CN114214071A

CN114214071A - Composition for treating chlorinated hydrocarbon in polluted soil and application thereof

Info

Publication number: CN114214071A
Application number: CN202111345916.7A
Authority: CN
Inventors: 朱长银; 黄铭泉; 王镝翔; 陈宁; 方国东; 周东美
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2021-11-15
Filing date: 2021-11-15
Publication date: 2022-03-22
Anticipated expiration: 2041-11-15
Also published as: CN114214071B

Abstract

A composition for treating chlorohydrocarbon in polluted soil and application thereof are disclosed, wherein under the heating condition (30-60 ℃), the pH of soil is firstly adjusted, chloralkane in the soil is converted into chloroalkene through elimination reaction under the action of heat and alkali, sodium Persulfate (PS) is added after the pH of the soil is reduced, and PS is activated by heat for oxidation. The conventional heat activated PS can only degrade unsaturated hydrocarbons (such as trichloroethylene and the like) in chlorinated hydrocarbons, and has extremely poor repairing effect on chlorinated alkanes (such as tetrachloroethane). The technology utilizes two treatment methods of coupling heat, alkali conversion and heat activated PS oxidation, can efficiently degrade various chlorinated hydrocarbon compound contaminated soil and reduce the dosage of a repairing medicament, has the advantages of high repairing efficiency, convenient operation, environmental friendliness, low cost and the like, and provides wide prospects for repairing halogenated organic contaminated soil.

Description

Composition for treating chlorinated hydrocarbon in polluted soil and application thereof

Technical Field

The invention belongs to the technical field of soil remediation, and particularly relates to a method for quickly and efficiently treating chlorohydrocarbon-polluted soil and application thereof.

Background

The chlorohydrocarbon is a general name of a compound obtained by replacing one or more hydrogen in hydrocarbon molecules by chlorine, mainly refers to 1-carbon and 2-carbon chlorinated organic matters, has the characteristics of stable chemical property, low boiling point, small viscosity, difficult water solubility and the like, and is a common organic solvent and a product intermediate. However, because of improper storage and disposal, thousands of field soil and underground water pollution in the world are caused, and the pollution is a toxic and harmful substance which seriously pollutes the environment. Among them, tetrachloroethane, dichloromethane, trichloroethylene and the like are organic pollutants with extremely high detection rate in field soil and underground groundwater. Persulfate (PS) -based advanced oxidation is a new technology developed in recent years, and is widely applied to in-situ remediation of soil and underground water. PS can be activated by a variety of methods to produce highly reactive sulfate radicals (SO)₄ ^·-) Having a higher oxidation-reduction potential (E)⁰2.6-3.0V), can degrade pollutants such as dyes, chlorophenols, medicines and the like rapidly, wherein thermal activation is a common PS activation method, and can activate PS efficiently to degrade organic pollutants in soil. For chlorinated hydrocarbons, different types of chlorinated hydrocarbons are reacted with SO₄ ^·-The reactivity of oxidizing free radicals is greatly different, chloro olefin pollutants (such as trichloroethylene, dichloroethylene and the like) are easily oxidized and degraded due to unsaturated double bonds in molecules, and chloro alkane (such as trichloroethane, tetrachloroethane and the like) has low carbon chain electron density and is difficult to be oxidized and degraded. Because a large amount of organic matters exist in the soil, the organic matters compete with pollutants for oxidative free radicals, so that the degradation of the pollutants is inhibited, and the inhibition effect on the chlorinated alkane pollutants which are difficult to degrade and the organic matters in the soil is more obvious. Therefore, the conventional PS oxidation technology is difficult to treat chloralkane pollutants in soil.

Alkali activation is also a common PS activation technology, and PS is firstly added into polluted soil in the remediation process, and then an activator liquid alkali is added to initiate a free radical reaction and degrade pollutants. However, higher pH conditions (pH) are required for alkali activation>Basic activity of 12Chemolysis effect), in addition, the PS decomposition process releases a large amount of H⁺Therefore, a large amount of alkali needs to be added into the soil to maintain the high pH value of the soil in the reaction process, but the ecological function is damaged by the excessively high pH value, so that the restored soil is strong in alkalinity, and a large amount of acid needs to be added in the later period to adjust the pH value of the soil in the practical application process. For example, the invention CN106753386A in China discloses a method for treating organophosphorus pesticide contaminated soil by using alkali activated PS, and the concentration of the required alkali is as high as 2-7M.

At present, a plurality of patents for degrading organic pollutants in soil by using oxidative free radicals generated by activated PS exist in China, for example, the Chinese invention CN201611200096.1 discloses a method for removing organochlorine pesticides in soil by using ferrous iron and hydrogen peroxide activated PS; the CN201711440570.2 invention in China utilizes heating, hydrogen peroxide and chelating transition metal to activate PS to remove semi-volatile organic pollutants in soil; according to the invention, CN201710966738.7 in China applies a direct current electric field to test the directional migration of PS in soil, and utilizes an alternating current electric field to generate heat to activate PS to generate sulfate radicals to degrade pollutants. However, there are few patents for degrading chlorinated hydrocarbons in soil using activated PS, and these patents are mainly directed to chlorinated alkenes among chlorinated hydrocarbons, which are more easily degraded. For example, CN201310270204.2 in China degrades trichloroethylene in soil by activating PS through ferroferric oxide powder. The development of a repair technology capable of efficiently degrading chloralkane in soil is urgently needed.

Disclosure of Invention

The technical problem to be solved is as follows: the invention provides a method for degrading a composition of chlorinated hydrocarbon in soil and application thereof, aiming at solving the pollution problem of the chlorinated hydrocarbon in the soil.

The technical scheme is as follows: a composition for treating chlorinated hydrocarbon in polluted soil contains sodium hydroxide and sodium persulfate as effective components.

The concentration of sodium hydroxide is 0.01-0.1M, and the concentration of sodium persulfate is 0.05-0.2M.

The application of the composition in treating soil polluted by chlorohydrocarbon.

The chlorinated hydrocarbon is contaminated with chloroform, dichloroethane, trichloroethane, tetrachloroethane, 1,2, 2-tetrachloroethane, pentachloroethane or mono/polychlorinated olefinsThe concentration of chlorinated hydrocarbon is not higher than 100 mg/kg^-1。

The application method comprises the specific steps of firstly heating the soil to 30-60 ℃, adding a sodium hydroxide solution, adjusting the pH of the soil to 8-12, adding a sodium persulfate solution after the chlorinated alkane is converted into chlorinated alkene, and degrading the chlorinated alkene by utilizing the thermally activated persulfate.

The principle of the invention is that alkali is added through thermal coupling to adjust soil to be in alkalescence (pH is 8-12), so that chloralkane is subjected to elimination reaction to remove hydrogen chloride and is converted into chloroalkene; during the thermal activation of PS, persulfate ions are decomposed under the heating condition to generate SO₄ ^·-The method has good degradation effect on chlorinated olefin generated after elimination reaction, and can rapidly degrade chlorinated hydrocarbon. The advantages of this coupling technique are mainly three-fold: 1) the addition of alkali can promote the chlorinated alkane to eliminate hydrogen chloride and convert the hydrogen chloride into chlorinated alkene, and the heating can further accelerate the conversion of the chlorinated alkane and reduce the dosage of the alkali; 2) can avoid the problem that the PS is decomposed to produce H in the traditional operation process of activating the PS by alkali⁺The consumption of alkali and the rapid decomposition of PS under strong alkaline conditions and the like, and the dosage of alkali and PS is reduced; 3) the low alkali dosage can avoid the damage of the ecological function of the soil due to overhigh pH value, and the subsequent addition of PS for acid production can neutralize the influence caused by alkali addition.

S₂O₈ ^2-+ heating → 2SO₄ ^·- (1)

C₂H₂Cl₄+OH^-→C₂HCl₃+Cl^-+H₂O (2)

C₂HCl₃+SO₄ ^·-→CO₂+H₂O+SO₄ ^2- (3)

Has the advantages that: (1) the invention is based on i) comparing the simple thermal activation of persulfate to produce SO₄ ^·-The degradation effect of the chlorinated paraffin on chlorinated paraffin is not as good as that of chlorinated olefin, so that the chlorinated paraffin is removed by hydrogen chloride through elimination reaction and is converted into the chlorinated olefin through the addition of alkali; ii) in contrast to the alkali activation, the amount of alkali used in the treatment process can theoretically beThe reduction is 80%. Therefore, the technology has strong degradation capability on the chlorinated hydrocarbon in the soil and can save the cost. (2) The alkali added in the previous step can be neutralized with PS (decomposed to produce acid) added in the next step, and the pH value of the treated soil is close to neutral, so that the influence on the soil is small. (3) The main degradation product of the chlorinated hydrocarbon in the invention is CO₂And Cl^-The degradation is more thorough. (4) The method is simple to operate, low in cost, suitable for degradation treatment of chlorinated hydrocarbons in soil and large-scale engineering application, and good in applicability.

Drawings

FIG. 1 thermal activation of PS for comparison of trichloroethylene degradation with 1,1,2, 2-tetrachloroethane (hereinafter tetrachloroethane refers to 1,1,2, 2-tetrachloroethane);

FIG. 2 conversion of tetrachloroethane at ambient temperature (30 ℃ C.) at different pH conditions;

figure 3 effect of temperature on tetrachloroethane conversion: wherein a is 40 ℃ and b is 50 ℃;

FIG. 4 shows the influence of stepwise addition of base and PS (thermobase coupled thermal activation PS technique) and simultaneous addition of base and PS on the degradation of tetrachloroethane (tetrachloroethane has reacted rapidly to trichloroethylene after addition of base);

FIG. 5 effect of PS concentration on trichloroethylene degradation by heat activated PS;

FIG. 6 effect of temperature on degradation of trichloroethylene by heat activated PS;

FIG. 7 is a diagram for verifying the applicability of the thermal-base coupled thermal activation PS technology to the degradation of chloroform, dichloroethane, trichloroethane and 1,1,1, 2-tetrachloroethane (isomers of tetrachloroethane);

FIG. 8 the effect of base concentration on the degradation of trichloroethylene by heat activated PS (with addition of base, PS);

FIG. 9 effect of base concentration on degradation of tetrachloroethane by heat activated PS (simultaneous addition of base, PS);

FIG. 10 is a diagram for verifying applicability of hot alkali in a static state to convert tetrachloroethane;

FIG. 11 is a graph for verifying applicability, in which the conversion of chloroform, dichloroethane, trichloroethane and 1,1,1, 2-tetrachloroethane (isomer of tetrachloroethane) by hot alkali in a static state is examined.

Detailed Description

Example 1

The degradation of tetrachloroethane and trichloroethylene in soil was explored. And (3) investigating the degradation effect of the heat activated PS on tetrachloroethane and trichloroethylene in soil. A9 mL brown bottle (with a polytetrafluoroethylene gasket on the cover) is used as a reaction container, 2g of contaminated soil is weighed into the reaction container, the concentration of tetrachloroethane is 16.8mg/kg, the concentration of trichloroethylene is 13.1mg/kg, the prepared PS solution is added, and water is added to ensure that the concentration of PS is 0.05M, and the volume of the solution is 4 mL. The reaction flask is placed in a reciprocating shaking box at 250rpm, the temperature is 50 ℃, and the reaction lasts for 3 days.

The results are shown in FIG. 1, which shows that PS activated by heat alone has a good effect of degrading trichloroethylene (about 80%), but has a poor effect of degrading tetrachloroethane (about 20%). This is mainly because trichloroethylene has unsaturated double bonds and is easily degraded by oxidation.

Example 2

The effect of pH (7-10) on the conversion of tetrachloroethane (without PS) was examined using phosphoric acid (pH 7) and boric acid buffer (

pH

8,9,10) at 30 ℃. A9 mL brown bottle (cap with Teflon pad) was used as a reaction vessel, the concentration of tetrachloroethane in the solution was 16.8mg/L, the concentration of buffer was 10mM, and the volume of the solution was 4 mL. The reaction flask is placed in a reciprocating oscillation box at 250rpm and reacted for 12 hours.

As a result, as shown in fig. 3, after 12 hours of reaction, tetrachloroethane was not significantly converted under

pH

7 and 8, the conversion rate of tetrachloroethane was 50% under pH 9, and tetrachloroethane was completely converted under pH 10, and the conversion product was mainly trichloroethylene. The result shows that the conversion of tetrachloroethane can be accelerated by increasing the pH of the solution, wherein the conversion of tetrachloroethane is obvious when the pH is 9-10.

Example 3

The effect of temperature (40 ℃ to 50 ℃) on the conversion effect of tetrachloroethane (without PS) was examined using phosphoric acid (pH 7) and boric acid buffer (

pH

8,9, 10). A9 mL brown bottle (cap with Teflon pad) was used as a reaction vessel, the concentration of tetrachloroethane in the solution was 16.8mg/L, the concentration of buffer was 10mM, and the volume of the solution was 4 mL. The reaction flask is placed in a reciprocating oscillation box at 250rpm and reacted for 12 hours.

As a result, as shown in FIG. 3, the conversion rates of tetrachloroethane at

pH

7,8 and 9 were 5,12 and 76.3% respectively after the reaction for 12 hours at a reaction temperature of 40 ℃ and the conversion rate of tetrachloroethane at pH 10 after the reaction for 2 hours reached 96%; when the reaction temperature is 50 ℃, the conversion rate of tetrachloroethane is 35% and 53% when the reaction temperature is 12h and the reaction time is 4h and 1h when the reaction temperature is 9 and 10, respectively, after the reaction time is 12h, the tetrachloroethane can be completely converted. The results show that at different temperatures, increasing the pH favors the conversion of tetrachloroethane; at the same pH, the temperature is increased to facilitate the conversion of tetrachloroethane; when the temperature is increased to 50 ℃, the dosage of alkali can be greatly reduced, and when the pH is 7 and 8, tetrachloroethane has obvious conversion.

Example 4

The degradation of tetrachloroethane in soil was explored. The degradation effect of adding alkali/PS simultaneously and adding alkali/PS sequentially step by step on tetrachloroethane in soil is compared under the conditions that the solid-liquid ratio is 1:2, the concentration of PS is 0.05M and the concentration of sodium hydroxide is 0.01M. Using a 9mL brown bottle (with a polytetrafluoroethylene gasket on the cover) as a reaction vessel, weighing 2g of contaminated soil into the reaction vessel, wherein the concentration of tetrachloroethane is 16.8mg/kg, a) firstly adding sodium hydroxide and adding water to ensure that the concentration of the sodium hydroxide is 0.01-0.05M, and the volume of the solution is 4 mL. Placing the reaction bottle in a reciprocating oscillation box at the speed of 250rpm, reacting for 6 hours at the temperature of 50 ℃, cooling, adding PS into the bottle, and reacting for 42 hours; b) and adding the prepared sodium hydroxide and PS solution into a reaction bottle at the same time to ensure that the concentration of the sodium hydroxide is 0.01M and the concentration of the PS is 0.05M, placing the reaction bottle in a reciprocating oscillation box with 250rpm, and reacting for 2 days at the temperature of 50 ℃.

The results are shown in fig. 4, with simultaneous dosing: when sodium hydroxide (10mM) and PS are mixed and added into the system, the degradation rate of tetrachloroethane is about 20% after reaction for 2d, and only when the concentration of sodium hydroxide is 50mM, tetrachloroethane can be completely converted into trichloroethylene, and the degradation rate of the trichloroethylene is 69% (figure 4 a); adding step by step: after the sodium hydroxide is added for reaction for 6 hours, the tetrachloroethane is completely converted into trichloroethylene, and then PS (figure 4b) is added, so that the oxidative degradation rate of the trichloroethylene by the PS reaches 93 percent. The results show that the stepwise addition can significantly promote the degradation of tetrachloroethane and reduce the amount of alkali.

Example 5

The degradation of trichloroethylene in soil is explored. The solid-liquid ratio is 1:2, the PS concentration is 0.05M, the temperature is 50 ℃, the aerobic condition is initially adopted, and the influence of the PS concentration (0.01-0.05M) on the removal of trichloroethylene by thermally activating PS is examined. A9 mL brown bottle (with a polytetrafluoroethylene gasket on the cover) is used as a reaction vessel, the trichloroethylene concentration is 13.1mg/kg, 2g of polluted soil is weighed into the reaction vessel, the prepared PS solution is added, and water is added, wherein the volume of the solution is 4 mL. The reaction flask was placed in a reciprocating shaker box at 250 rpm.

As shown in FIG. 5, the degradation rate of trichloroethylene reached 48% after 2 days of reaction at a PS concentration of 0.01M, and increased to 64%, 83% and 91% by increasing the PS concentrations to 25, 50 and 75 mM. The results show that increasing the concentration of PS promotes the degradation of trichloroethylene.

Example 6

The degradation of trichloroethylene in soil is explored. The influence of temperature (30-60 ℃) on the removal of trichloroethylene by thermally activating PS is examined under the conditions that the solid-liquid ratio is 1:2 and the PS concentration is 0.05M. A9 mL brown bottle (with a polytetrafluoroethylene gasket on the cover) is used as a reaction vessel, the trichloroethylene concentration is 13.1mg/kg, 2g of contaminated soil is weighed into the reaction vessel, the prepared PS solution is added, and water is added to ensure that the PS concentration is 0.05M and the volume of the solution is 4 mL. The reaction bottle is placed in a reciprocating oscillation box at 250rpm, the temperature is 30-60 ℃, and the reaction lasts for 2 days.

As shown in fig. 6, the degradation rate of the thermally activated PS to trichloroethylene reaches about 80% at 50 ℃, and the degradation rate of the thermally activated PS to trichloroethylene reaches about 98% at 60 ℃, so that the temperature rise is helpful for the degradation effect of the thermally activated PS to trichloroethylene, and the optimal reaction temperature is 50-60 ℃. The degradation of the trichloroethylene can be increased by raising the temperature and increasing the PS, relatively speaking, the promotion effect of the raising the temperature on the degradation of the trichloroethylene is more obvious, and the using amount of the agent can be reduced by raising the temperature in the soil remediation process.

Example 7

The effect of pH on the conversion of chloroform, dichloroethane and trichloroethane in the solution (without adding PS) was examined. A9 mL brown bottle (with a polytetrafluoroethylene gasket on the cap) was used as a reaction vessel, the chloroform concentration in the solution was 11.9mg/L, the dichloroethane concentration was 9.9mg/L, the trichloroethane concentration was 13.3mg/L, the pH of the solution was adjusted directly with sodium hydroxide, and the volume of the solution was 4 mL. The reaction bottle is placed in a reciprocating oscillation box with 250rpm, the temperature is 50 ℃, and the reaction lasts 12 hours.

As shown in FIG. 7, after 12 hours of reaction, only tetrachloroethane was significantly converted at pH 10, chloroform and trichloroethane were both significantly converted at elevated pH 12, whereas dichloroethane was more difficult to convert. The results show that increasing the solution pH accelerates the conversion of chlorinated hydrocarbons, while lower chlorinated hydrocarbons are relatively more difficult to convert and require higher pH.

Example 8

To determine whether the base plays a role in activating PS or converting chloroalkane in the process, the effect of the base concentration on the degradation of trichloroethylene in soil by thermally activated PS was investigated (with addition of base, PS). The solid-liquid ratio is 1:2, the PS concentration is 0.05M, the concentration ratio of sodium hydroxide to PS is 0:1, 1:1 and 4:1, and the influence of the addition of sodium hydroxide on the degradation of trichloroethylene in soil by heat-activated PS is compared. A9 mL brown bottle (a cover is provided with a polytetrafluoroethylene gasket) is used as a reaction container, the concentration of trichloroethylene is 13.1mg/kg, 2g of polluted soil is weighed into the reaction bottle, prepared sodium hydroxide and PS solution are simultaneously added into the reaction bottle, the concentration of PS is 0.05M, the concentration ratio of sodium hydroxide to PS is 0:1, 1:1 and 4:1, the volume of the solution is 4mL, the reaction bottle is placed in a reciprocating oscillation box with the speed of 250rpm, the temperature is 50 ℃, and the reaction is carried out for 2 days.

As shown in FIG. 8, when no sodium hydroxide is added, i.e., the concentration ratio of sodium hydroxide to PS is 0:1, the degradation rate of trichloroethylene in the thermally activated PS system is 78%; the addition of sodium hydroxide instead reduced the degradation rate of trichloroethylene, which was only 17% when the concentration ratio of sodium hydroxide to PS was 4: 1. Since trichloroethylene cannot continue to dehydrochlorinate at this pH, the conversion of the base is excluded. The literature reports that during degradation of contaminants by base-activated PS, the degradation rate of the contaminants increases with increasing base concentration. In the present case, the degradation of trichloroethylene is inhibited as the concentration of alkali increases, indicating that alkali is not the activation in the traditional sense in the technology, and the addition of alkali is not beneficial to the oxidative degradation of pollutants.

Example 9

The effect of alkali concentration on the degradation of tetrachloroethane by heat-activated PS was examined (simultaneous addition of alkali and PS). The solid-liquid ratio is 1:2, the sodium hydroxide concentration is 0,0.05 and 0.2M respectively, the PS concentration is 0.05M, namely the concentration ratio of the sodium hydroxide to the PS is 0:1, 1:1 and 4:1, and the influence of the adding amount of the sodium hydroxide on the degradation of trichloroethylene in the soil by the heat-activated PS is compared. A9 mL brown bottle (a cover is provided with a polytetrafluoroethylene gasket) is used as a reaction container, the concentration of tetrachloroethane is 16.8mg/kg, 2g of polluted soil is weighed into the reaction bottle, prepared sodium hydroxide and PS solution are added into the reaction bottle at the same time, the concentration of PS is 0.05M, the concentration ratio of sodium hydroxide to PS is 0:1, 1:1 and 4:1, the reaction bottle is placed in a reciprocating oscillation box at 250rpm, the temperature is 50 ℃, and the reaction lasts for 2 days.

As a result, as shown in FIG. 9, the increase of the alkali concentration by 4 times did not promote the degradation of tetrachloroethane, and the best degradation effect was achieved only with tetrachloroethane at an appropriate ratio (1: 1). It is therefore believed that at the appropriate base-oxidant ratio, the tetrachloroethane conversion is complete and the product trichloroethylene is converted by thermal activation of the PS degradation. The sodium hydroxide and the PS are added simultaneously, and the excessive sodium hydroxide (4:1) inhibits the degradation of the thermally activated PS to the tetrachloroethane, mainly because the excessive sodium hydroxide can remarkably promote the decomposition of the PS, and in addition, the decomposition of the PS can produce acid to neutralize the alkalinity of the sodium hydroxide, thereby reducing the conversion effect to the tetrachloroethane. The results further prove that the hot-alkali conversion coupling PS oxidation technology is not used for adjusting the conventional alkali activation PS technology, the two technologies are completely different, and the hot-alkali conversion coupling PS oxidation technology has a better degradation effect on chlorinated hydrocarbon and obviously reduces the dosage of a medicament.

Example 10

The conversion of tetrachloroethane in soil by hot alkali treatment in a standing state is explored. The solid-liquid ratio is 1:1, the concentration of sodium hydroxide is 0.1M, the temperature is 50 ℃, the aerobic condition is initially adopted, and the influence of the simulated actual site medicament injection condition on the tetrachloroethane conversion effect is investigated. A9 mL brown bottle (a cover is provided with a polytetrafluoroethylene gasket) is used as a reaction container, the concentration of tetrachloroethane is 16.8mg/kg, 5g of polluted soil is weighed into the reaction container, prepared sodium hydroxide solution is added, water is added, the volume of the solution is 5mL, and no headspace exists in the bottle. The reaction flask was placed in a water bath at 50 ℃ and reacted for 2 days.

The results are shown in fig. 10, tetrachloroethane can be completely converted within two hours in the standing state, the experiment can simulate the real state of an actual polluted site injected with the reagent, and it can be seen that the influence of the standing experiment on the tetrachloroethane conversion reaction is small.

Example 11

The conversion of chloroform, dichloroethane, trichloroethane, and 1,1,1, 2-tetrachloroethane in the soil by hot alkali treatment in a standing state was investigated. The solid-liquid ratio is 1:1, the concentration of sodium hydroxide is 0.1M, the temperature is 50 ℃, the initial aerobic condition is adopted, and the influence on the conversion effect of chloroform, dichloroethane, trichloroethane and 1,1,1, 2-tetrachloroethane under the condition of simulating the injection of the medicament in an actual field is investigated. A9 mL brown bottle (with a polytetrafluoroethylene gasket on the cover) is used as a reaction container, the chloroform concentration is 11.9mg/kg, the dichloroethane concentration is 9.9mg/kg, the trichloroethane concentration is 13.3mg/kg, 5g of contaminated soil is weighed into the reaction container, the prepared PS solution is added, water is added, the volume of the solution is 5mL, and no headspace exists in the bottle. The reaction flask is placed in a water bath at 50 ℃ for reaction for 6 h.

The results are shown in fig. 11, the conversion rates of chloroform, dichloroethane, trichloroethane and 1,1,1, 2-tetrachloroethane in the standing state are respectively 78%, 24%, 100% and 100% within two hours, the experiment can simulate the real state of an actual polluted site injected with the medicament, and it can be seen that the standing experiment has little influence on other chlorohydrocarbon conversion reactions.

The results can be known that the action of alkali cannot be ignored in the technology of thermal alkali coupling PS oxidation degradation of chlorinated hydrocarbon, so when the technology is used for repairing the soil polluted by chlorinated hydrocarbon, the dosage of alkali needs to be controlled, and after chlorinated alkane is completely converted into chlorinated alkene, the coupled thermal activation PS technology oxidizes and mineralizes the converted chlorinated alkene, thereby achieving the purpose of removing the chlorinated hydrocarbon in the soil.

Claims

1. The composition for treating chlorinated hydrocarbon in polluted soil is characterized by comprising the effective components of sodium hydroxide and sodium persulfate.

2. The composition for treating chlorinated hydrocarbons in contaminated soils according to claim 1, characterized by a sodium hydroxide concentration of 0.01 to 0.1M and a sodium persulfate concentration of 0.05 to 0.2M.

3. Use of a composition according to claim 1 or 2 for treating soil contaminated with chlorinated hydrocarbons.

4. Use according to claim 3, characterized in that the chlorinated hydrocarbon contamination is chloroform, dichloroethane, trichloroethane, tetrachloroethane, 1,2, 2-tetrachloroethane, pentachloroethane or mono/polychlorinated olefins, the concentration of chlorinated hydrocarbon being not higher than 100 mg-kg^-1。

5. The use according to claim 3, characterized in that the soil is heated to 30-60 ℃, sodium hydroxide solution is added, the pH of the soil is adjusted to 8-12, sodium persulfate solution is added after the chlorinated alkane is converted into chlorinated alkene by elimination reaction, and the chlorinated alkene is degraded by using the thermally activated persulfate.