Soil heavy metal biological passivator as well as preparation method and application thereof

Abstract

The invention discloses a soil heavy metal biological passivator as well as a preparation method and application thereof, belongs to the technical field of contaminated soil remediation, and provides a soil heavy metal biological passivator which comprises a mineral compound and a biological modifier, the mineral compound comprises bentonite and sepiolite; the biological modifier comprises reed straw biochar and an arbuscular mycorrhizal fungus inoculant; the mass ratio of the mineral compound to the biological improver is 1: (1-3). The preparation method of the soil heavy metal biological passivator comprises the following steps: carbonizing reed straws to obtain reed straw biochar; mixing with an arbuscular mycorrhizal fungus inoculant, shaking with a constant temperature, filtering, and washing trapped fluid to obtain a biological modifier; mixing bentonite with sepiolite to obtain a mineral compound; and combining the biological modifier with the mineral compound to obtain the soil heavy metal biological passivator. The soil heavy metal biological passivator does not need to worry about secondary damage to soil due to excessive adding amount, and the working efficiency is improved.

Description

Technical Field

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

[0002] Current situation of soil heavy metal pollution Soil heavy metal pollution has become a global environmental problem, posing a serious threat to the ecosystem, agricultural production, and human health. Heavy metals such as cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), etc. have the characteristics of high toxicity, poor mobility, and non-degradability. Once they enter the soil, they will accumulate through the food chain and ultimately endanger human health. For example, cadmium poisoning can cause osteoporosis and kidney damage; lead has a serious impact on the nervous system, especially on the development of children. At present, the remediation technologies for soil heavy metal pollution mainly include physical and chemical methods and bioremediation methods. Physical and chemical methods such as leaching, solidification / stabilization, and electrokinetic remediation, etc. Although these methods have significant effects, they usually have high costs, complex operations, and may damage the soil structure and fertility. Bioremediation methods use plants, microorganisms, or their metabolites to immobilize, transform, or extract heavy metals, and have the advantages of environmental protection, economy, and sustainability, so they have received extensive attention. Research progress of biostabilizers In recent years, biostabilizers, as a new type of soil remediation material, have been favored due to their high efficiency, safety, and environmental friendliness. Biostabilizers mainly reduce the bioavailability of heavy metals in the soil through the following mechanisms: complexation: forming stable chelates with heavy metals to reduce their free concentration in the soil solution; precipitation: by changing the soil pH value or providing a precipitation matrix, promoting heavy metals to exist in the form of insoluble minerals; adsorption: using the active functional groups on the material surface to capture heavy metal ions and limit their migration ability. Research shows that some natural organic matters (such as humic acid, chitosan) and microbial metabolites (such as siderophores, polysaccharides) have good passivation effects. However, existing biostabilizers generally have problems such as complex preparation processes, high costs, or unstable passivation efficiencies, which limit their large-scale application.

[0003] Although biostabilizers show great potential in the field of soil remediation, they still face the following problems that need to be solved urgently: limited material sources, many biostabilizers rely on specific microorganisms or plant extracts, with long production cycles and high costs; unstable passivation efficiency, affected by factors such as soil type, heavy metal type, and environmental conditions, it is difficult to guarantee the effects of existing passivators. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a soil heavy metal biological passivator, its preparation method and application, which can release arbuscular mycorrhizal fungi (AMF) loaded in reed straw biochar according to changes in external conditions such as temperature, pH value and light. When using the soil heavy metal passivator, there is no need to worry about excessive addition causing secondary damage to the soil, thus facilitating the actual application of the soil heavy metal passivator by humans and improving work efficiency.

[0005] To achieve the above object, the present invention provides a soil heavy metal biological passivator, comprising a mineral complex and a biological modifier;

[0006] The mineral complex includes bentonite and sepiolite; the biological modifier includes reed straw biochar and arbuscular mycorrhizal fungi inoculant;

[0007] The mass ratio of the mineral complex to the biological modifier is 1:1 - 3.

[0008] Preferably, the mass ratio of bentonite to sepiolite in the mineral complex is 1 - 2:1.

[0009] Preferably, the mass ratio of reed straw biochar to arbuscular mycorrhizal fungi inoculant in the biological modifier is 1:1 - 5.

[0010] The present invention also provides a preparation method of the soil heavy metal biological passivator, comprising the following steps:

[0011] (1) Carbonize reed straw to obtain reed straw biochar;

[0012] (2) Mix the reed straw biochar obtained in step (1) with arbuscular mycorrhizal fungi inoculant, use a constant temperature shaker, filter, and wash the retentate to obtain a biological modifier;

[0013] (3) Mix bentonite and sepiolite to obtain a mineral complex;

[0014] (4) Combine the biological modifier obtained in step (2) with the mineral complex obtained in step (3) to obtain the soil heavy metal biological passivator.

[0015] Preferably, in step (1), the carbonization temperature is 500 - 600 °C and the carbonization time is 1 - 3 h.

[0016] Preferably, in step (2), the effective viable count of the arbuscular mycorrhizal fungi inoculant is 50 - 80 spores / g.

[0017] Preferably, in step (2), the rotation speed of the constant temperature shaker is 160 - 200 rpm, the temperature of the constant temperature shaker is 26 - 30 °C, and the time of the constant temperature shaker is 48 - 72 h.

[0018] Preferably, the filtration in step (2) is carried out using a 200-mesh nylon mesh, the washing in step (2) is carried out using an aqueous sodium chloride solution with a mass concentration of 0.85%, and the number of washing times is 1 to 3 times.

[0019] The present invention also provides the application of the soil heavy metal biological passivator in reducing cadmium pollution in soil, and the dosage of the soil heavy metal biological passivator is calculated according to 1% of the soil quality.

[0020] The present invention also provides the application of the soil heavy metal biological passivator in reducing the cadmium content of crops planted in cadmium-polluted soil.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] The present invention provides a soil heavy metal biological passivator, its preparation method and application. A mineral complex prepared by mixing bentonite and sepiolite is combined with an AMF biological modifier loaded on reed straw biochar to prepare a soil heavy metal passivator. It can release arbuscular mycorrhizal fungi (AMF) loaded in the reed straw biochar according to changes in external conditions such as temperature, pH value, and light. When using the soil heavy metal passivator, there is no need to worry about excessive addition causing secondary damage to the soil, thus facilitating the actual application of the soil heavy metal passivator by humans and improving work efficiency. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 are the available Cd contents in the rhizosphere and non-rhizosphere of different groups. In the figure, CK is the polluted soil without any treatment as the blank control group, AM is the first comparative example group, M1 / S1 is the first example group, M2 / S1 is the fourth example group, M1 / S2 is the fourth comparative example group, CKF is the polluted soil without any treatment in the non-rhizosphere as the blank control group, AMF is the first comparative example group in the non-rhizosphere, M1 / S1F is the first example group in the non-rhizosphere, M2 / S1F is the fourth example group in the non-rhizosphere, M1 / S2F is the fourth comparative example group in the non-rhizosphere. Different lowercase letters in the figure represent significant differences;

[0025] Figure 2For the available Pb content in the rhizosphere and non-rhizosphere of different groups, in the figure, CK is the contaminated soil without any treatment as the blank control group, AM is the control group of Comparative Example 1, M1 / S1 is the group of Example 1, M2 / S1 is the group of Example 4, M1 / S2 is the group of Comparative Example 4, CKF is the contaminated soil without any treatment in the non-rhizosphere as the blank control group, AMF is the non-rhizosphere control group of Comparative Example 1, M1 / S1F is the non-rhizosphere group of Example 1, M2 / S1F is the non-rhizosphere group of Example 4, M1 / S2F is the non-rhizosphere group of Comparative Example 4. Different lowercase letters in the figure represent significant differences;

[0026] Figure 3 For the Cd content and the percentage reduction of Cd content in the wheat grain of different groups, CK is the contaminated soil without any treatment as the blank control group, AM is the control group of Comparative Example 1, M1 / S1 is the group of Example 1, M2 / S1 is the group of Example 4, M1 / S2 is the group of Comparative Example 4. Different lowercase letters in the figure represent significant differences;

[0027] Figure 4 For the Pb content and the percentage reduction of Pb content in the wheat grain of different groups, CK is the contaminated soil without any treatment as the blank control group, AM is the control group of Comparative Example 1, M1 / S1 is the group of Example 1, M2 / S1 is the group of Example 4, M1 / S2 is the group of Comparative Example 4. Different lowercase letters in the figure represent significant differences;

[0028] Figure 5 It is a comparison chart of the growth trends of wheat in the blank control group and the experimental group. Among them, A is the comparison chart of the growth trends of wheat in the blank control group and the control group of Comparative Example 3. In the figure, CK represents the blank control group, and 1% BC + 1% P represents the control group of Comparative Example 3. B is the comparison chart of the growth trends of wheat in the blank control group and the group of Example 1. In the figure, CK represents the blank control group, and 1% BC + 1% P + 1% AMF represents the group of Example 1. Detailed implementation manners

[0029] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. In addition, 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.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0032] Without departing from the scope or spirit of this invention, various modifications and variations can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this invention are merely exemplary.

[0033] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0034] Sources of materials used in this invention: Bentonite was purchased from Lishi Bentonite Processing Co., Ltd. in Xuanhua County, Zhangjiakou City, Hebei Province; sepiolite was purchased from Jinyuan Bentonite Factory in Kedao Tun, Zunhua City, Tangshan City, Hebei Province; reed straw was sourced from the reeds in the Baiyangdian Wetland.

[0035] Extraction method of arbuscular mycorrhizal fungi used in this invention: The wet sieving decantation - sucrose centrifugation method was adopted to isolate arbuscular mycorrhizal fungi AMF spores from the in-situ Cd and Pb contaminated soil (the specific location of soil collection was the farmland soil north of Yucheng Village, Qingyuan District, Baoding City, Hebei Province). Weigh 50 g of soil, soak it in 1 L of water and let it stand for 30 min, stir it quickly and evenly and then let it stand for 10 min. Pour out the upper suspension and sieve it through a 200-mesh nylon sieve. After sieving, place the sieved material in a 100 mL centrifuge tube, add water to half of the tube, centrifuge at 1500 r / min for 3 min and then discard the supernatant. Add a 40% sucrose aqueous solution to half of the 100 mL centrifuge tube to the lower precipitate after wet sieving, centrifuge at 1500 r / min for 10 min, sieve the supernatant through a 400-mesh sieve, and rinse it with water to remove the sucrose solution to obtain AMF fungal spores. Collect the AMF fungal spores obtained by wet sieving into a petri dish, observe the morphology of the spores under a stereomicroscope (Nikon, SMZ745T), select the spores with consistent size, color and morphology, place them in clean water and store them at 4°C. The storage time should not exceed one month, and the spores should be regularly checked for deterioration.

[0036] Sow tobacco in sterilized river sand and cultivate until it has 3 - 6 true leaves, which can be used as the host plant seedlings required for single spore isolation culture. Under a dissecting microscope, use a capillary tube to directly place a single spore of AMF fungi after disinfection on the root system of a seedling, and then plant the seedling in a seedling raising device. After culturing for 3 weeks using the semi-hydroponic method, mycorrhizal infection generally occurs. This method can obtain single spore isolation cultures relatively quickly. It is also possible to disinfect the surface of the spores obtained by wet sieving, select a single spore, directly place it in the disinfected substrate in a container, and then sow the surface-disinfected (surface disinfected with 75% ethanol, 0.1% mercuric chloride or 0.1% sodium hypochlorite for 5 minutes and rinsed with sterile water) germinated seeds of the host plant. After 3 months of growth, there will be a new generation of spores in the culture medium that have propagated from a single spore, and a pure line can be obtained.

[0037] To expand the reproduction of the pure line from single spore isolation culture, the pot enrichment culture method can be used. The specific method is to load the disinfected river sand into a pot after treatment, mix the single spore isolation culture, including spores, sporocarps, mycelium or (and) mycorrhizal root segments, into the culture medium in the pot, and then sow the surface-disinfected seeds of clover, alfalfa or tobacco host plants. During the cultivation and growth process, diluted Hoagland nutrient solution (KH2PO3 136g / L 1mL, KNO3 101g / L 5mL, Ca(NO3)2 236g / L 5mL, MgSO4 246.5g / L 2mL, H3BO3 2.86g / L 1mL, MnCl2·4H2O 1.81g / L 1mL, ZnSO4·7H2O 0.22g / L 1mL, CuSO4·5H2O 0.08g / L 1mL, H2MnO4·H2O 0.02g / L 1mL, FeEDTA 1mL) can be applied regularly according to needs. Generally, after 3 months of growth, the enriched culture of this pure line, that is, the arbuscular mycorrhizal fungal inoculum, can be obtained.

[0038] Example 1

[0039] (1) Carbonize reed straw at 550 °C for 2 h to obtain reed straw biochar;

[0040] (2) Mix reed straw biochar and arbuscular mycorrhizal fungal inoculum (effective viable spore count is 65 spores / g) in a mass ratio of 1:3, shake at 180 rpm in a constant temperature shaker at 28 °C for 60 h, filter using a 200-mesh nylon net, and wash the retained liquid 2 times with a 0.85% sodium chloride aqueous solution to obtain a biological modifier;

[0041] (3) Mix bentonite and sepiolite in a mass ratio of 1:1 to obtain a mineral complex;

[0042] (4) Combine the biological modifier and the mineral complex in a mass ratio of 2:1 to obtain a soil heavy metal biological passivator.

[0043] Example 2

[0044] (1) Reed straw was carbonized at 500 °C for 3 h to obtain reed straw biochar;

[0045] (2) The reed straw biochar was mixed with arbuscular mycorrhizal fungal inoculant (effective viable count of 50 spores / g) at a mass ratio of 1:1, shaken at 160 rpm in a constant temperature shaker at 26 °C for 72 h, filtered through a 200-mesh nylon screen, and the retained liquid was washed once with a 0.85% sodium chloride aqueous solution to obtain a biological modifier;

[0046] (3) Bentonite and sepiolite were mixed at a mass ratio of 2:1 to obtain a mineral complex;

[0047] (4) The biological modifier and the mineral complex were combined at a mass ratio of 1:1 to obtain a soil heavy metal biological passivator.

[0048] Example 3

[0049] (1) Reed straw was carbonized at 600 °C for 1 h to obtain reed straw biochar;

[0050] (2) The reed straw biochar was mixed with arbuscular mycorrhizal fungal inoculant (effective viable count of 80 spores / g) at a mass ratio of 1:5, shaken at 200 rpm in a constant temperature shaker at 30 °C for 48 h, filtered through a 200-mesh nylon screen, and the retained liquid was washed 3 times with a 0.85% sodium chloride aqueous solution to obtain a biological modifier;

[0051] (3) Bentonite and sepiolite were mixed at a mass ratio of 1:1 to obtain a mineral complex;

[0052] (4) The biological modifier and the mineral complex were combined at a mass ratio of 3:1 to obtain a soil heavy metal biological passivator.

[0053] Example 4

[0054] (1) Reed straw was carbonized at 550 °C for 2 h to obtain reed straw biochar;

[0055] (2) The reed straw biochar was mixed with arbuscular mycorrhizal fungal inoculant (effective viable count of 65 spores / g) at a mass ratio of 1:3, shaken at 180 rpm in a constant temperature shaker at 28 °C for 60 h, filtered through a 200-mesh nylon screen, and the retained liquid was washed 2 times with a 0.85% sodium chloride aqueous solution to obtain a biological modifier;

[0056] (3) Bentonite and sepiolite were mixed at a mass ratio of 2:1 to obtain a mineral complex;

[0057] (4) The biological modifier and the mineral complex are combined at a mass ratio of 2:1 to obtain the soil heavy metal biological passivator.

[0058] Comparative Example 1

[0059] An arbuscular mycorrhizal fungal inoculant with an effective viable spore count of 65 spores / g is used as the passivator.

[0060] Comparative Example 2

[0061] (1) Reed straw is carbonized at 550 °C for 2 h to obtain reed straw biochar;

[0062] (2) The reed straw biochar and the arbuscular mycorrhizal fungal inoculant (with an effective viable spore count of 65 spores / g) are mixed at a mass ratio of 1:3, shaken at 180 rpm in a constant temperature shaker at 28 °C for 60 h, filtered through a 200-mesh nylon net, and the retained liquid is washed twice with a sodium chloride aqueous solution with a mass concentration of 0.85% to obtain the biological modifier.

[0063] Comparative Example 3

[0064] (1) Reed straw is carbonized at 550 °C for 2 h to obtain reed straw biochar;

[0065] (2) Bentonite and sepiolite are mixed at a mass ratio of 1:1 to obtain the mineral complex;

[0066] (4) The reed straw biochar and the mineral complex are combined at a mass ratio of 2:1 to obtain the passivator.

[0067] Comparative Example 4

[0068] (1) Reed straw is carbonized at 550 °C for 2 h to obtain reed straw biochar;

[0069] (2) The reed straw biochar and the arbuscular mycorrhizal fungal inoculant (with an effective viable spore count of 65 spores / g) are mixed at a mass ratio of 1:3, shaken at 180 rpm in a constant temperature shaker at 28 °C for 60 h, filtered through a 200-mesh nylon net, and the retained liquid is washed twice with a sodium chloride aqueous solution with a mass concentration of 0.85% to obtain the biological modifier;

[0070] (3) Bentonite and sepiolite are mixed at a mass ratio of 1:2 to obtain the mineral complex;

[0071] (4) The biological modifier and the mineral complex are combined at a mass ratio of 2:1 to obtain the soil heavy metal biological passivator.

[0072] Experimental Example 1

[0073] Experiments were conducted using the soil heavy metal biostabilizer prepared in Example 1, the soil heavy metal biostabilizer prepared in Example 4, the stabilizer in Comparative Example 1, the biological modifier prepared in Comparative Example 2, and the soil heavy metal biostabilizer prepared in Comparative Example 4, which were respectively designated as the Example 1 group, the Example 4 group, the Comparative Example 1 group, the Comparative Example 2 group, and the Comparative Example 4 group. The contaminated soil without any treatment was used as the blank control group.

[0074] The original soil was sourced from the farmland soil in the north of Yucheng Village, Qingyuan District, Baoding City, Hebei Province. The contaminated soil was obtained by adding 10 mg / kg CdCl2 to the original soil and aging it for 30 days.

[0075] The soil heavy metal biostabilizer prepared in Example 1, the soil heavy metal biostabilizer prepared in Example 4, the stabilizer in Comparative Example 1, the biological modifier prepared in Comparative Example 2, and the soil heavy metal biostabilizer prepared in Comparative Example 4 were respectively mixed evenly with the contaminated soil at a mass fraction ratio of 1%. After 1 month of treatment, the cadmium (Cd) concentrations in the soils of different groups were detected respectively; then 10 disinfected wheat seeds were planted in polyethylene pots (5 kg / pot) containing the soils treated with different groups, and after growing for 6 months, the growth conditions of wheat in different groups were observed. The experimental results are shown in Table 1 below.

[0076] Table 1 Changes in Cd concentrations in soils and wheat plants of different groups

[0077]

[0078]

[0079]

[0080] According to Table 1, in the Example 1 group using the soil heavy metal biostabilizer of the present invention, the wheat grew well, the biomass increased, the branches and leaves were the most lush, and the Cd content in the wheat kernels was the lowest.

[0081] As Figure 1 shown, for the available Cd contents in the rhizosphere and non-rhizosphere of different groups, it can be seen from Figure 1 that the available Cd content in the group containing bentonite / sepiolite 1:1 (M1 / S1) in the Example 1 group was the lowest.

[0082] As Figure 2 shown, for the available Pb contents in the rhizosphere and non-rhizosphere of different groups, it can be seen from Figure 2 that the available Pb content in the group containing bentonite / sepiolite 1:1 (M1 / S1) in the Example 1 group was the lowest.

[0083] As Figure 3 shown, for the Cd contents in the wheat kernels of different groups, fromFigure 3 It can be seen that the Cd content in wheat grains of the group in Example 1 containing bentonite / sepiolite 1:1 (M1 / S1) is the lowest.

[0084] As Figure 4 shown, it is the Pb content in wheat grains of different groups. From Figure 4 it can be seen that the Pb content in wheat grains of the group in Example 1 containing bentonite / sepiolite 1:1 (M1 / S1) is the lowest.

[0085] As Figure 5 shown in A, it is the comparison chart of the growth trends of wheat in the blank control group (CK) of contaminated soil without any treatment and the group in Comparative Example 3 (1% BC + 1% P) applying the passivator prepared in Comparative Example 3. From Figure 5 the description in A, it can be known that the growth trend of wheat in the group in Comparative Example 3 is slightly better than that in the blank control group; as Figure 5 shown in B, it is the comparison chart of the growth trends of wheat in the blank control group (CK) of contaminated soil without any treatment and the group in Example 1 (1% BC + 1% P + 1% AMF) applying the soil heavy metal biological passivator prepared in Example 1. From Figure 5 the description in B, it can be known that the growth trend of wheat in the group applying the soil heavy metal biological passivator prepared in Example 1 is vigorous.

[0086] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A biological passivator for heavy metals in soil, characterized in that, It includes a mineral complex and a biological conditioner; The mineral complex includes bentonite and sepiolite; the biological conditioner includes reed straw biochar and arbuscular mycorrhizal fungal inoculant; The mass ratio of the mineral complex to the biological conditioner is 1:1 - 3.

2. The heavy metal biological passivator for soil according to claim 1, wherein The mass ratio of bentonite to sepiolite in the mineral complex is 1 - 2:

1.

3. The soil heavy metal biological passivator according to claim 1, wherein The mass ratio of reed straw biochar to arbuscular mycorrhizal fungal inoculant in the biological conditioner is 1:1 - 5.

4. The preparation method of the soil heavy metal biological passivator according to any one of claims 1 to 3, characterized in that, It includes the following steps: (1) Carbonize reed straw to obtain reed straw biochar; (2) Mix the reed straw biochar obtained in step (1) with arbuscular mycorrhizal fungal inoculant, use a constant temperature shaker, filter, and take the retentate for washing to obtain the biological conditioner; (3) Mix bentonite and sepiolite to obtain the mineral complex; (4) Combine the biological conditioner obtained in step (2) with the mineral complex obtained in step (3) to obtain the soil heavy metal biological passivator.

5. The preparation method according to claim 4, characterized in that, In step (1), the temperature of the carbonization is 500 - 600 °C, and the time of the carbonization is 1 - 3 h.

6. The preparation method according to claim 4, characterized in that, In step (2), the effective viable count in the arbuscular mycorrhizal fungal inoculant is 50 - 80 spores / g.

7. According to the preparation method described in claim 4, characterized in that, In step (2), the rotation speed of the constant temperature shaker is 160 - 200 rpm, the temperature of the constant temperature shaker is 26 - 30 °C, and the time of the constant temperature shaker is 48 - 72 h.

8. The preparation method according to claim 4, characterized in that, In step (2), the filtration is carried out using a 200 - mesh nylon mesh, the washing in step (2) is carried out using a sodium chloride aqueous solution with a mass concentration of 0.85%, and the number of washing times is 1 - 3 times.

9. Use of the soil heavy metal biological passivator according to any one of claims 1 to 3 in reducing cadmium pollution in soil, characterized in that, The dosage of the soil heavy metal biological passivator is calculated according to 1% of the soil mass.

10. Use of the soil heavy metal biological passivator according to any one of claims 1 - 3 in reducing the cadmium content of crops grown in cadmium - contaminated soil.

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