JP2006095509A - Composition having organic compound decomposition property and decomposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a water-soluble chemical agent and to provide a decomposition method capable of economically and efficiently decomposing an organic compound polluting soil and groundwater into harmless substances. <P>SOLUTION: The subject composition containing a water-soluble metal compound containing a metal having a plurality of oxidation numbers and being in +2 or +3 oxidation number state, a reducing agent, and water is used for the decomposition method. The water-soluble metal compound may be zinc chloride, ferrous chloride, manganese dichloride, ferrous sulfate, and ferrous nitrate. The reducing agent may be sodium sulfite, sodium hydrogen sulfite, sodium thiosulfate, sodium phosphite, and sodium pyrophosphite. A preferable ratio of the water-soluble metal compound to the reducing agent is 1 to 200 pts. wt. of the water-soluble metal compound to 100 pts. wt. of the reducing agent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drug having the property of cheaply and effectively decomposing volatile organic compounds, particularly volatile organic compounds contaminating soil and groundwater.

  Volatile organic compounds such as trichloroethene and tetrachloroethene are widely used as cleaning agents and solvents for dry cleaning in the machinery and semiconductor industries due to their nonflammability, flame retardancy, and degreasing properties. I came. However, in recent years, contamination of soil or groundwater by these compounds has been confirmed, and removal / decomposition of volatile organic compounds that contaminate soil and groundwater is strongly desired because of the risk of harming human health.

Conventionally, soil gas suction method, groundwater pumping method and soil excavation method have been proposed as methods for purifying soil and groundwater contaminated with volatile organic compounds. The problem that it cannot be disassembled in the field, is difficult to apply to soil contamination in the deep underground and the place where the building is located for technical reasons, and is very expensive. was there.
As a method of purifying soil etc. by decomposing volatile organic compounds separated from soil etc. by the above purification method or directly decomposing organic compounds in soil etc., combustion decomposition method, thermal decomposition method, Chemical decomposition methods, catalytic decomposition methods, microbial decomposition methods, and electrolysis methods are known.

Among them, a decomposition method using a reduction reaction such as iron powder has been proposed as a chemical decomposition method that is easy to use on site and can be reliably decomposed (Patent Document 1). However, in this method, the iron powder is oxidized by oxygen in the air during storage, so that the decomposition ability tends to decrease with time, and another problem arises that groundwater becomes red during use.
As a method improved from the method disclosed in the above-mentioned document 1, a method in which another drug is combined with iron powder (Patent Document 2), a method using another reducing drug (Patent Document 3), and the like have been proposed. However, since the decomposing agents used in these methods are all made of solid matter, the soil and the decomposing agent must be mixed and stirred with each other in order to construct them directly on the soil. In the mixing of solids, there is a problem that it takes a long time to decompose the organic matter in that the contact between the decomposer and the organic matter is not homogeneous.
JP 2000-135483 A JP 2002-282834 A JP 2004-074141 A JP-A-5-231086 Japanese Patent Laid-Open No. 9-1225859 JP 2003-337534 A

  The problem to be solved by the present invention is by decomposing volatile organic compounds and purifying soil and groundwater contaminated with them, by using a combination of chemicals having good solubility in water, To construct and purify at low cost, reliably and efficiently.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, the present invention has a decomposability of an organic compound composed of a water-soluble metal compound, a reducing agent, and water, which is composed of a metal having a plurality of oxidation numbers and having an oxidation number of +2 or +3. The composition includes the following inventions (hereinafter also referred to as a decomposable composition).
(1) The decomposable composition, wherein the metal is a transition metal and the oxidation number of the water-soluble metal compound is +2.
(2) The degradable composition, wherein the water-soluble metal compound is a metal salt compound.
(3) The decomposable composition, wherein the reducing agent is an alkali metal sulfite or an alkali metal hydrogen sulfite.
(4) The decomposable composition comprising 1 to 200 parts by mass of the water-soluble metal compound per 100 parts by mass of the reducing agent.
(5) A method for decomposing an organic compound comprising decomposing a chlorinated organic compound using the decomposable composition.
(6) A method for decomposing the organic compound, comprising: confirming that the soil is contaminated with an organic compound; and applying a composition having organic compound decomposability.

  According to the present invention, the chemical having the property of decomposing organic matter can be applied to the contaminated soil in the form of an aqueous solution, and the expensive construction cost that has been a problem in the conventional method for chemically purifying the contaminated soil / groundwater. It is possible to decompose the contaminated organic compound reliably and efficiently while making the price low.

The organic compound to be decomposed in the present invention is not particularly limited, but 1,1-dichloroethene, 1,2-dichloroethene, trichloroethene, tetrachloroethene, dichloromethane, carbon tetrachloride, 1, Halogenated hydrocarbons such as 2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane and chlorobenzene, and aromatic carbonization such as benzene, toluene and xylene Hydrogen etc. are mentioned.
The above-mentioned halogenated hydrocarbons or aromatic hydrocarbons are typical organic compounds that contaminate soil, groundwater, etc. as a result of being used in large quantities on earth as a cooling medium for air conditioners or paint solvents in the past. It is said that there is.

As described above, the decomposable composition of the present invention includes a water-soluble metal compound that is a metal that can have a plurality of oxidation numbers and is composed of a metal that has an oxidation number of +2 or +3 as a component. . In the present invention, “water-soluble” means that the solubility is 1 g or more with respect to 100 g of water.
Water-soluble metal compounds that may be used in the present invention (hereinafter sometimes referred to simply as metal compounds) include magnesium chloride, zinc chloride, manganese dichloride, ferrous chloride, cobalt chloride, nickel chloride, titanium trichloride, and trichloride. Metal chlorides such as vanadium and chromium dichloride, magnesium sulfate, zinc sulfate, manganese sulfate, ferrous sulfate, ferrous nitrate, ferrous ammonium sulfate, cobalt sulfate, nickel sulfate, dititanium trisulfate and di Examples thereof include metal sulfates such as zirconium sulfate. A plurality of compounds can be used in combination as the metal compound.
Preferred metal compounds are transition metal salts having an oxidation number of +2 such as ferrous chloride and manganese dichloride, more preferably ferrous chloride and ferrous sulfate.

The reducing agent used in combination with the water-soluble metal compound is preferably a compound having a reduction reactivity that satisfies the following requirements, specifically sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium phosphite and Sodium pyrophosphite or a compound in which these sodium is substituted with potassium is preferred.
In the present invention, the reduction reactivity is evaluated by the following method using an oxidation-reduction reaction with iodine, and the reducing agent in the present invention is preferably a compound that is colorless in the following (d). In addition, in the following evaluation method, the conditions of the starch sensitivity test in JIS K 8659-1996 concerning starch are employed as they are.
(A) Aqueous starch solution; an aqueous solution obtained by further diluting 1 ml of starch in 100 ml of water into 20 ml of water (b) starch / iodine solution; iodine solution having a concentration of 2.5 mmol / L with respect to 20 ml of the above starch solution (2) Addition of 2 ml (c) Addition of reducing agent; To 20 ml of the starch / iodine solution, 0.2 ml of a reducing agent solution having a concentration of 5.0 mmol / L is added and left at room temperature for 10 minutes.
(D) Check whether the solution has become colorless after standing for 10 minutes in (c) above.

A preferred ratio of the reducing agent to the metal compound is 1 to 200 parts by mass of the metal compound per 100 parts by mass of the reducing agent in that the organic compound is efficiently decomposed. Especially preferably, it is 10-100 mass parts of metal compounds per 100 mass parts of reducing agents.
The composition of the present invention comprises the above reducing agent, metal compound and water as essential components, and the preferred amount of water used is based on the total amount of the reducing agent, metal compound and water. The total amount of the compounds (hereinafter collectively referred to as active ingredients) is 0.01 to 10% by mass. A more preferable amount of water used is such that the proportion of the active ingredient is 0.1 to 5% by mass.

The method of mixing each component is not particularly limited, and each drug may be used after being dissolved in water and dissolved, or after each drug is mixed in a powder state and dissolved in water. It is also possible to prepare an aqueous solution of each drug and then mix it before construction. Preferably, the reducing agent and the metal compound are mixed immediately before the construction or used as an aqueous solution because they can be stably applied.
In the present invention, the reducing agent and the metal compound do not exhibit sufficient decomposition ability even if they are brought into contact with an organic compound alone, but they exhibit excellent decomposition ability when used in combination. To do. The decomposition mechanism is not clear, but in the examples described later, only carbon dioxide gas and chlorine ions were confirmed as the decomposition products of trichloroethene, so that they are different from the conventional reductive decomposition reaction of trichloroethene. It is guessed. In the conventional reductive decomposition of trichloroethene, cis-1,2-dichloroethene, chloroethene and ethylene were detected as decomposition products, and therefore it is explained that sequential dechlorination reaction occurs. .

In the present invention, there is no limitation on the method of using the degradable composition of the present invention, but a method of spreading and infiltrating the soil is preferably employed. Specifically, a step of confirming that the soil is contaminated with an organic compound and a step of applying the composition having the organic matter decomposability are employed.
As a specific example of the process for confirming soil contaminated with organic compounds, sampling and measurement related to soil gas surveys stipulated in Ordinance No. 16 of the Ordinance of the Ministry of the Environment are conducted based on the Enforcement Rules of the Soil Contamination Countermeasures Law. In addition, the methods described in Patent Documents 4 to 6 are also possible.
The points to be surveyed are also determined based on the laws and regulations, taking into consideration the center point of the 10m grid and the center point of the 30m grid, the size of the entire land concerned, and the possibility of contamination spreading.
As for the part where it is recognized that there is a high possibility that contaminated soil is concentrated, a 1m grid as described in Patent Document 6, a history of handling volatile organic compounds, immovable buildings and large-sized buildings Considering the existence of equipment, etc., it is possible to determine a specific point according to the actual situation.

  As a specific example of the process of applying a composition having organic substance decomposability, a spot where contamination is detected by the above-mentioned investigation is selected, and a spot detected at a high concentration is mainly applied. If necessary, work around contaminated points and low-concentration points. If the flow of groundwater or the direction in which the contamination has spread is known, it is effective to install it upstream.

  The construction of the decomposable composition of the present invention may be applied by spreading and infiltrating the soil, or a method of injecting the decomposable composition through the injection tube by inserting an injection tube into the soil or groundwater can be employed. More specifically, there is a method in which the decomposable composition is directly injected into the holes or wells used in the survey, especially in the hole where the high concentration of contamination is observed, or is sprayed and permeated around the hole including those holes. Adopted. A degradable composition may be added to the groundwater pumped around these survey holes, or the water treated in this way may be returned to the groundwater and circulated. It may be recovered together with water directly by soil gas suction, pumped water aeration, air sparging, or the like, or an organic compound once adsorbed on activated carbon or the like may be treated with a decomposable composition and decomposed. It is also possible to decompose organic compounds by mixing the degradable composition into the excavated contaminated soil.

  The preferable use amount of the decomposable composition is 0.5 to 10,000 parts by mass with respect to 1 part by mass of the organic compound as the total amount of the metal compound and the reducing agent, and more preferably 2 to 2 on the same basis. 4,000 parts by mass.

The decomposable composition of the present invention is the same as described above for the soil when the organic matter is not sufficiently decomposed by the above treatment, or when the organic matter is once decontaminated after being decomposed by the treatment. It is possible to re-investigate and reconstruct by this method.
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
○ Example 1

Into a 40 mL vial, take 0.1 g of sodium bisulfite and 0.1 g of ferrous chloride, add 20 g of distilled water, mix, dissolve, and use a silicone rubber septum and aluminum cap coated with fluorine resin. Sealed. Inside, 5 μL of trichloroethene was injected using a microsyringe, and the concentration of trichloroethene in the gas phase after shaking for 3 days in a thermostatic chamber at 25 ° C. was analyzed by headspace gas chromatography. The ratio with respect to the analysis result immediately after mixing (hereinafter referred to as “blank”) when no chemical was added was defined as the decomposition ratio as shown in the following formula and was calculated to be 0.5.
In gas chromatography, cis-1,2-dichloroethene, chloroethene and ethylene were not detected. Further, it was confirmed by the separate analysis method that carbon dioxide gas and chlorine ions were generated in the cracked gas.
Decomposition ratio = (area of trichloroethene after 3 days) ÷ (area of blank)
○ Examples 2 to 14

Table 1 shows the results of determining the decomposition ratio after shaking for a predetermined time using the reducing agent and metal compound described in Table 1.
○ Comparative Examples 1-9

  Trichloroethene was decomposed under the conditions described in Table 1, and the result was expressed as a decomposition ratio.

○実施例１５

Example 15

A glass column with a diameter of 26 mm and a height of 300 mm is packed with 150 g of masa soil (* 1), to which 7.5 mg of trichloroethene dissolved in 20 g of water is added, and the pollution corresponding to a soil elution amount of 5.0 mg / L Adjusted the simulated contaminated soil layer assuming the point detected by the survey. Thereto, 80 g of a 5 wt% aqueous solution prepared by dissolving sodium bisulfite and ferrous chloride in distilled water at a weight ratio of 5: 1 was added dropwise at a rate of 0.48 g / min to infiltrate the chemical solution. The soil elution amount after dropping the drug droplet was measured to be 0.01 mg / L, and the total amount of trichloroethene detected in the system was 1.9 mg by adding trichloroethene in the effluent. The ratio to the total amount of trichloroethene detected in the system (hereinafter referred to as blank) when only the same amount of distilled water without addition of chemicals was added dropwise was defined as the decomposition ratio and calculated as 0.4 It became.
In gas chromatography, cis-1,2-dichloroethene, chloroethene and ethylene were not detected. Moreover, it was confirmed by the separate analysis method that the carbon dioxide gas in the cracked gas and the chlorine ions in the liquid were increased.
Decomposition ratio = (total amount of trichloroethene after chemical treatment) ÷ (total amount of blank)
* 1. Masa soil: Weathered debris such as granite collected from the Chubu region.
Example 16

The same test as in Example 15 was performed using the reducing agent and metal compound described in Table 2. The results are shown in Table 2.
Example 17

A similar test was conducted by changing 7.5 mg of trichloroethene of Example 15 to 3.2 mg of tetrachloroethene. The results are shown in Table 2.
Examples 18 to 19

The test was performed under the conditions shown in Table 2 except that the Masa soil of Example 15 was changed to red yellow soil (* 2). The results are shown in Table 2.
* 2. Red-yellow soil: Collected from hills in western Japan.
Example 20

The test was performed in the same manner as in Example 19 except that the red-yellow soil in Example 19 was changed to black I * 3 (* 3) and the chemicals were changed to those shown in Table 2. The results are shown in Table 2.
* 3. Kuroboku soil: collected from the hilly area of the Chubu region.
○ Comparative Example 10

For the simulated contaminated soil layer of Example 15, when the amount of soil elution after dropping only the same amount of distilled water without adding a drug was measured, it was 0.03 mg / L, and trichloroethene in the effluent was also added. The total amount of trichloroethene detected in the system was 4.9 mg. In addition, this result was used as the blank of Example 15.
○ Comparative Examples 11-15

  The simulated contaminated soil layer corresponding to each of the examples described in Table 2 was prepared, and only the distilled water with no chemical added was dropped in the same amount as in each of the examples, and the amount of soil elution after the test and detected in the system. The total amount of the organic compound was measured, and the results of comparing each example and a comparative example were summarized in Table 2 as blanks for each example.

According to the present invention, volatile organic compounds can be decomposed reliably and inexpensively, and soil and groundwater contaminated by them can be constructed and purified economically and efficiently.

Claims (7)

An organic compound decomposable composition comprising a water-soluble metal compound composed of a metal having a plurality of oxidation numbers and having an oxidation number of +2 or +3, a reducing agent, and water.
2. The organic compound-decomposable composition according to claim 1, wherein the metal is a transition metal and the oxidation number of the water-soluble metal compound is +2.
3. The organic compound-decomposable composition according to claim 1, wherein the water-soluble metal compound is a metal salt compound.
4. The organic compound-decomposable composition according to claim 1, wherein the reducing agent is an alkali metal sulfite or an alkali metal hydrogen sulfite.
5. The organic compound-decomposable composition according to claim 1, wherein the water-soluble metal compound is contained in an amount of 1 to 200 parts by weight per 100 parts by weight of the reducing agent.
A method for decomposing an organic compound, comprising decomposing an organic compound using the composition having organic decomposability according to any one of claims 1 to 5.
The step of confirming that the soil is contaminated with an organic compound, and the step of constructing a composition having an organic matter decomposability according to any one of claims 1 to 5, comprising: Method for decomposing organic compounds.