Method for dissociating nutritional components in coal gangue and controlling harmful heavy metals through bacillus fungicide

Abstract

The invention provides a method for dissociating nutritional components in coal gangue and controlling harmful heavy metals through a bacillus fungicide, and belongs to the technical field of coal gangue utilization, and the method comprises the following steps: a, crushing, screening, calcining and mixing coal gangue to obtain mixed coal gangue; b, compounding to obtain a mixed bacillus inoculant; and c, dissociating the mixed coal gangue by the mixed bacillus to obtain the improved coal gangue. The improved coal gangue obtained by the invention has the characteristics of environmental protection, recycling, effectiveness and the like, the contents of alkali-hydrolyzable nitrogen, available phosphorus, quick-acting potassium and available silicon of the improved coal gangue are obviously increased, the content of heavy metals is obviously reduced, and the improved coal gangue can be used for improving barren soil.

Description

Technical Field

[0001] The invention belongs to the technical field of coal gangue utilization, and particularly relates to a method for dissociating nutrient components in coal gangue and controlling harmful heavy metals by using a bacillus bacterial agent. Background Art

[0002] Coal gangue is a solid waste discharged during coal mining and coal washing. It is a companion rock of coal seams during coal formation. Compared with ordinary coal, it has the characteristics of low carbon content, hard texture, and low calorific value. It is a kind of solid waste in mines. At present, coal gangue has become one of the industrial solid wastes with the largest emission, and the emission is equivalent to about 10% to 20% of coal production. Coal gangue also causes environmental problems such as water pollution, land destruction, and air pollution, endangering human life and health. The composition of coal gangue is complex, and the composition will vary greatly due to different origins, and the properties are also different, which brings great difficulties to the comprehensive utilization of coal gangue. Therefore, it is very important and urgent to effectively treat coal gangue.

[0003] The content of nitrogen, phosphorus, potassium, silicon and other nutrients in coal gangue is similar to that in soil, and the organic matter content is 2-10 times higher than that in soil. In addition, it can potentially reduce soil adhesion, improve soil porosity, and be beneficial to crop growth and fruit quality. If coal gangue can be effectively used in agriculture, the pressure on the environment caused by coal gangue can be alleviated to a large extent. However, the biggest problem with coal gangue as a plant nutrient is that the content of effective phosphorus, potassium and silicon in coal gangue that can be directly absorbed and utilized by plants is lower than that in soil. The nutrients contained in coal gangue usually exist in the form of oxides, silicates, etc. that cannot be directly absorbed and utilized by plants, and need to be further converted into soluble forms that can be directly absorbed and utilized by plants. In recent years, researchers have found that some bacteria have the characteristics of dissolving phosphorus, potassium, silicon and nitrogen, and can be used to dissolve nutrients in minerals. However, a large number of studies have focused on the phosphorus dissolving ability of bacteria and their effective application as biofertilizers for plant growth and crop yields, and there are few studies on the use of microbial methods to dissociate nutrients in different types of coal gangue. When using coal gangue for soil improvement, while achieving improvement effects and nutrient dissolution, we should also pay attention to its potential ecological risks, monitor its heavy metal content, and seek appropriate preventive measures to control its migration into the soil.

[0004] Therefore, it is necessary to find suitable and effective bacteria to decompose the nutrients in coal gangue to solve the problem of land fertilizer shortage and realize the large-scale recycling of coal gangue. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies in the prior art and provide a method for dissociating nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-type bacterial agent, which can be used to improve poor agricultural soil. The method can significantly increase the content of alkaline nitrogen, available phosphorus, available potassium, and available silicon in activated coal gangue, while reducing the content of heavy metals in the coal gangue.

[0006] The purpose of the present invention can be achieved by the following technical measures:

[0007] The present invention provides a method for dissociating nutrient components in coal gangue and controlling harmful heavy metals by using a bacillus-based inoculant, comprising pre-treating coal gangue, compounding to obtain a mixed bacillus inoculant, dissociating the mixed coal gangue by the mixed bacillus, and drying to obtain improved coal gangue, etc. The method comprises the following steps:

[0008] a. Pretreatment of coal gangue: crush, grind and screen the coal gangue into powder; calcine the coal gangue powder at 500-550°C for 2h-3h to obtain calcined activated coal gangue, mix the calcined activated coal gangue with the original coal gangue after grinding in a mass ratio of 1:1-1:4, and store for later use;

[0009] b. Compounding to obtain a mixed bacillus inoculant: selecting Bacillus megaterium (ACCC03031), Bacillus mucilaginosus (ACCC19749), and Bacillus subtilis (ACCC 19743) from the China Agricultural Microbiological Culture Collection Center, and naming them A1, A2, and A3 respectively, culturing the slant seeds stored at 0-4°C in a solid culture medium, rinsing the cultured bacillus into a triangular flask, adjusting the bacterial content of the bacterial solution and the pH value of the bacterial solution with tap water to obtain a suspension of a single bacterial species, and mixing the suspensions of A1, A2, and A3 at a volume ratio of (1.0-2.5):(1.0-2.0):1 to obtain a mixed bacterial solution;

[0010] c. Dissociating mixed coal gangue with mixed Bacillus: inoculating the mixed bacterial agent obtained in step b into the mixed coal gangue powder obtained in step a for fermentation and culturing, and then drying to obtain improved coal gangue.

[0011] Preferably, in step a, the gangue is processed into powder with a particle size of ≤0.5 mm. Mixing the calcined activated gangue and the raw gangue in a mass ratio of 1:1-1:4 can significantly increase the fertilizer nutrient elements. Preferably, the mass ratio of the calcined activated gangue to the raw gangue is 1:3.

[0012] Preferably, in step b, a tryptone soy solid culture medium is used, wherein each 1000 mL of distilled water contains 10-20 g of soytone, 3-9 g of trypsin, 3-10 g of sodium chloride, and 15-45 g of agar. After heating and dissolving, and adjusting the pH value to 7.0-7.4, the culture medium is divided into containers and sterilized at 121°C in an autoclave for 20-30 min, and then the bacteria inoculated in the solid culture medium are cultured at 25-30°C for 2-3 days.

[0013] Preferably, in step b, the bacterial count in the suspension of the single bacterial species is 5×10 11 ~ 10×10 13 cfu·ml -1 , use 1 mol / L dilute H2SO4 solution and 1 mol / L dilute HCl solution to adjust the pH value of the bacterial solution to 6-9, and use tap water to prepare the bacterial suspension, which makes the operation simple and convenient in actual production.

[0014] Preferably, in step c, the mixed bacterial agent and the mixed coal gangue are mixed at a solid-liquid ratio of 1:2-2:1, wherein the unit of the mixed bacterial liquid is ml, and the unit of the mixed coal gangue is g.

[0015] Preferably, in step c, during the fermentation culture, ventilation and oxygen supply are performed, the temperature is controlled at 25-35° C., the humidity is controlled at 35-55%, and the culture is statically cultured for 1-7 days, preferably 4 days.

[0016] Preferably, in step c, the drying temperature is 50-60° C., and the moisture content of the improved coal gangue is ≤3.0%.

[0017] The present invention applies coal gangue to the barren soil to be improved, and the alkaline nitrogen, available phosphorus, available potassium and available silicon therein are determined according to the third edition of "Soil Agrochemical Analysis" -12227476. The heavy metal content is determined according to the standard HJ781-2016 "Determination of 22 metal elements in solid waste by inductively coupled plasma emission spectrometry". The invention has the characteristics of environmental protection, resource utilization and effectiveness. The improved coal gangue has an alkali-hydrolyzed nitrogen content of 150-200 mg / kg, an effective phosphorus content of 20-40 mg / kg, an available potassium content of 300-400 mg / kg, an effective silicon content of 300-350 mg / kg, and heavy metal contents (Cd, Pb, Cr, Ni, As, Cu, and Zn are 0 mg / kg, 80-106 mg / kg, 100-116 mg / kg, 45-65 mg / kg, 30-41 mg / kg, 50-63 mg / kg, and 150-200 mg / kg, respectively) all meeting the requirements of GB15618-2018 "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standards", and will not cause environmental harm to soil and crops.

[0018] The reaction mechanism of the present invention is: the gangue calcined at 500-550°C contains more glassy and amorphous substances, forms large pores of tens of microns inside, increases porosity, maintains water absorption at 20%, and the measured heavy metal content is greatly reduced. The reduction in heavy metal content may be because the heavy metal structure of the gangue after calcination is more stable, and a small amount of heavy metal components in the gangue can be adsorbed on the surface of the bacteria through electrostatic effects, chemical bonds, etc., enter the bacteria through the form of ion channels, and fix the heavy metal ions in the form of sulfides, iron oxides, etc. Bacillus produces a large number of flagella and some protein components of the bacterial outer membrane, which allows Bacillus to adsorb on the surface of coal gangue to produce organic acids, such as citric acid, lactic acid, acetic acid, etc. The protonation of organic acids and the chelation of cationic organic acid ligands destroy the mineral crystal structure of coal gangue such as orthoclase, Berlinite, and muscovite, making it easier for beneficial elements such as P, K, N, and Si to dissolve.

[0019] Compared with the prior art, the present invention has the following advantages and innovations:

[0020] (1) Coal gangue has a large output and low cost, which can release effective elements to the maximum extent and control heavy metals. It can be used to solve the problem of shortage of land fertilizer in China, and is conducive to the large-scale recycling and utilization of coal gangue and the maximization of economic benefits.

[0021] (2) By using calcined coal gangue to increase the content of nutrients and reduce heavy metals, bacterial agents can be selected more specifically for different poor soils. It has a good improvement effect on the minerals, water retention and absorption, and soil compaction of poor soils.

[0022] (3) The element content used in this method makes it easier for plants to absorb nutrients and can better reflect the actual nutrient content of coal gangue. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 The present invention is a process flow chart of a technology for dissociating nutrient components in coal gangue and controlling harmful heavy metals by using Bacillus bacteria agents.

[0025] Figure 2(a) is the XRD pattern of coal gangue;

[0026] Figure 2(b) is the XRD pattern of coal gangue after calcination. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0028] The selected coal gangue comes from the Buertai Mine in Ordos City, Inner Mongolia. Its main chemical components are silicon dioxide and aluminum oxides (accounting for 74.31% in total), followed by sulfur oxides (7.87%) and iron oxides (6.76%). The main elements are shown in Table 1. Coal gangue contains nutrients such as nitrogen, phosphorus, potassium, and silicon. Usually, only the parts of these elements in the form of alkaline nitrogen, effective phosphorus, fast-acting potassium, and effective silicon can be directly absorbed and utilized by plants. Its nutrient elements and heavy metal contents are shown in Tables 2 and 3.

[0029] As shown in Table 2, although the content of nutrients in coal gangue is high, most of them are difficult to be absorbed and utilized by plants. As shown in Table 3, the content of heavy metals such as lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), cadmium (Cd), mercury (Hg), zinc (Zn), and arsenic (As) in raw coal gangue is lower than the risk screening value of the "Soil Environmental Quality-Agricultural Land Soil Pollution Risk Control Standard" (GB 15618-2018). The content of heavy metals in coal gangue calcined at 500-550℃ is significantly reduced (Pb, Cr, Ni, As, Cu, Zn are reduced by 80%, 42%, 62%, 54%, 55%, and 72% respectively). Therefore, by mixing and calcining activated coal gangue, the content of heavy metals can be reduced from the source and the ability of soil to retain water and moisture can be increased.

[0030] Table 1 Main chemical elements of coal gangue

[0031]

[0032] Table 2 Content of nutrient elements in raw coal gangue (mg / kg)

[0033]

[0034] Table 3 Heavy metal content in coal gangue (mg / kg)

[0035]

[0036] Coal gangue contains nutrients such as nitrogen, phosphorus, potassium, and silicon. In order to explore the occurrence forms of various nutrients, X-ray diffraction analysis was carried out on the original coal gangue samples and the calcined coal gangue. The results are shown in Figure 2(a) and Figure 2(b).

[0037] Figure 2(a) shows the main minerals in coal gangue, including quartz, calcite and mullite, and also contains a small amount of orthoclase and Berlinite. Combined with the analysis of the chemical composition of coal gangue, it can be determined that phosphorus exists in the form of orthoclase in coal gangue, while potassium exists in Berlinite, and silicon mainly exists in the form of quartz and mullite. Figure 2(b) shows the main minerals in coal gangue after calcination, including quartz, albite, muscovite and Berlinite.

[0038] Embodiment 1

[0039] The gangue is processed into powder with a particle size of less than 0.5 mm through crushing, grinding and screening processes. The gangue powder is calcined at 500-550℃ for 2.5-3h to obtain calcined activated gangue, which is then mixed with the original gangue powder in a mass ratio of 1:3 and stored for later use. A single Bacillus is taken, inoculated and expanded in an ultra-clean environment, and stored in a refrigerator at 0-4℃ for later use. After the Bacillus is cultured in tryptone soy solid medium for 2 days, the tryptone soy solid medium contains 15 g of soytone, 5 g of trypsin, 5 g of sodium chloride, and 13 g of agar per 1000 mL of distilled water, with a pH of 7.0±0.3, and the culture temperature is controlled at 25-35℃. It is rinsed into a glass bottle with tap water, and the number of bacteria in the suspension is controlled to be 5×10 12 ~10×10 12 cfu·ml -1 , and obtain a suspension of a single bacterial species. Different Bacillus species are compounded to obtain a mixed bacterial agent, and the prepared bacterial agent and coal gangue powder are inoculated and cultured at a solid-liquid ratio of 1:1. The unit of the bacterial agent is ml, and the unit of the mixed coal gangue is g. The temperature is controlled at 25-35℃, and the culture is statically cultured in a constant temperature incubator for 3 days, and then dried in an oven at 50-60℃ to obtain the bacterial dissociated coal gangue. The overall process is as follows: Figure 1 shown.

[0040] In order to verify the effect of Bacillus dissociation on the improvement of coal gangue, the specific test conditions and changes in nutrient elements are shown in Table 4. It shows that after the mixed coal gangue is dissociated by Bacillus, the available phosphorus, alkaline nitrogen, available potassium and available silicon are increased, and the heavy metal content is significantly reduced.

[0041] In this implementation, the optimal bacterial agent is when the strains A1: A2: A3==1:1:1, the contents of effective phosphorus, alkaline nitrogen, quick-acting potassium, and effective silicon are the highest, which are 40.14 mg / kg, 181.67 mg / kg, 452.15 mg / kg, and 430.90 mg / kg, respectively, which are 219.59%, 40.29%, 95.17%, and 38.06% higher than the original gangue control group, and lead, chromium, zinc, copper, nickel, mercury, and arsenic are reduced by 28.26%, 25.86%, 39.83%, 32.27%, 33.39%, 13.73%, and 19.70% respectively compared with the original gangue. This shows that the compound inoculation of Bacillus in gangue is more conducive to the growth of bacteria. Bacillus uses organic and inorganic components in coal gangue as its own nutrients, produces organic acids, induces coal gangue mineralization, produces minerals such as carbonates, sulfates and phosphates, and makes the nutrients in coal gangue easier to dissolve. It can also convert the oxides contained in coal gangue into metal salts that are easily absorbed by plants.

[0042] Table 4 Content of various nutrient elements in coal gangue after dissociation by different fungi (mg / kg)

[0043]

[0044] Embodiment 2

[0045] The gangue was processed into powder with a particle size of less than 0.5 mm through crushing, grinding and screening. The gangue powder was calcined at 500-550℃ for 2.5-3h to obtain calcined activated gangue, which was then mixed with the original gangue powder in a mass ratio of 1:3 and stored for later use. Three types of Bacillus, A1, A2 and A3, were inoculated and expanded in an ultra-clean environment and stored in a refrigerator at 0-4℃ for later use. After the Bacillus was cultured in tryptone soy solid medium for 2 days, the tryptone soy solid medium contained 15 g soytone, 5 g trypsin, 5 g sodium chloride and 13 g agar per 1000 mL of distilled water, with a pH of 7.0±0.3, and the culture temperature was controlled at 25-35℃. The culture was rinsed into the glass bottle with tap water, and the number of bacteria in the suspension was controlled to be 5×10 12 ~10×10 12 cfu·ml -1 , and obtain a suspension of a single bacterial species. According to the conclusion in Example 1, a mixed bacterial agent is prepared according to A1: A2: A3==1:1:1, and the prepared bacterial agent and coal gangue powder are inoculated and cultured at a solid-liquid ratio of 1:1. The unit of the bacterial agent is ml, and the unit of the mixed coal gangue is g. The temperature is controlled at 25-35°C, and the culture is statically cultured in a constant temperature incubator for 1d, 2d, 3d, 4d, and 5d, and then dried in an oven at 50-60°C to obtain bacterially dissociated coal gangue.

[0046] To verify the effect of different dissociation times of composite bacillus on the improvement of coal gangue, the specific test conditions and the results of changes in nutrient elements are shown in Table 5. It is shown that after mixed coal gangue is dissociated with mixed bacillus for 1-7d, available phosphorus, alkaline nitrogen, available potassium, and available silicon are all improved, and the content of heavy metals is significantly reduced. In the present embodiment, the content of effective elements shows a trend of first increasing and then decreasing with the increase of incubation time, and the effect is best on the 4th day. After reaching the peak value, with the increase of incubation time, the content of effective elements in coal gangue is reduced instead. This is because the nutrition required for the reproduction and growth of the strain increases, and the effective elements dissociated are consumed. If the culture time is too long, the bacteria will have entered the decay stage long ago. The presence of a large number of dead bacteria will compete with the coal gangue for nutrients, which will also lead to a decrease in effective elements. When the optimal dissociation time is 4 days, the contents of effective phosphorus, alkaline nitrogen, quick-acting potassium and effective silicon in the improved coal gangue are 42.5 mg / kg, 190.7 mg / kg, 461.7 mg / kg and 433.6 mg / kg, respectively, which are 302.46%, 65.07%, 128.94% and 53.98% higher than those in the original coal gangue control group. The contents of lead, chromium, zinc, copper, nickel, mercury and arsenic are 29.30%, 25.85%, 22.72%, 35.96%, 34.27%, 13.73% and 19.58% lower than those in the original coal gangue, respectively.

[0047] Table 5 Content of various nutrients in coal gangue after dissociation at different times (mg / kg)

[0048] Example

[0049] The gangue was processed into powder with a particle size of less than 0.5 mm through crushing, grinding and screening. The gangue powder was calcined at 500-550℃ for 2.5-3h to obtain calcined activated gangue, which was then mixed with the original gangue powder in a mass ratio of 1:1, 1:2, 1:3, and 1:4 and stored for later use. A single Bacillus was inoculated and expanded in an ultra-clean environment and stored in a refrigerator at 0-4℃ for later use. After the Bacillus was cultured in tryptone soy solid medium for 2 days, the tryptone soy solid medium contained 15 g soytone, 5 g trypsin, 5 g sodium chloride, and 13 g agar per 1000 mL of distilled water, with a pH of 7.0±0.3, and the culture temperature was controlled at 25-35℃. It was rinsed into a glass bottle with tap water, and the number of bacteria in the suspension was controlled to be 5×10 12 ~10×10 12 cfu·ml -1A suspension of a single bacterial species was obtained, and according to the conclusion in Example 1, a mixed bacterial agent was compounded according to A1: A2: A3==1:1:1, and the prepared bacterial agent and coal gangue powder were inoculated and cultured at a solid-liquid ratio of 1:1. The unit of the bacterial agent was ml, and the unit of the mixed coal gangue was g. The temperature was controlled at 25-35°C, and the culture was statically cultured in a constant temperature incubator for 3 days, and then dried in an oven at 50-60°C to obtain bacterially dissociated coal gangue.

[0050] After the static cultivation, the available phosphorus, alkaline nitrogen, available potassium and available silicon in the improved coal gangue increased by 204.36%-259.19%, 31.28%-50.97%, 84.53%-107.89% and 35.26%-78.55%, respectively, while lead, chromium, zinc, copper, nickel, mercury and arsenic decreased by 28.1%-46.0%, 22.5%-37.4%, 1.2%-32.3%, 24.3%-55.5, 22.0%-45.1%, 5.9%-19.6% and 16.4%-30.7%, respectively, compared with the original coal gangue. When the optimal mixing mass ratio of calcined activated coal gangue to raw coal gangue powder is 1:3, the amount of calcined coal gangue is less, the energy consumption is appropriate, and the content of nutrient elements in the improved coal gangue is higher and the content of heavy metals meets the standards.

[0051] Comparative Example 1

[0052] The gangue is processed into powder with a particle size of less than 0.5 mm through crushing, grinding and screening processes, and the gangue powder is calcined at 500-550°C for 2.5-3h to obtain calcined activated gangue, which is then mixed with the original gangue powder at a mass ratio of 1:5 and stored for later use; tap water and mixed gangue powder are mixed at a solid-liquid ratio of 2:1, 1:1, and 1:2, the unit of tap water is ml, and the unit of mixed gangue is g, the temperature is controlled at 25-35°C, the humidity is controlled at 35-55%, and it is left to stand for 4 days. Then it is dried in an oven at 50-60°C to obtain bacterially dissociated gangue. After the static culture, the available phosphorus, alkaline nitrogen, available potassium and available silicon in the gangue increased by 5.7%-12.6%, 3.3%-5.2%, 1.0%-7.8% and 1.0%-2.5% respectively compared with the mixed gangue before static culture.

[0053] It shows that after the static culture of mixed coal gangue in a humid environment, without the action of Bacillus and with a low proportion of calcined coal gangue, the contents of lead, chromium, zinc, copper, nickel, mercury and arsenic in the mixed coal gangue not only did not decrease compared with before static culture, but increased to varying degrees, increasing by 0.9%-3.3%, 0.9%-3.1%, 0.4%-1.4%, 1.3%-3.1%, 0.3%-2.1%, 2.4%-4.4% and 1.1%-3.8% respectively.

[0054] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for dissociating nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-like bacterial agent, characterized in that: The method comprises the following steps: a. Pretreatment of coal gangue: crush, grind and screen the coal gangue into powder; calcine the coal gangue powder at 500-550°C for 2h-3h to obtain calcined activated coal gangue, mix the calcined activated coal gangue with the original coal gangue after grinding in a mass ratio of 1:1-1:4, and store for later use; b. Compounding to obtain a mixed bacillus inoculant: selecting Bacillus megaterium ACCC03031, Bacillus mucilaginosus ACCC19749, and Bacillus subtilis ACCC 19743 from the China Agricultural Microbiological Culture Collection Center, and naming them A1, A2, and A3 respectively, inoculating slant seeds stored at 0-4° C. into a solid culture medium for cultivation, rinsing the cultured bacillus into a triangular flask, adjusting the bacterial content of the bacterial solution and the pH value of the bacterial solution with tap water to obtain a suspension of a single bacterial species, and mixing the suspensions of A1, A2, and A3 at a volume ratio of (1.0-2.5):(1.0-2.0):1 to obtain a mixed bacterial solution; c. Dissociating mixed coal gangue with mixed Bacillus: inoculating the mixed bacterial agent obtained in step b into the mixed coal gangue powder obtained in step a for fermentation and cultivation, and then drying to obtain improved coal gangue.

2. The method for decomposing the nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-like bacterial agent according to claim 1, characterized in that: In step a, the coal gangue is processed into powder with a particle size of ≤0.5 mm.

3. The method for decomposing the nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-like bacterial agent according to claim 1, characterized in that: In step b, a tryptone soy solid culture medium is used, wherein each 1000 mL of distilled water contains 10-20 g of soytone, 3-9 g of trypsin, 3-10 g of sodium chloride, and 15-45 g of agar. After heating and dissolving, and adjusting the pH value to 7.0-7.4, the culture medium is divided into containers and sterilized in an autoclave at 121°C for 20-30 min. The bacteria inoculated in the solid culture medium are then cultured at 25-30°C for 2-3 days.

4. The method for decomposing the nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-like bacterial agent according to claim 1, characterized in that: In step b, the bacterial count in the suspension of the single bacterial species is 5×10 11 ~ 10×10 13 cfu·ml -1 , adjust the pH value of the bacterial solution to 6-9 with 1 mol / L dilute H2SO4 solution and 1 mol / L dilute HCl solution.

5. The method for decomposing nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-like bacterial agent according to claim 1, characterized in that: In step c, the mixed bacterial agent and the mixed coal gangue are mixed according to a solid-liquid ratio of 1:2-2:1, wherein the unit of the mixed bacterial agent is ml, and the unit of the mixed coal gangue is g.

6. The method for decomposing nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-like bacterial agent according to claim 1, characterized in that: In step c, during the fermentation culture, ventilation and oxygen supply are performed, the temperature is controlled at 25-35° C., the humidity is controlled at 35-55%, and the culture is statically cultured for 1-7 days.

7. The method for decomposing the nutrient components in coal gangue and controlling harmful heavy metals by using a Bacillus-like bacterial agent according to claim 1, characterized in that: In step c, the drying temperature is 50-60° C., and the moisture content of the improved coal gangue is ≤3.0%.

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