Soil ecological restoration agent based on coal gangue-fly ash and preparation method thereof

Abstract

The invention relates to the technical field of soil remediation, in particular to a soil ecological remediation agent based on coal gangue-fly ash and a preparation method of the soil ecological remediation agent. The soil ecological restoration agent comprises the following components in parts by weight: 40-50 parts of coal gangue-fly ash mixed powder, 6-12 parts of a microbial agent, 15-20 parts of humic acid, 6-12 parts of sodium polyacrylate, 8-12 parts of straw carbon, 20-25 parts of bentonite and 4-6 parts of aluminum sulfate. The soil ecological restoration agent can supplement trace elements into soil, meanwhile, the coal gangue-fly ash can adsorb heavy metals in the soil so as to fix the heavy metals, the microbial agent can be loaded on the surface of the coal gangue-fly ash, the heavy metals adsorbed on the coal gangue-fly ash are precipitated through the microbial agent, and the heavy metals adsorbed on the coal gangue-fly ash can be fixed. The concentration of heavy metal ions in the soil is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a soil ecological remediation agent based on coal gangue-fly ash and a preparation method thereof. Background Art

[0002] Gangue is a typical solid waste generated during coal mining and dressing. It generally has a low carbon content and a high ash content. Long-term open-air storage of gangue can cause air pollution and other problems. While some disposal and utilization methods are being explored, such as combustion for power generation, production of building materials and ceramics, and extraction of valuable metals, no truly low-cost, large-scale disposal technology for gangue has yet been established.

[0003] In recent years, a disposal technology using coal gangue for ecological restoration has emerged. However, the capillary porosity of coal gangue is low and cannot effectively improve the water retention capacity of the soil. At the same time, coal gangue generally contains heavy metals (such as Pb, Cd, As, Hg, etc.). Directly adding these coal gangue to the soil will lead to an increase in the heavy metal content in the soil, thus limiting the application of coal gangue in the field of ecological restoration. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a soil ecological restoration agent based on coal gangue-fly ash and a preparation method thereof.

[0005] The technical solution of the present invention is: a soil ecological restoration agent based on coal gangue and fly ash, which includes the following components by weight: 40 to 50 parts of coal gangue and fly ash mixed powder, 6 to 12 parts of microbial agent, 15 to 20 parts of humic acid, 6 to 12 parts of sodium polyacrylate, 8 to 12 parts of straw charcoal, 20 to 25 parts of bentonite, and 4 to 6 parts of aluminum sulfate.

[0006] Description: The above-mentioned soil ecological restoration agent is combined with coal gangue and fly ash to supplement trace elements into the soil. At the same time, coal gangue-fly ash can adsorb heavy metals in the soil to fix the heavy metals, and microbial agents can be loaded on the surface of coal gangue-fly ash. The heavy metals adsorbed on the coal gangue-fly ash are precipitated by the microbial agents to reduce the concentration of heavy metal ions in the soil.

[0007] Furthermore, the preparation method of the gangue-fly ash mixed powder comprises the following steps:

[0008] S1. crushing the gangue into a gangue powder with a particle size of ≤100 mesh, then calcining the gangue powder at 700-800° C. for two hours, and activating the gangue powder after the calcination to obtain activated gangue powder;

[0009] S2. Add the activated gangue powder to deionized water and ultrasonically disperse it for 15 to 20 minutes to obtain a dispersion system. Then, add acrylic acid to the dispersion system, heat it to 60 to 80° C., keep it warm for 2 to 4 hours, and then filter it to obtain gangue powder loaded with acrylic acid. The mass ratio of the activated gangue powder, acrylic acid, and deionized water is 1:0.3 to 0.4:3 to 5.

[0010] S3. activating fly ash, adding the activated fly ash and carboxymethyl urea to deionized water to obtain a mixed solution, adjusting the pH value of the mixed solution to 10-12 using a sodium hydroxide solution having a mass concentration of 10-15%, and then heating the mixed solution to 50-60° C. and keeping the temperature for 1-3 hours to obtain fly ash loaded with carboxymethyl urea; wherein the mass ratio of the activated fly ash, carboxymethyl urea, and deionized water is 1:0.2-0.4:3-5;

[0011] S4. Fully mixing the acrylic acid-loaded coal gangue powder and the carboxymethyl urea-loaded fly ash to obtain a mixed powder, adding the mixed powder into room temperature deionized water, and ultrasonically dispersing the mixture for 15 to 20 minutes to obtain a dispersion; the mass ratio of the acrylic acid-loaded coal gangue powder, the carboxymethyl urea-loaded fly ash, and the deionized water is 1:1.2 to 1.6:4 to 6;

[0012] S5. Heat the dispersion, and add potassium persulfate to the dispersion every time the temperature of the dispersion increases by 10-15° C. during the heating process until the temperature of the dispersion reaches 70-80° C., add epichlorohydrin to the dispersion, and then keep the dispersion warm for 2-4 hours under stirring. After the insulation is completed, filter and wash to obtain a gangue-fly ash mixed powder; wherein the single addition amount of potassium persulfate accounts for 0.2-0.4% of the total mass of the dispersion, and the addition amount of epichlorohydrin accounts for 1-3% of the total mass of the dispersion.

[0013] Description: The above method activates coal gangue powder and fly ash, then loads acrylic acid on the coal gangue powder and loads carboxymethyl urea on the fly ash. Through copolymerization of acrylic acid and carboxymethyl urea, the coal gangue powder and fly ash are combined to form a mixed powder, thereby improving the adsorption properties of the coal gangue powder and fly ash, so that the coal gangue-fly ash mixed powder can effectively fix heavy metal ions and improve the water retention capacity of the soil.

[0014] Furthermore, in step S1, the activation method of the coal gangue powder is: adding the calcined coal gangue powder to an ethanol solution with a mass concentration of 40-60%, then adding a silane coupling agent to the ethanol solution and heating the ethanol solution to 60-70°C, stirring for 1-2 hours and then filtering to obtain activated coal gangue powder, wherein the mass ratio of the calcined coal gangue powder, the silane coupling agent and the ethanol solution is 1:0.1-0.2:3-4.

[0015] Note: The above steps activate the gangue powder through the silane coupling agent, which increases the number of organic functional groups on the surface of the gangue powder. These organic functional groups can form covalent bonds with acrylic acid, thereby improving the loading stability of acrylic acid.

[0016] Furthermore, in step S3, the fly ash activation method is: adding the fly ash to a sodium hydroxide solution with a mass concentration of 4-8%, then heating the sodium hydroxide solution to 70-80°C, keeping it warm for 30-40 minutes and then filtering to obtain activated fly ash, wherein the mass ratio of fly ash to sodium hydroxide solution is 1:2-3.

[0017] Note: The above steps activate the fly ash by sodium hydroxide, thereby increasing the active sites on the fly ash surface and making it easier for the fly ash to load carboxymethyl urea.

[0018] Furthermore, in step S4, the mixing method is: using a ball mill to mix the coal gangue powder loaded with acrylic acid and the fly ash loaded with carboxymethyl urea, the mixing time is 20 to 30 minutes, and the ball-to-material ratio is 1 to 3:1.

[0019] Description: The coal gangue powder loaded with acrylic acid and the fly ash loaded with carboxymethyl urea can be fully mixed by a ball mill to ensure the uniformity of the mixed powder.

[0020] Furthermore, the components of the microbial agent include, by weight, 1 to 3 parts of Bacillus licheniformis, 2 to 4 parts of Pseudomonas aeruginosa, 2 to 3 parts of Sphingomonas, and 1 to 2 parts of Aspergillus niger.

[0021] Description: The above-mentioned microbial agent can be loaded on the coal gangue-fly ash mixed powder, and cooperate with the coal gangue-fly ash mixed powder to effectively chelate heavy metals in the soil and reduce the concentration of heavy metal ions in the soil.

[0022] On the other hand, the present invention also provides a method for preparing a soil ecological restoration agent based on coal gangue-fly ash, comprising the following steps:

[0023] 1) adding the gangue-fly ash mixed powder, humic acid, sodium polyacrylate, straw charcoal and bentonite into a mixer according to the weight parts, stirring for 10 to 20 minutes, adding the microbial agent and aluminum sulfate into the mixer, and continuing to stir for 20 to 30 minutes to obtain a mixture;

[0024] 2) adding water at 20-30° C. to the mixture, stirring for 10-15 minutes, and using a granulator to form the mixture into particles with a particle size of 2-5 mm to obtain a soil ecological restoration agent; wherein the amount of water added accounts for 20-30% of the total mass of the mixture.

[0025] Description: The above preparation method is to granulate the coal gangue-fly ash mixed powder with other ingredients, so that the soil ecological restoration agent has better adsorption performance, and the sodium polyacrylate can be slowly dissolved, so that the microbial agent is slowly released into the soil, thereby improving the heavy metal removal rate in the soil.

[0026] The beneficial effects of the present invention are:

[0027] (1) The soil ecological restoration agent of the present invention can supplement trace elements into the soil. At the same time, the gangue-fly ash can adsorb heavy metals in the soil to fix the heavy metals. The microbial agent can be loaded on the surface of the gangue-fly ash. The microbial agent precipitates the heavy metals adsorbed on the gangue-fly ash to reduce the concentration of heavy metal ions in the soil.

[0028] (2) The preparation method of the present invention is to granulate the coal gangue-fly ash mixed powder with other ingredients, so that the soil ecological restoration agent has better adsorption performance, and the sodium polyacrylate can be slowly dissolved, so that the microbial agent is slowly released into the soil, thereby improving the heavy metal removal rate in the soil. DETAILED DESCRIPTION

[0029] In order to further illustrate the approach and effects achieved by the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with experiments.

[0030] Example 1: A soil ecological restoration agent based on coal gangue-fly ash, comprising the following ingredients, by weight: 45 parts of coal gangue-fly ash mixed powder, 9 parts of microbial agent, 18 parts of humic acid, 9 parts of sodium polyacrylate, 10 parts of straw charcoal, 22 parts of bentonite, and 5 parts of aluminum sulfate;

[0031] The preparation method of coal gangue-fly ash mixed powder comprises the following steps:

[0032] S1. crushing the gangue into a gangue powder with a particle size of ≤100 mesh, then calcining the gangue powder at 750° C. for two hours, and activating the gangue powder after the calcination to obtain activated gangue powder;

[0033] The activation method of the coal gangue powder comprises: adding the calcined coal gangue powder to an ethanol solution with a mass concentration of 50%, then adding a silane coupling agent to the ethanol solution, heating the ethanol solution to 65° C., stirring for 1.5 hours, and filtering to obtain activated coal gangue powder, wherein the mass ratio of the calcined coal gangue powder, the silane coupling agent, and the ethanol solution is 1:0.15:3.5;

[0034] S2. Add the activated gangue powder to deionized water and ultrasonically disperse for 18 minutes to obtain a dispersion system. Then, add acrylic acid to the dispersion system, heat it to 70°C, keep it warm for 3 hours, and filter it to obtain acrylic acid-loaded gangue powder; wherein the mass ratio of the activated gangue powder, acrylic acid, and deionized water is 1:0.35:4;

[0035] S3. activating fly ash, adding the activated fly ash and carboxymethyl urea to deionized water to obtain a mixed solution, adjusting the pH value of the mixed solution to 11 with a 12% sodium hydroxide solution, and then heating the mixed solution to 55° C. and keeping the temperature for 2 hours to obtain fly ash loaded with carboxymethyl urea; wherein the mass ratio of the activated fly ash, carboxymethyl urea, and deionized water is 1:0.3:4;

[0036] The fly ash activation method comprises: adding the fly ash into a sodium hydroxide solution with a mass concentration of 6%, then heating the sodium hydroxide solution to 75° C., keeping the temperature for 35 minutes, and then filtering to obtain activated fly ash, wherein the mass ratio of the fly ash to the sodium hydroxide solution is 1:2.5;

[0037] S4. Fully mixing the acrylic acid-loaded coal gangue powder and the carboxymethyl urea-loaded fly ash to obtain a mixed powder, adding the mixed powder into room temperature deionized water and ultrasonically dispersing the mixture for 18 minutes to obtain a dispersion; the mass ratio of the acrylic acid-loaded coal gangue powder, the carboxymethyl urea-loaded fly ash, and the deionized water is 1:1.4:5;

[0038] The mixing method comprises: using a ball mill to mix the coal gangue powder loaded with acrylic acid and the fly ash loaded with carboxymethyl urea, with a mixing time of 25 minutes and a ball-to-material ratio of 2:1;

[0039] S5. Heating the dispersion, adding potassium persulfate to the dispersion once every time the temperature of the dispersion increases by 12° C. during the heating process until the temperature of the dispersion reaches 75° C., adding epichlorohydrin to the dispersion, and then keeping the dispersion warm for 3 hours under stirring. After the insulation is completed, filtering and washing to obtain a gangue-fly ash mixed powder; wherein the single addition amount of potassium persulfate accounts for 0.3% of the total mass of the dispersion, and the addition amount of epichlorohydrin accounts for 2% of the total mass of the dispersion;

[0040] The components of the microbial agent include, by weight, 2 parts of Bacillus licheniformis, 3 parts of Pseudomonas aeruginosa, 2.5 parts of Sphingomonas, and 1.5 parts of Aspergillus niger; wherein the Bacillus licheniformis has a preservation number of CICC 10087, the Pseudomonas aeruginosa has a preservation number of CICC 10204, the Sphingomonas has a preservation number of CICC 24503, and the Aspergillus niger has a preservation number of CICC 40273; the purchased strains are cultured in a culture medium until the logarithmic phase, centrifuged, and freeze-dried to obtain strains, and the strains are mixed in proportion to obtain the microbial agent;

[0041] The preparation method of the soil ecological restoration agent comprises the following steps:

[0042] 1) adding the gangue-fly ash mixed powder, humic acid, sodium polyacrylate, straw charcoal and bentonite into a mixer according to the weight parts, stirring for 15 minutes, then adding the microbial agent and aluminum sulfate into the mixer, and continuing to stir for 25 minutes to obtain a mixture;

[0043] 2) adding water at 25° C. to the mixture, stirring for 12 minutes, and using a granulator to form the mixture into particles with a particle size of 2 to 5 mm to obtain a soil ecological restoration agent; wherein the amount of water added accounts for 25% of the total mass of the mixture.

[0044] Example 2: This example is basically the same as Example 1, except that the soil ecological restoration agent comprises the following ingredients, by weight: 40 parts of coal gangue-fly ash mixed powder, 6 parts of microbial agent, 15 parts of humic acid, 6 parts of sodium polyacrylate, 8 parts of straw charcoal, 20 parts of bentonite, and 4 parts of aluminum sulfate;

[0045] The components of the microbial agent include, by weight, 1 part of Bacillus licheniformis, 2 parts of Pseudomonas aeruginosa, 2 parts of Sphingomonas, and 1 part of Aspergillus niger.

[0046] Example 3: This example is basically the same as Example 1, except that the soil ecological restoration agent comprises the following ingredients, by weight: 50 parts of coal gangue-fly ash mixed powder, 12 parts of microbial agent, 20 parts of humic acid, 12 parts of sodium polyacrylate, 12 parts of straw charcoal, 25 parts of bentonite, and 6 parts of aluminum sulfate;

[0047] The components of the microbial agent include, by weight, 3 parts of Bacillus licheniformis, 4 parts of Pseudomonas aeruginosa, 3 parts of Sphingomonas, and 2 parts of Aspergillus niger.

[0048] Example 4: This example is basically the same as Example 1, except that the mass ratio of the calcined gangue powder, the silane coupling agent and the ethanol solution is 1:0.1:3.

[0049] Example 5: This example is basically the same as Example 1, except that the mass ratio of the calcined gangue powder, the silane coupling agent and the ethanol solution is 1:0.2:4.

[0050] Example 6: This example is basically the same as Example 1, except that the mass ratio of activated gangue powder, acrylic acid and deionized water is 1:0.3:3.

[0051] Example 7: This example is basically the same as Example 1, except that the mass ratio of activated gangue powder, acrylic acid and deionized water is 1:0.4:5.

[0052] Example 8: This example is basically the same as Example 1, except that the mass ratio of activated fly ash, carboxymethyl urea and deionized water is 1:0.2:3.

[0053] Example 9: This example is basically the same as Example 1, except that the mass ratio of activated fly ash, carboxymethyl urea and deionized water is 1:0.4:5.

[0054] Example 10: This example is basically the same as Example 1, except that the mass ratio of fly ash to sodium hydroxide solution is 1:2.

[0055] Example 11: This example is basically the same as Example 1, except that the mass ratio of fly ash to sodium hydroxide solution is 1:3.

[0056] Example 12: This example is basically the same as Example 1, except that the mass ratio of the acrylic acid-loaded coal gangue powder, the carboxymethyl urea-loaded fly ash, and deionized water is 1:1.2:4.

[0057] Example 13: This example is basically the same as Example 1, except that the mass ratio of the acrylic acid-loaded coal gangue powder, the carboxymethyl urea-loaded fly ash, and deionized water is 1:1.6:6.

[0058] Example 14: This example is basically the same as Example 1, except that potassium persulfate is added to the dispersion once every time the dispersion temperature rises by 10°C during the heating process.

[0059] Example 15: This example is basically the same as Example 1, except that potassium persulfate is added to the dispersion once every time the dispersion temperature rises by 15°C during the heating process.

[0060] Example 16: This example is basically the same as Example 1, except that the single addition amount of potassium persulfate accounts for 0.2% of the total mass of the dispersion.

[0061] Example 17: This example is basically the same as Example 1, except that the single addition amount of potassium persulfate accounts for 0.4% of the total mass of the dispersion.

[0062] Example 18: This example is basically the same as Example 1, except that the amount of water added accounts for 20% of the total mass of the mixture.

[0063] Example 19: This example is basically the same as Example 1, except that the amount of water added accounts for 30% of the total mass of the mixture.

[0064] Comparative Example 1: This embodiment is basically the same as Example 1, except that the gangue powder and fly ash are not subjected to any treatment and are directly added to the soil ecological restoration agent.

[0065] Comparative Example 2: This embodiment is basically the same as Example 1, except that acrylic acid is not loaded onto the gangue powder and carboxymethyl urea is not loaded onto the fly ash.

[0066] Comparative Example 3: This example is basically the same as Example 1, except that potassium persulfate is added to the dispersion all at once.

[0067] Experimental Example: In order to explore the soil remediation effect of the soil ecological remediation agent prepared in each embodiment on the soil, 24 equal parts of heavy metal contaminated soil were taken from the same area as experimental soil, and the soil ecological remediation agent prepared in each embodiment and comparative example was added to each experimental soil at an addition amount of 5% and mixed evenly. Subsequently, water was sprayed into each experimental soil to make the soil moisture content reach 20%. The soil was left to stand for 60 days to complete the remediation. The heavy metal content of the soil before and after remediation was tested, and the reduction rate of the heavy metal content in the experimental soil before and after remediation was obtained by calculation. The specific exploration is as follows:

[0068] Experimental Example 1: Exploring the influence of soil ecological restoration agent components on restoration effects

[0069] Using Examples 1 to 3 and Comparative Example 1 as experimental comparisons, the heavy metal content reduction rates obtained under soil ecological restoration agents with different components are shown in Table 1 below:

[0070] Table 1 Reduction rate of heavy metal content under different components of soil ecological restoration agents

[0071] Group Cd Hg As Pb Example 1 97.24％ 95.51％ 95.37％ 96.89％ Example 2 96.33％ 94.43％ 95.05％ 95.11％ Example 3 96.08％ 94.25％ 94.79％ 95.23％ Comparative Example 1 90.47％ 88.85％ 87.53％ 89.67％

[0072] As can be seen from the data in Table 1, compared with Examples 1, 2, and 3, Example 1 has the highest reduction rate of heavy metal content, indicating that the soil ecological restoration agent of Example 1 has the best restoration effect on heavy metal contaminated soil. Therefore, the soil ecological restoration agent composition selected in Example 1 is optimal.

[0073] Compared with Comparative Example 1, Example 1 shows that without any treatment of the gangue powder and fly ash, the reduction rate of heavy metal content is significantly reduced. This may be because without any treatment of the gangue powder and fly ash, the gangue powder and fly ash fail to effectively adsorb heavy metal ions. Therefore, the soil ecological restoration agent component selected in Example 1 is optimal.

[0074] Experimental Example 2: Investigating the influence of preparation parameters of acrylic acid-loaded gangue powder on the repair effect

[0075] Using Examples 1 and 4 to 7 as experimental comparisons, the heavy metal content reduction rates of the acrylic acid-loaded gangue powder under different preparation parameters are shown in Table 2 below:

[0076] Table 2 Reduction rate of heavy metal content in acrylic acid-loaded coal gangue powder under different preparation parameters

[0077]

[0078]

[0079] It can be seen from the data in Table 2 that compared with Examples 1, 4, 5, 6, and 7, Example 1 has the highest reduction rate of heavy metal content, indicating that the soil ecological remediation agent of Example 1 has the best remediation effect on heavy metal contaminated soil. This may be because the surface of the coal gangue powder can fully load acrylic acid under the preparation parameters of Example 1, so the preparation parameters of the coal gangue powder loaded with acrylic acid selected in Example 1 are optimal.

[0080] Experimental Example 3: Investigating the influence of preparation parameters of fly ash loaded with carboxymethyl urea on the repair effect

[0081] Using Examples 1 and 8 to 11 as experimental comparisons, the heavy metal content reduction rates of the fly ash loaded with carboxymethyl urea under different preparation parameters are shown in Table 3 below:

[0082] Table 3 Reduction rate of heavy metal content in fly ash loaded with carboxymethyl urea under different preparation parameters

[0083] Group Cd Hg As Pb Example 1 97.24％ 95.51％ 95.37％ 96.89％ Example 8 95.33％ 94.17％ 94.68％ 96.12％ Example 9 95.52％ 94.27％ 94.82％ 95.93％ Example 10 96.16％ 94.42％ 95.14％ 96.22％ Example 11 95.44％ 94.10％ 94.95％ 95.88％

[0084] It can be seen from the data in Table 3 that compared with Examples 1, 8, 9, 10, and 11, the heavy metal content reduction rate of Example 1 is the highest, indicating that the soil ecological remediation agent of Example 1 has the best remediation effect on heavy metal contaminated soil. This may be because the fly ash surface can fully load carboxylmethyl urea under the preparation parameters of Example 1, so the preparation parameters of the fly ash loaded with carboxylmethyl urea selected in Example 1 are optimal.

[0085] Experimental Example 4: Investigating the influence of preparation parameters of coal gangue-fly ash mixed powder on the repair effect

[0086] Using Examples 1, 12 to 17 and Comparative Examples 2 to 3 as experimental comparisons, the heavy metal content reduction rates of the gangue-fly ash mixed powder under different preparation parameters are shown in Table 4 below:

[0087] Table 4 Reduction rate of heavy metal content in coal gangue-fly ash mixed powder under different preparation parameters

[0088]

[0089]

[0090] As can be seen from the data in Table 4, compared with Examples 1, 12, and 13, Example 1 has the highest reduction rate of heavy metal content, indicating that the soil ecological restoration agent of Example 1 has the best restoration effect on heavy metal contaminated soil. This may be because the coal gangue powder loaded with acrylic acid and the fly ash loaded with carboxymethyl urea can be stably combined under the dispersion ratio of Example 1, so the dispersion ratio selected in Example 1 is optimal;

[0091] Comparing Examples 1, 14, 15, 16, and 17: Example 1 has the highest reduction rate of heavy metal content, indicating that the soil ecological restoration agent of Example 1 has the best restoration effect on heavy metal contaminated soil. This may be because the acrylic acid loaded on the gangue powder can fully react with the carboxymethyl urea loaded on the fly ash under the potassium persulfate addition frequency and addition amount of Example 1. Therefore, the potassium persulfate addition frequency and addition amount selected in Example 1 are both optimal;

[0092] Compared with Comparative Example 2, Example 1 shows that the heavy metal content reduction rate is significantly reduced after neither acrylic acid is loaded on the gangue powder nor carboxymethyl urea is loaded on the fly ash. This may be because the gangue powder and fly ash cannot play a synergistic role, resulting in a decrease in the adsorption rate of heavy metals. Therefore, the gangue-fly ash mixed powder preparation method selected in Example 1 is the best.

[0093] Compared with Comparative Example 3, Example 1 shows that after potassium persulfate was added to the dispersion all at once, the reduction rate of heavy metal content decreased. This may be because the one-time addition of potassium persulfate resulted in insufficient combination of coal gangue powder and fly ash. Therefore, the potassium persulfate addition method selected in Example 1 is optimal.

[0094] Experimental Example 5: Investigating the effect of water addition on the repair effect

[0095] Using Examples 1 and 18-19 as experimental comparisons, the heavy metal content reduction rates obtained under different water addition amounts are shown in Table 5 below:

[0096] Table 5 Reduction rate of heavy metal content under different water addition amounts

[0097] Group Cd Hg As Pb Example 1 97.24％ 95.51％ 95.37％ 96.89％ Example 18 96.78％ 95.13％ 95.09％ 96.24％ Example 19 96.85％ 95.11％ 95.21％ 96.43％

[0098] It can be seen from the data in Table 5 that compared with Examples 1, 18 and 19, the heavy metal content reduction rate of Example 1 is the highest, indicating that the soil ecological remediation agent of Example 1 has the best remediation effect on heavy metal contaminated soil. This may be because the pores of the soil ecological remediation agent particles are the most uniform under the water addition amount of Example 1, so the water addition amount selected in Example 1 is the best.

Claims

1. A soil ecological restoration agent based on coal gangue-fly ash, characterized in that: The composition includes the following ingredients by weight: 40-50 parts of coal gangue-fly ash mixed powder, 6-12 parts of microbial agent, 15-20 parts of humic acid, 6-12 parts of sodium polyacrylate, 8-12 parts of straw charcoal, 20-25 parts of bentonite and 4-6 parts of aluminum sulfate.

2. The soil ecological restoration agent based on coal gangue-fly ash according to claim 1, characterized in that: The preparation method of coal gangue-fly ash mixed powder comprises the following steps: S1. crushing the gangue into a gangue powder with a particle size of ≤100 mesh, then calcining the gangue powder at 700-800° C. for two hours, and activating the gangue powder after the calcination to obtain activated gangue powder; S2. Add the activated gangue powder to deionized water and ultrasonically disperse it for 15 to 20 minutes to obtain a dispersion system. Then, add acrylic acid to the dispersion system, heat it to 60 to 80° C., keep it warm for 2 to 4 hours, and then filter it to obtain gangue powder loaded with acrylic acid. The mass ratio of the activated gangue powder, acrylic acid, and deionized water is 1:0.3 to 0.4:3 to 5. S3. activating fly ash, adding the activated fly ash and carboxymethyl urea to deionized water to obtain a mixed solution, adjusting the pH value of the mixed solution to 10-12 using a sodium hydroxide solution having a mass concentration of 10-15%, and then heating the mixed solution to 50-60° C. and keeping the temperature for 1-3 hours to obtain fly ash loaded with carboxymethyl urea; wherein the mass ratio of the activated fly ash, carboxymethyl urea, and deionized water is 1:0.2-0.4:3-5; S4. Fully mixing the acrylic acid-loaded coal gangue powder and the carboxymethyl urea-loaded fly ash to obtain a mixed powder, adding the mixed powder into room temperature deionized water, and ultrasonically dispersing the mixture for 15 to 20 minutes to obtain a dispersion; the mass ratio of the acrylic acid-loaded coal gangue powder, the carboxymethyl urea-loaded fly ash, and the deionized water is 1:1.2 to 1.6:4 to 6; S5. Heat the dispersion, and add potassium persulfate to the dispersion every time the temperature of the dispersion increases by 10-15° C. during the heating process until the temperature of the dispersion reaches 70-80° C., add epichlorohydrin to the dispersion, and then keep the dispersion warm for 2-4 hours under stirring. After the insulation is completed, filter and wash to obtain a gangue-fly ash mixed powder; wherein the single addition amount of potassium persulfate accounts for 0.2-0.4% of the total mass of the dispersion, and the addition amount of epichlorohydrin accounts for 1-3% of the total mass of the dispersion.

3. The soil ecological restoration agent based on coal gangue-fly ash according to claim 2, characterized in that: In step S1, the activation method of the coal gangue powder is: adding the calcined coal gangue powder to an ethanol solution with a mass concentration of 40-60%, then adding a silane coupling agent to the ethanol solution and heating the ethanol solution to 60-70°C, stirring for 1-2 hours and filtering to obtain activated coal gangue powder, wherein the mass ratio of the calcined coal gangue powder, the silane coupling agent and the ethanol solution is 1:0.1-0.2:3-4.

4. The soil ecological restoration agent based on coal gangue-fly ash according to claim 2, characterized in that: In step S3, the fly ash activation method is: adding the fly ash to a sodium hydroxide solution with a mass concentration of 4-8%, then heating the sodium hydroxide solution to 70-80°C, keeping it warm for 30-40 minutes and filtering it to obtain activated fly ash, wherein the mass ratio of fly ash to sodium hydroxide solution is 1:2-3.

5. The soil ecological restoration agent based on coal gangue-fly ash according to claim 2, characterized in that: In step S4, the mixing method is: using a ball mill to mix the coal gangue powder loaded with acrylic acid and the fly ash loaded with carboxymethyl urea, the mixing time is 20 to 30 minutes, and the ball-to-material ratio is 1 to 3:

1.

6. The soil ecological restoration agent based on coal gangue-fly ash according to claim 1, characterized in that: The components of the microbial agent include, by weight, 1 to 3 parts of Bacillus licheniformis, 2 to 4 parts of Pseudomonas aeruginosa, 2 to 3 parts of Sphingomonas, and 1 to 2 parts of Aspergillus niger.

7. The method for preparing a soil ecological restoration agent based on coal gangue-fly ash according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) adding the gangue-fly ash mixed powder, humic acid, sodium polyacrylate, straw charcoal and bentonite into a mixer according to the weight parts, stirring for 10 to 20 minutes, adding the microbial agent and aluminum sulfate into the mixer, and continuing to stir for 20 to 30 minutes to obtain a mixture; 2) adding water at 20-30° C. to the mixture, stirring for 10-15 minutes, and using a granulator to form the mixture into particles with a particle size of 2-5 mm to obtain a soil ecological restoration agent; wherein the amount of water added accounts for 20-30% of the total mass of the mixture.

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