Method for treating heavy metals in soil by microorganisms

Abstract

The invention discloses a method for treating heavy metal in soil with microorganisms, and belongs to the technical field of soil remediation, the method comprises the following steps: (1) soil treatment: ploughing the soil polluted by the heavy metal with the ploughing depth of 30-40cm; (2) heavy metal treatment: adding a heavy metal treatment agent into the soil, turning over the soil again to enable the heavy metal treatment agent to be in full contact with the soil, then irrigating the land, adjusting the moisture content of the soil to 25-30%, covering the surface of the soil with a layer of plastic film after irrigation is completed, and removing the plastic film after treatment is completed, the problem that the heavy metal treatment efficiency is reduced because the initial growth of microorganisms is inhibited by heavy metal is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a method for treating heavy metals in soil by using microorganisms. Background Art

[0002] With the development of modern science and technology, soil pollution is becoming increasingly serious, and heavy metal pollution is the main problem in soil pollution, which has the characteristics of concealment, difficulty in degradation, poor mobility and easy enrichment. The main sources of heavy metals in soil are factory waste and agricultural production, and the increasingly serious heavy metal pollution in soil has seriously endangered the ecological environment and human health. Therefore, how to solve the heavy metal pollution in soil has become a focus issue at present. At present, the use of microorganisms to treat soil heavy metal pollution, using microorganisms to adsorb, reduce, and transform heavy metals to reduce or remove heavy metal pollutants, has good effects and little impact on environmental pollution. It is one of the main technical methods for heavy metal soil remediation. However, in the early stage of treatment, the amount of microorganisms is small, and the concentration of heavy metals in the soil is high at this time, which will reduce the metabolic capacity and activity of microorganisms, and the growth and reproduction of microorganisms are inhibited by heavy metals, resulting in a decrease in the efficiency of microorganisms in treating heavy metals.

[0003] Therefore, the present invention provides a method for treating heavy metals in soil with microorganisms, which promotes the growth and reproduction of early microorganisms and solves the problem that the initial growth of microorganisms is inhibited by heavy metals. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for treating heavy metals in soil by using microorganisms, which solves the problem that the initial growth of microorganisms is inhibited by heavy metals, resulting in reduced heavy metal treatment efficiency.

[0005] The present invention solves the above technical problems by the following technical means:

[0006] A method for treating heavy metals in soil with microorganisms, the method comprising the following steps:

[0007] (1) Soil treatment: Plough the heavy metal-contaminated soil to a depth of 30-40 cm and clean up weeds and gravel in the soil;

[0008] (2) Heavy metal treatment: Add heavy metal treatment agent to the soil, turn the soil again to allow the heavy metal treatment agent to fully contact the soil, then irrigate the land and adjust the soil moisture content to 25-30%. After irrigation, cover the soil surface with a layer of plastic film, and remove the film after the treatment is completed.

[0009] Furthermore, the processing time in step (2) is 50-60 days.

[0010] Furthermore, the heavy metal treatment agent in step (2) includes heavy metal treatment agent A and heavy metal treatment agent B, wherein the heavy metal treatment agent A and the heavy metal treatment agent B are uniformly mixed in a mass ratio of 1:1.

[0011] Furthermore, the amount of heavy metal treatment agent used is 2 Apply 30-40g of heavy metal treatment agent to the soil.

[0012] Further, the preparation method of the heavy metal treatment agent is as follows:

[0013] Preparation method of heavy metal treatment agent A:

[0014] S1: Glucose is added to water, stirred until completely dissolved to obtain a glucose solution, and then β-cyclodextrin is added to the glucose solution, mixed evenly, and then the solution temperature is heated to 80-90° C., gelatin is added, mixed evenly, and then dried at 0-5° C. for 2-3 hours and then crushed to obtain particles A;

[0015] S2: adding cassava starch to water at 70-80° C. for gelatinization, cooling to room temperature after gelatinization, adding papain solution, mixing evenly to obtain solution A, spraying the solution on the surface of the composite particles, and drying at 20-30° C. for 30-40 min to obtain treatment agent A;

[0016] Preparation method of heavy metal treatment agent B:

[0017] S1: Mix soybean meal, diatomaceous earth and seaweed polysaccharide evenly, place in a granulator for granulation to obtain solid particles, place the solid particles into microbial fermentation liquid for adsorption, take out and naturally air-dry to obtain particles B;

[0018] S2: Add xanthan gum to water, stir evenly and heat the solution to 90-95°C, then add polyvinyl alcohol and glutaraldehyde, mix evenly and cool to room temperature to obtain a mixed gel; put particle B into the mixed gel until particle B is fully coated, then take it out and dry it at 20-30°C for 30-40 minutes to obtain heavy metal treatment agent B.

[0019] Furthermore, the mass ratio of glucose, β-cyclodextrin and gelatin in the heavy metal treatment agent A is (1.2-1.5):(1-1.2):(4-5), and the mass ratio of cassava starch and papain is (10-15):(1-1.2).

[0020] Furthermore, the mass ratio of soybean meal, diatomaceous earth and seaweed polysaccharide in the trace heavy metal treatment agent B is (6-8):(3-4):(2-3), and the mass ratio of xanthan gum, polyvinyl alcohol and glutaraldehyde is (3-4):(1-1.2):(0.15-0.2).

[0021] Furthermore, the particle size of the solid particles in the trace heavy metal treatment agent B is 2-3 mm.

[0022] Furthermore, the preparation method of the microbial fermentation broth in the trace heavy metal treatment agent B is as follows:

[0023] Trichoderma harzianum and Bacillus subtilis were inoculated into PDA medium respectively and activated at 23-26°C for 3-5 days. After activation, the bacterial cakes of each strain were selected and added into the fermentation liquid medium at an inoculum of 2% and cultured in a shaking table at 25-28°C and 200-220 r / min. When the effective viable bacteria count in each mixed fermentation liquid medium reached (4-5)×10 6 CFU / mL, the fermentation was stopped to obtain fermentation broths respectively, and then the fermentation broths were mixed in a volume ratio of 1:1 to obtain microbial fermentation broth.

[0024] Furthermore, the fermentation liquid culture medium is composed of: 5-6g glucose, 12-15g yeast powder, 0.1-0.2g magnesium sulfate, 0.1-0.15g potassium dihydrogen phosphate, and 1000ml distilled water. After preparation, it is sterilized at a high temperature of 120°C with steam for 20-25min.

[0025] The decomposition rate of heavy metal treatment agent A is greater than that of metal treatment agent B. Heavy metal treatment agent A can form an environment suitable for microbial growth in the soil in advance, ensuring that heavy metal treatment agent B has the best breeding place when slowly releasing the internal fermentation liquid, and prompting microorganisms to grow and reproduce rapidly in the early stage of treatment to form a dominant flora. Specifically, heavy metal treatment agent B contains microbial fermentation liquid, and microorganisms can grow and reproduce in the soil after being released. Through the adsorption of its cell wall and extracellular polymers, heavy metal ions are adsorbed on the cell surface or inside, thereby reducing the content of heavy metals in the soil. However, after the microorganisms in heavy metal treatment agent B are released, the initial content is low, and the high heavy metal content has a significant inhibitory effect on microbial reproduction, and may even cause microbial death, thereby reducing the treatment efficiency of heavy metal treatment agent B. Therefore, a mixed gel is sprayed on the surface of heavy metal treatment agent B. The mixed gel is a three-dimensional mesh structure formed by cross-linking xanthan gum and polyvinyl alcohol, which improves the stability of the mixed gel, can delay the decomposition rate of treatment agent B, and allows the organism to be slowly released from heavy metal treatment agent B.

[0026] In addition, heavy metal treatment agent A is also added. The papain contained on the surface of heavy metal treatment agent A can promote the hydrolysis of gelatin, produce more nutrients such as polypeptides and amino acids, and cooperate with the glucose of heavy metal treatment agent A to provide nutrition and carbon source for the growth of microorganisms exposed in metal treatment agent B, promote the growth and reproduction of microorganisms, improve the activity of microorganisms, promote microorganisms to secrete more extracellular polymers, and improve the adsorption capacity of heavy metals. At the same time, the β-cyclodextrin in heavy metal treatment agent A can complex heavy metals in the soil, reduce the heavy metal content in the soil, and avoid excessive heavy metal concentrations interfering with the growth of initial microorganisms.

[0027] Therefore, through the combined action of heavy metal treatment agent A and heavy metal treatment agent B, the initial growth and reproduction rate of microorganisms can be effectively increased, and the efficiency of microorganisms in treating heavy metals can be improved.

[0028] Beneficial effects:

[0029] The heavy metal treatment agent A and the heavy metal treatment agent B prepared by the present invention work together to effectively reduce the content of heavy metals in the soil, solve the problem of heavy metal pollution in the soil, effectively restore the ecological function of the soil, and improve the soil quality. In addition, the heavy metal treatment particles prepared by the present invention are green and pollution-free, and will not affect the environment or subsequent crop planting. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to specific embodiments:

[0031] Embodiment 1:

[0032] Microbial fermentation broth:

[0033] After thawing, Trichoderma harzianum and Bacillus subtilis were inoculated into PDA medium respectively and activated at 23°C for 3 days. After activation, the bacterial cakes of each strain were selected and added into the fermentation liquid medium at an inoculum of 2% and cultured in a shaking table at 25°C and 200 r / min. When the effective viable bacteria count in each mixed fermentation liquid medium reached 4×10 6 CFU / mL, stop fermentation, obtain fermentation broth respectively, and then mix the fermentation broth in a volume ratio of 1:1 to obtain microbial fermentation broth, wherein the fermentation liquid culture medium is composed of: 5g glucose, 12g yeast powder, 0.g magnesium sulfate, 0.1g dipotassium hydrogen phosphate, 1000ml distilled water, and is sterilized at a high temperature of 120℃ with steam for 20min.

[0034] Heavy metal treatment agent A:

[0035] S1: 1.2 g of glucose was added to 100 ml of water, and stirred until completely dissolved to obtain a glucose solution. Then 1 g of β-cyclodextrin was added to the glucose solution, and the solution temperature was heated to 80°C after mixing evenly. 4 g of gelatin was added, and the mixture was dried at 0°C for 2 h and then crushed to obtain particles A.

[0036] S2: 10 g of cassava starch was added to 100 ml of 70° C. water for gelatinization. After gelatinization, the mixture was cooled to room temperature. A papain solution prepared by mixing 1 g of papain with 10 ml of water was added. The mixture was mixed evenly to obtain a solution A, which was sprayed on the surface of the composite particles and dried at 20° C. for 30 min to obtain a treatment agent A.

[0037] Heavy metal treatment agent B:

[0038] S1: Soybean meal, diatomaceous earth and seaweed polysaccharide are uniformly mixed in a mass ratio of 6:3:2, and placed in a granulator for granulation to obtain solid particles with a particle size of 2 mm, and the solid particles are placed in a microbial fermentation liquid for adsorption, and taken out and naturally air-dried to obtain particles B;

[0039] S2: Add 3g xanthan gum to 100ml water, stir evenly and heat the solution to 90°C, then add 1g polyvinyl alcohol and 0.15g glutaraldehyde, mix evenly and cool to room temperature to obtain a mixed gel; put particle B into the mixed gel until particle B is fully coated, take it out, and dry it at 20°C for 30min to obtain heavy metal treatment agent B.

[0040] Methods of treating heavy metals in soil with microorganisms:

[0041] (1) Soil treatment: The heavy metal-contaminated soil is plowed to a depth of 30 cm and weeds and gravel are removed from the soil;

[0042] (2) Heavy metal treatment: Add heavy metal treatment agent to the soil. The heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 1:1. 2 The soil was treated with 30g of heavy metal treatment agent, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 25%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 50 days of treatment.

[0043] Embodiment 2:

[0044] Microbial fermentation broth:

[0045] After thawing, Trichoderma harzianum and Bacillus subtilis were inoculated into PDA medium respectively and activated at 24°C for 4 days. After activation, the bacterial cakes of each strain were selected and added into the fermentation liquid medium at an inoculum of 2% and shaken at 26°C and 210 r / min. When the effective viable bacteria count in each mixed fermentation liquid medium reached 4.5×10 6 CFU / mL, stop fermentation, obtain fermentation broth respectively, and then mix the fermentation broth in a volume ratio of 1:1 to obtain microbial fermentation broth. The composition of the fermentation liquid culture medium is: 5.5g glucose, 14g yeast powder, 0.15g magnesium sulfate, 0.13g potassium hydrogen phosphate, 1000ml distilled water, and it is sterilized at a high temperature of 120℃ with steam for 22min.

[0046] Heavy metal treatment agent A:

[0047] S1: 1.35 g of glucose was added to 112 ml of water, and stirred until completely dissolved to obtain a glucose solution. Then 1.1 g of β-cyclodextrin was added to the glucose solution, and the solution temperature was heated to 85° C., 4.5 g of gelatin was added, and the mixture was dried at 2° C. for 2.5 h and then crushed to obtain particles A.

[0048] S2: 12.5 g of cassava starch was added to 125 ml of 75° C. water for gelatinization. After gelatinization, the mixture was cooled to room temperature. A papain solution prepared by mixing 1.1 g of papain with 11 ml of water was added. The mixture was mixed evenly to obtain a solution A, which was sprayed on the surface of the composite particles and dried at 25° C. for 35 min to obtain a treatment agent A.

[0049] Heavy metal treatment agent B:

[0050] S1: Soybean meal, diatomaceous earth and seaweed polysaccharide were mixed uniformly in a mass ratio of 7:3.5:2.5, and placed in a granulator for granulation to obtain solid particles with a particle size of 2.5 mm, and the solid particles were placed in a microbial fermentation liquid for adsorption, and then taken out and naturally air-dried to obtain particles B;

[0051] S2: Add 3.5g xanthan gum to 140ml water, stir evenly and heat the solution to 95°C, then add 1g polyvinyl alcohol and 0.18g glutaraldehyde, mix evenly and cool to room temperature to obtain a mixed gel; put particle B into the mixed gel until particle B is fully coated, take it out, and dry it at 25°C for 35min to obtain heavy metal treatment agent B.

[0052] Methods of treating heavy metals in soil with microorganisms:

[0053] (1) Soil treatment: The heavy metal-contaminated soil is plowed to a depth of 35 cm and weeds and gravel are removed from the soil;

[0054] (2) Heavy metal treatment: Add heavy metal treatment agent to the soil. The heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 1:1. 2 The soil was treated with 35g of heavy metal treatment agent, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 28%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 55 days of treatment.

[0055] Embodiment 3:

[0056] Microbial fermentation broth:

[0057] After thawing, Trichoderma harzianum and Bacillus subtilis were inoculated into PDA medium respectively and activated at 26°C for 5 days. After activation, the bacterial cakes of each strain were selected and added into the fermentation liquid medium at an inoculum of 2% and cultured in a shaking incubator at 28°C and 220 r / min. When the number of effective live bacteria in each mixed fermentation liquid medium reached 5×10 6 CFU / mL, stop fermentation, obtain fermentation broth respectively, and then mix the fermentation broth in a volume ratio of 1:1 to obtain microbial fermentation broth. The fermentation liquid culture medium is composed of: 6g glucose, 15g yeast powder, 0.2g magnesium sulfate, 0.15g potassium hydrogen phosphate, 1000ml distilled water, and is sterilized at a high temperature of 120°C with steam for 25min.

[0058] Heavy metal treatment agent A:

[0059] S1: 1.5 g of glucose was added to 125 ml of water, and stirred until completely dissolved to obtain a glucose solution. Then 1.2 g of β-cyclodextrin was added to the glucose solution, and the solution temperature was heated to 90° C., 5 g of gelatin was added, and the mixture was dried at 5° C. for 2 h and then crushed to obtain particles A.

[0060] S2: 15 g of cassava starch was added to 150 ml of 70° C. water for gelatinization. After gelatinization, the mixture was cooled to room temperature. A papain solution prepared by mixing 1.2 g of papain with 12 ml of water was added. The mixture was mixed evenly to obtain a solution A, which was sprayed on the surface of the composite particles and dried at 30° C. for 40 min to obtain a treatment agent A.

[0061] Heavy metal treatment agent B:

[0062] S1: Soybean meal, diatomaceous earth and seaweed polysaccharide were mixed uniformly in a mass ratio of 8:4:3, placed in a granulator for granulation to obtain solid particles with a particle size of 3 mm, placed the solid particles in a microbial fermentation liquid for adsorption, and taken out and naturally air-dried to obtain particles B;

[0063] S2: Add 4 g of xanthan gum to 120 ml of water, stir evenly, heat the solution to 90°C, then add 1.2 g of polyvinyl alcohol and 0.2 g of glutaraldehyde, mix evenly, and cool to room temperature to obtain a mixed gel; put particle B into the mixed gel until particle B is fully coated, take it out, and dry it at 30°C for 40 minutes to obtain heavy metal treatment agent B.

[0064] Methods of treating heavy metals in soil with microorganisms:

[0065] (1) Soil treatment: The heavy metal-contaminated soil is plowed to a depth of 40 cm and weeds and gravel are removed from the soil;

[0066] (2) Heavy metal treatment: Add heavy metal treatment agent to the soil. The heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 1:1. 2 The soil was treated with 40g of heavy metal treatment agent, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 30%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 60 days of treatment.

[0067] Comparative Example 1:

[0068] This comparative example is in contrast to Example 1, the only difference being that the raw materials for preparing the heavy metal treatment agent A are different, specifically, no glucose is added, and the specific method is as follows:

[0069] S1: Add 1 g of β-cyclodextrin to 100 ml of water, stir until completely dissolved to obtain a β-cyclodextrin solution, then heat the β-cyclodextrin solution to 80°C, add 4 g of gelatin, mix well, dry at 0°C for 2 hours, and then grind to obtain particles A;

[0070] S2: 10 g of cassava starch was added to 100 ml of 70° C. water for gelatinization. After gelatinization, the mixture was cooled to room temperature. 1 g of papain was mixed with 10 ml of water to prepare a papain solution. The mixture was evenly mixed to obtain a solution A, which was sprayed on the surface of the composite particles and dried at 20° C. for 30 min to obtain a treatment agent A.

[0071] The method of treating heavy metals in soil with microorganisms in this comparative example is the same as that in Example 1.

[0072] Comparative Example 2:

[0073] This comparative example is in contrast to Example 1, the only difference being that the raw materials for preparing the heavy metal treatment agent A are different, specifically, no β-cyclodextrin is added, and the specific method is as follows:

[0074] S1: 1.2 g of glucose was added to 100 ml of water, and stirred until completely dissolved to obtain a glucose solution. The glucose solution was then heated to 80°C, 4 g of gelatin was added, and the mixture was evenly mixed and dried at 0°C for 2 h and then crushed to obtain particles A.

[0075] S2: 10 g of cassava starch was added to 100 ml of 70° C. water for gelatinization. After gelatinization, the mixture was cooled to room temperature. 1 g of papain was mixed with 10 ml of water to prepare a papain solution. The mixture was evenly mixed to obtain a solution A, which was sprayed on the surface of the composite particles and dried at 20° C. for 30 min to obtain a treatment agent A.

[0076] The method of treating heavy metals in soil with microorganisms in this comparative example is the same as that in Example 1.

[0077] Comparative Example 3:

[0078] This comparative example is in contrast to Example 1, the only difference being that the raw materials for preparing heavy metal treatment A are different, specifically, no papain or cassava starch is added, and the specific method is as follows:

[0079] S1: Add 1.2 g of glucose to 100 ml of water, stir until completely dissolved to obtain a glucose solution, then add 1 g of β-cyclodextrin to the glucose solution, mix well, heat the solution to 80°C, add 4 g of gelatin, mix well, dry at 0°C for 2 hours, and then crush to obtain a heavy metal treatment agent A.

[0080] The method of treating heavy metals in soil with microorganisms in this comparative example is the same as that in Example 1.

[0081] Comparative Example 4:

[0082] This comparative example is in contrast to Example 1, the only difference being that the raw materials for preparing the heavy metal treatment agent B are different, specifically, the mixed gel is replaced with gelatin, and the specific method is as follows:

[0083] S1: Soybean meal, diatomaceous earth and seaweed polysaccharide are uniformly mixed in a mass ratio of 6:3:2, and placed in a granulator for granulation to obtain solid particles with a particle size of 2 mm, and the solid particles are placed in a microbial fermentation liquid for adsorption, and taken out and naturally air-dried to obtain particles B;

[0084] S2: Add 3 g of gelatin to 100 ml of water, stir evenly, heat the solution to 90°C, then add 0.15 g of glutaraldehyde, mix evenly, and cool to room temperature to obtain gelatin gel; put particle B into the gelatin gel until particle B is fully coated, take it out, and dry it at 20°C for 30 minutes to obtain heavy metal treatment agent B.

[0085] The method of treating heavy metals in soil with microorganisms in this comparative example is the same as that in Example 1.

[0086] Comparative Example 5:

[0087] This comparative example is in contrast to Example 1, the only difference being that the process of preparing the heavy metal treatment agent B is different, specifically, the particles B are not mixed with gel to be coated, and the specific method is as follows:

[0088] S1: Soybean meal, diatomaceous earth and seaweed polysaccharide are uniformly mixed in a mass ratio of 6:3:2, placed in a granulator for granulation to obtain solid particles with a particle size of 2 mm, the solid particles are placed in microbial fermentation liquid for adsorption, taken out and naturally air-dried to obtain heavy metal treatment agent B.

[0089] The method of treating heavy metals in soil with microorganisms in this comparative example is the same as that in Example 1.

[0090] Comparative Example 6:

[0091] This comparative example is in contrast to Example 1, the only difference being that no heavy metal treatment agent A is added to the heavy metal treatment agent, that is, only heavy metal treatment agent B is added, and the specific method is as follows;

[0092] (1) Soil treatment: The heavy metal-contaminated soil is plowed to a depth of 30 cm and weeds and gravel are removed from the soil;

[0093] (2) Heavy metal treatment: Add heavy metal treatment agent B to the soil, 2 The soil was treated with 30g of heavy metal treatment agent B, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 25%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 50 days of treatment.

[0094] In this comparative example, the microbial treatment agent B is the same as that in Example 1.

[0095] Comparative Example 7:

[0096] This comparative example is in contrast to Example 1, the only difference being that the heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 2:1, and the specific method is as follows:

[0097] (1) Soil treatment: The heavy metal-contaminated soil is plowed to a depth of 30 cm and weeds and gravel are removed from the soil;

[0098] (2) Heavy metal treatment: Add heavy metal treatment agent to the soil. The heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 2:1. 2The soil was treated with 30g of heavy metal treatment agent, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 25%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 50 days of treatment.

[0099] In this comparative example, heavy metal treatment agent A and heavy metal treatment agent B are the same as those in Example 1.

[0100] Comparative Example 8:

[0101] This comparative example is in contrast to Example 1, the only difference being that the heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 1:2, and the specific method is as follows:

[0102] (1) Soil treatment: The heavy metal-contaminated soil is plowed to a depth of 30 cm and weeds and gravel are removed from the soil;

[0103] (2) Heavy metal treatment: Add heavy metal treatment agent to the soil. The heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 1:2. 2 The soil was treated with 30g of heavy metal treatment agent, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 25%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 50 days of treatment.

[0104] In this comparative example, heavy metal treatment agent A and heavy metal treatment agent B are the same as those in Example 1.

[0105] Comparative Example 9:

[0106] This comparative example is in contrast to Example 1, except that microbial fermentation liquid is used instead of heavy metal treatment agent B, and the specific method is as follows:

[0107] (1) Soil treatment: The heavy metal-contaminated soil is plowed to a depth of 30 cm and weeds and gravel are removed from the soil;

[0108] (2) Heavy metal treatment: Add heavy metal treatment agent A and microbial fermentation liquid to the soil. 2 The soil was treated with 15 g of heavy metal treatment agent A and 15 g of microbial fermentation liquid, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 25%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 50 days of treatment.

[0109] The microbial fermentation broth used in this comparative example is the same as that prepared in Example 1.

[0110] experiment:

[0111] Experimental setup: Soil without heavy metal contamination was dug as experimental soil. The soil area of ​​each experimental group was 2m 2 , with a thickness of 30cm, and then add heavy metal ions to simulate heavy metal contaminated soil. The specific situation is as follows:

[0112] CuSO4, ZnSO4, and Pb(NO3)2 were selected to make aqueous solutions, and then added to the soil to make the soil contain Cu 2 + 、Zn 2+ , Pb 2 The initial concentration was 100 mg / kg. After standing for two days, the solution was stirred evenly before conducting the experiment.

[0113] Experimental group 1 used heavy metal treatment agent A and heavy metal treatment agent B prepared in Example 1;

[0114] Comparative groups 1-5 used heavy metal treatment agent A and heavy metal treatment agent B prepared in comparative examples 1-5, respectively; the heavy metal treatment method was as follows:

[0115] (1) Heavy metal treatment: Add heavy metal treatment agent to the soil. The heavy metal treatment agent is a mixture of heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 1:1. 2 After applying 30g of heavy metal treatment agent to the soil, stir the soil to make the heavy metal treatment agent fully contact with the soil, then irrigate the land and adjust the soil moisture content to 25%. After irrigation, cover the soil surface with a layer of plastic film and remove the film after 50 days of treatment.

[0116] Comparative group 6 used only the heavy metal treatment agent B prepared in Example 1, with an amount of 2 30 g of heavy metal treatment agent B was used on the soil.

[0117] Comparative groups 7-8 used heavy metal treatment agent A and heavy metal treatment agent B prepared in Example 1, wherein the heavy metal treatment agent of comparative group 7 was mixed with heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 2:1, and the heavy metal treatment agent of comparative group 8 was mixed with heavy metal treatment agent A and heavy metal treatment agent B in a mass ratio of 1:2.

[0118] Comparative group 9 uses the treatment agent A prepared in Example 1 and the microbial fermentation liquid, and its heavy metal treatment method is as follows:

[0119] (1) Heavy metal treatment: Add heavy metal treatment agent A and microbial fermentation liquid to the soil. 2The soil was treated with 15 g of heavy metal treatment agent A and 15 g of microbial fermentation liquid, and the soil was turned over again to allow the heavy metal treatment agent to fully contact the soil. The land was then irrigated to adjust the soil moisture content to 25%. After the irrigation was completed, a layer of plastic film was covered on the soil surface, and the film was removed after 50 days of treatment.

[0120] The blank group was not treated.

[0121] Sampling: After the treatment, the five-point sampling method was adopted to collect soil from the surface layer, 10 cm of the tillage layer, and 20 cm of the tillage layer. The soil samples were mixed and the heavy metals (Cu 2+ 、Zn 2+ , Pb 2+ ) content, the results are shown in Table 1:

[0122] Table 1

[0123] <![CDATA[Cu 2+ (mg / kg)]]> <![CDATA[Zn 2+ (mg / kg)]]> <![CDATA[Pb 2+ (mg / kg)]]> Experimental Group 1 38.41 52.05 25.25 Comparison group 1 51.04 65.87 38.05 Comparison group 2 50.51 64.02 37.86 Comparison group 3 55.13 71.44 45.84 Comparison group 4 56.12 73.65 48.02 Comparison group 5 59.66 76.23 52.81 Comparison group 6 66.33 82.66 58.18 Comparison group 7 45.87 60.58 32.31 Comparison group 8 52.15 67.56 40.45 Comparison group 9 63.52 79.45 54.45 Blank Group 97.21 98.24 96.35

[0124] Analyzing Table 1, we can get:

[0125] 1. Compared with experimental group 1, the difference between comparison groups 1-3 is that the raw materials for preparing heavy metal treatment agent A are different. No glucose was added to comparison group 1, the initial microbial carbon source amount was reduced, the microbial activity was low, and the growth and reproduction rate of microorganisms was slow, resulting in a decrease in the efficiency of heavy metal treatment of heavy metals in comparison group 1, so its heavy metal content was high. No β-cyclodextrin was added to comparison group 2, and its heavy metal content was high. This is because β-cyclodextrin can complex heavy metals in the soil and reduce the heavy metal content in the soil, so that the heavy metal content in the initial growth environment of the organism is low, while no β-cyclodextrin was added to comparison group 2, and the heavy metal content in the initial growth environment of the microorganism was high, which inhibited the growth and reproduction of microorganisms, resulting in a decrease in the treatment efficiency of heavy metals. No papain and cassava starch were added to comparison group 3, and the decomposition rate of heavy metal treatment agent A was slow, resulting in the heavy metal treatment agent B starting to release microorganisms. The heavy metal treatment agent A did not create a good growth environment for the microorganisms, resulting in the inhibition of the initial growth and reproduction of microorganisms by heavy metals, resulting in a decrease in the treatment efficiency of heavy metals.

[0126] 2. Compared with experimental group 1, in control group 4, the mixed gel was replaced with gelatin. Compared with the mixed gel, gelatin can be degraded by microorganisms faster, resulting in a faster release of microorganisms in heavy metal treatment agent B. At this time, the heavy metal content in the soil was high, and the heavy metal treatment agent A was not well decomposed. The growth environment of the microorganisms was poor and the growth was inhibited, resulting in a low heavy metal treatment efficiency. Compared with experimental group 1, in control group 5, the particles B were not wrapped with mixed gel, and the microorganisms were released too quickly. At this time, the heavy metal treatment agent A was not well decomposed. The microorganisms were in an environment with a high heavy metal content, and their growth and reproduction were inhibited, resulting in a low heavy metal treatment efficiency.

[0127] 3. Compared with experimental group 1, control group 6 did not add heavy metal treatment agent A, that is, only heavy metal treatment agent B was added. After the microorganisms were released, their growth and reproduction were inhibited by the high heavy metal content in the surrounding environment, resulting in poor heavy metal treatment efficiency. Compared with experimental group 1, control group 7 had heavy metal treatment agents A and B mixed evenly at a mass ratio of 2:1. The amount of heavy metal treatment agent A was large, resulting in other microorganisms in the soil growing faster and becoming dominant populations, affecting the microorganisms released from heavy metal treatment agent B. The amount of heavy metal treatment agent B added was small, resulting in a small content of microorganisms in the soil, and the treatment effect on heavy metals was poor. Compared with experimental group 1, control group 8 had heavy metal treatment agents A and B mixed evenly at a mass ratio of 1:2. The amount of heavy metal treatment agent A added was small, and the amount of substances decomposed by it that were beneficial to microbial growth was small. The growth rate of microorganisms was not as good as that of experimental group 1, and its heavy metal treatment effect was poor.

[0128] 4. Compared with experimental group 1, control group 9 was treated with heavy metal treatment agent A and microbial fermentation liquid. Microorganisms were directly added to the soil, and the initial content was low. Heavy metals inhibited the growth of microorganisms, and heavy metal treatment agent A could not be well decomposed to create a good growth environment for microorganisms, resulting in a decrease in the reproduction of microorganisms, a decrease in the treatment effect of heavy metals, and a high content of heavy metals in the soil.

[0129] 5. The blank group was not treated with heavy metal treatment agents, and the heavy metal content in its soil was high, while the heavy metal content in the soil treated by experimental group 1 was low, indicating that the heavy metal treatment agent prepared by experimental group 1 can effectively reduce the content of heavy metals in the soil, and the heavy metal treatment efficiency is relatively high.

[0130] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. A method for treating heavy metals in soil using microorganisms, characterized in that: The method comprises the following steps: (1) Soil treatment: Plough the heavy metal-contaminated soil to a depth of 30-40 cm; (2) Heavy metal treatment: Add heavy metal treatment agent to the soil, turn the soil again to allow the heavy metal treatment agent to fully contact the soil, then irrigate the land and adjust the soil moisture content to 25-30%. After irrigation, cover the soil surface with a layer of plastic film, and remove the film after the treatment is completed.

2. A method for treating heavy metals in soil with microorganisms according to claim 1, characterized in that: The processing time in step (2) is 50-60 days.

3. The method for treating heavy metals in soil with microorganisms according to claim 2, characterized in that: The heavy metal treatment agent in step (2) includes heavy metal treatment agent A and heavy metal treatment agent B, wherein the heavy metal treatment agent A and the heavy metal treatment agent B are uniformly mixed in a mass ratio of 1:

1.

4. The method for treating heavy metals in soil with microorganisms according to claim 3, characterized in that: The amount of heavy metal treatment agent used is per 1m 2 Apply 30-40g of heavy metal treatment agent to the soil.

5. The method for treating heavy metals in soil with microorganisms according to claim 4, characterized in that: The preparation method of the heavy metal treatment agent is as follows: Heavy metal treatment agent A: S1: Glucose is added to water, stirred until completely dissolved to obtain a glucose solution, and then β-cyclodextrin is added to the glucose solution, mixed evenly, and then the solution temperature is heated to 80-90° C., gelatin is added, mixed evenly, and then dried at 0-5° C. for 2-3 hours and then crushed to obtain particles A; S2: adding cassava starch to water at 70-80° C. for gelatinization, cooling to room temperature after gelatinization, adding papain solution, mixing evenly to obtain solution A, spraying the solution on the surface of the composite particles, and drying at 20-30° C. for 30-40 min to obtain treatment agent A; Heavy metal treatment agent B: S1: Mix soybean meal, diatomaceous earth and seaweed polysaccharide evenly, place in a granulator for granulation to obtain solid particles, place the solid particles into microbial fermentation liquid for adsorption, take out and naturally air-dry to obtain particles B; S2: Add xanthan gum to water, stir evenly and heat the solution to 90-95°C, then add polyvinyl alcohol and glutaraldehyde, mix evenly and cool to room temperature to obtain a mixed gel; put particle B into the mixed gel until particle B is fully coated, take it out, dry it at 20-30°C for 30-40 minutes, and obtain heavy metal treatment agent B.

6. A method for treating heavy metals in soil with microorganisms according to claim 5, characterized in that: The mass ratio of glucose, β-cyclodextrin and gelatin in the heavy metal treatment agent A is (1.2-1.5):(1-1.2):(4-5), and the mass ratio of cassava starch and papain is (10-15):(1-1.2).

7. A method for treating heavy metals in soil with microorganisms according to claim 6, characterized in that: The mass ratio of soybean meal, diatomaceous earth and seaweed polysaccharide in the trace heavy metal treatment agent B is (6-8):(3-4):(2-3), and the mass ratio of xanthan gum, polyvinyl alcohol and glutaraldehyde is (3-4):(1-1.2):(0.15-0.2).

8. The method for treating heavy metals in soil with microorganisms according to claim 7, characterized in that: The particle size of the solid particles in the trace heavy metal treatment agent B is 2-3 mm.

9. The method for treating heavy metals in soil with microorganisms according to claim 8, characterized in that: The preparation method of the microbial fermentation liquid in the trace heavy metal treatment agent B is as follows: Trichoderma harzianum and Bacillus subtilis were inoculated into PDA medium respectively and activated at 23-26°C for 3-5 days. After activation, the bacterial cakes of each strain were selected and added into the fermentation liquid medium at an inoculum of 2% and cultured in a shaking table at 25-28°C and 200-220 r / min. When the effective viable bacteria count in each mixed fermentation liquid medium reached (4-5)×10 6 CFU / mL, the fermentation was stopped to obtain fermentation broths respectively, and then the fermentation broths were mixed in a volume ratio of 1:1 to obtain microbial fermentation broth.