JPH11188269A - Photocatalystic body for decomposing organic material, proliferation preventing method of harmful organism using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the proliferation of a small organism such as plankton at a low cost by supporting a photocatalytic body for decomposing organic material on a granular porous carrier and forming so as to enable to float on water surface to decompose organic material while floating on the water surface of lake and marsh, a reservoir sea or the like. SOLUTION: In the case of preventing the proliferation of the small organism to be harmful such as a plankton by using the oxidation decomposition action, which the photocatalyst 1 exhibits, and decomposing the organic material near the water surface 3, the photocatalytic body 4 formed by supporting the photocatalyst 1 on the photocatalyst carrier 2 is floated on the waster surface 3. Then the contact surface area with water is sufficiently secured and the organic material on the vast surface of the lake and marsh is decomposed. As the photocatalyst 1 to be used, any one exhibiting oxidation reduction action by light irradiation is used and for example, titanium oxide, tungsten oxide, zinc oxide are mentioned. The photocatalyst carrier 2 is constituted of a glass molded body, resin, fiber, paper or the like in addition to one formed by making titanium oxide and the like granular and porous.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst for decomposing organic substances and a method for preventing the growth of pests, and more particularly to a photocatalyst for decomposing organic substances which can be suspended on a water surface such as a lake, a reservoir or the sea. The present invention relates to a method for preventing the growth of pests in water by decomposing organic substances using a photocatalyst floating on a water surface such as a reservoir or the sea.

[0002]

2. Description of the Related Art In recent years, organic matter pollution in lakes, marshes, reservoirs or the ocean has become a major problem. In particular, eutrophication of water causes a great deal of damage to pests, such as the occurrence of large quantities of plankton and enormous damage to marine resources, and countermeasures are urgently needed.

[0003] For example, in lakes and marshes, a large amount of pests (blue flour, plankton, also called water blossoms), which are pests, are caught in fish gills and hinder the respiration of fish. It consumes a large amount of oxygen and causes deficiency of oxygen in the water to kill fish and shellfish, causing great damage to marine resources. Furthermore, the abundance of blue-green algae has caused many environmental pollution problems such as lake water pollution and odor.

[0004] In the ocean, the proliferation of plankton due to eutrophication of water causes many problems. Excessive overgrowth of marine plankton has caused enormous damage to marine resources. In particular, power companies are struggling to take countermeasures because jellyfish and the like are generated in large quantities and rush to the water intake of power plants.

[0005] On the other hand, it is known that a photocatalyst such as titanium oxide produces a strong oxidizing action by photocatalytic action when irradiated with light such as sunlight. The organic substance is oxidized and decomposed into carbon dioxide gas and water by the strong oxidizing action, so that the photocatalytic action is applied to the decomposition and sterilization of harmful organic substances.

That is, in the field of water treatment, titanium oxide is suspended in water and exposed to light to decompose organic substances. Attempts have also been made to use glass beads partially coated with a titanium oxide thin film on the sea surface to decompose floating crude oil. Furthermore, an attempt has been made to apply the strong oxidizing action generated by the photocatalyst to the prevention of harmful plankton proliferation. This is a method in which the photocatalyst 1 is fixed to a raft-shaped floating body 12 and floated on the water surface 3, as shown in FIG.

However, in the method of directly suspending titanium oxide in water, it is difficult to maintain the suspended state for a long period of time due to sedimentation or absorption by aquatic organisms. There were problems such as being unable to float only near the surface of water that could reach it. In addition, those in which a titanium oxide thin film is partially applied on glass beads have problems that the contact area with water is small and the cost is high.

[0008] In addition, a photocatalyst fixed to a raft-like floating body and floated on the water surface has a problem that it takes a great deal of cost to cover a vast lake surface. That is, as shown in FIG. 7, the use of the raft-shaped floating body 12 requires a material that transmits ultraviolet light well, so that the range of material selection is limited and the cost is high. It took some effort to collect them.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a method for decomposing an organic substance by using a strong oxidative decomposition action of an organic substance, which is exhibited by a photocatalyst, and for preventing the growth of harmful small organisms such as plankton. Solve the problems in the technology, stably float the photocatalyst near the water surface irradiated with light, ensure sufficient contact area with water,
In addition, a photocatalyst for decomposing organic substances, which enables organic substances to be decomposed by floating the photocatalysts on a vast lake surface to prevent the growth of harmful plankton and other small organisms at low cost, and An object of the present invention is to provide a method for preventing the growth of pests using a photocatalyst.

[0010]

According to a first aspect of the present invention, there is provided a photocatalyst for decomposing an organic substance, wherein a photocatalyst is supported on a granular porous carrier, and is capable of floating on a water surface. It is. Further, the method for preventing the growth of water surface pests according to claim 3 of the present invention is characterized in that a photocatalyst capable of floating on the water surface, which is obtained by supporting a photocatalyst on a granular and porous carrier, is dispersed and floated on the water surface. Is what you do.

FIG. 1 is a diagram schematically showing a photocatalyst of the present invention. A photocatalyst 4 having a photocatalyst 1 carried on a photocatalyst carrier 2 is floated on a water surface 3. According to the present invention, by using the strong oxidative decomposition action exhibited by the photocatalyst, decompose organic matter near the water surface, and in the case of preventing the growth of small organisms such as harmful plankton, solving the above-mentioned problems in the prior art. , While stably floating the photocatalyst near the surface of the water to be irradiated with light, and ensuring a sufficient contact area with water,
In addition, organic substances can be decomposed on a vast lake surface to prevent the growth of harmful small organisms such as plankton at low cost. As the photocatalyst in the present invention, any substance can be used as long as it exhibits a redox action by light irradiation. For example, various photocatalytic substances such as titanium oxide, tungsten oxide, zinc oxide and strontium titanate can be used. .

Among these, titanium oxide is particularly excellent in terms of photocatalytic activity, has the advantage of having catalytic activity against sunlight, is chemically stable, has abundant resources and is inexpensive. Moreover, it is particularly desirable as a photocatalyst of the present invention because it has features such as being non-polluting.

Titanium oxide has an anatase-type crystal structure and a rutile-type crystal structure, and high photocatalytic activity is observed in the oxidized anatase type. Therefore, in order to obtain high photocatalytic activity, it is desirable to use a material containing at least titanium oxide having an anatase type crystal structure.

The particulate and porous photocatalyst carrier of the present invention is preferably a material which does not cause environmental pollution even when sprayed on the water surface. From such a point of view, as the granular and porous photocatalyst carrier of the present invention, in addition to a granular and porous photocatalyst such as titanium oxide, in addition to a coal ash molded body described in detail below, glass molding A molded article made of a body, resin, fiber, paper, etc. and free from environmental pollution can be suitably used.

[0015] Of these, porous bodies containing coal ash are particularly desirable for the following reasons. In other words, coal ash contains silica and alumina as main components and further contains calcium oxide, and its composition is close to natural minerals such as pearlite, and is chemically stable, and is oxidized and deteriorated by a photocatalyst. Nothing.

As the granular porous carrier containing coal ash used in the present invention, those having a calcium phosphate compound on at least the surface can be desirably used. Since coal ash has calcium oxide as a component thereof, it is treated with phosphoric acid to produce a calcium phosphate compound such as hydroxyapatite which is a calcium phosphate compound. Since such a compound has affinity for a living body, the use of such a carrier can effectively prevent the growth of pests by the photocatalytic carrier. Coal ash, unlike incinerated ash from general waste, has less harmful components such as heavy metals, so there is no concern about environmental pollution. In addition, coal ash from the same coal production area and the same combustion furnace has stable quality,
There is a feature that molding and loading of a photocatalyst can be stably performed with good reproducibility.

A porous body containing coal ash as a main component and capable of floating in water can be easily manufactured by, for example, press molding or extrusion molding using a mold. The coal ash porous molded body has already been applied to an exhaust gas desulfurization device of a thermal power plant, and has been proved to be excellent in economic efficiency. Millions of tons of coal ash are discharged annually, and about half of it is effectively used as a raw material for cement, but the rest is disposed of in landfills, and it is desired to use it effectively.

As the granular and porous photocatalyst of the present invention, a photocatalyst capable of floating on the water surface when loaded into water with a photocatalyst supported thereon is used. In order to be able to float, it is necessary that the effective specific gravity is smaller than that of lake water or sea water. For this purpose, the true specific gravity of the material constituting the carrier is made smaller than that of seawater or lake water, or the true specific gravity of the constituent material is large, but by having closed pores inside, In comparison with this, the effective specific gravity is made smaller to allow the photocatalyst to float.

As the photocatalyst of the present invention, as shown in FIG. 2, a photocatalyst carried on a granular carrier can be used. In such a photocatalyst, since the photocatalyst is supported on or near the surface of the carrier, the photocatalyst can act effectively.

As a method of supporting the photocatalyst after forming the granular carrier, for example, the carrier is impregnated with a solution of a raw salt of titanium oxide, and the pH of the solution is increased by adding an alkali to attach the titanium oxide component to the surface of the carrier. And heat-treating it. In addition, a carrier is placed in a heated electric furnace, and for example, an atomized solution of titanium tetraisopropoxide in an organic solvent is vapor-transported into an electric furnace by air, and thermally decomposed on the surface of the carrier to form a film. May be formed.

Further, as shown in FIG. 3, the particulate carrier carrying the photocatalyst of the present invention can be loaded with a photocatalyst by mixing the carrier material before the formation of the particulate carrier. In the case where the photocatalyst is supported in this way, the photocatalyst is firmly supported by the carrier, and thus there is no risk of falling off.

The pH of the thus obtained photocatalyst can be adjusted by treating it with phosphoric acid.

Further, in the present invention, when the photocatalyst is sprayed on the water surface, it is desirable that the water surface scene is not spoiled if possible. From such a viewpoint, in the present invention,
In addition to the above-mentioned molded product, a naturally occurring mineral such as pumice or a natural material made of a plant such as wood can be suitably used by supporting a photocatalyst as a granular and porous photocatalyst carrier.

The photocatalyst of the present invention has a size suitable for being put into water and floating on the water surface. When the particulate carrier supporting the photocatalyst is suspended on the water surface and the organic matter near the water surface or near the water surface is decomposed by the photocatalysis caused by irradiation of light such as sunlight, it is better to make the size relatively small. It is advantageous to increase the ratio of receiving water and the ratio of contact with water. However, in consideration of recovery, the size of the photocatalyst needs to be limited to a size suitable for recovery. From such a viewpoint, the size of the photocatalyst can be appropriately selected.

The method of spraying and floating the photocatalyst on the water surface in the present invention is not limited at all. The method for recovering the photocatalyst is not particularly limited, and can be very easily performed by, for example, using a collecting net or suction-filtrating water containing a carrier near the water surface.

In order to limit the region in which the photocatalyst is floated in the present invention, a simple enclosure such as an oil fence can be provided, for example. In addition, it is also possible to prevent the photocatalyst from moving by suspending the photocatalyst tied to a rope in the form of beads or the like in water and fixing the rope.

In the present invention, the degree of immersion of the photocatalyst from the water surface is preferably such that the photocatalyst is immersed so as to be in good contact with water and is floating to such an extent that light is well irradiated. The adjustment of the immersion depth can be performed by selecting an effective specific gravity of the granular carrier.

The photocatalyst of the present invention can be used by spraying and floating on the surface of water such as lakes, marshes, reservoirs and the ocean. It is particularly effective when used in areas where water tends to be eutrophic. For example, in lakes, marshes, oceans, and the like, they can be used by being scattered and floated with a limited area near the estuary to which eutrophic water flows or near the intake of a power plant. In such a limited area, the amount of the photocatalyst to be suspended can be appropriately selected depending on the pest to be prevented from growing.

[0029]

When the photocatalyst floating on the water surface is irradiated with sunlight, a pair of electrons and holes is generated inside the photocatalyst which is a semiconductor, and the holes generate a very strong oxidizing action. Since the photocatalyst is floating on the water surface, this oxidizing action oxidizes and decomposes organic compounds such as microorganisms existing near the water surface into water and carbon dioxide gas. This decomposition of organic substances can prevent the growth of pests.

In the present invention, since the photocatalyst is directly floating on the water surface, the light is not blocked. Further, since it is porous and in contact with water, the oxidizing action by the photocatalyst is performed through water, and organic substances in the water surface and in water near the water surface are oxidized and decomposed. This prevents the growth of pests. Since all of the photocatalyst carriers are chemically stable, the carriers are not oxidized.

[0031]

Embodiments of the present invention will be described below based on examples.

(Embodiment 1) The size shown in FIG.
A × 1 m aquarium was filled with eutrophic lake water 7. Plankton 11 was observed in this lake. Using an oil fence 9 covering the water tank up to a depth of about 0.7 m from the water surface, the water tank was divided into two minutes. The water tank is designed to irradiate sunlight from sunrise to sunset without interruption as long as there is sunshine, and the water temperature is controlled at 25 ° C. This 2
In one of the divided water tanks, as shown in FIG. 1, a photocatalyst 4 having titanium oxide supported on the surface was floated.

The photocatalyst used here is obtained by first pulverizing and mixing coal ash and pressing it into granules by the process shown in FIG.
A porous carrier in the form of particles suspended in water by heat treatment, impregnated with a solution of titanium chloride, and then added with an alkali to increase the pH of the solution, thereby allowing a titanium oxide component to adhere to the surface of the carrier. Is further heat-treated to support titanium oxide on the surface.

FIG. 5 shows a plankton growth curve on a lake surface in a water tank in this embodiment. In the figure, A is a growth curve on the water surface on which the photocatalyst is suspended, and P is a growth curve on the water surface on which the photocatalyst is not suspended. As shown in this figure, it was confirmed that plankton growth was prevented on the water surface on which the photocatalyst was suspended.

(Example 2) Except that pumice was used as a granular and porous carrier for supporting a photocatalyst and that a titanium oxide was supported on it, a plankton The growth was examined. FIG. 5B shows the result. It was also confirmed that plankton growth was similarly prevented when the photocatalyst was suspended.

(Example 3) Plankton growth was examined in exactly the same manner as in Example 1 except that eutrophicized seawater was used as water to fill the water tank. The presence of micro-organisms was found in this seawater. FIG. 6 shows a plankton growth curve on the sea surface in the water tank. In the figure, D is a growth curve of the sea surface on the side where the photocatalyst is suspended, and Q is a growth curve of the sea surface where the photocatalyst is not suspended. As shown in this figure, it was confirmed that plankton growth was prevented on the water surface on the side where the photocatalysts were suspended even in seawater.

[0037]

According to the present invention, a photocatalyst is supported on a granular and porous carrier so that the photocatalyst can float on the water surface.
This can be floated directly on the water surface, and can be effectively irradiated with light while being in good contact with water. For this reason, the strong oxidizing power of the granular porous photocatalyst acts through water, and organic substances can be effectively decomposed. In addition, the required amount of the photocatalyst can be floated at a required location, and the collection thereof is easy.

Further, in the present invention, the use of a granular porous carrier containing an oxide of silicon and aluminum as a main component, particularly a granular porous carrier containing coal ash, does not pollute the environment. In addition, coal ash, which is waste, can be effectively used, and desirable effects can be obtained not only in terms of economy but also in terms of environmental measures.

Further, in the present invention, by using a natural material as the granular carrier, it is possible to prevent environmental pollution and prevent the growth of pests without impairing the landscape of the water surface.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a state in which a photocatalyst of the present invention is floated on a water surface.

FIG. 2 is a diagram showing a method for producing a granular carrier supporting a photocatalyst.

FIG. 3 is a diagram showing a method for producing a granular carrier supporting a photocatalyst.

FIG. 4 is a diagram showing a configuration of an aquarium according to an embodiment of the present invention.

FIG. 5 is a diagram showing a growth curve of phytoplankton in lake water.

FIG. 6 is a view showing a growth curve of plankton in seawater.

FIG. 7 is a diagram showing a conventional technique in which a photocatalyst is fixed to a raft-shaped floating body and floated on the water surface.

[Explanation of symbols]

Reference Signs List 1 photocatalyst 2 porous photocatalyst carrier 3 water surface 4 photocatalyst body 6 water tank 7 water
8 ... sand and gravel, 9 ... oil fence, 10 ... anchor wire 11 ... plankton 12 ... raft-like floating body

Claims (6)

[Claims] 1. A photocatalyst for decomposing organic substances which can be suspended on a water surface, wherein the photocatalyst is supported on a granular porous carrier. 2. The photocatalyst for decomposing organic substances according to claim 1, wherein a photocatalyst containing titanium oxide is supported on a porous body containing silicon oxide and aluminum oxide as main components. 3. A method for preventing the growth of pests, wherein a photocatalyst capable of floating on a water surface, comprising a particulate porous carrier carrying a photocatalyst, is sprayed and floated on the water surface. 4. The granular porous carrier according to claim 3, wherein the porous carrier is a granular porous carrier containing coal ash.
The method for preventing the growth of pests according to the above. 5. The method for preventing the growth of pests according to claim 3, wherein a calcium phosphate compound is present on at least the surface of the granular porous carrier containing coal ash. 6. The method for preventing the growth of pests according to claim 3, wherein the granular and porous carrier is a natural material.