JP2004057878A - Method of producing photocatalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a photocatalyst by which calcium phosphate is formed on the surface of a metal oxide in such a short period of time as only enough to satisfy industrial application. <P>SOLUTION: The method of producing a photocatalyst includes a step ST100 for mixing a powdery metal oxide as a starting material in a stock solution, a step ST102 for dispersing the powdery metal oxide mixed in the stock solution, a step ST104 for irradiating those with microwaves, a step ST106 for separating the metal oxide from the stock solution by filtration, and a step ST108 for drying the separated metal oxide by heating. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a photocatalyst exhibiting photocatalytic activity.
[0002]
[Prior art]
Photocatalysts using metal oxides such as titanium oxide as photocatalysts are attracting attention for their application to environmentally conscious processes that convert clean light energy into chemical energy. I have. In particular, it is known that by doping titanium oxide with an anionic element such as nitrogen or sulfur, it exhibits photoactivity not only in the ultraviolet region but also in the visible light region, such as in sunlight or indoors where ultraviolet light is weak. Researches have been made on the application of such materials as decomposition and removal of harmful substances such as nitrogen oxides, deodorization, antibacterial, antifouling, and hydrophilic materials in combination with an environment or a visible light source.
[0003]
Usually, a metal oxide such as titanium oxide is obtained as a powder and is difficult to handle as it is. Therefore, a photocatalyst containing the metal oxide is often kneaded into a substrate such as an organic fiber or a plastic. However, there is a problem that these base materials themselves are deteriorated by the photocatalytic effect of the photocatalyst.
[0004]
In order to solve such a problem, a metal oxide having a coating layer of calcium phosphate such as hydroxyapatite formed on the surface thereof has been developed. JP-A-11-267519 discloses a technique in which fine particles of titanium dioxide are dispersed in an aqueous slurry containing an anionic surfactant, and then at least a part of the surface of the fine particles of titanium dioxide is coated with porous calcium phosphate. Have been. Specifically, tricalcium phosphate _Ca 3 _{(PO 4)} calcium phosphate compounds represented by various rational formula, beginning ₂ into a simulated body fluid _{containing, NaCl, NaHCO 3, KCl,} K 2 HPO 4 · 3H _An aqueous slurry is prepared by adding ₂ O, MgCl ₂ .6H ₂ O, CaCl ₂ , Na ₂ SO _4, NaF, or the like, and titanium dioxide fine particles are mixed and dispersed in the aqueous slurry, and the mixture is maintained at a temperature of 40 ° C. for 24 hours. By doing so, porous calcium phosphate is precipitated on the surface of the titanium dioxide fine particles.
[0005]
In this way, by depositing porous calcium phosphate having no photocatalytic property on the surface, forming a coating barrier on the surface of titanium dioxide, and preventing direct contact between the photocatalyst and a substrate such as organic fiber or plastic, the basic Deterioration of the material can be prevented.
[0006]
In addition, it is said that calcium phosphate provided on the surface has an effect of adsorbing harmful substances in the atmosphere, and has an effect of more exerting the photocatalytic action of the metal oxide photocatalyst.
[0007]
[Problems to be solved by the invention]
However, in the above prior art, a simulated body fluid was required to form calcium phosphate on the surface of the metal oxide. Therefore, there has been a problem that an extremely large number of chemical substances are required, and furthermore, an adjustment process for adjusting the ion concentration to an optimum state and a pH adjustment are required.
[0008]
In addition, a long-term treatment of 24 hours or more was required for precipitation of calcium phosphate, which was insufficient as an industrial production method.
[0009]
Further, despite the above-described action of calcium phosphate, the metal oxide photocatalyst coated with calcium phosphate actually has a problem that the photocatalytic action is reduced. In particular, in a nitrogen-doped or sulfur-doped metal oxide photocatalyst having a high photocatalytic activity in the visible light region, the photocatalytic action was significantly reduced with the formation of the calcium phosphate coating layer.
[0010]
An object of the present invention is to provide a method for producing a photocatalyst in which calcium phosphate is formed on the surface of a metal oxide in a short time without requiring a simulated body fluid, in view of the above-mentioned problems of the related art.
[0011]
Still another object of the present invention is to provide a photocatalyst in which a coating layer of calcium phosphate is formed and which exhibits high photoactivity in a visible light region in view of the above-mentioned problems of the related art.
[0012]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problem is a method for producing a photocatalyst containing a metal oxide having calcium phosphate as a coating layer, comprising a raw material containing at least calcium ions and phosphate ions or at least calcium ions and hydrogen phosphate ions. The method includes a step of immersing a metal oxide in a solution and irradiating the solution with microwaves, wherein calcium phosphate is deposited as a coating layer on at least a part of the surface of the metal oxide.
[0013]
Further, the method for producing a photocatalyst includes a step of extracting a metal oxide obtained by precipitating the calcium phosphate from the raw material solution, and a step of heating the extracted metal oxide at 100 ° C. or more and 600 ° C. or less. Is preferred.
[0014]
Further, in the method for producing a photocatalyst, the raw material solution preferably contains an anionic surfactant.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
As shown in FIG. 1, the method for manufacturing a photocatalyst according to the embodiment of the present invention includes a mixing step ST100, a dispersion step ST102, a microwave irradiation step ST104, an extraction step ST106, and a heating step for a metal oxide powder as a raw material and a raw material solution. -It includes a drying step ST108.
[0017]
The raw material metal oxides are titanium oxide (TiO ₂ ), iron oxide (Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), tin oxide (SnO ₂ ), bismuth oxide (Bi ₂ O ₃ ), and niobium oxide (Nb). ₂ O ₅ ), nickel oxide (NiO), copper oxide (Cu ₂ O), zirconium oxide (ZrO ₂ ), zinc oxide (ZnO), strontium titanate (SrTiO ₃ ), barium titanate (BaTiO ₃ ), titanic acid It is preferable to include any one of iron (FeTiO ₃ ) and silicon oxide (SiO ₂ ) or a combination thereof.
[0018]
The metal oxide may be a powdery or granular material, or may be a thin film formed on a predetermined substrate such as glass, metal, and plastic. In the case of a powder, it is preferable that the average particle size of the primary particles is 0.001 μm or more and 0.2 μm or less.
[0019]
Further, it is more preferable to use one obtained by doping the above metal oxide with at least one of nitrogen and sulfur. The doping of nitrogen and sulfur is preferably 0.01 atomic% or more and 13 atomic% or less based on the metal oxide. In particular, titanium oxide (Ti-ON) containing nitrogen as a dopant is more preferable because it exhibits high photocatalytic activity even in the visible light region having a wavelength of 380 nm or more.
[0020]
The raw material solution uses ion-exchanged water as a solvent and contains calcium ion (Ca ²⁺ ) and phosphate ion ((PO ₄ ) ³⁻ ) or hydrogen phosphate ion ((HPO ₄ ) ^{2 −} , (H ₂ PO ₄ )). ^- ) Can be used. For example, a simulated body fluid further containing potassium chloride (KCl) and sodium chloride (NaCl) in calcium chloride (CaCl ₂ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), and potassium hydrogen phosphate (KH ₂ PO ₄ ) Can be used. However, it is not limited to this, and any material containing Ca ²⁺ and (PO ₄ ) ^3- may be used.
[0021]
The Ca ²⁺ ion concentration in the raw material solution is preferably 0.01 to 2.00% by weight, particularly preferably 0.05 to 1.00% by weight, based on the titanium oxide photocatalyst doped with an anion. At this time, the ion concentration of Ca ^{2+ in} the raw material solution is 0.1 mM or more and 50 mM or less, and the ion concentration of (PO ₄ ) ³⁻ or (HPO ₄ ) ^{2 −} , (H ₂ PO ₄ ) ⁻ is 0.1 mM. It is preferable that the concentration is not less than 50 mM. The pH may be 3 or more and 11 or less, and particularly preferably 6 or more and 9 or less.
[0022]
It is preferable to use water as a solvent for the raw material solution. In particular, it is preferable to use high-purity water, such as ion-exchanged water, in order to avoid contamination by contaminants in the photocatalyst. It is also preferable to use an organic solvent such as alcohol and acetone in addition to water.
[0023]
An anionic surfactant may be further added to the raw material solution. The anionic surfactant preferably contains at least one of fatty acid soda soap, potassium oleate soap, alkyl ether carboxylate and the like.
[0024]
The method for manufacturing a photocatalyst in the present embodiment is performed by the following process using these raw materials.
[0025]
In the mixing step ST100, the metal oxide and the raw material solution are mixed. At this time, it is preferable to mix the metal oxide at a ratio of 0.1 mg to 10 g with respect to 100 ml of the raw material solution. If the mixing amount is larger than this, the precipitated amount of calcium phosphate becomes excessive, and the photocatalytic activity of the resulting photocatalyst decreases. In addition, when the mixing amount is smaller than this, the precipitation rate of calcium phosphate in the following treatment decreases, and it becomes difficult to obtain an industrially sufficient treatment speed.
[0026]
The container for storing the raw material solution is preferably a container that transmits electromagnetic waves, such as a glass container and a plastic container. For example, a glass beaker or the like can be used.
[0027]
When processing is performed on a metal oxide thin film formed on a substrate, the substrate on which the thin film is formed is immersed in a raw material solution.
[0028]
In the dispersion step ST102, the metal oxide is dispersed in the raw material solution as a substantially non-precipitated slurry. For the dispersion treatment, a mechanical slurry disperser generally used widely can be used. However, when the metal oxide is a thin film on the substrate, the treatment in this step is unnecessary.
[0029]
In the microwave irradiation step ST104, the raw material solution in which the metal oxide is dispersed is irradiated with microwave to deposit calcium phosphate on the surface of the metal oxide.
[0030]
The irradiation power density of the microwave is preferably 0.01 W / ml or more and 10 W / ml or less with respect to the amount of the raw material solution. Further, it is preferable that the frequency of the microwave is not less than 10 MHz and not more than 50 GHz. In particular, it is more preferable that the frequency is 1 GHz or more and 10 GHz or less. The microwave irradiation time is preferably 30 seconds or more and 1 hour or less.
[0031]
The microwave irradiation is performed while keeping the raw material solution from boiling. Specifically, it is preferable to perform microwave irradiation while maintaining the temperature of the raw material solution at 40 ° C. or higher and 80 ° C. or lower. In particular, it is more preferable to perform the treatment while maintaining the temperature at 60 ° C. or more and 80 ° C. or less.
[0032]
However, these microwave irradiation conditions include the ion concentration in the raw material solution, the amount of the mixed metal oxide, the form of the metal oxide (whether powdery or thin film), the average particle size of the metal oxide, The composition, coverage and shape of the resulting calcium phosphate can be controlled by appropriately changing the irradiation power density and frequency of the microwave, the material of the container of the raw material solution, and the like.
[0033]
In the extraction step ST106, a metal oxide in which calcium phosphate is precipitated from the raw material solution is extracted. The extraction can be performed by filtering the metal oxide powder using a filter such as filter paper. When the metal oxide is formed on the substrate, it is only necessary to take out the substrate from the raw material solution.
[0034]
In addition, the raw material solution can be used as a slurry or a coating liquid without performing the extraction treatment. In this case, it is preferable to adjust the characteristics of the raw material solution by pH treatment or the like according to the intended use.
[0035]
In the heating / drying step ST108, the extracted metal oxide is heated and dried. At this time, the heating temperature is preferably 100 ° C. or more and 600 ° C. or less. In particular, the temperature is more preferably 300 ° C. or more and 600 ° C. or less. The heating time is not particularly limited, but is preferably 10 minutes or more and 5 hours or less.
[0036]
In the present embodiment, the extraction step ST106 and the heating / drying step ST108 are performed, but these steps may be omitted. However, as described in the following examples, the action of the photocatalyst can be improved by performing the heating and drying treatment.
[0037]
By the above treatment, a photocatalyst in which calcium phosphate is precipitated on the surface of the metal oxide can be obtained. FIG. 2 shows an example of an aspect of the photocatalyst obtained by the present embodiment. The calcium phosphate is formed as a plate-like precipitate protruding from the surface of the metal oxide as shown in FIG. Further, with the change in the processing conditions, as shown in FIG. 2B, there is a case where a conical precipitate protruding from the surface of the metal oxide is formed.
[0038]
The composition of calcium phosphate is a compound containing Ca ₉ (PO ₄ ) ₆ as a main component, and specifically, tricalcium phosphate (Ca ₃ (PO ₄ ) ₂ ), hydroxyapatite (Ca ₁₀ (PO ₄ ) _{6. (OH) 2),} dibasic calcium phosphate dihydrate _{(CaHPO 4 · 2H 2 O)} , octacalcium phosphate _{(Ca 8 H 7 (PO 4} ) 6 · 5H 2 O) or tetra calcium phosphate _{(Ca 4} O _(PO 4 ₂ ) etc. are included. Particularly, it is preferably hydroxyapatite (Ca ₁₀ (PO ₄ ) _6. (OH) ₂ ). However, the compounds are not limited to these exemplified compounds, and may be porous calcium phosphate, and may contain a small amount of impurities.
[0039]
Further, as shown in FIG. 3, the cross section of the titanium oxide granular material having a double structure of a bulk portion doped with at least one of nitrogen and sulfur and a surface layer containing neither nitrogen nor sulfur, Calcium phosphate can also be precipitated on the surface. Titanium oxide having a double structure can be obtained by forming an undoped surface layer on the outer periphery of a nitrogen-doped bulk portion using a thermal oxidation method, a plasma irradiation method, a sol-gel method, or the like.
[0040]
Since the surface layer of undoped titanium oxide has higher hydrophilicity than titanium oxide doped with nitrogen, a higher photocatalytic action can be exerted on nitrogen-doped titanium oxide having no surface layer. By depositing calcium phosphate on the surface of this double-structured titanium oxide, a high photocatalytic action can be obtained by a synergistic effect of the hydrophilic action of the surface layer and the adsorption action of the calcium phosphate coating layer.
[0041]
Furthermore, by having a double structure, the surface layer, which is an undoped layer, functions as a buffer layer, and it is possible to prevent an adverse effect on the photocatalytic action on the bulk portion due to precipitation of calcium phosphate.
[0042]
As described above, according to the present embodiment, the time for precipitating calcium phosphate can be reduced to about 1/20 of that of the related art. Further, even if the time of the heat treatment in the heating / drying step is taken into consideration, the manufacturing time can be reduced to about 1/5 of the conventional one.
[0043]
In addition, the raw material solution may contain at least Ca ²⁺ and (PO ₄ ) ³⁻ or hydrogen phosphate ions ((HPO ₄ ) ^{2 −} , (H ₂ PO ₄ ) ⁻ ). Since it is not necessary to adjust the concentration of various types of ions as described above, the manufacturing process can be simplified.
[0044]
Furthermore, by heating and drying the metal oxide coated with calcium phosphate, a decrease in the photocatalytic action can be suppressed. Further, the photocatalytic action can be improved by the adsorption action of calcium phosphate and the like. In particular, the effect is remarkable in a nitrogen-doped or sulfur-doped metal oxide photocatalyst having high photocatalytic activity in the visible light region.
[0045]
The photocatalyst obtained according to the present embodiment includes natural fibers, artificial fibers, plastics, paper, sheets in a vehicle interior, contents parts such as package trays, touch panel parts, car parts such as handles, artificial flowers, air purifier filters, and mirrors. The effect can be exhibited by using it for glass, outer walls, tiles, bathroom members and the like.
[0046]
<Example 1>
Hereinafter, an example in which nitrogen-doped titanium oxide (Ti-ON) which is a metal oxide having photocatalytic activity in the visible light region (420 nm or more) is treated will be described.
[0047]
Nitrogen-doped titanium oxide powder (Ti-ON) is obtained by subjecting titanium oxide (TiO ₂ ) powder (ST01, manufactured by Ishihara Sangyo) to a heat treatment at 600 ° C. for 3 hours in an air stream containing ammonia. Produced by
[0048]
The raw material solution was prepared by adding 100 mg of CaCl ₂ , 1150 mg of NaHPO ₄ , and 200 mg of KH ₂ PO ₄ to 1 liter of ion-exchanged water to prepare a solution containing Ca ²⁺ and (PO ₄ ) ^3- . In this example, 8.0 g of NaCl, 200 mg of KCl, 100 mg of MgCl ₂ .6 (H ₂ O) and a surfactant were further added, and the treatment was performed using 27 ml of the raw material solution.
[0049]
To 27 ml of this raw material solution, 2.0 g of the above-mentioned nitrogen-doped titanium oxide (Ti-ON) was mixed, and ion-exchanged water was added to obtain a 277 ml raw material solution. Further, titanium oxide was dispersed in the raw material solution by a slurry disperser so as not to settle. At this time, the pH of the solution was 8.5.
[0050]
Thereafter, a microwave having an irradiation power of 70 W and a frequency of 2.45 GHz was irradiated for 10 minutes to deposit calcium phosphate on the surface of the nitrogen-doped titanium oxide powder.
[0051]
Further, a titanium oxide powder was extracted from the raw material solution using a filter, and subjected to a heating and drying treatment at 100 ° C., 200 ° C., and 300 ° C. for one hour in the air. Thus, a photocatalyst in which calcium phosphate (such as hydroxyapatite) was deposited on the surface of nitrogen-doped titanium oxide was obtained.
[0052]
The catalytic action of the photocatalyst was measured using a decomposition reaction of acetaldehyde into carbon dioxide (CO ₂ ) by a photocatalytic reaction. Specifically, a 1-liter container was filled with acetaldehyde at a concentration of 500 ppm, 0.1 g of a photocatalyst was put therein, and the photocatalytic action was measured from an increase in the CO ₂ concentration in the container when visible light was irradiated. . The visible light was emitted from a white fluorescent tube through an ultraviolet cut filter at an energy density of 0.9 mW / cm ² .
[0053]
FIG. 4 is a graph showing the measurement results of the catalytic action of the photocatalyst obtained in this example. The reaction rate was reduced by 60% as compared with that before the calcium phosphate precipitation treatment only by air drying after forming the photocatalyst. However, the addition of the heating and drying treatment at 100 ° C. or 200 ° C. restored the reaction rate to 75%. Further, when the heating and drying treatment at 300 ° C. was added, the reaction rate was improved up to 105% as compared with before the calcium phosphate precipitation treatment.
[0054]
Further, the crystallinity and composition of the photocatalyst without heating and drying treatment and the photocatalyst after heating and drying treatment at 300 ° C. were analyzed by X-ray diffraction and X-ray electron spectroscopy (XPS). There was no difference in crystallinity between the photocatalysts. In each composition ratio, Ca was 0.7 atomic% and P was 1.2 atomic%, and there was no difference in the chemical bonding state of Ca and P. That is, desorption of calcium phosphate did not occur by the heating and drying treatment.
[0055]
It is considered that the reason why the photocatalytic activity is improved by the heating and drying treatment is that the structure of calcium phosphate on the surface is stabilized and the gas adsorbing property is improved. It is also conceivable that at a concentration lower than the detection level, the catalytic reaction inhibitor covering the surface of titanium oxide (Ti-ON) was desorbed.
[0056]
In the above method, the calcium phosphate component, the photocatalyst powder, and the surfactant were all mixed in water and mechanically dispersed at the same time, and then subjected to microwave treatment.However, a slurry in which the photocatalyst powder was dispersed in advance was prepared, and calcium phosphate was prepared. Calcium phosphate can also be precipitated on the surface of the photocatalyst by microwave treatment after mixing the aqueous solution containing the components.
[0057]
<Example 2>
The Ti-O-N photocatalyst powder was prepared by heating titanium oxide (TiO ₂ ) powder (manufactured by Taki Chemical Co., A100) and urea in an equimolar mixture at 400 ° C. for 1 hour, and washing the surface residue with sulfuric acid. After that, it was further washed with water, dried at 120 ° C., and then finely pulverized to produce.
[0058]
The raw material solution was prepared by adding 100 mg of CaCl ₂ , 1150 mg of NaHPO ₄ , and 200 mg of KH ₂ PO ₄ to 1 liter of ion-exchanged water to prepare a solution containing Ca ²⁺ and (PO ₄ ) ^3- . In this example, 8.0 g of NaCl, 200 mg of KCl, and 100 mg of MgCl ₂ .6 (H ₂ O) were further added, and treatment was performed using 1350 ml of the raw material solution.
[0059]
In addition, a photocatalyst slurry was prepared by adding a surfactant to a mixture of 25 g of Ti-O-N photocatalyst powder and 225 g of ion-exchanged water and using a mechanical disperser to disperse the mixture so that no sedimentation occurred. .
[0060]
Thereafter, the two solutions are mixed and irradiated with microwaves having a frequency of 2.45 GHz for 30 seconds at an irradiation power of 1400 W, followed by irradiation at 70 W for 15 minutes to deposit calcium phosphate on the surface of the titanium oxynitride powder photocatalyst. I let it.
[0061]
In addition, the composition of calcium phosphate was analyzed using X-ray diffraction and X-ray electron spectroscopy (XPS). As a result, it was found that Ca was 0.2 at% and P was 1.2 at%, and that P formed phosphate ions.
[0062]
The catalytic action of the photocatalyst was measured using a decomposition reaction of acetaldehyde into carbon dioxide (CO ₂ ) by a photocatalytic reaction. Specifically, a 1-liter container was filled with acetaldehyde at a concentration of 500 ppm, 0.1 g of a photocatalyst was put therein, and the photocatalytic action was measured from the increase in the CO ₂ concentration in the container when visible light was irradiated. The visible light was emitted from a white fluorescent tube at an energy density of 0.9 mW / cm ² via an ultraviolet cut filter.
[0063]
As a result, the generated CO ₂ concentration after the visible light irradiation for 23 hours was 293.2 ppm in the sample before the deposition of calcium phosphate, whereas the sample in which the calcium phosphate was deposited by the microwave irradiation of the present invention was 259.9 ppm. Met. The formation of calcium phosphate on the surface reduced the number of active sites and slightly decreased the gas reaction rate, but it was found that this was a level at which there was no practical problem.
[0064]
In the above embodiment, the heat treatment temperature during powder production was 400 ° C., but any temperature within the range of 250 to 600 ° C. may be used. The mixing ratio of titanium oxide / urea may be in the range of 0.1-1000. The cleaning is not limited to sulfuric acid, and other chemicals may be used.
[0065]
<Example 3>
Hereinafter, examples in which nitrogen-doped zinc oxide (Zn-ON) is treated as a metal oxide will be described.
[0066]
Nitrogen-doped zinc oxide powder (Ti-ON) was prepared by subjecting zinc oxide powder to a heat treatment at 400 ° C. × 1 hour in an airflow of ammonia / argon = 2/1 at a flow rate ratio. .
[0067]
The raw material solution was prepared in the same manner as in Example 1. To 27 ml of the raw material solution, 2.0 g of the above-mentioned nitrogen-doped zinc oxide (Ti-ON) was mixed, and ion-exchanged water was added to obtain 277 ml of the raw material solution. In addition, zinc oxide was dispersed in the raw material solution by a slurry disperser so as not to settle.
[0068]
Thereafter, a microwave having an irradiation power of 70 W and a frequency of 2.45 GHz was irradiated for 10 minutes to precipitate calcium phosphate on the surface of the zinc oxide powder.
[0069]
Further, a zinc oxide powder was extracted from the raw material solution using a filter, and subjected to a heating and drying process in the atmosphere. Thus, a photocatalyst in which calcium phosphate was precipitated on the surface of nitrogen-doped zinc oxide was obtained.
[0070]
As in Example 1, the catalytic action of the photocatalyst was measured using a decomposition reaction of acetaldehyde into carbon dioxide (CO ₂ ) by a photocatalytic reaction. As a result, as in Example 1, it was found to have a high photocatalytic action in the visible light region.
[0071]
As a result of measurement using XPS, Ca was 0.4 at% and P was 0.3 at%. In addition, analysis of the chemical bonding state revealed that the surface contained PO ⁴⁻ . Further, Na ⁺ , Cl ⁻ , Mg ²⁺ , (CO ₃ ) ⁻ contained in the raw material solution are all 0.1 atomic% or less, and it is apparent that calcium phosphate such as hydroxyapatite is selectively precipitated. became.
[0072]
【The invention's effect】
According to the present invention, a method for producing a photocatalyst that forms calcium phosphate on the surface of a metal oxide without the need for complicated ion concentration adjustment for preparing a simulated body fluid and with a short treatment time that is sufficiently industrially sufficient is provided. Can be provided.
[0073]
Furthermore, according to the present invention, it is possible to provide a photocatalyst having a calcium phosphate coating layer on the surface and exhibiting high photoactivity in the visible light region.
[Brief description of the drawings]
FIG. 1 is a view showing a flowchart of a method for producing a photocatalyst according to an embodiment of the present invention.
FIG. 2 is a diagram showing an example of a form of a photocatalyst produced in an embodiment of the present invention.
FIG. 3 is a diagram showing a cross-sectional structure of a nitrogen-doped metal oxide photocatalyst produced in an embodiment of the present invention.
FIG. 4 is a graph showing the decomposition effect of acetaldehyde by titanium oxide (Ti—O—N) in Example 1.
[Explanation of symbols]
100 metal oxide, 102 calcium phosphate, 200 bulk of doped metal oxide, 202 surface layer of undoped metal oxide, 204 calcium phosphate.

Claims (3)

A method for producing a photocatalyst including a metal oxide having calcium phosphate as a coating layer,
A step of immersing the metal oxide in a raw material solution containing at least calcium ions and phosphate ions or at least calcium ions and hydrogen phosphate ions and irradiating with microwaves,
A method for producing a photocatalyst, comprising depositing calcium phosphate as a coating layer on at least a part of the surface of the metal oxide. The method for producing a photocatalyst according to claim 1, further comprising:
Extracting the metal oxide from which the calcium phosphate is precipitated from the raw material solution,
Heating the extracted metal oxide at 100 ° C. or higher and 600 ° C. or lower,
A method for producing a photocatalyst, comprising: The method for producing a photocatalyst according to claim 1 or 2,
The method for producing a photocatalyst, wherein the raw material solution further contains an anionic surfactant.

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