KR100803738B1 - Method for preparing titaniumoxide photocatalyst with ti-peroxy gel - Google Patents

Abstract

A method for preparing titanium oxide photocatalysts by using a Ti-peroxy gel is provided to mass-produce titanium oxide photocatalysts, and prepare titanium oxide photocatalysts having various shapes by a simple process in which a chemical treatment and a heat treatment are combined with each other, wherein the prepared titanium oxide photocatalysts have a very high photocatalytic efficiency as well as excellent adhesion of a base metal with titanium oxide. As a preparation method of a titanium oxide photocatalyst having a crystal type titanium dioxide coating, the preparation method includes the steps of: cleaning surfaces of a Ti-based metal; dipping the cleaned surfaces of the Ti-based metal into a mixed solution consisting of an acid and an oxidizer to form an oxide coating layer with a mixed phase of an amorphous phase and a crystalline phase; and heat-treating the Ti-based metal having the mixed phased oxide coating layer formed thereon. The Ti-based metal is a pure Ti, or a Ti alloy comprising 80 wt.% to less than 100 wt.% of Ti as a Ti alloy comprising titanium(Ti) and at least one selected from the group consisting of aluminum(Al), vanadium(V), zirconium(Zr), niobium(Nb), nickel(Ni) and molybdenum(Mo).

Description

Method for preparing titanium oxide photocatalyst using titanium-peroxy gel {Method for preparing titaniumoxide photocatalyst with Ti-peroxy gel}

1 is a method for preparing a titanium oxide photocatalyst according to the present invention, the results of electron microscopy measurement of the surface structure (a) and the cross-sectional structure (b) of the titanium peroxygel film produced from the mixed solution added with sulfuric acid and oxidizing agent Figure is shown.

FIG. 2 is a diagram illustrating an XRD measurement result of a crystal structure of a titanium peroxygel film produced in a mixed solution containing sulfuric acid and an oxidizing agent in a method for preparing a titanium oxide photocatalyst according to the present invention.

FIG. 3 is a diagram illustrating XRD measurement results of a crystal structure of a fibrous TiO ₂ photocatalyst film formed by a combination of a chemical oxidation promoting reaction and a heat treatment in the method of preparing a titanium oxide photocatalyst according to the present invention.

4 is a view showing a photograph of one embodiment of the fibrous TiO ₂ photocatalyst shape prepared by the present invention in the method for producing a titanium oxide photocatalyst according to the present invention.

5 is a view showing the results of the efficiency test for the photocatalyst prepared by the titanium oxide photocatalyst production method according to the present invention through the dye decomposition of aniline blue (Aniline blue).

The present invention relates to a method for producing a titanium oxide photocatalyst using a titanium-peroxy gel, and more particularly, to mass production of titanium oxide photocatalyst by a simple process combining chemical treatment and heat treatment. In the titanium oxide photocatalyst, the prepared titanium oxide photocatalyst is not only excellent in adhesion between the base metal and titanium oxide, but also has a high photocatalytic efficiency in a method of preparing a titanium oxide photocatalyst using a titanium-peroxy gel. It is about.

The photocatalyst refers to a substance that receives a light and promotes a chemical reaction. Examples of the photocatalyst include a semiconductor, chlorophyll, V ₂ O ₃ , ZnO, ZrO ₂ , perovskite-type composite metal oxide (SrTiO ₃ ), and titanium oxide.

Titanium oxide can be used semi-permanently because it does not change even when it receives light. Since it oxidizes most organic materials and decomposes them into carbon dioxide and water, it is less secondary pollution and effective for removing bleach and odor. Therefore, in view of the above and the activity of the oxide film for the photocatalytic reaction, titanium oxide is emerging as a representative material in the photocatalyst field, and many studies have been conducted. Titanium oxide with a photocatalytic function is largely divided into anatase and rutile according to the crystalline form. In general, the rutile type has a problem that the crystal state is stable but the activity is inferior, and the anatase type has a high photocatalytic activity and thus may be a more preferable form in the photocatalyst field. The decomposition of organic matter by the photocatalyst generates electrons and holes when light energy above band gap energy is irradiated to the photocatalyst, and is adsorbed on the surface of the photocatalyst by the strong oxidizing power of the hydroxyl radical (-0H) generated by the photocatalyst. This is due to the oxidation reaction in which the gaseous or liquid organic matter is degraded.

As a method for using titanium oxide as a photocatalyst, a method of directly applying a powder of titanium oxide prepared as a photocatalyst or adding a binder such as silica to titanium oxide and coating it on a support or a carrier as a paint, titanium tetrachloride, titanium alkoxide, etc. After coating the titanium compound of the support on the support using a sol-gel method to form titanium oxide on the surface of the support and the like have been widely known.

In order to use titanium oxide (TiO ₂ ) powder itself as a photocatalyst, powdered titanium dioxide in which the crystal structure of anatase and rutile are mixed as a primary material is synthesized through a sulfuric acid method and a chlorine method. The titanium dioxide powder thus prepared is used in the form of a slurry or surface coated on a support. In addition, when TiO ₂ powder is directly used as a photocatalyst for wastewater treatment, a UV lamp is installed inside the photocatalytic reactor, and wastewater and TiO ₂ powder are mixed and used in a slurry form in the reaction cell, depending on the reaction time and throughput of the wastewater. The reaction cells are connected and used. In addition, a catalyst (TiO ₂ powder) recovery apparatus is attached to the reaction cell terminal of the apparatus. However, in this case, a separate device is required to recover and recycle the catalyst, TiO ₂ , and the cost of recovering and recycling the titanium oxide is not only economically expensive, but also a part of the waste water is adsorbed on the surface of the catalyst, thereby increasing the efficiency of the catalyst. As such, most of these slurry forms cannot be used for catalysts requiring a specific form and for photocatalysts for atmospheric purification.

When TiO ₂ is used as a photocatalyst for an air purifier, a method of coating and drying a solution in which a titanium dioxide powder is suspended on a carrier or a support has been used. However, the disadvantage of TiO ₂ surface coating is that the manufacturing method is complicated and the manufacturing cost is increased. Not only this, but also the bond between the support and the coated TiO ₂ is weak, the adhesion is weak, the surface of the photocatalyst is peeled off frequently used problems. The coating method using the sol-gel method is also widely used, but this method uses titanium ethoxide [Ti (OC ₂ H ₅ ) ₄ ]) or titanium tetraiso as the starting metal alkoxide. Since TiO ₂ sol must be prepared first using propane (titanium tetraisopropoxide), the manufacturing method is complicated and expensive, and there are many problems in use such as weak bonding of the TiO ₂ coated with the support. There is a need for a new type of catalyst production technology.

Korean patent application (Registration No .: 1004241000000, Application No .: 2001-59765) discloses a method for producing a fibrous TiO ₂ photocatalyst through electrochemical anodization. The fibrous TiO ₂ photocatalyst prepared by the electrochemical anodic oxidation method produces a TiO ₂ which exhibits a crystal structure of anatase and rutile by direct electrochemical reaction with titanium metal on a fine titanium fiber surface. By using the photocatalyst prepared in this way, the shape of the catalytic reactor does not need to be restricted and the adhesion of the film is good so that it can be used semi-permanently without the risk of peeling. It is remarkably excellent in terms of quality and effect, and can be applied to various fields such as air and water, but the photocatalyst production by the electrochemical method is not only an electrode device not only simple. There are process limitations such as excessive equipment required.

Accordingly, the present invention is to solve the problems of the prior art, it is possible to mass-produce and can produce various types of titanium oxide photocatalyst by a simple process combining the chemical treatment and heat treatment, the prepared titanium oxide photocatalyst is a base metal It is an object of the present invention to provide a method for producing a titanium oxide photocatalyst using a titanium-peroxy gel having a very high adhesion to titanium oxide and a very high photocatalytic efficiency.

The present invention to achieve the above technical problem,

A method of producing a titanium oxide photocatalyst having a crystalline titanium dioxide film,

Washing the titanium metal;

Immersing the washed surface of the titanium-based metal in a mixed solution of an acid and an oxidizing agent to form an oxide layer of an amorphous and crystalline mixed phase; And

Heat-treating the titanium-based metal on which the oxide layer of the mixed phase is formed

It provides a titanium oxide photocatalyst manufacturing method comprising the.

Hereinafter, the present invention will be described in more detail.

The present invention provides a method for producing a titanium oxide photocatalyst having a crystalline titanium dioxide film, the method comprising: washing a titanium metal; Immersing the washed titanium-based metal surface in a mixed solution of an acid and an oxidizing agent to form an oxide layer of an amorphous and crystalline mixed phase; And it provides a titanium oxide photocatalyst manufacturing method comprising the step of heat-treating the titanium-based metal on which the oxide film layer of the mixed phase is formed. This method eliminates the problems in the production of fibrous titanium oxide photocatalysts exhibiting high specific surface areas through electrochemical anodizing, i.e. inhibitors of mass production caused by complex process conditions, excessive equipment investment, etc. I can solve it.

 In the manufacturing method according to the present invention, the titanium-based metal is made of titanium, aluminum (Al), vanadium (V), zirconium (Zr), niobium (Nb), nickel (Ni) and molybdenum (Mo). It may be an alloy with one or more metals selected from the group, and the use of pure titanium metal is also possible, with the preferred titanium content of the titanium based metal being at least 80% by weight.

When the content of the titanium-based metal is less than 80% by weight, it may not only cause a problem in forming an oxide film of titanium-peroxygel, but also makes it difficult to transfer the crystal structure to titanium dioxide crystals through subsequent heat treatment.

In order to form titanium dioxide that exhibits photocatalytic properties on a titanium-based metal surface having a complex shape, oil or contaminants must be removed by first cleaning the surface of titanium. The cleaning solution that can be used in the manufacturing method is not particularly limited. All washes used in the art can be used but are preferably a mixed solution of hydrofluoric acid (HF), nitric acid (HNO ₃ ) and water.

The mixing ratio of the washing liquid is a ratio of the mixed volume of hydrofluoric acid (HF, 30-49 wt% solution), nitric acid (HNO ₃ , 50-70 wt% solution), and water in the ratio of 0.5 to 2 nitric acid relative to the volume ratio of hydrofluoric acid 1, And it is preferable that water is the ratio of 1.0-3.

If the volume ratio of the nitric acid (HNO ₃ ) is less than 0.5, the time required for surface cleaning is long, if more than 2 may cause a problem that the material size is rapidly reduced because the dissolution of titanium material is too fast. In addition, when the volume ratio of the water is less than 1, excessive dissolution of the titanium base metal may be a problem, and when it exceeds 3, a problem of increasing the time required for surface cleaning occurs.

In the preparation method, the washing time is preferably 1 to 2 minutes.

The surface-washed fibrous titanium or various forms of titanium soja are immersed in a mixed solution containing acid and an oxidizing agent, for example sulfuric acid, for a certain time, and the oxidation reaction of sulfuric acid on the surface of the fibrous titanium material On the surface of the titanium metal, oxidation is accelerated through the strong reduction of the added oxidant, Ti ^{4 +} (OH) _X (0 <X≤1), Ti ⁴⁺ (OH) ₂ O ₂ ^2- , Ti ^{4 _{+ (OH -) 2 O 2}} 2 - , and TiO ₂ and nH oxide consisting of mixed components of the ₂ O titanium gel, titania gel, or a titanium FER oxy gel amorphous oxide of the gold which is called the (Ti-peroxy gel) A film layer is produced. The acid in the mixed solution is not particularly limited, but sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl) and nitric acid (HNO ₃ ), or a mixture of the three acids may be used. However, hydrogen peroxide (H ₂ O ₂ ) can be used.

The concentration of sulfuric acid, hydrochloric acid and nitric acid is preferably 90 to 98% by weight for sulfuric acid solution, 30 to 38% by weight for hydrochloric acid solution, 60 to 90% by weight for nitric acid solution, and the concentration of oxidant is hydrogen peroxide. It is preferred that it is 20-30% by weight.

On the other hand, since the crystal structure and formation rate of, for example, titanium peroxygel produced on the titanium-based metal surface in accordance with the mixing ratio of the acid and the oxidizing agent in the mixed solution used are slightly different, the amorphous oxidation in the production method It is preferable that the mixing volume ratio of the acid and the oxidant in the mixed solution used for forming the coating layer is 1: 3 to 1: 1.

When the acid is present in the mixed solution used to form the oxide film layer of the mixed phase in excess of the ratio, the growth rate of the titanium peroxygel oxide film is delayed, and when the oxidant is present in excess of the ratio, There is a problem that the efficiency of the photocatalyst is lowered because the efficiency of transition to the TiO ₂ crystal structure is lowered.

For example, to form an oxide film of the titanium peroxygel, sulfuric acid (H ₂ SO ₄ , concentration 95%, specific gravity 1.83) is added as an acid and hydrogen peroxide (H ₂ O ₂ , concentration 30%) is added as an oxidizing agent. When using a mixed solution, the thickness of the film produced in this process should be formed at least 500 nm, it is possible to secure the thickness of the TiO ₂ photocatalyst necessary for the efficient photocatalyst through the subsequent heat treatment process.

 In addition, since the crystal structure and the production rate of the oxide film layer is slightly different depending on the immersion time of the mixed solution used, the immersion time for forming the amorphous oxide film layer in the production method is preferably 2 to 40 hours. .

If the immersion time is shorter than 2 hours, the thickness of the resulting oxide film is too thin to have a problem of efficiency of the photocatalyst, and if it is longer than 40 hours, the thickness of the film is too thick, causing a problem of peeling from the base metal.

1 is a diagram showing the surface structure and cross-sectional structure of a titanium peroxygel film having a thickness of about 3 μm generated in a mixed solution containing sulfuric acid and an oxidizing agent in the method for preparing a titanium oxide photocatalyst according to the present invention. It can be seen that the gel film was produced by being in close contact with titanium, the base metal.

Figure 2 shows the XRD measurement results of the crystal structure of the titanium peroxygel film produced in the mixed solution of sulfuric acid and oxidizing agent in the method for producing a titanium oxide photocatalyst according to the present invention, referring to FIG. The immersion in the mixed solution did not show any particular crystal structure of the oxide film, but rutile and anatase components, which are crystal structures of titanium dioxide, were slightly mixed.As described above, the mixture ratio and immersion time in the mixed solution of acid and oxidant As a result, the ratio of the finely formed TiO ₂ crystal structures differs slightly, but the oxide film of most peroxygels shows an amorphous structure.

The film of titanium oxide gel formed by oxidation reaction with sulfuric acid and additives has very good adhesion with titanium as a base metal even at a certain film thickness, but since it does not show a complete crystal structure of TiO ₂ , it cannot be used as a photocatalyst. The process of changing the oxide film of titanium peroxygel to titanium dioxide crystals (anatase, rutile) is required, and the temperature of the step of heat-treating the titanium metal on which the amorphous oxide film layer is formed in the manufacturing method It is preferable that is 400 degreeC-800 degreeC.

FIG. 3 shows the XRD measurement results of the crystal structure of the fibrous TiO ₂ photocatalyst film formed by a combination of a chemical oxidation promoting reaction and a heat treatment in the method of preparing a titanium oxide photocatalyst according to the present invention. Referring to FIG. As described above, the type of crystalline titanium dioxide used in the photocatalytic reaction can be classified into two types, anatase and rutile. In the case where the heat treatment temperature is low, that is, 400 ° C to 500 ° C In the case of heat treatment at, most stable anatase crystal forms are formed at low temperatures, and rutile crystals are formed at high temperatures at 700 ° C. to 800 ° C. Therefore, when the temperature of the heat treatment step is less than 400 ℃ there is a problem that the crystals of the anatase and rutile form is not formed, if the temperature is higher than 800 ℃ because the high temperature oxidation proceeds rapidly, the film is likely to be peeled off easily restricted to use as photocatalyst There is a problem of receiving. The time of the heat treatment step in the manufacturing method is not particularly limited, but is preferably 30 minutes to 2 hours.

If the time of the heat treatment step is less than 30 minutes it is difficult to change to the crystal structure of anatase or rutile, if greater than 2 hours there is a problem of excessive surface oxidation.

Among the above-mentioned two types of crystal forms of titanium dioxide, the efficiency as a photocatalyst is known to be slightly better than that of rutile crystals, but rutile crystals can be produced even at a high heat treatment time at high temperatures. There is also an advantageous side.

In the manufacturing method of the titanium oxide photocatalyst according to the present invention, the material type of the titanium-based metal is not particularly limited, but it is preferable that it is a plate, network, three-dimensional structure or fiber, and in the case of fiber, the diameter is 10 μm to 1 It is preferable that it is mm. If the diameter of the titanium material is less than 10 ㎛, the breakage of the material occurs in the manufacturing process, when larger than 1 mm can not be expected to improve the specific surface area of the advantage of the fibrous material.

Figure 4 shows a photo of one embodiment of the fibrous TiO ₂ photocatalyst shape prepared by the present invention in the method for producing a titanium oxide photocatalyst according to the present invention.

The titanium oxide photocatalyst is used for removing heavy metals, preventing self-cleaning and antifogging due to superhydrophilicity, blocking UV rays, using amphiphilic properties, photolysis of water using sunlight, water purification, odor removal, and air purifiers. In addition, it can be used in various fields such as valuable precious metal recovery, antibacterial and sterilization, and especially can be used for water purification, deodorization, air purifier, valuable precious metal recovery, antibacterial and sterilization.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments, but the following examples are for the purpose of explanation and are not intended to limit the invention.

Example

The organic and inorganic reagents required for the preparation were purified by standard methods from Aldrich or Fluka, and used an X-ray diffractometer to confirm the crystal structure of the titanium oxide film. The incident angle was fixed at 1.5 degrees and 2θ was measured in the range of 20 to 80 degrees.

 (1) washing stage

The base metal for preparing the titanium oxide photocatalyst may be in pure form or may be in the form of an alloy. The base metal may be any shape as well as a fiber, but in this embodiment, 95 wt% titanium 40 g of 150 μm commercial fibrous titanium was treated with hydrofluoric acid (48% HF, manufactured by Aldrich) and nitric acid (HNO _3). HF: HNO ₃ using a mixed solution of 70% Aldrich) It was washed for about 1 to 2 minutes in a washing solution in which the volume ratio of H ₂ O was 1: 1: 1.5.

(2) Immersion stage

The washed titanium-containing metal is sulfuric acid (H ₂ SO _{4 ,} concentration 95%, specific gravity 1.83, manufactured by Aldrich) and hydrogen peroxide (H ₂ O _{2 ,} concentration 30%, manufactured by Aldrich) 1: 10 in a mixed solution of 3 volume ratio It was immersed for a time to form an amorphous oxide layer on the titanium metal surface. The temperature of the mixed solution was 35-45 ^o C, and the film formed after immersion was fixed at an incident angle of 1.5 degrees with an X-ray diffraction and 2θ was measured and analyzed in the range of 20 to 80 degrees.

(3) heat treatment step

The titanium metal on which the mixed oxide layer was formed was heat-treated at 650 ° C. for 1 hour. After the heat treatment, the crystal structure of the TiO ₂ photocatalyst oxide film was measured using an X-ray diffractometer. X-ray analysis of the oxide film (titanium peroxygel) formed on the titanium metal surface after the immersion step showed some rutile and anatase components, but mainly showed diffraction peaks of titanium, which is a component of the titanium base metal. As a result, it was found that the oxide film on the surface was mostly amorphous (see FIG. 2). The film thickness of titanium peroxy gel was about 3 micrometers.

A fiber-type titanium material in which titanium peroxy gel was formed on a titanium film by immersion in a mixed solution of hydrogen peroxide could be transformed into a crystalline titanium dioxide structure that can react as a photocatalyst through heat treatment. X-ray analysis of the oxide film formed on the metal surface after the heat treatment step revealed that the anatase structure, which is a high-temperature crystal of titanium dioxide capable of photocatalytic reaction, was formed on the fibrous titanium surface in close contact with titanium, the base metal, and a little rutile. It was found that the crystals were also mixed (see FIG. 3). The peak of titanium in the X-ray analysis of the oxide film after the heat treatment step was due to the detection of the titanium metal component present in the inside of the fibrous form, and through the analysis of the crystal structure of FIG. It was found that the TiO ₂ photocatalyst exhibited a suitable structure for the action of the photocatalyst. 4 shows a photograph of the shape of the fibrous TiO ₂ photocatalyst prepared by the above method.

Result of decomposition reaction of aniline blue dye

In order to investigate the efficiency of the fibrous titanium dioxide photocatalyst prepared by the method of the present invention, the dye decomposition efficiency of the photocatalyst was investigated.

The photolysis reaction experiment was performed by spreading 2.5 g of a 150 μm fibrous TiO ₂ photocatalyst prepared by the method of the present invention on the bottom of a cylindrical Pyrex glass reactor (Φ = 7.0 cm, h = 2.0 cm), and 0.01 mM aniline blue. After adding 40 mL of a solution (pH 4.0, Fluka), the photolysis efficiency was measured at 25 ° C using a high pressure mercury lamp (100 W) as a light source. At this time, the decomposition concentration of aniline blue was UV / Vis. A spectrophotometer (Unicam 8700) was used to measure the absorbance at 600 nm, which differs depending on the amount of dye decomposition, and was then converted into dye degradation rate.

As a result of measuring the photodegradation effect of the dye, the degradation rate of the dye was 14.86% for 1 hour, 31% for 2 hours, and 60% for 6 hours. This photocatalytic efficiency is very good, and if the amount of sample to be injected during the photocatalytic decomposition efficiency test is increased, the dye decomposition efficiency will be further improved.

According to the present invention, it is possible to mass-produce and produce various types of titanium oxide photocatalyst by a simple process combining chemical treatment and heat treatment, and the prepared titanium oxide photocatalyst may have excellent adhesion between the base metal and titanium oxide. In addition, the photocatalytic efficiency is very high. Titanium oxide photocatalyst according to the present invention can exhibit an excellent effect as a catalyst in various fields such as for various air cleaners, air purification, water purification, wastewater treatment, sterilization and antibacterial.

Claims (7)

A method of producing a titanium oxide photocatalyst having a crystalline titanium dioxide film, Washing the titanium metal; Immersing the washed surface of the titanium metal in a mixed solution of an acid and an oxidizing agent to form an oxide layer of an amorphous and crystalline mixed phase; And Heat-treating the titanium metal on which the oxide layer of the mixed phase is formed Titanium oxide photocatalyst production method comprising. The method of claim 1, wherein the titanium-based metal is selected from the group consisting of titanium, aluminum (Al), vanadium (V), zirconium (Zr), niobium (Nb), nickel (Ni) and molybdenum (Mo). A titanium alloy with at least one metal, the titanium alloy having a titanium content of at least 80% by weight and less than 100% by weight; Or titanium oxide photocatalyst production method, characterized in that the pure titanium. The washing solution of claim 1, wherein the washing solution is a mixed solution of 30 to 49 wt% hydrofluoric acid (HF) solution, 50 to 70 wt% nitric acid (HNO ₃ ) solution and water, and the mixed volume ratio is hydrofluoric acid. Nitric acid is a ratio of 0.5 to 2 with respect to the volume ratio of 1, water is a method of producing a titanium oxide photocatalyst, characterized in that the ratio of 1.0 to 3. According to claim 1, wherein the acid in the mixed solution used to form the oxide film layer of the amorphous and crystalline mixed phase is 90 to 98% by weight of sulfuric acid (H ₂ SO ₄ ), 30 to 38% by weight of hydrochloric acid (HCl) and Nitric acid (HNO ₃ ) at a concentration of 60 to 90% by weight, or a mixture thereof, and the oxidizing agent is hydrogen peroxide (H ₂ O ₂ ) at a concentration of 20 to 30% by weight. The method of claim 1, wherein the mixing volume ratio of the acid and the oxidizing agent is 1: 3 to 1: 1, and the immersion time in the mixed solution is 2 to 40 hours. The method of claim 1, wherein the temperature of the heat treatment step is 400 ° C. to 800 ° C., and the heat treatment time is 30 minutes to 2 hours. The method of claim 1, wherein the titanium-based metal material is in the form of a plate, a network, a three-dimensional structure, or a fiber having a diameter of 10 µm to 1 mm.

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