JP4766685B2 - Oxyapatite containing active oxygen, method for producing the same, and photocatalyst comprising the same - Google Patents

Description

The present invention relates to an oxyapatite containing active oxygen, a method for producing the same, and a photocatalyst using a photocatalytic oxyapatite structure comprising the same.

Hydroxyapatite, which is famous for the main components of living hard tissues such as teeth and bones, has a crystal structure belonging to hexagonal crystals. There are two crystallographically different positions of Ca in the crystal, which are 9-coordinated with oxygen (hereinafter also referred to as CaI) and 6-coordinated Ca (hereinafter also referred to as CaII). Therefore, the composition of hydroxyapatite can be expressed as [CaI] ₄ [CaII] ₆ (PO ₄ ) ₆ (OH) ₂ . In general, apatite forms a tunnel structure that runs in the c-axis direction centering on CaI and OH, and has ion migration and ion exchange capabilities along this tunnel.

Many methods for synthesizing hydroxyapatite have been studied for a long time, and in order to obtain the required properties, they are generally synthesized by heating in a humidified air atmosphere. There are also many synthetic reports on hydroxyapatite in which some or all of Ca and some or all of P are substituted with other atoms.

Hydroxyapatite has long been used in a wide range of fields, including ion exchangers, biological component adsorbents such as proteins, chromatographic adsorbents, humidity sensors, artificial roots, artificial bones, artificial organ bone substitutes, and basic cosmetics (non- Patent Document 1).

In recent years, using photocatalysts typified by titanium oxide, decomposition and removal of harmful substances released into the living environment, such as NOx and SOx, or decomposition and removal of malodorous components and oils that occur in daily living environments The importance of wastewater treatment and water sterilization is increasing. Therefore, for the purpose of improving the performance of the photocatalyst, studies have been made to add the action of adsorbing hydroxyapatite to the catalytic action of titanium oxide, and a photocatalyst (for example, Patent Documents 1 and 2) in which both are mixed, or titanium or the like is carried on the apatite itself. Thus, a photocatalyst having a catalytic action (Patent Document 3) has been proposed. However, further improvement is required for improving the photocatalytic performance, such as the photocatalytic performance is lowered because titanium oxide is partially coated with apatite, and the amount of titanium supported is limited due to the problem of maintaining the apatite structure.

Active oxygen typified by oxygen anion (O ⁻ ), superoxide anion (O ₂ ⁻ ), peroxide anion (O ₂ ²⁻ ), etc. is extremely reactive and has various oxidation reactions such as organic and inorganic substances. It is known that it plays an important role involved in (Non-patent Document 2). A substance containing active oxygen is expected to be applied to various uses of a catalyst such as a photocatalyst. For this reason, extensive research has been conducted on active oxygen adsorbed on the solid surface of an oxide compound as a catalytic action (Non-Patent Document 3). However, it is difficult to generate active oxygen easily and stably due to the instability of active oxygen, and most of these studies can be accomplished by irradiating high-energy radiation such as γ rays. As described above, since active oxygen is generated through a complicated process in the prior art, development of a new material that can be synthesized by a simple method has been desired.
Japanese Patent Laid-Open No. 10-244166 JP 2003-275601 A Japanese Patent No. 3678606 JCElliott, Structure and Chemistry of the Apatites and OtherCalcium Orthophosphates, Elsevier The Chemical Society of Japan, Reactive Oxygen chemistry, Quarterly Chemistry Review, Society Publishing Center, 1990, No7 JHLunsford, Catal. Rev. 1973, 8, 135

An object of the present invention is to provide a photocatalyst that is easy to synthesize, can contain active oxygen stably, and can maintain catalytic activity when irradiated with light.

As a result of intensive studies to solve the above-mentioned problems, the present inventors stably synthesized a substance composed of a composition obtained by partially substituting divalent ions at the CaII site with trivalent ions in a dry atmosphere. The present inventors have found a photocatalytic action that can contain active oxygen having a catalytic action and can maintain the catalytic activity when irradiated with light, and has reached the present invention.
That is, the present invention is as follows.
(1) Okishiapatai you want to contain active oxygen.
(2) The oxyapatite containing active oxygen according to (1) above, wherein the oxyapatite containing active oxygen has a photoactive point .
(3) The oxyapatite containing active oxygen according to (1) or (2) above, wherein the oxyapatite containing active oxygen is represented by the following general formula (1) .

M1 _a M2 _b (M3O ₄ ) ₆ XY (1)
(In the formula, M1 represents at least one element of Ca, Mg, Sr, Ba, Sn, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pb, Cd, and Ag, and M2 represents Sc. , Y, La, Sb, Bi, Eu, Nd, Al, Ga, In, and M3 represents P, Si, Mn, As, Cr, V, Ge, B, W, Represents at least one element of Mo, a + b = 10, 0.1 ≦ b ≦ 2.0, X represents at least one active oxygen of O ⁻ , O ₂ ⁻ , and O ₃ ⁻ , Y compensates for the charge of oxyapatite other than X, and O ²⁻ , O ₂ ²⁻ , OH ⁻ , F ⁻ , Cl ⁻ , I ⁻ , Br ⁻ , S ²⁻ , NCN ²⁻ , CO ^{_{3 2-, SO 4 2-, NO}} 2 2-, H -, e - represented by, Oki only X When the charge of the apatite is compensated, Y may not.)

(4) The oxyapatite containing active oxygen according to claim 3, wherein Y in the general formula (1) is O ²⁻ .

(5) oxy apatite represented by the following general formula, heating temperature 50 ° C. or higher 1800 ° C. or less, in claim 4, characterized in that it is obtained by treatment with the following dry Kiri囲gas water vapor partial pressure 10 2 ^Pa The manufacturing method of the oxyapatite containing the active oxygen of description.
M1 _a M2 _b (M3O ₄ ) ₆ Y
(M1 in the formula represents at least one element of Ca, Mg, Sr, Ba, Sn, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pb, Cd, and Ag,
M2 represents at least one element of Sc, Y, La, Sb, Bi, Eu, Nd, Al, Ga, In,
M3 represents at least one element of P, Si, Mn, As, Cr, V, Ge, B, W, and Mo.
a + b = 10, 0.1 ≦ b ≦ 2.0.
Y represents O ²⁻ . )
(6) A method for producing oxyapatite containing active oxygen as described in (4) above, wherein oxides, hydroxides, and carbonates of each element of M1, M2, and M3 in the general formula (1) A compound selected from the group consisting of chloride, chloride, fluoride, nitrate, sulfate, and alkoxy at a composition ratio that satisfies a + b = 10, 0.1 ≦ b ≦ 2.0, a heating temperature of 50 ° C. to 1800 ° C., and a water vapor partial pressure of 10 ² Pa The method for producing oxyapatite containing active oxygen according to claim 4, which is obtained by reacting in the following dry atmosphere.
(7) A method for producing active oxygen-containing oxyapatite, characterized in that the method for producing active oxygen-containing oxyapatite according to (5) or (6) further includes a step of irradiating light.
(8) A photocatalyst comprising oxyapatite containing active oxygen according to any one of (1) to (4).

The oxyapatite used for the photocatalyst of the present invention can contain active oxygen stably and is easy to synthesize. Furthermore, since it also has a photoactive point, the catalytic activity can be maintained by irradiation with light, and it can be used as an excellent photocatalyst.

The present invention is described in detail below.

The photocatalyst of the present invention is characterized by utilizing oxyapatite containing active oxygen.
The active oxygen in the present invention refers to O ⁻ , O ₂ ⁻ , O ₃ ^— , which may be contained in any one kind in the apatite structure, or may be contained as a mixture of plural kinds thereof. . The presence of active oxygen results in stronger photocatalysis.

The active oxygen in the present invention is detected by measuring at room temperature using electron paramagnetic resonance spectroscopy (EPR), for example, EMX manufactured by Bruker. The type of active oxygen can be determined from the value of g given from the spectrum, and the value can be determined from the value disclosed in Japanese Patent Laid-Open No. 2002-3218 by Hosono et al. For example, O ⁻ can be defined by gx = gy = 2.04 and gz = 2.00.

The concentration of active oxygen in the present invention can be determined by integrating the superposed spectrum composed of the spectra of each active oxygen and comparing it with the copper sulfate pentahydrate of the standard sample.

From the viewpoint of obtaining the effect of the present invention, the concentration of active oxygen contained in the oxyapatite used for the photocatalyst of the present invention is preferably 10 ¹⁴ cm ⁻³ or more, more preferably 10 ¹⁵ cm ⁻³ or more, Preferably it is 10 ¹⁶ cm ⁻³ or more, more preferably 10 ¹⁷ cm ⁻³ or more, and most preferably 10 ¹⁸ cm ⁻³ or more. The concentration of active oxygen is preferably as high as possible from the viewpoint of photocatalysis, but the practical upper limit is 10 ²¹ cm ⁻³ from the material composition and structure.

Having a photoactive point in the oxyapatite of the present invention means that there is a light absorption site in the oxyapatite when irradiated with light. That is, the oxyapatite in the present invention generates electrons in the conductor and holes in the valence band by photoexcitation when irradiated with light having a wavelength having energy greater than the band gap. These electrons and holes move to the vicinity of free O ²⁻ and oxygen on the surface, and active oxygen can be generated and the concentration thereof can be increased by the oxidation-reduction reaction here. Furthermore, since it also has an adsorption action which is one of the characteristics of apatite, various adsorbed substances adsorbed can be oxidized / reduced / decomposed. Since oxyapatite itself can assume both photocatalytic action and adsorption action, it is not necessary to mix titanium oxide and hydroxyapatite as in the prior art.

The oxyapatite used for the photocatalyst of the present invention is characterized by being represented by the compound of the general formula (1).

M1 _a M2 _b (M3O ₄ ) ₆ XY (1)
(In the formula, M1 represents at least one element of Ca, Mg, Sr, Ba, Sn, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pb, Cd, and Ag, and M2 represents Sc. , Y, La, Sb, Bi, Eu, Nd, Al, Ga, In, and M3 represents P, Si, Mn, As, Cr, V, Ge, B, W, Represents at least one element of Mo. a + b = 10 represents 0.1 ≦ b ≦ 2.0 X represents at least one active oxygen selected from O ⁻ , O ₂ ⁻ and O ₃ ⁻ , Y compensates for the charge of oxyapatite other than X, and O ²⁻ , O ₂ ²⁻ , OH ⁻ , F ⁻ , Cl ⁻ , I ⁻ , Br ⁻ , S ²⁻ , NCN ²⁻ , CO ^{_{3 2-, SO 4 2-, NO}} 2 2-, H -, e - represented by, Oki only X When the charge of the apatite is compensated, Y may not.)
The oxyapatite used in the photocatalyst of the present invention is not particularly limited as long as the above requirements are satisfied, but it is easy to achieve a high active oxygen content concentration, the synthesis is relatively easy, and the structure is stable. For example, Ca ₈ La ₂ (PO ₄ ) ₆ O ₂ , Ca ₈ Y ₂ (PO ₄ ) ₆ O ₂ , Ca ₈ Al ₂ (PO ₄ ) ₆ O ₂ , Ca ₈ In ₂ (PO ₄ ) ₆ O ₂ Ca ₈ La ₂ (SiO ₄ ) ₆ O ₂ is preferred. In particular, when used as a photocatalyst by visible light, Ca ₈ La ₂ (CrO ₄ ) ₆ O ₂ , Ca ₈ La ₂ (VO ₄ ) ₆ O ₂ , Ca ₈ Bi ₂ (VO ₄ ) containing Cr, V, Mn, etc. ) ₆ O ₂ , Ca ₈ La ₂ (MnO ₄ ) ₆ O ₂ , Ca ₈ Bi ₂ (MnO ₄ ) ₆ O _{2 and the} like are suitable.

These photocatalytic oxyapatites themselves contain active oxygen, and when irradiated with light, active oxygen generation occurs momentarily and continuously, increasing the concentration of active oxygen. In addition, oxyapatite has a high adsorption action. Therefore, adsorption of harmful substances and the like, and oxidation and decomposition of the adsorbed species can be performed with a single substance, and the efficiency of the catalyst and the manufacturing process are extremely superior compared to the conventional mixture of titanium oxide and hydroxyapatite.

The oxyapatite used for the photocatalyst of the present invention is characterized in that the effect of the present invention can be further improved by irradiation with light. The type of light used for light irradiation is not particularly limited, and examples thereof include visible light, ultraviolet light, extreme ultraviolet light, X-rays, and γ-rays. The light source is selected according to the composition of the oxyapatite to be used, and light having a wavelength having energy greater than or equal to the band gap is preferable. For irradiation, these light sources may be used alone or in combination. The time of light irradiation is not particularly limited as long as the effect of the present invention can be improved, but it is preferably 5 seconds or longer and 3 days or shorter, more preferably 10 seconds or longer and within 1 day, and most preferably 15 seconds or longer and 12 hours. Is within. By performing light irradiation, as described above , active oxygen can be generated and the catalytic activity can be maintained.

The oxyapatite used in the photocatalyst of the present invention is a heat treatment of a raw material composition having a composition satisfying M1, M2, M3, Y and a, b of the general formula (1) in an atmosphere having a water vapor partial pressure of 10 ² Pa or less. It is preferable to obtain by doing.

Although it does not specifically limit as said raw material compound used for this invention, The oxide of the element corresponding to M1, M2, M3, and Y in General formula (1), hydroxide, carbonate, chloride, Fluorides, nitrates, sulfates, alkoxides and the like can be mentioned.
Ordinarily, apatite has been sought to obtain properties by synthesis under steam or a humid atmosphere, as found in the prior art. However, in the present invention, active oxygen can be contained by synthesizing oxyapatite in a dry atmosphere having a water vapor partial pressure of 10 ² Pa or less without using conventional methods.

Hydroxyapatite used in the photocatalyst of the present invention is obtained by heat treatment in the following dry atmosphere water vapor partial pressure 10 ² Pa, preferably 10 ¹ Pa or less steam partial pressure, more preferably less steam partial pressure 10 ⁰ Pa, most The water vapor partial pressure is preferably 10 ⁻¹ Pa or less. As the type of gas, air, oxygen, nitrogen, argon, helium, or a mixed gas thereof can be used. By reducing the water vapor partial pressure, the concentration of active oxygen can be increased.

In the method for producing oxyapatite used for the photocatalyst of the present invention, the reaction is performed in a dry atmosphere having a heating temperature of 50 ° C. or more and 1800 ° C. or less and a water vapor partial pressure of 10 ² Pa or less at the time of apatite synthesis, It reacts in a dry atmosphere of 50 ° C. or higher and 1800 ° C. or lower and a water vapor partial pressure of 10 ² Pa or lower. Unlike conventional conventional means, it is possible to contain active oxygen in oxyapatite by reacting in the above dry atmosphere or by reacting in a dry atmosphere after normal apatite synthesis. In the production method of the present invention, a conventionally known method for synthesizing hydroxyapatite can be used without particular limitation, except that it is synthesized or reacted in a dry atmosphere.

As a known method for synthesizing hydroxyapatite, Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ will be described below, but the present invention is not limited thereto. Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ is a solid phase reaction method in which calcium triphosphate and calcium carbonate are reacted at 1000 ° C. or higher, and element substitution of chloroapatite is performed at 1000 ° C. or higher. Conversion reaction method to be performed, hydrothermal reaction method to grow crystals under 300 to 700 ° C hydrothermal conditions, reflux method to boil and heat brushite in water, hydrolyze brushite and calcium triphosphate at 100 ° C or less A hydrolysis method for converting to apatite, a precipitation reaction method in which a calcium salt aqueous solution and a phosphate aqueous solution are mixed and reacted under basic conditions of pH 8 to 10 can be used. In the case of a thin film form, a CVD method, a sputtering method, a laser ablation method, a sol-gel method or the like can be used. Also, floating melt zone method to obtain a single crystal, or the like can be used Czochralski method (e.g. Takafumi Kanazawa inorganic phosphorus chemical First Printing Kodansha P19～, Hideki Momma, Inorganicmaterials, 2, 401 (1995 )).

The oxyapatite used for the photocatalyst of the present invention can be produced by the above-mentioned method. Depending on the application, a method for increasing the surface area by making it porous, acicular, etc., a method for increasing the crystal density, and a cost reduction using a roughly purified material are aimed at. A method or the like can be used.

The oxyapatite used in the photocatalyst of the present invention may be mixed with impurities in the substance represented by the general formula (1) as long as the effect can be obtained. Impurities include substances obtained by non-stoichiometry, elements that are partially missing from the above general formula (1), and elements that are not included in the general formula (1) at all. Examples include substances.

When the oxyapatite used for the photocatalyst of the present invention contains impurities, the substance represented by the general formula (1) is preferably 50% to 100%, more preferably 70% to 100%, and still more preferably 80%. It is 100% or less and most preferably 90% or more and 100% or less. The more the substance represented by the general formula (1), the higher the concentration of active oxygen, which is preferable in order to achieve more effects.

The oxyapatite of the present invention can be used in a mixed state with other substances. Examples of the mixing include a state where it is simply mixed with oxyapatite, a state where it is kneaded near the melting point, a state where it is coated with oxyapatite, and a state where it is chemically bonded to a part of the oxyapatite structure. For example, powder before molding, paint for walls and glass, organic materials (polymers) / inorganic materials before thin film or film production, target materials used for making household goods / indoor equipment and thin films, medical devices, electronic It can be mixed in a surface coating solution such as equipment.

In the present invention, the mixed concentration of the oxyapatite used for the photocatalyst is not particularly limited as long as the function of the oxyapatite of the present invention can be expressed, but is preferably 0.1% to 80%, more preferably 1.0%. It is 50% or less and most preferably 3.0% or more and 40% or less.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not restrict | limited to an Example.

Evaluation methods and measurement methods used in the present invention are as follows.
(XRD) In RINT2000 manufactured by Rigaku Corporation, measurement is made using Cu Kα rays. Measurement conditions are an accelerating voltage 50 k V, accelerating current 200 mA, receiving slit width 0.15 mm, the scanning speed of 4 ° / min, a sampling 0.02 °. The diffraction lines are monochromatic by a graphite monochromator and counted. The structure is identified by using JADE made by MaterialsData or referring to past papers.
(IR) Use Spectrum One from Perkin Elmer. The measurement conditions are resolution of 1 cm ^-1 in a range of 400-4000cm ^-1. Confirm the OH stretching vibration observed around 3600 cm ⁻¹ .
(Heat resistance test) Process in an oven at 1400 ° C for 4 hours, and confirm the structural change by XRD measurement as described above.
(Photocatalytic ability test) 0.02 mmol / L methylene blue (Wako Pure Chemical Industries, Ltd.) to adjust the aqueous solution which is referred to as blank solution. On the other hand, oxyapatite is added to a 0.02 mmol / L methylene blue aqueous solution so as to be 0.05 g / L. Both were irradiated with light at 25 ° C while stirring, and using a spectrophotometer U4000 manufactured by Hitachi High Technology Co., Ltd., the amount of absorption peak of methylene blue near 660 nm was measured. Confirm the photocatalytic performance of oxyapatite from the amount of decomposition of methylene blue.

[Example 1]
2.00 g CaCO ₃ in (Ltd. Pure Chemical Laboratories) and 7.61 g CaHPO ₄ (Wako Pure Chemical Industries, Ltd.) and Ca ₂ P ₂ O ₇ and 3.25g of obtained by heating at 800 ° C. the la ₂ O ₃ ((Ltd.) pure chemical Laboratories) was wet-mixed in ethanol, to obtain a uniform mixed sample. The obtained sample was calcined in a dry oxygen flow (300 ml / min) at 1400 ° C. for 6 hours with a water vapor partial pressure of 6 Pa. The obtained compound could be assigned to the hexagonal apatite structure by XRD, and it was confirmed by IR analysis that there was no OH stretching. From the EPR measurement of the obtained compound, the concentration of active oxygen was quantified as 2 × 10 ¹⁶ cm ⁻³ . From the above, the synthesis of La ₂ Ca ₈ (PO ₄ ) ₆ O _{(2 + α)} was confirmed. (α represents an increase in oxygen atoms due to the presence of active oxygen.) The obtained compound was found to have excellent heat resistance without any change in structure even after the heat resistance test.

[Example 2]
Pure water 2.00g of _{Ca (NO 3) 2 · 4H} 2 O (( Ltd.) Pure Chemical Laboratories) and 0.81g of _{Y (NO 3) 3 · 6H} 2 O (( Ltd.) Pure Chemical Laboratories) Then, 30% aqueous ammonia was added to adjust the pH to about 10 to obtain a solution A. Meanwhile 0.84g of _{(NH 4) 2 HPO 4 (} ( Ltd.) Pure Chemical Laboratories) was added 30% aqueous ammonia dissolved in pure water and adjusted to about pH = 10 to obtain a solution B by. Both solutions were bubbled with nitrogen gas for 1 hour at room temperature to remove dissolved carbon dioxide gas.
Thereafter, with stirring, solution B with decarboxylated gas was added to solution A with decarboxylated gas while adding 30% aqueous ammonia so that the pH was about 10, thereby obtaining a precipitate. The resulting precipitate was heated at 90 ° C. for 24 hours in a dry oxygen flow (300 ml / min) with a water vapor partial pressure of 6 Pa.

The obtained compound could be assigned to the hexagonal apatite structure by XRD, and it was confirmed by IR analysis that there was no OH stretching. From the EPR measurement of the obtained compound, the concentration of active oxygen was quantified as 1 × 10 ¹⁶ cm ⁻³ . From the above, the synthesis of Y ₂ Ca ₈ (PO ₄ ) ₆ O _{(2 + α)} was confirmed. In addition, it was found that the obtained compound was excellent in heat resistance without any change in structure after the heat resistance test.

[Example 3]
The 2.00 g oxyapatite produced in Example 1 was irradiated with ultraviolet rays for 15 minutes. The obtained compound was assigned to a hexagonal apatite structure by XRD, and it was confirmed by IR analysis that there was no OH stretching. From the EPR measurement of the obtained compound, the concentration of active oxygen was quantified as 1 × 10 ¹⁷ cm ^−3, and the concentration of active oxygen was increased as compared with Example 1. In addition, it was found that the obtained compound was excellent in heat resistance without any change in structure after the heat resistance test.

[Example 4]
2.00 g CaCO ₃ (Ltd. Pure Chemical Laboratories) and 1.29g of V ₂ O ₅ in (Ltd. Pure Chemical Laboratories) and 0.81 g La ₂ O ₃ in (Co. high purity Chemical Research ) Was wet mixed in ethanol to obtain a uniformly mixed sample. The obtained sample was fired at 1300 ° C. for 6 hours in a 300 ml / min dry oxygen flow. The obtained compound could be assigned to the hexagonal apatite structure by XRD, and it was confirmed by IR analysis that there was no OH stretching. From the EPR measurement of the obtained compound, the concentration of active oxygen was quantified as 2 × 10 ¹⁶ cm ⁻³ . From the above, the synthesis of Ca ₈ La ₂ (VO ₄ ) ₆ O _{(2 + α)} was confirmed. In addition, it was found that the obtained compound was excellent in heat resistance without any change in structure after the heat resistance test.
[Example 5]
2.00 g CaCO ₃ (Ltd. Pure Chemical Laboratories) and 1.22g of V ₂ O ₅ in (Ltd. Pure Chemical Laboratories) and 0.57 g La ₂ O ₃ in (Co. high purity Chemical Research ) Was wet mixed in ethanol to obtain a uniformly mixed sample. The obtained sample was calcined at 1250 ° C. for 6 hours in a 300 ml / min dry oxygen flow. The obtained compound could be assigned to the hexagonal apatite structure by XRD, and it was confirmed by IR analysis that there was no OH stretching. From the EPR measurement of the obtained compound, the concentration of active oxygen was quantified as 7 × 10 ¹⁶ cm ⁻³ . From the above, the synthesis of Ca _8.5 La _1.5 (VO ₄ ) ₆ O _{(2 + α)} was confirmed. In addition, it was found that the obtained compound was excellent in heat resistance without any change in structure after the heat resistance test.
[Example 6]
Visible light was irradiated for 15 minutes to 2.00 g of oxyapatite prepared in Examples 4 and 5, respectively. The obtained compound was assigned to a hexagonal apatite structure by XRD, and it was confirmed by IR analysis that there was no OH stretching. From the EPR measurement of the obtained compound, the concentration of active oxygen was quantified as 2 × 10 ¹⁷ cm ⁻³ and 2 × 10 ¹⁸ cm ^{−3, respectively,} and the concentration of active oxygen was increased as compared with Examples 4 and 5. In addition, it was found that the obtained compound was excellent in heat resistance without any change in structure after the heat resistance test.
[Example 7 ]
As a result of conducting a photocatalytic ability test by irradiating visible light (wavelength of 400 nm or more) with the oxyapatite prepared in Example 4,
1251954927853_0
As shown in Fig. 4, it was found that methylene blue was significantly decomposed compared to the blank, and that oxyapatite was extremely excellent in photocatalytic activity.
[Comparative Example 1]
2.00 g CaCO ₃ in (Ltd. Pure Chemical Laboratories) and CaHPO of 3.81 g ₄ (Wako Pure Chemical Industries, Ltd.) ethanol in Ca ₂ P ₂ O ₇ obtained by heating at 800 ° C. Wet mixing was performed to obtain a uniformly mixed sample. The obtained sample was baked at 1400 ° C. for 6 hours in an atmosphere having a water vapor partial pressure of about 10 ³ kPa. The obtained compound could be assigned to the hexagonal apatite structure by XRD. From the IR analysis, OH stretching was observed, and it was considered that hydroxyapatite was formed. From the above, the synthesis of Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ was confirmed. From the EPR measurement of the obtained compound, an absorption band attributable to active oxygen radicals was not observed. Further, after the heat resistance test of the obtained compound, the structure is not maintained and thermal stability is applied.

[Comparative Example 2]
2.00 g CaCO ₃ in (Ltd. Pure Chemical Laboratories) and 7.61 g CaHPO ₄ (Wako Pure Chemical Industries, Ltd.) and Ca ₂ P ₂ O ₇ and 3.25g of obtained by heating at 800 ° C. the la ₂ O ₃ ((Ltd.) pure chemical Laboratories) was wet-mixed in ethanol, to obtain a uniform mixed sample. The obtained sample was baked at 1400 ° C. for 6 hours in an atmosphere having a water vapor partial pressure of about 10 ³ kPa. The obtained compound could be assigned to the hexagonal apatite structure by XRD. From the above, the synthesis of La ₂ Ca ₈ (PO ₄ ) ₆ O ₂ was confirmed. From the EPR measurement of the obtained compound, an absorption band attributable to active oxygen radicals was not observed.

[Comparative Example 3]
Pure water 2.00g of _{Ca (NO 3) 2 · 4H} 2 O (( Ltd.) Pure Chemical Laboratories) and 0.81g of _{Y (NO 3) 3 · 6H} 2 O (( Ltd.) Pure Chemical Laboratories) Then, 30% aqueous ammonia was added to adjust the pH to about 10 to obtain a solution A. Meanwhile 0.84g of _{(NH 4) 2 HPO 4 (} ( Ltd.) Pure Chemical Laboratories) was added 30% aqueous ammonia dissolved in pure water and adjusted to about pH = 10 to obtain a solution B by. Both solutions were bubbled with nitrogen gas for 1 hour at room temperature to remove dissolved carbon dioxide gas. Thereafter, with stirring, solution B with decarboxylated gas was added to solution A with decarboxylated gas while adding 30% aqueous ammonia so that the pH was about 10, thereby obtaining a precipitate. The resulting precipitate was 800 ° C. in an air atmosphere of water vapor partial pressure of about 10 ³ kPa, and 1 hour calcination, then the powder after the calcination was formed on the pellet, with a water vapor partial pressure of about 10 ³ kPa in the air Firing was performed at 1250 ° C. for 1 hour. The obtained compound could be assigned to the hexagonal apatite structure by XRD. From the above, the synthesis of Y ₂ Ca ₈ (PO ₄ ) ₆ O ₂ was confirmed. From the EPR measurement of the obtained compound at room temperature, no absorption band attributable to active oxygen radicals was observed.

As described above, the oxyapatite having a photocatalytic action used by the photocatalyst of the present invention itself contains active oxygen, and the generation of active oxygen is short and continuous when irradiated with light. This can occur to increase the concentration of active oxygen, and in addition, oxyapatite has a high adsorption action. Therefore, adsorption of harmful substances, etc. and oxidation and decomposition of adsorbed species can be performed with a single substance. Compared to conventional titanium oxide and hydroxyapatite mixtures, etc., the efficiency of the catalyst and the manufacturing process are extremely excellent. Yes. Therefore, the oxyapatite containing active oxygen of the present invention is very useful as a photocatalyst.

The oxyapatite photocatalytic ability test result of Example 7 .

Claims (8)

Okishiapatai that you want to contain the active oxygen. 2. The oxyapatite containing active oxygen according to claim 1, wherein the oxyapatite containing active oxygen has a photoactive point . The oxyapatite containing active oxygen according to claim 1 or 2, wherein the oxyapatite containing active oxygen is represented by the following general formula (1).
M1 _a M2 _b (M3O ₄ ) ₆ XY (1)
(In the formula, M1 represents at least one element of Ca, Mg, Sr, Ba, Sn, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pb, Cd, and Ag, and M2 represents Sc. , Y, La, Sb, Bi, Eu, Nd, Al, Ga, In, and M3 represents P, Si, Mn, As, Cr, V, Ge, B, W, Represents at least one element of Mo, a + b = 10, 0.1 ≦ b ≦ 2.0, X represents at least one active oxygen of O ⁻ , O ₂ ⁻ , and O ₃ ⁻ , Y compensates for the charge of oxyapatite other than X, and O ²⁻ , O ₂ ²⁻ , OH ⁻ , F ⁻ , Cl ⁻ , I ⁻ , Br ⁻ , S ²⁻ , NCN ²⁻ , CO ^{_{3 2-, SO 4 2-, NO}} 2 2-, H -, e - represented by, Oki only X When the charge of the apatite is compensated, Y may not.) Y in the general formula (1) is O ^2- The oxyapatite containing active oxygen according to claim 3. Oxyapatite represented by the following general formula, heating temperature 50 ° C. or higher 1800 ° C. or less, the activity according to claim 4, characterized in that it is obtained by treatment with the following dry Kiri囲gas water vapor partial pressure 10 2 ^Pa A method for producing oxygen-containing oxyapatite.
M1 _a M2 _b (M3O ₄ ) ₆ Y
(M1 in the formula represents at least one element of Ca, Mg, Sr, Ba, Sn, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pb, Cd, and Ag,
M2 represents at least one element of Sc, Y, La, Sb, Bi, Eu, Nd, Al, Ga, In,
M3 represents at least one element of P, Si, Mn, As, Cr, V, Ge, B, W, and Mo.
a + b = 10, 0.1 ≦ b ≦ 2.0.
Y represents O ²⁻ . ) The method for producing oxyapatite containing active oxygen according to claim 4 , wherein oxides, hydroxides, carbonates, and chlorides of each element of M1, M2, and M3 in the general formula (1) , A compound selected from fluoride, nitrate, sulfate, and alkoxy at a composition ratio satisfying a + b = 10, 0.1 ≦ b ≦ 2.0, a heating temperature of 50 ° C. to 1800 ° C., and a water vapor partial pressure of 10 ² Pa or less The method for producing oxyapatite containing active oxygen according to claim 4, wherein the oxyapatite is obtained by reacting with an acid. A method for producing active oxygen-containing oxyapatite, comprising the step of further irradiating light to the method for producing active oxygen-containing oxyapatite according to claim 5 or 6.   The photocatalyst which consists of oxyapatite containing the active oxygen in any one of Claims 1-4.

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