JP2006223919A - Functional powder and structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a drawback in which a photocatalytic material is expensive since titanium is a main raw material though in a TiO<SB>2</SB>photocatalyst, a wide development study is carried out, practical use progresses and also a new material exhibiting a photocatalytic function without irradiating an ultraviolet ray is proposed from its excellent effect of environmental improvement and conservation. <P>SOLUTION: It was found that an iron oxide a large amount of which is included in slag inevitably generated in ordinary steel production as a by-product is a metal deficiency oxide having a composition of Fe<SB>X</SB>O(X<1) and p-type semiconductor character. Further, it was confirmed to include a photocatalytic effect without irradiating the ultraviolet ray. An inexpensive material is obtained which has the photocatalytic function without irradiating the ultraviolet ray. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to the discovery that iron oxide inevitably contained in electric furnace slag, converter slag, and hot rolling scale is a metal-deficient non-stoichiometric oxide having p-type semiconductor characteristics, and its effective utilization. .

  Reactions generated by light energy are classified as shown in (Table 1).

About 30 years ago, a photocatalytic reaction capable of photodegrading water using a ceramic semiconductor (rutile-type titanium dioxide) as a photoelectrode was discovered in Japan, and as a result, development research on the photocatalytic reaction was actively started. .

Since then, extensive research and development has been promoted, and the practical application of photocatalytic reactions using white fine powder of titanium dioxide (anatase type, large specific surface area), which is mass-produced and marketed, is mainly applied to the structure. .

The target photocatalyst is required to be irradiated with ultraviolet rays, and development research on practical application of anatase-type titanium dioxide and TiO ₂ having a photocatalytic function has been actively promoted.

Examples of application development utilizing the functions of anatase-type titanium dioxide and TiO ₂ already in practical use are shown in (Table 2).

The photocatalyst, TiO _2, is said to exhibit its function as a semiconductor only when it receives and excites energy corresponding to its band gap energy of 3.2 eV from ultraviolet light having a wavelength of 380 nm.

When energy from ultraviolet rays is received, electrons in the valence band are excited and move to the conduction band. Holes are formed in the traces where electrons have escaped. It is explained that the strong oxidation function of hydroxyl radical (.OH) generated by depriving electrons of H ₂ O in contact with holes is the function of the photocatalyst itself.

The oxidizing power of hydroxyl radicals is determined by the C—C, C—H, C—N, C—O, O—H, and N—H in the molecules that make up inorganic and organic substances such as chemical substances that cause environmental pollution. These bonds can be broken and broken because they are much larger than the bond energy.

Therefore, it is possible to clean the chemical substances and the like that cause environmental pollution with a strong oxidizing power cleanly by irradiation with ultraviolet rays, which can be an effective means for environmental purification. The biggest feature is that the reaction proceeds permanently without being consumed or changing its properties. It should be noted that the concentration of hydroxyl radicals produced is extremely small under the amount of ultraviolet rays present in the living space, which is completely harmless to the human body.

However, it seems that the limitation of this technology exists in that hydroxyl radicals are generated only after receiving ultraviolet rays. Research and development has been started to break this technical limit.

In the present invention, the present inventors have already proposed a photocatalyst capable of generating hydroxyl radicals without irradiation with ultraviolet rays. However, in view of the disadvantage that it is expensive and difficult to be widely used in the world, it is extremely inexpensive and the same. It is a new proposal of a new functional body based on a novel discovery having a function.
Japanese Patent Application No. 2004-227533 JP 2002-316056 PR The Chemical Society of Japan "Catalyst Chemistry Involving Light" (1994) Hashimoto, Kobayakawa “Photocatalyst and Semiconductor Electrode” (CMC Publishing) Kominato "Chemistry of non-stoichiometric compounds" (Baifukan) N A Trobov et al. “Metallic oxide phase diagram” (published by Nisso News Agency)

The process in which the photocatalyst performs its function is as follows.
(1) Irradiation of the photocatalyst with ultraviolet rays (2) Electrons in the valence band move to the conduction band.
(3) Holes are generated where the electrons in the charged band are missing.
(4) Water molecules adsorb to the holes.
(5) Water molecules are deprived of electrons and decomposed into hydrogen ions and hydroxyl radicals.
(6) The generated hydroxyl radical decomposes organic matter and the like.

  The feature of the photocatalyst is that “holes are generated only by UV irradiation”. In other words, he filed an application for "providing a photocatalyst that generates holes even without UV irradiation" or "providing a semiconductor in which holes exist in advance".

  However, since the synthesis is expensive, a “semiconductor in which holes exist in advance” having the same function is the subject of this patent.

1) The basic concept of the present invention “ultraviolet irradiation → hole generation” is a mechanism by which a conventional photocatalyst exerts its function. The present invention provides “a p-type semiconductor having holes in advance”. “A p-type semiconductor having holes in advance” is expected to have a function equivalent to that of a conventional photocatalyst without irradiation with ultraviolet rays.

  That is, when water molecules contained as a gas are contacted and adsorbed to the extent that they are indicated by the dew point of water or a gas body of any kind, on the “p-type semiconductor that holds holes in advance”, the holes become water. Takes electrons from the molecule and generates hydroxyl radicals (.OH). The function of this hydroxyl radical is as described above. The catalytic function expressed by this mechanism does not require any ultraviolet irradiation. The present invention provides a novel catalyst characterized in that “holes” that generate hydroxyl radicals (.OH) by reaction with moisture are retained in advance.

2) Specific means of the present invention The crystals of transition metal stoichiometric oxide and stoichiometric nitride are electrically neutral. This principle is the fundamental idea of the proposal of the present invention.

It is well known that transition metals constitute non-stoichiometric compounds because each atom constitutes multiple valence states. Typical examples are nonstoichiometric oxides and nonstoichiometric nitrides.

Nonstoichiometric oxides and nonstoichiometric nitrides are further classified into metal-rich and metal-deficient types.

Among these, in the metal-deficient non-stoichiometric oxides and nitrides, the holes corresponding to the deficient metal atoms (+ charges) are contained in the valence crystal in order to maintain electrical neutrality at the same time as the generation. It is formed.

In other words, both the metal-deficient non-stoichiometric oxide and the metal-deficient non-stoichiometric nitride are p-type semiconductors that hold holes in advance.

  In the present invention, a metal-deficient transition metal non-stoichiometric oxide or a metal-deficient transition metal non-stoichiometric nitride in which holes are formed in advance is used as a “catalyst that exhibits a photocatalytic function without ultraviolet irradiation”. It is to propose.

  Various technical studies on crystallographic elucidation of transition metal oxides have been conducted. However, despite the technical efforts, it is difficult to say that the details have been completely elucidated.

  However, crystallographic discussion is not necessary in the present invention. The stoichiometric oxide and stoichiometric nitride of transition metals that are electrically neutral are logically set and specified, and the metal-deficient non-stoichiometric oxide and non-stoichiometric ratio for the specified stoichiometric compound are specified. It is the gist of the present invention to propose the setting of nitride.

  The results of the investigation of the transition metal-oxygen binary system based on the research results of many researchers are summarized in Table 3 according to the gist of the present invention.

When the compound showing electrical neutrality is TiO, X = 1 means a stoichiometric oxide. When X <1, it becomes a metal-rich non-stoichiometric oxide, and e ⁻ is generated that balances + electrons of excess metal to form an n-type (−) semiconductor.

  When X> 1, a metal-deficient type, that is, an oxygen-excess type non-stoichiometric oxide is formed. A “hole” is generated that balances the negative electrons of excess oxygen, thereby forming a p-type (+) semiconductor.

  In the semiconductor type column of (Table 3), all the semiconductors marked with a circle in the p (+) type semiconductor column, that is, metal-deficient semiconductors, are proposed in the present invention as “p in which holes are present in advance”. Belongs to the category of "type semiconductors". That is, all of these semiconductors are included in the present invention.

  However, in order to be widely used in the world, it is necessary to obtain a metal-deficient non-stoichiometric oxide having p-type semiconductor characteristics at a low cost.

As a result of searching various low-priced compounds that are metal-deficient non-stoichiometric oxides having p-type semiconductor characteristics, iron oxides contained in large amounts in steelmaking slag are Fe _X O (X < It has been discovered that the metal-excess type oxide having the composition 1) has p-type semiconductor characteristics and exhibits a photocatalytic effect without irradiation with ultraviolet rays. This is a very significant discovery. I would like to explain the effect in detail below.

The metal-deficient non-stoichiometric oxide proposed in the present invention, Fe _X O (X <1), is present in a large amount in steelmaking slag. Conventional photocatalysts are mainly composed of titanium oxide, and the price for photocatalyst use is 2000 yen or more per kilogram.

  With the proposal of the present invention, the range of material selection according to applications such as cheaper applications is widened, and the photocatalytic effect can be enjoyed in various places in the living environment.

In Fe _X O (X <1) proposed by the present invention, excessive “holes” are generated in advance. Therefore, when a temperature gradient is applied to these, a small amount of power generation function due to the Seebeck effect is exhibited. Since this power generation function exhibits an effect of improving blood circulation in the body, the metal-deficient non-stoichiometric oxide or the metal-deficient non-stoichiometric nitride of the present invention is also valuable for use as a body function preservation product.

Fe _X O (X <1) obtained in a powder form from steelmaking slag is made as fine as possible and used as follows.
(1) Use as powder.
(2) Use by mixing powder in a solvent.
(3) Used by coating the surface layer of a structure such as ceramics.
(4) Use as a fired product in which powder is mixed with other ceramics.
(5) Used by sintering only powder.

  When using the powder as it is, it is used by mixing it with all fibers. Various fiber products having a photocatalytic effect can be manufactured at low cost. It can be effectively used for hospitals, nursing facilities for the elderly, hotels, sheets for the Shinkansen, etc.

A typical usage when the powder is mixed with a solvent is a use as a spray.
It can be used effectively for various deodorizing, antifouling and antibacterial areas such as inner and outer walls, curtains, floors and kitchens.

  Used on ceramics, plastic, glass, wood and various metals. Applications range widely, for example, coated plastic spheres can be effectively used for sterilization of water absorption towers and purification of feed water.

It can be used after being kneaded in a ceramic or the like and fired, or coated on the surface and fired.

As it is, it can be used as a p-type semiconductor.

Table 5 summarizes the results of functional evaluation of the example samples of the present invention.

Examples 1 and 2 are metal-deficient non-stoichiometric iron oxide Fe _0.94 O extracted from special steel-made steel slag. Comparative Material 1-2 is a conventional photocatalyst TiO _2.

  The decomposition function of acetaldehyde with the elapsed time by these examples and comparative samples was measured under the condition of presence or absence of black light.

  The outline of the method for evaluating the photocatalytic function and the method for measuring the amount of acetaldehyde in the examples of the present invention is shown in Table 6.

Comparative materials 1 and 2 are conventional photocatalysts. Although the acetaldehyde is satisfactorily decomposed in the environment of the black lamp irradiation, the acetaldehyde is hardly decomposed in the environment without the black lamp irradiation.

  In the metal-deficient non-stoichiometric oxides and non-stoichiometric nitrides provided by the present invention in Examples 1 to 6, the decomposition of acetaldehyde proceeds efficiently regardless of the presence or absence of a black lamp.

    At the time of FeXO (X <1) non-stoichiometric oxide formation, the hydroxyl radical (• OH) generated by the oxidative decomposition of the water component adsorbed on the crystal by the pre-generated holes in the crystal decomposes acetaldehyde. This is because.

  Since the non-stoichiometric oxide provided by the present invention, holes are generated in advance, inorganic and organic substances can be decomposed by hydroxyl radical (.OH) without irradiation of a black lamp.

Practical use is being promoted for various applications utilizing the function (Table 1), but since the irradiation with ultraviolet rays is an essential condition for the function, practical use is delayed.

Since the proposal of the present invention eliminates the need for ultraviolet irradiation, it is not necessary to say that the practical application for the applications shown in (Table 1) will be actively promoted. In particular, application development will become increasingly active as a material for environmental improvement and environmental conservation.

However, since functional materials having a photocatalytic function are expensive, there is a drawback that they cannot be widely used.

It has been found that FeXO (X <1) having a photocatalytic function is present in steelmaking slag without ultraviolet irradiation, and the photocatalytic effect can be widely used. Therefore, the effect of the present invention is great.

The present invention relates to the discovery that iron oxide inevitably contained in electric furnace slag, converter slag, and hot rolling scale is a metal-deficient non-stoichiometric oxide having p-type semiconductor characteristics, and its effective utilization. .

About 30 years ago, a photocatalytic reaction capable of photodegrading water using a ceramic semiconductor (rutile-type titanium dioxide) as a photoelectrode was discovered in Japan, and as a result, development research on the photocatalytic reaction was actively started. .

Since then, extensive research and development has been promoted, and the practical application of photocatalytic reactions using white fine powder of titanium dioxide (anatase type, large specific surface area), which is mass-produced and marketed, is mainly applied to the structure. .

The target photocatalyst is required to be irradiated with ultraviolet rays, and development research on practical application of anatase-type titanium dioxide and TiO ₂ having a photocatalytic function has been actively promoted.

Examples of application development utilizing the functions of anatase-type titanium dioxide and TiO ₂ that have already been put into practical use are shown in Table 1.

The photocatalyst, TiO _2, is said to exhibit its function as a semiconductor only when it receives and excites energy corresponding to its band gap energy of 3.2 eV from ultraviolet light having a wavelength of 380 nm.

When energy from ultraviolet rays is received, electrons in the valence band are excited and move to the conduction band. Holes are formed in the traces where electrons have escaped. It is explained that the strong oxidation function of hydroxyl radical (.OH) generated by depriving electrons of H ₂ O in contact with holes is the function of the photocatalyst itself.

The oxidizing power of hydroxyl radicals is determined by the C—C, C—H, C—N, C—O, O—H, and N—H in the molecules that make up inorganic and organic substances such as chemical substances that cause environmental pollution. These bonds can be broken and broken because they are much larger than the bond energy.

Therefore, it is possible to clean the chemical substances and the like that cause environmental pollution with a strong oxidizing power cleanly by irradiation with ultraviolet rays, which can be an effective means for environmental purification. The biggest feature is that the reaction proceeds permanently without being consumed or changing its properties. It should be noted that the concentration of hydroxyl radicals produced is extremely small under the amount of ultraviolet rays present in the living space, which is completely harmless to the human body.

However, it seems that the limitation of this technology exists in that hydroxyl radicals are generated only after receiving ultraviolet rays. Research and development has been started to break this technical limit.

In the present invention, the present inventors have already proposed a photocatalyst capable of generating hydroxyl radicals without irradiation with ultraviolet rays. However, in view of the disadvantage that it is expensive and difficult to be widely used in the world, it is extremely inexpensive and the same. It is a new proposal of a new functional body based on a novel discovery having a function.
Japanese Patent Application No. 2004-227533 JP 2002-316056 PR The Chemical Society of Japan "Catalyst Chemistry Involving Light" (1994) Hashimoto, Kobayakawa “Photocatalyst and Semiconductor Electrode” (CMC Publishing) Kominato "Chemistry of non-stoichiometric compounds" (Baifukan) N A Trobov et al. “Metallic oxide phase diagram” (published by Nisso News Agency)

The process in which the photocatalyst performs its function is as follows.
(1) Irradiation of the photocatalyst with ultraviolet rays (2) Electrons in the valence band move to the conduction band.
(3) Holes are generated where the electrons in the charged band are missing.
(4) Water molecules are adsorbed on the holes.
(5) Water molecules are deprived of electrons and decomposed into hydrogen ions and hydroxyl radicals.
(6) The generated hydroxyl radical decomposes organic matter and the like.
The feature of the photocatalyst is that “holes are generated only by UV irradiation”.

The application for "providing a p-type semiconductor in which holes exist in advance without irradiation with ultraviolet rays", which improved the problems of conventional photocatalysts, was made in advance.

    However, since the synthesis is expensive, the subject of this patent is to propose a “semiconductor in which holes exist in advance” having the same function.

1) The basic concept of the present invention “ultraviolet irradiation → hole generation” is a mechanism by which a conventional photocatalyst exerts its function. The present inventors have already proposed a “p-type semiconductor having holes in advance”. At the same time, it was proved in the prior application patent that “a p-type semiconductor having holes in advance” has the same function as a conventional photocatalyst without irradiation with ultraviolet rays.

  That is, when water molecules contained as a gas are contacted and adsorbed to the extent that they are indicated by the dew point of water or a gas body of any kind, on the “p-type semiconductor that holds holes in advance”, the holes become water. Takes electrons from the molecule and generates hydroxyl radicals (.OH). The function of this hydroxyl radical is as described above. The catalytic function expressed by this mechanism does not require any ultraviolet irradiation.

2) Specific means of the present invention The crystals of transition metal stoichiometric oxide and stoichiometric nitride are electrically neutral. This principle is the fundamental idea of the proposal of the present invention.

It is well known that transition metals constitute non-stoichiometric compounds because each atom constitutes multiple valence states. Typical examples are nonstoichiometric oxides and nonstoichiometric nitrides.

Nonstoichiometric oxides and nonstoichiometric nitrides are further classified into metal-rich and metal-deficient types.

Among these, in the metal-deficient non-stoichiometric oxides and nitrides, the holes corresponding to the deficient metal atoms (+ charges) are contained in the valence crystal in order to maintain electrical neutrality at the same time as the generation. It is formed.

In other words, both the metal-deficient non-stoichiometric oxide and the metal-deficient non-stoichiometric nitride are p-type semiconductors that hold holes in advance.

    Various technical studies on crystallographic elucidation of transition metal oxides have been conducted. However, despite the technical efforts, it is difficult to say that the details have been completely elucidated.

    However, crystallographic discussion is not necessary in the present invention. The stoichiometric oxide and stoichiometric nitride of transition metals that are electrically neutral are logically set and specified, and the metal-deficient non-stoichiometric oxide and non-stoichiometric ratio for the specified stoichiometric compound are specified. It is the gist of the present invention to propose the setting of nitride.

    (Table 2) shows the results of the investigation of the transition metal-oxygen binary phase diagram based on the research results of many researchers, and the results summarized in the gist of the present invention.

When the compound showing electrical neutrality is TiO, X = 1 means a stoichiometric oxide. When X <1, it becomes a metal-rich non-stoichiometric oxide, and e ⁻ is generated that balances + electrons of excess metal to form an n-type (−) semiconductor.

    When X> 1, a metal-deficient type, that is, an oxygen-excess type non-stoichiometric oxide is formed. A “hole” is generated that balances the negative electrons of excess oxygen, thereby forming a p-type (+) semiconductor.

  In the semiconductor type column of (Table 3), all the semiconductors marked with a circle in the p (+) type semiconductor column, that is, metal-deficient semiconductors, are proposed in the present invention as “p in which holes are present in advance”. Belongs to the category of "type semiconductors". That is, all of these semiconductors are included in the present invention.

    However, in order to be widely used in the world, it is necessary to obtain a metal-deficient non-stoichiometric oxide having p-type semiconductor characteristics at a low cost.

As a result of searching various low-priced compounds that are metal-deficient non-stoichiometric oxides having p-type semiconductor properties, iron oxides contained in large amounts in steelmaking slag are Fe _X O (X < It has been discovered that the metal-excess type oxide having the composition 1) has p-type semiconductor characteristics and exhibits a photocatalytic effect without irradiation with ultraviolet rays. This is a very significant discovery.

  Steelmaking slag is a so-called industrial waste that is inevitably by-produced in the refining process of steelmaking and ironmaking, and its production amount is said to correspond to 10% of the produced steel.

The metal-deficient non-stoichiometric oxide Fe _X O (X <1) proposed in the present invention is present in a large amount in steelmaking slag. Conventional photocatalysts are mainly composed of titanium oxide, and the price for photocatalyst use is 2000 yen or more per kilogram. Since Fe _X O (X <1) according to the present proposal can be manufactured by extraction from steelmaking slag, the effect of being able to be manufactured at a considerably low cost compared with the conventional photocatalyst is great.

In Fe _X O (X <1) proposed by the present invention, excessive “holes” are generated in advance. Therefore, when a temperature gradient is applied to these, a small amount of power generation function due to the Seebeck effect is exhibited. Since this power generation function exhibits an effect of improving blood circulation in the body, the metal-deficient non-stoichiometric oxide or the metal-deficient non-stoichiometric nitride of the present invention is also valuable for use as a body function preservation product.

In addition, the significance of opening the way to application of steelmaking slag, which is abandonment and industrial waste, has valuable value.

An iron oxide mainly composed of Fe _X O (X <1) obtained in a powder form from steelmaking slag is made as fine as possible and used as follows.
(1) Use as powder.
(2) Use by mixing powder in a solvent.
(3) Used by coating the surface layer of a structure such as ceramics.
(4) Use as a fired product in which powder is mixed with other ceramics.
(5) Used by sintering only powder.

    When using the powder as it is, it is used by mixing it with all fibers. Various fiber products having a photocatalytic effect can be manufactured at low cost. It can be effectively used for hospitals, nursing facilities for the elderly, hotels, sheets for the Shinkansen, etc.

    A typical usage when the powder is mixed with a solvent is a use as a spray. It can be used effectively for various deodorizing, antifouling and antibacterial areas such as inner and outer walls, curtains, floors and kitchens.

    Used on ceramics, plastic, glass, wood and various metals. Applications range widely, for example, coated plastic spheres can be effectively used for sterilization of water absorption towers and purification of feed water.

It can be used after being kneaded in a ceramic or the like and fired, or coated on the surface and fired.

It can be used as a p-type semiconductor for oxidation catalyst applications by sintering into a porous filter form.

As shown in Table 3, the acetaldehyde decomposition effect of the Fe _X O (X <1) of the present invention in the ultraviolet irradiation environment and the decomposition effect of the conventional photocatalyst are almost the same. The material of the present invention exhibits the same function as a photocatalyst even under an ultraviolet irradiation environment.

  The decomposition function of acetaldehyde with the elapsed time of the material of the present invention when no black lamp was irradiated is shown in Example 2 of (Table 3). Acetaldehyde is decomposed without irradiation of a black lamp. On the other hand, in the case of a normal photocatalyst, the decomposition function of acetoaldode is not recognized in an environment without black lamp irradiation.

Examples 1 and 2 are metal-deficient non-stoichiometric iron oxide Fe _0.94 O extracted from special steel-made steel slag. Comparative Material 1-2 is a conventional photocatalyst TiO _2.

    The outline of the method for evaluating the photocatalytic function and the method for measuring the amount of acetaldehyde in the examples of the present invention is shown in Table 4.

Comparative materials 1 and 2 are conventional photocatalysts. Although the acetaldehyde is satisfactorily decomposed in the environment of the black lamp irradiation, the acetaldehyde is hardly decomposed in the environment without the black lamp irradiation.

  Examples 1 and 2 are metal-deficient non-stoichiometric oxides provided by the present invention, which are p-type semiconductors, and acetaldehyde is efficiently decomposed regardless of the presence or absence of a black lamp.

Fe _X O (X <1) When the non-stoichiometric oxide is generated, the holes generated in advance in the crystal oxidize and decompose the water component adsorbed on the crystal, and the hydroxyl radical (.OH) generates acetaldehyde. This phenomenon can be explained by disassembly.

An example demonstrates the effect of the material by this invention in the environment where an ultraviolet-ray is not irradiated. All of the test materials used in the following examples are iron balls mainly composed of Fe _X O (X <1) showing p-type semiconductor characteristics extracted from the steelmaking slug proposed in the present invention on a ceramic sphere having a diameter of 5 mm. A spherical structure coated with oxide powder.

  The effect of the material of the present invention on the effect of removing chlorine contained in tap water is shown in (Table 5). In addition, the numerical value in a table | surface is content (ppm) measured with the chlorine meter.

0, 1, 2, and 6 spherical structures were inserted into 100 CC tap water, held in a non-light environment for a predetermined time, and the amount of chlorine was measured with a chlorine meter.

  It is clearly recognized from (Table 5) that the material of the present invention effectively decomposes and releases chlorine in tap water.

Using an air purifier equipped with 100 spherical structure bodies per 10 cm ² , which is a test material similar to that in Example 3, in an environment where light irradiation is not performed, The change in odor was measured. The measurement was performed with a CIAQ (Composite Index of Air Quality) instrument and displayed as a CIAQ value. The results are shown in (Table 6).

  Room A was a room with a strong odor and had a CIAQ value of 60. As a result of operating the air cleaner using the filter equipped with the spherical structure of the present invention for 30 minutes, there was no odor sensed by the sense of smell, and the CIAQ value was 15.

      Similar effects are recognized in other rooms, and the effectiveness of the material of the present invention is proved.

  The antibacterial effect of the material of the present invention is shown in (Table 7). Bacterial liquid was put into 100 CC purified water charged with three inventive materials, and the change in the number of bacteria after being kept in the dark room for each time was measured. (The number of bacteria at the start-the number of bacteria after holding) / The number of bacteria at the start is displayed in%.

  Although there is a difference in effect, all these bacteria have a bactericidal effect under no lighting. By increasing the number of inputs, it has been confirmed that the effect is accelerated.

  There is no doubt that the effect of the material of the present invention, which is recognized under no illumination, has an extremely great value that has never been recognized. It goes without saying that the effects of the material of the present invention can be easily proved against various fungi other than bacteria, viruses and the like mentioned in the Examples and are included in the scope of claims of the present invention.

    The material of the present invention has the characteristics of a p-type semiconductor as already described in detail. It is recognized as a physical phenomenon that negative electrons are exchanged between a p-type semiconductor and a contact object when an organic or inorganic substance comes into contact with the crystal surface of the p-type semiconductor. It can be said that the water is brought into contact with the p-type semiconductor and the .OH radical is generated as a result of the electrons of water being taken away by the p-type semiconductor.

  The p-type semiconducting property of transferring electrons after adsorption is used as an oxidation active catalyst for automobile exhaust gas. Therefore, the oxidation activity catalytic effect of the material of the present invention was measured.

  The results are shown in (Table 8). The general-purpose catalyst shown in the comparison is a platinum-palladium catalyst. The material of the present invention exhibits an oxidation active catalyst function similar to a general-purpose catalyst.

Photocatalysts have been put into practical use for various applications utilizing their functions (Table 1). However, since the irradiation with ultraviolet rays is an indispensable condition for exhibiting the functions, the practical use has been delayed.

The proposal of the present invention makes it unnecessary to irradiate ultraviolet rays, and it is not necessary to say that the applications shown in Table 1 and the practical application to various fields will be actively promoted. In particular, application development will become increasingly active as a material for environmental improvement and environmental conservation.

However, since functional materials having a photocatalytic function are expensive, there is a drawback that they cannot be widely used.

It has been found that FeXO (X <1) having a photocatalytic function is present in steelmaking slag without ultraviolet irradiation, and the photocatalytic effect can be widely used. Therefore, the effect of the present invention is great.

The present invention relates to the discovery that the iron oxide inevitably contained in electric furnace slag, converter slag, hot rolling scale and copper smelting slag is a metal-deficient non-stoichiometric oxide having p-type semiconductor characteristics. It relates to its effective use.

About 30 years ago, a photocatalytic reaction capable of photodegrading water using a ceramic semiconductor (rutile-type titanium dioxide) as a photoelectrode was discovered in Japan, and as a result, development research on the photocatalytic reaction was actively started. .

Since then, extensive research and development has been promoted, and the practical application of photocatalytic reactions using white fine powder of titanium dioxide (anatase type, large specific surface area), which is mass-produced and marketed, is mainly applied to the structure. Yes.

The target photocatalyst is required to be irradiated with ultraviolet rays, and development research on practical application of anatase-type titanium dioxide and TiO ₂ having a photocatalytic function has been actively promoted.

Examples of application development utilizing the functions of anatase-type titanium dioxide and TiO ₂ that have already been put into practical use are shown in Table 1.

The photocatalyst, TiO ₂ exhibits its function as a semiconductor only after receiving energy corresponding to its band gap energy of 3.2 eV from ultraviolet light having a wavelength of 380 nm and exciting it.

When energy from ultraviolet rays is received, electrons in the valence band are excited and move to the conduction band. Holes are formed in the traces where electrons have escaped. It is explained that the strong oxidation function of hydroxyl radical (.OH) generated by depriving electrons of H ₂ O in contact with holes is the function of the photocatalyst itself.

The oxidizing power of hydroxyl radicals is determined by the C—C, C—H, C—N, C—O, O—H, and N—H in the molecules that make up inorganic and organic substances such as chemical substances that cause environmental pollution. These bonds can be broken and broken because they are much larger than the bond energy.

Therefore, it is possible to clean the chemical substances and the like that cause environmental pollution with a strong oxidizing power cleanly by irradiation with ultraviolet rays, which can be an effective means for environmental purification. The biggest feature is that the reaction proceeds permanently without being consumed or changing its properties. It should be noted that the concentration of hydroxyl radicals produced is extremely small under the amount of ultraviolet rays present in the living space, which is completely harmless to the human body.

However, it seems that there is a limit of this technology in becoming a semiconductor only after receiving ultraviolet rays. For this purpose, new photocatalysts that react also in the visible and infrared wavelength regions are being developed.

    The inventors noticed that the function of the photocatalyst is expressed due to the electron transfer function of the p-type semiconductor. We have found that a metal-deficient non-stoichiometric transition metal oxide having p-type semiconductor properties newly synthesized by a combustion synthesis method exhibits the same function as a photocatalyst in an environment where light irradiation is not performed. Yes.

Based on this technical point of view, further research was conducted on a wide range of metal-deficient non-stoichiometric metal oxides having p-type semiconductor characteristics. As a result, among the iron oxides that are components of steel slag that is a byproduct of steel refining, iron oxides that make up the hot rolling scale, and iron oxides that are contained in copper slag that is a byproduct of copper refining, It was discovered that iron oxide, Fe _X O (X <1), which is a p-type semiconductor, exists.

In general, it can be expressed that several percent of p-type semiconductors are present in these by-products, in which approximately 7,000,000 tons are used annually for roadbed materials, raw materials for cement clinker, and the like. These by-products have a p-type semiconductor characteristic of more than 50% in a plurality of iron oxides contained about 30% in oxide slag, about 50% in copper slag and 95% or more in the rolling scale. It was also discovered that the iron oxide Fe _X O (X <1) was contained.

In other words, the iron oxide Fe _X O (X <1) having p-type semiconductor characteristics is mixed with other components without being utilized, and is left unnecessarily as a structural member such as a roadbed material. It will be that.

Among them, if iron oxide Fe _X O (X <1) having p-type semiconductor characteristics is extracted and used as a functional material, its social contribution can be immense. Like.

The present invention proposes a valuable application by measuring various properties of iron oxide Fe _X O (X <1) having p-type semiconductor properties.
Japanese Patent Application No. 2004-227533 JP 2002-316056 PR The Chemical Society of Japan "Catalyst Chemistry Involving Light" (1994) Hashimoto, Kobayakawa “Photocatalyst and Semiconductor Electrode” (CMC Publishing) Kominato "Chemistry of non-stoichiometric compounds" (Baifukan) N A Trobov et al. “Metallic oxide phase diagram” (published by Nisso News Agency)

The process in which the photocatalyst performs its function is as follows.
(1) The photocatalyst is irradiated with ultraviolet rays.
(2) Electrons in the valence band move to the conduction band.
(3) Holes are generated where the electrons in the charged band are missing.
(4) Water molecules are adsorbed on the surface of the photocatalytic crystal.
(5) Electrons are exchanged between the crystal surface and water molecules via holes.
(6) Water molecules are deprived of electrons and decomposed into hydrogen ions and hydroxyl radicals.
(7) The generated hydroxyl radical decomposes organic matter and the like.
The feature of the photocatalyst is that “holes are generated only by UV irradiation”.

The application for "providing a p-type semiconductor in which holes exist in advance without irradiation with ultraviolet rays", which improved the problems of conventional photocatalysts, was made in advance.

    However, since the synthesis is expensive, the subject of this patent is to propose a “semiconductor in which holes exist in advance” having the same function.

1) The basic concept of the present invention “ultraviolet irradiation → hole generation” is a mechanism by which a conventional photocatalyst exerts its function. The present inventors have already proposed a “p-type semiconductor having holes in advance”. At the same time, it was proved in the prior application patent that “a p-type semiconductor having holes in advance” has the same function as a conventional photocatalyst without irradiation with ultraviolet rays.

  That is, when water molecules contained as a gas are contacted and adsorbed to the extent that they are indicated by the dew point of water or a gas body of any kind, on the “p-type semiconductor that holds holes in advance” Takes electrons from water molecules and generates hydroxyl radicals (.OH). The function of this hydroxyl radical is as described above. The catalytic function expressed by this mechanism does not require any ultraviolet irradiation. In addition, in the “p-type semiconductor that has holes in advance”, regardless of whether the component that contacts or adsorbs on the surface of the semiconductor crystal is an inorganic substance or an organic substance, electrons are exchanged via holes on the crystal surface. It is predicted that a catalytic reaction will occur.

2) Specific means of the present invention The crystals of transition metal stoichiometric oxide and stoichiometric nitride are electrically neutral. This principle is the fundamental idea of the proposal of the present invention.

It is well known that transition metals constitute non-stoichiometric compounds because each atom constitutes multiple valence states. Typical examples are nonstoichiometric oxides and nonstoichiometric nitrides.

Nonstoichiometric oxides and nonstoichiometric nitrides are further classified into metal-rich and metal-deficient types.

Among these, in the metal-deficient non-stoichiometric oxides and nitrides, the holes corresponding to the deficient metal atoms (+ charges) are contained in the valence crystal in order to maintain electrical neutrality at the same time as the generation. It is formed.

In other words, both the metal-deficient non-stoichiometric oxide and the metal-deficient non-stoichiometric nitride are p-type semiconductors that hold holes in advance.

    Various technical studies on crystallographic elucidation of transition metal oxides have been conducted. However, despite the technical efforts, it is difficult to say that the details have been completely elucidated.

    However, crystallographic discussion is not necessary in the present invention. The stoichiometric oxide and stoichiometric nitride of transition metals that are electrically neutral are logically set and specified, and the metal-deficient non-stoichiometric oxide and non-stoichiometric ratio for the specified stoichiometric compound are specified. It is the gist of the present invention to propose the setting of nitride.

    (Table 2) shows the results of the investigation of the transition metal-oxygen binary phase diagram based on the research results of many researchers, and the results summarized in the gist of the present invention.

When the compound showing electrical neutrality is TiO, X = 1 means a stoichiometric oxide. When X <1, it becomes a metal-rich non-stoichiometric oxide, and e ⁻ is generated that balances + electrons of excess metal to form an n-type (−) semiconductor.

    When X> 1, a metal-deficient type, that is, an oxygen-excess type non-stoichiometric oxide is formed. A “hole” is generated that balances the negative electrons of excess oxygen, thereby forming a p-type (+) semiconductor.

  In the semiconductor type column of (Table 2), all the semiconductors marked with a circle in the p (+) type semiconductor column, that is, metal-deficient semiconductors, are proposed in the present invention as “p in which holes are present in advance”. Belongs to the category of "type semiconductors". That is, all of these semiconductors are included in the present invention.

    However, in order to be widely used in the world, it is necessary to obtain a metal-deficient non-stoichiometric oxide having p-type semiconductor characteristics at a low cost.

As a result of searching various low-priced compounds that are metal-deficient non-stoichiometric oxides having p-type semiconductor properties, iron oxides contained in large amounts in steelmaking slag, hot rolling scale and copper slag are listed in (Table 2). The present inventors have found that it is a metal-excess type oxide having a composition of Fe _X O (X <1), has p-type semiconductor characteristics, and exhibits a photocatalytic effect without irradiation with ultraviolet rays. This is a very significant discovery.

The iron oxide Fe _X O (X <1) having p-type semiconductor properties obtained in this way is a by-product of steel production and copper production, and is used as a structural material such as roadbed material together with other components. Yes. Among these by-products, p-type semiconductor characteristics of more than 50% in a plurality of iron oxides contained about 30% in oxidized slag in electric furnace slag, about 50% in copper slag and 95% or more in the rolling scale. It was also discovered that the iron oxide Fe _X O (X <1) was contained.

The iron oxide Fe _X O (p <1) having p-type semiconductor characteristics has non-magnetic characteristics, and the other iron oxides are ferromagnets. Therefore, iron oxide having p-type semiconductor characteristics can be easily obtained by magnetic separation. The product Fe _X O (X <1) can be separated from other iron oxides. Practically, the iron oxide Fe _X O (X <1) having p-type semiconductor characteristics is allowed to contain a certain amount of other iron oxides and oxides other than iron.

Since the iron oxide Fe _X O (X <1) having p-type semiconductor characteristics can be separated by a simple pulverization process and a selection process, its manufacturing cost is extremely low.

Conventional photocatalysts are mainly composed of titanium oxide, and the price for photocatalyst use is 2000 yen or more per kilogram. Since Fe _X O (X <1) according to the present proposal can be manufactured by extraction from steelmaking slag or the like, it can be manufactured at a considerably lower cost than conventional photocatalysts, so its social effect is great.

    The material of the present invention exhibits the function possessed by a conventional photocatalyst without irradiation with ultraviolet rays. Furthermore, it discovered that a valuable function as a p-type semiconductor was exhibited.

    It has also been clarified that the p-type semiconducting property of transferring electrons after adsorption can be used as an oxidation active catalyst for automobile exhaust gas.

Furthermore, since Fe _X O (X <1) generates excessive “holes” in advance, if a temperature gradient is applied to these, a very small amount of power generation function due to the Seebeck effect is exhibited. Since this power generation function exhibits an effect of improving blood circulation in the body, the metal-deficient non-stoichiometric oxide or the metal-deficient non-stoichiometric nitride of the present invention is also valuable for use as a body function preservation product.

These functional effects are summarized in Table 3.

An iron oxide mainly composed of Fe _X O (X <1) obtained in a powder form from steelmaking slag or the like is miniaturized as much as possible and provided as follows.
(1) Use as powder.
(2) Use by mixing powder in a solvent.
(3) Used by coating the surface layer of a structure such as ceramics.
(4) Use as a fired product in which powder is mixed with other ceramics.
(5) Used by sintering only powder.

    When using the powder as it is, it is used by mixing it with all fibers. Various fiber products having a photocatalytic effect can be manufactured at low cost. It can be effectively used for hospitals, nursing facilities for the elderly, hotels, sheets for the Shinkansen, etc. It can also be said that it includes future possibilities as pharmaceuticals.

    A typical usage when the powder is mixed with a solvent is a use as a spray. It can be used effectively for various deodorizing, antifouling and antibacterial areas such as inner and outer walls, curtains, floors and kitchens.

    Used on ceramics, plastic, glass, wood and various metals. Applications range widely. For example, coated plastic and ceramic spheres can be effectively used for sterilization of water absorption towers and purification of feed water.

It can be used after being kneaded in a ceramic or the like and fired, or coated on the surface and fired. These can be used as containers and interior products.

It can be used as a p-type semiconductor for oxidation catalyst applications by sintering into a porous filter form.

As shown in Table 4, the acetaldehyde decomposition effect of the Fe _X O (X <1) of the present invention in an ultraviolet irradiation environment and the conventional photocatalyst decomposition effect are almost the same. The material of the present invention exhibits the same function as a photocatalyst even under an ultraviolet irradiation environment. Note that the test apparatus conforms to JIS R1701-1 (2004).

  The decomposition function of acetaldehyde with the elapsed time of the material of the present invention when no black lamp was irradiated is shown in Example 2 of (Table 4). Acetaldehyde is decomposed without irradiation of a black lamp. On the other hand, in the case of a normal photocatalyst, the decomposition function of acetoaldode is not recognized in an environment without black lamp irradiation.

Examples 1 and 2 are metal-deficient non-stoichiometric iron oxides Fe _X O extracted from special steel-made steel slag and the like. Comparative Material 1-2 is a conventional photocatalyst TiO _2.

Comparative materials 1 and 2 are conventional photocatalysts. Although the acetaldehyde is satisfactorily decomposed in the environment of the black lamp irradiation, the acetaldehyde is hardly decomposed in the environment without the black lamp irradiation.

  Examples 1 and 2 are metal-deficient non-stoichiometric oxides provided by the present invention, which are p-type semiconductors, and acetaldehyde is efficiently decomposed regardless of the presence or absence of a black lamp.

This phenomenon can be explained by the fact that holes generated in advance in the Fe _X O (X <1) crystal oxidatively decompose the acetaldehyde component adsorbed on the crystal.

An example demonstrates the effect of the material by this invention in the environment where an ultraviolet-ray is not irradiated. All of the test materials used in the following examples mainly consisted of Fe _X O (X <1) showing p-type semiconductor characteristics extracted from a steelmaking slug proposed in the present invention on a ceramic sphere having a diameter of 5 mm. A spherical structure coated with iron oxide powder.

The ceramic sphere and Fe _X O (X <1) are inserted into the same container, and then the container is rotated at a rotational speed that applies a centrifugal force to the interior material, so that Fe _X O (X <1) A powder coating layer was formed.

    The effect of the material of the present invention on the effect of removing chlorine contained in tap water is shown in (Table 5). In addition, the numerical value in a table | surface is content (ppm) measured with the chlorine meter.

0, 1, 2, and 6 spherical structures were inserted into 100 CC tap water, held in a non-light environment for a predetermined time, and the amount of chlorine was measured with a chlorine meter.

  It is clearly recognized from (Table 5) that the material of the present invention effectively decomposes and releases chlorine in tap water.

A spherical structure, which is the same test material as in Example 3, was used in an ordinary house indoors in an environment where no light was irradiated using an air cleaner equipped with a filter loaded with 100 per 10 cm ² . The change in odor was measured. The measurement was performed with a CIAQ (Composite Index of Air Quality) instrument and displayed as a CIAQ value. The results are shown in (Table 6). The CIAQ value is a scale that comprehensively shows the odor of hydrocarbon compounds.

  Room A was a room with a strong odor and had a CIAQ value of 60. As a result of operating an air cleaner using a filter equipped with the spherical structure of the present invention for 30 minutes, there was no odor sensed by the sense of smell, and the CIAQ value was 15.

        The same effect is recognized also in other rooms, and the deodorizing effect of the material of the present invention is proved.

    The antibacterial effect of the material of the present invention is shown in (Table 7). Bacterial liquid was put into 100 CC purified water charged with three inventive materials, and the change in the number of bacteria after being kept in the dark room for each time was measured. The result is obtained by the formula of (the number of bacteria at the start-the number of bacteria after the holding) / the number of bacteria at the start, and is displayed as the sterilization rate (%).

    Although there is a difference in effect, all these bacteria have a bactericidal effect under no lighting. By increasing the number of inputs, it has been confirmed that the effect is accelerated.

    There is no doubt that the effect of the material of the present invention, which is recognized under no illumination, has an extremely great value that has never been recognized. It goes without saying that the effects of the material of the present invention can be easily proved against various fungi other than bacteria, viruses and the like mentioned in the Examples, and are included in the claims of the present invention. This suggests the possibility of being used as a medicine in the future.

      As already described in detail, the material of the present invention has the characteristics of a p-type semiconductor. It is recognized as a physical phenomenon that negative electrons are exchanged between a p-type semiconductor and a contact object when an organic substance or an inorganic substance contacts the crystal surface of the p-type semiconductor.

The iron oxide Fe _X O (X <1) having the p-type semiconductor characteristics proposed by the present invention can be expected to further have an oxidation active catalytic effect.

The results of measuring the oxidation catalyst effect are shown in (Table 8). In a standard gas atmosphere of CO: 4.8% and O ₂ : 4.8%, the state of oxidative decomposition of CO was indicated by the decomposition rate (%).
The general-purpose catalyst shown in the comparison is a platinum-palladium catalyst. The material of the present invention exhibits an oxidation active catalyst function similar to a general-purpose catalyst. In addition, the same oxidative decomposition effect has been confirmed for fine carbon particles (soot).

Photocatalysts are being put into practical use for various applications that utilize their functions (Table 1), but UV irradiation is an indispensable condition for demonstrating the function and is also practical because it is expensive in price. It is late.

We found that iron oxide Fe _X O (X <1) having p-type semiconductor characteristics exists in steelmaking slag, etc., and Fe _X O (X <1) is more than the photocatalytic effect without ultraviolet irradiation. It was possible to grasp that the function was performed as measurement data.

Fe _X O (X <1) is contained in blast furnace slag, electric furnace slag, converter slag, hot rolling scale, copper slag, and the like. These are all byproducts of steel and copper production, and can be obtained at low cost. As a result, the production cost of Fe _X O (X <1) is extremely low compared with conventional photocatalysts. In addition, it can be said that the above-mentioned by-product, which has been treated as industrial waste, can be used as a functional product.

In addition, the function of Fe _X O (X <1) is higher than that of conventional photocatalysts and has the characteristics of a p-type semiconductor. Can be used.

  For example, it can be expected to be used as various gas sensors, thermistors, varistors, light emitting diodes, and conductive oxides.

In short, the point of the present invention is “A semiconductor was found in industrial waste”.

Claims (12)

Metal-deficient indefinite, mainly iron oxide powder obtained by extraction, separation and pulverization from at least one of electric furnace slag, converter slag, and hot rolling scale, and the iron oxide has p-type semiconductor characteristics It is a specific oxide, and the structure composed of the powder as it is and mixed with the powder or coated on the surface exhibits a photocatalytic function in an environment where no ultraviolet rays are irradiated. Functional powder and structure. 2. The spraying solvent according to claim 1, wherein the powder is mixed in a solvent, and the spray filled with the solvent. 3. A low-cost solvent for spraying and a spray filled with the solvent according to claim 2, wherein the solvent is applied for anti-staining of inner and outer walls, deodorization in the room, air purification in the room, and antibacterial against germs. . 2. Various fibrous products according to claim 1, wherein the powder is mixed with a fibrous woven fabric, a sheet and a non-woven fabric. 5. Various clothes-like products according to claim 4, which are applied for antifouling, deodorization, indoor air purification, and antibacterial against germs. The ceramic structure according to claim 1, wherein the powder is supported on a surface layer. The powder of claim 1 and a ceramic sphere intended to coat the powder on the surface are inserted into the same container, and then the container is rotated at a rotational speed that applies a centrifugal force to the interior material. A functional structure having the powder coating layer according to claim 1 formed on a surface of a sphere. 8. The functional structure according to claim 6, wherein the ceramic structure is substantially a sphere and is applied to water quality improvement applications. 8. The functional structure according to claim 6, wherein the ceramic structure is substantially a sphere and is applied to air cleaning applications such as deodorization.   A functional structure, wherein the structure according to claim 1 has a filter shape.   2. Various ceramics made by kneading the powder of claim 1 into ceramics.   A functional structure obtained by sintering the powder of claim 1.