JP2004211088A - Organic compound decomposing material and method of treating soil or water therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic compound decomposing material which is low-cost, has a high ability to decompose organic compounds, scarcely influences the environment, and is excellent in stability. <P>SOLUTION: The organic compound decomposing material contains a metal such as iron and a metal oxide such as iron oxide or titanium oxide. This material is excellent in the ability to decompose harmful organic compounds, especially highly volatile organic compounds or organic agricultural chemicals, scarcely causes secondary environmental pollution and the impairment of soil or water, and contains the metal and the metal oxide which are low-cost materials. Therefore, it is useful as a cleaning material for ground water or soil containing harmful organic compounds. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an organic compound decomposer capable of efficiently processing harmful organic compounds at low cost.

  Highly volatile organic compounds such as halogenated hydrocarbons such as trichloroethylene and tetrachloroethylene, aromatics such as benzene, xylene and toluene, and aldehydes such as acetaldehyde and formaldehyde are widely used industrially as solvents, detergents and the like. Organic pesticides such as organochlorine and organophosphorus are used in the agricultural field as insecticides, fungicides, herbicides, and the like. However, some of these organic compounds exhibit toxicity to humans, carcinogenicity, impaired growth of animals and plants, induction of malformation, and the like, and their production, use, and disposal are being strictly regulated. However, many of the above-mentioned organic compounds are hardly decomposable, and those that have been discarded or leaked without strict control until then, or those that have been used before regulation such as DDT or BHC have been found in the environment. It remains. These pollute soil and groundwater in the long term, and cause serious social problems such as highly volatile components released into the air, polluting the air. In recent years, it has been reported that some organic compounds act as so-called endocrine disruptors (or environmental hormones) that inhibit the reproductive functions of animals and plants.

  As a method of treating an organic compound in soil, a method is known in which after degassing the soil and collecting gas components, reductive decomposition is performed using hydrogen as a reducing agent and platinum or palladium as a catalyst. Non-Patent Document 1). Also known is a method in which a reducing agent or an oxidizing agent is directly injected into contaminated soil to reductively or oxidatively decompose an organic compound, that is, a so-called in-situ purification method. In this method, for example, metallic iron is used as a reducing agent. (See, for example, Patent Document 1) and composite compounds of magnetite and metallic iron (for example, see Patent Document 2). Potassium permanganate and hydrogen peroxide (for example, see Patent Document 3) are used as oxidizing agents. Have been.

Isao Jokko et al., "Environmental Catalyst Handbook", First Edition, published by NTTS Corporation, November 20, 2001, pp. 134-138. Japanese Patent No. 3079109 (pages 1-2) JP 2002-317202 A (page 1) JP-A-7-75772 (page 1)

  However, since the hydrogen reduction method uses a noble metal as a catalyst, the cost is too high. Although the in situ purification method is low-cost, the metallic iron described in Patent Document 1 causes a phenomenon called red water in which groundwater is colored red, and the metallic iron and the composite compound described in Patent Document 2 have a decomposability of organic compounds. Not enough. The oxidizing agent described in Patent Literature 3 has too strong oxidizing power and also oxidizes nitrogen compounds and minerals in the soil, thus causing a problem that the properties of the soil are changed.

  The present inventors have conducted intensive studies to solve these problems, and as a result, have found that an organic compound decomposer containing a metal and a metal oxide has a remarkably high ability to decompose an organic compound. Was completed.

  That is, the present invention is an organic compound decomposer characterized by containing a metal and a metal oxide.

  The organic compound decomposing material of the present invention is excellent in the ability to decompose harmful organic compounds, particularly highly volatile organic compounds and organic pesticides, is unlikely to cause secondary environmental pollution and deterioration of soil and water quality, and furthermore, has the effect of oxidizing metals and metals. Because it uses low-cost materials such as materials, it is useful as a purification material for groundwater and soil containing harmful organic compounds.

  The present invention is an organic compound decomposing material, characterized by containing a metal and a metal oxide. The metal and the metal oxide used in the present invention do not have a high decomposition ability of the organic compound even when they are individually brought into contact with the organic compound. It is presumed that a very excellent decomposition ability is exhibited. For this reason, even if a metal or metal oxide has a low reaction activity, it is highly decomposable by mixing and using them, and the decomposition reaction proceeds slowly, so that the properties and water quality of the soil are unlikely to change. It is thought that it may be.

  As the metal, it is sufficient that the metal itself acts as a reducing agent, and examples thereof include iron, aluminum, zinc, copper, and magnesium. These may be used alone, or two or more kinds may be mixed, It can also be used as an alloy. The form of the metal is not particularly limited, such as a fine powder, a granule, and a small piece, but the fine powder is preferable because the contact area with the organic compound is increased.

As the metal oxide, oxides such as iron, titanium, aluminum, zinc, and manganese can be used. These may be used alone or in combination of two or more, and a composite oxide thereof may be used. May be used. Here, the metal oxide includes not only a normal metal oxide but also a metal hydrated oxide and a metal hydroxide. As the metal oxide, various forms such as a fine powder, a granular form, and a small piece form can be used, and the fine powder form is preferable because the contact area is large and the reactivity is high. The use of iron oxide and / or titanium oxide as the metal oxide is preferable because of its high ability to decompose organic compounds. The iron oxide is a compound represented by the general formula FeO _x (1 ≦ x ≦ 1.5), specifically, ferrous oxide FeO (when x = 1), ferric oxide Fe ₂ O ₃ (when x = 1.5), magnetite Fe ₃ O ₄ (when x = 1.33), over-reduced magnetite FeO _x (1 <x <1.33), and beltride FeO _x (1. 33 <x <1.5). As the iron oxide, a product obtained by neutralizing waste sulfuric acid containing an iron component generated in a manufacturing process of a sulfuric acid method titanium oxide or an acid washing process of an iron material can be used. The titanium oxide is a compound represented by the general formula TiO _x (1 ≦ x ≦ 2), specifically, titanium monoxide TiO (when x = 1), dititanium trioxide Ti ₂ O ₃ (for x = 1.5), titanium dioxide TiO ₂ (for x = 2) and non-stoichiometric titanium oxide (1 <x <1.5 or 1.5 <x <2) is there.

  Furthermore, in the present invention, when a metal oxide containing oxygen at a lower ratio than that calculated from the normal valence of the metal component, that is, a so-called lower oxide is used, the reducing property of the lower metal metal oxide and This is preferable because the synthesizing effect with the reducing property of the metal increases the decomposition ability. Such materials include lower oxides such as iron, titanium and manganese. Among them, magnetite, over-reduced magnetite, beltride, and titanium oxide having a non-stoichiometric composition are preferable lower metal oxides because they have more excellent processing ability.

  The metal contained in the organic compound decomposer of the present invention and the metal element constituting the metal oxide may be different or the same. Among them, it is preferable to use metal iron and iron oxide, or metal iron and titanium oxide because of their high effects, and it is more preferable to use metal iron and iron oxide. The mixing ratio of the metal and the metal oxide (metal: metal oxide) is preferably in the range of 0.02: 1 to 9: 1 in terms of weight ratio. Is difficult to obtain. In particular, when metallic iron and iron oxide are used, if the compounding ratio is within the above range, the generation of red water is suppressed even though metallic iron is contained. A more preferred range is from 0.05: 1 to 4: 1. The metal and the metal oxide may be simply mixed, but in order to improve workability, a clay mineral such as bentonite, talc, clay or the like may be added as a binder and formed into granules or pellets. Alternatively, the powdered metal can be dispersed in water by adding a dispersant or adjusting the pH as appropriate, and the metal oxide can be mixed to form a slurry. In addition, for the purpose of enhancing the effects of the present invention, activated carbon, an adsorbent such as zeolite, or a reducing agent such as sodium sulfite may be added, or oxidizing hydrogen peroxide or the like within a range that does not impair the effects of the present invention. Agents can also be added.

  The organic compound that can be decomposed in the present invention is not particularly limited, and can be used for highly volatile organic compounds, organic pesticides, dioxins, PCBs, nonylphenol, bisphenol A, 4-nitrotoluene, and the like. Highly volatile organic compounds include halogenated hydrocarbons such as trichloroethylene, tetrachloroethylene, perchloroethylene, trichloroethane, tetrachloroethane, chlorobenzene, and dichloromethane; aromatics such as benzene, xylene, toluene, and acetone; and aldehydes such as acetaldehyde and formaldehyde. And the like. As organic pesticides, DDT, BHC, endrin, dieldrin, aldrin, heptachlor, chlordane, pentachlorobenzyl alcohol, atrazine, hexachlorobenzene, hexachlorocyclohexane, methoxychlor, chlorinated organic compounds such as pentachlorophenol, parathion, TEPP, Organophosphorus such as malathion, carbamate such as methomil, synthetic pyrethroid such as permethrin, phenoxy such as 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, or dibromochloropropane, tributyltin chloride, , 4-D, etc., among which the effect on DDT and BHC is high.

  The organic compound decomposer of the present invention can be used for water treatment and soil treatment by a known method. For example, in the water treatment, the decomposed material of the present invention is put into various wastewater such as industrial wastewater, agricultural wastewater, domestic wastewater or pumped groundwater, and after decomposing the organic compound by stirring, the decomposed material may be filtered off. Alternatively, it may be supported on an adsorbent such as activated carbon or zeolite and filled in a reaction tower for use. The treated water after treatment is recycled into the environment such as oceans, rivers, lakes and marshes, and groundwater. In the case of purification of groundwater, for example, the present invention can be applied to a so-called permeation barrier method in which a layer containing the decomposition material of the present invention is formed in soil, and when groundwater permeates this layer, organic compounds contained in the groundwater are decomposed.

  In the soil treatment, if the organic compound is highly volatile, the soil may be evacuated to collect gaseous components containing the volatile organic compound, and then contacted with the decomposition material. Alternatively, it may be applied to an in-situ purification method and introduced into soil. The in situ purification method is particularly preferable because it does not require a special facility such as a reaction tower and can purify the soil at low cost, and can be used particularly for treating low-volatile organic compounds such as organic pesticides, PCBs, and dioxins. . There is no particular limitation on the method of injecting into the soil, if it is a solid decomposed material, dig up the soil, mix the decomposed material with the soil and backfill it, or inject the decomposed material into a slurry and inject into the soil, It can be appropriately selected according to the properties of the soil, topography and the like.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Examples 1-3
As a metal, metallic iron (electrolytic metallic iron powder having an average particle diameter of about 5.0 μm: a special grade reagent, manufactured by Kanto Chemical), and as a metal oxide, iron oxide (a belt oxide (FeO _1.447 having an average particle diameter of about 0.1 μm ₎ ) Powder), and these were mixed at a weight ratio of 3: 1, 1: 1 and 0.33: 1 to obtain organic compound decomposers (samples A to C) of the present invention. These are Examples 1 to 3, respectively.

Examples 4 to 7
Metal oxide used in Example 1 as a metal and iron oxide (beltride (FeO _1.39 ) powder having an average particle size of about 0.07 μm) obtained by neutralizing and oxidizing waste sulfuric acid containing iron as a metal oxide ) Were mixed at a weight ratio of 3: 1, 1: 1, 0.33: 1, 0.1: 1 to obtain the organic compound decomposing material of the present invention (samples D to G). These are Examples 4 to 7, respectively.

Comparative Examples 1-3
The electrolytic metal iron powder used in Examples 1 to 7, the beltride powder used in Examples 1 to 3, and the beltride powder used in Examples 4 to 7 were each Comparative Examples. (Samples H to J)

Evaluation 1
Samples A to C, H, and I obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were added to a 3 ppm aqueous solution of trichloroethylene at a concentration of 25 g / liter, sealed in a vial bottle, and shaken and stirred for 24 hours. Processed. One and seven days after the treatment, the concentration of trichlorethylene contained in the aqueous solution was measured by a GC-MS headspace method. Further, the color of the aqueous solution after the treatment was visually determined.

  The evaluation results are shown in Table 1. Although metallic iron and iron oxide alone are weak in the ability to decompose organic compounds when used alone, the organic compound decomposer of the present invention obtained by mixing them has a high ability to decompose trichloroethylene, After that, it was found that the aqueous solution was not colored.

Evaluation 2
100 ml of a test solution was added to distilled water so that γ-BHC was at a concentration of 1 ppm. Samples D to G of Examples 4 to 7 and Samples H and J of Comparative Examples 1 and 3 were added to this test solution. After adding 10 g of each, the vial was sealed and shaken and stirred for 24 hours for treatment. In addition, a sample in which no sample was added to the test solution was designated as Comparative Example 4. Next, the whole amount of the sample was put into a 100 ml separating funnel, 10 ml of methylene chloride was added, and the mixture was mixed for 10 minutes. Then, the lower layer (methylene chloride layer) was collected, and this extract was subjected to gravity filtration. 10 ml of methylene chloride was further added to the remaining upper layer (aqueous layer), and after mixing for 10 minutes, the lower layer (methylene chloride layer) was collected. The extract was subjected to gravity filtration and combined with the first extract. 2 g of anhydrous sodium sulfate was added to the obtained extract and water was adsorbed for 10 minutes, and then anhydrous sodium sulfate was separated by natural filtration. The concentration of BHC contained in the extracted methylene chloride was measured by a GC-MS headspace method.

  Table 2 shows the evaluation results. It was found that the organic compound decomposing material of the present invention also has a high BHC decomposing ability.

INDUSTRIAL APPLICABILITY The present invention is useful for cleaning groundwater and soil containing harmful organic compounds.

Claims (9)

An organic compound decomposer comprising a metal and a metal oxide. The organic compound decomposer according to claim 1, wherein the metal oxide is iron oxide and / or titanium oxide. The organic compound decomposer according to claim 1, wherein the metal oxide is a lower oxide. The organic compound decomposer according to claim 1, wherein the metal is at least one selected from the group consisting of iron, aluminum, zinc, copper, and magnesium. 2. The organic compound decomposer according to claim 1, wherein the metal is iron and the metal oxide is iron oxide. 6. The organic compound decomposer according to claim 2, wherein the iron oxide is at least one selected from the group consisting of magnetite, overreduced magnetite, and beltride. 2. The organic compound decomposer according to claim 1, wherein the mixing ratio of the metal and the metal oxide is in the range of 0.02: 1 to 9: 1 by weight. A method for treating soil, comprising charging the decomposition material according to claim 1 into soil to decompose organic compounds in the soil. A method for treating water, comprising: introducing the decomposition material according to claim 1 into water to decompose an organic compound in the water, and then separating the decomposition material into a solid and a liquid.