JPH0787891B2 - Removing agent and method for removing oxidizable harmful substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention removes odorous or irritating components in gas and oxidizable harmful substances such as growth promoting components harmful to preservation of fruits and vegetables and flowers. The present invention relates to a method and a remover for the harmful substance.

[Prior Art] In recent years, with the improvement of living standards and the increasing taste of food, not only the odors and irritating ingredients that are industrially generated but also the odors and irritants that are generated at the time of cooking wastes at home and restaurants. The ingredients are becoming a problem.

On the other hand, for fruits and vegetables, etc., it is preferable that fruits and vegetables with a fresh or optimum ripening degree or seasonally or physically rare fruits and flowers always undergo ripening in the distribution process because it lowers the commercial value. Absent.

The main components of these harmful substances are malodorous components such as hydrogen sulfide, ammonia, mercaptans, amines and aldehydes, and the irritating components include aldehydes such as formaldehyde and acrolein and ozone, and fruits and vegetables. As for the preservation of species, there is ethylene, which is a plant growth hormone.

In order to remove these harmful components, the conventional method is to adsorb the harmful components to porous materials such as activated carbon, alumina, silica gel, zeolite, etc., and to remove acidic (basic) harmful components with basic (acidic) substances. It is known to use a method of oxidization, a method of chemically oxidizing harmful components with potassium permanganate, chlorine dioxide or the like.

However, these methods are not always satisfactory. That is, the method of (1) has a problem that the adsorption capacity of basic substances such as ammonia and ethylene is not sufficient and the adsorption capacity is limited, and the method of (2) limits the harmful components that can be removed depending on the compound used. The method has the drawback that the removal rate is slow.

Also, there are many cases where these harmful substance removing agents are used after being filtered, but in any case, since the adsorption capacity and the oxidation capacity are not reactivated, there is a drawback that the removal capacity inevitably shows a saturation point in a short time. .

Further, when forming a filter, it is common to fix the harmful substance remover to a non-woven fabric or a honeycomb support with a binder such as latex, organic pressure-sensitive adhesive or water glass. There is a drawback that the surface of the removing agent is covered and the removing ability cannot be fully exhibited.

[Problems to be Solved by the Invention] An object of the present invention is to provide malodorous components such as hydrogen sulfide, ammonia, mercaptan, amines and aldehydes contained in gas, irritating components such as formaldehyde, acrolein and ozone, and plants such as ethylene. It is intended to provide a method for rapidly and efficiently removing oxidizable harmful substances such as growth hormone and at the same time, a removal activity of the harmful substances and a removing agent for the harmful substances [Means for solving the problems] As a result of intensive studies to achieve this object, the inventors of the present invention, while irradiating a clay molded body containing a specific compound with ultraviolet rays, contact it with an oxidizable harmful substance contained in a gas or By passing these, these oxidizable harmful substances can be efficiently removed, and even if they are used for a long time, these compounds can be oxidized harmful substances. It found that removal activity does not fall against, and have completed the present invention based on this finding.

That is, the present invention, a clay molded body containing a semiconductor having a band gap of 0.5 ~ 5eV, a gas containing an oxidizable harmful substance is brought into contact, and ultraviolet rays are radiated. The present invention provides a method for removing oxidizable harmful substances and a removing agent used for the method.

The semiconductor having a bandgap of 0.5 to 5 eV used in the present invention is a semiconductor which causes a photocatalytic reaction, and preferably has a bandgap of 1 to 3 eV.

When a specific semiconductor is irradiated with light having an energy higher than the band gap, electronic excitation occurs from the valence band to the conduction band, and holes are generated in the valence band and electrons are generated in the conduction band.

It is known that these holes and electrons appear on the semiconductor surface by diffusion or the like and carry out a photocatalytic reaction in a gas phase or a liquid phase.

As the semiconductor used in the present invention, those having the above-mentioned effects can be used without particular limitation, and examples thereof include tin dioxide, zinc oxide, tungsten trioxide, titanium dioxide,
Metal oxides such as barium titanate and ferric oxide; for example, zinc sulfide, cadmium sulfide, lead sulfide, zinc selenide,
Metal chalcogenides such as cadmium selenide; Group IV elements such as silicon and germanium; III- such as gallium phosphide, gallium arsenide and indium phosphide
Group V compound semiconductors; for example, organic semiconductors such as polyacetylene, polypyrrole, polythiophene, polyaniline, and polyvinylcarbazole, and other semiconductors can be used.

In addition, arsenic, phosphorus, aluminum,
Those doped with impurities such as boron, sodium and halogen can also be used in the same manner.

As the semiconductor used in the present invention, metal oxides such as zinc oxide, tungsten trioxide, titanium dioxide and cerium oxide, and mixed crystals thereof are particularly suitable.

Further, by supporting a noble metal such as platinum on the surface of these semiconductors, the catalytic effect can be improved.

Furthermore, an adsorbent such as activated carbon or oxide clay may be used together.

As the clay of the clay molded body used in the present invention,
For example, clay that is used in refractories, ceramics, paper industry, rubber industry, etc. can be used, and any material that exhibits plasticity when kneaded with an appropriate amount of water and shows rigidity when dried is used. Can be used.

The clay used in the present invention includes, for example, one or more kinds of clay minerals composed of hydrous silicates such as kaolin, smectite, illite, ryokdeite, and allophane, and those having a particle size ranging from colloidal to fine sand are suitable. Can be used.

Among them, clay containing a large amount of kaolin, illite, and ryokdei stone can be preferably used because the plasticity can be obtained with a small amount of water.

Further, other deodorants, adsorbents and the like can be mixed with clay and used together with the semiconductor.

The advantage of using a clay molded product is that it does not deactivate the active sites, unlike using a binder such as latex, an organic pressure-sensitive adhesive, or water glass, or a hydrated aggregate such as gypsum or cement as a support. Therefore, the semiconductor's original ability to remove harmful substances should not be compromised, but rather should be improved considerably.

Such a remarkable preferable action occurs in the case of a clay molded body in which the binder itself or water does not cover the semiconductor surface as in the case of using other binders or the like, and when the same semiconductor amount is used, It can be presumed that the powder can be dispersed over a wider range and the light irradiation area can be increased as compared with the case where powder is used as it is.

From the viewpoint of performance, the larger the content ratio of the semiconductor in the clay molded body used in the present invention, the better. However, in order to maintain the original plasticity and moldability of clay, the content of semiconductor is preferably 80% or less, and particularly preferably 70% or less for imparting mechanical strength.

The semiconductor-added clay molding used in the present invention is provided with a support around the light source and adhered thereto, or fixed with screws, bolts or the like. Further, the clay molded body itself can be installed directly around the light source.

The clay forming body of the present invention can remove harmful substances in an air stream as a filter.

Examples of the shape of the filter formed from the clay molded body of the present invention include, but are not limited to, a porous flat membrane type, a honeycomb type, and a filter structure filling type.

The ultraviolet ray used in the present invention has a wavelength of 400 to 200 nm.
The near-ultraviolet ray is preferable from the viewpoint of reaction efficiency, but vacuum ultraviolet rays having a wavelength of 200 nm or less other than this range may be contained.

These ultraviolet rays can be generated by using an ultra-high pressure mercury lamp, a xenon lamp, and a low-pressure mercury lamp alone or in combination, but the third component such as gallium and thallium other than mercury and rare gas coexists in the discharge tube to meet the purpose. A light source modified to have the above wavelength distribution characteristics may be used. Of course, light rays other than ultraviolet rays, for example, rays including visible rays can also be used.

The ultraviolet lamp used for the irradiation of ultraviolet rays in the present invention can be installed as close as possible to the clay molded body and in the inflow direction and / or the outflow direction of the gas or liquid.
It may also be installed inside the clay compact. In order to prevent the lamp surface from being contaminated, it is particularly preferable that the lamp can be installed so as to face the outflow direction.

The method of the present invention may be carried out by introducing a gas to be treated into a specific reactor by a batch method or a continuous method, or may be installed in a circulation device or the like for continuous treatment.

The reactor used in the present invention may be an open system or a closed system, or may be a ventilation system in which a fan is used to blow air into the reactor.

The amount of the semiconductor used is the clay molded body used in the present invention or the filter formed from the clay molded body and the size and shape of the passage before and after the clay molded body, the type, composition, mixing ratio and the light source of the target oxidizable harmful substance. It depends on the type and power consumption, and is not particularly limited.

The oxidation removal reaction by the clay molded body of the present invention is sulfur oxide,
Even if various harmful substances such as nitrogen oxides, hydrocarbon compounds, halogen compounds, and media such as water and organic solvents coexist, the removal reaction will occur without being disturbed, so a method of removing harmful substances with extremely stable performance. Become.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples. The parts and% in the examples are based on weight.

Example 1, Comparative Example 1 Titanium dioxide and Kasaoka clay in the amounts shown in Table 1 were gradually added with 10 g of water and kneaded with a mixer to obtain a commercially available meat chopper having a pore size of 3 to 4 mm while being sufficiently plastic. It was used to prepare pellets of clay kneaded material.

Further, after drying the pellets at 120 ° C. for 1 hour, they were sorted by a sieve having a pore diameter of about 1 mm, and the residue remaining in the sieve was used as a sample.

5 g of the obtained sample was placed in an 80 ml Pyrex glass Erlenmeyer flask, the inside of the Erlenmeyer flask was replaced with air containing ethylene at a concentration of 85 ppm, and the container was sealed with a silicone rubber stopper. Next, the Erlenmeyer flask was irradiated with an ultra-high pressure mercury lamp (illuminance 10 mW / cm, main wavelength 365 nm) installed at a distance of 20 cm from the Erlenmeyer flask, and the time-dependent change in the concentration of ethylene in the container was traced by gas chromatography.

The results are shown in Table 1.

From the results shown in Table 1, it can be seen that the clay molded body of the present invention is superior in ethylene removal performance as compared with the case where titanium dioxide or the clay molded body is used alone.

Examples 2 to 5 Samples prepared by kneading the semiconductors shown in Table 2 with Kasaoka clay in a one-to-one manner were removed by the same method as in Example 1, except that the types of harmful components in the air were changed to those shown. An experiment was conducted. The results are shown in Table 2.

Comparative Examples 2-5 Corresponding to Examples 2-5, performance evaluation experiments were conducted by the same operation in the absence of semiconductor, and the results are shown in Table 2.

From the results shown in Table 2, it can be seen that the clay molded body of the present invention shows a remarkable removing effect against various harmful substances even if the type of semiconductor is changed.

Example 6 10 g of clay pellets prepared in the same manner as in Example 1 from equal amounts of titanium dioxide and clay were filled in a Pyrex glass glass tube having an inner diameter of 14 mm and a length of 10 cm, and a thin glass tube was penetrated at both ends of the tube. A filter was created by inserting with the rubber plug made of silicon rubber. Air containing harmful components in the initial concentration shown in Table 3 was generated by a gas generator or a cylinder, and flowed in from one thin glass tube and flowed out from the other. Then, the concentrations of harmful components in the air at the inlet and the outlet of the filter were measured by gas chromatography.

At that time, the filter portion was irradiated with ultraviolet rays by an ultra-high pressure mercury lamp (illuminance 10 mW / cm, main wavelength 364 nm) installed at a distance of 20 cm from the glass tube.

From the results shown in Table 3, it can be seen that various harmful substances can be efficiently removed by passing through the filter filled with the clay molded body of the present invention.

Examples 7 to 8 and Comparative Examples 6 to 7 Clays prepared by kneading titanium dioxide and Kasaoka clay in a one-to-one ratio as shown in Table 4 in order to compare the difference in removal capacity depending on the molding method or the supporting method. Pellets Commercially available titanium dioxide powder (manufactured by Nippon Aerosil Co., Ltd.) Titanium dioxide honeycomb molded body (manufactured by Kyocera Corporation) Titanium dioxide-supported gypsum Titanium dioxide-supported cement Commercially available porous polyurethane (manufactured by Bridgestone Co., Ltd.) Similarly, an experiment for removing ethylene and methyl mercaptan was carried out using an 80 ml Erlenmeyer flask. The results are shown in Table 4.

In addition, plaster and cement have predetermined dimensions (cross section 3
(3 cm ² × 4 cm length) was added and molded, and a predetermined amount of titanium dioxide was carried while the surface was still soft, and naturally dried to obtain a sample.

The porous urethane was used as a sample by supporting a predetermined amount of titanium dioxide on a porous polyurethane honeycomb using a urethane-based adhesive (Asahi Denka Co., Ltd.) and cutting it into 3 × 5 × 0.5 cm ³ .

From the results in Table 4, it can be seen that the clay molded product of the present invention is superior in removal performance of harmful substances as compared with the case where titanium dioxide is supported on another carrier.

Example 9 and Comparative Example 9 The titanium dioxide-supporting clay pellets used in the experiment of Example 2 were put into an 80 ml Erlenmeyer flask as in Example 1, and ozone generated by a commercially available ozone generator was added to be about 100 ppm. After that, ultraviolet irradiation was started, and the time-dependent change in ozone concentration was examined using a detector tube NO18L manufactured by Gastec. The results are shown in Table 5.

At that time, since the measuring range of the detector tube was narrow (0.1ppm to 3ppm), it was diluted 16 times for measurement.

In the comparative experiment as well, the performance evaluation against ozone was similarly performed using the indicated removing agent.

From the results shown in Table 5, it can be seen that the clay molded product of the present invention has excellent performance in removing ozone.

Example 10 5 g of the same clay molded body used in Example 2A was placed in an Erlenmeyer flask made of Pyrax glass, and the inside of the Erlenmeyer flask was set to 1000.
Continuously replace with air containing 0 ppm ethylene. After the ethylene concentration in the flask became stable at 10000 ppm, UV irradiation was started in the same manner as in Example 1, and the ethylene concentration began to decrease and became half after 2 hours.

On the other hand, when a similar experiment was carried out on the activated carbon honeycomb molded body, a concentration drop of several hundred ppm was first observed, but it reached a substantially constant value after 1 hour, and the concentration did not drop further.

Further, the same experiment was carried out for potassium permanganate, but the ethylene concentration hardly decreased.

From these results, it is understood that the clay molded body of the present invention has the harmful substance removing activity regenerated by the irradiation of ultraviolet rays.

[Advantages of the Invention] According to the present invention, compared with the prior art, it is more harmful to the storage of malodorous components such as hydrogen sulfide, ammonia, mercaptan, amines and aldehydes, irritating components such as formaldehyde and acrolein, and fruits and vegetables. It is possible to remove gas containing ethylene and other substances at the same time quickly and efficiently regardless of the kind of harmful substances, and the removal activity does not deteriorate. The method of the present invention is highly safe and has a wide range of applicable harmful substances.In addition, various harmful substances such as sulfur oxides, nitrogen oxides, hydrocarbon compounds and halogen-containing compounds, water and organic solvents, etc. Even if the medium coexists, the removal reaction takes place without being disturbed, so that the performance is extremely stable and there is an advantage that systemization is simple.

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Claims (2)

[Claims] 1. A clay molded body containing a semiconductor having a band gap of 0.5 to 5 eV is brought into contact with a gas containing an oxidizable harmful substance and irradiated with ultraviolet rays. Method for removing oxidative harmful substances. 2. An agent for removing oxidizable harmful substances, which is a molded body composed of a semiconductor powder having a band gap of 0.5 to 5 eV and clay.