WO2005047185A1

WO2005047185A1 - Photocatalyst composition and preparing method thereof

Info

Publication number: WO2005047185A1
Application number: PCT/KR2003/002546
Authority: WO
Inventors: Cheong-Sik Jeong
Original assignee: Cpc Co., Ltd
Priority date: 2003-11-14
Filing date: 2003-11-25
Publication date: 2005-05-26
Also published as: KR100611632B1; AU2003282430A8; KR20050046846A; AU2003282430A1

Abstract

The present invention relates to a method for preparing a photocatalyst composition which is comprised of following steps: adding base to water solution of titanium isopropoxide and discarding supernatant ; adding acid to the obtained solution and stirring , adding base to neutralize solution, adding selenium sol to the resulting titanium dioxide sol and mixing; and heating mixed sol for drying.

Description

PHOTOCATALYST COMPOSITION AND PREPARING

METHOD THEREOF

BACKGROUND OF THE INVENTION

1. Field of the Invention The present invention relates to a photocatalyst composition and a preparing method thereof which have an excellent photocatalyst function even in a natural light and indoor light.

2. Description of the Background Art When a light having energy above band gap is irradiated to a metallic material having a semiconductor property, oxidation and reduction reactions occur in surrounding organic compounds. Here, a photocatalyst material having a property of semiconductor is referred to as a photocatalyst agent. For obtaining the above photocatalyst, there is a method in which a photocatalyst is carried on a substrate using a refractory binding agent by adapting a high molecule as a supporter. Another method is characterized in which a photocatalyst powder is adhered to a substrate of a fluorine group polymer or a silicon polymer and silicon sol of an inorganic group by binder. And, there is a method in which a photocatalyst is obtained from a metallic oxide sol as a carrier of a photocatalyst powder. Recently, an applicable range of the photocatalyst is sharply increased. Namely, the above photocatalyst is adapted in home, office and various industrial fields. The use of the photocatalyst is rapidly spread. Photocatalyst is used for decomposition of harmful substances to a human body and bad smells. It is also used for prevention of sliding in a public bath room, removal of smell component, purification of indoor air, removal of bad smell in the interior of a vehicle, or prevention of bacteria propagation in a food factory, etc. However, it is needed to implement the properties that photocatalyst particles are strongly adhered on a substrate, maintaining an inherent function of the photocatalyst and a long time efficacy of the same. In the case that an organic high molecule is adapted as a supporter of a photocatalyst, a semiconductor photocatalyst may receive a certain energy level above the energy of the band gap, so that the organic materials may be continuously and gradually oxidized and decomposed. Therefore, the efficacy of the same is very short, and it is impossible to implement a desired effect, so that a consumer is not satisfied. In addition, when rutile type photocatalyst or anatase type photocatalyst is coated on a substrate by spray or brush method using an organic group as a binder and inorganic silicon group polymer as a supporter and dried thereon, a certain crack may occur due to the binding of particles during a drying process or the surface of the catalyst may be rough.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a photocatalyst composition and a manufacturing method thereof which overcome the problems encountered in the conventional art. It is another object of the present invention to provide a photocatalyst composition and a manufacturing method thereof which are capable of implementing a strong adhering force on the surface of a substrate without damaging the particles of a photocatalyst and the inherent functions of a photocatalyst. It is another object of the present invention to provide a photocatalyst composition and a manufacturing method thereof which are capable of implementing a long time efficacy of the photocatalyst. To achieve the above objects, there is provided a method for preparing a photocatalyst composition which is comprised of following steps: adding base to water solution of titanium isopropoxide and discarding supernatant ; adding acid to the obtaind solution and stirring , adding base to neutralize solution, adding selenium sol to the resulting titanium dioxide sol and mixing; and heating mixed sol for drying. In the present invention, it is possible to implement a uniform thin film coating process having a desired adherence without crystallization by a titanium dioxide and a crack during a drying process. Layers are separated by neutralization using an alkali property contained in NaOH, KOH, NaHC0 , ammonia water, etc. in a titanium aqueous solution like Ti((OCH ((^3)₂)₄, as a layer separation agent of a photocatalyst sol adapted in the present invention. Here, a separated supernatant has a base component. The supernatant is washed multiple times using distilled water thus discarding a base. The distilled water is added 1 or 3 times based on the volume of a precipitated agent, and a solid value is obtained based on the added amount of the distilled water. Here, HN0₃ solution is slowly added by 1 ,000ppm(0.1%) and is strongly agitated by high-speed agitator for 30 minutes thus obtaining pH of 1-2. In order to adjust color and pH of neutrality, NaOH, KOH, NaHC0₃, or ammonia water may be added in an aqueous solution within a range of 0.2% thus obtaining a neutral pH of 7-8. The obtained material is heated at above 100°C for more than 30 minutes, and then the crystal titanium dioxide sol of the anatase type is obtained. The photocatalyst is coated on a ceramic and is dried and heated to 400°C. As a result, the titanium dioxide of the anatase type is obtained. At this time, the titanium dioxide sol of the anatase type has a grain diameter of below 5-20nm, and pH is 7-8, and the outer appearance is white transparent color. As a component of the binder adapted in the present invention, there are Se, Co, Ce0₃, Ta20₅, Ru0₂, InPb, MoS₃₎ MoS₂, Sa0₂, Zno, SrTi0₃, CdS, CdO, CaP, Ti0₂, Si0₂, SiC, Ca, Fe, Mn, Mg, etc. Among the above components, a transparent selenium sol has an excellent adherence on the surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments and references of the present invention will be described in detail. The scope of the present invention is not limited to the following examples.

[Example 1] Preparation of titania sol

In a high speed agitator, a distilled water of 12L was added to Titanium isopropoxide of 1kg, agitating for 10min and white solution was obtained. 300ml of NaOH solution (40%, supplied by Yongjin chemical corporation) was added and stirred for 5min at the speed of 60rpm. After confirming the layer was separated, the water residing in the upper layer of the solution was discarded. Supernatant was fully washed with silver nitrate solution of 1mol until chlorine contained in the supernatant was not detected thus obtaining 2,000ml of gel. The resultant solution was diluted with nitric acid (70%) supplied by Dongyang chemical corporation, and a solid value was freely controlled based on the ratio of the diluted nitric solution, thus obtaining a stable aqueous dispersion of about 5,000ml which has at least 10% of solid value.

[Example 2] Preparation of inorganic binder A distilled water of 30ml was added to a solution of a nitric acid (70% ) of 100 ml supplied by Dongyang chemical corporation thus preparing diluted HN0₃ solution. Se of 13g was added to diluted HN0₃. The resultant solution was neutralized with KOH (30%) solution supplied by Duksan chemical corporation, and pH was adjusted to 8-9. The pH was fixed at 7.5-8 using lactic acid for preventing a layer separation, and the solid value was adjusted using distilled water. It was preferred that the solid component does not exceed 3% of the solid content of photocatalyst when it is used as a binder for a photocatalyst according to the present invention.

[Example 3] Preparation of photocatalyst composition The inorganic binder prepared by the example 2 was mixed with a photocatalyst and was heated at below 100°C within 10 minutes thus preparing an anatase type titanium dioxide. The photocatalyst sol of transparent white color was obtained.

[Experimental example 1] The decomposition force test for the organic materials of the photocatalyst sol of the example 3 including the inorganic binder was implemented based on the following methods. A cubic box was formed by plastic material in size of 2m³. A 20W UV fluorescent light was attached to each rectangular corner of the box. A bad smell gas (for example, ammonia, SOx, NOx, etc.) of 2,000ppm was injected into the box one time for every one minute for 24 hours totally 1 ,440 times using a pump. Photocatalyst sol containing inorganic binder was injected for 1 minute by 10CC using an air spray gun by a compressor for removing particles of the bad smell gas. Thereafter, a smell removing ability was checked one time for every hour. As a result of the above processes for researching and checking the efficiency of the removal of the bad smell gas, photocatalyst sol containing inorganic binder was proved to be capable of decomposing organic materials completely only in 1 minute.

[Experimental example 2] The decrease rate of the bacteria was checked with respect to the strain 1 of Staphylococcus aureus having an initial number of bacteria of 1.3x10⁶ after 24 hours based on FC-TM-20 in the antimicrobial susceptibility test. As a result of the check, an extinction ability of 99.9% was obtained. In addition, the decrease rate of the bacteria was checked with respect to the strain 2 of the Escherichia coli having an initial number of bacteria of 1.5x10⁴ after 24 hours based on the same manner. As a result of the check, an extinction ability of 99.9% was obtained.

[Experimental example 3] A photocatalyst sol was adjusted to solid value of 1% using distilled water and was fully diluted and sprayed on a transparent glass test sample having a dimension of 10cmx5.5cmx5cm using a spray, so that a coating layer having a thickness of 1μm~2μm was formed thereon. Thereafter, an adhering strength test was performed with respect to the resultant coating layer under a natural environment at a room temperature through 200°C. [Adhering strength test 1] A photocatalyst having water was placed indoor at a room temperature of 15°C for 2 hours. The water contained in the photocatalyst was fully evaporated. It was visually checked that a rainbow was outputted from a glass test sample coated with a photocatalyst, viewing the same in a lateral direction. In addition, the strength of the glass test sample coated with the photocatalyst was tested using a 4H pencil. As a result of the test, there was not any scratch on the glass test sample.

[Adhering strength test 2] The above glass test sample was coated using a spray at a room temperature, and water contained in the glass test sample was evaporated at a temperature of 50°C. The strength of the glass test sample coated with a photocatalyst was tested using a 4H pencil. As a result of the test, there was not any scratch on the glass test sample.

[Adhering strength test 3] The glass test sample was coated using a spray at a room temperature, and water contained in the glass test sample was evaporated for 5 minutes at a temperature of 50°C and was heated for 10 minutes at a temperature of 100°C. The strength of the glass test sample coated with the photocatalyst was tested using a 4H pencil. As a result of the test, there was not any scratch on the glass test sample. In order to test the adherence of the photocatalyst on the surface, the strength of the glass test sample coated with the photocatalyst was tested using a 4H pencil. As a result of the test, there was not any scratch on the surface of the same. In addition, the glass test sample coated with the photocatalyst was rubbed 50 times with a common towel using a neutral detergent having a density of 1.OOOpprn for performing an adhesive force test on the surface. As a result of the test, it was possible to obtain the same result as the original state.

[Experimental example 4] In order to perform a storing property test with respect to a photocatalyst sol having an inorganic binder, the photocatalyst sol was inputted into an ample bottle having a volume of 100CC by 50CC and was frozen in a freezing room of a common environment for 24 hours at -5°C. A resultant sol was placed at a room temperature for 3 hours. Thereafter, the state of the recoupling of the nano-size particles was visually checked. The conventional local products and conventional Japanese products each having pH value of 7-8 were frozen or defrozen. As a result of the above process, when the particles were recoupled, the products were damaged, so that there was not any value as a product. However, in the case of the products according to the present invention, when it was frozen and defrozen multiple times, it was possible to visually check no changes in the products. Therefore, even when the products according to the present invention are frozen by mistake during the transportation of the products, there will be no problems in the products. Hence, it is possible to sell and use the products without any damages. As described above, in the preparing method of the present invention, it is possible to prepare a photocatalyst composition having a good adhering property, spreading property, durability, cold-resistant property, etc. when coating on a surface of a thing without decreasing an inherent function of a photocatalyst. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.

Claims

What was claimed is: 1. A method for preparing a photocatalyst composition which is comprised of following steps: adding base to water solution of titanium isopropoxide and discarding supernatant ; adding acid to the obtaind solution and stirring , adding base to neutralize solution, adding selenium sol to the resulting titanium dioxide sol and mixing; and heating mixed sol for drying.

2. The method of claim 1, wherein the amount of said solid selenium is below 3% of the solid titanium dioxide photocatalyst.

3. The method of claim 1 , wherein mixed sol is heated for 10 - 60 minutes at 100°C for drying.

4. A method for preparing a titania sol which is comprised of following steps: adding base to water solution of titanium isopropoxide and discarding supernatant ; adding acid to the obtaind solution and stirring , adding base to neutralize solution.