An ecological restoration and water retention technology for coal gangue abandoned mine

Abstract

The application discloses a coal gangue abandoned mine ecological restoration water conservation technology and belongs to the technical field of environmental protection.The restoration technology is characterized in that after the surface soil of the mine is loosened, alkaline waste and heavy metal adsorbents are first added for neutralization and adsorption pretreatment, and then a composite soil conditioner is continuously added to construct an improved composite layer soil in turn in a gradient mode, wherein the composite soil conditioner comprises fly ash, steel slag, local clay, straw fiber, water-retaining slow-release microcapsules, biochar, papermaking white mud and humus soil; high-resistance vegetation is transplanted on the obtained improved composite layer soil, and microbial inoculants are inoculated at the same time; and the restoration is completed after maintenance until stability is achieved.The application integrates multiple technical processes and matches and cooperates with each other, and through a multiple restoration mechanism of materials-vegetation-microorganisms, the multiple restoration mechanism jointly acts to finally achieve the purpose of long-acting water conservation, and compared with traditional mine restoration technologies, the application has better stability, is more long-acting and persistent, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to a water conservation technology for ecological restoration of abandoned coal gangue mines. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. Due to its low utilization rate, this coal gangue accumulates and eventually forms abandoned mines, which not only occupy a large amount of land resources, but also cause serious pollution and damage to the ecological environment.

[0003] Ecological restoration of abandoned coal gangue mines faces numerous challenges, with poor water retention being a key issue. Coal gangue itself has a loose structure and large pores, lacking the water and fertilizer retention capacity of soil, making vegetation growth difficult and further exacerbating soil erosion and ecological degradation. Traditional mine restoration techniques for abandoned coal gangue mines have limitations. For example, simple vegetation cover cannot fundamentally solve the problem of rapid water loss; although efforts have been made to select acid-resistant and drought-resistant plant species adapted to the coal gangue mine environment, their growth still faces challenges. The special properties of coal gangue, such as high acidity, low fertility, and unstable structure, result in slow vegetation growth and low survival rates, hindering effective restoration. Simply introducing microorganisms has limited effect on mine restoration. Furthermore, due to the poor stability of coal gangue soil, the harsh environment, such as high acidity and high concentrations of heavy metals, inhibits the survival and reproduction of microorganisms. External environmental factors in the mine also disrupt the microbial community structure.

[0004] Therefore, it is of great significance to develop an efficient, environmentally friendly and economical ecological restoration water conservation technology for abandoned coal gangue mines that can improve their long-term water and fertilizer retention capacity. Summary of the Invention

[0005] In response to the problems mentioned in the background art, the purpose of this invention is to provide an ecological restoration and water conservation technology for abandoned coal gangue mines. This technology fully utilizes alkaline industrial waste for neutralization and pretreatment, followed by gradient covering to construct an improved composite soil layer, and finally transplanting highly resistant vegetation combinations and inoculating with microbial agents, thereby restoring the harsh ecological environment of abandoned coal gangue mines.

[0006] This invention provides a water conservation technology for ecological restoration of abandoned coal gangue mines, comprising the following steps: Step 1: Crush, till, and loosen the surface soil of the abandoned coal gangue mine. After surface treatment, evenly spread alkaline waste and heavy metal adsorbent on the surface and repeat tilling until uniform. Step 2: Continue to add composite soil conditioner to the surface soil of the mine after Step 1, and gradually cover it to construct an improved composite soil layer; The improved composite soil layer includes a water-retaining bottom layer, an anti-corrosion slow-release middle layer, and an organic top layer. The composite soil conditioner includes fly ash, steel slag, local clay, straw fiber, water-retaining slow-release microcapsules, biochar, papermaking white mud, and humus. Step 3: Transplant highly resistant vegetation onto the improved composite soil layer obtained in Step 2, and simultaneously inoculate with microbial agents. After the soil has stabilized, it is ready for use.

[0007] Furthermore, in step one, a jaw crusher and a rotary tiller are used to crush and till the surface soil of the mine to a depth of 30-50 cm. The removal of debris and the pretreatment of the surface soil at the same time ensure the uniformity of the coal gangue matrix and provide a good foundation for subsequent remediation.

[0008] Further, the alkaline waste mentioned in step one includes any one or more of steel slag, red mud, eggshell powder, and municipal sludge. The soil in abandoned coal gangue mines is highly acidic. This invention uses steel slag and red mud as neutralizing materials: Steel slag is an industrial waste residue from iron and steel smelting, mainly containing calcium oxide and magnesium oxide, which can effectively neutralize the acidity of coal gangue mine soil. Its mineral phases, dicalcium silicate and tricalcium silicate, can also slowly release alkaline substances to achieve long-term, deep pH regulation. Red mud is an industrial waste generated during alumina production, mainly containing iron oxide and aluminum oxide, which can also neutralize acidic soil. The silicate minerals in red mud can also promote the formation of soil aggregates and improve water and fertilizer retention capacity. Eggshell powder can slowly release calcium ions to neutralize soil acidity, maintain stable soil pH in the long term, and provide a good environment for the deep growth of plant roots. The organic matter rich in municipal sludge can not only improve soil structure and increase nutrient content, but also help alleviate the salinity and alkalinity of red mud. This invention combines the aforementioned industrial waste and domestic waste, enabling low-cost neutralization of acidic mine soils and resource recovery and utilization of various industrial and domestic wastes, while also promoting long-term vegetation growth. The preferred composition of this invention is a combination of 45% steel slag, 20% red mud, 10% eggshell powder, and 25% municipal sludge as alkaline waste. In a specific implementation example, the municipal sludge used has a pH of 8.6-8.8, a moisture content of 70%-76%, and an organic matter content of 50%-55% (dry basis).

[0009] Furthermore, the heavy metal adsorbent described in step one is composed of rice husk biochar and bentonite in a mass ratio of 10:(1-3). Rice husk biochar can effectively adsorb cadmium, lead, etc., in the soil, while bentonite can significantly enhance cation exchange capacity and promote the enrichment of heavy metals in the soil. This invention uses the above-mentioned heavy metal adsorbent to perform preliminary adsorption and solidification of heavy metals in soil and alkaline waste, which is beneficial to the rapid growth and development of vegetation and microorganisms in the later stage, and can improve the restoration rate of the mine ecology.

[0010] Further, the preparation method of the water-retaining and sustained-release microcapsules in step two is as follows: dissolve acrylic acid, acrylamide, and potassium humate in deionized water, add sodium hydroxide solution dropwise under an ice-water bath, then add an initiator and a crosslinking agent and stir to obtain a prepolymer solution. Slowly drop the prepolymer solution into a composite solution of chitosan and sodium montmorillonite, sonicate, and react in a water bath at 50-60℃. Finally, centrifuge, wash, and dry to obtain microcapsules. The mass ratio of chitosan to sodium montmorillonite is (1-2):1, the mass ratio of acrylic acid, acrylamide, and potassium humate is 15:5:3, the initiator is potassium persulfate, and the crosslinking agent is N,N′-methylenebisacrylamide.

[0011] Further, the specific method for constructing the improved composite soil layer in step two is as follows: fly ash, steel slag, and local clay are mixed evenly and then added to the neutralized and adsorbed mine soil. After being tilled evenly, it serves as the water-retaining bottom layer. Then, straw fibers are embedded in the water-retaining bottom layer in a grid pattern to construct a straw fiber grid. Subsequently, a suspension of water-retaining slow-release microcapsules is evenly sprayed to obtain the corrosion-resistant slow-release middle layer. Finally, biochar, papermaking white mud, and humus are mixed and evenly covered onto the surface of the corrosion-resistant slow-release middle layer to construct an organic surface layer. After neutralization and adsorption treatment, this invention uses a mixture of fly ash, steel slag, local clay, and coal gangue matrix as the water-retaining bottom layer. Fly ash can reduce matrix density, increase water holding capacity, and supplement phosphorus and potassium nutrients. Steel slag helps to improve structural strength and impermeability. The mixture of the two can further improve the structural strength of coal gangue mine soil. This water-retaining bottom layer can serve as the base layer for mine soil remediation, enhance deep water retention, and provide a transitional buffer for the deep growth of vegetation roots in the later stages. Building upon the existing water-retaining sublayer, this invention incorporates a mixture of straw fiber and fly ash embedded in a grid pattern within the sublayer to further enhance shear strength and overcome the problem of soil erosion caused by the loose structure of coal gangue. Unlike most current polymeric water-retaining materials, which experience a gradual decrease in water retention capacity over time and decompose or leak away in coal gangue soil, this invention also prepares a slow-release microcapsule that combines excellent water retention and heavy metal adsorption functions, achieving a long-term balanced regulation of the soil. Finally, this invention uses a mixture of biochar, papermaking mud, and humus as an organic surface layer. Biochar has high porosity and adsorption capacity, significantly improving soil water retention capacity and fixing nutrients to reduce leaching. Papermaking mud enhances the impermeability and cohesiveness of the surface layer, while humus is rich in organic matter, providing nutrients and promoting microbial activity. The construction of this organic surface layer provides a sufficient nutrient base for the rapid growth and development of subsequent vegetation and microbial species. Traditional remediation methods may damage the soil after improvement due to continued weathering of coal gangue and erosion by rainwater, resulting in reduced water retention capacity. By constructing the above-mentioned improved composite soil layer, this invention improves the structure of the soil in abandoned coal gangue mines, effectively enhances its water retention and stability, improves its erosion resistance, reduces evaporation, and lays the foundation for the stable and rapid growth of subsequent vegetation and fungi.

[0012] Furthermore, in the water-retaining bottom layer, the mass ratio of fly ash, steel slag, and local clay is 1:(2-3):(3-5), and the thickness of the water-retaining bottom layer is 25-30 cm; in the corrosion-resistant and slow-release middle layer, the spacing of the straw fiber mesh is 20×20 cm; in the organic surface layer, the mass ratio of biochar, papermaking mud, and humus is (20-30):(10-20):1, and the thickness of the organic surface layer is 5-10 cm.

[0013] Furthermore, the highly resistant vegetation described in step three includes *Sedum aizoon*, *Hippophae rhamnoides*, and *Pennisetum alopecuroides*, which are intercropped in a ratio of (40-60):3:(2-5). *Sedum aizoon* is a heavy metal hyperaccumulator and can further absorb heavy metals; *Hippophae rhamnoides* is drought-tolerant and tolerant of poor soil, with a well-developed root system that can fix nitrogen and improve soil fertility, alleviating the problem of poor substrate such as fly ash and steel slag; *Pennisetum alopecuroides* grows quickly and has a deep root system with a different root distribution layer than *Hippophae rhamnoides*, and can also combine with straw fiber mesh, synergistically improving erosion resistance and preventing soil erosion with *Hippophae rhamnoides*; this invention uses complementary transplantation of *Sedum aizoon*, *Hippophae rhamnoides*, and *Pennisetum alopecuroides* to further enhance soil stabilization and restoration effects, regulate microclimate, reduce water consumption, and promote organic matter cycling.

[0014] Further, the microbial inoculant in step three includes arbuscular mycorrhizal fungi, sulfate-reducing bacteria, Pseudomonas, and Frankelbrium, in a ratio of (3-5):1:(1-2):(2-3); wherein the arbuscular mycorrhizal fungi proliferate in the rhizosphere of the clover host, and a spore suspension is collected (density approximately 60 spores / mL), and the sulfate-reducing bacteria solution concentration is approximately 3 × 10⁻⁶. 8 CFU / mL, Pseudomonas bacterial concentration was 2×10⁻⁶. 7 CFU / mL, Frankincense bacterial concentration was 8×10⁻⁶ 6 CFU / mL. Arbuscular mycorrhizal fungi can live in symbiosis with vegetation and promote nutrient absorption; sulfate-reducing bacteria can assist in the treatment of heavy metals; Pseudomonas has the ability to degrade organic matter and fix heavy metals; Frankincense can live in symbiosis with vegetation to fix nitrogen and promote vegetation growth.

[0015] The beneficial effects of this invention are: Addressing the limitations of existing coal gangue-related abandoned mine remediation technologies, this invention integrates multiple technologies and processes, including neutralization and adsorption, soil improvement, vegetation transplantation, and microbial inoculation. These technologies work synergistically to achieve long-term water retention through a multi-layered remediation mechanism involving materials, vegetation, and microorganisms. This invention boasts low raw material and process costs, while also recycling various industrial and domestic waste materials. Compared to traditional mine remediation technologies, it offers better stability and longer-lasting effectiveness, demonstrating promising application prospects. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0018] Example 1 A water conservation technology for ecological restoration of abandoned coal gangue mines, comprising the following steps: 1. Select an abandoned coal gangue mine area with a slope of less than 25°. After removing impurities, use a jaw crusher and rotary tiller to crush and till the topsoil (treatment depth is 50 cm). After the topsoil is loosened and pretreated, spread alkaline waste (45% steel slag, 20% red mud, 10% eggshell powder, 25% urban sludge) and heavy metal adsorbent (rice husk biochar: bentonite = 10:2) evenly on the surface (addition amount is 120 kg / mu of alkaline waste and 20 kg / mu of heavy metal adsorbent), and repeatedly till with a rotary tiller until uniform.

[0019] 2. Add 1 part chitosan to 50 parts of 1% acetic acid solution and stir well. Add 0.8 parts sodium montmorillonite to 50 parts of deionized water and disperse ultrasonically. Mix the two evenly to obtain a wall material composite liquid. Separately, add 15 parts acrylic acid, 5 parts acrylamide, and 3 parts potassium humate to 80 parts of deionized water. Add 20 parts of 10% sodium hydroxide solution dropwise under an ice-water bath. Add 0.2 parts potassium persulfate and 0.1 parts N,N′-methylenebisacrylamide and stir well to obtain a prepolymer liquid. Slowly drop the prepolymer liquid into the wall material composite liquid. After ultrasonication for 15 min, react in a constant temperature water bath at 55℃ for 4 h. After centrifugation, washing, drying, and grinding, water-retaining sustained-release microcapsules are obtained. Fly ash, steel slag, and local clay were mixed evenly (mass ratio 1:2.5:4) and then added to the neutralized and adsorbed mine soil. After being tilled evenly, it served as a water-retaining bottom layer (30 cm). Then, corn stalk fibers (5-10 mm) were mixed with fly ash at a ratio of 3:1 and embedded in the water-retaining bottom layer in a grid pattern (spacing 20×20 cm) to construct a straw fiber grid. Subsequently, a suspension of the above-mentioned water-retaining slow-release microcapsules (microcapsule dosage 15 kg / mu) was evenly sprayed to obtain an anti-corrosion slow-release middle layer. Finally, biochar, papermaking white mud, and humus were mixed (mass ratio 25:15:1) and evenly covered onto the surface of the anti-corrosion slow-release middle layer to construct an organic surface layer (10 cm).

[0020] 3. Transplant *Sedum aizoon*, *Hippophae rhamnoides*, and *Pennisetum affine* (mixed planting at 5000 plants / acre, 300 plants / acre, and 300 clumps / acre) into the improved composite soil layer, and simultaneously inoculate with microbial inoculant (0.5 kg / m²). 3 The mixture was prepared using a 4:1:1.2:2.5 volume ratio of arbuscular mycorrhizal fungi suspension, sulfate-reducing bacteria suspension, Pseudomonas suspension, and Frankelbrium suspension, and was allowed to stabilize.

[0021] The initial soil data were analyzed and compared with the soil data after treatment. The results are shown in Table 1.

[0022] Table 1. Mine Soil Testing Data

[0023] Example 2 A water conservation technology for ecological restoration of abandoned coal gangue mines, comprising the following steps: 1. Select an abandoned coal gangue mine area with a slope of less than 25°. After removing impurities, use a jaw crusher and rotary tiller to crush and till the topsoil (treatment depth is 40 cm). After the topsoil is loosened and pretreated, spread alkaline waste (50% steel slag, 20% red mud, 10% eggshell powder, 20% urban sludge) and heavy metal adsorbent (rice husk biochar: bentonite = 10:1) evenly on the surface (addition amount is 120 kg / mu of alkaline waste and 20 kg / mu of heavy metal adsorbent), and repeatedly till with a rotary tiller until uniform.

[0024] 2. Add 1 part chitosan to 50 parts of 1% acetic acid solution and stir well. Add 0.5 parts sodium montmorillonite to 50 parts of deionized water and disperse ultrasonically. Mix the two evenly to obtain a wall material composite liquid. Separately, add 15 parts acrylic acid, 5 parts acrylamide, and 3 parts potassium humate to 80 parts of deionized water. Add 20 parts of 10% sodium hydroxide solution dropwise under an ice-water bath. Add 0.2 parts potassium persulfate and 0.1 parts N,N′-methylenebisacrylamide and stir well to obtain a prepolymer liquid. Slowly drop the prepolymer liquid into the wall material composite liquid. After ultrasonication for 15 min, react in a constant temperature water bath at 55℃ for 4 h. After centrifugation, washing, drying, and grinding, water-retaining sustained-release microcapsules are obtained. Fly ash, steel slag, and local clay were mixed evenly (mass ratio 1:2:5) and then added to the neutralized and adsorbed mine soil. After being tilled evenly, it served as a water-retaining bottom layer (25 cm). Then, corn stalk fibers (5-10 mm) were mixed with fly ash at a ratio of 3:1 and embedded in the water-retaining bottom layer in a grid pattern (spacing 20×20 cm) to construct a straw fiber grid. Subsequently, a suspension of the above-mentioned water-retaining slow-release microcapsules (microcapsule dosage 15 kg / mu) was evenly sprayed to obtain an anti-corrosion slow-release middle layer. Finally, biochar, papermaking white mud, and humus were mixed (mass ratio 20:20:1) and evenly covered onto the surface of the anti-corrosion slow-release middle layer to construct an organic surface layer (10 cm).

[0025] 3. Transplant *Sedum aizoon*, *Hippophae rhamnoides*, and *Pennisetum affine* (mixed planting at 4000 plants / acre, 300 plants / acre, and 500 clumps / acre) into the improved composite soil layer, and simultaneously inoculate with microbial inoculant (0.5 kg / m²). 3 The mixture was prepared using a 4:1:1.6:2.4 volume ratio of arbuscular mycorrhizal fungi suspension, sulfate-reducing bacteria suspension, Pseudomonas suspension, and Frankelbrium suspension, and was allowed to stabilize.

[0026] The initial soil data were analyzed and compared with the soil data after treatment. The results are shown in Table 2.

[0027] Table 2. Mine Soil Testing Data

[0028] Example 3 A water conservation technology for ecological restoration of abandoned coal gangue mines, comprising the following steps: 1. Select an abandoned coal gangue mine area with a slope of less than 25°. After removing impurities, use a jaw crusher and rotary tiller to crush and till the topsoil (treatment depth is 45 cm). After the topsoil is loosened and pretreated, spread alkaline waste (50% steel slag, 15% red mud, 10% eggshell powder, 25% urban sludge) and heavy metal adsorbent (rice husk biochar: bentonite = 10:3) evenly on the surface (addition amount is 120 kg / mu of alkaline waste and 20 kg / mu of heavy metal adsorbent), and repeatedly till with a rotary tiller until uniform.

[0029] 2. Add 1 part chitosan to 50 parts of 1% acetic acid solution and stir well. Add 1 part sodium montmorillonite to 50 parts of deionized water and disperse ultrasonically. Mix the two evenly to obtain a wall material composite liquid. Separately, add 15 parts acrylic acid, 5 parts acrylamide, and 3 parts potassium humate to 80 parts of deionized water. Add 20 parts of 10% sodium hydroxide solution dropwise under an ice-water bath. Add 0.2 parts potassium persulfate and 0.1 parts N,N′-methylenebisacrylamide and stir well to obtain a prepolymer liquid. Slowly drop the prepolymer liquid into the wall material composite liquid. After ultrasonication for 15 min, react in a constant temperature water bath at 55℃ for 4 h. After centrifugation, washing, drying, and grinding, water-retaining sustained-release microcapsules are obtained. Fly ash, steel slag, and local clay were mixed evenly (mass ratio 1:3:3) and then added to the neutralized and adsorbed mine soil. After being tilled evenly, it served as a water-retaining bottom layer (30 cm). Then, corn stalk fibers (5-10 mm) were mixed with fly ash at a ratio of 3:1 and embedded in the water-retaining bottom layer in a grid pattern (spacing 20×20 cm) to construct a straw fiber grid. Subsequently, a suspension of the above-mentioned water-retaining slow-release microcapsules (microcapsule dosage 18 kg / mu) was evenly sprayed to obtain an anti-corrosion slow-release middle layer. Finally, biochar, papermaking white mud, and humus were mixed (mass ratio 30:10:1) and evenly covered onto the surface of the anti-corrosion slow-release middle layer to construct an organic surface layer (8 cm).

[0030] 3. Transplant *Sedum aizoon*, *Hippophae rhamnoides*, and *Pennisetum affine* (mixed planting at 6000 plants / acre, 300 plants / acre, and 200 clumps / acre) into the improved composite soil layer, and simultaneously inoculate with microbial inoculant (0.5 kg / m²). 3 The mixture was prepared using a 5:1:1:2 volume ratio of arbuscular mycorrhizal fungi suspension, sulfate-reducing bacteria suspension, Pseudomonas suspension, and Frankelbrium suspension, and was allowed to mature.

[0031] The initial soil data were analyzed and compared with the soil data after treatment. The results are shown in Table 3.

[0032] Table 3. Mine Soil Testing Data

[0033] Comparative Example 1 Refer to the steps and parameters in Example 1, except that step 2 does not use sodium-based montmorillonite to prepare water-retaining sustained-release microcapsules.

[0034] The initial soil data were analyzed and compared with the soil data after treatment. The results are shown in Table 4.

[0035] Table 4. Mine Soil Testing Data

[0036] Comparative Example 2 Referring to the steps and parameters of Example 1, the difference is that in step 3, the volume ratio of arbuscular mycorrhizal fungal suspension, sulfate-reducing bacteria solution, Pseudomonas solution, and Frankel's solution is adjusted to 1:1:1:1.

[0037] The initial soil data were analyzed and compared with the soil data after treatment. The results are shown in Table 5.

[0038] Table 5. Mine Soil Testing Data

[0039] Based on the test results of Examples 1-3 above, it can be seen that the mine restoration technology of the present invention has strong water and fertilizer retention capacity. Through the combined action of multiple restoration mechanisms of materials, vegetation, and microorganisms, the soil restoration of abandoned coal gangue mines can be basically completed after a short period of treatment: the heavy metal content is significantly reduced, the content of nutrients such as nitrogen, phosphorus, and potassium is significantly increased, and it has excellent long-term water retention capacity, ensuring the stability of the mine soil and effectively reducing the cumbersome maintenance costs in the later stage. Comparing the data of Example 1 and Comparative Example 1, it can be seen that the water-retaining slow-release microcapsules prepared by the present invention can play a stable and long-term water retention role, and the water retention capacity will not gradually weaken due to external factors or other factors. Compared with most existing polymer water-retaining materials, the improvement effect is significant. Comparing the data of Example 1 and Comparative Example 2, it can be seen that the combination and ratio of microbial strains selected in the present invention have a significant impact on the synergistic restoration effect of materials, vegetation, and microorganisms. The raw materials and process costs of the present invention are low, and various industrial and domestic wastes are recycled and utilized. Compared with traditional mine restoration technologies, it has better stability and longer-lasting effect, and has good application prospects.

[0040] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they are not intended to limit the present invention. It should be noted that various changes and modifications can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the concept and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for ecological restoration and water conservation in abandoned coal gangue mines, characterized in that, Includes the following steps: Step 1: Crush, till, and loosen the surface soil of the abandoned coal gangue mine. After surface treatment, evenly spread alkaline waste and heavy metal adsorbent on the surface and repeat tilling until uniform for neutralization and adsorption treatment. The alkaline waste includes any one or more of steel slag, red mud, eggshell powder, and municipal sludge; Step 2: Continue to add composite soil conditioner to the surface soil of the mine after Step 1, and gradually cover it to construct an improved composite soil layer; The composite soil conditioner includes fly ash, steel slag, local clay, straw fiber, water-retaining slow-release microcapsules, biochar, papermaking mud, and humus. The preparation method of the water-retaining slow-release microcapsules is as follows: acrylic acid, acrylamide, and potassium humate are dissolved in deionized water, sodium hydroxide solution is added dropwise under an ice-water bath, then an initiator and a crosslinking agent are added and stirred to obtain a prepolymer solution. The prepolymer solution is slowly added dropwise to a composite solution of chitosan and sodium montmorillonite, ultrasonicated, and reacted in a water bath at 50-60℃. Finally, the microcapsules are obtained by centrifugation, washing, and drying. The mass ratio of chitosan to sodium montmorillonite is (1-2):

1. The improved composite soil layer comprises a water-retaining bottom layer, an anti-corrosion slow-release middle layer, and an organic surface layer, which are sequentially layered and constructed using the following method: Fly ash, steel slag, and local clay are mixed evenly and then added to the neutralized and adsorbed mine soil. After even tilling, this mixture forms the water-retaining bottom layer. Straw fibers are then embedded in the water-retaining bottom layer in a grid pattern to construct a straw fiber grid. A suspension of water-retaining slow-release microcapsules is then evenly sprayed to obtain the anti-corrosion slow-release middle layer. Finally, biochar, papermaking mud, and humus are mixed and evenly applied to the surface of the anti-corrosion slow-release middle layer to construct the organic surface layer. The mass ratio of fly ash, steel slag, and local clay in the water-retaining bottom layer is 1:(2-3):(3-5), and the thickness of the water-retaining bottom layer is 25-30 cm. The straw fiber grid spacing in the anti-corrosion slow-release middle layer is 20×20 cm. cm; In the organic surface layer, the mass ratio of biochar, papermaking mud and humus is (20-30):(10-20):1, and the thickness of the organic surface layer is 5-10 cm. Step 3: Transplant highly resistant vegetation onto the improved composite soil layer obtained in Step 2, and simultaneously inoculate with microbial agents. Allow the soil to stabilize before proceeding.

2. The method for ecological restoration and water conservation in abandoned coal gangue mines according to claim 1, characterized in that, In step one, a jaw crusher and a rotary tiller are used to crush and till the surface soil of the mine to a depth of 30-50 cm.

3. The method for ecological restoration and water conservation in abandoned coal gangue mines according to claim 1, characterized in that, The heavy metal adsorbent described in step one is composed of rice husk biochar and bentonite in a mass ratio of 10:(1-3).

4. The method for ecological restoration and water conservation in abandoned coal gangue mines according to claim 1, characterized in that, The highly resistant vegetation described in step three includes Sedum aizoon, Hippophae rhamnoides, and Napier grass. Sedum aizoon, Hippophae rhamnoides, and Napier grass are interplanted at a density of 4,000-6,000 plants / acre, 300 plants / acre, and 200-500 clumps / acre, respectively.

5. The method for ecological restoration and water conservation in abandoned coal gangue mines according to claim 1, characterized in that, The microbial inoculant mentioned in step three includes arbuscular mycorrhizal fungi, sulfate-reducing bacteria, Pseudomonas, and Frankelbrium, with a volume ratio of (3-5):1:(1-2):(2-3).

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