JP2009256111A - Method for producing photosemiconductor particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method by which, when photosemiconductor particles each consisting of a base made of a metal compound photosemiconductor and a ceramic fixed on at least part of the surface thereof is produced by a liquid phase method, solid-liquid separation is easily carried out and the effect of the resulting photosemiconductor particles as a photosemiconductor is not affected. <P>SOLUTION: A mixed fluid, containing the base with the ceramic or a precursor thereof fixed on at least part of the surface thereof and water, is prepared, and a coagulant is added to the mixed fluid and stirred to coagulate solid matter in the form of coarse particles. The solid matter in the form of coarse particles is recovered by solid-liquid separation treatment, and the resulting solid matter is heated to decompose the coagulant contained in the solid matter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a substrate that is a metal compound optical semiconductor, and a method for producing optical semiconductor particles comprising ceramics immobilized on at least a part of the surface of the substrate.

  Metal compound optical semiconductors such as titania and zinc oxide exhibit the property of absorbing light having energy corresponding to its bandwidth. Therefore, application development as an ultraviolet shielding agent is attempted in the fields of cosmetics and resin pigments. Also, paying attention to the high reactivity of holes and electrons generated in metal compound optical semiconductors that have absorbed light, it can be applied to environmental purification such as water purification, antifouling, antibacterial, deodorizing, air purification, etc. as "photocatalyst" Has been tried.

  When a metal compound optical semiconductor is used for these applications, the metal compound optical semiconductor may be used as it is, but a different compound may be immobilized on the surface of the metal compound optical semiconductor for improvement. For example, metal oxide particles whose surface is coated with dense silica (see Patent Document 1), pigment whose surface is coated with a silicon compound and an aluminum compound (see Patent Document 2), silica hydrate coating layer Titanium oxide photocatalyst for removing basic gas (see Patent Document 3), highly active photocatalyst coated with a silicon oxide film having substantially no pores (see Patent Document 4), partially coated with calcium phosphate Photocatalyst (Patent Document 5).

  As a method for immobilizing different compounds on the surface of the metal compound optical semiconductor, a gas phase method (see Patent Document 6) in which a gaseous raw material is reacted with the metal compound optical semiconductor, or a liquid phase method in which treatment is performed in a solvent. is there. Among these, the liquid phase method is excellent in that heat can be easily removed and the amount of a raw material to be reacted is easily controlled. Examples of the liquid phase method include a method in which silicate and sulfuric acid are dropped while heating in a basic aqueous solution (see Patent Document 7), water is adsorbed in advance on the surface of an optical semiconductor in an organic solvent, and a metal alkoxide is added. A method of hydrolyzing on the surface of an optical semiconductor (see Patent Document 8), a production method of coating with silicate in an acidic aqueous medium having a pH of 5 or less (see Patent Document 4), Na, K, Cl, Ca, A method of immersing in a simulated body fluid containing ions such as P and Mg (see Patent Document 5).

It is known to simplify solid-liquid separation using a flocculant, and is industrially used for treatment of waste water and sewage. The effect of the flocculant is to make it easy to separate solids by joining together the fine particles dispersed in the liquid to form coarse particles, so-called flocs.
In the method for producing a metal compound optical semiconductor, examples of simplifying solid-liquid separation using a flocculant include polybasic mineral acids, organic acids or phenols having two or more carboxyl groups and / or hydroxyl groups, and their A method of treating with at least one salt and at least one organic polymer flocculant (see Patent Document 9), a method of aggregating metatitanic acid produced by hydrolysis of titanium sulfate with a polymer flocculant (patent) Reference 10) is disclosed. However, Patent Document 9 and Patent Document 10 relate to the use of a flocculant in a method for producing optical semiconductor particles composed of a substrate which is a metal compound optical semiconductor and ceramics fixed to at least a part of the surface of the substrate. Is not described at all.
Japanese Patent No. 3570730 Japanese Patent No. 1539263 JP 2002-159865 A Patent application PCT / JP2006 / 302542 Japanese Patent No. 3275032 Japanese Patent No. 1895322 Japanese Patent Laid-Open No. 02-296726 Japanese Patent No. 2832342 JP 53-39296 A Japanese Patent No. 3554803

When producing optical semiconductor particles by a liquid phase method, since the handled optical semiconductor particles include fine particles, the following point (a) or (b) becomes a problem, and the optical semiconductor particles are easily recovered from the solvent. I can't.
(A) When collecting the optical semiconductor particles by filtration, the liquid passing speed of the filter is low, and the processing takes time,
(B) When collecting photo semiconductor particles with a thickener, that is, when concentration and separation are performed by sedimentation of photo semiconductor particles, the time required for sedimentation is long and the processing takes time.

  Accordingly, the present invention provides a simple solid-liquid separation when manufacturing optical semiconductor particles comprising a substrate, which is a metal compound optical semiconductor, and ceramics immobilized on at least a part of the surface of the substrate by a liquid phase method. An object of the present invention is to provide a production method that can be used and does not affect the function of the obtained optical semiconductor particles as an optical semiconductor.

In order to solve the above-mentioned problems, the present inventors have intensively studied using a slurry containing titanium oxide particles having a silicic acid compound immobilized on the surface. As a result, when the particles are solid-liquid separated in an agglomerated state by adding an aggregating agent and the resulting solid is heated to decompose the aggregating agent, titanium oxide particles having silicon oxide immobilized on the surface can be easily produced. At the same time, the inventors have found that the obtained product exhibits the same performance as that produced without using a flocculant, and completed the invention. That is, according to the present invention, the following manufacturing method is provided.
[1]
A method for producing optical semiconductor particles comprising a base (hereinafter, appropriately referred to as a base), which is a metal compound optical semiconductor, and ceramics fixed to at least a part of the surface of the base, wherein the ceramic comprises the base and The manufacturing method of the optical-semiconductor particle which is a different compound and consists of the process of following (A)-(D).
(A) a step of mixing the substrate, ceramics or a raw material thereof, and a water-containing solvent to prepare a mixed solution containing the substrate on which ceramic or a precursor thereof is immobilized on at least a part of the surface, and water;
(B) adding a flocculant to the mixed solution and stirring the mixture;
(C) a step of recovering from the water-containing solvent the solid body containing the substrate on which ceramics or a precursor thereof is immobilized on at least a part of the surface, and a flocculant;
(D) A step of decomposing the flocculant by heating the solid matter.
[2]
A step of washing the substrate having ceramics or a precursor thereof immobilized on at least a part of the surface between steps (B) and (C) or between steps (C) and (D) ( The method for producing an optical semiconductor particle according to [1], which also includes E).
[3]
When the step (E) is based on the flow of the water-containing solvent, and the flow rate of the liquid separating the solid and the washing waste liquid is divided into a horizontal vector component and a vertical vector component, The method for producing an optical semiconductor particle according to [2], wherein the cleaning is performed by controlling the supply amount of the hydrous solvent so that the rising speed of the liquid as a vector component in the vertical direction is slower than the sedimentation speed of the solid.

  According to the present invention, solid-liquid separation can be easily performed in the production of optical semiconductor particles composed of a substrate that is a metal compound optical semiconductor and ceramics fixed to at least a part of the surface of the substrate by a liquid phase method. The manufacturing method which can be implemented and does not affect the effect | action as an optical semiconductor of the obtained said optical semiconductor particle can be provided.

The manufacturing method according to the present invention is the following manufacturing method.
[1]
A method for producing optical semiconductor particles comprising a base that is a metal compound optical semiconductor and ceramics immobilized on at least a part of the surface of the base, wherein the ceramics is a compound different from the base, and The manufacturing method of the optical semiconductor particle which consists of the process of (A)-(D) of:
(A) A step of mixing the substrate, ceramics or a raw material thereof, and a water-containing solvent to prepare a mixed solution containing the substrate on which ceramic or a precursor thereof is fixed on at least a part of the surface, and water;
(B) A step of adding a flocculant to the mixed solution and stirring the mixture;
(C) a step of recovering from the water-containing solvent the solid body containing the substrate on which ceramics or a precursor thereof is immobilized on at least a part of the surface, and a flocculant;
(D) A step of decomposing the flocculant by heating the solid matter.
[2]
A step of washing the substrate having ceramics or a precursor thereof immobilized on at least a part of the surface between steps (B) and (C) or between steps (C) and (D) ( The method for producing an optical semiconductor particle according to [1], which also includes E).
[3]
When the step (E) is based on the flow of the water-containing solvent, and the flow rate of the liquid separating the solid and the washing waste liquid is divided into a horizontal vector component and a vertical vector component, The method for producing an optical semiconductor particle according to [2], wherein the cleaning is performed by controlling the supply amount of the hydrous solvent so that the rising speed of the liquid as a vector component in the vertical direction is slower than the sedimentation speed of the solid.

  The photo-semiconductor particles produced in the present invention are composed of a base that is a metal compound photo-semiconductor and ceramics fixed to at least a part of the surface of the base. And the said optical semiconductor particle should just be the said structure each independently, All the particles may be the same structures, and the mixture of the particle | grains of 2 or more types of different structures may be sufficient as them. Further, two or more kinds of ceramics may be fixed on one substrate.

  If a base | substrate is a metal compound optical semiconductor, there will be no restriction | limiting in particular, For example, a titanium oxide, a zinc oxide, a tungsten oxide, strontium titanate etc. are mentioned. A crystallite diameter derived from X-ray diffraction (XRD) is preferably in the range of 1 to 500 nm. The shape is not particularly limited, and examples thereof include a spherical shape, a spheroid shape, a column shape, a geometric shape, and a flake shape. Furthermore, it is also possible to use the above-mentioned substrate having ceramics immobilized on at least a part of its surface as the substrate of the present invention. In addition, although only 1 type is used for this base | substrate, it is also possible to use 2 or more types of mixtures.

  When the present invention is carried out as a method for producing a photocatalyst, titanium oxide is preferable because of its excellent photocatalytic ability and excellent safety and stability. Examples of titanium oxide include amorphous, anatase type, rutile type, brookite type titanium dioxide, and among these, anatase type or rutile type, which are excellent in photocatalytic activity, or a mixture thereof is more preferable. These may contain a small amount of amorphous material. As a substrate, one or more transition metals added or supported on a metal compound optical semiconductor, one or more typical elements of Group 14, 15, and / or Group 16 added or supported on a metal compound semiconductor, An optical semiconductor composed of two or more kinds of metal compounds and a mixture of two or more kinds of metal compound semiconductors can also be used.

  The ceramic is not particularly limited as long as it is a compound different from the base constituting the optical semiconductor particles, and may be a metal compound optical semiconductor. For example, when the substrate is titanium oxide, the ceramic may be zinc oxide. When the present invention is carried out as a method for producing cosmetics, pigments, or photocatalysts, Si, Al, Zr, Ce oxides, or calcium compounds are preferred. The oxide may contain a hydroxyl group, adsorbed water, etc., and may be a single oxide, a binary composite oxide, or a multicomponent composite oxide. And it is not limited to the said metal, You may contain another metal element as an ion or a metal. Examples of calcium compounds include calcium phosphates or silicates, such as hydroxyapatite, fluorapatite, hydroxyapatite containing other metal ions, etc., and calcium phosphates having a mineral composition generally known as “apatite”, and An example is calcium silicate. In the production method of the present invention, in the step (D), heat treatment is performed to decompose the flocculant. Therefore, the ceramic constituting the optical semiconductor particles provided by the production method of the present invention is a fired ceramic.

  Of these oxides or compounds, an oxide of Si is more preferable. This is because when the Si oxide is immobilized on the surface of the substrate, the heat resistance of the substrate is improved and the flocculant can be decomposed at a higher temperature.

  The ceramic raw material is a substance that forms a ceramic or a precursor thereof on the surface of the substrate by causing hydrolysis, condensation, precipitation or the like in the step (A), and may be only one kind. Two or more kinds may be used. Metal halides, metal alkoxides, metal complexes, metal oxoacid salts, and the like are listed as raw materials used only in one kind. A combination of a metal soluble salt and a soluble oxo acid or a salt thereof is used as a raw material using two or more kinds. When the combination is used as a raw material, an insoluble or hardly soluble oxo acid salt of the metal is precipitated on the surface of the substrate to become a ceramic or a precursor thereof. When the ceramic is silicon oxide, silicic acid, silicate, silicate ester, silicon halide, organohydrogenpolysiloxane, etc. can be exemplified as raw materials.

  A ceramic precursor is a compound that is converted into ceramic by physical or chemical treatment. The ceramic precursor may be converted into ceramics in the process of the present invention, or may be provided with a process of converting into ceramics separately. As what is converted into ceramics in the process of this invention, in the heat processing in a process (D), there exists a thing which becomes ceramics by oxidation, hydrolysis, a condensation reaction, etc. Examples of such a precursor include aluminum hydroxide, which is a compound that can be formed on the surface of a substrate using an aluminum alkoxide as a raw material and can be converted into alumina in step (D).

  The water-containing solvent is water or a mixed solvent mainly composed of water, and is an organic solvent classified into alcohols, ketones, ethers, or esters, having 1 to 4 carbon atoms and water-soluble. An organic solvent may be included. Specific examples of the hydrous solvent include water and mixed solvents such as water and methyl alcohol, water and ethyl alcohol, water and isopropanol. Of these, water is preferred. Moreover, these water and mixed solvents can be used individually by 1 type or in combination of 2 or more types.

  There is no restriction | limiting in particular in the mixing method in a process (A). For example, (a) a method of mixing a ceramic or a raw material thereof after mixing the substrate with a hydrous solvent, (b) a mixed solution of mixing the hydrous solvent and the substrate, and a mixed solution of mixing the hydrous solvent and the ceramic or the raw material thereof. (C) A method of mixing a substrate after mixing ceramics or its raw material with a water-containing solvent, (d) pH of a mixed solution containing the substrate, ceramics or its raw material, and a water-containing solvent And (e) in the case where the ceramic is formed by reacting two or more kinds of raw materials, a mixed liquid in which a hydrous solvent, a substrate, and a first ceramic raw material are mixed, and hydrous And a method of mixing two of a mixed solution in which a solvent and a second raw material of ceramics are mixed. The mixed solution thus prepared may be appropriately aged at room temperature or under heating conditions.

  The mixed solution prepared in the step (A) includes a substrate having ceramics or a precursor thereof immobilized on at least a part of the surface, and water. It does not necessarily need to be composed only of these materials. Among the organic solvents classified as unreacted ceramic raw materials, by-products generated during the formation of the ceramic precursor, alcohols, ketones, ethers, or esters, the number of carbon atoms 1 to 4 and a water-soluble organic solvent may be included.

  If the concentration of the substrate contained in the mixed solution is low, the productivity is low, and if the concentration is high, the specific gravity of the solution is excessive, and special manufacturing equipment with strong stirring force is required. So in any case, the economy is bad. Therefore, the concentration of the substrate relative to the total weight of the mixed solution (hereinafter referred to as “slurry concentration” as appropriate) is preferably 0.5% by weight to 40% by weight, and more preferably 5% by weight to 20% by weight. preferable.

  When the concentration of water in the mixed solution is low, the flocculant is difficult to dissolve and the aggregation effect is difficult to express. Therefore, when expressed as the weight of water with respect to the total weight of the mixed solution, 60% by weight or more is preferable, 80% by weight or more is more preferable. The water contained in the mixed solution may be finally within the above range, and only water as a water-containing solvent may be used, and a preparation method that enters the above range upon completion of mixing may be used. After that, it may be adjusted by adding water. In addition, when the mixed solution contains an inorganic salt such as a neutralized salt, the flocculant may not be effective due to the salting out action, so even if the water concentration is within this range, the water-containing solvent May be substituted.

  Hereinafter, specific examples of the mixing method in the step (A) will be shown.

(1. Method of mixing while maintaining the pH of a mixed solution containing a substrate, ceramics or a raw material thereof, and a water-containing solvent at 5 or less)
Step (A) mixes at least one set of the hydrous solvent containing the substrate and the silicate, the hydrous solvent containing the silicate and the substrate, and the hydrous solvent containing the substrate and the hydrous solvent containing silicate. A manufacturing method, which is a step and is a step of mixing while maintaining a pH of a mixed solution containing both the substrate and the silicate at 5 or less.

  In this example, the ceramic is silicon oxide. Here, as a method for maintaining the pH at 5 or less, when mixing the substrate, the silicate, and the water-containing solvent, the pH of the water-containing solvent is always measured, and an appropriate method may be added by adding an acid and a base. . However, it is easy to neutralize the total amount of the base components contained in the silicate used for the production and to make a sufficient amount of acid present in the water-containing solvent in advance so that the pH becomes 5 or less. In this case, as the silicate, silicic acid and / or an oligomer salt thereof may be used, and two or more kinds may be mixed and used. Sodium salts and potassium salts are preferred from the viewpoint of industrial availability, and an aqueous sodium silicate solution (JIS K1408 “water glass”) is more preferred because the dissolution step can be omitted. As the acid, any acid can be used, but a mineral acid such as hydrochloric acid, nitric acid, or sulfuric acid is preferably used. Only one kind of acid may be used, or two or more kinds of acids may be mixed and used. A base is used separately in the case of the above-described method in which a sufficient amount of acid is previously present in a water-containing solvent after neutralizing the total amount of base components contained in the silicate and then having a pH of 5 or less. There is no need. However, when a base is used, any base can be used. Of these, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide are preferably used.

(2. Method of mixing the substrate after mixing the ceramic or its raw material with the hydrous solvent)
A production method, wherein the step (A) is a step of forming a calcium and phosphorus compound on the surface of the substrate using a simulated body fluid. Specifically, the simulated body fluid is first prepared and then the substrate is mixed. In this example, apatite is formed as a kind of calcium phosphate.

  Here, the simulated body fluid is prepared by dissolving sodium chloride, potassium chloride, sodium bicarbonate, dipotassium hydrogen phosphate, magnesium chloride, calcium chloride, sodium sulfate, or sodium fluoride in water. It means a solution whose pH is adjusted to 7 to 8 with an acid base such as hydrochloric acid or amine. Among the simulated body fluid compositions in which a sodium ion concentration of 147 mM, a potassium ion concentration of 5 mM, a calcium ion concentration of 7.5 mM, a bicarbonate ion of 4.2 mM, and a hydrogen phosphate ion of 4.2 mM and an aqueous solution of pH 7.4 are preferred It can be illustrated as one.

  The flocculant added in the step (B) is a water-soluble flocculant. Of the water-soluble flocculants, polymer flocculants are preferred. Examples thereof include polymers such as acrylamide, acrylic acid, and methacrylic acid, and those obtained by modifying at least a part of functional groups of these polymers. As long as it is a polymer flocculant, any of anionic, nonionic, cationic or amphoteric types can be used, and any type of polymer flocculant can be selected depending on the pH of the mixed solution to be added. Since the polymer flocculant other than the nonionic type contains a partial structure of an ion pair, an inorganic salt may remain when the flocculant is decomposed in the step (D), and further washing may be required. Examples of the ion pair include sodium salt, potassium salt, chloride, sulfate and the like. From this point, a nonionic polymer flocculant is preferable, but as is apparent from the amount of the flocculant used for the optical semiconductor particles, the amount of residual inorganic salt is not so large, and other types than the nonionic type can be used. is there. Examples of nonionic polymer flocculants include polyacrylamide flocculants containing one or more compounds selected from the group consisting of acrylamide or modified products thereof as repeating units. The form of the flocculant is not particularly limited, and any of powder, dispersion, paste, emulsion, or solution can be used. The addition method is not particularly limited, and any known addition method may be used.

  The amount of the flocculant used is preferably 0.1% by weight or more and 3% by weight or less, and more preferably 0.5% by weight or more and 1.5% by weight or less with respect to the weight of the substrate contained in the mixed solution. . If the amount is too small, it is difficult to obtain an agglomeration effect. If the amount is too large, the effect of simplifying solid-liquid separation can be used, but it takes time to decompose in the step (D) and the productivity is lowered.

  The solid material recovered from the mixed solution in the step (C) includes the substrate on which ceramics or a precursor thereof is immobilized on at least a part of the surface, and a flocculant. When recovered, it is not necessary to be composed only of these, and it may contain a water-containing solvent or a neutralized salt. Moreover, the collection method of the said solid substance is not specifically limited. A known method for separating a solid and a liquid, such as natural filtration by the weight of the water-containing solvent, vacuum filtration, pressure filtration, centrifugation, and decantation, can be applied.

  In order to decompose the flocculant in the step (D), the solid is heated to a temperature range where the flocculant is decomposed. At a low temperature, the flocculant tends to be insufficiently decomposed, and it takes a long time for the decomposition. When the temperature is high, the flocculant is rapidly decomposed, but the optical semiconductor particles are easily deteriorated by heating. Therefore, 400 ° C. or higher and 1000 ° C. or lower is preferable, and 500 ° C. or higher and 800 ° C. or lower is more preferable. The heating time needs to be selected depending on the heating temperature, and is not particularly limited. However, a long time is required for the low temperature treatment, and a short time is sufficient for the high temperature treatment. In the case of heating at 600 ° C., it is preferably 0.5 hours or longer and 24 hours or shorter, more preferably 1 hour or longer and 18 hours or shorter. Moreover, when decomposition | disassembly of an aggregating agent is based on an oxidative decomposition reaction, decomposition | disassembly can also be accelerated | stimulated by raising the oxygen partial pressure in atmosphere.

  When the step (A) is a method of using or using a nonvolatile compound as a by-product, the nonvolatile compound may be incorporated into the optical semiconductor particles as an impurity. In this case, it is necessary to clean the optical semiconductor particles. In order to produce the non-volatile compound as a by-product, for example, base particles are dispersed in a nitric acid acidic aqueous solution, mixed with sodium silicate, and a silicon compound is immobilized on the surface of the base. There is a method for preparing a mixed solution containing, and sodium nitrate produced as a neutralized salt corresponds to the nonvolatile compound. In the method using the non-volatile compound, the base material is mixed with a solution in which calcium chloride and phosphate are dissolved as a raw material for ceramics, and the base is fixed with the calcium and phosphorus compound. There is a method of preparing a mixed solution containing particles, and the remaining amount of calcium chloride or phosphate used corresponds to the nonvolatile compound.

In addition, when the step (A) is a method using sulfuric acid, a method using or by-producing sulfate, or a method using a substrate, ceramics, or a raw material of ceramics containing a sulfur compound, Sulfur compounds such as SO ₄ minutes and SO ₃ minutes may be incorporated into the semiconductor particles and colored. In order to suppress or avoid this coloring, the content of the sulfur compound is 0.5 wt% or less, preferably 0.3 wt% as the weight of S atoms with respect to the weight of the metal compound photo semiconductor contained in the photo semiconductor particles. In some cases, it may be necessary to perform cleaning in order to achieve a weight% or less, more preferably 0.2 wt% or less.

  When cleaning is required, when preparing a mixed solution in step (A), a method of removing impurities from the mixed solution using an ion exchange resin, or when recovering a solid in step (C) In addition, washing may be performed by a method of passing a water-containing solvent through a cake made of solid matter formed on a filter, or at least one of the surfaces independently of steps (A) to (D). It can also be carried out as a production method including a step (E) of cleaning the substrate having ceramics or its precursor immobilized on the part. The step (E) may be performed at any stage after the step (A), either between the steps (B) and (C) or between the steps (C) and (D). If it is, it is preferable because the solid and the solvent used for washing (hereinafter referred to as “washing solvent” as appropriate) can be easily separated and washed easily. Although it is possible to carry out after the step (D), a step for recovering the solid matter from the washing solvent and a step for drying the solid matter are necessary.

  The cleaning solvent is a water-containing solvent mainly composed of water, and includes an organic solvent having 1 to 4 carbon atoms and a water-soluble organic solvent classified into alcohols, ketones, ethers, or esters. It doesn't matter. When the step (A) is a step of by-producing water-soluble impurities such as inorganic salts, the solvent used for washing is preferably water.

  Further, the washing solvent may be adjusted to be acidic or basic in order to enhance the removal efficiency of impurities. For example, if it is adjusted to be acidic with mineral acid or organic acid, the removal efficiency of cationic impurities such as alkali metal and alkaline earth metal can be enhanced, and if it is adjusted to basic with alkali metal hydroxide or ammonia In addition, the removal efficiency of anionic impurities such as nitrate ion, chloride ion and sulfate ion can be enhanced. In addition, only one of the acid basicity of the washing solvent may be carried out, or acidity and basicity may be used in combination. Even if it is swung between acidic and basic, it may be washed. The pH of the cleaning solvent adjusted to be acidic or basic may be adjusted to any pH as long as the flocculant does not decompose and exhibits a coagulation effect. When a nonionic polyacrylamide polymer flocculant is used, the pH is preferably in the range of 1 to 10, more preferably pH 2 to 8.

  The washing method is a known washing method, such as a method of alternately repeating decantation and the addition of the washing solvent one or more times, a desalting treatment by ion exchange, a washing method of repeating redispersion and filtration in the washing solvent one or more times. However, it is preferable to carry out flow cleaning in which the solvent is continuously replaced successively, and more preferably by upward flow. This is because the solid matter (hereinafter, referred to as “floc” where appropriate) in which coarse particles are formed by the effect of the flocculant exhibits a large sedimentation rate. Examples of such a device include a device in which a liquid mixture containing optical semiconductor particles and impurities is placed in a cylindrical container, water is supplied from the bottom of the container, and discharged from the top. Known devices such as thickeners and screw decanters Is also available.

  When performing the cleaning by the upward flow, when the liquid flow velocity in the portion separating the floc and the cleaning solvent is divided into a horizontal vector component and a vertical vector component, the liquid vertical vector Washing is performed by controlling the supply amount of the washing solvent so that the rising speed as a component is equal to or less than the sedimentation speed of the floc. If the rising speed exceeds the settling speed of the floc, the floc flows out of the cleaning device and cannot be cleaned. Although it is possible to reduce the ascending speed to 0, that is, to wash the laminar flow with the washing solvent only in the horizontal direction, the apparatus becomes complicated. Therefore, the ascending speed needs to be greater than 0 and less than or equal to the floc settling speed.

When the washing solvent is supplied from the lower part of the floc precipitation, the precipitation layer becomes resistant to the washing solvent, so that the rising flow rate varies and a local upflow may occur. In addition, bubbles generated in equipment piping or a liquid feed pump are supplied to the cleaning container, and the flock may rise in the cleaning container accompanying the bubbles. For this reason, if the rising flow velocity approximates the sedimentation rate of the floc, cleaning can be performed in a short time, but the loss of the solid matter increases.
On the other hand, if the ascending flow rate is too small, loss of the floc can be suppressed, but it takes time for cleaning. Therefore, the ascending flow rate is preferably 1% or more and 50% or less, more preferably 3% or more and 25% or less, based on the settling speed of the floc (100%).

Examples of the photocatalyst in which the Si oxide produced in the present invention is immobilized on the surface include the following.
(A) a photocatalyst comprising the substrate and a silicon oxide film having substantially no pores covering the substrate;
(B) The photocatalyst of (a) which is a film obtained by baking the silicon oxide film (c) The silicon oxide film is a fired film obtained by firing at a temperature of 400 ° C. or higher and 1000 ° C. or lower. The photocatalyst according to the b (d) The photocatalyst according to the a to c, wherein the alkali metal content is 1 ppm or more and 1000 ppm or less,
(E) In the pore diameter distribution measurement in the region of 20 to 500 angstroms by the nitrogen adsorption method, the photocatalysts a to d having no pores derived from a silicon oxide film,
(F) The photocatalyst of a to e, wherein the amount of silicon supported per 1 m ^{2 of} surface area is 0.10 mg or more and 2.0 mg or less,
(G) The photocatalysts a to f, wherein an alkali metal is contained in silicon oxide,
(H) The photocatalysts a to g, wherein the sulfur compound content is 0.5% by weight or less as a sulfur atom with respect to the weight of the photocatalyst.
The photocatalysts (a) to (h) will be described in more detail below.
Examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium, and francium. These alkali metals may contain only 1 type and may contain 2 or more types.
The alkali metal content is more preferably 10 ppm to 1000 ppm, and 10 ppm to 500 ppm is particularly preferable because of excellent heat resistance. When an alkali metal is contained, a desired silicon oxide film with improved photocatalytic activity is formed. However, when it increases, the heat resistance of the photocatalyst deteriorates.
The amount of silicon supported is a calculated value calculated from the amount of silicon contained in the photocatalyst having a Si oxide immobilized on the surface and the surface area, preferably 0.12 mg or more, 1.5 mg or less, more preferably 0.8. It is 16 mg or more and 1.0 mg or less. If it is less than 0.10 mg, the effect of improving the activity by the silicon oxide film is not sufficient, and the effect of improving the photolytic activity is small. On the other hand, if it exceeds 2.0 mg, the ratio of the substrate in the photocatalyst is too low, so that the photolytic activity is hardly improved.
When the sulfur compound is contained, the photocatalyst may be colored, and is preferably 0.5% by weight or less, more preferably 0.3% by weight or less, and most preferably not contained.

In the present invention, the presence or absence of pores derived from a silicon oxide film is compared with the pore volume distribution of the photo-semiconductor particles in which the ceramic is silicon oxide and the pore volume distribution of particles corresponding to the substrate of the photo-semiconductor particles. In particular, it can be determined by the following methods (1) to (4).
(1) Measure the nitrogen adsorption isotherm during the substrate desorption process,
(2) Measuring nitrogen adsorption isotherm in the process of desorption of optical semiconductor particles (3) Analyzing the two nitrogen adsorption isotherms by the BJH (Barrett-Joyner-Halenda) method to obtain a region of 20 to 500 angstroms The log differential pore volume distribution curve is obtained.
(4) When two log differential pore volume distribution curves are compared, and there is no region where the log differential pore volume of the optical semiconductor particles is 0.1 ml / g or more larger than the log differential pore volume of the substrate When it is determined that the optical semiconductor particles have substantially no pores and a region larger than 0.1 ml / g exists, it is determined that the silicon oxide film has pores.
The reason why the concentration is 0.1 ml / g or more is that, in the pore distribution measurement by the nitrogen adsorption method, a measurement error of about 0.1 ml / g width often occurs in the log differential pore volume value.

Examples of the photocatalyst in which the calcium compound produced in the present invention is immobilized on the surface include the following. Here, the substrate is described as “titanium oxide particles” having excellent photocatalytic activity.
(X) Titanium oxide particles in which calcium phosphate is immobilized on at least part of the surface (y) Titanium oxide particles in which apatite composed of calcium phosphate is immobilized on at least part of the surface ( z) Titanium oxide particles in which calcium silicate is immobilized on at least a part of the surface The photocatalysts (x) to (z) have an adsorption performance because the calcium compound exhibits an effect as an adsorbent or a spacer. It is characterized in that the organic base material (base material made of an organic substance such as a resin) is hardly deteriorated. Here, “deterioration of the organic base material” means that when the photocatalyst is added to the organic base material, the organic base material is decomposed and deteriorated by the decomposing power of the photocatalyst. The spacer effect of the calcium compound in the photocatalysts (x) to (z) is due to the structure in which the titanium oxide particles do not directly contact the organic base material. It is difficult to be disassembled.

The amount of the calcium compound is preferably 0.5% by weight or more and 20% by weight or less, and more preferably 3% by weight or more and 10% by weight or less as the weight of Ca ions relative to the total weight of the photocatalyst. When the amount of the calcium compound is small, the effect as an adsorbent or a spacer is limited. When the amount is large, the organic matter is more difficult to deteriorate, but the ratio of the substrate to the total weight of the photocatalyst is lowered, so that the photocatalytic activity is lowered.
The calcium compound may be of a single composition, but may be a mixture or composite of two or more compounds. For example, when calcium phosphate is immobilized, calcium carbonate generated based on carbon dioxide in the air may be immobilized together, and other inorganic ions may be included.

  Since the optical semiconductor particles obtained in the present invention have no difference in performance as compared with those produced without using an aggregating agent, there is no particular limitation when used for various applications. For example, it can be blended as a UV shielding agent or a pigment in applications such as cosmetics, sunscreen creams, synthetic resins, paints, etc., as well as known ones. Moreover, it can be used for the photocatalyst containing body which shows functions, such as air purification, water quality purification, deodorization, antibacterial, antifouling, self-cleaning, as a photocatalyst.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the following, a solid material containing the above-mentioned substrate having a ceramic or its precursor immobilized on at least a part of its surface and a flocculant prepared through a step corresponding to step (B) of the present invention, and a hydrous solvent The slurry consisting of is called “coarse particle liquid”. In Examples 1 to 7 and Comparative Examples 1 to 4, when the alkali metal content of the optical semiconductor particles is not described, it means that the alkali metal cannot be detected.

First, analysis methods used in Examples and Comparative Examples will be described.
(i) Alkali metal content The alkali metal content was measured using a fluorescent X-ray analyzer (LAB CENTER XRE-1700, Shimadzu Corporation), and the atomic absorption photometer (Z- 5000, Hitachi, Ltd.).
(ii) Silicon content The silicon content was quantified using a fluorescent X-ray analyzer (LAB CENTER XRE-1700, Shimadzu Corporation).
(iii) Specific surface area The BET method specific surface area measuring device (FlowSorb 2 2300, Shimadzu Corporation) was used.
(iv) Crystallite diameter X-ray diffraction (XRD) measurement was performed and calculated using the Scherrer equation.

Example 1
(1-A; Preparation of liquid mixture 1)
200 g of water and 81.7 g of 1 mol / L nitric acid aqueous solution are added to a glass flask, and titanium dioxide (ST-01, Ishihara Sangyo Co., Ltd., water content 9% by weight, specific surface area 300 m ² / g, crystallite diameter 6 nm, containing Na (Amount 1400 ppm) 24.5 g was dispersed to prepare A liquid. In a beaker, 100 g of water and 13.5 g of an aqueous sodium silicate solution (SiO ₂ content 29.1 wt%, Na ₂ O content 9.5 wt%, JIS K1408 “Water Glass No. 3”) were added, stirred, and solution B It was. The liquid B was dripped at 2 ml / min while the liquid A was kept at 35 ° C. and stirred to obtain a mixed liquid C. The pH of the mixed solution C at the end of dropping was 2.8. The mixture C was stirred for 16 hours while being kept at 35 ° C. to obtain a mixture 1. In addition, the slurry density | concentration of the liquid mixture 1 is 5.3 weight%.
(1-B; Preparation of coarse particle liquid 1)
While stirring at room temperature, 26 mg of a commercially available polymer flocculant Acofloc (registered trademark of Mitsui Chemicals Aqua Polymer Co., Ltd., manufactured by Mitsui Chemicals Aqua Polymer Co., Ltd., nonionic, modified acrylamide polymer) is powdered with respect to the total amount of the liquid mixture 1. As it was, it was thrown in three times. The amount of the polymer flocculant used corresponds to 0.1% by weight. When stirring was continued, coarse particles were gradually formed, and the coarse particle liquid 1 was obtained by stirring for 15 minutes after completion of the addition of the polymer flocculant. In the coarse particle liquid 1, after stirring was stopped and left for 30 minutes, a white floc settled on the bottom of the flask, and the supernatant liquid was slightly cloudy.
(Preparation of optical semiconductor particles 1)
Solids were recovered from the total amount of the coarse particle liquid 1 by vacuum filtration, and washed by repeating redispersion in 500 mL of pure water and vacuum filtration four times alternately. Next, the washed solid was put in a magnetic dish and heated at 120 ° C. for 3 hours in an air atmosphere using an electric furnace. The temperature was continuously raised to 600 ° C., and then kept at 600 ° C. for 3 hours. After heating, the mixture was allowed to stand until it reached room temperature to obtain 23.4 g of optical semiconductor particles 1. This optical semiconductor particle 1 was a white powder, the silicon content was 5.7 wt%, and the specific surface area was 187.1 m ² / g. Therefore, the amount of silicon supported per 1 m ² of the surface area of the optical semiconductor particle 1 was 0.31 mg. Moreover, the optical semiconductor particle 1 had a sodium content of 160 ppm.

(Example 2)
(2-A; Preparation of mixed solution 2)
A liquid mixture 2 was obtained in the same manner as Example 1 (1-A).
(2-B: Preparation of coarse particle liquid 2)
In the same manner as in Example 1 (1-B), except that the mixed solution 2 was used instead of the mixed solution 1 and 130 mg of the commercially available flocculant N210 was used, and it was added in 12 batches. A coarse particle liquid 2 was obtained. In the coarse particle liquid 2, after stirring was stopped and the mixture was allowed to stand for 30 minutes, a white floc settled on the bottom of the flask, and the supernatant liquid was transparent. The amount of the polymer flocculant used corresponds to 0.6% by weight.
(2-C; Preparation of optical semiconductor particles 2)
The total amount of the coarse particle liquid 2 was transferred to a glass 500 mL beaker and allowed to stand for 30 minutes, and then the supernatant liquid was decanted off. Next, the following (a) to (d) were repeated 5 times for washing.
(A) 330 mL of pure water was poured into a beaker.
(B) Stir with a glass rod for 1 minute,
(C) left for 30 minutes,
(D) The supernatant was decanted off.
Then, the contents of the beaker were filtered under reduced pressure to recover the solid matter. The collected white solid was put in a magnetic dish and heated at 120 ° C. for 3 hours in an air atmosphere using an electric furnace. The temperature was continuously raised to 600 ° C., and then kept at 600 ° C. for 3 hours. After heating, the mixture was allowed to stand until it reached room temperature to obtain 24.1 g of optical semiconductor particles 2. The optical semiconductor particles 2, a white powder, silicon content 5.7 wt%, a specific surface area of 195.9m ² / g, a surface area 1 m ² per silicon supported amount 0.29 mg, was sodium content 150 ppm.

(Example 3)
(3-A; Preparation of liquid mixture 3)
To a glass separable flask having a volume of 1.5 L, 555 g of water and 22.7 g of 60% nitric acid are added, and titanium dioxide (ST-01, Ishihara Sangyo Co., Ltd., water content 9% by weight, specific surface area 300 m ² / g, crystal 122.0 g (child diameter 6 nm, Na content 1400 ppm) was dispersed to prepare Liquid A. In a beaker, 232.4 g of water and 67.6 g of an aqueous sodium silicate solution (SiO ₂ content 29% by weight, Na ₂ O content 9.5% by weight, JIS K1408 “Water Glass No. 3”) were added, stirred, and liquid B It was. The liquid B was dripped at 3 ml / min while the liquid A was maintained at 35 ° C. and stirred, whereby a liquid mixture C was obtained. The pH of the mixed solution C at the end of dropping was 3.9. The mixture C was stirred for 16 hours while maintaining the temperature at 35 ° C. to obtain a mixture 3. The slurry concentration of the mixed solution 3 is 11.1% by weight.
(3-B: Preparation of coarse particle liquid 3)
Example 1 (1-B) except that 1/3 of the mixture 3 was used in place of the mixture 1 and that 218 mg of the commercially available flocculant N210 was used and was added in 23 portions. ) To obtain a coarse particle liquid 3. In the coarse particle liquid 3, after stirring was stopped and the mixture was allowed to stand for 30 minutes, white floc settled on the bottom of the flask, and the supernatant liquid was transparent. The amount of the polymer flocculant used corresponds to 0.6% by weight. Further, when the floc settled after stopping the stirring, the length of the boundary between the sludge and the supernatant liquid descending in one minute was measured to determine the floc sedimentation speed. As a result, the sedimentation speed of floc was 3.7 cm / min.
(3-C; Preparation of optical semiconductor particles 3)
The coarse particle liquid 3 was transferred to a glass 500 mL beaker and allowed to stand for 30 minutes, and then the supernatant liquid was decanted off. Next, a glass column tube (inner diameter: 90 mm, length: 300 mm, lower end: attached to a two-way cock, upper end: a glass tube with an inner diameter of 4 mm can be held at an arbitrary height, and a stopper that can be sealed except in the glass tube is attached) With the bottom fixed and the bottom cock closed, the top stopper was opened and the contents of the beaker were transferred into the column. Then, after closing the stopper at the upper end and opening the cock at the lower end, pure water was supplied from the lower end at a rate of 10 mL / min for 5 hours to drain the drainage through the glass tube at the upper end. At that time, the height of the glass tube was adjusted so that the liquid amount inside the column tube was 400 mL. In addition, the ascending flow rate of the liquid in the column tube calculated from the supply rate of pure water and the inner diameter of the column tube is 0.16 cm / min, which corresponds to 4% of the floc sedimentation rate. After 5 hours, the supply of pure water was stopped, and the contents of the column tube were filtered under reduced pressure to recover the solid matter. The recovered white solid was placed in a magnetic dish and heated in an air atmosphere at 120 ° C. for 3 hours using an electric furnace. The temperature was continuously raised to 600 ° C., and then kept at 600 ° C. for 3 hours. After heating, the mixture was allowed to stand until it reached room temperature to obtain 42.5 g of optical semiconductor particles 3. The optical semiconductor particles 3 is a white powder, silicon content 6.1 wt%, a specific surface area of 209.8m ² / g, a surface area 1 m ² per silicon supported amount 0.29 mg, sodium content was 170ppm .

Example 4
(4-A; Preparation of mixture 4)
One-third of the amount of the mixed solution 3 was separated to obtain a mixed solution 4.
(4-B; Preparation of coarse particle liquid 4)
Coarse particles are obtained in the same manner as in Example 1 (1-B) except that the mixed liquid 4 is used instead of the mixed liquid 1 and that 435 mg of the polymer flocculant N210 is added in 36 portions. Liquid 4 was obtained. The amount of the polymer flocculant used corresponds to 1.2% by weight.
(4-C; Preparation of optical semiconductor particles 4)
Except for using coarse particle liquid 4 instead of coarse particle liquid 3 and maintaining 600 ° C. for 5 hours, photo-semiconductor particles 4 were obtained in the same manner as in Example 3 (3-C). 9 g was obtained. This optical semiconductor particle 4 was a white powder, had a silicon content of 6.4% by weight, a specific surface area of 212.3 m ² / g, a silicon loading amount of 0.30 mg per 1 m ^{2 of} surface area, and a sodium content of 200 ppm. It was.

(Example 5)
(5-A; Preparation of mixed solution 5)
210 g of water and 2.8 g of 60% nitric acid are added to a glass flask, and titanium dioxide (ST-01, Ishihara Sangyo Co., Ltd., water content 9% by weight, specific surface area 300 m ² / g, crystallite diameter 6 nm, Na content 1400 ppm) 20.4g was disperse | distributed and it was set as A liquid. 88.2 g of water and 11.7 g of a potassium silicate aqueous solution (manufactured by Wako Pure Chemical Industries, SiO ₂ content 28 wt%) were added to the beaker, and the mixture was stirred to give B solution. The liquid A was kept at 25 ° C. and stirred, and the liquid B was added dropwise at 2 ml / min to obtain a mixed liquid C. The pH of the mixed solution C at the end of dropping was 2.9. The mixture C was stirred for 16 hours while being kept at 25 ° C. to obtain a mixture 5. In addition, the slurry density | concentration of the liquid mixture 5 is 5.6 weight%.
(5-B: Preparation of coarse particle liquid 5)
Coarse particles are obtained in the same manner as in Example 1 (1-B) except that the mixed liquid 5 is used instead of the mixed liquid 1 and 109 mg of the polymer flocculant N210 is added in 10 portions. Liquid 5 was obtained. The amount of the polymer flocculant used corresponds to 0.6% by weight.
(5-C; Preparation of optical semiconductor particles 5)
20.6g of optical semiconductor particles 5 were obtained in the same manner as in Example 2 (2-C) except that the coarse particle liquid 5 was used instead of the coarse particle liquid 2. The optical semiconductor particles 5 is a white powder, silicon content 4.9 wt%, a specific surface area of 193.9m ² / g, a surface area 1 m ² per silicon supported amount 0.25 mg, sodium content 80 ppm, potassium content It was 100 ppm.

(Example 6)
(6-A; Preparation of mixed solution 6)
230 g of water and 25.2 g of 1 mol / L hydrochloric acid aqueous solution were added to a glass flask, and titanium dioxide (P-25, Nippon Aerosil Co., Ltd., anatase: rutile ratio 8: 2 mixture, purity 99.5%, specific surface area) 22.4 g (50 m ² / g, no alkali metal was detected) was dispersed to prepare Liquid A. In a beaker, 100 g of water and an aqueous solution of sodium silicate (SiO ₂ content 29% by weight, Na ₂ O content 9.5% by weight, JIS K1408 “Water Glass No. 3”) were added and stirred to obtain Liquid B. . The liquid B was dripped at 2 ml / min while the liquid A was kept at 35 ° C. and stirred to obtain a mixed liquid C. The pH of the mixed solution C at the end of dropping was 2.9. The mixture C was stirred for 72 hours while being kept at 35 ° C. to obtain a mixture 6. The slurry concentration of the mixed solution 6 is 5.3% by weight.
(6-B: Preparation of coarse particle liquid 6)
115 mg of Mixture 6 was used instead of Mixture 1 and Acofloc (Mitsui Chemicals Aqua Polymer registered trademark) N100S (Mitsui Chemicals Aqua Polymer Co., Ltd., nonion type, polyacrylamide) was used instead of the commercially available polymer flocculant N210. The coarse particle liquid 6 was obtained in the same manner as in Example 1 (1-B) except that it was used 10 times differently. After the coarse particle liquid 6 was agitated and left for 30 minutes, white floc settled on the bottom of the flask, and the supernatant liquid was transparent. In addition, the usage-amount of a polymer flocculent is equivalent to 0.5 weight%.
(6-C; Preparation of optical semiconductor particles 6)
22.5g of optical semiconductor particles 6 were obtained in the same manner as in Example 2 (2-C) except that the coarse particle liquid 6 was used instead of the coarse particle liquid 2. The optical semiconductor particles 6, a white powder, silicon content 1.3 wt%, a specific surface area of 52.9m ² / g, silicon supported amount per surface area of 1 m ² is 0.25 mg, sodium content 40ppm met It was.

(Example 7)
(7-A; Preparation of mixed solution 7)
A liquid mixture 7 was obtained in the same manner as in Example 6 (6-A).
(7-B; Preparation of coarse particle liquid 7)
In the same manner as in Example 7 (7-B), coarse particle liquid 7 was obtained. In the coarse particle liquid 7, after stirring was stopped and the mixture was allowed to stand for 30 minutes, white floc settled on the bottom of the flask, and the supernatant liquid was transparent. In addition, the usage-amount of a polymer flocculent is equivalent to 0.5 weight%.
(7-C; Preparation of optical semiconductor particles 7)
The coarse particle liquid 7 was filtered under reduced pressure to recover a solid. The collected white solid was put in a magnetic dish and heated at 120 ° C. for 3 hours in an air atmosphere using an electric furnace. The temperature was continuously raised to 600 ° C., and then kept at 600 ° C. for 3 hours. After heating, the mixture was allowed to stand until it reached room temperature to obtain 22.9 g of optical semiconductor particles 7. This optical semiconductor particle 7 was a white powder, having a silicon content of 1.3% by weight, a specific surface area of 54.2 m ² / g, a silicon loading of 0.24 mg per 1 m ^{2 of} surface area, and a sodium content of 820 ppm.

(Example 8)
(8-A; Preparation of mixed solution 8)
Sodium chloride, sodium bicarbonate, potassium chloride, disodium hydrogen phosphate, calcium chloride, hydrochloric acid, and water were used as simulated body fluids, Na ion 147 mM, K ion 5 mM, Ca ion 7.5 mM, bicarbonate ion 4. An aqueous solution having a pH of 7.4 and a composition of 2 mM and hydrogen phosphate ion of 5 mM was prepared. Then, 11.0 g of titanium dioxide (ST-01, Ishihara Sangyo Co., Ltd., water content 9 wt%, specific surface area 300 m ² / g, crystallite diameter 6 nm) is added to 2000 g of the simulated body fluid, and the mixture is stirred at 50 ° C. for 8 hours. I kept doing it. The slurry concentration at this stage is 0.5% by weight. Next, heating and stirring were stopped and the mixture was allowed to stand at room temperature for 18 hours. As a result, a white precipitate was formed at the bottom, and the supernatant was slightly cloudy. After decanting off the supernatant, the precipitate was diluted with pure water to make the total amount 100 g. This was subjected to ultrasonic irradiation and stirring for 1 hour, and the precipitate was redispersed to obtain a mixed solution 8. The slurry concentration of the mixed solution 8 is 10.0% by weight.
(8-B; Preparation of coarse particle liquid 8)
Same as Example 1 (1-B), except that the mixed liquid 8 was used instead of the mixed liquid 1 and that 57 mg of the commercially available polymer flocculant N210 was charged in 5 divided powders. Thus, a coarse particle liquid 8 was obtained. After the coarse particle liquid 8 was agitated and left for 30 minutes, white floc settled on the bottom of the flask, and the supernatant liquid was transparent. The amount of the polymer flocculant used corresponds to 0.6% by weight.
(8-C; Preparation of optical semiconductor particles 8)
The coarse particle liquid 8 was transferred to a glass 200 mL beaker and allowed to stand for 30 minutes, and then the supernatant liquid was decanted off. Next, the following (a) to (d) were repeated 5 times for washing.
(A) Pour 130 mL of pure water into a beaker.
(B) stirred for 5 minutes with a glass rod,
(C) left for 30 minutes,
(D) The supernatant was decanted off.
Then, the contents of the beaker were filtered under reduced pressure to recover the solid matter. The collected white solid was put in a magnetic dish and heated at 120 ° C. for 3 hours in an air atmosphere using an electric furnace. Subsequently, the temperature was raised to 450 ° C., and then maintained at 450 ° C. for 12 hours. After heating, the mixture was allowed to stand until it reached room temperature to obtain 10.9 g of optical semiconductor particles 8. This photo semiconductor particle 8 was a white powder and contained 4.4 wt% Ca and 1.9 wt% P by fluorescent X-ray analysis.

(Comparative Example 1)
(9-A; Preparation of mixed solution 9)
In the same manner as in Example 1, a mixed solution 9 was obtained. In the mixed liquid 9, after the stirring was stopped and the mixture was allowed to stand for 30 minutes, the supernatant liquid remained cloudy.
(9-B; Preparation of coarse particle liquid 9)
For comparison, a coagulant was not used, so the coarse particle liquid 9 was not prepared.
(9-C; Preparation of optical semiconductor particles 9)
24.0 g of optical semiconductor particles 9 were obtained from the total amount of the mixed liquid 9 in the same manner as in Example 1 (1-C). The optical semiconductor particles 9 is white powder, silicon content 5.4 wt%, a specific surface area of 190.4m ² / g, silicon supported amount per surface area of 1 m ² is 0.28 mg, the sodium content was 150ppm .

(Comparative Example 2)
(10-A; Preparation of mixed solution 10)
One-third of the amount of the mixed solution 3 was separated to obtain a mixed solution 10. In the mixed solution 10, the supernatant liquid remained cloudy even after stirring was stopped and left for 30 minutes.
(10-B; Preparation of coarse particle liquid 10)
For comparison, a coagulant was not used, so the coarse particle liquid 10 was not prepared.
(10-C; Preparation of optical semiconductor particle 10)
Instead of the mixed liquid 1, the mixed liquid 10 was used in the same manner as in Example 1 (1-C) to obtain 40.9 g of optical semiconductor particles 10. The optical semiconductor particles 10 is white powder, silicon content 6.2 wt%, a specific surface area of 218.6m ² / g, silicon supported amount per surface area of 1 m ² is 0.28 mg, the sodium content was 180ppm .

(Comparative Example 3)
(11-A; Preparation of mixed solution 11)
The liquid mixture 11 was obtained like Example 5 (5-A). The mixture 11 remained cloudy even after stirring was stopped and allowed to stand for 30 minutes.
(11-B; Preparation of coarse particle liquid 11)
For comparison, the flocculant was not used, so the coarse particle liquid 11 was not prepared.
(11-C; Preparation of optical semiconductor particles 11)
19.5g of optical semiconductor particles 11 were obtained using the liquid mixture 11 instead of the liquid mixture 1 in the same manner as in Example 1 (1-C). This optical semiconductor particle 11 is a white powder, the silicon content is 4.8% by weight, the specific surface area is 186.0 m ² / g, the silicon loading per surface area of 1 m ² is 0.26 mg, the sodium content is 60 ppm, the potassium content. It was 90 ppm.

(Comparative Example 4)
(12-A; Preparation of mixed solution 12)
A liquid mixture 12 was obtained in the same manner as in Example 6 (6-A). The liquid mixture 12 remained cloudy even after stirring was stopped and allowed to stand for 30 minutes.
(12-B; Preparation of coarse particle liquid 12)
For comparison, no coagulant was used, so the coarse particle liquid 12 was not prepared.
(12-C; Preparation of optical semiconductor particles 12)
Instead of the mixed liquid 1, the mixed liquid 12 was used in the same manner as in Example 1 (1-C) to obtain 21.1 g of the optical semiconductor particles 12. This optical semiconductor particle 12 was a white powder, and had a silicon content of 1.4% by weight, a specific surface area of 56.4 m ² / g, a silicon loading amount of 0.22 mg per 1 m ^{2 of} surface area, and a sodium content of 40 ppm.

(Comparative Example 5)
(13-A; Preparation of liquid mixture 13)
A liquid mixture 13 was obtained in the same manner as Example 8 (8-A). The liquid mixture 13 remained cloudy even after stirring was stopped and the mixture was allowed to stand for 30 minutes.
(13-B; Preparation of coarse particle liquid 13)
For comparison, a coagulant was not used, so the coarse particle liquid 13 was not prepared.
(13-C; Preparation of optical semiconductor particles 13)
10 g of the mixed solution 13 was put in 10 centrifuge tubes, and each of the following (a) to (d) was repeated 5 times for washing.
(A) It was processed at 3000 rpm for 10 minutes with a centrifuge (manufactured by Kokusan Co., Ltd., H-18) to precipitate the solid matter.
(B) Decanting off the supernatant.
(C) 10 g of pure water was added,
(D) The solid matter was dispersed by ultrasonic irradiation and shaking.
Next, the contents of the 10 centrifuge tubes were filtered under reduced pressure to collect solid matter. The collected white solid was put in a magnetic dish and heated at 120 ° C. for 3 hours in an air atmosphere using an electric furnace. Subsequently, the temperature was raised to 450 ° C., and then maintained at 450 ° C. for 12 hours. After heating, the mixture was allowed to stand until it reached room temperature to obtain 10.9 g of optical semiconductor particles 13. This optical semiconductor particle 13 was a white powder, and contained 4.1 wt% Ca and 1.8 wt% P by fluorescent X-ray analysis.

Example 9
<Evaluation of preparations>
(1. Measurement of flow rate)
As necessary, the coarse particle liquids 1 to 8 and the mixed liquids 9 to 13 were diluted with water to adjust the slurry concentration to 5% by weight, and the liquid passing speed in the filtration treatment was measured by the following method.
A membrane filter is sandwiched between glass filter holders for vacuum filtration (Advantech Toyo Co., Ltd., KGS-47, funnel volume 110 mL, effective filtration area 9.6 cm ² ). A vacuum filtration device was prepared. At this time, the holder base was placed so that the filtrate was collected in the graduated cylinder and the holder base foot was stuck in the mouth of the graduated cylinder. Next, the decompression vessel was decompressed with an aspirator, and 30 mL of the sample solution was poured onto the top of the filter. And the time until 15 mL of filtrate was accumulated, that is, the time for 10 mL to flow, was measured with the time when 5 mL of filtrate was accumulated as the start time. The measurement results are shown in Table 1 together with the substrate, the slurry concentration of the mixed solution, the ceramic raw material, and the amount of the coagulant used in the preparation of each sample solution.

(2. Photodegradation performance evaluation of optical semiconductor particles)
The photo-semiconductor particles 1 to 13 were suspended in a methylene blue aqueous solution and irradiated with light, and the photodegradation activity was tested by quantifying the concentration of methylene blue in the liquid by spectroscopic analysis. The test operation method is as follows.
(Preparation of optical semiconductor particle suspension)
45 g of methylene blue aqueous solution having a concentration of 40 × 10 ⁻⁶ mol / L was weighed into a 100 cc polyethylene wide-mouthed bottle in which a fluororesin stirrer was previously placed. Next, 10 mg of photo-semiconductor particles were added while stirring with a magnetic stirrer. Then, after stirring vigorously for 5 minutes, the stirring strength was adjusted to such an extent that the liquid did not scatter and stirring was continued.
(Preliminary adsorption treatment)
Starting from the moment when the photo semiconductor particles were added, stirring was continued for 60 minutes without light irradiation. After 60 minutes, 3.0 cc of the suspension was collected and used as a sample before light irradiation.
(Photolytic treatment)
3.5 cc of the suspension after the pre-adsorption treatment was extracted, and a quartz standard spectroscopic cell (Tosoh Quartz Co., Ltd., outer dimensions 12.5 × 12.5 × 45 mm, optical path width 10 mm, which was previously filled with a fluororesin stirrer. , Optical path length 10 mm, volume 4.5 cc), and stirred with a magnetic stirrer. Next, light was irradiated for 5 minutes from the outside / lateral direction of the spectroscopic cell. Light irradiation was performed through a quartz filter container filled with pure water using a light source device SX-UI151XQ (USHIO Inc., 150 W xenon short arc lamp) as a light source. The amount of irradiation light was 5.0 mW / cm ² when the highest luminance portion was measured with an ultraviolet illuminance meter UVD-365PD (USHIO INC., Test wavelength 365 nm). After irradiation, the suspension in the spectroscopic cell was collected and used as a sample after light irradiation.
(Quantitative determination of methylene blue)
A membrane filter (Toyo Roshi Kaisha, DISMIC-13HP) was attached to an all plastic 5cc syringe. The sample suspension before and after the light irradiation was put into this, respectively, and extruded with a piston to remove the optical semiconductor particles. At that time, the first half amount of the filtrate was discarded, and the latter half amount of the filtrate was collected in a semi-micro type disposable cell for visible light analysis (made of polystyrene, optical path width 4 mm, optical path length 10 mm, volume 1.5 cc). Then, using a UV-visible spectrophotometer (UV-2550, Shimadzu Corporation), the absorbance at a wavelength of 680 nanometers was measured, and the methylene blue concentration was calculated. The reason for discarding the first half of the filtrate is to avoid the influence of the phenomenon that methylene blue is adsorbed on the membrane filter attached to the syringe and the concentration changes due to the initial adsorption of the membrane filter. This is because the adsorption is saturated and the concentration of the sample solution can be measured correctly.
The photolytic activity is shown in Table 2 as the methylene blue adsorption rate from the methylene blue concentration before the light irradiation based on the initial concentration of methylene blue, and as the methylene blue decomposition rate from the methylene blue concentration after the light irradiation based on the methylene blue concentration before the light irradiation. It was.

(3. Determination of presence or absence of pores derived from silicon oxide film by pore distribution measurement)
Using autosorb (manufactured by Cantachrome), measure the nitrogen adsorption isotherms of photo-semiconductor particles 1-7, 9-12, and titanium oxide ST-01 and P-25 in the desorption process under liquid nitrogen (77K) did. In addition, the titanium oxide used what dried after giving a baking process at 200 degreeC for 3 hours.
First, vacuum deaeration at 100 ° C. was performed as a pretreatment, and then a nitrogen adsorption isotherm of each sample was measured, and a log differential pore volume distribution curve was obtained by analyzing the result by the BJH method.
Next, the presence or absence of pores derived from the silicon oxide film was determined. Specifically, the photo-semiconductor particles 1 to 5 are ST-01, the photo-semiconductor particles 6 and 7 are P-25, and a log differential pore volume distribution curve is compared to determine the presence or absence of pores derived from a silicon oxide film. Was judged. The determination results are shown in Table 2.

  In the production method of the present invention, when producing optical semiconductor particles obtained by immobilizing ceramics on the surface of a metal compound optical semiconductor and performing performance modification, the solid-liquid separation is simplified, and the optical semiconductor particle is used as an optical semiconductor. Since it does not affect the performance, it can be used for the production of optical semiconductor particles used as cosmetics, pigments, photocatalysts and the like.

It is a figure which shows the log differential pore volume distribution curve (solid line) of the optical semiconductor particle 1, and the log differential pore volume distribution curve (dotted line) of titanium dioxide ST-01 corresponding to the base. It is a figure which shows the log differential pore volume distribution curve (solid line) of the optical-semiconductor particle 5, and the log differential pore volume distribution curve (dotted line) of titanium dioxide ST-01 applicable to the base | substrate. It is a figure which shows the log differential pore volume distribution curve (solid line) of the optical-semiconductor particle 6, and the log differential pore volume distribution curve (dotted line) of the titanium dioxide P-25 applicable to the base | substrate.

Claims (19)

A method for producing optical semiconductor particles comprising a base that is a metal compound optical semiconductor and ceramics immobilized on at least a part of the surface of the base, wherein the ceramics is a compound different from the base, and The manufacturing method of the optical semiconductor particle which consists of the process of (A)-(D).
(A) a step of mixing the substrate, ceramics or a raw material thereof, and a water-containing solvent to prepare a mixed solution containing the substrate on which ceramic or a precursor thereof is immobilized on at least a part of the surface, and water;
(B) adding a flocculant to the mixed solution and stirring the mixture;
(C) a step of recovering from the water-containing solvent the solid body containing the substrate on which ceramics or a precursor thereof is immobilized on at least a part of the surface, and a flocculant;
(D) A step of decomposing the flocculant by heating the solid matter.   A step of washing the substrate having ceramics or a precursor thereof immobilized on at least a part of the surface between steps (B) and (C) or between steps (C) and (D) ( The manufacturing method of the optical-semiconductor particle of Claim 1 which also includes E).   When the step (E) is based on the flow of the water-containing solvent, and the flow rate of the liquid separating the solid and the washing waste liquid is divided into a horizontal vector component and a vertical vector component, The method for producing optical semiconductor particles according to claim 2, wherein the cleaning is performed by controlling the supply amount of the hydrous solvent so that the rising speed of the liquid as a vector component in the vertical direction is slower than the settling speed of the solid.   The method for producing optical semiconductor particles according to any one of claims 1 to 3, wherein the flocculant is a polymer flocculant.   The method for producing optical semiconductor particles according to claim 4, wherein the polymer flocculant is nonionic.   6. The method for producing optical semiconductor particles according to claim 5, wherein the nonionic polymer flocculant is a polymer compound containing one or more partial structures selected from the group consisting of acrylamide or a modified product thereof as a repeating unit.   The method for producing optical semiconductor particles according to claim 1, wherein the substrate is made of an oxide of titanium.   The method for producing an optical semiconductor particle according to any one of claims 1 to 7, wherein the optical semiconductor particle is a photocatalyst.   The method for producing optical semiconductor particles according to any one of claims 1 to 8, wherein the ceramic is made of silicon oxide. The method for producing optical semiconductor particles according to claim 9, wherein the ceramic is silicon oxide fired at 400 ° C or higher and 1000 ° C or lower.   Step (A) mixes at least one set of the hydrous solvent containing the substrate and the silicate, the hydrous solvent containing the silicate and the substrate, and the hydrous solvent containing the substrate and the hydrous solvent containing silicate. The method for producing optical semiconductor particles according to claim 9 or 10, wherein the method is a step of mixing while maintaining a pH of a mixed solution containing both the substrate and the silicate at 5 or less.   Silicon oxide in which the silicon oxide is immobilized in a film shape on at least a part of the surface of the substrate and has no pores in the pore size distribution measurement in the region of 20 to 500 angstroms by the nitrogen adsorption method It is a film | membrane, The manufacturing method of the optical-semiconductor particle as described in any one of Claim 9 to 11. The method for producing an optical semiconductor particle according to any one of claims 9 to 12, wherein the amount of silicon supported per 1 m ² of the surface area of the optical semiconductor particle is 0.10 mg or more and 2.0 mg or less.   The method for producing an optical semiconductor particle according to claim 9, wherein the optical semiconductor particle is an optical semiconductor particle containing 1 ppm or more and 1000 ppm or less of an alkali metal.   The method for producing optical semiconductor particles according to claim 9, wherein the silicon oxide contains an alkali metal.   The method for producing optical semiconductor particles according to claim 1, wherein the ceramic is apatite.   The method for producing optical semiconductor particles according to any one of claims 1 to 8, wherein the ceramic comprises a compound of calcium and phosphorus.   The step (A) is a step of forming a compound of calcium and phosphorus on the surface of the substrate using a water-soluble calcium salt and a water-soluble phosphate compound as the raw material. The manufacturing method of the optical-semiconductor particle as described in any one. The method for producing optical semiconductor particles according to any one of claims 16 to 18, wherein the step (A) is a step of forming a compound of calcium and phosphorus on the surface of the substrate using a simulated body fluid.

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