Preparation method and application of heavy metal contaminated soil remediation agent

Abstract

The invention belongs to the technical field of heavy metal pollution treatment, and relates to a preparation method and application of a heavy metal polluted soil remediation agent. The heavy metal contaminated soil remediation agent mainly comprises the following components in parts by weight: 20-30 parts of alkali modified cotton straw biochar, 5-10 parts of sepiolite, 15-20 parts of humic acid and 5-10 parts of calcium silicate. The heavy metal contaminated soil remediation agent can effectively remove mercury, arsenic, cadmium and / or lead pollution in heavy metal contaminated soil and improve the heavy metal contaminated soil environment. After the soil remediation agent is used for treating the heavy metal cadmium contaminated soil, the pH value of the soil can be increased, absorption and enrichment of crops to cadmium and lead are reduced, and the method is a novel bioremediation method which is low in cost, efficient, simple, convenient and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal pollution control and relates to a preparation method and application of a heavy metal polluted soil repair agent. Background Art

[0002] With the rapid development of modern agriculture, industry and transportation, a variety of heavy metals have accumulated in the ecological environment, causing damage to soil biodiversity, exacerbating the destruction of resources, and threatening the safety and health of organisms. This is an issue that needs to be addressed urgently. Pollution from heavy metals such as nickel (Ni), lead (Pb), cobalt (Co), cadmium (Cd), manganese (Mn), chromium (Cr), and zinc (Zn) is becoming more and more serious. Soil heavy metal pollution is hidden, cumulative, lagging, and irreversible. Excessive concentration of heavy metals will not only affect crop growth, but also enrich through the food chain and ultimately endanger human health.

[0003] Common methods for remediating soil heavy metal pollution include physical remediation, chemical remediation, biological remediation and combined remediation. Among them, physical remediation engineering measures are costly, plant remediation cycles are too long, and microbial remediation technology is not yet mature. The most widely used method in practice is chemical passivation remediation technology. Chemical passivation remediation technology is to apply passivators to the soil to reduce the bioavailability and mobility of heavy metals in the soil through processes such as adsorption, precipitation, complexation, ion exchange and oxidation-reduction.

[0004] Scholars at home and abroad mainly conduct research on the remediation of contaminated soil through physical, chemical, biological and other methods. Due to differences in the physical and chemical properties of soil, types of heavy metal pollution, and degree of pollution, the remediation effect is not ideal. It is necessary to further expand comprehensive research methods to reduce heavy metal residues, reduce heavy metal toxicity, improve ecological restoration efficiency, beautify the living environment, and eliminate the adverse effects of pollution. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a preparation method and application of a heavy metal contaminated soil remediation agent, which can effectively remove mercury, arsenic, cadmium and / or lead pollution in heavy metal contaminated soil and effectively improve the heavy metal contaminated soil environment.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a heavy metal contaminated soil remediation agent, which mainly comprises the following components by weight: 20-30 parts of alkali-modified cotton straw biochar, 5-10 parts of sepiolite, 15-20 parts of humic acid and 5-10 parts of calcium silicate.

[0008] Furthermore, the heavy metal contaminated soil remediation agent mainly includes the following components by weight: 25 parts of alkali-modified cotton straw biochar, 8 parts of sepiolite, 10 parts of humic acid and 7 parts of calcium silicate.

[0009] In a second aspect, the present invention provides a method for preparing the heavy metal contaminated soil remediation agent, the preparation method comprising:

[0010] (1) Preparation of alkali-modified cotton straw biochar: The cotton straw was naturally air-dried, crushed and sieved through a 20-mesh sieve, and the sieved cotton straw was dried in an oven at 60°C; the cotton straw was mixed with MgCl2 and stirred vigorously for 6 h, filtered and dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tubular furnace and heated to 700°C at a heating rate of 10°C / min, and calcined at high temperature under nitrogen for 1-1.5 h to obtain alkali-modified cotton straw biochar.

[0011] (2) The biochar, sepiolite, humic acid and calcium silicate are mixed and ground to obtain a heavy metal contaminated soil remediation agent.

[0012] Furthermore, the concentration of MgCl2 in step (1) is 0.5 mol / L.

[0013] Furthermore, in the step (1), the mass volume ratio of cotton straw to MgCl2 is 1 g: (10 mL-20 mL).

[0014] Furthermore, in the step (1), the mass volume ratio of cotton straw to MgCl2 is 1 g: 15 mL.

[0015] Furthermore, in step (1), high temperature calcination is carried out under nitrogen conditions for 1 hour.

[0016] In a third aspect, the present invention provides the use of the heavy metal contaminated soil remediation agent obtained by the above preparation method in in-situ remediation of heavy metal contaminated soil.

[0017] In a fourth aspect, the present invention provides a method for using the heavy metal contaminated soil remediation agent, which comprises applying the heavy metal contaminated soil remediation agent to heavy metal contaminated soil and tilling the soil.

[0018] Furthermore, when the application environment is potted plants, the application amount of the heavy metal contaminated soil remediation agent is 2%-5% of the weight of the potted soil; when the application environment is a field, the application amount of the heavy metal contaminated soil remediation agent is 140-220 kg / mu.

[0019] Furthermore, the heavy metal pollution is mercury, arsenic, cadmium and / or lead pollution.

[0020] Biochar is a highly aromatic, carbon-rich solid material made from agricultural waste, animal biomass or sludge and other solid wastes through thermochemical conversion or chemical pyrolysis under anoxic conditions. Biochar is generally alkaline, has a large porosity and specific surface area, and contains a large number of oxygen-containing functional groups such as phenolic hydroxyl and carboxyl. Biochar can improve the adsorption and conversion capacity of soil for heavy metals, reduce the effectiveness of heavy metals, and promote the remediation of heavy metal-contaminated soil, but the remediation effect is closely related to the preparation material, pyrolysis temperature, and addition ratio. Modified biochar is prepared by modification of metal salts or metal oxides, acids, bases and organic compounds. The modification treatment can change the specific surface area, redox activity, functional group abundance and other properties of biochar, and shows great application potential in fixing soil heavy metals. Sepiolite is a silicate mineral belonging to the glauconite peridotite mineral group. Due to its large porosity and specific surface area, it has good adsorption and ion exchange properties and can be effectively used to treat heavy metal pollution in water bodies. Humic acid is a negatively charged, weakly acidic colloid, but the edges of humic acid are positively charged, and the surface of clay crystals in the soil is negatively charged, so the soil can adsorb humic acid colloid. Since most metal ions are positively charged, humic acid combines with soil colloids to enhance the adsorption of heavy metals in the soil. Calcium silicate is a porous material, and its pore structure can provide a large amount of adsorption surface area, which is conducive to the adsorption of heavy metal ions. In addition, calcium silicate also has a high chemical reaction activity and can react chemically with heavy metal ions to form stable adsorption products. The adsorption mechanism of calcium silicate for heavy metal ions mainly includes two forms: surface adsorption and ion exchange. In surface adsorption, heavy metal ions produce physical adsorption with the adsorption sites on the surface of active calcium silicate. The present invention combines the above four components to show a significant synergistic effect in heavy metal contaminated soil, and has a significant effect in removing mercury, arsenic, cadmium and / or lead pollution.

[0021] Beneficial effects achieved by the present invention:

[0022] After being treated with the soil remediation agent of the present invention, the contents of effective mercury and arsenic in the soil are significantly reduced.

[0023] After treating soil contaminated with heavy metal cadmium, the soil remediation agent of the present invention can increase the pH value of the soil, significantly reduce the effectiveness of heavy metal cadmium and lead in the soil, and reduce the absorption and enrichment of cadmium and lead by crops. It is a low-cost, efficient, simple and environmentally friendly new bioremediation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for the specific implementation methods are briefly introduced below.

[0025] Figure 1is the passivation rate of the heavy metal contaminated soil remediation agent of the present invention on mercury pollution

[0026] Compared with the CK group, * P<0.05, ** P<0.01; compared with group A, # P<0.05, ## P<0.01.

[0027] Figure 2 is the passivation rate of the heavy metal contaminated soil remediation agent of the present invention on arsenic pollution

[0028] Compared with the CK group, * P<0.05, ** P<0.01; compared with group A, # P<0.05, ## P<0.01.

[0029] Figure 3 The influence of the heavy metal contaminated soil remediation agent of the present invention on the soil pH value

[0030] Compared with the CK group, * P<0.05.

[0031] Figure 4 Effect of the heavy metal contaminated soil remediation agent of the present invention on cadmium accumulation in the tuberous roots of Tripterygium wilfordii

[0032] Compared with the CK group, * P<0.05, ** P<0.01; compared with group A, # P<0.05, ## P<0.01.

[0033] Figure 5 Effect of the heavy metal contaminated soil remediation agent of the present invention on the lead accumulation in the tuberous roots of Tripterygium wilfordii

[0034] Compared with the CK group, * P<0.05, ** P<0.01; compared with group A, # P<0.05, ## P<0.01. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. The test reagents used in the following embodiments, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0036] Example 1 Heavy metal contaminated soil remediation agent and preparation method thereof

[0037] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 25 parts of alkali-modified cotton straw biochar, 8 parts of sepiolite, 10 parts of humic acid and 7 parts of calcium silicate.

[0038] The preparation method is as follows: (1) Preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:15 mL, and stir vigorously for 6 hours, filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1-1.5 hours to obtain alkali-modified cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0039] Example 2 Heavy metal contaminated soil remediation agent and preparation method thereof

[0040] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 30 parts of alkali-modified cotton straw biochar, 10 parts of sepiolite, 15 parts of humic acid and 10 parts of calcium silicate.

[0041] The preparation method is as follows: (1) Preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:20 mL, and stir vigorously for 6 hours, filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1.5 hours to obtain alkali-modified cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0042] Example 3 Heavy metal contaminated soil remediation agent and preparation method thereof

[0043] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 25 parts of alkali-modified cotton straw biochar, 10 parts of sepiolite, 15 parts of humic acid and 8 parts of calcium silicate.

[0044] The preparation method is as follows: (1) Preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:10 mL, and stir vigorously for 6 hours, filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1.5 hours to obtain alkali-modified cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0045] Example 4 Heavy metal contaminated soil remediation agent and preparation method thereof

[0046] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 30 parts of alkali-modified cotton straw biochar, 5 parts of sepiolite, 20 parts of humic acid and 5 parts of calcium silicate.

[0047] The preparation method is as follows: (1) Preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and then dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:15 mL, and stir vigorously for 6 hours, then filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1 hour to obtain alkali-modified cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0048] Example 5 Heavy metal contaminated soil remediation agent and preparation method thereof

[0049] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 20 parts of alkali-modified cotton straw biochar, 10 parts of sepiolite, 15 parts of humic acid and 10 parts of calcium silicate.

[0050] The preparation method is as follows: (1) Preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and then dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:15 mL, and stir vigorously for 6 hours, then filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1 hour to obtain alkali-modified cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0051] Comparative Example 1 Heavy metal contaminated soil remediation agent and preparation method thereof

[0052] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 25 parts of cotton straw biochar, 8 parts of sepiolite, 10 parts of humic acid and 7 parts of calcium silicate.

[0053] The preparation method is as follows: (1) Preparation of cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, dry the sieved cotton straw in an oven at 60°C, place the cotton straw in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature for 1-1.5h under nitrogen conditions to obtain cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0054] Comparative Example 2 Heavy metal contaminated soil remediation agent and preparation method thereof

[0055] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 25 parts of alkali-modified peanut shell biochar, 8 parts of sepiolite, 10 parts of humic acid and 7 parts of calcium silicate.

[0056] The preparation method is as follows: (1) Preparation of alkali-modified peanut shell biochar: air-dry the peanut shell naturally, crush it and pass it through a 20-mesh sieve, and dry the sieved peanut shell in an oven at 60°C; mix the peanut shell with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:15 mL, and stir vigorously for 6 hours, filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1-1.5 hours to obtain alkali-modified peanut shell biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0057] Comparative Example 3 Heavy metal contaminated soil remediation agent and preparation method thereof

[0058] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 25 parts of alkali-modified cotton straw biochar, 8 parts of red mud, 10 parts of humic acid and 7 parts of calcium silicate.

[0059] The preparation method is as follows: (1) Preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:15 mL, and stir vigorously for 6 hours, filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1-1.5 hours to obtain alkali-modified cotton straw biochar; (2) mix the biochar, red mud, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0060] Comparative Example 4 Heavy metal contaminated soil remediation agent and preparation method thereof

[0061] The heavy metal contaminated soil remediation agent mainly includes the following components by weight: 15 parts of alkali-modified cotton straw biochar, 15 parts of sepiolite, 10 parts of humic acid and 15 parts of calcium silicate.

[0062] The preparation method is as follows: (1) Preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with 0.5 mol / L MgCl2 at a mass volume ratio of 1 g:15 mL, and stir vigorously for 6 hours, filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature under nitrogen for 1-1.5 hours to obtain alkali-modified cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain a heavy metal contaminated soil remediation agent.

[0063] Test Example 1: Restoration effect of the remediation agent of the present invention on mercury-arsenic contaminated soil

[0064] 1. Experimental Methods

[0065] The test soil was mercury-arsenic contaminated soil, taken from an abandoned chemical plant area, with a water content of 21.5% and a pH of 7.5. The effective content of mercury and arsenic in the soil was determined by the EDTA one-step extraction method. The effective mercury content in the soil was 12.37 mg / kg, and the effective arsenic content was 63.54 mg / kg.

[0066] The collected soil samples were air-dried, crushed and sieved through a 20-mesh sieve. The method of indoor soil cultivation was used to set up 7 treatments: control group (CK group), embodiment 1 group (A group), embodiment 2 group (B group), comparative example 1 group (C group), comparative example 2 group (D group), comparative example 3 group (E group), comparative example 4 group (F group). Each treatment was set up with 3 replicates and passivated for 21 days.

[0067] The test soil sample without the repair agent was used as the control group, and the repair agents prepared by Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 were used in groups AF, respectively, with a mass percentage of 2.5%. The soil moisture was maintained at a moisture content of about 55%, and the culture vessel was covered with plastic wrap, placed in a dark place, and kept away from light for 24 hours.

[0068] 2. Determination of available mercury and arsenic content in soil

[0069] The repaired soil was collected and the passivation rate was determined, and the heavy metal remediation effect was analyzed based on the passivation rate.

[0070] Passivation rate = (effective content of heavy metals before restoration - effective content of heavy metals after restoration) / effective content of heavy metals before restoration.

[0071] 3. Data processing

[0072] The data results are the mean ± standard deviation of 3 replicates. SPSS19.0 software was used for statistical analysis, Duncan method was used for difference significance analysis, and Graphpad Prism 7.0 software was used for plotting.

[0073] 4. Determination results of soil available mercury and arsenic content

[0074] like Figure 1 , 2 As shown in the figure, after restoration, compared with CK without restoration agent, the effective mercury and arsenic content in the soil was significantly reduced in Group A and Group B after restoration agent treatment. The passivation efficiency of effective mercury and arsenic in Group A was 79.2% and 85.1%, respectively, and the passivation efficiency of effective mercury and arsenic in Group B was 74.5% and 83.8%, respectively. The effect of Group A and Group B in reducing the effective mercury and arsenic content in the soil was significantly better than that of Group C, Group D, Group E, and Group F.

[0075] Test Example 2: Restoration effect of the soil remediation agent of the present invention on composite contaminated soil

[0076] 1. Experimental Methods

[0077] The test soil was collected from the surface soil of a heavy metal-contaminated farmland. The soil pH was 6.48 and the organic matter content was 24.76 g / kg.

[0078] The total cadmium content and the total lead content in the soil samples were determined by graphite furnace atomic absorption spectrophotometry in the "Determination of Lead and Cadmium in Soil Quality" (GB / T 17141-1997), and the determination of effective cadmium and effective lead in soil was determined by atomic absorption spectrophotometer in the "Determination of Effective Lead and Cadmium in Soil Quality" (GB / T 23739-2009). The total cadmium content in the soil was 2.17 mg / kg, and the effective cadmium was 1.05 mg / kg; the total lead content was 139.54 mg / kg, and the effective lead was 62.05 mg / kg.

[0079] The collected soil samples were air-dried, crushed and sieved through a 20-mesh sieve. Five treatments were set up: control group (CK group), Example 1 group (A group), comparative example 1 group (B group), comparative example 2 group (C group), comparative example 3 group (D group). Three replicates were set up for each treatment, for a total of 15 pots. The test soil sample without the repair agent was used as the control group, and the AD group used the repair agent prepared by Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 with a mass fraction of 2.5%, respectively.

[0080] Mix each repair agent with the soil evenly and transfer them to a flowerpot. Put 3 kg of soil in each pot and plant the clover seeds in the soil. After 10 days, keep 3 evenly growing seedlings in each pot. Water regularly to keep the soil water holding capacity at about 55%. Grow in a greenhouse at 25-30℃ for 25 days, collect soil samples and harvest the clover plants.

[0081] 2. Determination of soil pH and heavy metal content in Tripterygium wilfordii

[0082] 2.1 Soil pH was measured using the electrode method.

[0083] 2.2 Determination of heavy metal content in root tubers of Tripterygium wilfordii: Tripterygium wilfordii was harvested on day 25, the roots were cleaned of mud and sand, dried, cut into thin slices, dried at 60°C to constant weight, crushed and passed through a 0.15 mm nylon sieve to obtain sample powder. The content of lead and cadmium in root tubers of Tripterygium wilfordii was determined by microwave digestion and inductively coupled plasma emission spectrometry.

[0084] 3. Data processing

[0085] The data results are the mean ± standard deviation of 3 replicates. SPSS19.0 software was used for statistical analysis, Duncan method was used for difference significance analysis, and Graphpad Prism 7.0 software was used for plotting.

[0086] 4. Results

[0087] 4.1 Soil pH determination

[0088] Compared with CK without the application of the repair agent, the repair agent treatment in group A can increase the soil pH value. The effect of group A in increasing the soil pH value is significantly better than that of groups B, C, and D. Figure 3 shown.

[0089] 4.2 Determination of heavy metal content in root tubers of Tripterygium wilfordii

[0090] Compared with CK without the application of the repair agent, the repair agent in group A significantly reduced the cadmium content in the tubers of Tripterygium wilfordii. The effect of group A on reducing the cadmium content in the tubers of Tripterygium wilfordii was significantly better than that of groups B, C, and D. Figure 4 shown.

[0091] Compared with CK without the application of the repair agent, the repair agent in group A significantly reduced the lead content in the tubers of Tripterygium wilfordii. The effect of group A on reducing the lead content in the tubers of Tripterygium wilfordii was significantly better than that of groups B, C, and D. Figure 5 shown.

[0092] After treating soil contaminated with heavy metal cadmium, the soil remediation agent of the present invention can increase the pH value of the soil, significantly reduce the effectiveness of heavy metal cadmium and lead in the soil, and reduce the absorption and enrichment of cadmium and lead by crops. It is a low-cost, efficient, simple and environmentally friendly new bioremediation method.

[0093] It can be seen from the above results that after changing the components or the ratio of the components of the heavy metal contaminated soil remediation agent of the present invention, the remediation effect on the heavy metal contaminated soil will be significantly reduced. The components of the soil remediation agent of the present invention complement each other and achieve synergistic enhancement between the components.

[0094] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A heavy metal contaminated soil remediation agent, characterized in that: The heavy metal contaminated soil remediation agent mainly comprises the following components by weight: 20-30 parts of alkali-modified cotton straw biochar, 5-10 parts of sepiolite, 15-20 parts of humic acid and 5-10 parts of calcium silicate.

2. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The heavy metal contaminated soil remediation agent mainly comprises the following components by weight: 25 parts of alkali-modified cotton straw biochar, 8 parts of sepiolite, 10 parts of humic acid and 7 parts of calcium silicate.

3. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The preparation method of the heavy metal contaminated soil remediation agent is as follows: (1) preparation of alkali-modified cotton straw biochar: naturally air-dry the cotton straw, crush it and pass it through a 20-mesh sieve, and dry the sieved cotton straw in an oven at 60°C; mix the cotton straw with MgCl2, and stir it vigorously for 6 hours, filter it and dry it in an oven at 60°C for more than 10 hours to reach constant weight, then place it in a tubular furnace and heat it to 700°C at a heating rate of 10°C / min, and calcine it at high temperature for 1-1.5 hours under nitrogen conditions to obtain alkali-modified cotton straw biochar; (2) mix the biochar, sepiolite, humic acid and calcium silicate, grind them, and obtain the heavy metal contaminated soil remediation agent.

4. The heavy metal contaminated soil remediation agent according to claim 3, characterized in that: The concentration of MgCl2 in step (1) is 0.5 mol / L.

5. The heavy metal contaminated soil remediation agent according to claim 3, characterized in that: In the step (1), the mass volume ratio of cotton straw to MgCl2 is 1 g: (10 mL-20 mL).

6. The heavy metal contaminated soil remediation agent according to claim 3, characterized in that: In the step (1), the mass volume ratio of cotton straw to MgCl2 is 1 g: 15 mL.

7. The heavy metal contaminated soil remediation agent according to claim 3, characterized in that: In the step (1), high temperature calcination is carried out under nitrogen conditions for 1 hour.

8. Use of the heavy metal contaminated soil remediation agent according to claim 1 in in-situ remediation of heavy metal contaminated soil.

9. The use according to claim 8, characterized in that: The heavy metal pollution is mercury, arsenic, cadmium and / or lead pollution.

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