, glass, plastic, fiber, wood, paper, etc.; the shape can be plate-shaped, wave-shaped, honeycomb-shaped, spherical, curved. Shapes and other shapes.

When the photocatalyst is fixed to the substrate, the photocatalyst is used as a photocatalyst coating agent. After the coating agent is applied or sprayed onto the surface of the substrate, a method of drying or baking can be used. The photocatalyst coating agent contains at least a binder. An inorganic resin or an organic resin can be used for the binder. The binder which is difficult to decompose by photocatalytic reaction is preferably, for example, a polymerizable hydrazine compound, cement, concrete, gypsum, polyoxyxylene resin, fluororesin or the like, wherein the polymerizable hydrazine compound has high durability, is relatively easy to handle, and is versatile. High, very suitable. The polymerizable hydrazine compound may, for example, be a hydrolyzable decane or a hydrolyzate thereof or a partial condensate thereof, water glass, colloidal cerium oxide, or organic polyoxane. One type of these may be used, or two or more types may be used in combination. The hydrolyzable decane contains at least one hydrolyzable group such as an alkoxy group or a halogen group, and the alkoxy decane has excellent stability and economy, particularly tetraalkoxy such as tetramethoxy decane or tetraethoxy decane. The hydrazine is highly reactive and is very suitable. As the water glass, sodium citrate, potassium citrate or lithium silicate can be used, and among them, sodium citrate is highly stable, and is extremely suitable. Sodium citrate-based water glass, when the molar ratio of Na ₂ O to SiO _{2 is in} the range of 2 to 4, the hardenability is high; from the balance between stability and hardenability, the molar ratio is 3 to 3 Water glass is the most suitable. For colloidal cerium oxide or organopolyoxy siloxane, those having a stanol group can be used. The coating agent may further contain water or a nonaqueous solvent such as an alcohol, a hydrocarbon, an ether, an ether alcohol, an ester, an ether ester or a ketone as a dispersion medium; and the compatibility with the binder may be used. One of these types or a mixture of two or more kinds of solvents is appropriately selected and used. The solid content concentration in the coating agent is preferably in the range of 0.05 to 50% by weight, more preferably in the range of 0.1 to 40% by weight. The photocatalyst is preferably 20 to 95% by weight of the solid content, more preferably 40 to 95% by weight.

The coating agent may contain a pH adjuster, a dispersant, an antifoaming agent, an emulsifier, a colorant, and an extender in addition to the photocatalyst, the binder, or the dispersion medium, without impairing the effects of the present invention. , various agents such as fungicides, hardening aids, and tackifiers, fillers, etc. When such additives or fillers are non-volatile, it is preferred to select an inorganic one which is difficult to decompose by photocatalytic action.

The photocatalyst of the present invention can be dispersed in a dispersion medium in advance to form a dispersion. When a photocatalyst coating agent using a dispersion is prepared, a high degree of dispersibility can be easily obtained, which is suitable. Alternatively, the dispersion may be applied to the surface of the substrate at a suitable concentration without using a binder, or after spraying, dried, and fired to fix the photocatalyst to the substrate. The dispersion medium of the dispersion is the same as the dispersion medium to be blended with the coating agent, or one having a high compatibility is selected. Further, a dispersant may be blended in the dispersion, and the type of the dispersant may be appropriately selected depending on the dispersing medium. Examples of the dispersing agent include (1) surfactants {(a) anionic systems [carboxylates, sulfate salts, sulfonates, phosphate salts, etc.], (b) cationic systems [alkylamine salts, alkylamines) a quaternary ammonium salt, an aromatic quaternary ammonium salt, a heterocyclic quaternary ammonium salt, etc., and (c) an amphoteric (betaine type, amino acid type, alkylamine oxide, nitrogen-containing heterocyclic type, etc.), (d) nonionic system (ether type, ether ester type, ester type, nitrogen type, etc.), (2) polyfluorene-based dispersant [alkyl modified polyoxyalkylene, polyalkylene oxide modified poly a phthalocyanine or the like, (3) a phosphate dispersant [sodium phosphate, sodium pyrophosphate, sodium orthophosphate, sodium metaphosphate, sodium tripolyphosphate, etc.], (4) an alkanolamine [aminomethyl propyl acrylate] Alcohol, aminomethyl propylene glycol, etc., etc. Among them, a carboxylate-based surfactant, especially a polymer type, is highly suitable for highly dispersing titanium oxide. Specifically, there is a polyacrylate {[CH ₂ CH(COOM)] _n , M is an alkali metal, an alkaline earth metal, an ammonium, etc., and the following are the same as the acrylate-acrylamide copolymer {[CH ₂ CH( COOM)] _n -[CH ₂ CH(CONH ₂ ) _m ]}, acrylic acid-maleate copolymer {[CH ₂ CH(COOH)] _n -[CH ₂ CH(COOM)CH(COOM)] _m }, ethylene-maleate copolymer {[CH ₂ CH ₂ ] _n -[CH(COOM)CH(COOM)] _m }, olefin-maleate copolymer {[CH ₂ CH (R)] _n -[CH(COOM)CH(COOM)] _m }, styrene-maleate copolymer {[CH ₂ CH(C ₆ H ₅ )] _n -[CH(COOM)CH (COOM)] _m } and so on. The amount of the photocatalyst in the dispersion is preferably in the range of 5 to 90% by weight, more preferably in the range of 10 to 80% by weight. Further, the amount of the dispersing agent is preferably 0.01 to 20% by weight based on the photocatalyst, and more preferably 0.01 to 10% by weight.

When the photocatalyst is used for molding, it can be molded into an arbitrary shape by mixing with a binder such as clay, diatomaceous earth, an organic resin, or an inorganic resin.

[Examples]

Next, the invention will be described by way of examples; the invention is not limited thereto.

[Example 1]

(1) A solution of sodium hydroxide having a concentration of 100 g/l of Na ₂ O was added to 700 ml of an aqueous solution of titanium tetrachloride having a concentration of 200 g/l of TiO ₂ . Thereafter, after adjusting the pH of the system to 7, the mixture was filtered and washed until the conductivity of the filtrate was 100 μS/cm, and dried to obtain titanium oxide.

This titanium oxide is a spindle-shaped titanium oxide having a rutile crystal having an average major axis diameter of 64 nm, an average minor axis diameter of 13 nm (axial ratio of 4.9), and a specific surface area of 160 m ² /g, and the inside of the titanium oxide particles contains 1.7% by weight. Sodium Na ₂ O.

(2) 50 g of the spindle-shaped titanium oxide was added to 0.5 L of pure water. Stirring was carried out to obtain a dispersion, and the pH was adjusted to 1 using sulfuric acid. Next, an aqueous solution of ferric nitrate corresponding to 0.2% by weight of Fe in terms of Fe was added and mixed, and iron nitrate was neutralized by the sodium component contained in the titanium oxide, and heating was continued at 90 ° C for 1 hour. After the heat treatment, it was filtered; the obtained dehydrated cake of the titanium oxide tweezers was further dispersed in 0.5 L of pure water. The pH of the redispersed liquid was neutralized to about 7 with sodium hydroxide, filtered, washed, dried at 110 ° C for 1 day and 1 night, and then pulverized by a cabinet machine to obtain a photocatalyst of the present invention (sample A). .

In the sample A, α-iron oxyhydroxide was supported on the surface of the titanium oxide particles, and was confirmed by analysis by Mesbauer spectroscopy. Further, Sample A contained 0.2% by weight of α-iron oxyhydroxide and 1.7% by weight of sodium of Na ₂ O in terms of Fe.

[Example 2]

The unfired spindle-shaped titanium oxide used in Example 1 was calcined at 350 ° C for 5 hours to obtain a specific surface area of 63 m ² /g, an average major axis diameter of 38 nm, and an average minor axis diameter of 19 nm (axis). The rutile-type fired spindle-shaped titanium dioxide (sample a) having a ratio of sodium to 0.2) and a sodium content of 0.25% by weight of Na ₂ O.

The photocatalyst (sample B) of the present invention was obtained in the same manner as in Example 1 except that the fired spindle-shaped titanium oxide was used instead of the unfired spindle-shaped titanium oxide.

In the sample B, α-iron oxyhydroxide was supported on the surface of the titanium oxide particles, and was confirmed by analysis by Mesbauer spectroscopy. Further, the sample B contained 0.1% by weight of Fe-calcium hydroxide and 0.26% by weight of sodium of Na ₂ O in terms of Fe.

[Example 3]

(1) 1 L of an aqueous solution of 80 g/l of a titanium sulfate-based solution was heated and maintained at a temperature of 85 ° C for 3 hours to be hydrolyzed. The hydrolyzate thus obtained is filtered, washed, and dried to obtain titanium oxide. This titanium oxide is a spherical titanium oxide having an anatase type crystal; it has an average particle diameter of 4.5 nm and a specific surface area of 320 m ² /g, and alkali metal elements and alkaline earth metal elements are not analyzed.

(2) 50 g of the spindle-shaped titanium oxide was added to 0.5 L of pure water, and the mixture was stirred to obtain a dispersion liquid, and the pH was adjusted to 1 using sulfuric acid. Next, an aqueous solution of iron nitrate equivalent to 0.2% by weight in terms of Fe and sodium hydroxide in terms of Fe were added and mixed, and iron nitrate was neutralized, and heat treatment was further continued at 90 ° C for 1 hour. After the heat treatment, the obtained dehydrated cake of titanium oxide was redispersed in 0.5 L of pure water through filtration. After neutralizing with sodium hydroxide until the pH of the redispersion was about 7, the mixture was filtered, washed, and dried at 110 ° C for one day and one night, and then pulverized by a cabinet machine to obtain a photocatalyst of the present invention (sample C).

This sample C, α-iron oxyhydroxide was supported on the surface of the titanium oxide particles, and was confirmed by analysis by Mesbauer spectroscopy. Further, Sample C contained α-iron oxyhydroxide in an amount of 0.25% by weight in terms of Fe, and an alkali metal element such as sodium or an alkaline earth metal element was not analyzed.

[Example 4]

The spindle-shaped titanium dioxide used in Example 1 and α-oxygen oxyhydroxide Iron (manufactured by Ishihara Sangyo Co., Ltd., N-600) was mixed with a tanning machine to obtain the photocatalyst of the present invention (sample D).

The presence of this sample D, α-iron oxyhydroxide was confirmed by analysis by Metz Fuller's Spectrophotometry. Further, Sample D contained sodium of α-iron oxyhydroxide in an amount of 0.75% by weight and 1.19% by weight of Na ₂ O in terms of Fe.

[Example 5]

The suspension of the spindle-shaped titanium oxide used in Example 1 and a suspension of α-iron hydroxide (N-600 manufactured by Ishihara Sangyo Co., Ltd.) were placed in a container equipped with a stirrer, mixed, and then filtered and washed. The film was dried at 110 ° C for 1 day and 1 night, and then pulverized by a cabinet machine to obtain a photocatalyst of the present invention (sample E).

This sample E was confirmed by Metzbauer spectroscopy to confirm the presence of α-iron oxyhydroxide. Further, Sample E contained sodium of α-iron hydroxide in a proportion of 0.75% by weight and 1.19% by weight of Na ₂ O in terms of Fe.

[Comparative Example 1]

The spindle-shaped titanium oxide of Example 1 was used as a comparative sample (sample F).

[Comparative Example 2]

The fired spindle-shaped titanium oxide of Example 2 was used as a comparative sample (sample G).

[Comparative Example 3]

The spherical titanium oxide of Example 3 was used as a comparative sample (sample H).

[Comparative Example 4]

A photocatalyst (Sample I) was obtained in the same manner as in Example 2 except that the heat treatment was carried out without adding ferric nitrate. In sample I, the supported iron hydroxide was confirmed by analysis by Mesper's spectrometry.

[Comparative Example 5]

The sample B obtained in Example 2 was heated in air at a temperature of 350 ° C for 1 hour to obtain a photocatalyst (sample J). In the sample J, the supported iron oxide was confirmed by analysis by the Mesbauer spectroscopy.

[Comparative Example 6]

The α-iron ferric hydroxide (N-600, manufactured by Ishihara Sangyo Co., Ltd.) of Example 4 was used as a comparative sample (sample K).

<Evaluation 1>Evaluation of acetaldehyde decomposition activity

0.1 g of the samples (A to K) obtained in Examples 1 to 5 and Comparative Examples 1 to 6 were uniformly spread on a container of 6 cmφ. The flexible bag having a capacity of 2 L was filled with acetaldehyde and synthetic air, and the acetaldehyde concentration was adjusted to 210 ppm. After the container was placed in a 500 ml separable flask, it was connected to a flexible bag, and the reaction was carried out by circulating a gas in the system at a rate of 31 / minute by a pump. Arrival adsorption After the equilibration (about 30 minutes), light irradiation was performed for 5 hours with a white fluorescent lamp of 5,700 lux. The gas in the system was taken from the sampling port by a syringe, and the acetaldehyde concentration was measured by a gas chromatograph. The reduction rate constant (K) of the acetaldehyde concentration was calculated by the following formula 1, and the photocatalytic activity was evaluated. When the decomposition rate constant of the acetaldehyde is large, the photocatalytic activity is excellent. The results are shown in Table 1. The photocatalyst obtained by the present invention has high photocatalytic activity under the irradiation of light of a white fluorescent lamp by containing titanium oxide and iron oxyhydroxide. Moreover, the photocatalyst of the present invention has high photocatalytic activity under ultraviolet irradiation, and can effectively utilize ultraviolet light plus visible light, and has excellent photocatalytic activity.

Equation 1: ln(C/Co)=-kt

k: reaction rate constant (l/h)

t: reaction time (h)

C: acetaldehyde concentration after light irradiation (ppm)

Co: acetaldehyde concentration at the beginning of light irradiation (ppm)

The reflectance spectra of the samples B, I, and J obtained in Example 2 and Comparative Examples 4 and 5 were measured in the wavelength range of 400 to 700 nm, and the reflectance spectrum of the titanium oxide (sample a) used in Example 2 was measured at each wavelength. The reflectance spectra of the samples B, I, and J were subtracted from the reflectance spectra of the titanium oxide (sample a), and the absorption spectra of the iron compounds contained in the samples B, I, and J were determined. The results are shown in Figures 1 to 3. Sample B loaded with α-iron oxyhydroxide had a high absorption peak in the range of 400 to 500 nm. Since the peak is absorbed, the light of the white fluorescent lamp absorbing the iron oxyhydroxide contains light having a wavelength of 400 to 500 nm; by this absorption, the titanium oxide exhibits photocatalytic activity. Therefore, the photocatalyst activity of the white fluorescent lamp is increased by the light of the wavelength of 400 to 500 nm contained in the light of the white fluorescent lamp by the photocatalyst of the present invention.

Using the samples A and B obtained in Examples 1 and 2, colloidal cerium oxide was used in a binder to prepare a coating agent using pure water as a dispersion medium. Further, pure water is used as a dispersant in the dispersant, and a polyacrylate-based polymer is used as a dispersant. These coating agents and aqueous dispersions were dropped in a container of 6 cmφ, uniformly spread, and dried at 110 ° C for 12 hours to obtain a photo-contact medium. Thereafter, the results of the same test as in the evaluation 1 were carried out, and the iron oxyhydroxide having a wavelength of 400 to 500 nm containing light of the white fluorescent lamp was used in combination, and the light was confirmed by the light of the white fluorescent lamp. Improve photocatalytic activity. Further, the photocatalytic activity is also enhanced under ultraviolet irradiation, and it is possible to effectively use ultraviolet light plus visible light to confirm superior photocatalytic activity.

Even the samples A and B obtained in Examples 1 and 2 were formed using clay. ‧ Granulation As a photocatalyst molded body, it is confirmed that the photocatalyst activity can be stably improved by irradiation with light of a white fluorescent lamp by using iron oxyhydroxide which absorbs light having a wavelength of 400 to 500 nm in light of a white fluorescent lamp. Further, the photocatalytic activity can be improved under ultraviolet irradiation, and ultraviolet light and visible light can be effectively utilized, and it is confirmed that the photocatalytic activity is excellent.

[industrial use]

In the photocatalyst of the present invention, by using iron oxyhydroxide which absorbs light having a wavelength of 400 to 500 nm in light such as a white fluorescent lamp, it has excellent photocatalytic activity with respect to light such as a white fluorescent lamp; In the environment of 400 to 800 nm light, it can be used for a wide range of applications such as purification materials, deodorizing materials, antifouling materials, sterilizing materials, and anti-cloud materials.

Fig. 1 is a differential absorption spectrum of Sample B of Example 2.

2 is a differential absorption spectrum of Sample I of Comparative Example 4.

3 is a differential absorption spectrum of a sample J of Comparative Example 5.

Claims (8)

A photocatalyst comprising a photocatalyst containing at least α-oxyhydroxide iron and rutile-type spindle-shaped titanium oxide; characterized in that α-oxygen is supported on the surface of the rutile-type spindle-shaped titanium oxide particles The iron hydroxide, rutile-type spindle-shaped titanium oxide and/or α-iron hydroxide hydroxide have an alkali metal element and/or an alkaline earth metal element in the interior and/or surface thereof, and the content of α-oxygen hydroxide is relatively The total amount of the α-oxygen hydroxide and the rutile-type spindle-shaped titanium oxide is in the range of 0.01 to 5% by weight in terms of Fe, and the content of the alkali metal element and/or the alkaline earth metal element is relative to the α-oxygen. The total amount of iron hydroxide and rutile-type spindle-shaped titanium oxide is 0.01 to 30% by weight in terms of oxide, and the rutile type is obtained by absorbing a wavelength of 400 to 500 nm by α-iron hydroxide. The spindle-shaped titanium oxide exhibits photocatalytic activity, and the acetaldehyde decomposition reaction rate constant when the photocatalyst is irradiated with light of a white fluorescent lamp having a wavelength of 400 to 500 nm, and the acetaldehyde of the titanium oxide measured under the same conditions Decomposition rate constant, 2 times . For example, in the photocatalyst of claim 1, wherein the alkali metal element is sodium. A method for producing a photocatalyst, which is characterized in that a pH of a vehicle containing a rutile-type spindle-shaped titanium oxide containing an alkali metal element and/or an alkaline earth metal element is adjusted to 3 or less, and then iron is added to the vehicle liquid. Compound, Thereafter, the vehicle liquid is heated in the range of 50 ° C to 200 ° C to react the iron compound, and α-iron oxyhydroxide is supported on the surface of the rutile-type spindle-shaped titanium oxide particles. A method for producing a photocatalyst according to claim 3, wherein a titanium oxide obtained by firing a titanium oxide or a titanium oxide precursor is used. A photocatalyst coating agent comprising at least a photocatalyst and a binder as claimed in claim 1 or 2. A photocatalyst dispersion characterized by containing at least a photocatalyst and a dispersion medium according to claim 1 or 2. A photocatalyst molded body characterized by containing at least a photocatalyst according to claim 1 or 2. A photo-contacting medium characterized in that a photocatalyst according to claim 1 or 2 is fixed to a substrate.