JP7464963B2 - Visible light responsive titanium oxide supporting material, method for decomposing organic matter, and method for producing visible light responsive titanium oxide supporting material - Google Patents

Description

The present invention relates to a visible light responsive titanium oxide-supported material, a method for decomposing organic matter, and a method for producing a visible light responsive titanium oxide-supported material.

Conventionally, air and water purification materials using charcoal, activated carbon, etc. have been used, but there is a problem that the air and water purification ability of charcoal and activated carbon drops rapidly when the adsorption saturation is reached. Therefore, air and water purification materials that support photocatalysts such as titanium oxide have been proposed.

However, photocatalysts such as titanium oxide only exhibit photocatalytic activity, such as the oxidative decomposition of organic matter, when exposed to ultraviolet light, which means they are inefficient.

In recent years, therefore, visible light responsive titanium oxide has been developed. Non-Patent Document 1 discloses a method for producing visible light responsive titanium oxide-supported activated carbon by mixing titanium (IV) n-butoxide in a required liquid, adding triethylamine as a nitrogen source and stirring to form a titanium oxide suspension, and then adding activated carbon and stirring, filtering, vacuum drying, and calcining the suspension, as shown in Figure 6.

Wei Zhang et al., Chemical Engineering Journal 168(2011)485-492.

However, the method of Non-Patent Document 1 has problems in that the operation is relatively complicated and the raw material titanium (IV) n-butoxide is expensive. In addition, there is a problem that the method is not suitable for using light because titanium oxide gets into the pores (e.g., micropores and mesopores) of the activated carbon, which are difficult for light to reach. Furthermore, titanium oxide that is not adsorbed because it does not enter the pores of the activated carbon cannot be supported by the activated carbon and remains in the solution and is discarded in the filtration process. In addition, although activated carbon can adsorb large amounts of organic matter by increasing its specific surface area due to its pores, etc., the method of Non-Patent Document 1 has a problem in that titanium oxide is already supported in the pores of the activated carbon, reducing the specific surface area, making it difficult to adsorb large amounts of organic matter to be decomposed on the activated carbon.

The present invention has been made in consideration of the above circumstances, and aims to provide a visible light responsive titanium oxide-supported material that has excellent organic matter retention and resolution capabilities. In addition, the present invention aims to provide a method for producing the visible light responsive titanium oxide-supported material in a simpler process.

The present invention includes the following aspects.
[1] A visible light responsive titanium oxide supporting material, in which visible light responsive titanium oxide fine particles are supported on the surface of a support, the support having either micropores or mesopores or both, and the visible light responsive titanium oxide fine particles are supported on the surface of the support in an area that does not correspond to either the micropores or the mesopores.
[2] The visible light responsive titanium oxide supporting material according to [1], wherein the particle diameter of the visible light responsive titanium oxide fine particles is larger than the inner diameter of the micropores and mesopores.
[3] The visible light responsive titanium oxide-supporting material according to [1] or [2], wherein the support is a carbon material.
[4] The visible light responsive titanium oxide supporting material according to [3], wherein the carbon material is derived from cedar sawdust.
[5] The visible light responsive titanium oxide support material according to any one of [1] to [4], wherein the visible light responsive titanium oxide fine particles are titanium oxide fine particles doped with a nonmetallic element.
[6] The visible light responsive titanium oxide-supporting material according to [5], wherein the nonmetallic element is nitrogen or sulfur.
[7] A method for decomposing an organic matter, comprising carrying an organic matter on the visible light responsive titanium oxide supporting material according to any one of [1] to [6] and irradiating the organic matter with visible light to decompose the organic matter.

[8] A method for producing a visible light responsive titanium oxide support material, comprising: a supporting step of supporting visible light responsive titanium oxide microparticles on a support raw material; and a heat treatment step of the support raw material on which the visible light responsive titanium oxide microparticles are supported in the supporting step.
[9] The manufacturing method according to [8], wherein the supporting step is carried out by putting the support raw material and the visible light responsive titanium oxide fine particles into a ball mill device.
[10] The method according to [8] or [9], wherein the carrier raw material is a carbon precursor.
[11] The method according to [10], wherein the carbon precursor is cedar sawdust.
[12] The method according to any one of [8] to [11], further comprising a doping step, prior to the supporting step, of doping titanium oxide fine particles with a nonmetallic element to obtain the visible light responsive titanium oxide fine particles.
[13] The method according to [12], wherein the doping step is carried out by putting titanium oxide fine particles and a nonmetallic element or a compound containing a nonmetallic element into a ball mill.
[14] The manufacturing method according to [13], wherein the nonmetallic element is nitrogen or sulfur.
[15] The method according to any one of [12] to [14], wherein the visible light responsive titanium oxide microparticles are heat-treated at a temperature of less than 400° C. or are not heat-treated between the doping step and the supporting step.
[16] A visible light responsive titanium oxide-supporting material produced by the method according to any one of [8] to [15].

The present invention can provide a visible light responsive titanium oxide-supported material that has excellent organic matter retention and resolution capabilities. The present invention can also provide a method for producing the visible light responsive titanium oxide-supported material in a simpler process.

FIG. 1 is a schematic diagram showing a visible light responsive titanium oxide supporting material according to this embodiment. FIG. 2 is a schematic diagram showing a method for producing a visible light responsive titanium oxide-supported material according to this embodiment. FIG. 3 is a schematic diagram showing the organic matter decomposition method according to the present embodiment. 4A and 4B are photographs of the visible light responsive titanium oxide supporting material according to this embodiment, observed with a scanning electron microscope (SEM). (a) is a photograph at a magnification of 1000 times, and (b) is a photograph at a magnification of 20000 times. FIG. 5 is a graph showing the results of a methylene blue decomposition test carried out using the visible light responsive titanium oxide supporting material according to this embodiment. FIG. 6 is a schematic diagram showing a conventional method for producing visible light responsive titanium oxide-supported activated carbon.

[Visible light responsive titanium oxide supporting material]
The visible light responsive titanium oxide supporting material according to this embodiment will be described below. Note that the drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand, and the shapes and dimensional ratios of each component element may not necessarily be the same as in reality.

Figure 1 is a schematic diagram showing a visible light responsive titanium oxide-supported material 1 according to this embodiment.

In the visible light responsive titanium oxide support material 1, visible light responsive titanium oxide fine particles 2 are supported on the surface of a support 3', the support 3' having either or both micropores and mesopores (hereinafter sometimes referred to as micropores, etc. 31), and the visible light responsive titanium oxide fine particles 2 are supported on the surface of the support 3' in an area that does not correspond to either the micropores or the mesopores.

In this specification, "micropore" refers to a pore with an inner diameter of more than 0 nm and less than 2 nm, and "mesopore" refers to a pore with an inner diameter of 2 nm or more and 50 nm or less.

The carrier 3' has micropores 31. The micropores 31 can efficiently hold the organic matter 4 to be decomposed. The organic matter 4 may be held in the micropores 31 in any form, but specifically, for example, the organic matter 4 may be adsorbed to the micropores 31, or the organic matter 4 may be bound to the micropores 31.

It is preferable that the visible light responsive titanium oxide microparticles 2 are not supported in the micropores 31 of the carrier 3'. This allows more organic matter 4 to be held in the micropores 31.

The visible light responsive titanium oxide particles 2 are supported on the surface of the carrier 3' in an area that does not correspond to either the micropores or the mesopores. This allows light to be used more efficiently than when the visible light responsive titanium oxide particles 2 are inserted into the micropores 31, etc.

The amount of visible light responsive titanium oxide microparticles 2 supported in the visible light responsive titanium oxide support material 1 is preferably 10.0 to 25.0 mass %, more preferably 12.0 to 22.0 mass %, and even more preferably 15.0 to 20.0 mass %, based on the amount of the visible light responsive titanium oxide support material 1.

By setting the amount of visible light responsive titanium oxide microparticles 2 carried in the visible light responsive titanium oxide support material 1 to be equal to or greater than the above lower limit, the organic matter decomposition ability can be further improved. In addition, by setting the amount of visible light responsive titanium oxide microparticles 2 carried in the visible light responsive titanium oxide support material 1 to be equal to or less than the above upper limit, the organic matter decomposition ability can be further improved and the amount of organic matter retained can be further improved.

The visible light responsive titanium oxide microparticles 2 may be directly supported on the carrier 3', or may be indirectly supported on the carrier 3' via another substance or a linker.

From the viewpoint of producing the visible light responsive titanium oxide supporting material 1 in a simpler process, it is preferable that the visible light responsive titanium oxide microparticles 2 are directly supported on the support 3'.

The visible light responsive titanium oxide microparticles 2 may be supported on the carrier 3' in any manner, including, for example, embedding, welding, adsorption, covalent bonding, ionic bonding, metallic bonding, and bonding by intermolecular forces.

An example of a case in which the visible light responsive titanium oxide microparticles 2 are directly supported on the carrier 3' is a case in which the carrier 3' has macropores 32 on the surface of an area that does not correspond to either the micropores or the mesopores, and the visible light responsive titanium oxide microparticles 2 are embedded in the macropores 32.

In this specification, "macropore" refers to a pore with an inner diameter of more than 50 nm.

The total volume of the micropores and mesopores formed in the carrier 3' is preferably 0.01 to 0.70 cm ³ /g, more preferably 0.02 to 0.50 cm ³ /g, and even more preferably 0.05 to 0.40 cm ³ /g, per unit mass of the visible light responsive titanium oxide supporting material 1.

It is preferable that the particle diameter of the visible light responsive titanium oxide microparticles 2 supported on the surface of the carrier 3' is larger than the inner diameter of the micropores 31 (in other words, the inner diameter of the micropores 31 is smaller than the particle diameter of the visible light responsive titanium oxide microparticles 2 supported on the surface of the carrier 3'). By having the particle diameter of the visible light responsive titanium oxide microparticles 2 larger than the inner diameter of the micropores 31, the visible light responsive titanium oxide microparticles 2 do not enter the micropores 31, and more organic matter 4 can be retained in the micropores 31.

Specifically, the average particle diameter of the visible light responsive titanium oxide microparticles 2 is, for example, preferably greater than 50 nm and equal to or less than 5000 nm, more preferably equal to or greater than 60 nm and equal to or less than 1000 nm, and even more preferably equal to or greater than 70 nm and equal to or less than 500 nm.

When the average particle diameter of the visible light responsive titanium oxide microparticles 2 is equal to or greater than the above lower limit, the visible light responsive titanium oxide microparticles 2 do not enter the micropores 31, and more organic matter 4 can be retained in the micropores 31. On the other hand, when the average particle diameter of the visible light responsive titanium oxide microparticles 2 is equal to or less than the above upper limit, the efficiency of decomposing organic matter can be further improved.

The carrier 3' is preferably a material derived from the carrier raw material 3. A material derived from the carrier raw material 3 refers to a processed product obtained by performing some kind of chemical treatment on the carrier raw material 3. An example of a derived product is a heat-treated product, and an example of a heat-treated product is a fired product.

The carrier 3' may be any material as long as it has micropores 31, but it is preferable that the carrier 3' be a carbon material, alumina, silica, or the like, because it is easy to manufacture the carrier 3' having micropores 31 by heat-treating the carrier raw material (e.g., carrier raw material 3 described below) that is the raw material for manufacturing the carrier 3'.

When the carrier 3' is a carbon material, the carbon precursor used as the carrier raw material 3 is preferably a soft material having cushioning properties. By using a soft material having cushioning properties, the visible light responsive titanium oxide microparticles 2 can be easily supported on the carrier raw material 3 (and thus the carrier 3'). Examples of such carbon precursors include sawdust from wood such as cedar, oak, pine, and cypress, bamboo, and rice husks.

Titanium oxide is a typical example of a so-called "photocatalyst." The principle of photocatalysis is that when a substance is irradiated with light with energy equal to or greater than its band gap, charge separation occurs, and the resulting electrons and holes cause an oxidation/reduction reaction on the solid surface, which can decompose organic matter, etc.

Specific examples of visible light responsive titanium oxide microparticles 2 include titanium oxide microparticles 21 doped with iron, titanium oxide microparticles 21 doped with a nonmetallic element 22, etc.

The titanium oxide microparticles 21 themselves have a large band gap and only respond to ultraviolet light, but by doping them with iron or a nonmetallic element 22, new energy levels can be generated and the band structure can be changed, forming visible light responsive titanium oxide microparticles 2 that absorb in the visible light region. This can improve the utilization rate of light, such as solar energy.

Specific examples of the nonmetallic element 22 for reducing the band gap of the titanium oxide microparticles 21 include nitrogen doping, sulfur doping, co-doping with iodine and nitrogen, and co-doping with fluorine and nitrogen, among which nitrogen doping is preferred. When the oxygen sites of the titanium oxide microparticles 21 are replaced with nitrogen or sulfur, yellow titanium oxide microparticles are obtained, the band gap is reduced, and photocatalytic activity is exhibited when irradiated with visible light.

The specific surface area of the visible light responsive titanium oxide supporting material 1 is preferably 10 to 1000 m ² /g, more preferably 50 to 800 m ² /g, and further preferably 100 to 700 m ² /g.

By having the specific surface area of the visible light responsive titanium oxide supporting material 1 within the above range, the organic matter retention ability can be further improved. The specific surface area can be determined by the BET method.

[Method of producing visible light responsive titanium oxide supporting material]
Next, a description will be given of a method for producing the visible light responsive titanium oxide supporting material 1. FIG.

(Doping process)
2(a) and 2(b) is preferably carried out in the method for producing the visible light responsive titanium oxide support material 1. In the doping step, titanium oxide fine particles 21 are doped with a nonmetallic element 22 to obtain visible light responsive titanium oxide fine particles 2.

The doping process is preferably carried out by putting titanium oxide fine particles 21 and a nonmetallic element 22 or a compound containing a nonmetallic element 22 into a ball mill device.

The rotation speed of the ball mill device in the doping process is not particularly limited, but is preferably 100 to 800 rpm, more preferably 200 to 700 rpm, and even more preferably 300 to 600 rpm. In addition, the rotation time of the ball mill device in the doping process is preferably 0.1 to 5 hours, more preferably 0.3 to 4 hours, and even more preferably 0.5 to 3 hours.

By setting the rotation speed and rotation time of the ball mill device in the doping process to be equal to or greater than the above lower limit, a sufficient amount of nonmetallic element 22 can be doped into the titanium oxide microparticles 21. On the other hand, by setting the rotation speed of the ball mill device in the doping process to be equal to or less than the above upper limit, it is possible to further prevent the particle diameter of the titanium oxide microparticles 21 from becoming excessively small.

The mass of each ball and the number of balls used are not particularly limited, but for example, when a 250 cc ball mill container (pot) is used, the mass of each ball used in the ball mill device in the doping process is preferably 1 to 3 g. In addition, the number of balls used in the ball mill device in the doping process is preferably 40 to 60. The material of the balls and ball mill container (pot) is not particularly limited, but for example, alumina, stainless steel, zirconia, etc. can be used.

When using a nonmetallic element 22 in the doping process, the amounts of titanium oxide microparticles 21 and nonmetallic element 22 used are not particularly limited and may be set according to the desired doping amount, but it is preferable to use 0.1 to 20 parts by mass of nonmetallic element 22 per 100 parts by mass of titanium oxide microparticles 21, more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 5 parts by mass.

When a compound containing a nonmetallic element 22 is used in the doping process, the amounts of titanium oxide microparticles 21 and the compound containing a nonmetallic element 22 used are not particularly limited and may be set according to the desired doping amount, but it is preferable to use the compound containing a nonmetallic element 22 so that the amount of nonmetallic element 22 contained in the compound is 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, per 100 parts by mass of titanium oxide microparticles 21.

Specifically, the average particle size of the titanium oxide microparticles 21 fed into the ball mill is preferably, for example, greater than 50 nm and less than 5000 nm, more preferably 60 nm or more and 1000 nm or less, and even more preferably 70 nm or more and 500 nm or less.

The nonmetallic element 22 is preferably nitrogen or sulfur, and more preferably nitrogen.

When the nonmetallic element 22 is nitrogen, the doping process is preferably carried out by putting the titanium oxide fine particles 21 and a nitrogen-containing compound into a ball mill. A nitrogen-containing compound is a compound that has a nitrogen atom as a constituent atom, and specific examples thereof include ammonia, urea, ammonium carbonate, triethylamine, etc.

When the nonmetallic element 22 is sulfur, the doping process is preferably carried out by putting titanium oxide fine particles 21 and sulfur or a sulfur-containing compound into a ball mill. A sulfur-containing compound is a compound that has a sulfur atom as a constituent atom.

(Supporting process)
In the method for producing the visible light responsive titanium oxide supporting material 1, a supporting step shown in Fig. 2(b) and (c) is carried out. In the supporting step, the visible light responsive titanium oxide fine particles 2 are supported on the support raw material 3.

The carrier raw material 3 may be any material that can be used to produce the carrier 3', but it is preferable to use a carbon precursor, alumina, silica, etc., in that it is easy to form micropores, etc. 31 by heat treatment.

The carbon precursor used as the carrier raw material 3 is preferably a soft material having cushioning properties. By using a soft material having cushioning properties, the visible light responsive titanium oxide microparticles 2 can be easily supported on the carrier raw material 3 (and thus the carrier 3'). Examples of such carbon precursors include sawdust from wood such as cedar, oak, pine, and cypress, bamboo, and rice husks.

The loading step may be carried out by any method, but is preferably carried out by placing the carrier raw material 3 and visible light responsive titanium oxide fine particles 2 in a ball mill device.

The rotation speed of the ball mill device in the loading step is not particularly limited, but is preferably 50 to 500 rpm, more preferably 70 to 400 rpm, and even more preferably 100 to 300 rpm. The rotation time of the ball mill device in the loading step is preferably 5 to 120 minutes, more preferably 10 to 60 minutes, and even more preferably 10 to 30 minutes.

By setting the rotation speed and rotation time of the ball mill device in the loading process to the above lower limit values or more, the visible light responsive titanium oxide microparticles 2 can be firmly loaded onto the carrier raw material 3. On the other hand, by setting the rotation speed of the ball mill device in the loading process to the above upper limit values or less, excessive pulverization of the carrier raw material 3 can be suppressed.

The mass of each ball and the number of balls used are not particularly limited, but for example, when a 250 cc ball mill container (pot) is used, the mass of each ball used in the ball mill device in the loading process is preferably 1 to 3 g. In addition, the number of balls used in the ball mill device in the loading process is preferably 40 to 60. The material of the balls and ball mill container (pot) is not particularly limited, but for example, alumina, stainless steel, zirconia, etc. can be used.

The amounts of visible light responsive titanium oxide microparticles 2 and carrier raw material 3 used in the loading process are not particularly limited and may be set according to the desired amount of visible light responsive titanium oxide microparticles loaded onto carrier 3'. However, from the viewpoint of balancing the amounts used of both, it is preferable to use 100 to 5,000 parts by mass of carrier raw material 3 per 100 parts by mass of visible light responsive titanium oxide microparticles 2, more preferably 200 to 4,000 parts by mass, and even more preferably 300 to 3,000 parts by mass.

(Preliminary heat treatment process)
In the method for producing the visible light responsive titanium oxide supporting material 1, the visible light responsive titanium oxide fine particles 2 may be heat-treated between the doping step and the supporting step, thereby removing the nonmetallic elements 22 that have not been doped into the titanium oxide fine particles 21.

The heating temperature is preferably greater than 0°C and less than 500°C, more preferably 100 to 450°C, and even more preferably 200 to 400°C. The heating time is preferably 0.1 to 5 hours, more preferably 0.2 to 3 hours, and even more preferably 0.5 to 2 hours.

By setting the heating temperature and heating time to the above lower limit values or more, the nonmetallic elements 22 that have not been doped into the titanium oxide microparticles 21 can be removed more efficiently. On the other hand, by setting the temperature and heating time of the heat treatment to the above upper limit values or less, the doped nonmetallic elements 22 can be further prevented from being removed from the titanium oxide microparticles 21.

Between the doping step and the supporting step, the visible light responsive titanium oxide microparticles 2 may or may not be heat-treated as described above, but it is preferable to heat-treat the visible light responsive titanium oxide microparticles 2 at a temperature of less than 400°C or not to heat-treat them.

By heat-treating the visible light responsive titanium oxide microparticles 2 at a temperature below 400°C or not heat-treating them, the organic matter retention and resolution of the visible light responsive titanium oxide supporting material 1 can be further improved.

(Heat treatment process)
2(c) and 2(d) is performed in the manufacturing method of the visible light responsive titanium oxide supporting material 1. In the heat treatment step, the carrier raw material on which the visible light responsive titanium oxide fine particles 2 are supported in the supporting step is heat treated. As a result, the carrier raw material 3 becomes a carrier 3' having micropores 31 formed therein, and the visible light responsive titanium oxide supporting material 1 is formed.

The formation of micropores, etc. 31 in the carrier raw material 3 by heat treatment will be explained using a specific example. For example, when the carrier raw material 3 is a carbon precursor, the carbon precursor is placed in a crucible, covered to prevent air from entering, and heat treated (hereinafter sometimes referred to as calcination). The carbon precursor is thermally decomposed and carbonized, forming micropores, etc. 31 and forming developed charcoal.

When the carrier raw material 3 is a carbon precursor, the calcination temperature is preferably 400 to 1000°C, more preferably 400 to 800°C, and even more preferably 400 to 700°C.

The firing time is preferably 0.1 to 5 hours, more preferably 0.2 to 3 hours, and even more preferably 0.5 to 2 hours.

By setting the firing temperature and firing time to the above lower limit values or more, a sufficient amount of micropores, etc. 31 can be formed in the carrier 3'. On the other hand, by setting the firing temperature and firing time to the above upper limit values or less, it is possible to further suppress the doped nonmetallic elements 22 from being removed from the titanium oxide microparticles 21.

In the visible light responsive titanium oxide support material 1, the visible light responsive titanium oxide fine particles 2 are supported on the carrier raw material 3 in the support process, and then micropores, etc. 31 are formed in the carrier raw material 3 in the heat treatment process to form the carrier 3', so that the visible light responsive titanium oxide fine particles 2 are not supported in the micropores, etc. 31 immediately after the heat treatment process.

Since the visible light responsive titanium oxide microparticles 2 are not supported in the micropores 31, more organic matter 4 can be retained in the micropores 31.

[Method of decomposing organic matter]
The organic matter decomposition method according to the present embodiment will now be described with reference to Fig. 3, which is a schematic diagram showing the organic matter decomposition method according to the present embodiment.

In the method for decomposing organic matter according to this embodiment, organic matter 4 is held on a visible light responsive titanium oxide supporting material 1 and is irradiated with visible light to decompose the organic matter 4.

The organic matter 4 may be held in the micropores 31 of the visible light responsive titanium oxide supporting material 1, or may be held on the surface of an area that does not correspond to either a micropore or a mesopore, but more organic matter 4 can be held in the micropores 31.

The organic matter 4 may be retained in any form on the visible light responsive titanium oxide-supported material 1, but specifically, for example, the organic matter 4 may be adsorbed or bonded to functional groups (e.g., carboxyl groups, phenolic hydroxyl groups, etc.) on the surface of the visible light responsive titanium oxide-supported material 1.

As shown in FIG. 3(a), an organic substance 4 is held on a visible light responsive titanium oxide supporting material 1. Examples of holding methods include placing the visible light responsive titanium oxide supporting material 1 in a space containing gaseous organic substance 4, and adding the visible light responsive titanium oxide supporting material 1 to a solution in which the organic substance 4 is dissolved in a solvent. Examples of solvents for dissolving the organic substance 4 include water, methanol, ethanol, etc.

In the organic matter decomposition method according to this embodiment, the amounts of visible light responsive titanium oxide supporting material 1 and organic matter 4 used are not particularly limited, but from the viewpoint of balancing the amounts used of both, it is preferable to use 0 to 20 parts by mass of organic matter 4 per 100 parts by mass of visible light responsive titanium oxide supporting material 1, more preferably 0 to 10 parts by mass, and even more preferably 0 to 5 parts by mass.

The organic matter 4 may be any organic matter that can be decomposed by the visible light responsive titanium oxide supporting material 1. When evaluating the performance of the visible light responsive titanium oxide supporting material 1, organic matter that is typically used in organic matter decomposition tests using titanium oxide microparticles, such as methylene blue (a blue pigment), methyl orange, rhodamine B, etc., may be used.

Next, as shown in FIG. 3(b), visible light L is irradiated onto the visible light responsive titanium oxide supporting material 1 holding the organic matter 4, generating radical species and active oxygen species (hereinafter sometimes referred to as radical species, etc.) R, which decomposes the organic matter 4.

The wavelength region of visible light L is preferably 350 to 700 nm, more preferably 350 to 600 nm, and even more preferably 350 to 550 nm.

The effects of the present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[Preparation of visible light responsive titanium oxide supporting material]
A visible light responsive titanium oxide supporting material was prepared as follows.

Example 1
[Doping process]
5.4 g of titanium oxide fine particles (anatase type, average particle size 0.3-0.4 μm, Junsei Chemical Co., Ltd.) and 0.6 g of ammonium carbonate were placed in a planetary ball mill (Fritsch, P-6, ball mill pot: made of alumina) loaded with 50 alumina grinding balls, each 10 mm in diameter and 2 g in weight, and rotated at 500 rpm for 2 hours to produce visible light responsive titanium oxide fine particles (average particle size 0.1-0.2 μm) in which the titanium oxide fine particles were doped with nitrogen. The titanium oxide fine particles changed color from white to yellow by the doping process.

[Supporting step]
After the doping step, 25 g of cedar sawdust was put into the device and rotated at 200 rpm for 20 minutes to support the visible light responsive titanium oxide microparticles on the cedar sawdust. The obtained microparticles were sieved to collect microparticles with a particle size of more than 106 μm.

[Firing process]
The fine particles having a particle diameter of more than 106 μm, in which the visible light responsive titanium oxide fine particles were supported on the sawdust obtained in the supporting step, were placed in a crucible, covered with a lid to prevent air from entering, and heated to 400° C. at a rate of 5° C./min. Thereafter, the material was fired (carbonized) at 400° C. for 1 hour to produce a visible light responsive titanium oxide supporting material.

Example 2
The visible light responsive titanium oxide supported material of Example 2 was prepared in the same manner as in Example 1, except that the fine particles with a particle diameter of more than 106 μm, in which visible light responsive titanium oxide fine particles were supported on sawdust obtained in the supporting process, were placed in a crucible, covered with a lid to prevent air from entering, and heated to 700°C at a rate of 5°C/min, and then fired (carbonized) at 700°C for 1 hour.

Figure 4 shows a photograph of the visible light responsive titanium oxide-supported material obtained in Example 2, observed with a scanning electron microscope (SEM) (JSM-6380LANV, manufactured by JEOL Ltd.).

Figure 4(a) shows a scanning electron microscope (SEM) at a magnification of 1000x, which confirms that visible light responsive titanium oxide microparticles are supported in the vessels of the cedar. Figure 4(b) shows a scanning electron microscope (SEM) at a magnification of 20,000x, which confirms that the particle size of the visible light responsive titanium oxide microparticles supported in the vessels of the cedar is approximately 100-200 nm.

Example 3
The visible light responsive titanium oxide microparticles obtained in the doping process were placed in a crucible, covered to prevent air from entering, and heated to 400°C at a rate of 5°C/min., and then heat-treated at 400°C for 1 hour before carrying out the supporting process. Except for this, the visible light responsive titanium oxide supporting material of Example 3 was prepared in the same manner as in Example 1.

[Methylene blue decomposition test]
Methylene blue (Sigma-Aldrich) was dissolved in pure water to prepare a methylene blue solution (50 mL) having a predetermined concentration (Examples 1 and 3: 80 μmol/L, Example 2: 180 μmol/L).

To this methylene blue solution, 0.1 g of the visible light responsive titanium oxide-supported material of Examples 1 to 3 was added, and the mixture was stirred in a dark room at 20° C. for 20 to 24 hours while blowing in air (100 mL/min), until the concentration of the methylene blue solution reached equilibrium, becoming approximately 10 μmol/L (=C ₀ ). The concentration of the methylene blue solution was measured by a method for measuring absorbance at a wavelength of 664 nm.

The methylene blue solution was irradiated with visible light (350-700 nm, central wavelength 450 nm) under irradiation conditions of 100,000 lux by irradiating it with light from a filtered LED lamp, and the concentration of the methylene blue solution (= C [μmol/L]) was measured again over time.

The graph obtained, with the vertical axis representing C/ _C0 and the horizontal axis representing time (min), is shown in Figure 5. Note that "blank" indicates the case where the above methylene blue decomposition test was carried out without adding the visible light responsive titanium oxide supporting material.

As shown in Figure 5, methylene blue was hardly decomposed when the visible light responsive titanium oxide support material was not added. In contrast, it was confirmed that methylene blue was efficiently decomposed when the visible light responsive titanium oxide support material of Examples 1 to 3 was added.

Furthermore, it was confirmed that when the visible light responsive titanium oxide microparticles were not heat-treated between the doping process and the supporting process (Examples 1 and 2), they had better organic matter retention and decomposition capabilities than when they were heat-treated at 400°C (Example 3).

As described above, the visible light responsive titanium oxide-supported material of the present invention has excellent organic matter retention and resolution capabilities. Furthermore, the method for producing a visible light responsive titanium oxide-supported material of the present invention can produce the visible light responsive titanium oxide-supported material in a simpler process.

The visible light responsive titanium oxide-supported material of the present invention can be suitably used as an air and water purifier, deodorizer, water purifier material, etc.

Reference Signs List 1: Visible light responsive titanium oxide support material 2: Visible light responsive titanium oxide fine particles 21: Titanium oxide fine particles 22: Non-metallic element 3: Carrier raw material 3': Carrier 31: Micropores, etc. 32: Macropores 4: Organic matter L: Visible light R: Radical species, etc.

Claims (12)

Visible light responsive titanium oxide fine particles are supported on the surface of the carrier,
The support has either or both of micropores and mesopores,
the visible light responsive titanium oxide fine particles are embedded in the surface of the carrier in a region that does not correspond to either the micropores or the mesopores,
The support is a carbon material,
The visible light responsive titanium oxide fine particles have an average particle diameter of more than 50 nm and not more than 5,000 nm . The visible light responsive titanium oxide supporting material according to claim 1, wherein the inner diameter of the micropores and mesopores is smaller than the particle diameter of the visible light responsive titanium oxide fine particles supported on the surface of the support. The visible light responsive titanium oxide supporting material according to claim 1, wherein the carbon material is derived from cedar sawdust. The visible light responsive titanium oxide support material according to any one of claims 1 to 3, wherein the visible light responsive titanium oxide fine particles are titanium oxide fine particles doped with a nonmetallic element. The visible light responsive titanium oxide support material according to claim 4, wherein the nonmetallic element is nitrogen or sulfur. A method for decomposing organic matter, comprising carrying an organic matter on the visible light responsive titanium oxide carrying material according to any one of claims 1 to 5, irradiating the organic matter with visible light, and decomposing the organic matter. a supporting step of supporting visible light responsive titanium oxide fine particles on a support material;
a step of heat-treating the carrier raw material on which the visible light responsive titanium oxide fine particles have been supported in the supporting step;
A method for producing a visible light responsive titanium oxide-supporting material comprising the steps of:
The supporting step is carried out by putting the support raw material and the visible light responsive titanium oxide fine particles into a ball mill device,
The method for producing a visible light responsive titanium oxide supporting material, wherein the support raw material is a carbon precursor. The method of claim 7, wherein the carbon precursor is cedar sawdust. The method according to claim 7 or 8, further comprising a doping step of doping titanium oxide fine particles with a nonmetallic element to obtain the visible light responsive titanium oxide fine particles, prior to the supporting step. The manufacturing method according to claim 9, wherein the doping step is carried out by putting titanium oxide fine particles and a nonmetallic element or a compound containing a nonmetallic element into a ball mill device. The manufacturing method according to claim 10, wherein the nonmetallic element is nitrogen or sulfur. The method according to any one of claims 9 to 11, wherein the visible light responsive titanium oxide fine particles are heat-treated at a temperature of less than 400°C between the doping step and the supporting step, or are not heat-treated.

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