JP2008272585A - Method of wet-detoxifying contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of inexpensively and easily detoxifying contaminants such as heavy metals and organic chlorine compounds in the soil without adversely affecting the environment. <P>SOLUTION: The method of wet-detoxifying the contaminated soil containing the heavy metals and the organic chlorine compounds comprises: an elution step for mixing at least an aqueous solution containing hydrogen peroxide and an acid with the contaminated soil to elute ions of the heavy metals in the mixed solution; a first degradation step by adding an alkaline compound into the aqueous solution containing the organic chlorine compounds; and a second degradation step for mixing the organic chlorine compounds and a photosensitizer and irradiating the organic chlorine compounds with ultraviolet light rays to decompose the organic chlorine compounds. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wet detoxification method for contaminated soil in which heavy metals are eluted from soil contaminated with heavy metals and organochlorine compounds.

  In recent years, soil in various manufacturing plant sites and adjacent areas has been contaminated with Type 1 specified hazardous substances (including organochlorine compounds) and Type 2 specified hazardous substances (including inorganic substances such as heavy metals). It is pointed out that there is a problem. Since there are concerns about adverse effects on human bodies due to pollutants such as heavy metals and organic chlorine compounds, an effective treatment method for detoxifying the contaminated soil is desired.

  Conventionally, incineration has been proposed as a method for detoxifying soil contaminated with heavy metals and organochlorine compounds. However, in the case of incineration treatment, not only volatile heavy metal gases such as mercury and arsenic are generated, but also dioxins generated by organochlorine compounds in the treatment object during the incineration process are included in the exhaust gas. There is a problem that it spreads widely and contaminates the soil around the incineration plant.

  In view of such problems, as a method for detoxifying soil contaminated with heavy metals and organochlorine compounds, treatment for washing and removing heavy metal contaminants in soil with an acid has been studied. Specifically, a technique for removing heavy metals by adding an aqueous acid solution having a weight 5 to 10 times that of contaminated soil to the contaminated soil, stirring and mixing, and then removing heavy metals has already been disclosed (for example, Patent Document 1). reference).

  Moreover, the following detoxification processing method of contaminated soil is also known. First, iron powder and at least one of an aluminum salt and an iron salt are added to soil contaminated with heavy metals and organochlorine compounds. Next, the pH is adjusted to be weakly acidic or alkaline, and at least one hydroxide of the produced aluminum hydroxide or iron oxide is mixed with the contaminant. Thereafter, the insolubilized soil obtained by adding the neutral cement agent is used as backfill soil (for example, see Patent Document 2).

Furthermore, there is also a technology for detoxifying contaminated soil by adopting the melting and detoxifying detoxification method, burying contaminated soil contaminated with heavy metals and organochlorine compounds in the buried pit, inserting electrodes, and energizing. Are known.
JP 05-293396 A (Claims) JP 2003-290757 A (Claims)

  However, the conventional method for detoxifying soil contaminated with heavy metals and organochlorine compounds has the following problems. Heavy metals in contaminated soil exist in various forms. If heavy metals exist in a form that is sparingly soluble in water, for example, heavy metal contaminants can be separated from soil contaminated with mercury-based pesticides such as phenyl mercury iodide or trivalent arsenic-based pesticides by the power of acid aqueous solution. Is extremely difficult. For this reason, in the case of the detoxification processing method of the contaminated soil disclosed in Patent Document 1, there is a problem that it is not possible to achieve a heavy metal removal rate that makes the contaminated soil comply with environmental standards.

  Moreover, in the case of the detoxification method of the contaminated soil disclosed in Patent Document 2, the heavy metals are not essentially purified, and the entire amount remains in the soil as it is. For this reason, when a long time elapses, the fixing effect is not sustained, and heavy metals in the soil may elute due to oxidation atmosphere or infiltration of groundwater, and may cause secondary environmental pollution.

  In addition, when adopting the melting and fixing detoxification method, the center temperature of the contaminated material in the buried pit becomes high, so a large amount of power is required, and both the equipment introduction cost and the processing cost are expensive. There is.

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to reduce heavy metals and organic matter in soil easily at low cost and without adversely affecting the environment. The object is to provide a method for detoxifying pollutants such as chlorine compounds.

  In order to achieve the above object, the present invention is a method for detoxifying contaminated soil containing heavy metals and organochlorine compounds, wherein at least an aqueous solution containing hydrogen peroxide and an acid are mixed in the contaminated soil, An elution step of eluting heavy metal ions into the mixture, a first decomposition step of decomposing by adding an alkaline compound to an aqueous solution containing an organic chlorine compound, an organic chlorine compound and a photosensitizer are mixed, This is a wet detoxification method for contaminated soil, which has a second decomposition step in which an organic chlorine compound is decomposed by ultraviolet irradiation.

For this reason, all the heavy metals and organochlorine compounds contained in the contaminated soil can be treated. Hydrogen peroxide generates HO ₂ ⁻ in an aqueous solution due to acid dissociation equilibrium. Therefore, HO ₂ ^- by the action of, it is possible to easily form the eluted heavy metals present in the form of sparingly soluble in an acidic aqueous solution. Taking mercury as an example, mercury is oxidized from a low valence of +1 or 0 to +2, and the solubility in water increases. Further, +6 valent chromium ions, which are one of heavy metals existing in a highly toxic form, can be reduced to +3 valent chromium ions by hydrogen peroxide and dissolved in water in a less toxic form. Furthermore, heavy metals can be more efficiently eluted from soil by adding an acid. Further, by mixing with a photosensitizer, an organic chlorine compound having an absorption band with a short wavelength of 200 nm or less can be efficiently decomposed with a relatively long wavelength ultraviolet ray.

  In another aspect of the present invention, a contaminated soil having a first step of mixing an aqueous solution containing at least hydrogen peroxide and a second step of mixing an acid in a mixture of the aqueous solution and the contaminated soil. It is a wet detoxification method. For this reason, heavy metals can be more efficiently eluted from soil.

  Furthermore, another present invention is a wet detoxification method for contaminated soil in which, in the first step, an alkaline compound is added and the pH of the aqueous solution is higher than 7.

Since the acid dissociation equilibrium of hydrogen peroxide is proportional to the OH ⁻ concentration of the alkaline aqueous solution, the dissociation of hydrogen peroxide increases as the pH of the mixed aqueous solution increases. Moreover, the reactive HO ₂ ⁻ produced by the dissociation of hydrogen peroxide becomes more stable as the alkalinity becomes stronger. For this reason, the processing capability by hydrogen peroxide can be further increased by adding an alkaline compound. Further, H ⁺ generated by treating heavy metals in the mixed aqueous solution to which the alkaline compound is added is neutralized. For this reason, pH can be maintained alkaline and the decomposition function of hydrogen peroxide is not lost. Therefore, the detoxification treatment of heavy metals with hydrogen peroxide can be performed stably.

  Another aspect of the present invention is a wet detoxification method for contaminated soil in which the alkaline compound is sodium hydroxide or potassium hydroxide. For this reason, the heavy metals by hydrogen peroxide can be more efficiently eluted from soil.

  Further, another aspect of the present invention is a wet detoxification method for contaminated soil in which heavy metals are one or more heavy metals selected from the second type of specific harmful substances. For this reason, heavy metals can be more effectively detoxified.

  Another invention of the present invention is a wet detoxification method for contaminated soil in which contaminated soil containing an organic chlorine compound is further brought into contact with a surfactant to elute the organic chlorine compound. By using the surfactant, the interfacial tension between the organic chlorine compound and water can be reduced, and the mobility of the organic chlorine compound can be improved. For this reason, the organochlorine compound can be efficiently eluted into water. As a result, the organic chlorine compound can be more effectively detoxified.

  In another embodiment of the present invention, a wet detoxification method for contaminated soil in which the photosensitizer is acetophenone or acetone. For this reason, an organic chlorine compound can be detoxified more effectively by ultraviolet irradiation.

  In the wet detoxification treatment method for contaminated soil according to the present invention, the contaminated soil to be treated is soil containing at least one heavy metal selected from Periodic Tables 6 to 15. Specific examples of the heavy metal include metals such as mercury, arsenic, lead, hexavalent chromium, cadmium, zinc, copper, aluminum, iron, manganese, molybdenum, and nickel. Suitable for treating contaminated soil containing mercury, arsenic. However, the heavy metal to be decomposed is merely an example, and soil contaminated with other types of heavy metals may be treated. Examples of contaminated soil that can be rendered harmless by the present invention include red soil, black soil, glai soil, loam soil, and the like.

  As the alkaline compound used in the wet detoxification method for contaminated soil according to the present invention, solid sodium hydroxide, solid potassium hydroxide or a mixture thereof, or an aqueous solution of sodium hydroxide or potassium hydroxide is preferably used. In particular, it is more preferable to use solid sodium hydroxide. However, the above-mentioned alkaline compound is only an example, and other alkaline compounds may be adopted.

  Examples of the acid selectively used in the wet detoxification method for contaminated soil according to the present invention include inorganic acids such as nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid, and boric acid, formic acid, acetic acid, oxalic acid, and citric acid. Examples thereof include organic acids such as acid, maleic acid, fumaric acid, pyruvic acid, succinic acid, tartaric acid, and phthalic acid. Of these acids, it is particularly preferable to use nitric acid. However, the above-mentioned acids can be used alone or in combination of two or more. It is preferable to change the type of acid according to the type of heavy metal.

  According to the present invention, it is possible to provide a method for detoxifying contaminants such as heavy metals and organochlorine compounds in soil easily at low cost and without adversely affecting the environment.

  Hereinafter, preferred embodiments of a wet detoxification method for contaminated soil according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments described below.

  FIG. 1 is a flowchart showing a procedure of a wet detoxification method for contaminated soil according to the present invention.

  Hereinafter, the elution process procedure for performing the wet detoxification treatment of the contaminated soil will be described with reference to FIG.

First, soil contaminated with heavy metals and organochlorine compounds is put into a processing container (step S101). Subsequently, an appropriate amount of an alkaline compound and water are put into a processing container, and the pH of the mixed aqueous solution is adjusted to a predetermined value greater than 7 (step S102). Next, hydrogen peroxide is added and stirred (step S103: first step). In the treatment of soil contaminated with heavy metals, the alkaline compound has a role of maintaining the pH of the mixed aqueous solution on the alkaline side and easily dissociating hydrogen peroxide. Thus, by adjusting the pH of the mixed aqueous solution, it is possible to stabilize the dissociation rate of hydrogen peroxide and the reactive HO ₂ ⁻ generated from the decomposition of hydrogen peroxide. Here, sodium hydroxide can be suitably used as the alkaline compound. Further, it is preferable to efficiently treat the contaminated soil by controlling the amount of hydrogen peroxide added according to the properties of the contaminated soil to be treated and the content of heavy metal contained in the soil. The mixing method may be any type of mixing method such as ultrasonic dispersion and stirring using a stirring blade, in addition to stirring using a magnetic stirrer.

  Next, an acid is added to the mixed aqueous solution to adjust the pH of the mixed solution to be acidic (step S104: second step). Next, after stirring the mixed aqueous solution, the whole amount is filtered (step S105). In this embodiment, by adding an acid, heavy metal ions that are oxidized or reduced by hydrogen peroxide can be more efficiently eluted from the soil. As the acid, nitric acid can be preferably used. In addition, the separation method of soil and the treatment liquid may be other separation methods such as centrifugation other than filtration. Moreover, it is preferable to wash the filtered soil with water.

  Subsequently, heavy metals contained in the treatment liquid are collected (step S106). In this embodiment, the treatment liquid is brought into contact with an absorbent to adsorb and remove heavy metals on the absorbent. Any known adsorbent capable of adsorbing heavy metals can be used as the adsorbent for heavy metals used in the present embodiment. For example, ion exchangers such as thiol-based exchange resins, cation exchange resins, strong acid cation exchange resins, weak acid cation exchange resins, and chelate resins can be suitably used. In the present embodiment, the treatment liquid from which heavy metals have been removed may be circulated through the heavy metal-contaminated soil treatment system.

  On the other hand, after removing heavy metals, the soil containing the organic chlorine compound is mixed with a surfactant having a predetermined concentration to elute the organic chlorine compound from the soil into the water. In the present embodiment, a nonionic surfactant is particularly preferable. As the nonionic surfactant, a low molecular weight system such as alkyl glycoside, for example, n-octyl-β-D-glucoside, or a high molecular weight system such as polyethylene glycol or polyvinyl alcohol can be preferably used. However, the above-mentioned nonionic surfactant is only an example, and other nonionic surfactants may be adopted. By using the surfactant, the interfacial tension between the organic chlorine compound and water can be reduced, and the mobility of the organic chlorine compound can be improved. In addition, since micelles are formed in an aqueous solution, the solubility of water in an organic chlorine compound that is hardly soluble in water is increased. As a result, the organic chlorine compound can be efficiently eluted into water. Moreover, it is preferable to adjust the kind and addition amount of surfactant according to the property of the contaminated soil to be treated and the content of the organochlorine compound contained in the soil to efficiently treat the contaminated soil. Next, the eluted organic chlorine compound is mixed with an alkaline aqueous solution containing a photosensitizer, and then irradiated with ultraviolet rays. By adding a photosensitizer, an organic chlorine compound having an absorption band with a short wavelength of 200 nm or less can be efficiently decomposed with a relatively long wavelength ultraviolet ray. As the photosensitizer, acetone or acetophenone can be preferably used. However, in addition to acetone or acetophenone, those having a ketone structure or an aldehyde structure may be used. In addition, it is preferable to adjust the addition amount of a photosensitizer according to the kind of organic chlorine compound, the wavelength of the ultraviolet-ray to irradiate, or the kind of photosensitizer. Moreover, you may decompose | disassemble directly in alkaline aqueous solution according to the kind of organic chlorine compound. The order of step S102 and step S103 may be changed. Further, step S102 may not be performed.

  The preferred embodiment of the wet detoxification treatment for contaminated soil according to the present invention has been described above. As a result, it is possible to efficiently detoxify contaminated soil containing heavy metals and organochlorine compounds using a simple apparatus in a short time, and the processing cost can be reduced.

  Next, examples of the wet detoxification method for contaminated soil according to the present invention will be described. However, the present invention is not limited to the following examples. Note that, in each of the following embodiments, overlapping description is omitted for each common implementation method. In each of the examples described below, the mercury, arsenic and hexavalent chromium remaining states in the heavy metal-contaminated soil treated with hydrogen peroxide are respectively described in terms of mercury detector tube (GASTEC No. 203) and arsenic detector tube ( GASTEC No. 202) and inductively coupled plasma mass spectrometer (manufactured by Yokogawa Analytical Systems). Further, the remaining state of the decomposed organochlorine compound was grasped from a GC / MS spectrum measured using a GC / MS QP5000 manufactured by Shimadzu Corporation.

(Example 1)
A. Treatment procedure First, 100 g of a sample (soil containing mercury-based pesticide) and 250 g of water were placed in a beaker and mixed with stirring. Next, sodium hydroxide was added to the above-mentioned mixed aqueous solution so as to have a pH of about 10 to 11, and 20 g of 10% hydrogen peroxide was further added, followed by stirring with a magnetic stirrer for 1 hour. Subsequently, nitric acid was added so that the pH of the mixed solution was about 1, and after stirring for 1 hour, suction filtration was performed to perform solid-liquid separation. Thereafter, the separated solid was washed twice with 100 ml of water.

  Each of the two washing waters was taken out in small amounts and used as a sample for measuring the amount of mercury remaining in the mercury-contaminated soil treated with hydrogen peroxide. On the other hand, the separated treatment liquid was passed through a column packed with a thiol-based exchange resin. A small amount of liquid after passing through the column was taken out and used as a sample for measuring mercury concentration.

B. Analysis result As a result of measuring the mercury concentration of the first washing water, the mercury concentration was 0.01 ppm. On the other hand, the mercury concentration in the second wash water was 0.005 ppm, which was below the environmental standard. On the other hand, no mercury was detected in the liquid after passing through the column. From this result, it was judged that the soil containing mercury-based pesticides can be efficiently detoxified by the wet detoxification method for contaminated soil of the present invention.

(Example 2)
A. Treatment Procedure In this example, soil containing arsenic pesticide and inorganic heavy metal exchange resin were used instead of soil containing mercury pesticide and thiol exchange resin, respectively. The processing procedure was the same as that in Example 1. A small amount of each of the solid washing water after the treatment and the liquid after passing through the column was taken out and used as a sample for measuring the arsenic concentration.

B. Analysis Result As a result of measuring the arsenic concentration of the first wash water, the arsenic concentration was 0.38 ppm. In contrast, the mercury concentration in the second wash water was 0.12 ppm, which was below the environmental standard. On the other hand, 0.05 ppm of arsenic was detected in the liquid after passing through the column. From this result, it was determined that arsenic contained in the soil can be efficiently removed by the wet detoxification method for contaminated soil of the present invention.

Example 3
A. Treatment procedure In this example, soil containing hexavalent chromium and strongly acidic cation exchange resin were used in place of soil containing mercury-based pesticide and thiol exchange resin, respectively. The processing procedure was the same as that in Example 1. A small amount of each of the washed solid water after treatment and the liquid after passing through the column was taken out and used as a sample for measuring the concentration of hexavalent chromium.

B. Analysis result As a result of measuring the hexavalent chromium concentration of the first washing water, the hexavalent chromium concentration was 2 ppm. On the other hand, the hexavalent chromium concentration of the liquid after passing through the column became a concentration below the environmental standard. Hexavalent chromium salts are not sparingly soluble, but when they are eluted in water, they become anions and cannot be recovered with a strongly acidic cation exchange resin. Considering the toxicity of hexavalent chromium, it is preferable to reduce hexavalent chromium to +3 valence and recover it as a +3 valent cation. In this example, hydrogen peroxide worked as a reducing agent, and hexavalent chromium could be reduced to + trivalent chromium. From this result, it was judged that + 6valent chromium contained in the soil can be efficiently removed by the wet detoxification method for contaminated soil of the present invention.

  Next, the treatment (first decomposition step) for removing the organic chlorine compound contained in the soil after the treatment in Examples 1 to 3 will be described.

Example 4
A. Treatment procedure 0.7 mg of BHC (hexachlorocyclohexane) pesticide (γ isomer) contained in soil was dissolved in 10 mL of acetone, and diluted with 250 mL of water to obtain a 2.8 mg / L BHC aqueous solution. . To this aqueous solution, 1 mL of 50 μg / mL phenanthrene-n-hexane solution was added as an internal standard reagent. Further, 0.2 g of sodium hydroxide was added to the aqueous solution to adjust the alkali concentration to 0.1 M, and the BHC pesticide was decomposed. The decomposition of the BHC pesticide is stopped by adding hydrochloric acid to the alkaline aqueous solution and neutralizing it. The decomposition times for the BHC pesticides were 0, 5, 10, 20 and 30 minutes, respectively. At the elapse of each time, a 50 ml sample was taken out, and the organic component was extracted with hexane. After dehydration with anhydrous sodium sulfate and filtration, the extract was evaporated in vacuo by an evaporator at 50 ° C., and the extract was dissolved in 2 ml of hexane to prepare a sample for measuring GC / MS spectrum.

B. Analysis Results FIGS. 2 to 6 are GC / MS measurement results showing the effect of treatment time with an aqueous sodium hydroxide solution on the decomposition treatment of BHC pesticides. In FIG. 2, the upper and lower charts are a GC spectrum chart and an enlarged chart of the upper GC spectrum, respectively. In each of FIGS. 3 to 6, the upper chart, the middle chart, and the lower chart are a GC spectrum chart, an enlarged chart of the upper GC spectrum, and an MS chart, respectively. Thereafter, the same applies to FIGS. FIG. 7 is a graph showing changes in the treatment time with the aqueous sodium hydroxide solution and the residual amount of the BHC pesticide on the decomposition treatment of the BHC pesticide. FIG. 8 is a diagram showing a change in the treatment time of the aqueous sodium hydroxide solution and the natural logarithm of the relative concentration of the residual amount of the BHC pesticide on the decomposition treatment of the BHC pesticide. Table 1 is a table showing changes in the treatment time with the aqueous sodium hydroxide and the BHC pesticide decomposition on the decomposition treatment of the BHC pesticide. Table 2 is a table | surface which shows the change of the processing time by the sodium hydroxide aqueous solution and the peak of a BHC pesticide which have an influence on the decomposition process of a BHC pesticide.

  Since phenanthrene is stable in alkaline aqueous solution, the relative concentration of BHC pesticide is determined by comparing the peak of BHC pesticide with the peak of phenanthrene. The chart shown in FIG. 2 is each GC spectrum chart showing the analysis results of the solution after neutralizing the sodium hydroxide aqueous solution of BHC pesticide and phenanthrene with hydrochloric acid at time zero. As shown in FIG. 2, a BHC peak was clearly detected at a retention time of 8.40 min, and a phenanthrene peak was also detected at 8.50 min.

  3 to 6 are GC / MS measurement results of the mixed aqueous solution when the treatment time of the aqueous sodium hydroxide solution was 5, 10, 20 and 30 min, respectively.

  As shown in FIGS. 3 to 8 and Tables 1 and 2, it was found that the concentration of the BHC pesticide gradually decreased as the treatment time of the aqueous sodium hydroxide solution increased. In particular, in FIG. 8, the natural logarithm of the relative concentration of the BHC pesticide is linear with respect to the decomposition time, indicating that the decomposition reaction of the BHC pesticide in a 0.1 M sodium hydroxide aqueous solution proceeds with a simple primary reaction. Indicates. For this reason, it was found that the half time of the decomposition reaction of the BHC pesticide was 7.1 min at room temperature in a 0.1 M sodium hydroxide aqueous solution. From this result, it was judged that BHC pesticides can be efficiently decomposed in an alkaline aqueous solution.

(Example 5)
A. Treatment procedure An aqueous solution containing organochlorine compounds (BHC pesticide and DDT pesticide) was placed in a treatment vessel, and then a 0.1 M aqueous sodium hydroxide solution was added. Next, 0.2% by weight of acetophenone relative to water was added as a photosensitizer, and ultraviolet irradiation with a low-pressure mercury lamp was performed for 2 hours (second decomposition step).

  A small amount of the treatment solution irradiated with ultraviolet rays for 2 hours was taken out, and the aqueous solution was extracted with hexane. Thereafter, the extract was vacuum evaporated at 50 ° C. with an evaporator, and the extract was further dissolved in 2 ml of hexane to prepare a sample for measuring a GC / MS spectrum. Moreover, in order to confirm the residual state of the organochlorine compound after the decomposition treatment with sodium hydroxide or the product after the decomposition, a small amount of the mixture stock solution before the decomposition treatment was taken out. The stock solution was extracted with hexane, the residue was dissolved with 2 ml of hexane, and this was used as a sample for GC / MS spectrum measurement.

B. Analysis Results FIG. 9 and FIG. 10 show the analysis results of the agricultural chemical decomposition treatment by ultraviolet irradiation.

  FIG. 9 is a GC spectrum and MS chart showing the analysis results of the stock solution before the decomposition treatment. As shown in FIG. 9, a BHC peak was clearly detected in the vicinity of the retention time of 8.25 min, and a DDT peak was also detected in the vicinity of 10 to 11 min.

  FIG. 10 is a GC / MS measurement result of the treatment liquid when the treatment time by ultraviolet irradiation is 2 hours.

  In the decomposition treatment by ultraviolet irradiation in a 0.1 M sodium hydroxide aqueous solution, the DDT signal that does not show the decomposition effect by the treatment with the sodium hydroxide aqueous solution until 1/100 after performing ultraviolet irradiation for 2 hours. Diminished. From the results of Example 6, it was determined that the BHC pesticide and the DDT pesticide can be efficiently removed simultaneously by the treatment method of the present invention.

Example 6
A. Treatment procedure 0.2% by weight acetone with respect to water is added as a photosensitizer to an aqueous solution in equilibrium with the actual buried pesticide containing BHC pesticide and DDT pesticide, and ultraviolet irradiation with a low-pressure mercury lamp is performed. It went for 1 hour.

  A small amount of the treatment solution irradiated with ultraviolet rays for 1 hour was taken out, and the aqueous solution was extracted with hexane. Thereafter, the extract was vacuum evaporated at 50 ° C. with an evaporator, and the extract was further dissolved in 2 ml of hexane to prepare a sample for measuring a GC / MS spectrum. Moreover, in order to confirm the residual state of the organochlorine compound after the decomposition treatment by ultraviolet irradiation or the product after the decomposition, a small amount of the mixture stock solution before the decomposition treatment was taken out. The stock solution was extracted with hexane, the residue was dissolved with 2 ml of hexane, and this was used as a sample for GC / MS spectrum measurement.

B. Analysis Results FIG. 11 is a chart of GC spectra and MS showing analysis results of the stock solution before the decomposition treatment. As shown in FIG. 11, a BHC peak was clearly detected at a retention time of 8.25 min, and a DDE peak was also detected in the vicinity of 10 min and two DDT peaks were detected in the vicinity of 10.3 to 10.6 min.

  FIG. 12 shows a GC / MS measurement result of the treatment liquid when the treatment time by ultraviolet irradiation is 1 hour.

  As shown in FIG. 12, although ultraviolet irradiation was performed for 1 hour in an aqueous solution, the BHC signal changed by about ½, but the DDT signal almost disappeared. From this result, it was judged that BHC can be decomposed by ultraviolet irradiation in water, but DDT can be decomposed more efficiently.

  INDUSTRIAL APPLICATION This invention can be utilized in the industry which processes the soil contaminated with heavy metals to detoxification.

It is a flowchart which shows the procedure of the wet detoxification processing method of the contaminated soil which concerns on this invention. In Example 4 of this invention, it is a GC spectrum chart which shows the analysis result of the process liquid which is not decomposed | disassembled by sodium hydroxide aqueous solution (upper part: GC spectrum chart, lower part: the enlarged chart of the upper chart). In Example 4 of this invention, it is each chart of GC spectrum and MS which shows the analysis result of the processing liquid after performing decomposition processing by sodium hydroxide aqueous solution for 5 minutes (upper part: GC spectrum chart, middle part: upper part of chart of the upper part) Enlarged chart, bottom: MS chart). In Example 4 of this invention, it is each GC spectrum and MS chart which show the analysis result of the process liquid after performing the decomposition process by sodium hydroxide aqueous solution for 10 minutes (the upper part: GC spectrum chart, the middle part: upper part of the chart of the upper part) Enlarged chart, bottom: MS chart). In Example 4 of this invention, it is each chart of GC spectrum and MS which shows the analysis result of the processing liquid after performing decomposition processing by sodium hydroxide aqueous solution for 20 minutes (upper part: GC spectrum chart, middle part: upper part of chart of the upper part) Enlarged chart, bottom: MS chart). In Example 4 of this invention, it is each chart of GC spectrum and MS which shows the analysis result of the processing liquid after performing the decomposition process by sodium hydroxide aqueous solution for 30 minutes (upper part: GC spectrum chart, middle part: upper part of the chart of the upper part) Enlarged chart, bottom: MS chart). It is a figure which shows the change of the processing time by the sodium hydroxide aqueous solution and the BHC pesticide residual amount which influence on the decomposition process of BHC pesticide. It is a figure which shows the change with the natural logarithm of the processing time by the sodium hydroxide aqueous solution and the relative density | concentration of BHC pesticide residual amount affecting the decomposition process of BHC pesticide. In Example 5 of this invention, it is each chart of GC spectrum and MS which shows the analysis result of the undiluted | stock solution before a decomposition process (the upper part: GC spectrum chart, the middle part: the enlarged chart of the upper chart, the lower part: MS chart). In Example 5 of this invention, it is each chart of GC spectrum and MS which shows the analysis result of the process liquid after performing the decomposition process by ultraviolet irradiation in water for 2 hours (upper part: GC spectrum chart, middle part: upper chart) (Lower chart: MS chart). In Example 6 of this invention, it is each chart of GC spectrum and MS which shows the analysis result of the undiluted | stock solution before a decomposition process (the upper part: GC spectrum chart, the middle part: the enlarged chart of the upper chart, the lower part: MS chart). In Example 6 of this invention, it is each chart of GC spectrum and MS which shows the analysis result of the process liquid after performing the decomposition process by ultraviolet irradiation in water for 1 hour (upper part: GC spectrum chart, middle part: upper chart) (Lower chart: MS chart).

Claims (7)

A method for detoxifying contaminated soil containing heavy metals and organochlorine compounds,
Mixing at least the aqueous solution containing hydrogen peroxide and acid into the contaminated soil, and eluting the heavy metal ions into the mixed solution, and adding an alkaline compound to the aqueous solution containing the organochlorine compound A contaminated soil, comprising: a first decomposition step for decomposing and a second decomposition step for mixing the organochlorine compound and a photosensitizer, and decomposing the organochlorine compound by ultraviolet irradiation. Wet detoxification treatment method. The elution step includes a first step of mixing an aqueous solution containing at least hydrogen peroxide,
The wet detoxification of contaminated soil according to claim 1, further comprising a step of treating heavy metal ions comprising a second step of mixing an acid in the mixture of the aqueous solution and the contaminated soil. Processing method.   Furthermore, in the said 1st process, an alkaline compound is added and pH of the said aqueous solution is made larger than 7, The wet detoxification method of the contaminated soil of Claim 2 characterized by the above-mentioned.   The method for wet detoxification of contaminated soil according to any one of claims 1 to 3, wherein the alkaline compound is sodium hydroxide or potassium hydroxide.   The method for wet detoxification of contaminated soil according to any one of claims 1 to 4, wherein the heavy metals are one or more heavy metals selected from the second type specific harmful substances.   2. The wet detoxification method for contaminated soil according to claim 1, wherein the contaminated soil containing the organic chlorine compound is further brought into contact with a surfactant to elute the organic chlorine compound.   2. The wet detoxification method for contaminated soil according to claim 1, wherein the photosensitizer is acetophenone or acetone.

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