Preparation of cadmium passivator for weak alkaline soil and method for passivating lead in soil

Abstract

The application belongs to the technical field of heavy metal pollution treatment, and relates to a preparation of a weak alkaline soil cadmium passivator and a method for passivating soil lead. The weak alkaline soil cadmium passivator mainly comprises the following components in parts by weight: graphene oxide modified biochar 20-30 parts, montmorillonite 5-10 parts, bentonite 5-10 parts and microbial inoculum 5-10 parts, wherein the microbial inoculum is a composite inoculum composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens. The weak alkaline soil cadmium passivator has a good repairing effect on cadmium and lead in contaminated soil, can significantly improve the physicochemical properties of cadmium and / or lead contaminated soil, increase the soil organic matter content, reduce the migration in the environment, reduce the cadmium content in crops, and has great market promotion value.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal pollution control technology, and relates to the preparation of a weakly alkaline soil cadmium passivating agent and a method for passivating soil lead. Background Technology

[0002] Lead and cadmium in soil can be found in a variety of ways, such as atmospheric deposition, industrial wastewater and domestic sewage discharge, industrial solid waste and urban garbage dumping, and the application of chemical pesticides.

[0003] Lead and cadmium are characterized by their insidious nature, bioaccumulation, irreversibility, and difficulty in remediation in soil. They can affect crops, air and water quality, eventually appearing in the food chain and accumulating in the human body, leading to physiological dysfunction and even diseases such as lung cancer and renal insufficiency.

[0004] Unlike organic pollution, the core issue with heavy metal pollution is its non-degradability. Only by removing heavy metals from the soil or altering their valence and form within the soil, thereby reducing their migration and bioavailability in the environment, can the remediation of heavy metal-contaminated soil be achieved.

[0005] Alkaline soils include slightly alkaline soils (pH generally 7.1-8.5) and strongly alkaline soils (pH generally 8.5-9.5). Alkaline soils have a higher pH and lower organic matter content. In northern China, farmland is mainly dryland, and the soil is in an oxidized state most of the time, making it difficult to reduce the available heavy metal content in the soil by increasing soil pH or continuous flooding. Further application of high-pH soil conditioners or passivating agents to moderately alkaline soils carries risks such as soil compaction and reduced fertility. Currently, there are few passivating agents suitable for cadmium-contaminated alkaline soils, necessitating the development of cadmium passivating agents with significant passivation effects on slightly alkaline soils. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for preparing a weakly alkaline soil cadmium passivating agent and passivating soil lead. The weakly alkaline soil cadmium passivating agent has a significant passivation effect on cadmium-contaminated soil, effectively removes cadmium and lead from weakly alkaline soil, and improves the soil environment contaminated with heavy metals.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] In a first aspect, the present invention provides a weakly alkaline soil cadmium passivating agent, which mainly comprises the following components by weight: 20-30 parts of graphene oxide modified biochar, 5-10 parts of montmorillonite, 5-10 parts of bentonite, and 5-10 parts of microbial inoculant, wherein the microbial inoculant is a compound inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoides.

[0009] Furthermore, the weakly alkaline soil cadmium passivating agent mainly comprises the following components by weight: 25 parts of graphene oxide modified biochar, 8 parts of montmorillonite, 10 parts of bentonite, and 7 parts of microbial inoculant.

[0010] Furthermore, the montmorillonite is sodium-based montmorillonite and / or calcium-based montmorillonite.

[0011] Furthermore, the microbial mass ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids in the microbial agent is 2-4∶4-6∶1-3∶0.5-1, and the effective viable count of each of the Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids in the agent is ≥1.0×10⁻⁶. 9 cfu·g -1 The effective viable count of the compound microbial agent is ≥5.0×10⁻⁶. 9 cfu·g -1 .

[0012] Furthermore, the microbial mass ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids is 3:5:2:1.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned weakly alkaline soil cadmium passivating agent, wherein the preparation method is as follows:

[0014] (1) Preparation of graphene oxide modified biochar: peanut shells were dried at 60-65℃ for 10h, pulverized and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed and pyrolyzed at 500-550℃ for 2-3h under nitrogen protection to obtain mixed biochar. The mixture was cooled, dried, ground and passed through a 100-mesh sieve to obtain graphene oxide modified biochar.

[0015] (2) Mix the microbial agents evenly, separate the bacterial cells by centrifugation and precipitation, add galactose protectant, and freeze dry under vacuum to obtain composite microbial powder;

[0016] (3) Mix biochar, montmorillonite, bentonite and compound microbial powder, grind them to obtain a weakly alkaline soil cadmium passivating agent.

[0017] Furthermore, in step (1), the mass ratio of peanut shell powder to graphene oxide is 100-120:3.

[0018] Furthermore, in step (1), the mass ratio of peanut shell powder to graphene oxide is 110:3.

[0019] Furthermore, in step (2), the mass ratio of microbial cell precipitate to galactose is 1-3:1.

[0020] Furthermore, in step (2), the mass ratio of microbial cell precipitate to galactose is 2:1.

[0021] Thirdly, this invention provides the application of the weakly alkaline soil cadmium passivating agent obtained by the above preparation method in in-situ remediation of soil heavy metal pollution.

[0022] Fourthly, the present invention provides a method for using the above-mentioned weakly alkaline soil cadmium passivating agent, wherein the method comprises: applying the composite heavy metal passivating agent to heavy metal contaminated soil and tilling it.

[0023] Furthermore, when the application environment is potted plants, the application amount of the weakly alkaline soil cadmium passivating agent is 1%-4% of the weight of the potted soil; when the application environment is open field, the application amount of the weakly alkaline soil cadmium passivating agent is 150-200 kg / mu.

[0024] Preferably, the heavy metal pollution is cadmium and / or lead pollution.

[0025] The beneficial effects achieved by this invention are as follows:

[0026] (1) In the weakly alkaline soil cadmium passivating agent of this invention, biochar can adsorb heavy metal ions in the soil, thereby reducing the content of available heavy metals. At the same time, it can also increase the content of soil organic matter, enhance the activity of soil microorganisms, improve the physical and chemical properties of the soil, promote crop growth, and reduce the toxic effects of heavy metals on crops. The type of biochar, pyrolysis conditions, and amount added will all affect the performance of biochar. Montmorillonite is mainly composed of silicon dioxide and alumina, which does not pose a pollution risk to the soil and provides binding sites for cadmium and lead. Bentonite is composed of silicon dioxide and alumina, which undergoes ion exchange reaction with cadmium and lead ions in the soil. It has a large specific surface area and good adsorption performance for heavy metals. Microbial agents can quickly decompose organic matter to improve soil fertility. At the same time, the substances secreted by microorganisms form more stable aggregates with modified biochar, fixing or changing the form of heavy metals, thereby reducing the bioavailability of heavy metals in the soil, reducing the toxicity of heavy metals to crops, and enhancing the passivation effect.

[0027] (2) The weakly alkaline cadmium passivating agent of this invention is composed of the above-mentioned raw materials. Each raw material works synergistically to passivate cadmium and lead in the soil, significantly improving the physicochemical properties of soil contaminated with cadmium and / or lead, increasing soil organic matter content, reducing their migration in the environment, and decreasing cadmium content in crops. Adding any single substance alone cannot achieve the remediation effect of this invention. The proportions of the raw materials in this invention are not arbitrarily added; the amount of each substance has a crucial impact on the passivation effect of cadmium and lead.

[0028] (3) The weakly alkaline soil cadmium passivating agent of the present invention has a good remediation effect on cadmium and lead in polluted soil. It can significantly improve the physical and chemical properties of soil polluted by cadmium and / or lead, increase the soil organic matter content, reduce its migration in the environment, and reduce the cadmium content in crops. It has great market promotion value. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the specific embodiments will be briefly described below.

[0030] Figure 1 To investigate the effect of the passivating agent of this invention on the content of available cadmium in soil, a comparison was made with the control group. * P < 0.05 ** P < 0.01; compared with group A, # P < 0.05 ## P < 0.01.

[0031] Figure 2 To illustrate the effect of the passivating agent of this invention on the content of available lead in soil, a comparison was made with the control group. * P < 0.05 ** P < 0.01; compared with group A, # P < 0.05 ## P < 0.01.

[0032] Figure 3 To illustrate the effect of the passivating agent of this invention on soil organic matter content, a comparison was made with the control group. * P < 0.05 ** P < 0.01; compared with group A, # P < 0.05.

[0033] Figure 4 To investigate the effect of the passivating agent of this invention on the cadmium content of Chinese cabbage, a comparison was made with the control group. * P < 0.05 ** P < 0.01; compared with group A, # P < 0.05 ## P < 0.01. Detailed Implementation

[0034] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional biochemical reagents; and unless otherwise specified, the experimental methods are all conventional methods.

[0036] Example 1: Weakly alkaline soil cadmium passivating agent and its preparation method

[0037] Peanut shells were dried at 65℃ for 10 hours, pulverized, and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed at a mass ratio of 110:3 and pyrolyzed at 500℃ for 2.5 hours under nitrogen protection to obtain mixed biochar. The mixed biochar was cooled, dried, ground, and passed through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculum composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreutonicus at a mass ratio of 3:5:2:1 was mixed evenly. After centrifugation and sedimentation of the microbial cells, a galactose protectant was added. The mass ratio of microbial cell precipitate to galactose was 2:1. The mixture was then freeze-dried under vacuum to obtain composite microbial powder. Biochar, sodium montmorillonite, bentonite, and composite microbial powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0038] Example 2: Weakly alkaline soil cadmium passivating agent and its preparation method

[0039] Peanut shells were dried at 60℃ for 10 hours, pulverized, and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed at a mass ratio of 100:3 and pyrolyzed at 550℃ for 2 hours under nitrogen protection to obtain mixed biochar. The biochar was cooled, dried, ground, and passed through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculum composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreutonicus at a mass ratio of 2:4:1:1 was mixed evenly. After centrifugation and sedimentation of the microbial cells, a galactose protectant was added. The mass ratio of microbial cell precipitate to galactose was 3:1. The mixture was then freeze-dried under vacuum to obtain composite microbial powder. Biochar, calcium-based montmorillonite, bentonite, and composite microbial powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0040] Example 3: Weakly alkaline soil cadmium passivating agent and its preparation method

[0041] Peanut shells were dried at 65℃ for 10 hours, pulverized, and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed at a mass ratio of 120:3 and pyrolyzed at 500℃ for 3 hours under nitrogen protection to obtain mixed biochar. The mixed biochar was cooled, dried, ground, and passed through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculum composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids at a mass ratio of 4:6:3:0.5 was mixed evenly. After centrifugation and separation of the bacterial cells, a galactose protectant was added. The mass ratio of microbial cell precipitate to galactose was 1:1. The mixture was then freeze-dried under vacuum to obtain composite microbial powder. Biochar, calcium-based montmorillonite, bentonite, and composite microbial powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0042] Example 4: Weakly alkaline soil cadmium passivating agent and its preparation method

[0043] Peanut shells were dried at 60℃ for 10 hours, pulverized, and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed at a mass ratio of 110:3 and pyrolyzed at 550℃ for 2 hours under nitrogen protection to obtain mixed biochar. The mixed biochar was cooled, dried, ground, and passed through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculum composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids at a mass ratio of 4:4:3:0.5 was mixed evenly. After centrifugation and separation of the bacterial cells, a galactose protectant was added. The mass ratio of microbial cell precipitate to galactose was 1:1. The mixture was then freeze-dried under vacuum to obtain composite microbial powder. Biochar, sodium montmorillonite, bentonite, and composite microbial powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0044] Example 5: Weakly alkaline soil cadmium passivating agent and its preparation method

[0045] Peanut shells were dried at 65℃ for 10 hours, pulverized, and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed at a mass ratio of 120:3 and pyrolyzed at 550℃ for 3 hours under nitrogen protection to obtain mixed biochar. The mixed biochar was cooled, dried, ground, and passed through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids at a mass ratio of 4:4:1:1 was mixed evenly. After centrifugation and sedimentation of the microbial cells, a galactose protectant was added. The mass ratio of microbial cell precipitate to galactose was 3:1. The mixture was then freeze-dried under vacuum to obtain composite microbial powder. Biochar, sodium montmorillonite, bentonite, and composite microbial powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0046] Comparative Example 1: Cadmium passivating agent for weakly alkaline soil and its preparation method

[0047] The difference from Example 1 is that no biochar modification is performed.

[0048] Peanut shells were dried at 65℃ for 10 hours, pulverized and passed through a 100-mesh sieve to obtain peanut shell powder. The powder was then pyrolyzed at 500℃ for 2.5 hours under nitrogen protection, cooled, dried, ground, and passed through a 100-mesh sieve to obtain biochar. A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids in a mass ratio of 3:5:2:1 was mixed evenly. After centrifugation and sedimentation of the microbial cells, a galactose preservative was added, with the mass ratio of microbial cell precipitate to galactose being 2:1. The mixture was then freeze-dried under vacuum to obtain a composite microbial powder. Finally, biochar, sodium montmorillonite, bentonite, and the composite microbial powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0049] Comparative Example 2: Cadmium passivating agent for weakly alkaline soil and its preparation method

[0050] The difference from Example 1 is that the composite microorganisms are not protected with galactose.

[0051] Peanut shells were dried at 65℃ for 10 hours, pulverized and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed at a mass ratio of 110:3 and pyrolyzed at 500℃ for 2.5 hours under nitrogen protection to obtain mixed biochar. The mixed biochar was cooled, dried, ground, and passed through a 100-mesh sieve to obtain graphene oxide modified biochar. A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreutonicus at a mass ratio of 3:5:2:1 was mixed evenly to obtain a composite microbial inoculant powder. Biochar, sodium montmorillonite, bentonite, and the composite microbial inoculant powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0052] Comparative Example 3: Cadmium passivating agent for weakly alkaline soil and its preparation method

[0053] Compared with Example 1, the difference lies in changing the type and proportion of microbial inoculants.

[0054] Peanut shells were dried at 65℃ for 10 hours, pulverized, and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed at a mass ratio of 110:3 and pyrolyzed at 500℃ for 2.5 hours under nitrogen protection to obtain mixed biochar. The mixed biochar was cooled, dried, ground, and passed through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus thuringiensis at a mass ratio of 4:5:2 was mixed evenly. After centrifugation and sedimentation of the microbial cells, a galactose protectant was added. The mass ratio of microbial cell precipitate to galactose was 2:1. The mixture was then freeze-dried under vacuum to obtain composite microbial powder. Biochar, sodium montmorillonite, bentonite, and composite microbial powder were mixed and ground to obtain a weakly alkaline soil cadmium passivating agent.

[0055] Test Example 1: The effect of the weakly alkaline soil cadmium passivating agent of the present invention on cadmium and lead pollution.

[0056] 1. Experimental Methods

[0057] The test soil was farmland soil contaminated with cadmium and lead, with a soil pH of 7.25. The total cadmium and total lead contents in the soil samples were determined by graphite furnace atomic absorption spectrophotometry according to the standard "Determination of Lead and Cadmium in Soil Quality" (GB / T 17141-1997). The available cadmium and available lead contents were determined by atomic absorption spectrophotometry according to the standard "Determination of Available Lead and Cadmium in Soil Quality" (GB / T 23739-2009). The total cadmium content was 4.72 mg / kg, and the available cadmium content was 1.65 mg / kg; the total lead content was 153.83 mg / kg, and the available lead content was 78.47 mg / kg.

[0058] The study employed an indoor soil culture method, setting up seven treatments: control group (CK group), Example 1 group (A group), Example 2 group (B group), Comparative Example 1 group (C group), Comparative Example 2 group (D group), Comparative Example 3 group (E group), and Comparative Example 4 group (F group). Each treatment was replicated in triplicate, and passivation was performed for 21 days.

[0059] Using soil samples without passivating agents as the control group, the AF group was treated with passivating agents prepared in Examples 1, 2, 1, 2, 3, and 4 at a mass fraction of 3%. The culture dishes were covered with plastic wrap and placed in the dark for incubation. Throughout the incubation period, the soil moisture for each treatment was maintained at 65% of field capacity, with water added every 2-3 days. Simultaneously, the incubation temperature was kept constant at 20-25℃. After incubation, soil samples were collected, air-dried, pulverized, and passed through a 20-mesh sieve.

[0060] 2. Determination of available cadmium and lead content in soil

[0061] Weigh 5g of passivated soil sample (21 days) into a 100mL Erlenmeyer flask, add 25mL of diethylenetriaminepentaacetic acid (DTA) extractant, seal with plastic wrap and rubber band, and place on a horizontal reciprocating shaker. Shake for 3 hours at 23-27℃ and 160-200 rpm. After extraction, allow to stand and filter, discarding 2-3mL of the initial filtrate. Determine the available cadmium and lead content in the remaining filtrate using an atomic emission spectrophotometer with acetylene as the carrier gas flame.

[0062] 3. Data Processing

[0063] Data processing was performed using Graphpad Prism 7.0 software, and the measurement data was presented in the following format: This indicates that one-way ANOVA was used for comparisons among multiple groups, and pairwise comparisons between groups were performed using SNK-q, with P < 0.05 considered statistically significant.

[0064] 4. Results of determination of available cadmium and lead content in soil

[0065] like Figure 1 , 2 As shown, after 21 days of passivation treatment, compared with the control group (CK) without passivation agent, groups A and B significantly reduced the content of available cadmium and lead in the soil. Group A showed the most significant reduction in available cadmium and lead content, with passivation efficiencies of 74.3% and 77.5%, respectively. Group B also showed a significant reduction in available cadmium and lead content, with passivation efficiencies of 67.4% and 76.2%, respectively. The effects of groups A and B in reducing the content of available cadmium and lead in the soil were significantly better than those of groups C, D, E, and F.

[0066] Test Example 2: Remediation effect of the weakly alkaline cadmium passivating agent of the present invention on cadmium-contaminated soil

[0067] 1. Experimental Methods

[0068] The soil samples were collected from farmland, air-dried naturally, impurities were removed, and the soil was sieved through a 20-mesh sieve. The soil pH was 7.53, the organic matter content was 14.65 g / kg, and the available cadmium content was 0.07 mg / kg.

[0069] Add the appropriate concentration of Cd(NO3)2 to the above soil, stir well, air dry in the dark for 2 weeks, grind, and pass through a 20-mesh sieve to prepare Cd. 2+ Soil contaminated with cadmium at a concentration of 15 mg / kg.

[0070] An indoor soil culture method was used, with six treatments: 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), and Comparative Example 4 group (E group). Each treatment had three replicates, for a total of 18 pots. The test soil sample without passivating agent served as the control group, while the A and B groups were treated with passivating agents prepared in Examples 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 at a mass fraction of 3%.

[0071] After thoroughly mixing the passivating agents with the soil, transfer the mixture to flowerpots, filling each pot with 2 kg of soil. Plant the bok choy seeds in cadmium-contaminated simulated soil. When the bok choy grows to 10 cm, retain 3 evenly growing seedlings per pot, water regularly to maintain a soil moisture content of 65%, and grow in a greenhouse at 25-30℃ for 30 days. Collect soil samples and harvest the bok choy plants.

[0072] 2. Determination of soil organic matter content and cadmium content in Chinese cabbage.

[0073] 2.1 Soil organic matter content was determined using the potassium dichromate-sulfuric acid solution oxidation method.

[0074] 2.2 Determination of Cadmium Content in Chinese Cabbage: Chinese cabbage was harvested at 30 days old. It was first rinsed with distilled water, then soaked in 20 mmol / L Na2EDTA for 15-20 minutes to remove Cd from the root surface. 2+ Finally, rinse thoroughly with distilled water. The Cd in the leaves... 2+ The content was determined by microwave digestion and inductively coupled plasma atomic emission spectrometry.

[0075] 3. Data Processing

[0076] Data processing was performed using Graphpad Prism 7.0 software, and the measurement data was presented in the following format: This indicates that one-way ANOVA was used for comparisons among multiple groups, and pairwise comparisons between groups were performed using SNK-q, with P < 0.05 considered statistically significant.

[0077] 4. Results

[0078] 4.1 Determination of soil organic matter content

[0079] Compared to the control group (CK) without passivation agent, group A, treated with passivation agent, showed increased soil organic matter content. The effect of group A in increasing soil organic matter content was significantly better than groups B, C, D, and E. Figure 3 As shown.

[0080] 4.2 Determination of Cadmium Content in Chinese Cabbage

[0081] Compared to the control group (CK) without passivation agent, group A, treated with passivation agent, significantly reduced the cadmium content in pak choi leaves, with a passivation efficiency of 86.9%. The effect of group A in reducing cadmium content in pak choi leaves was significantly better than groups B, C, D, and E. Figure 4 As shown.

[0082] The weakly alkaline soil cadmium passivating agent of this invention can increase the soil organic matter content, significantly reduce the availability of cadmium in the soil, and reduce the absorption and accumulation of cadmium by crops after treating soil contaminated with heavy metal cadmium. It has a wide range of applications.

[0083] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A weakly alkaline soil cadmium passivating agent, characterized in that, The weakly alkaline soil cadmium passivating agent mainly comprises the following components by weight: 20-30 parts of graphene oxide modified biochar, 5-10 parts of montmorillonite, 5-10 parts of bentonite, and 5-10 parts of microbial inoculant. The microbial agent is a compound microbial agent composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids. The mass ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids in the microbial agent is 2-4:4-6:1-3:0.5-1, and the effective viable count of each of the Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids is ≥1.0 × 10⁻⁶. 9 cfu·g -1 The effective viable count of the compound microbial agent is ≥5.0×10⁻⁶. 9 cfu·g -1 ; The preparation method is as follows: (1) Preparation of graphene oxide modified biochar: peanut shells were dried at 60-65℃ for 10h, pulverized and passed through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide were mixed and pyrolyzed at 500-550℃ for 2-3h under nitrogen protection to obtain mixed biochar. The mixture was cooled, dried, ground and passed through a 100-mesh sieve to obtain graphene oxide modified biochar. (2) Mix the microbial agents evenly, separate the bacterial cells by centrifugation and precipitation, add galactose protectant, and freeze dry under vacuum to obtain composite microbial powder; (3) Mix biochar, montmorillonite, bentonite and compound microbial powder, grind them to obtain a weakly alkaline soil cadmium passivating agent. In step (1), the mass ratio of peanut shell powder to graphene oxide is 100-120:3; in step (2), the mass ratio of microbial cell precipitate to galactose is 1-3:

1.

2. The weakly alkaline soil cadmium passivating agent according to claim 1, characterized in that, The weakly alkaline soil cadmium passivating agent mainly comprises the following components by weight: 25 parts graphene oxide modified biochar, 8 parts montmorillonite, 10 parts bentonite, and 7 parts microbial inoculant.

3. The weakly alkaline soil cadmium passivating agent according to claim 1, characterized in that, The montmorillonite is sodium-based montmorillonite and / or calcium-based montmorillonite.

4. The weakly alkaline soil cadmium passivating agent according to claim 1, characterized in that, The microbial mass ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreductoids is 3:5:2:

1.

5. The weakly alkaline soil cadmium passivating agent according to claim 1, characterized in that, In step (1), the mass ratio of peanut shell powder to graphene oxide is 110:3; in step (2), the mass ratio of microbial cell precipitate to galactose is 2:

1.

6. The application of the weakly alkaline soil cadmium passivating agent according to claim 1 in in-situ remediation of soil heavy metal pollution.

7. The application according to claim 6, characterized in that, The heavy metal pollution mentioned refers to cadmium and / or lead pollution.

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