Lead-polluted soil remediation agent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of heavy metal pollution treatment, and relates to a lead-polluted soil remediation agent as well as a preparation method and application thereof. The lead-polluted soil remediation agent is mainly prepared from the following components in parts by weight: 15 to 25 parts of alkali modified corncob charcoal, 15 to 25 parts of chitosan, 10 to 20 parts of modified bentonite, 10 to 15 parts of calcium silicate, 8 to 12 parts of lime and 8 to 12 parts of diatomite. The components are combined for use, a remarkable synergistic interaction effect is achieved in the lead-polluted soil, the passivation rate of the lead-polluted soil reaches 85.9%, the activity of lead in the soil is reduced, and crop absorption is inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal pollution control and relates to a lead-contaminated soil remediation agent and a preparation method and application thereof. Background Art

[0002] Heavy metals are considered to be the main obstacle to the sustainable development of environmental health because they can destroy the ecosystem and harm human health. Heavy metals enter the soil through interception, redox reaction, methylation reaction, chemical and biological transformation, and are retained in the soil through adsorption, precipitation and complexation. Finally, they exist in the soil in a stable chemical state, seriously polluting the soil and destroying the ecological balance.

[0003] Lead pollution in the environment mainly comes from enterprises that smelt, manufacture and use lead products. The main ways for lead to enter the soil environment are dry and wet deposition of atmospheric lead pollutants, sewage irrigation with lead-containing wastewater, direct pollution of lead-containing solid waste and the use of pesticides. Soil contaminated by heavy metal lead not only affects the photosynthesis and respiration of plants, reducing plant biomass and quality, but also enters the human body through breathing, skin, drinking water and food, causing health diseases such as cancer, disease and mutation, and endangering human health.

[0004] How to effectively reduce the transmission of heavy metals in the food chain, control soil pollution and protect the ecological environment has become a research hotspot in soil heavy metal pollution remediation today, and it is also one of the problems that need to be solved urgently. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a lead-contaminated soil remediation agent and its preparation method and application, wherein the lead-contaminated soil remediation agent can effectively remove the effective lead content in the lead-contaminated soil and effectively improve the lead-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 lead-contaminated soil remediation agent, which mainly comprises the following components by weight: 15-25 parts of alkali-modified corn cob biochar, 15-25 parts of chitosan, 10-20 parts of modified bentonite, 10-15 parts of calcium silicate, 8-12 parts of lime and 8-12 parts of diatomaceous earth.

[0008] Preferably, the lead-contaminated soil remediation agent mainly comprises the following components by weight: 20 parts of alkali-modified corn cob biochar, 20 parts of chitosan, 15 parts of modified bentonite, 12 parts of calcium silicate, 10 parts of lime and 10 parts of diatomaceous earth.

[0009] In a second aspect, the present invention provides a method for preparing the above-mentioned lead-contaminated soil remediation agent, comprising the following steps:

[0010] (1) Preparation of alkali-modified corn cob biochar: The corn cob is naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 hours to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1-1.5 hours under nitrogen conditions to obtain corn cob biochar; the corn cob biochar is mixed with potassium hydroxide, stirred and placed in a shaker for 10-14 hours, dried at 105°C for 22-26 hours, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0011] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a water bath at 65-75°C for 4-6 hours, let stand for 12-14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.15-1.35mmoL, react in a water bath at 70-90°C and evaporate to dryness to obtain modified bentonite;

[0012] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0013] Preferably, the concentration of potassium hydroxide in step (1) is 3 mol / L.

[0014] Preferably, in step (1), the weight ratio of corn cob biochar to potassium hydroxide is 1:1-3.

[0015] More preferably, in step (1), the weight ratio of corncob biochar to potassium hydroxide is 1:2.

[0016] Preferably, in step (1), high temperature calcination is carried out under nitrogen conditions for 1.5 hours.

[0017] Preferably, in step (2), bentonite: Al 3+ =1g:1.25mmoL.

[0018] Preferably, the preparation method of the lead-contaminated soil remediation agent of the present invention comprises the following steps:

[0019] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen conditions to obtain corn cob biochar; the corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:2, stirred and placed in a shaker for 12 h, dried at 105°C for 24 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0020] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 70°C water bath for 5 hours, let stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.25mmoL, react in a water bath at 80°C and evaporate to dryness to obtain modified bentonite;

[0021] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0022] In a third aspect, the present invention provides the use of the lead-contaminated soil remediation agent obtained by the above preparation method in in-situ remediation of soil lead contamination.

[0023] Beneficial effects achieved by the present invention:

[0024] The soil remediation agent of the present invention can effectively reduce the bioavailability of lead in the soil, promote the conversion of lead in the soil into an inactive residue state, and the functional groups on the surface of biochar and heavy metal ions form a unique complex through surface complexation, which reduces the activity of lead in the soil, prevents crop absorption, and controls its migration through its adsorption. Modified bentonite has ion exchange properties, which can fix heavy metal ions in the soil, reduce the bioavailability of heavy metal ions, and thus reduce the absorption of heavy metal ions by plants. While adsorbing heavy metal ions, calcium silicate also has high chemical reaction activity and can react chemically with heavy metal ions to form stable adsorption products. Chitosan can combine with lead ions through surface complexation, ion exchange, etc. to form a stable complex. The addition of lime increases the pH value of the soil. The increase in the pH value of the soil increases the surface negative charge of variable charged colloids such as clay minerals, organic matter and iron-aluminum oxides, thereby increasing the specific adsorption ratio of heavy metal ions and reducing the activity of soluble heavy metal ions. Diatomaceous earth has a strong adsorption capacity for heavy metal ions and will not change the physical and chemical properties of the soil too much.

[0025] The present invention uses the above components in combination, and exhibits a significant synergistic effect in lead-contaminated soil, with a passivation rate of 85.9% for lead-contaminated soil, thereby reducing the activity of lead in the soil and inhibiting crop absorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 The passivation rate of the lead-contaminated soil remediation agent of the present invention on the total lead in the lead-contaminated soil

[0028] Compared with the control group, # P<0.05, ## P<0.01; compared with Example 1 group, & P<0.05, && P<0.01.

[0029] Figure 2 The passivation rate of the lead-contaminated soil remediation agent of the present invention on the effective lead in the lead-contaminated soil

[0030] Compared with the control group, # P<0.05, ## P<0.01; compared with Example 1 group, & P<0.05, && P<0.01.

[0031] Figure 3 Effect of the lead-contaminated soil remediation agent of the present invention on lead accumulation in cabbage leaves

[0032] Compared with the control group, # P<0.05, ## P<0.01; compared with Example 1 group, & P<0.05. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is briefly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example 1 Lead-contaminated soil remediation agent and preparation method thereof

[0035] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 20 parts of alkali-modified corn cob biochar, 20 parts of chitosan, 15 parts of modified bentonite, 12 parts of calcium silicate, 10 parts of lime and 10 parts of diatomaceous earth.

[0036] The preparation method is:

[0037] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen conditions to obtain corn cob biochar; the corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:2, stirred and placed in a shaker for 12 h, dried at 105°C for 24 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0038] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 70°C water bath for 5 hours, let stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.25mmoL, react in a water bath at 80°C and evaporate to dryness to obtain modified bentonite;

[0039] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0040] Example 2 Lead-contaminated soil remediation agent and preparation method thereof

[0041] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 15 parts of alkali-modified corn cob biochar, 25 parts of chitosan, 20 parts of modified bentonite, 10 parts of calcium silicate, 8 parts of lime and 12 parts of diatomaceous earth.

[0042] The preparation method is:

[0043] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1 h under nitrogen to obtain corn cob biochar; corn cob biochar and 3 mol / L potassium hydroxide were mixed at a weight ratio of 1:3, stirred and placed in a shaker for 10 h, dried at 105°C for 22 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0044] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 75°C water bath for 4 hours, let stand for 14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.30mmoL, react in a water bath at 85°C and evaporate to dryness to obtain modified bentonite;

[0045] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0046] Example 3 Lead-contaminated soil remediation agent and preparation method thereof

[0047] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 25 parts of alkali-modified corn cob biochar, 15 parts of chitosan, 10 parts of modified bentonite, 15 parts of calcium silicate, 12 parts of lime and 8 parts of diatomaceous earth.

[0048] The preparation method is:

[0049] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen conditions to obtain corn cob biochar; the corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:1, stirred and placed in a shaker for 14 h, dried at 105°C for 26 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0050] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 65°C water bath for 4 hours, let stand for 12 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.20mmoL, react in a water bath at 80°C and evaporate to dryness to obtain modified bentonite;

[0051] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0052] Example 4 Lead-contaminated soil remediation agent and preparation method thereof

[0053] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 15 parts of alkali-modified corn cob biochar, 20 parts of chitosan, 15 parts of modified bentonite, 10 parts of calcium silicate, 10 parts of lime and 8 parts of diatomaceous earth.

[0054] The preparation method is:

[0055] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen conditions to obtain corn cob biochar; the corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:2, stirred and placed in a shaker for 14 h, dried at 105°C for 22 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0056] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 70°C water bath for 6 hours, let stand for 14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.35mmoL, react in a 90°C water bath and evaporate to dryness to obtain modified bentonite;

[0057] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0058] Example 5 Lead-contaminated soil remediation agent and preparation method thereof

[0059] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 25 parts of alkali-modified corn cob biochar, 20 parts of chitosan, 20 parts of modified bentonite, 10 parts of calcium silicate, 12 parts of lime and 8 parts of diatomaceous earth.

[0060] The preparation method is:

[0061] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1 h under nitrogen to obtain corn cob biochar; corn cob biochar and 3 mol / L potassium hydroxide were mixed at a weight ratio of 1:3, stirred and placed in a shaker for 10 h, dried at 105°C for 22 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0062] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 75°C water bath for 6 hours, let stand for 12 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.15mmoL, react in a 70°C water bath and evaporate to dryness to obtain modified bentonite;

[0063] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0064] Comparative Example 1 Lead-contaminated soil remediation agent and preparation method thereof

[0065] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 20 parts of corn cob biochar, 20 parts of chitosan, 15 parts of modified bentonite, 12 parts of calcium silicate, 10 parts of lime and 10 parts of diatomaceous earth.

[0066] The preparation method is:

[0067] (1) Preparation of corn cob biochar: The corn cob was naturally air-dried, crushed and passed through a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen to obtain corn cob biochar;

[0068] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 70°C water bath for 5 hours, let stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.25mmoL, react in a water bath at 80°C and evaporate to dryness to obtain modified bentonite;

[0069] (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0070] Comparative Example 2 Lead-contaminated soil remediation agent and preparation method thereof

[0071] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 20 parts of alkali-modified corn cob biochar, 20 parts of chitosan, 15 parts of bentonite, 12 parts of calcium silicate, 10 parts of lime and 10 parts of diatomaceous earth.

[0072] The preparation method is:

[0073] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen conditions to obtain corn cob biochar; the corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:2, stirred and placed in a shaker for 12 h, dried at 105°C for 24 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0074] (2) The biochar, chitosan, bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0075] Comparative Example 3 Lead-contaminated soil remediation agent and preparation method thereof

[0076] A lead-contaminated soil remediation agent mainly comprises the following components by weight: 25 parts of alkali-modified corn cob biochar, 25 parts of chitosan, 20 parts of modified bentonite and 17 parts of diatomaceous earth.

[0077] The preparation method is:

[0078] (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen conditions to obtain corn cob biochar; the corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:2, stirred and placed in a shaker for 12 h, dried at 105°C for 24 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar;

[0079] (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 70°C water bath for 5 hours, let stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.25mmoL, react in a water bath at 80°C and evaporate to dryness to obtain modified bentonite;

[0080] (3) The biochar, chitosan, modified bentonite and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

[0081] Test Example 1: Restoration effect of the remediation agent of the present invention on lead-contaminated soil

[0082] The test soil was lead-contaminated soil from a chemical plant. The lead-contaminated soil was artificially prepared, and the total lead content in the soil sample was determined by graphite furnace atomic absorption spectrophotometry according to the "Determination of Lead and Cadmium in Soil Quality" (GB / T 17141-1997). The total lead content in the soil was 354.15 mg / kg.

[0083] A pot experiment was used to test the remediation effects of different remediation agents on lead-contaminated soil, and 6 treatments were set up: control group, Example 1 group, Example 3 group, Comparative Example 1 group, Comparative Example 2 group, and Comparative Example 3 group. Three replicates were set for each treatment.

[0084] The test soil sample without the repair agent was used as the control group. The Example 1 group, the Example 3 group, the Comparative Example 1 group, the Comparative Example 2 group, and the Comparative Example 3 group used 3% by weight of the repair agent of Example 1, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively. The soil moisture was maintained at about 60% water content, the flower pot was covered with plastic wrap, placed in a dark place, and kept away from light for 24 hours.

[0085] The repaired soil was collected and the passivation rate was determined. The remediation effect of lead pollution was analyzed based on the passivation rate.

[0086] Passivation rate = (total lead content in soil before remediation - total lead content in soil after remediation) / total lead content in soil before remediation.

[0087] like Figure 1 As shown, after restoration, compared with the control group without the restoration agent, the lead content in the soil was significantly reduced in Example 1 and Example 3 after the restoration agent treatment. The effect of Example 1 on reducing the lead content in the soil was significantly better than that of Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0088] Experimental Example 2 The remediation effect of the remediation agent of the present invention on lead-contaminated soil and its effect on lead accumulation in crops

[0089] The saline-alkali land contaminated by lead was selected, and the total lead content in the soil samples was determined by graphite furnace atomic absorption spectrophotometry according to the "Determination of Lead and Cadmium in Soil Quality" (GB / T17141-1997), and the determination of effective lead in soil was determined by atomic absorption spectrophotometer according to the "Determination of Effective Lead and Cadmium in Soil Quality" (GB / T 23739-2009). The total lead content in the soil was 253.18 mg / kg, and the effective lead was 110.36 mg / kg.

[0090] 18 identical plots were selected, and 450 kg of the lead pollution remediation agent prepared in Example 1, Example 2, and Comparative Examples 1-3 and 1500 kg of farmyard manure per mu were added respectively; the control group was added with 1500 kg of farmyard manure per mu and cabbage was planted for comparative experiments. Three replicates were set for each treatment.

[0091] The cabbages that had grown for 70 days were harvested and buried together, and the content of available lead in the soil and the content of lead in the cabbage leaves were tested after harvest.

[0092] like Figure 2 As shown, the residual effective lead content in the soil of the plot where only farmyard manure was added to plant cabbage was 109.80 mg / kg; the effective lead content in the soil of the plot where farmyard manure and the lead pollution remediation agent prepared in Example 1 were added to plant cabbage was 15.56 mg / kg, and the passivation rate of the lead pollution remediation agent in Example 1 on the lead-contaminated soil was 85.9%.

[0093] like Figure 3 As shown, compared with the control group without the repair agent, the repair agents of Example 1 and Example 2 significantly reduced the lead content in cabbage leaves. The effect of the repair agent of Example 1 on reducing the lead content in cabbage leaf tubers was significantly better than that of the control groups 1-3.

[0094] Comparative Example 1 did not modify the corncob biochar, and the remediation effect on the lead-contaminated soil was worse than that of Example 1. Comparative Example 2 did not modify the bentonite, and the remediation effect on the lead-contaminated soil was worse than that of Example 1. Comparative Example 3 did not add lime and calcium silicate, and the remediation effect on the lead-contaminated soil was worse than that of Example 1.

[0095] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, transformation and modification made to the above embodiment based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A lead-contaminated soil remediation agent, characterized in that: The lead-contaminated soil remediation agent mainly comprises the following components by weight: 15-25 parts of alkali-modified corn cob biochar, 15-25 parts of chitosan, 10-20 parts of modified bentonite, 10-15 parts of calcium silicate, 8-12 parts of lime and 8-12 parts of diatomaceous earth.

2. The lead-contaminated soil remediation agent according to claim 1, characterized in that: The lead-contaminated soil remediation agent mainly includes the following components by weight: 20 parts of alkali-modified corn cob biochar, 20 parts of chitosan, 15 parts of modified bentonite, 12 parts of calcium silicate, 10 parts of lime and 10 parts of diatomaceous earth.

3. The lead-contaminated soil remediation agent according to claim 1, characterized in that: The preparation method of the lead-contaminated soil remediation agent is as follows: (1) Preparation of alkali-modified corn cob biochar: The corn cob is naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 hours to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1-1.5 hours under nitrogen conditions to obtain corn cob biochar; the corn cob biochar is mixed with potassium hydroxide, stirred and placed in a shaker for 10-14 hours, dried at 105°C for 22-26 hours, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar; (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a water bath at 65-75°C for 4-6 hours, let stand for 12-14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.15-1.35mmoL, react in a water bath at 70-90°C and evaporate to dryness to obtain modified bentonite; (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

4. The lead-contaminated soil remediation agent according to claim 3, characterized in that: The concentration of potassium hydroxide in step (1) is 3 mol / L.

5. The lead-contaminated soil remediation agent according to claim 3, characterized in that: In the step (1), the weight ratio of corncob biochar to potassium hydroxide is 1:1-3.

6. The lead-contaminated soil remediation agent according to claim 5, characterized in that: In the step (1), the weight ratio of corncob biochar to potassium hydroxide is 1:

2.

7. The lead-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 1.5 hours.

8. The lead-contaminated soil remediation agent according to claim 3, characterized in that: In the step (2), bentonite: Al 3 + =1g:1.25mmoL.

9. The lead-contaminated soil remediation agent according to claim 3, characterized in that: The preparation method of the lead-contaminated soil remediation agent is as follows: (1) Preparation of alkali-modified corn cob biochar: The corn cob was naturally air-dried, crushed and sieved with a 20-mesh sieve, dried in an oven at 60°C for more than 10 h to reach constant weight, and then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min, and calcined at high temperature for 1.5 h under nitrogen conditions to obtain corn cob biochar; the corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:2, stirred and placed in a shaker for 12 h, dried at 105°C for 24 h, cooled naturally, ground and sieved with a 100-mesh sieve to obtain alkali-modified corn cob biochar; (2) Preparation of modified bentonite: Weigh sodium hydroxide and polyaluminium chloride to prepare solutions, adjust the pH value of the polyaluminium chloride solution with sodium hydroxide solution, and then react in a 70°C water bath for 5 hours, let stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent to the bentonite and stir well to control the bentonite: Al 3+ =1g:1.25mmoL, react in a water bath at 80°C and evaporate to dryness to obtain modified bentonite; (3) The biochar, chitosan, modified bentonite, calcium silicate, lime and diatomaceous earth are mixed and ground to obtain a lead-contaminated soil remediation agent.

10. Use of the lead-contaminated soil remediation agent according to claim 1 in in-situ remediation of lead-contaminated soil.

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