Preparation method of alkalescent soil cadmium passivator and passivating method for soil lead

Abstract

The invention belongs to the technical field of heavy metal pollution treatment, and relates to preparation of a weakly alkaline soil cadmium passivator and a method for passivating soil lead. The alkalescent soil cadmium passivating agent mainly comprises the following components in parts by weight: 20 to 30 parts of graphene oxide modified biochar, 5 to 10 parts of montmorillonite, 5 to 10 parts of bentonite and 5 to 10 parts of a microbial agent, the microbial agent is a composite microbial agent formed by mixing bacillus subtilis, bacillus amyloliquefaciens, bacillus thuringiensis and pseudomonas nitroreducens. The alkalescent soil cadmium passivator has a very good remediation effect on cadmium and lead in polluted soil, can remarkably improve the physicochemical properties of the cadmium and / or lead polluted soil, increase the content of organic matters in the soil, reduce the migration of the soil in the environment and reduce the content of cadmium in crops, and has a great market popularization value.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal pollution control, and relates to a preparation method of a cadmium passivator for weakly alkaline soil and a method for passivating lead in soil. Background Art

[0002] The sources of lead and cadmium elements in soil are diverse, such as atmospheric deposition, industrial wastewater and domestic sewage discharge, industrial solid waste and municipal waste dumping, and chemical pesticide application, etc.

[0003] Lead and cadmium in soil have obvious characteristics such as concealment, enrichment, irreversibility, and difficulty in treatment, which will affect the quality of crops, atmosphere and water bodies, and finally appear in the food chain and accumulate in the human body, thereby causing physiological disorders and even diseases such as lung cancer and renal insufficiency.

[0004] Different from organic pollution, the core problem of heavy metal pollution is non-degradability. Only by removing heavy metals from the soil or changing the valence and form of heavy metals in the soil, reducing their migration and bioavailability in the environment, can the remediation of heavy metal contaminated soil be achieved.

[0005] Alkaline soil includes slightly alkaline soil (pH generally 7.1 - 8.5) and strongly alkaline soil (pH generally 8.5 - 9.5). Alkaline soil has a relatively high pH and a low organic matter content. The cultivated land in the north is mainly dry land, and the soil is in an oxidized state most of the time. It is difficult to reduce the effective content of heavy metals in the soil by methods such as increasing the soil pH and continuous flooding. Further applying soil conditioners or passivators with a high pH value to medium and alkaline soil has risks such as soil compaction and reduced fertility. At present, there are few passivators suitable for cadmium-contaminated alkaline soil, and it is necessary to develop cadmium passivators with significant passivation effects on weakly alkaline soil. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a preparation method of a cadmium passivator for weakly alkaline soil and a method for passivating lead in soil. The cadmium passivator for weakly alkaline soil has a significant passivation effect on cadmium-contaminated soil, can effectively remove cadmium and lead in weakly alkaline soil, and improve the heavy metal contaminated soil environment.

[0007] To achieve the above purpose, the present application adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a cadmium passivator for weakly alkaline soil. The cadmium passivator for weakly alkaline soil mainly includes 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 composite inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreducens.

[0009] Furthermore, the weak alkaline soil cadmium passivator 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 nitroreducens in the microbial inoculant is 2-4:4-6:1-3:0.5-1, and the effective viable count of each bacterium in Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreducens is ≥1.0×10 9 cfu·g -1 , and the effective viable count of the composite bacterium agent is ≥5.0×10 9 cfu·g -1 .

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

[0013] Second, the present invention provides a preparation method of the above-mentioned weak alkaline soil cadmium passivator, and the preparation method is as follows:

[0014] (1) Preparation of graphene oxide modified biochar: Peanut shells are dried at 60-65°C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide are mixed and pyrolyzed at 500-550°C for 2-3 h under nitrogen protection to obtain mixed biochar, which is cooled, dried, ground, and sieved through a 100-mesh sieve to obtain graphene oxide modified biochar;

[0015] (2) The microbial inoculant is mixed evenly. After the microbial cells are centrifuged and precipitated, they are put into a galactose protectant and vacuum freeze-dried to obtain composite microbial powder;

[0016] (3) The biochar, montmorillonite, bentonite, and composite microbial powder are mixed and ground to obtain a weak alkaline soil cadmium passivator.

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

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

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

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

[0021] In a third aspect, the present invention provides an application of the weakly alkaline soil cadmium passivator obtained by the above preparation method in the in-situ remediation of soil heavy metal pollution.

[0022] In a fourth aspect, the present invention provides a method for using the above weakly alkaline soil cadmium passivator, and the method is: applying the composite heavy metal passivator to heavy metal-polluted soil and plowing.

[0023] Further, when the application environment is a potted plant, the application amount of the weakly alkaline soil cadmium passivator is 1%-4% of the weight of the potted soil; when the application environment is a field, the application amount of the weakly alkaline soil cadmium passivator is 150-200 kg / mu.

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

[0025] Beneficial effects achieved by the present invention:

[0026] (1) In the weakly alkaline soil cadmium passivator of the present 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 the growth of crops, and reduce the toxicity of heavy metals to crops. The type of biochar, pyrolysis conditions, addition amount, etc. will all affect the performance of biochar. Montmorillonite is mainly composed of silicon dioxide and aluminum oxide, and there is no pollution risk to the soil, providing binding sites for cadmium and lead. Bentonite is composed of silicon dioxide and aluminum trioxide, undergoes an ion exchange reaction with cadmium and lead ions in the soil, has a large specific surface area, and has 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 aggregated particles with modified biochar, fixing heavy metals or changing their existing forms, thereby reducing the bioavailability of soil heavy metals, reducing the toxicity of heavy metals to crops, and enhancing the passivation effect.

[0027] (2) The weakly alkaline soil cadmium passivator of the present invention is composed of the above raw materials, and each raw material plays a synergistic role in passivating cadmium and lead in the soil, significantly improving the physical and chemical properties of the soil polluted by cadmium and / or lead, increasing the content of soil organic matter, reducing its migration in the environment, and reducing the cadmium content in crops. Adding any one of these substances alone cannot achieve the repair effect of the present invention. The ratio of each raw material in the invention is not arbitrarily added, and the dosage of each substance has a key influence on the passivation effect of cadmium and lead.

[0028] (3) The cadmium passivator for weakly alkaline soil of the present invention has a good remediation effect on cadmium and lead in contaminated soil, can significantly improve the physical and chemical properties of soil contaminated by cadmium and / or lead, increase the soil organic matter content, reduce its migration in the environment, and reduce the cadmium content in crops, having great market promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the specific embodiments.

[0030] Figure 1 Effect of the passivator of the present invention on the content of available cadmium in soil, compared with the CK group, * P < 0.05, ** P < 0.01; compared with the A group, # P < 0.05, ## P < 0.01.

[0031] Figure 2 Effect of the passivator of the present invention on the content of available lead in soil, compared with the CK group, * P < 0.05, ** P < 0.01; compared with the A group, # P < 0.05, ## P < 0.01.

[0032] Figure 3 Effect of the passivator of the present invention on the soil organic matter content, compared with the CK group, * P < 0.05, ** P < 0.01; compared with the A group, # P < 0.05.

[0033] Figure 4 Effect of the passivator of the present invention on the cadmium content in pakchoi, compared with the CK group, * P < 0.05, ** P < 0.01; compared with the A group, # P < 0.05, ## P < 0.01. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0035] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments. The test reagents used in the following embodiments are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0036] Example 1 Weakly Alkaline Soil Cadmium Passivator and Its Preparation Method

[0037] The peanut shells are dried at 65 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide are mixed at a mass ratio of 110:3, pyrolyzed at 500 °C for 2.5 h under nitrogen protection to obtain a mixed biochar, cooled, dried, ground, and sieved through a 100-mesh sieve to obtain graphene oxide-modified biochar; the microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreducens at a mass ratio of 3∶5∶2∶1 is mixed evenly. After the microbial cells are centrifuged and precipitated and separated, they are put into a galactose protectant. The mass ratio of the microbial cell precipitate to galactose is 2∶1, and vacuum freeze-drying is carried out to obtain a composite microbial powder; the biochar, sodium-based montmorillonite, bentonite, and composite microbial powder are mixed and ground to obtain a weakly alkaline soil cadmium passivator.

[0038] Example 2 Weakly Alkaline Soil Cadmium Passivator and Its Preparation Method

[0039] The peanut shells are dried at 60 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide are mixed at a mass ratio of 100:3, pyrolyzed at 550 °C for 2 h under nitrogen protection to obtain a mixed biochar, cooled, dried, ground, and sieved through a 100-mesh sieve to obtain graphene oxide-modified biochar; the microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreducens at a mass ratio of 2∶4∶1∶1 is mixed evenly. After the microbial cells are centrifuged and precipitated and separated, they are put into a galactose protectant. The mass ratio of the microbial cell precipitate to galactose is 3∶1, and vacuum freeze-drying is carried out to obtain a composite microbial powder; the biochar, calcium-based montmorillonite, bentonite, and composite microbial powder are mixed and ground to obtain a weakly alkaline soil cadmium passivator.

[0040] Example 3 Weakly Alkaline Soil Cadmium Passivator and Its Preparation Method

[0041] The peanut shells are dried at 65 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide are mixed at a mass ratio of 120:3, and pyrolyzed at 500 °C for 3 h under nitrogen protection to obtain mixed biochar. After cooling, drying, grinding and sieving through a 100-mesh sieve, graphene oxide-modified biochar is obtained; A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens at a mass ratio of 4:6:3:0.5 is mixed evenly. After the microbial cells are centrifuged and precipitated, they are put into a galactose protectant. The mass ratio of the microbial cell precipitate to galactose is 1:1, and vacuum freeze-drying is carried out to obtain composite microbial powder; The biochar, calcium-based montmorillonite, bentonite and composite microbial powder are mixed and ground to obtain a weak alkaline soil cadmium passivator.

[0042] Example 4 Weak Alkaline Soil Cadmium Passivator and Its Preparation Method

[0043] The peanut shells are dried at 60 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide are mixed at a mass ratio of 110:3, and pyrolyzed at 550 °C for 2 h under nitrogen protection to obtain mixed biochar. After cooling, drying, grinding and sieving through a 100-mesh sieve, graphene oxide-modified biochar is obtained; A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens at a mass ratio of 4:4:3:0.5 is mixed evenly. After the microbial cells are centrifuged and precipitated, they are put into a galactose protectant. The mass ratio of the microbial cell precipitate to galactose is 1:1, and vacuum freeze-drying is carried out to obtain composite microbial powder; The biochar, sodium-based montmorillonite, bentonite and composite microbial powder are mixed and ground to obtain a weak alkaline soil cadmium passivator.

[0044] Example 5 Weak Alkaline Soil Cadmium Passivator and Its Preparation Method

[0045] The peanut shells are dried at 65 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide are mixed at a mass ratio of 120:3, and pyrolyzed at 550 °C for 3 h under nitrogen protection to obtain mixed biochar. After cooling, drying, grinding and sieving through a 100-mesh sieve, graphene oxide-modified biochar is obtained; A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens at a mass ratio of 4:4:1:1 is mixed evenly. After the microbial cells are centrifuged and precipitated, they are put into a galactose protectant. The mass ratio of the microbial cell precipitate to galactose is 3:1, and vacuum freeze-drying is carried out to obtain composite microbial powder; The biochar, sodium-based montmorillonite, bentonite and composite microbial powder are mixed and ground to obtain a weak alkaline soil cadmium passivator.

[0046] Comparative Example 1 Weak Alkaline Soil Cadmium Passivator and Its Preparation Method

[0047] Compared with Example 1, the difference is that biochar modification is not carried out.

[0048] Peanut shells are dried at 65 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder is pyrolyzed at 500 °C for 2.5 h under nitrogen protection, cooled, dried, ground, and sieved through a 100-mesh sieve to obtain biochar. A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreducens with a mass ratio of 3:5:2:1 is mixed evenly. After the microbial cells are centrifuged and precipitated, they are put into a galactose protectant. The mass ratio of the microbial cell precipitate to galactose is 2:1, and vacuum freeze-drying is carried out to obtain a composite microbial powder. The biochar, sodium-based montmorillonite, bentonite, and composite microbial powder are mixed and ground to obtain a weakly alkaline soil cadmium passivator.

[0049] Comparative Example 2 Weakly Alkaline Soil Cadmium Passivator and Its Preparation Method

[0050] Compared with Example 1, the difference is that the composite microorganisms are not protected by galactose.

[0051] Peanut shells are dried at 65 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. Peanut shell powder and graphene oxide with a mass ratio of 110:3 are mixed and pyrolyzed at 500 °C for 2.5 h under nitrogen protection to obtain mixed biochar, cooled, dried, ground, and sieved through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis, and Pseudomonas nitroreducens with a mass ratio of 3:5:2:1 is mixed evenly to obtain a composite microbial powder. The biochar, sodium-based montmorillonite, bentonite, and composite microbial powder are mixed and ground to obtain a weakly alkaline soil cadmium passivator.

[0052] Comparative Example 3 Weakly Alkaline Soil Cadmium Passivator and Its Preparation Method

[0053] Compared with Example 1, the difference is that the types and proportions of the microbial inoculant are changed.

[0054] Peanut shells are dried at 65 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. Peanut shell powder and graphene oxide with a mass ratio of 110:3 are mixed and pyrolyzed at 500 °C for 2.5 h under nitrogen protection to obtain mixed biochar, cooled, dried, ground, and sieved through a 100-mesh sieve to obtain graphene oxide-modified biochar. A microbial inoculant composed of Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus thuringiensis with a mass ratio of 4:5:2 is mixed evenly. After the microbial cells are centrifuged and precipitated, they are put into a galactose protectant. The mass ratio of the microbial cell precipitate to galactose is 2:1, and vacuum freeze-drying is carried out to obtain a composite microbial powder. The biochar, sodium-based montmorillonite, bentonite, and composite microbial powder are mixed and ground to obtain a weakly alkaline soil cadmium passivator.

[0055] Test Example 1: Influence of the Cadmium Passivator for Slightly Alkaline Soils of the Present Invention on Cadmium and Lead Pollution

[0056] 1. Experimental Method

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

[0058] The indoor soil culture method was adopted, and 7 treatments were set up: control group (CK group), Example 1 group (Group A), Example 2 group (Group B), Comparative Example 1 group (Group C), Comparative Example 2 group (Group D), Comparative Example 3 group (Group E), and Comparative Example 4 group (Group F). Each treatment was set with 3 replicates and passivated for 21 d.

[0059] The test soil sample without passivator was used as the control group. The passivators prepared from Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 with a mass fraction of 3% were used in Groups A-F respectively. The culture vessels were covered with plastic wrap and cultured in the dark. During the whole culture period, the soil humidity of each treatment was maintained at 65% of the field water holding capacity, and water was added by weighing every 2-3 d. At the same time, the culture temperature was kept constant at 20-25 °C. After the culture ended, soil samples were collected, air-dried, crushed, and passed through a 20-mesh sieve.

[0060] 2. Determination of Available Cadmium and Lead Contents in Soil

[0061] Weigh 5 g of the soil sample passivated for 21 d into a 100 mL conical flask, add 25 mL of diethylenetriaminepentaacetic acid extractant, seal it with plastic wrap and rubber band, and place it on a horizontal reciprocating shaker to shake. The shaking time is 3 h, the temperature is 23-27 °C, and the rotation speed is 160-200 r / min. After extraction, let it stand for filtration, and discard 2-3 mL of the initial filtrate. The remaining filtrate was used to determine the available cadmium and lead contents by an atomic spectrophotometer, and the carrier gas flame was acetylene.

[0062] 3. Data Processing

[0063] Data processing was carried out using Graphpad Prism 7.0 software, and measurement data were expressed as It is shown that one-way ANOVA was used for comparison among multiple groups, and SNK-q was used for pairwise comparison between groups. A statistically significant difference was defined as P < 0.05.

[0064] 4. Determination results of available cadmium and lead contents in soil

[0065] As Figure 1 , 2 shown, after 21 days of passivation treatment, compared with the CK group without passivator application, the passivator treatments in groups A and B significantly reduced the available cadmium and lead contents in the soil. The treatment in group A had the most obvious effect on reducing the available cadmium and lead contents, with passivation efficiencies of 74.3% and 77.5% respectively. The treatment in group B also had a significant effect on reducing the available cadmium and lead contents, with passivation efficiencies of 67.4% and 76.2% respectively. The effects of groups A and B in reducing the available cadmium and lead contents in the soil were significantly better than those of groups C, D, E, and F.

[0066] Test Example 2 Remediation effect of the weak alkaline soil cadmium passivator of the present invention on cadmium-polluted soil

[0067] 1. Experimental method

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

[0069] Cd(NO3)2 with corresponding concentration was added to the above soil, stirred evenly, air-dried in the dark for 2 weeks, ground, and passed through a 20-mesh sieve to prepare cadmium-polluted soil with a Cd 2+ content of 15 mg / kg.

[0070] The indoor soil culture method was adopted, and 6 treatments were set: control group (CK group), Example 1 group (group A), Comparative Example 1 group (group B), Comparative Example 2 group (group C), Comparative Example 3 group (group D), and Comparative Example 4 group (group E). Each treatment had 3 replicates, totaling 18 pots. The test soil sample without passivator was used as the control group, and the passivators prepared from Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 with a mass fraction of 3% were used in groups A - F respectively.

[0071] After mixing each passivator with the soil evenly, it was transferred to flower pots, and each pot was filled with 2 kg of soil. Chinese cabbage seeds were planted in the cadmium-polluted simulated soil. When the Chinese cabbage grew to 10 cm, 3 evenly growing seedlings were retained in each pot, watered regularly to keep the soil water holding capacity at 65%, and grown in a greenhouse at 25 - 30 °C for 30 days. Then soil samples were collected and Chinese cabbage plants were harvested.

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

[0073] 2.1 The determination of soil organic matter content was carried out by the dichromate-sulfuric acid solution oxidation method.

[0074] 2.2 The determination of cadmium content in pakchoi: Pakchoi was harvested at 30 d. First, it was rinsed with distilled water, and then soaked in 20 mmol / L Na2EDTA for 15 - 20 min to remove Cd on the root surface 2+ , and finally it was washed clean with distilled water. The Cd content in the leaves 2+ was determined by microwave digestion and inductively coupled plasma optical emission spectrometer.

[0075] 3. Data processing

[0076] Data processing was performed using Graphpad Prism 7.0 software. Measurement data were expressed as . One-way analysis of variance was used for comparison among multiple groups, and SNK-q was used for pairwise comparison between groups. A P value < 0.05 was considered statistically significant.

[0077] 4. Results

[0078] 4.1 The determination of soil organic matter content

[0079] Compared with CK without applying the passivator, the passivator treatment in group A could increase the soil organic matter content. The effect of increasing the soil organic matter content in group A was significantly better than that in groups B, C, D, and E. As Figure 3 shown.

[0080] 4.2 The determination of cadmium content in pakchoi

[0081] Compared with CK without applying the passivator, the passivator in group A significantly reduced the cadmium content in pakchoi leaves, and the passivation efficiency of the treatment in group A was 86.9%. The effect of reducing the cadmium content in pakchoi leaves in group A was significantly better than that in groups B, C, D, and E. As Figure 4 shown.

[0082] After treating heavy metal cadmium-polluted soil with the weak alkaline soil cadmium passivator of the present invention, it can increase the soil organic matter content, significantly reduce the availability of heavy metal cadmium in the soil, reduce the absorption and enrichment of cadmium by crops, and has wide applications.

[0083] The above are only embodiments of the present invention, and common general technical solutions and / or characteristics in the solutions are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope claimed in this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A cadmium passivator for weakly alkaline soil, characterized in that, The weak alkaline soil cadmium passivator 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 inoculum; The microbial inoculum is a composite microbial inoculum composed of a mixture of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens.

2. The cadmium passivator for weakly alkaline soil according to claim 1, wherein The weak alkaline soil cadmium passivator 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 inoculum.

3. The cadmium passivator for weakly alkaline soil according to claim 1, wherein The montmorillonite is sodium-based montmorillonite and / or calcium-based montmorillonite.

4. The cadmium passivator for weakly alkaline soil according to claim 1, wherein In the microbial inoculum, the microbial mass ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens is 2-4∶4-6∶1-3: 0.5-1, and the effective viable count of each inoculum in Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens is ≥1.0×10 9 cfu·g -1 , and the effective viable count of the compound inoculum is ≥5.0×10 9 cfu·g -1 .

5. The cadmium passivator for weakly alkaline soil according to claim 4, wherein The microbial mass ratio of Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus thuringiensis and Pseudomonas nitroreducens is 3:5:2:

1.

6. The cadmium passivator for weakly alkaline soil according to claim 1, characterized in that, The preparation method is as follows: (1) Preparation of graphene oxide modified biochar: Peanut shells are dried at 60-65 °C for 10 h, crushed and sieved through a 100-mesh sieve to obtain peanut shell powder. The peanut shell powder and graphene oxide are mixed and pyrolyzed at 500-550 °C for 2-3 h under nitrogen protection to obtain mixed biochar. After cooling, drying, grinding and sieving through a 100-mesh sieve, graphene oxide modified biochar is obtained; (2) The microbial inoculum is mixed evenly. After the microbial cells are centrifuged and precipitated and separated, they are put into a galactose protectant and vacuum freeze-dried to obtain composite microbial powder; (3) The biochar, montmorillonite, bentonite and composite microbial powder are mixed and ground to obtain a weak alkaline soil cadmium passivator.

7. The cadmium passivator for weakly alkaline soil according to claim 1, characterized in that, The mass ratio of peanut shell powder to graphene oxide is 100-120:3; in the step (2), the mass ratio of the microbial cell precipitate to galactose is 1-3:

1.

8. The cadmium passivator for weakly alkaline soil according to claim 7, characterized in that, In the step (1), the mass ratio of peanut shell powder to graphene oxide is 110:3; in the step (2), the mass ratio of the microbial cell precipitate to galactose is 2:

1.

9. Application of the weak alkaline soil cadmium passivator according to claim 1 in in-situ remediation of soil heavy metal pollution.

10. The application according to claim 9, characterized in that, The heavy metal pollution is cadmium and / or lead pollution.

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