Photocatalyst and water treatment using the same

Description: TECHNICAL FIELD [Detailed description of the invention]

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INDUSTRIAL APPLICABILITY The present invention relates to a photocatalyst for removing pollutants (organochlorine compounds, etc.) in water by utilizing the oxidizing power of a photocatalyst, and a water treatment method using the photocatalyst, particularly sewage. The present invention relates to an improvement that facilitates the recovery of the photocatalyst after purification.

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[Conventional Techniques] Organochlorine compounds such as trichloroethane and tetrachlorethylene are used in large quantities as degreasing agents and cleaning solutions in various industries, but these organochlorine compounds are harmful to the human body and are produced in drinking water. Environmental pollution such as pollution has become a social problem. Recently, a photocatalytic decomposition method has been actively studied as a method for decomposing this organochlorine compound. This is to decompose by the strong oxidizing power generated when the photocatalyst is irradiated with light, and TiO as a photocatalyst.₂, ZnO, RuO₂, WO₃Etc. are available, but from the viewpoint of safety and stability, TiO₂Is often used.

In this water treatment with a photocatalyst, the point is how to separate and recover the photocatalyst from the treated water while maintaining high contact efficiency between the pollutant and the photocatalyst. For example, when the photocatalyst is used in the powder state, the contact efficiency with pollutants is increased, but the photocatalyst is difficult to settle and the sedimentation basin for separation and recovery is also large.

On the other hand, Japanese Patent Application Laid-Open No. 4-371233 proposes a photocatalyst in which a magnetic substance is encapsulated in a mass and / or a dispersion in nuclear fine particles, and catalyst particles excited by light irradiation are bonded to the surface thereof. doing. Nuclear particles are lumps with a particle size of about 30 to 100 μm formed of a synthetic resin such as nylon 12, and the magnetic material is encapsulated in lumps of 10 to 50 μm, or the granular magnetic material is kneaded in the resin. It is made to disperse. Then, in order to fix the catalyst particles to the nuclear particles, if an adhesive is used, the surface of the photocatalyst is covered with the adhesive. Therefore, the catalyst particles are driven into the surface of the nuclear particles and bonded while maintaining the activity. Is desirable.

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PROBLEM TO BE SOLVED: To solve a problem The photocatalyst shown in JP-A-4-371233 has high contact with treated water and can be easily separated and recovered by an electromagnet, but has the following problems. .. First, the manufacturing process of the photocatalyst is complicated. That is, after producing the nuclear particles containing or dispersing the magnetic material, the catalyst particles must be further driven into the surface by a special device.

Next, nylon 12 and the like disclosed as the material of the nuclear particles are decomposed by the photocatalyst. Therefore, there is a possibility that the catalyst particles are separated from the nuclear particles and flow out, and the function of the photocatalyst is gradually deteriorated. Therefore, the subject of the present invention is that good contact with treated water can be maintained, separation and recovery are easy, the manufacturing process is simple, and stable performance can be maintained for a long period of time without being decomposed by a photocatalyst. An object of the present invention is to provide a photocatalyst and a water treatment method using the photocatalyst.

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Means for Solving the Problems In order to solve the above problems, the present invention uses a fluororesin as a binder for photocatalyst powder, and a magnetic material or a specific gravity for adding a function of separating and recovering from treated water. An adjusting material shall be added to form a fragmented photocatalyst. That is, the photocatalyst of the present invention is formed by mixing, rolling, and cutting a photocatalyst, a magnetic material, a specific gravity adjusting material, and a fluororesin powder into strips.

Fluororesin has excellent chemical resistance and environmental resistance, does not deteriorate due to the strong oxidizing power of the photocatalyst, and has high water resistance because it is hydrophobic. Further, by applying pressure, an arbitrary shape can be formed. Furthermore, the affinity with the photocatalyst is low, and the surface activity of the photocatalyst is less likely to be inhibited by the presence of the fluororesin. Therefore, by mixing and rolling the fluororesin and the photocatalyst powder into, for example, a sheet, and further cutting the powder to form a fine piece, the contact between the treated water and the photocatalyst is good, the activity is high, and the activity is high. A photocatalyst having excellent life reliability can be obtained.

Since the fluororesin can be produced by mixing not only the photocatalyst powder but also any powder or fine particles to produce a molded product, the magnetic powder is added to the photocatalyst to make it magnetic. By holding the photocatalyst, the photocatalyst is stirred and mixed with the treated water containing the pollutant, the photocatalyst is irradiated with light to oxidize and decompose the pollutant, and the photocatalyst is adsorbed by the magnetic separation means to be separated and recovered from the treated water. By adding a specific gravity adjusting material and setting the specific gravity of the photocatalyst to be smaller or larger than that of the treated water, it becomes possible to separate and recover the photocatalyst from the treated water by floating separation or sedimentation separation means.

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BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described. The photocatalyst is composed of a photocatalyst, a magnetic material or a specific gravity adjusting material, and a fluororesin as a binder thereof. First, as a photocatalyst, TiO₂, ZnO, RuO₂, WO₃Etc. are available, but from the viewpoint of environmental safety and life stability, TiO₂Is the most preferable. It is known that the catalytic activity is enhanced by supporting Pt on the surface of the photocatalyst, but a photocatalyst carrying an additive such as a noble metal for improving the activity can also be used in the present invention. , The types of photocatalysts and additives are not limited.

Next, a ferromagnetic material such as ferrite, nickel, or cobalt is used as the magnetic material. Further, as the specific gravity adjusting material, a material having a small specific density such as hollow glass beads is used in the case of floating separation, and a material having a large specific gravity such as solid glass beads or sand particles is used in the case of sedimentation separation. As the fluororesin, for example, polytetrafluoroethylene is suitable.

Using these materials, a photocatalyst is produced as follows. First, a photocatalyst powder (particle size is, for example, 7 to 50 nm) and a magnetic powder (about 100 μm) or a specific gravity adjusting material powder (same tens to several hundreds μm) are mixed. Next, fluororesin powder (particle size is, for example, about 0.3 μm) is added thereto, and the mixture is stirred and mixed again. Then, it is rolled by a roller to form a sheet having a thickness of, for example, about 0.1 to 1.0 mm. Then, this sheet is cut into an appropriate size, for example, about 1 to 10 mm square to obtain a photocatalyst.

The amount of fluororesin as a binder can be selected in the range of 5 to 90%, but in order to secure the amount of photocatalyst directly involved in the decomposition of pollutants, it is desirable to reduce the amount as much as possible within the moldable range. .. In addition, the magnetic material is 1 to 40%, and the specific gravity adjusting material is preferably added so as to have a value close to the specific gravity of water in order to reduce the stirring power of the treated water, but the efficiency of floating or settling is also taken into consideration. Is decided.

FIG. 1 is an enlarged view showing the internal structure of the photocatalyst. The photocatalyst 1 is porous, and fluororesin particles 1a partially bonded to each other form a three-dimensional network-like structure, and the photocatalyst particles 1b and particles 1c of a magnetic material or a specific gravity adjusting material are formed in the gaps thereof. It is held. The affinity between the fluororesin and the magnetic material or the specific gravity adjusting material is low, and the particles 1a to 1c are merely mechanically assembled in the photocatalyst body 1, and the activity of the photocatalyst surface is so inhibited by the fluororesin. Not done.

FIG. 2 is a schematic configuration diagram of a water treatment apparatus provided with magnetic separation means. The treated water containing the organic chlorine compound is guided to the reaction tank 3 by the water supply pump 2, is stirred and mixed with the photocatalyst 1 to which the magnetic material is added by the stirring device 5 driven by the motor 4, and is mixed with the photocatalyst 1 to which the magnetic material is added, and is emitted from the ultraviolet lamp 6 in the tank. Organochlorine compounds are decomposed and removed by a photocatalyst irradiated with light. The purified water is always drained through the three-way solenoid valve 8 leading to the drainage channel 7. At that time, the photocatalyst 1 flowing out of the tank is adsorbed and separated by the magnetic separator 9. The magnetic separator 9 is composed of a cylindrical electromagnet having an electromagnetic coil (not shown) on the outer circumference, and attracts a photocatalyst 1 containing a magnetic material to the inner peripheral wall surface. The adsorbed photocatalyst 1 stops the water supply pump 2 at an appropriate time, switches the three-way solenoid valve 8 to the circulation path 10 side, shuts off the exciting power supply of the magnetic separator 9, and starts the recovery pump 11 to start water. Is circulated counterclockwise in the figure, and is recovered in the reaction vessel 3.

FIG. 3 is a schematic configuration diagram of a water treatment device provided with a floating separation means. The process up to water treatment in the reaction tank 3 is the same as that of the device of FIG. 2, but in the photocatalyst 1 in which the specific gravity is lighter than that of water, for example 0.9, by adding a specific gravity adjusting material, purified water floats in the separation tank. When passing through 12, it floats on the ceiling and is separated. The separated photocatalyst 1 is recovered in the tank by the recovery pump 11 as in the case of FIG. Further, FIG. 4 is a schematic configuration diagram of a water treatment device provided with sedimentation separation means. The photocatalyst 1 having a specific gravity of 1.1, for example, set by the specific gravity adjusting material is settled and separated at the bottom of the purified water when it passes through the settling separation tank 13, and is recovered by the recovery pump 11.

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According to the present invention, by using a fluororesin as a binder, a fluororesin powder is added to a powder of a photocatalyst and a magnetic material or a specific gravity adjusting material, mixed by stirring, and then rolled and cut. A photocatalyst can be produced in the process, and the photocatalyst particles are stably retained without being hindered in activity. Further, by adding the magnetic material and the specific gravity adjusting material, the photocatalyst can be easily and surely separated and recovered by using the magnetic separation means, the floating separation or the sedimentation separation means.

[Simple explanation of drawings]

FIG. 1 is an internal structural diagram of a photocatalyst body showing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a water treatment apparatus that separates and recovers the photocatalyst of FIG. 1 by a magnetic separation means.

FIG. 3 is a schematic configuration diagram of a water treatment apparatus that separates and recovers the photocatalyst body of FIG. 1 by a floating separation means.

FIG. 4 is a schematic configuration diagram of a water treatment apparatus that separates and recovers the photocatalyst body of FIG. 1 by gravity settling means.

[Explanation of symbols]

1 Photocatalyst 1a Fluororesin particles 1b Photocatalyst particles 1c Magnetic material or specific gravity adjusting material particles 2 Water supply pump 3 Reaction tank 5 Stirrer 6 Ultraviolet lamp 7 Drainage channel 8 Three-way solenoid valve 9 Magnetic separator 11 Recovery pump 12 Floating separation tank 13 Sedimentation Separation tank