CN-122012114-A - Preparation method of heavy metal polluted farmland soil restoration agent and soil restoration method

CN122012114ACN 122012114 ACN122012114 ACN 122012114ACN-122012114-A

Abstract

The invention provides a preparation method of a heavy metal polluted farmland soil restoration agent and a soil restoration method, and relates to the technical field of soil restoration, wherein the soil restoration method comprises the steps of performing 5-20 times of freeze thawing treatment on a soil layer from the surface of a heavy metal polluted farmland to an area with the depth of 50cm underground before thawing in spring; and uniformly spreading the chitosan-magnetic composite biochar on the soil surface of the heavy metal polluted farmland 1 to 2 weeks before sowing the crops, carrying out permeable irrigation, uniformly applying the soil restoration agent on the soil layer from the surface of the heavy metal polluted farmland to the region with the depth of 15cm underground during sowing the crops, uniformly applying the chitosan-magnetic composite biochar on the soil layer from the region with the depth of 16cm underground to the region with the depth of 20cm underground in the heavy metal polluted farmland, and carrying out conventional field water and fertilizer management after earthing. By adopting the method, the high-efficiency and stable restoration of the heavy metal polluted farmland deep soil in the freeze-thawing cycle environment can be realized.

Inventors

QU JINGBO
ZHANG XINCHEN
ZHANG YAFEI
WANG XINYU
WU JIAYUN
SUN YONG

Assignees

东北农业大学

Dates

Publication Date: 20260512
Application Date: 20260414

Claims (10)

1. The preparation method of the heavy metal polluted farmland soil restoration agent is characterized by comprising the following steps of: S1, dissolving biochar, ferric chloride hexahydrate and ferrous sulfate heptahydrate in water to obtain a first mixed solution, adding alkali liquor into the first mixed solution to adjust the pH value to 10-11, carrying out a first stirring reaction, separating a magnetic precipitate, washing the magnetic precipitate to be neutral, and drying the magnetic precipitate to obtain magnetic biochar; s2, adding glutaraldehyde solution into the second mixed solution, performing a second stirring reaction, separating a magnetic product, washing to be neutral, and drying to obtain chitosan-magnetic composite biochar; And S3, uniformly mixing the compound bacterial liquid with a sodium alginate solution, adding the chitosan-magnetic compound biochar, uniformly stirring to obtain a third mixed liquid, adding the third mixed liquid into a calcium chloride solution, standing for solidification, collecting gel microspheres, washing and drying to obtain a soil restoration agent, wherein the compound bacterial liquid contains bacillus belicus and pseudomonas fluorescens.
2. The method for preparing a heavy metal contaminated farmland soil restoration agent according to claim 1, wherein in said step S1, the mass ratio of said biochar, said ferric chloride hexahydrate, and said ferrous sulfate heptahydrate is (1.8 to 2.2): 3.1 to 3.4): 1.5 to 1.7.
3. The method for preparing a heavy metal contaminated farmland soil restoration agent according to claim 1, wherein in the step S1, the mass ratio of the magnetic biochar to the chitosan is 5 (3.8 to 4.2).
4. The method for preparing a heavy metal contaminated farmland soil restoration agent according to claim 1, wherein the volume fraction of the glutaraldehyde solution is 1.8% to 2.2%, and the mass ratio of glutaraldehyde in the glutaraldehyde solution to the magnetic biochar is 1 (40 to 60).
5. The method for preparing a heavy metal contaminated farmland soil restoration agent according to claim 1, wherein in the step S3, the concentration of bacillus bailii in the composite bacterial liquid is (2.9 to 3.1) ×10 9 CFU/mL, the concentration of pseudomonas fluorescens is (1.9 to 2.1) ×10 9 CFU/mL, and the mass-volume ratio of the chitosan-magnetic composite biochar to the composite bacterial liquid is (4 to 6): 1.
6. The method for preparing a heavy metal contaminated farmland soil restoration agent according to claim 1, wherein in the step S3, the mass fraction of the sodium alginate solution is 3.5% to 4.5%, and the volume ratio of the composite bacterial liquid to the sodium alginate solution is (0.9 to 1.1): 0.9 to 1.1.
7. The method for preparing a heavy metal contaminated farmland soil restoration agent according to claim 1, wherein in the step S3, the mass fraction of the calcium chloride solution is 1.8% to 2.2%, and the ratio of the volume of the calcium chloride solution to the volume of the third mixed solution is (5 to 10): 1.
8. A method of soil remediation comprising: The method comprises the steps of M1, before the soil is thawed in spring, performing 5-20 times of freeze thawing treatment on a soil layer in a region from the surface of a heavy metal polluted farmland to the underground depth of 50cm, wherein the freeze thawing treatment comprises the steps of reducing the temperature of the soil layer to a freezing temperature, maintaining the temperature for 10-14 h, then reducing the temperature to a melting temperature, and maintaining the temperature for 10-14 h; step M2, uniformly broadcasting chitosan-magnetic composite biochar on the soil surface of the heavy metal polluted farmland according to a first application amount, and carrying out permeable irrigation, wherein the first application amount is 30 kg/mu to 50 kg/mu; Step M3, uniformly applying a soil restoration agent to a soil layer from the surface of the heavy metal polluted farmland to a region with the underground depth of 15cm according to a second application amount, uniformly applying chitosan-magnetic composite biochar to a soil layer from the underground depth of 16cm to a region with the underground depth of 20cm according to a third application amount, and performing conventional field water and fertilizer management after earthing, wherein the second application amount is 60 kg/mu to 80 kg/mu, and the third application amount is 30 kg/mu to 50 kg/mu; Wherein the chitosan-magnetic composite biochar and the soil restoration agent are prepared by the preparation method according to any one of claims 1 to 7.
9. The method of claim 8, wherein the crop is soybean.
10. The soil remediation method of claim 8 wherein in step M1, the freezing temperature is from-10 ℃ to-30 ℃ and the thawing temperature is from 10 ℃ to 25 ℃.

Description

Preparation method of heavy metal polluted farmland soil restoration agent and soil restoration method Technical Field The invention relates to the technical field of soil remediation, in particular to a preparation method of a heavy metal polluted farmland soil remediation agent and a soil remediation method. Background Restoration of heavy metal contaminated farmland soil in a freeze-thaw cycle environment is a key challenge in the field of environmental engineering. The unique physicochemical process initiated by freeze thawing cycle profoundly affects the long-term efficacy of soil restoration materials. The freeze thawing cycle changes the physicochemical properties of soil through the periodic freezing-thawing process, thereby obviously regulating and controlling the heavy metal behavior. Researches show that after 30 freeze thawing cycles, the content of weak acid extractable heavy metals in soil can be increased by 20 to 40 percent, and the bioavailability is obviously improved. Along with the freezing-thawing of the moisture, the activated heavy metals are easy to accelerate migration to deep soil. However, at present, heavy metal passivation materials are mostly applied to soil through conventional modes such as mechanical rotary tillage, and physical obstruction of lower undisturbed soil is difficult to break through, so that heavy metal passivation materials applied on a surface layer cannot effectively touch and fix heavy metals which have migrated to a deep layer, and a technical blind area for excessive repair of surface layer soil and heavy metal pollution of deep layer soil is formed. In addition, the traditional biochar is used as a heavy metal passivation material, and is faced with a remarkable bottleneck in a freeze-thawing cycle environment, and the biochar is easy to damage in structure, low in passivation capability and single in function, so that the soil restoration efficiency is seriously affected. Disclosure of Invention The invention solves at least one of the following problems (1) how to improve the deep soil restoration effect for restoring the heavy metal polluted farmland soil and (2) how to obtain the heavy metal passivation material with higher restoration efficiency. In order to solve the problems, the invention provides a preparation method of a heavy metal polluted farmland soil restoration agent, which comprises the following steps: S1, dissolving biochar, ferric chloride hexahydrate and ferrous sulfate heptahydrate in water to obtain a first mixed solution, adding alkali liquor into the first mixed solution to adjust the pH value to 10-11, carrying out a first stirring reaction, separating a magnetic precipitate, washing the magnetic precipitate to be neutral, and drying the magnetic precipitate to obtain magnetic biochar; s2, adding glutaraldehyde solution into the second mixed solution, performing a second stirring reaction, separating a magnetic product, washing to be neutral, and drying to obtain chitosan-magnetic composite biochar; And S3, uniformly mixing the compound bacterial liquid with a sodium alginate solution, adding the chitosan-magnetic compound biochar, uniformly stirring to obtain a third mixed liquid, adding the third mixed liquid into a calcium chloride solution, standing for solidification, collecting gel microspheres, washing and drying to obtain a soil restoration agent, wherein the compound bacterial liquid contains bacillus belicus and pseudomonas fluorescens. Compared with the prior art, the method has the advantages that the magnetic biochar is generated by loading the iron oxide on the surface of the biochar, the hydroxyl functional groups on the surface of the magnetic biochar are rich, heavy metal ions such as Cd 2+、Pb2+ and the like can be rapidly fixed through complexation and coprecipitation, and amino functional groups are further introduced to enhance the chelating ability after the chitosan is coated by glutaraldehyde crosslinking, so that the structural stability of the material in soil is improved, and the absorption of the biochar can be prevented from being attenuated with time. In addition, bacillus belicus and pseudomonas fluorescens in the composite bacterial liquid can not only change the heavy metal form by secreting organic acid and iron oxide to reduce the bioavailability, but also generate plant hormone to promote the growth of crops and promote stress resistance, and can also inhibit soil-borne pathogenic bacteria to improve the soil microecology. Finally, the sodium alginate-calcium chloride gel microsphere structure provides a protective barrier for the functional bacteria, reduces the risk of being stressed by the environment or predated by protozoa in the soil, realizes long-acting maintenance of microbial activity, and meanwhile, has the magnetic characteristic of being convenient for later-stage accurate positioning or recovery, and further optimizes the soil restoration efficiency and sustainability. The soil res