JP2002205064A - Cleaning module for aqueous environment using fluidized bed of titania spherical porous bodies and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a practical energy minimum-type aqueous environment cleaning system by obtaining a high performance water-based environment purification module in which a self-supported photocatalyst not requiring a binder or a substrate causing lowering of the performance of a fine powder photocatalyst is used. SOLUTION: As the self-supported photocatalyst to be used without using the binder or the substrate causing lowering of the functions of the fine powder photocatalyst, titania spherical porous bodies having excellent wear resistance are produced and a fluidized bed is formed by passing water from the lower part in a module filled with the titania spherical porous bodies. the practical water-based purification module capable of efficiently decomposing and removing the pollution materials in water is obtained by irradiating the fluidized bed with ultraviolet rays.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention aims to develop a photocatalyst module for an energy-minimum type environmental purification system, and has studied on the form and utilization of a photocatalyst that decomposes environmental pollutants with high efficiency. Instead of using the photocatalyst immobilized on the base material, a so-called self-supporting photocatalyst is formed into a fluidized bed using a spheroidized photocatalyst. Regarding utilization, it enabled the decomposition of environmental pollutants with higher efficiency than the immobilized photocatalyst.

[Prior Art] A photocatalyst is expected as an energy minimum type environmental purification material because it can decompose and remove environmental pollutants using sunlight. Until now, various photocatalysts as environmental purification materials for air and water have been studied, but there is no substitute for titania from the viewpoint of chemical stability and safety. The application of is being actively studied. However, the excellent performance of titania is an inherent property of the substance for fine powders and thin films, and it was necessary to use it by fixing it to a base material for practical use. This is called immobilization, but it is generally difficult to immobilize it, and when it is immobilized using a binder, there is a disadvantage that the performance originally possessed is extremely reduced. Especially in aqueous systems, if the fine powder is mixed uniformly in water, it is difficult to separate the treated water from the photocatalyst fine particles. Often, a method is used in which the water is passed through the surface at a considerable speed using a material having a reduced water content. However, with this method, the probability of contact between the photocatalyst and the contaminant is low, the light irradiation on the photocatalyst surface is not uniform, and the results are far less than the data obtained in basic research.

[Problems to be Solved by the Invention] As described above, even the titania having the best performance as an environmental purification material must be immobilized and used by some method. Building a water purification system is difficult and delayed. Therefore, in order to construct a practical energy minimum type water purification system, first, it is a so-called self-supporting photocatalyst that can be used without using a binder or a base material. Modularization is required to purify substances. In view of the above-mentioned problems in the fine powder or the immobilized photocatalyst and the conditions required for the energy-minimum type water-based purification system, the present invention does not require the use of a binder or a base material, and more efficiently purifies underwater pollutants. The present invention proposes a water-based purification module using a self-supporting photocatalyst and a method for manufacturing the same.

[Means for Solving the Problems] In order to achieve the above object, the present inventors have conducted intensive studies. As a result, a photocatalyst was formed into a spherical porous body having excellent wear resistance, and a fluidized bed was formed in flowing water. We succeeded in developing an environmental purification module that can irradiate light. That is, the present invention is a water-based environmental purification module characterized in that underwater contaminants are decomposed with high efficiency while forming a fluidized bed on the titania spherical porous body. The diameter of the titania spherical porous material to be fluidized is 30
It is preferable that the porosity is 5 to 85% and the specific surface area is 5 to 100 m ² / g. If the diameter of the spherical porous body is 30 μm or less, it cannot stay in the fluidized bed in flowing water and is unevenly distributed above the module.
Further, depending on the porosity, a fluidized bed cannot be formed at a thickness of 1000 μm or more. The porosity of such a spherical porous body to be fluidized is preferably from 5 to 85%. The photocatalytic function of decomposing pollutants first requires close adsorption of dissolved oxygen and pollutants to the catalyst, and a dense spherical body is not preferable. However, as the porosity increases, the strength of the spherical porous body decreases and the powder is powdered in the fluidized bed. Therefore, the porosity of the spherical porous body is optimally 10 to 60%. From the mechanism of decomposition of the contaminants of the photocatalyst, the larger the specific surface area is, the more preferable it is.
It is preferably m ² / g. If it is larger than 100 m ² / g, sintering of titania is not sufficient, abrasion resistance is reduced, and abrasion occurs in the fluidized bed, which is not preferable.

[0005] In producing such an aqueous environmental purification module, the titania spherical porous material to be filled in the module is made of titanium alkoxide or an inorganic polymer obtained by using titanium alkoxide and β-diketone as raw materials. After impregnating the porous body, it can be synthesized by oxidative decomposition. As the titanium alkoxide, titanium tetraisopropoxide and titanium tetra-n-butoxide are preferable. These alkoxides are dissolved in ethanol, isopropyl alcohol, etc., and if necessary, β-diketone such as ethyl acetoacetate is added. Then, a mixed solution of hydrochloric acid and ethanol is added, concentrated, impregnated, and hydrolyzed to form an inorganic polymer. A solvent having a predetermined concentration can be added by adding a solvent as needed. The concentration of the impregnating solution in terms of TiO ₂ is preferably 10 to 30 mol%. If the concentration is 10 mol% or less, the TiO ₂ impregnation amount is not sufficient, and the impregnation operation needs to be repeated many times.
If it is 1% or more, the viscosity of the solution becomes high and it is difficult to make the solution penetrate into the inside of the substrate, which is not preferable. After the substrate is impregnated, it is dried and baked in the air. If necessary, the above-mentioned impregnation operation may be repeated several times. Further, after adjusting the titanium alkoxide instead of impregnating the inorganic polymeric hexane, toluene, xylene, a concentration of 10-50 mol% in dissolved terms of TiO ₂ in an organic solvent such as tetrahydrofuran, and impregnating the substrate drying In some cases, the same result as that obtained by impregnating with an inorganic polymer may be obtained by hydrolyzing with a trace amount of water in the base material or water vapor in the atmosphere, and repeating this as necessary.

[0006] The substrate impregnated with the TiO ₂ precursor is fired at 400 to 600 ° C in the air or in an oxygen atmosphere to obtain a titania spherical porous body. At 400 ° C. or lower, crystallization of anatase does not sufficiently proceed, and at 600 ° C. or higher, crystal transition from anatase to rutile occurs, which is not preferable because the photocatalytic function is significantly reduced. An organic polymer spherical porous body is used as the substrate impregnated with the inorganic polymer.
This organic polymer spherical porous body is composed of a crosslinked polymer that is insoluble in an organic solvent, and has a thickness of 0.05 to 1 due to a crosslinked network.
It is preferable that macropores of about 0.01 to 10 μm are formed between microgels of about 0 μm. For example, bead-like polystyrene synthesized by copolymerizing styrene with divinylbenzene as a cross-linking agent, or a phenol resin-based And polycondensation type gels, which are already produced in large quantities by industrially established methods.

[Operation] The water-based environmental purification module according to the present invention can decompose and remove underwater pollutants with high efficiency because the titania spherical porous material is used in a fluidized bed. Conventional removal of contaminants in water involves suspending the photocatalyst fine powder in water, irradiating the batch with light to decompose the contaminants in the water, and separating the water and photocatalyst fine powder using an ultrafiltration membrane. And it has not been put to practical use due to low throughput and high cost. On the other hand, a material that coats glass beads with titania to cause photodegradation of contaminants in water is also being studied.However, a coating process must be added, and glass having a particle size that can be fluidized is also required. The production of beads is difficult, and above all, there is a disadvantage that the photocatalytic effect is not maintained for a long time due to the abrasion of the coating layer, and an environmental purification module using a photocatalyst in a fluidized bed has not been realized. On the other hand, the titania spherical porous body of the present invention itself is 100%.
It is a self-supporting photocatalyst that is a% titania, and when water is passed from below in the module to form a fluidized bed of a certain height, water contaminants are decomposed in the fluidized bed and only purified water is removed. Since it is separated upward, it has the greatest feature that water can be continuously purified in a flowing water system. Moreover, since the photocatalyst is a porous body, the contaminants are adsorbed by the porous body and pass through the catalyst surface when being discharged again to the outside of the porous body. On the other hand, the titania spherical porous body filled in the module is always flowing by forming a fluidized bed, and should inevitably move to the light irradiation surface,
This is presumed to be the cause of the high-efficiency decomposition of water pollutants in the fluidized bed.

On the other hand, such a titania spherical porous material capable of forming a fluidized bed is prepared by impregnating an inorganic polymer, which is a TiO ₂ precursor, into an organic polymer spherical porous material having macropores. It is presumed that synthesis was possible by forming a network of the _two precursor inorganic polymers and sintering them. In a water-based environmental purification module that continuously decomposes and removes underwater contaminants by a fluidized bed, a spherical porous body with excellent wear resistance is indispensable, and the spherical porous body has sufficient performance. is there.

Next, the present invention will be described in detail with reference to examples. (Example 1) Titanium tetraisopropoxide was dissolved in hexane and adjusted to 20 mol%. This solution is commercially available divinylbenzene synthetic adsorbent, styrene gel ion exchange resin, methacrylic porous ion exchange resin,
And a methacrylic high-porous synthetic adsorbent. 100 to 11 except for divinylbenzene synthetic adsorbent
It was used after drying at 0 ° C. After impregnation and drying, 500 in air
Calcination was performed at 1 ° C. for 1 hour to obtain an anatase type titania spherical porous body. However, the styrene gel type ion exchange resin did not become spherical but became powder. The reason for this is that there is no macropore in the substrate. The diameter, porosity, and specific surface area of these titania spherical porous bodies are 80 to 130 μm in diameter with a divinylbenzene synthetic adsorbent, 8% in porosity, 6 m ² / g in specific surface area, and 120 in diameter with a methacrylic porous ion exchange resin. ~ 500 µm, porosity 45%, specific surface area 5
5 m ² / g, methacrylic high-porous synthetic adsorbent with a diameter of 110 to 350 μm, porosity of 63%, specific surface area of 87
m ² / g. 1 g of each of these spherical porous bodies
Each was filled in a quartz glass tube with a glass filter having an inner diameter of 6 mm and a length of 20 cm to form a water-based purification module, and 100 ml of a 10 ppm aqueous methylene blue solution was passed through at a flow rate of 35 ml / min from below to form a fluidized bed having a height of 15 cm. Irradiation with black light (wavelength range 310 to 400 nm) at 1.3 mW / cm ² , the color disappeared after about 100 minutes. FIG. 1 shows an example of the result of tracking this process with an ultraviolet-visible absorption spectrum. This result is at the same level as the rate of decolorization of methylene blue performed batchwise using the photocatalyst fine powder. Further, even when the water-passing test was continued for two months, the appearance of the titania spherical porous body did not change, and the abrasion resistance was excellent.

Example 2 Titanium tetra-n-butoxide was dissolved in isopropyl alcohol and adjusted to 30 mol%. This solution was impregnated into chitosan resin spheres after replacing water as a swelling solvent with isopropyl alcohol, and calcined at 500 ° C. for 1 hour in the atmosphere to obtain a titania spherical porous body. This had a diameter of 500 to 1000 μm, a porosity of 75%, and a specific surface area of 12 m ² / g. Example 1
Water-based purification module in the same manner as described above, flow rate 10 ml / mi
When methylene blue was decolorized with n, the color disappeared in about 2 hours. During the test, slight destruction of the porous body was observed.

Example 3 Ethyl acetoacetate, an equimolar β-diketone, was added to titanium tetraisopropoxide and diluted with ethanol. The mixture was stirred for 1 hour while a mixed solution of hydrochloric acid and ethanol was added dropwise. Thereafter, the mixture was concentrated under reduced pressure using a rotary evaporator to obtain an inorganic polymer which is a precursor of titania. This precursor was impregnated into a substrate similar to the substrate used in Example 1 as a 25 mol% ethanol solution in terms of TiO ₂ . Thereafter, it was dried and calcined at 550 ° C. for 1 hour in the atmosphere to obtain a titania spherical porous body. However, a spherical porous body could not be obtained with the divinylbenzene-based synthetic adsorbent and the styrene-based gel-type ion exchange resin. The reason for this is that the precursor has a larger molecular weight than that of Example 1, and the divinylbenzene-based synthetic adsorbent having a small pore size of the macropore or a styrene-based gel-type ion exchange resin having no macropore makes it difficult for the precursor to penetrate inside. .
The obtained titania spherical porous body is a methacrylic porous ion exchange resin having a diameter of 150 to 600 μm and a porosity of 4
0%, specific surface area 51 m ² / g, methacrylic high-porous synthetic adsorbent, diameter 150 to 380 μm, porosity 5
8%, and the specific surface area was 68 m ² / g. These titania spherical porous bodies were modularized in the same manner as in Example 1 and subjected to a decolorization test of methylene blue. As a result, the color disappeared in about 2 hours. Next, this module was used to carry out a decomposition removal test of 19 ppm of Na salt of pentachlorophenol at a flow rate of 35 ml.
/ Min. Almost 3 hours, the peak disappeared in the ultraviolet-visible absorption spectrum. The results are shown in FIG. FIG. 3 shows the results of following this decomposition process by reducing the total organic carbon (TOC) in the solution. Decomposition of pentachlorophenol into carbon dioxide and inorganic chlorine, which was not revealed in the ultraviolet-visible absorption spectrum, became apparent.

[Effects of the Invention] As described above, according to the present invention, titania is converted into a spherical porous body, and water is passed through a module filled with the titania from below to form a fluidized bed, thereby containing the titania in water. Pollutants can be decomposed and removed with the same performance as the fine powder photocatalyst. Moreover, this module uses a titania spherical porous material with excellent wear resistance, so it can continuously decompose underwater pollutants continuously in a flowing water system for a long period of time, and an aqueous environmental purification system that could not be used with a fine powder photocatalyst Is realized.

[Brief description of the drawings]

FIG. 1 shows the results of purifying the decolorization of methylene blue by a titania spherical porous fluidized bed with an ultraviolet-visible absorption spectrum.

FIG. 2 shows the results of tracking the degradation of pentachlorophenol Na salt by a titania spherical porous fluidized bed with an ultraviolet-visible absorption spectrum.

FIG. 3 shows the results of tracking the degradation of pentachlorophenol Na salt by the fluidized bed of titania spherical porous material by reducing the TOC.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4D037 AA11 AB05 AB11 AB12 AB13 AB14 AB16 BA18 BB04 CA12 4D050 AA12 AB15 AB17 AB18 AB19 BB01 BC06 BC09 BD02 4G069 AA02 AA08 BA04A BA04B BA22C BA48A BC50C BE06C BE10C04EBX EB EA04 EB05 EB18Y EC02X EC02Y EC22Y ED10 FA01 FB13 FB30 FB39 FC02

Claims (4)

[Claims] 1. A water-based environmental purification module characterized in that titania is made into a spherical porous body, and after filling the same, water to be purified is passed from below to form a fluidized bed. 2. The titania spherical porous body to be fluidized is excellent in abrasion resistance and has a diameter of 30 to 1000 μm and a porosity of 5 to 5.
80%, aqueous environment purification module of claim 1, specific surface area, characterized in that a 5 to 100 m ² / g. 3. An aqueous environmental purification joule characterized in that an organic polymer porous body is impregnated with a titanium alkoxide or an inorganic polymer obtained from a titanium alkoxide and β-diketone as raw materials and then oxidatively decomposed and synthesized. How to manufacture. 4. An organic polymer porous body impregnated with an inorganic polymer obtained by using titanium alkoxide or a titanium alkoxide and β-diketone as raw materials is made of a crosslinked polymer insoluble in an organic solvent, and is formed of a crosslinked network. 05
The method for producing an aqueous environmental purification module according to claim 3, wherein macropores of about 0.01 to 10 m are formed between microgels of about 10 to 10 m.