A lead-contaminated soil remediation agent and its preparation method and application

Abstract

The present invention belongs to the field of heavy metal pollution control technology and relates to a lead-contaminated soil remediation agent, its preparation method, and application. The lead-contaminated soil remediation agent of the present invention mainly comprises the following components, by weight: 15-25 parts of alkali-modified corncob 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. The present invention combines these components to exhibit a significant synergistic effect in lead-contaminated soil, achieving a passivation rate of 85.9% in lead-contaminated soil, reducing the activity of lead in the soil and inhibiting crop absorption.

Description

Technical Field

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

[0002] Heavy metals are considered a major obstacle to sustainable environmental health due to their potential to disrupt ecosystems and harm human health. Heavy metals enter soil through processes such as interception, redox reactions, methylation, and chemical and biological transformations. They are then retained in the soil through adsorption, precipitation, and complexation, ultimately remaining in the soil in a stable chemical state, severely contaminating the soil and disrupting ecological balance.

[0003] Lead pollution in the environment primarily originates from enterprises that smelt, manufacture, and use lead products. Lead enters the soil environment primarily through wet and dry deposition of atmospheric lead pollutants, lead-containing wastewater irrigation, direct contamination from lead-containing solid waste, and pesticide use. Heavy metal lead contamination of soil not only affects plant photosynthesis and respiration, reducing plant biomass and quality, but also enters the human body through respiratory, skin, drinking water, and food, causing health problems such as cancer, disease, and mutations, posing a threat to 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, which can effectively remove the effective lead content in 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 in parts 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 was air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 hours to reach constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1-1.5 hours under nitrogen to obtain corn cob biochar; the corn cob biochar was mixed with potassium hydroxide, stirred, and placed in a shaker for 10-14 hours. It was dried at 105°C for 22-26 hours, cooled naturally, ground, and passed through 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℃ for 4-6 hours, let it stand for 12-14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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, the weight ratio of corn cob biochar to potassium hydroxide in step (1) is 1:2.

[0016] Preferably, in step (1), the 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to a constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1.5 h under nitrogen 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. It was dried at 105°C for 24 h, cooled naturally, ground, and passed through 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 it stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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-mentioned preparation method in in-situ remediation of lead-contaminated soil.

[0023] The beneficial effects achieved by the present invention are:

[0024] The soil remediation agent of the present invention effectively reduces the bioavailability of lead in soil and promotes its conversion to an inactive residual state. The functional groups on the biochar surface form unique complexes with heavy metal ions through surface complexation, reducing the activity of lead in soil, preventing crop absorption, and controlling its migration through adsorption. Modified bentonite has ion exchange properties, which can immobilize heavy metal ions in the soil, reducing their bioavailability and thus reducing their uptake by plants. Calcium silicate, while adsorbing heavy metal ions, also has high chemical reactivity, reacting with them to form stable adsorbed products. Chitosan can bind to lead ions through surface complexation and ion exchange to form stable complexes. The addition of lime increases soil pH, which increases the negative surface charge of variably charged colloids such as clay minerals, organic matter, and iron and aluminum oxides, thereby increasing the proportion of specific adsorption for heavy metal ions and reducing the activity of soluble heavy metal ions. Diatomaceous earth has a strong adsorption capacity for heavy metal ions and does not significantly alter the physical and chemical properties of the soil.

[0025] The present invention uses the above components in combination, showing a significant synergistic effect in lead-contaminated soil, with a passivation rate of 85.9% on lead-contaminated soil, 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 any 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 the 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 the 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 the Example 1 group, & P<0.05. DETAILED DESCRIPTION

[0033] The following is a brief description of the specific embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are also 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to a constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1.5 h under nitrogen 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. It was dried at 105°C for 24 h, cooled naturally, ground, and passed through 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 it stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to reach constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1 h under nitrogen to obtain corn cob biochar. The corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:3, stirred, and placed in a shaker for 10 h. It was dried at 105°C for 22 h, cooled naturally, ground, and passed through 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 it stand for 14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to reach constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1.5 h under nitrogen 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. It was dried at 105°C for 26 h, cooled naturally, ground, and passed through 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 it stand for 12 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to a constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1.5 h under nitrogen 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. It was dried at 105°C for 22 h, cooled naturally, ground, and passed through 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 it stand for 14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to reach constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1 h under nitrogen to obtain corn cob biochar. The corn cob biochar was mixed with 3 mol / L potassium hydroxide at a weight ratio of 1:3, stirred, and placed in a shaker for 10 h. It was dried at 105°C for 22 h, cooled naturally, ground, and passed through 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 it stand for 12 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. The corn cob was dried in an oven at 60°C for more than 10 h to a constant weight. The corn cob was then heated in a tube furnace at a heating rate of 20°C / min to 650°C. The corn cob biochar was calcined at high temperature for 1.5 h under nitrogen.

[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 it stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to a constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1.5 h under nitrogen 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. It was dried at 105°C for 24 h, cooled naturally, ground, and passed through a 100-mesh sieve to obtain alkali-modified corn cob biochar.

[0074] (2) 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 in parts 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to a constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1.5 h under nitrogen 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. It was dried at 105°C for 24 h, cooled naturally, ground, and passed through 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 it stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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. The total lead content in the soil sample was determined by graphite furnace atomic absorption spectrophotometry according to the "Soil Quality - Determination of Lead and Cadmium" (GB / T 17141-1997). The total lead content in the soil was 354.15 mg / kg.

[0083] A pot experiment was conducted to test the remediation effects of different remediation agents on lead-contaminated soil. Six 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 up 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 mass 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 a water content of about 60%. The flower pots were 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 measured, and 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 repair, compared with the control group without the application of the repair agent, the lead content in the soil of Example 1 and Example 3 was significantly reduced after treatment with the repair agent. 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] Soil samples from lead-contaminated saline-alkali land were determined using graphite furnace atomic absorption spectrophotometry according to the "Soil Quality - Determination of Lead and Cadmium" (GB / T 17141-1997). Available lead in the soil was determined using an atomic absorption spectrophotometer according to the "Soil Quality - Determination of Available Lead and Cadmium" (GB / T 23739-2009). The total lead content in the soil was 253.18 mg / kg, and the available lead content was 110.36 mg / kg.

[0090] Eighteen identical plots were selected and treated with 450 kg of the lead contamination remediation agent prepared in Example 1, Example 2, and Comparative Examples 1-3, along with 1500 kg of farmyard manure per mu. A control group was treated with 1500 kg of farmyard manure per mu and planted with cabbage for a comparative experiment. Three replicates were set up for each treatment.

[0091] The cabbages were harvested after 70 days of growth and then buried together. The available lead content in the soil and the lead content 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 application of the repair agent, the repair agents of Examples 1 and 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 lead-contaminated soil was worse than that of Example 1. Comparative Example 2 did not modify the bentonite, and the remediation effect on 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 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 of 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; The preparation method of the alkali-modified corn cob biochar comprises the following steps: naturally air-drying the corn cob, crushing the corn cob, passing it through a 20-mesh sieve, drying it in an oven at 60° C. for more than 10 hours to reach a constant weight, heating it to 650° C. at a heating rate of 20° C. / min in a tube furnace, and calcining it at high temperature for 1-1.5 hours under nitrogen to obtain the corn cob biochar; mixing the corn cob biochar with potassium hydroxide, stirring the mixture, shaking it in a shaker for 10-14 hours, drying it at 105° C. for 22-26 hours, cooling it naturally, grinding it, and passing it through a 100-mesh sieve to obtain the alkali-modified corn cob biochar; The preparation method of the modified bentonite is as follows: weighing sodium hydroxide and polyaluminium chloride to prepare solutions respectively, adjusting the pH value of the polyaluminium chloride solution with sodium hydroxide solution, reacting in a water bath at 65-75°C for 4-6 hours, standing for 12-14 hours, and obtaining a pillaring agent for use; slowly adding the prepared pillaring agent to the bentonite and stirring evenly, controlling the bentonite:Al 3+ =1g:1.15-1.35mmoL, react in a 70-90℃ water bath and evaporate to dryness to obtain modified bentonite.

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 was air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 hours to reach constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1-1.5 hours under nitrogen to obtain corn cob biochar; the corn cob biochar was mixed with potassium hydroxide, stirred, and placed in a shaker for 10-14 hours. It was dried at 105°C for 22-26 hours, cooled naturally, ground, and passed through 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℃ for 4-6 hours, let it stand for 12-14 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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 the 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 corn cob 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 corn cob 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), the product is calcined at high temperature under nitrogen conditions for 1.5 hours.

8. The lead-contaminated soil remediation agent according to claim 3, characterized in that: Bentonite in step (2): 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 air-dried, crushed, and passed through a 20-mesh sieve. It was dried in an oven at 60°C for more than 10 h to a constant weight. It was then placed in a tube furnace and heated to 650°C at a heating rate of 20°C / min. It was calcined at high temperature for 1.5 h under nitrogen 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. It was dried at 105°C for 24 h, cooled naturally, ground, and passed through 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 it stand for 13 hours, and obtain the columnar agent for use; slowly add the prepared columnar agent into the bentonite and stir evenly 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) 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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