JPH0596181A - Photocatalyst - Google Patents

Abstract

PURPOSE:To obtain a photocatalyst which can be used for photolysis of waste water, org. soln. etc., and can be easily dispersed and recovered by embedding and depositing a semiconductor photocatalyst uniformly on the surface of a synthetic resin powder body with impact force. CONSTITUTION:A semiconductor photocatalyst (e.g. titanium oxide) is uniformly embedded and deposited on the surface of a synthetic resin (e.g. polyethylene) powder body by impact force, using a ball mill or the like. This photocatalyst can be used for various photolyses. Especially, when this photocatalyst is used for harmful matters such as hydrocarbon halides, organophosphrous agricultural chemicals, etc., it can change these harmful matters into harmless ones with good efficiency in an industrial scale, which is useful for environmental preservation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst used for photodecomposition reaction of waste water, organic matter solution and the like.

[0002]

2. Description of the Related Art In recent years, attention has been paid to attempts to photolyze water, halogenated hydrocarbons, phenols, surfactants, organophosphorus pesticides and the like using a semiconductor catalyst such as titanium oxide or strontium titanate. Since the semiconductor photocatalyst used for this has a large specific surface area and high efficiency, an average particle size of 1
A fine particle having a particle size of μ or less is used, and it is decomposed by adding it to a liquid to be decomposed and irradiating it with a light source such as a mercury lamp.

[0003]

However, the conventional semiconductor catalyst having a fine particle size has a strong cohesive force, and when coagulating, the light receiving area becomes small and the efficiency is lowered. Had to let. In addition, there are problems that the catalyst adheres to the wall of the vessel and filtration becomes difficult, which hinders the recovery of the catalyst, and the aggregation of the catalyst has been a major obstacle in attempting to carry it out on an industrial scale. The present invention has been made to improve such problems, and an object thereof is to provide a photocatalyst that does not cause aggregation and is easily dispersed and recovered.

[0004]

SUMMARY OF THE INVENTION The present invention provides a photocatalyst for solving the above-mentioned problems, and the gist thereof is to embed a semiconductor catalyst uniformly on the surface of a synthetic resin powder by impact force to adhere the same. The thing is to use a photocatalyst. With such a structure, agglomeration does not occur at all, and since the apparent specific gravity is small, it can be easily dispersed in the liquid, the adhesion to the device is eliminated, and recovery is facilitated. occured.

The semiconductor catalyst is embedded in the surface of the synthetic resin powder by impact force, and the synthetic resin is preferably a thermoplastic resin such as polyethylene, polypropylene, polystyrene, polyamide, polymethylmethacrylate. It is better to select a material that is not affected by the decomposition target substance and decomposition products. For example, polyamide is suitable for chlorine-based solvents such as trichloroethane and tetrachloroethylene.

To attach the semiconductor catalyst to these powders by impact force, specifically, it is possible to sufficiently mix the synthetic resin powder and the semiconductor catalyst with a ball mill or the like. Particularly preferably, a device such as a hybridization system manufactured by Nara Machinery Co., Ltd. or a mechanofusion system manufactured by Hosokawa Micron Co., Ltd. is used. The object can be easily obtained by these devices. If the average particle size of the synthetic resin powder is too large, the efficiency decreases, so 1 mm or less is preferable. The shape is spherical, rod-shaped,
It is not limited to a needle shape or an irregular shape.

Semiconductor catalysts used as photocatalysts include titanium oxide, strontium titanate, cadmium sulfide,
Zinc oxide, cadmium telluride, cadmium selenide,
Examples thereof include silicon, tungsten oxide, iron oxide, molybdenum sulfide, etc., which are selected according to the purpose. For example, titanium oxide, strontium titanate, cadmium sulfide, zinc oxide and the like are suitable for decomposing water to obtain hydrogen and oxygen, and titanium oxide and tungsten oxide are suitable for decomposing chlorine-based solvents. In addition, platinum or ruthenium oxide may be supported on these catalysts in order to increase the catalyst efficiency. The present invention can be applied to any of the above catalysts.

[0008]

In general, when the photocatalyst is attached to the surface of the carrier, the contact area is reduced and the efficiency is expected to decrease. However, it was surprisingly found that the photocatalyst of the present invention does not cause any decrease in efficiency. The reason for this is not clear, but it is speculated that one of the factors is that a minute gap is created between the semiconductor powder and the synthetic resin powder due to the mechanical embedding of the semiconductor, and the liquid enters from there. .. Further, when the photocatalyst of the present invention is used, dispersion in the liquid becomes good, and photolysis can be efficiently performed,
Moreover, the catalyst can be easily separated from the liquid.

[0009]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. Reference example Fine particle size high purity titanium oxide (TP manufactured by Fuji Titanium Industry Co., Ltd.)
-2. 10 g of average particle size 0.3 μ) and polyamide powder (DAIAMIDE VESTOSINT 1111 manufactured by Daicel Hüls KK).
190 g of which the average particle size is 100 μ) is mixed and supplied to the hybridization system NHS-1 type manufactured by Nara Machinery Co., Ltd., and the device is dispersed at 5600 rp while being dispersed in the gas phase.
After being operated for 5 minutes at m. and subjected to impact, a polyamide having the surface completely covered with titanium oxide was obtained. This composite will contain 5% by weight of titanium oxide. This was used as a photocatalyst in the following examples.

Example 1 2500 ml of 1000 ppm aqueous solution of trichlorethylene was placed in a 3-liter three-necked flask, 50 g of the photocatalyst obtained in Reference Example (including 2.5 g of titanium oxide) was charged, and an electric stirrer and a water-cooled condenser were equipped. Then, while stirring, irradiation was carried out from the bottom of the flask with a 125 W mercury lamp from a distance of 20 mm for photolysis. PH dropped from 6.2 in the initial stage to 2.7 after 3 hours because of hydrogen chloride generated.

When the concentration of trichlorethylene in the liquid was analyzed by gas chromatography, it was 210 pp after 3 hours.
It was 50 ppm after 24 hours. Stirring speed 1
When the experiment was carried out by changing the range from 00 to 800 ppm, the catalyst was not settled and adhered to the vessel wall even at a low speed, and the same decomposition result was obtained. Further, when filtration was carried out using a filter paper to separate the catalyst from the aqueous solution, the filter paper could be smoothly separated without being clogged.

Example 2 An experiment was conducted in the same manner as in Example 1 except that tetrachloroethylene was used instead of trichlorethylene. PH dropped from 6.2 at the beginning to 2.4 after 9 hours. The tetrachloroethylene concentration was 200 ppm after 9 hours and 70 ppm after 24 hours. Stirring speed 100-80
When the experiment was carried out by changing the range of 0 rpm, no decomposition of the catalyst or deposition on the vessel wall was observed even at a low speed, and a similar decomposition rate was obtained. Further, when filtration was carried out using a filter paper to separate the catalyst from the aqueous solution, the filter paper could be smoothly separated without being clogged.

Comparative Example 2. As a photocatalyst, fine particle size high-purity titanium oxide (TP-2 manufactured by Fuji Titanium Industry Co., Ltd .; average particle size 0.3 μ) itself was used.
The same procedure as in Example 1 was carried out except that 5 g was used. If the stirring speed was not 600 rpm or more, the catalyst aggregated and settled, and the decomposition speed decreased. The decomposition rate without sedimentation was the same as in Example 1. An attempt was made to filter using a filter paper to separate the catalyst from the aqueous solution, but the filter paper was clogged and it was very difficult to separate by filtration.

[0014]

INDUSTRIAL APPLICABILITY The photocatalyst of the present invention can be utilized for various photodecomposition reactions, but when applied to harmful substances such as halogenated hydrocarbons and organophosphorus pesticides, it can be effectively detoxified on an industrial scale. It is very useful for environmental protection.

Claims (2)

[Claims] 1. A photocatalyst characterized in that a semiconductor photocatalyst is uniformly embedded and attached to the surface of a synthetic resin powder by impact force. 2. The synthetic resin is a thermoplastic resin.
The photocatalyst described.