KR100330627B1 - Producing method for Photocatalyst being coated Metal Oxide and Titanium Dioxide - Google Patents

Abstract

Since the activity of the TiO ₂ photocatalyst was found to be larger as the particle diameter of the TiO ₂ fine powder was smaller, fine powders of 10 to 20 nm or less were prepared. However, such fine powder tends to cause aggregation, leading to problems such as lowering the efficiency of the photocatalyst or limiting its use. Therefore, in consideration of the availability of the photocatalyst, the fine TiO ₂ powder is used to be supported on a carrier, and a porous material such as zeolite is mainly used as the carrier. However, since the photocatalytic reaction of TiO ₂ occurs only at the surface where light is exposed, it is not preferable to use a porous oxide as a carrier, and porous materials such as synthetic zeolites are expensive and are causing factors to increase the price of the photocatalyst. .

The present invention has been made to improve the problems of the prior art operating as described above, the main purpose of the carrier of the photocatalyst is not a porous material, but cheap natural minerals such as silica, kaolin, feldspar, feldspar, clay, Low-cost TiO ₂ complex coating a small amount of semiconducting metal oxides (WO ₃ , Fe ₂ O ₃ , SnO ₂ , Cu ₂ O, Nb ₂ O _5, etc.) to improve the photocatalytic activity of TiO ₂ coated on the surface of the carrier It is characterized by providing a method for producing a photocatalyst.

Description

Producing method for Photocatalyst being coated Metal Oxide and Titanium Dioxide}

The present invention relates to the production of low-cost photocatalyst for improving the properties of titanium dioxide (hereinafter referred to as 'TiO ₂ ') photocatalyst and expanding the usability of the photocatalyst, and more specifically, natural mineral powder such as silica, kaolin, feldspar, feldspar, clay Photocatalytically coated with anatase-type TiO ₂ with a small grain size and semiconducting metal oxides such as WO ₃ , Fe ₂ O ₃ , SnO ₂ , Cu ₂ O, and Nb ₂ O ₅ It is about manufacture.

Photocatalytic action has been identified in various semiconductors, but TiO ₂ is the most widely used at present. This is because, firstly, it exhibits sufficient catalytic activity by ultraviolet rays contained in sunlight or suitable artificial light, secondly, chemically stable, thirdly harmless to the environment and human body, and fourthly, the price is low and economical.

TiO ₂ has three types of crystal structures: anatase type, rutile type, and brookite type. Although rutile type TiO ₂ is widely used in industrial paints and cosmetics, it is suitable as a photocatalyst. Anatase type TiO ₂ . The band gap of the anatase type TiO ₂ is 3.2 eV, and the band gap of the rutile TiO ₂ is 3.0 eV, because the anatase type is at the upper side of the conduction band so that the reducing power is strong and oxygen can be reduced more easily. . Anatase type TiO ₂ has the functions of degrading deodorization, deodorization, antibacterial, and decomposition and removal of pollutants in water or air, and thus can be mainly applied to environmental purification.

In the case of using the TiO ₂ fine powder as the photocatalyst, the smaller the particle diameter of the fine powder is, the larger the photocatalytic activity is, so that fine powder of 10 to 20 nm or less is used. However, such fine powder tends to cause aggregation, leading to problems such as lowering the efficiency of the photocatalyst or limiting its use. Therefore, it is common to use fine TiO ₂ powder supported on a carrier. As a carrier, porous materials such as zeolite are mainly used, but since the photocatalytic reaction of TiO ₂ occurs only at the surface where light is exposed, it is not preferable to use porous oxide as a carrier, and porous materials such as synthetic zeolites are expensive. It is a factor which raises the price of a photocatalyst.

The characteristics of the photocatalyst depend on the particle size of TiO ₂ supported on the surface of the carrier. The smaller the particle size (or grain size) of TiO ₂ is, the higher the photocatalytic activity is. The method of coating TiO ₂ on the oxide powder serving as a carrier is generally a solution of titanium tetrachloride (TiCl ₄ ), a solution of titanium sulfate (Ti (SO ₄ ) ₂ ), and a solution of TNBT ((C ₄ H ₉ O) ₄ Ti), Precipitants such as sodium sulfite, formalin and sodium hydroxide are added dropwise to coat the titanium hydrate on the surface of the carrier, which is then heat-treated in air to obtain anatase-type TiO ₂ coating. However, the particle size of TiO ₂ obtained by such a method is about 15 nm, and it is difficult to obtain a coating layer of TiO _{2 having} a particle size of less than this. In order to reduce the coating amount of the TiO ₂ to produce a photocatalyst having a high activity and further reduce the particle size of the TiO ₂ (or grain size), by forming the electron trap sites in the band gap of TiO ₂ by the addition's heteroatom The bond between the former and the public must be prevented.

In the present invention, the carrier of the photocatalyst is a natural mineral such as silica, kaolin, feldspar, feldspar, and clay, which is not a porous material, and a small amount of semiconducting metal oxide (WO) is used to improve the photocatalytic activity of TiO ₂ coated on the surface of the carrier. There is a technical problem to provide a method for producing a TiO ₂ photocatalyst having a composite coating of ₃ , Fe ₂ O ₃ , SnO ₂ , Cu ₂ O, Nb ₂ O _5, and the like.

1 is a manufacturing process diagram of a titanium dioxide (TiO ₂ ) and a metal oxide composite coating photocatalyst using a natural mineral as a carrier

When described in detail with reference to the accompanying drawings, the present invention for achieving the above technical problem is as follows.

Figure 1 shows the manufacturing process of the TiO ₂ photocatalyst according to the present invention, as a carrier of the photocatalyst, silica, kaolin, feldspar, feldspar and clay having an average particle diameter of 10 to 30㎛ was used, and for the coating of TiO ₂ Titanium tetrachloride (TiCl ₄ ) aqueous solution, titanium sulfate (Ti (SO ₄ ) ₂ ) aqueous solution, TNBT ((C ₄ H ₉ O) ₄ Ti) solution was used as a source of titanium, and titanium hydroxide was formed on the surface of the carrier. As a precipitating agent, hydrazine, sodium sulfite, formalin, sodium hydroxide, ammonium bicarbonate and the like were used. In the coating treatment, a precipitant was added dropwise while the raw material powder was dispersed in the dilution liquid at room temperature and stirred. Diluent concentration of the titanium compound was 0.01M to 1M, 0.05M to 0.2M is preferred. Diluent concentration of the precipitant was 0.1M to 5M, 0.5M to 2.0M is preferred. After coating treatment, the solution was removed, washed, and dried at 110 ° C. for 24 hours.

A metal salt aqueous solution was used for the composite coating of hydroxides, such as tungsten, iron, and molybdenum, on the dried titanium hydrate coating support. As a source of tungsten, iron and molybdenum, respective nitrides, chlorides and ammonium compounds were used. Hydrazine, sodium sulfite, formalin, sodium hydroxide, ammonium bicarbonate, etc. were used as a precipitant for the production of metal hydroxides. The diluent concentration of the coating was set at 0.001M to 0.1M, and preferably 0.005M to 0.05M. The diluent concentration of the precipitant was set at 0.1M to 5M, and preferably 1.0M to 3.0M. After coating treatment, the solution was removed, washed, and dried at 110 ° C. for 24 hours.

As described above, a composite coating treatment of titanium hydroxide and hydroxides of metals such as tungsten, iron, and molybdenum was carried out using silica, kaolin, feldspar, feldspar, and clay as carriers. The composite hydroxide coating carrier was heat-treated for 1 to 10 hours at a temperature range of 400 ° C to 900 ° C to oxidize the hydroxide on the surface, and 500 ° C to 700 ° C is preferable as the heat treatment temperature, and the heat treatment time is 3 to 5 hours. It was appropriate.

The activity of the photocatalyst synthesized as above was evaluated by the removal rate of nitrogen oxides. In order to measure the removal rate of nitrogen oxide, UV light of 254 nm was used as a light source, NO standard gas was used as a source of nitrogen oxide, and NO concentration of the standard gas was 200 ppm (balance gas N ₂ ). The nitrogen oxide concentration was 3 to 4 ppm before the removal rate was measured. The nitrogen oxide concentration was changed after 15 minutes after the nitrogen oxide was added to the reactor. The measurement of nitrogen oxide was performed using the coroner's tube of GASTEC. In addition, the grain size of TiO ₂ formed on the surface of the carrier was determined using the Sherrer equation from the half width of the X-ray diffraction peak.

The grain size of TiO ₂ obtained by the method described above was 9-12 nm, and the removal rate of nitrogen oxide was improved by 10 to 23% in the sample coated with the metal oxide in comparison with the sample without the metal oxide in the composite coating. To get the result. The removal rate of nitrogen oxide showed up to 95%. This is in the process of the titanium hydroxide by heat treatment to form a Athanasiadis formulation TiO _2, than that of TiO ₂ metal ion of the heterodimer by inhibiting crystal growth of the anatase type TiO _2, without addition of the metal oxide, the crystal grain size (approx. 15nm) Smaller grains were obtained. In addition, the heterogeneous metal ions formed electron trap sites in the crystals of the anatase type TiO ₂ to interfere with the bonding of the electrons and the pores, thereby increasing the activity of the photocatalyst.

The following describes the present invention through comparative examples and examples.

<Example 1>

After crushing the WC grade kaolin produced in the Daemyung mine, it was classified using an air classifier so as to have an average particle diameter of 10 to 30 µm. 50 g of kaolin was suspended in a mixed aqueous solution of 0.1 M titanium tetrachloride and 0.2 M hydrochloric acid, and a precipitant was added dropwise while stirring at a speed of about 200 rpm. As a precipitant, 1 M aqueous ammonium bicarbonate solution was used. Kaolin coated with titanium hydroxide was dehydrated and dried at 110 ° C. for 24 hours.

Kaolin coated with titanium hydroxide was suspended in an aqueous solution of tungsten paraammonium [5 (NH ₄ ) ₂ O.12WO.5H ₂ O] at 0.01 M for secondary coating, followed by stirring at a rate of about 200 rpm and 1 M as a precipitant. Hydrazine aqueous solution of was dripped. After coating treatment, the solution was removed, washed, and dried at 110 ° C. for 24 hours.

Kaolin coated with titanium hydroxide and tungsten hydroxide was heat-treated at 500 ° C. for 4 hours to oxidize the hydroxide on the surface. The grain size was 10.3 nm and the removal rate of nitrogen oxide was 82.5%.

<Example 2>

50 g of kaolin was coated with titanium hydrate in the same manner as described in Example 1. Kaolin coated with titanium hydroxide was suspended in 0.02M aqueous solution of tungsten paraammonium [5 (NH ₄ ) ₂ O.12WO ₃ ㆍ 5H ₂ O] for secondary coating, and then stirred with a precipitant at a speed of about 200 rpm. 1 M aqueous hydrazine solution was added dropwise. Kaolin coated with a composite of titanium hydroxide and tungsten hydroxide was heat-treated after dehydration and cleaning as in Example 1. The grain size was 11.5 nm and the removal rate of nitrogen oxide was 91.3%.

<Example 3>

50 g of kaolin was coated with titanium hydrate in the same manner as described in Example 1. Kaolin coated with titanium hydroxide was suspended in 0.03 M aqueous solution of tungsten paraammonium [5 (NH ₄ ) ₂ O.12WO ₃ ㆍ 5H ₂ O] for secondary coating, and then stirred with a precipitant at a speed of about 200 rpm. 1 M aqueous hydrazine solution was added dropwise. Kaolin coated with a composite of titanium hydroxide and tungsten hydroxide was heat-treated after dehydration and cleaning as in Example 1. The grain size was 12.5 nm and the removal rate of nitrogen oxide was 95.2%.

Comparative Example 1

50 g of kaolin was subjected to a single coating of titanium hydrate in the same manner as described in Example 1, followed by dehydration, washing and heat treatment. The grain size was 15 nm and the removal rate of nitrogen oxide was 72.7%.

The present invention has the effect of lowering the manufacturing cost of the photocatalyst because the natural mineral as a support, and can be up to 9 ~ 12nm grain size of TiO ₂ by the composite coating treatment of TiO ₂ and metal oxides and the nitrogen oxide The removal ability is improved by about 10 to 20% and can be removed up to 95%, so that a highly active photocatalyst can be produced.

Claims (6)

Crushing and classifying the natural minerals as a carrier of a natural mineral powder having an average particle diameter of 10 ~ 30㎛, dispersed in a dilute solution of titanium hydroxide at room temperature, dropping a precipitant while stirring and dehydrating and washing at 110 ℃ After drying for 24 hours to prepare a primary coating carrier, the dried titanium hydrate coating carrier was dispersed in a dilute solution of metal hydroxide at room temperature, dropping a precipitant with stirring, followed by washing with dehydration and drying for 24 hours at 110 ℃, the carrier Method for producing a photocatalyst, characterized in that the heat treatment for 1 to 10 hours in the temperature range of 400 ℃ to 900 ℃ to oxidize the composite coating hydroxide on the surface of the The photocatalyst production method according to claim 1, wherein the natural mineral is silica, kaolin, feldspar, feldspar or clay. The method of claim 1, wherein the titanium hydroxide is a titanium tetrachloride (TiCl ₄ ) aqueous solution, titanium sulfate (Ti (SO ₄ ) ₂ ) aqueous solution or TNBT ((C ₄ H ₉ O) ₄ Ti) solution, the concentration of the diluted solution is 0.05M Photocatalyst Manufacturing Method ~ 0.2M The method of claim 1, wherein the precipitant is hydrazine, sodium sulfite, formalin, sodium hydroxide or ammonium bicarbonate, the concentration of the diluent is 0.5M to 2.0M for the coating of titanium hydroxide, the metal hydroxide coating Photocatalyst manufacturing method to 1.0M ~ 3.0M The method of claim 1, wherein the metal hydroxide is a semiconducting metal oxide, WO ₃ , Fe ₂ O ₃ , SnO ₂ , Cu ₂ O or Nb ₂ O ₅ The concentration of the diluent is 0.005M ~ 0.05M. The photocatalyst production method according to claim 1, wherein the heat treatment temperature for oxidizing the composite coated hydroxide on the surface of the natural mineral carrier is 500 ° C to 700 ° C and the heat treatment time is 3 to 5 hours.