CN116618065B - Preparation method and application of biochar composite materials for in-situ remediation of organically contaminated sites - Google Patents

Abstract

The invention is a preparation method and application of biochar composite materials for in-situ remediation of organic contaminated sites. This method uses corn straw, ferrous iron salt and sodium thiosulfate as raw materials. First, the ferrous iron salt and sodium thiosulfate are dissolved in water, and then a certain amount of corn straw is added, and then evaporated, dried, roasted and cooled , to prepare a biochar composite material that can efficiently catalyze persulfate in-situ remediation of organic contaminated sites. The biochar composite material of the present invention has long-term catalytic activity, and compared with iron-doped biochar, it can achieve efficient degradation of organic pollutants when the amount of carbon material is reduced by 20% to 50%. Significantly reduces in-situ repair costs.

Description

Preparation method and application of biochar composite materials for in-situ remediation of organically contaminated sites

Technical field

The invention belongs to the technical field of remediation of organic contaminated sites, and specifically relates to a preparation method and application of biochar composite materials for in-situ remediation of organic contaminated sites.

Background technique

Site organic pollution has always been a focus of concern at home and abroad because of its harm to the ecological environment and human health. In-situ remediation technology does not require excavation of contaminated soil and has the advantages of good economy, low risk of pollutant diffusion, and small changes in soil quality. It is widely used in the field of organically contaminated site remediation. Commonly used in-situ repair technologies include in-situ resistance heating thermal desorption technology, in-situ microbial technology, and in-situ chemical oxidation/reduction technology. Among them, persulfate (PS) chemical oxidation technology has the advantages of high oxidation efficiency, mild reaction conditions, and easy transportation and storage of PS. It is widely used for in-situ oxidation remediation of organic contaminated sites.

The key to PS oxidation technology is the generation of strong oxidizing free radicals through activation. Fe(II) is a commonly used catalyst for activating PS. It has the advantages of low price, wide source, safety and non-toxicity. However, the applicable pH range of directly using Fe(Ⅱ) to catalyze PS is acidic (pH 3~4). For near-neutral and alkaline organic polluted sites, Fe(Ⅱ) will precipitate with ^OH-, greatly reducing the catalytic ability. , it is difficult to effectively remove organic pollutants in the site. Studies have found that biochar loaded with Fe(Ⅱ) has good catalytic activation of PS. This is because: 1) Loading Fe(Ⅱ) on biochar can reduce the leaching and precipitation losses of Fe(Ⅱ), and can be used in a wide pH range. catalyze PS within the range (pH 3~9); 2) The oxygen-containing functional groups on the surface of biochar have a synergistic catalytic effect on PS.

When biochar with a single load of Fe (Ⅱ) is used, Fe (Ⅱ) on the biochar reacts with PS to generate SO ₄ ^- ·, and at the same time, Fe (Ⅱ) will be converted into Fe (Ⅲ), and Fe (Ⅲ) provides The ability of electrons to activate PS is weakened, making it difficult to sustain the catalytic activity of the catalyst. Therefore, the development of catalysts with long-lasting catalytic activity to activate PS has become a research hotspot in the in-situ oxidation remediation of organic contaminated sites by PS.

Contents of the invention

The invention provides a preparation method of biochar composite materials for in-situ remediation of organic contaminated sites and its application in in-situ remediation of organic contaminated sites. Loading sulfur on iron-doped biochar can increase the conductivity of the biochar material, and at the same time, the Fe (III) generated during the reaction can be reduced to Fe (II), so that the biochar composite material remains resistant to PS for a long time. Has good catalytic properties.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A method for preparing biochar composite materials for in-situ remediation of organically contaminated sites. The method uses corn straw, ferrous iron salts, and sodium thiosulfate as raw materials. First, the ferrous iron salts and sodium thiosulfate are dissolved in water, and then A certain amount of corn straw is added, and through evaporation, drying, roasting, and cooling, a biochar composite material that can efficiently catalyze PS in-situ repair of organic contaminated sites is prepared; the evaporation is stirring evaporation under water bath heating conditions, and the roasting The conditions are: raise the temperature to 350~450℃ in a _CO2 atmosphere, keep it for 0.5-2h, and then raise the temperature to 550~800℃ for roasting for 0.5-2h.

The ferrous iron salt is a water-soluble ferrous iron salt, such as at least one of ferrous sulfate, ferrous chloride, ferrous nitrate, etc.

Among them, the mass percentage of each component of the preferred raw materials is: corn straw 70%~85%, ferrous iron salt 5%~20%, and sodium thiosulfate 10%.

The specific steps of the above-mentioned preparation method of biochar composite materials for in-situ remediation of organically contaminated sites are:

1) Mixing of raw materials: Dissolve 5% to 20% of the total mass of ferrous iron salts and 10% of sodium thiosulfate in enough deionized water to obtain a mixed solution; crush the corn stalks and pass through 80 mesh ~200 mesh sieve, and then add the sieved corn straw to the mixed solution. The added amount of corn straw is 70% ~ 85%, and stir to form a solid-liquid mixture;

The sufficient amount of deionized water means that it can completely dissolve the divalent iron salt and sodium thiosulfate, and at the same time, it can fully soak the added corn straw to form a solid-liquid mixture;

2) Evaporation: Heat and stir in a water bath to fully evaporate the water in the solid-liquid mixture to nearly dryness. The temperature of the water bath heating is set to make the water evaporate quickly and at the same time, the iron species in the system are mainly in the form of Fe (Ⅱ). Yes, there is a small amount of Fe(III);

3) Drying: Place the evaporated material in an oven at 60°C to remove the remaining moisture to constant weight;

4) Roasting: Roast the material after removing moisture, raise the temperature to 350~450℃ in a _CO2 atmosphere, keep it for 0.5-2 h, then raise the temperature to 550~800℃ and continue roasting for 0.5-2 h;

5) Cooling: Stop roasting and cool for 6-12 hours to obtain biochar composite material.

Preferably, the heating rate in the CO ₂ atmosphere is 5~15°C/min, and the final temperature of the CO ₂ atmosphere is 600~800°C, including but not limited to 650°C, 700°C, 750°C, 780°C, etc.

Preferably, the water bath heating temperature in step 2) is 50~70°C;

The above-mentioned biochar composite material is used to catalyze PS in-situ remediation of organically contaminated soil. Deionized water and biochar composite material are mixed into a homogenate, and then the oxidant PS is prepared into a solution and injected into the organically contaminated soil. After reacting for 5 to 10 days, soil samples are taken to extract the organic pollutants. After analysis and detection, the residual organic pollutant content in the soil is calculated. Among them, the concentration of organic pollutants in the soil is 50~500 mg/kg, and the concentration of the biochar composite added to the soil is 1~5 g/kg (the mass of the biochar composite added to 1kg of soil is 1~5 g/kg). 5g), the concentration of the persulfate solution is 1~5 g/L, the injection rate of the agent (biochar composite material and PS) is 5 mL/min, and the mass ratio of the biochar composite material and PS dosage is preferably 1:1~ 1:1.7.

Use the above-mentioned biochar composite material to remediate organically contaminated groundwater in situ. Add the catalyst biochar composite material and oxidant PS to the organically contaminated groundwater. Mix evenly and react for 24 to 48 hours. Take the water sample after the reaction. After detection and analysis , calculate the residual organic pollutant content in the water body. Among them, the concentration of organic pollutants in groundwater is 50~500 mg/L, the concentration of biochar composite added to the water is 0.3~1.5 g/L, and the concentration of oxidant PS is 0.2~2 g/L. The biochar composite The material has good catalytic performance for PS within 24 hours, and the mass ratio of biochar composite material and PS dosage is preferably 1:2~1:2.5.

The organically contaminated soil is soil contaminated by benzene series (such as benzene, toluene) or chlorinated hydrocarbons (such as 1,2-dichloroethane, trichloroethylene), and the organically contaminated groundwater is contaminated by phenolic pollutants. (such as phenol, 2,4-dichlorophenol) contaminated groundwater.

Compared with the prior art, the beneficial effects of the present invention are:

1) The biochar composite material of the present invention has long-lasting catalytic activity. The biochar composite material prepared by the present invention overcomes the previous limitation of using Fe(II) to catalyze PS to generate Fe(III), which makes it difficult to cycle to produce new Fe(II), resulting in unsustainable catalytic effect. In the first stage of roasting, sodium ^thiosulfate decomposes anaerobically to generate S ^2- , which can reduce Fe(Ⅲ) to Fe(Ⅱ), thereby improving the catalytic activity of the biochar composite material. In addition, S ^2- on the surface of the biochar composite material will combine with Fe(Ⅱ), causing Fe(Ⅱ) to slowly release and react with PS to generate SO ₄ ^- · during the catalytic reaction process, which significantly improves the long-term durability of the biochar composite material. Catalytic performance of PS.

2) The biochar composite material of the present invention can significantly reduce the cost of in-situ repair. Compared with iron-doped biochar, the biochar composite material prepared by the present invention can achieve efficient degradation of organic pollutants in soil under the condition that the amount of biochar composite material added is reduced by 20% to 50%, significantly reducing The cost of in-situ repair is reduced.

Detailed ways

In order to better understand the content of the present invention, the present invention will be further described below in conjunction with the embodiments, but the examples cited do not limit the scope of protection of the present invention.

The present invention uses divalent iron salt and sodium thiosulfate as raw materials to dope and modify carbon-based materials. On the premise of greatly improving the PS catalytic efficiency, it can also reduce the amount of catalyst and significantly reduce the repair cost, and the biological Carbon composites can continuously catalyze PS over a longer period of time. Experiments have shown that the catalytic performance of biochar composite materials in catalyzing PS in removing organic pollutants is significantly stronger than that of PS alone. Under the same conditions, it is also significantly better than the catalytic effect of a single carbon-based material doped with iron or sulfur.

Example 1: (1) The preparation method of biochar composite materials for in-situ remediation of organically contaminated sites in this example is a method of preparing biochar composite materials using corn straw, ferrous sulfate and sodium thiosulfate as raw materials. The specific preparation method is Proceed as follows:

1) Mixing of raw materials: Dissolve 10% of ferrous sulfate and 10% of sodium thiosulfate equivalent to the total mass of raw materials in 100 mL of deionized water to obtain a mixed solution. Crush the corn stalks and pass them through a sieve of 80 to 200 mesh. Then add the sieved corn straw to the mixed solution. The amount of corn straw added is 80% (the mass ratio of corn straw, ferrous sulfate and sodium thiosulfate is 8:1:1). After stirring evenly, the solid solution is obtained. liquid mixture;

2) Evaporation: Use a constant-temperature water bath to heat and stir the water in the above solid-liquid mixture to fully evaporate to nearly dryness. The water bath temperature is 60°C;

3) Drying: Place the evaporated material in an oven at 60°C to remove the remaining moisture to constant weight;

4) Roasting: Roast the material after removing the moisture, raise the temperature to 350°C in a CO ₂ atmosphere, keep it for 1 hour, then raise the temperature to 600°C and continue roasting for 1 hour;

5) Cooling: Stop roasting and cool for 6 hours to obtain biochar composite material.

(2) Experiments on in-situ remediation of organically contaminated soil:

The above biochar composite materials were used to remediate toluene contaminated soil. The specific steps of the experimental process are as follows:

In the toluene-contaminated soil described in the embodiment of the present invention, the concentration of toluene is 250 mg/kg.

Use the above-mentioned biochar composite material to remediate toluene-contaminated soil in situ. Add 1.5 g of biochar composite material to 200 mL of deionized water to mix into a homogenate. Add 1.5 g of sodium persulfate to 200 mL of deionized water to prepare a solution for later use. The biochar composite material was first injected into a plexiglass column containing 1 kg of toluene-contaminated soil (the inner diameter of the plexiglass column was 8 cm and the height was 30 cm) at an injection rate of 5 mL/min. Then inject the sodium persulfate solution into the above-mentioned contaminated soil at an injection rate of 5 mL/min. Let it stand for 120 hours to continue reacting. Take a soil sample every 12 hours to extract the toluene in it. After analysis and detection, the concentration of toluene remaining in the soil is calculated.

The results showed that the reaction end point was reached after 120 hours, and the residual toluene concentration in the soil was 21.8 mg/kg, and the removal rate of toluene in the soil was 91.3%.

Example 2: The preparation method of biochar composite materials for in-situ remediation of organically contaminated sites in this example is the same as Example 1, except that the mass ratio of corn straw, ferrous sulfate and sodium thiosulfate is 7:2 :1.

The above biochar composite materials were used to remediate toluene contaminated soil. In the toluene-contaminated soil described in the embodiment of the present invention, the concentration of toluene is 250 mg/kg, and the experimental process is the same as in Example 1.

The results showed that the reaction end point was reached after 120 hours, the concentration of toluene in the soil was 53.7 mg/kg, and the removal rate of toluene in the soil was 78.5%.

Example 3: (1) The preparation method of biochar composite materials in this example uses corn straw, ferrous sulfate and sodium thiosulfate as raw materials. The specific steps are as follows:

1) Mixing of raw materials: Dissolve 5% of ferrous sulfate and 10% of sodium thiosulfate equivalent to the total mass of raw materials in 100 mL of deionized water to obtain a mixed solution. Crush the corn straw and pass it through a 80-200 mesh sieve. Then add the sieved corn straw to the mixed solution. The amount of corn straw added is 85% (the mass ratio of corn straw, ferrous sulfate and sodium thiosulfate is 17:1:2). After stirring evenly, the solid solution is obtained. liquid mixture;

2) Evaporation: Use a constant-temperature water bath to heat and stir the water in the above solid-liquid mixture to fully evaporate to nearly dryness. The water bath temperature is 60°C;

3) Drying: Place the above evaporated material in an oven at 60°C to remove the remaining moisture to constant weight;

4) Roasting: Roast the material after removing moisture, raise the temperature to 350°C in a CO ₂ atmosphere, keep it for 1 hour, then raise the temperature to 600°C and continue roasting for 2 hours;

5) Cooling: Stop roasting and cool for 6 hours to obtain biochar composite material.

(2) Experiments on in-situ remediation of organically contaminated soil:

The above biochar composite materials were used to remediate toluene contaminated soil. In the toluene-contaminated soil described in the embodiment of the present invention, the concentration of toluene is 250 mg/kg, and the experimental process is the same as in Example 1.

The results showed that the reaction end point was reached after 120 hours, the concentration of toluene in the soil was 43.8 mg/kg, and the removal rate of toluene in the soil was 82.5%.

Example 4: In this example, the biochar composite material in Example 1 is used for in-situ remediation of 1,2-dichloroethane contaminated soil.

In the 1,2-dichloroethane contaminated soil described in the embodiment of the present invention, the concentration of 1,2-dichloroethane is 250 mg/kg.

Use the above-mentioned biochar composite material to remediate 1,2-dichloroethane contaminated soil in situ. Add 1.5 g of biochar composite material to 200 mL of deionized water and mix into a homogenate. Add 1.5 g of sodium persulfate to 200 mL of deionized water. Prepare a solution for later use. First, the homogenate of the biochar composite catalytic material was injected into a plexiglass column containing 1 kg of 1,2-dichloroethane-contaminated soil (the inner diameter of the plexiglass column was 8 cm and the height was 30 cm), and the injection rate was 5 mL/min. Then inject the sodium persulfate solution into the above-mentioned contaminated soil at an injection rate of 5 mL/min. Let it stand for 120 hours and continue to react. Take a soil sample every 12 hours to extract the 1,2-dichloroethane. After analysis and detection, the concentration of 1,2-dichloroethane remaining in the soil is calculated.

The results showed that when the reaction endpoint was reached after 120 hours, the concentration of 1,2-dichloroethane remaining in the soil was 11.5 mg/kg, and the removal rate of 1,2-dichloroethane in the soil was 95.4%.

Example 5: In this example, the biochar composite material in Example 2 is used for in-situ remediation of 1,2-dichloroethane contaminated soil.

In the 1,2-dichloroethane contaminated soil described in the embodiment of the present invention, the concentration of 1,2-dichloroethane is 250 mg/kg. The experimental process is the same as Example 4.

The results showed that the reaction end point was reached after 120 hours, and the concentration of 1,2-dichloroethane remaining in the soil was 61.0 mg/kg, so the removal rate of 1,2-dichloroethane in the soil was 75.6%.

Example 6: In this example, the biochar composite material in Example 3 is used for in-situ remediation of 1,2-dichloroethane contaminated soil.

In the 1,2-dichloroethane contaminated soil described in the embodiment of the present invention, the concentration of 1,2-dichloroethane is 250 mg/kg. The experimental process is the same as Example 4.

The results showed that the reaction end point was reached after 120 hours, and the concentration of 1,2-dichloroethane remaining in the soil was 38.3 mg/kg, so the removal rate of 1,2-dichloroethane in the soil was 84.7%.

Example 7: In this example, the biochar composite material in Example 1 is used for in-situ remediation of organically contaminated groundwater, specifically for the removal of phenol in groundwater.

The embodiment of the present invention treats groundwater contaminated by phenol, and the concentration of phenol is 50 mg/L. The specific experimental steps are:

Add 20 mg of biochar composite material and 50 mg of persulfate into 100 mL of phenol-contaminated groundwater with a concentration of 50 mg/L, stir for 24 h, and react at 1 h, 3 h, 6 h, 12 h, and 24 h respectively. sampling. After analysis and detection, the concentration of residual phenol in the groundwater was calculated.

The results showed that when the reaction endpoint was reached after 24 hours, the residual phenol concentration in groundwater was 3.8 mg/L, and the removal rate of phenol in groundwater was 92.4%.

Example 8: In this example, the biochar composite material in Example 2 is used for in-situ remediation of groundwater contaminated by phenol.

In the groundwater contaminated by phenol according to the embodiment of the present invention, the concentration of phenol is 50 mg/L. The experimental process is the same as Example 7.

The results showed that when the reaction endpoint was reached after 24 hours, the residual phenol concentration in groundwater was 9.4 mg/L, and the removal rate of phenol in groundwater was 81.2%.

Example 9: In this example, the biochar composite material in Example 3 is used for in-situ remediation of groundwater contaminated by phenol.

In the groundwater contaminated by phenol according to the embodiment of the present invention, the concentration of phenol is 50 mg/L. The experimental process is the same as Example 7.

The results showed that when the reaction endpoint was reached after 24 hours, the residual phenol concentration in groundwater was 32.5 mg/L, and the removal rate of phenol in groundwater was 85.1%.

In order to more intuitively display the data changes in Examples 1-6, as shown in Table 1:

The initial concentration of toluene and 1,2-dichloroethane in the contaminated soil is: 250 mg/kg, the concentration of the biochar composite added to the soil is: 1.5 g/kg, and the concentration of the sodium persulfate solution is: 7.5 g/L , reaction time 5 d.

In order to more intuitively display the data changes in Examples 7-9, as shown in Table 2:

The initial concentration of phenol in groundwater is 50 mg/L, the concentration of biochar composite added to groundwater is: 0.2g/L, the concentration of sodium persulfate solution is: 0.5g/L, and the reaction time is 24 h.

Comparative Example 1: The biochar composite material in Example 1 was replaced with a biochar material doped with ferrous sulfate, and was used for in-situ remediation of toluene-contaminated soil according to the conditions in Example 1, that is, no sulfur was added in this comparative example. substitute sodium sulfate, and the remaining steps are the same as in Example 1.

The results showed that the reaction end point was reached after 48 hours. The concentration of toluene remaining in the soil was 73 mg/kg, and the removal rate was 60.8%.

Comparative Example 2: The biochar composite material in Example 1 was replaced with sodium thiosulfate-doped biochar material, and used for in-situ remediation of toluene-contaminated soil according to the conditions in Example 1, that is, no addition was made in this comparative example. Ferrous sulfate, the remaining steps are the same as in Example 1.

The results showed that the reaction end point was reached after 48 hours. The concentration of toluene remaining in the soil was 211.5 mg/kg, and the removal rate was 15.4%.

Comparative Example 3: The roasting atmosphere in Example 1 was changed to N ₂ , other conditions were the same as Example 1, and the conditions in Example 1 were used for in-situ remediation of toluene-contaminated soil.

The results showed that the reaction end point was reached after 120 hours, and the residual toluene concentration in the soil was 180.3 mg/kg, so the removal rate of toluene in the soil was 72.1%.

Comparative Example 4: The roasting conditions in Example 1 were changed to no staged roasting under _CO2 atmosphere, and the temperature was directly raised to 600°C and maintained for 2 h. Other conditions were the same as Example 1. Use the conditions as in Example 1. In-situ remediation of toluene-contaminated soil.

The results showed that the reaction end point was reached after 72 hours, the concentration of toluene remaining in the soil was 117.3 mg/kg, and the removal efficiency of toluene in the soil was 53.1%.

Comparative Example 5: Step 2) in Example 1 was changed to stirring with a magnetic stirrer for 6 hours and then dried in an oven at 60°C. Other conditions were the same as Example 1 and used in situ according to the conditions in Example 1. Remediation of toluene contaminated soil.

The results showed that the reaction end point was reached after 120 hours, the concentration of toluene remaining in the soil was 96.5 mg/kg, and the removal efficiency of toluene in the soil was 61.4%.

The present invention uses corn straw, ferrous sulfate and sodium thiosulfate as raw materials, and under a specific method, prepares a cheap, environmentally friendly and efficient biochar composite material for catalytic PS in-situ repair of organic contaminated sites. Experimental results show that the biochar composite material can effectively remove organic pollutants in both soil and groundwater, and the effective catalytic time of the catalyst for PS in soil is 120 h, and the effective catalytic time for PS in groundwater is 24 h, and Under the same conditions, the process operation within the given parameter range of the present invention can significantly improve the removal efficiency of pollutants, have the advantages of less catalyst usage and long action time, and significantly reduce the use cost.

The parts not described in the present invention are applicable to the existing technology.

Claims (8)

1. The application of a biochar composite material in catalytic persulfate in-situ remediation of organic contaminated sites, which is characterized by using corn straw, ferrous iron salts, and sodium thiosulfate as raw materials. First, the ferrous iron salts, sulfur Sodium sulfate is dissolved in water, and then corn straw is added. After evaporation, drying, roasting, and cooling, a biochar composite material for highly efficient catalytic persulfate in-situ repair of organic contaminated sites is prepared; the evaporation is performed under water bath heating conditions. Stir and evaporate. The roasting conditions are: raise the temperature to 350~450°C in a CO ₂ atmosphere, keep it for 0.5-2h, then raise the temperature to 550~800°C and roast for 0.5-2h; The mass percentage of each component of the raw material is: corn straw 70%~85%, ferrous iron salt 5%~20%, and sodium thiosulfate 10%. 2. The application according to claim 1, characterized in that the divalent iron salt is at least one of ferrous sulfate, ferrous chloride or ferrous nitrate. 3. Application according to claim 1, characterized in that the specific steps of the preparation method are: 1) Mixing of raw materials: Dissolve 5% to 20% of the total mass of ferrous iron salts and 10% of sodium thiosulfate in enough deionized water to obtain a mixed solution; crush the corn stalks and pass through 80 mesh ~200 mesh sieve, and then add the sieved corn straw into the mixed solution. The added amount of corn straw is 70% ~ 85%, and stir evenly to form a solid-liquid mixture; 2) Evaporation: Heat and stir the water bath to fully evaporate the water in the solid-liquid mixture. The temperature of the water bath is set to enable rapid evaporation of water while allowing the iron species in the system to exist in the form of Fe (Ⅱ); 3) Drying: Place the evaporated material in an oven at 50~70°C to remove the remaining moisture to constant weight; 4) Roasting: Roast the material after removing moisture, raise the temperature to 350~450℃ in a _CO2 atmosphere, keep it for 0.5~2 h, then raise the temperature to 550~800℃ and continue roasting for 0.5~2 h; 5) Cooling: Stop roasting and cool for 6~12 hours to obtain biochar composite material. 4. The preparation method according to claim 3, characterized in that the heating rate under the _CO2 atmosphere is 5~15°C/min, the heating end temperature of the _CO2 atmosphere is 550~700°C; the water bath heating temperature is 50~70℃. 5. An application of the biochar composite material according to claim 1, characterized in that the biochar composite material is used to catalyze persulfate in-situ repair of organic contaminated soil: deionized water and the biochar composite material are mixed evenly. slurry, and then prepare a solution of persulfate and inject it into the organically contaminated soil; react for 5 to 10 days, take soil samples to extract the organic pollutants, and calculate the concentration of residual organic pollutants in the soil; Among them, the concentration of organic pollutants in the soil is 50~500 mg/kg, the concentration of biochar composite added to the soil is 1~5 g/kg, the concentration of persulfate solution is 1~5 g/L, and the concentration of biochar composite added to the soil is 1~5 g/L. The injection rate of carbon composite and persulfate was 5 mL/min. 6. The application according to claim 5, characterized in that the mass ratio of the biochar composite material and persulfate dosage is 1:1~1:1.7; the organically contaminated soil is benzene-based or chlorine-containing Soil contaminated by hydrocarbons, the benzene series is at least one of benzene and toluene, and the chlorinated hydrocarbon is at least one of 1,2-dichloroethane and trichlorethylene. 7. An application of the biochar composite material according to claim 1, characterized in that the biochar composite material is used to repair organically contaminated groundwater in situ: the biochar composite material and persulfate are added to the organically contaminated groundwater. , mix evenly and react for 24 to 48 hours, take the water sample after the reaction, and calculate the concentration of residual organic pollutants in the groundwater; Among them, the concentration of organic pollutants in the groundwater is 50~500 mg/L, the concentration of the biochar composite added to the groundwater is 0.3~1.5 g/L, and the concentration of persulfate is 0.2~2 g/L, as described The biochar composite material had good catalytic performance against persulfate within 24 h. 8. The application according to claim 7, characterized in that the mass ratio of the biochar composite material and persulfate dosage is 1:2~1:2.5; the organically polluted groundwater is contaminated by phenolic pollutants. of groundwater, and the phenolic pollutant is at least one of phenol and 2,4-dichlorophenol.