A recycled heavy metal tailings slag slope protection material and its preparation method

Abstract

This invention provides a slope protection material composed of recycled heavy metal tailings and its preparation method. The material includes: recycled heavy metal tailings treated with a heavy metal chelating agent as a heavy metal ion capture agent, the chelating agent being added at 0.05%–0.2% of the heavy metal tailings weight; recycled heavy metal tailings as aggregate, which is mixed with natural soil to form a base material at a ratio of 1:1.5–2.5; fine aggregate and fine sand, added at 5%–10% of the base material weight; and high-viscosity industrial-grade sodium alginate added as a water-retaining and reinforcing agent, added at 0.5%–2.0% of the base material weight. Additionally, 28% organic matter is added to the base material. The application of this invention effectively solves the problems of ineffective utilization of recycled heavy metal tailings and excessive use of scarce natural soil in existing technologies, and also addresses the issues of weak strength, poor effectiveness in steep slope treatment, and poor stability in existing slope protection materials.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal polluted waste mine recycling application, specifically involving a recycled heavy metal tailings slag slope protection material and its preparation method. Background Technology

[0002] In the ecological restoration of abandoned mining areas and the treatment of steep slopes in mountainous areas and roadsides, the main component of existing slope protection materials is natural soil. However, natural soil in the construction area of ​​slope protection projects is a scarce resource. Therefore, the construction of slope protection projects often leads to the over-exploitation of natural soil and high project costs. In abandoned mining areas with heavy metals, a large amount of heavy metal tailings are accumulated, which on the one hand occupies limited land resources (approximately 14.4 million hectares of land nationwide), and on the other hand, the heavy metals contained in the tailings can easily leach into the soil and water bodies (daily infiltration rate of 0.5-3.0 meters), causing pollution to the ecological environment of the accumulation area and the surrounding mining area. How to recycle these waste heavy metal tailings to eliminate pollution sources has become a difficult problem. There is a solution that uses copper tailings solid waste to be mixed into slope protection materials, but the heavy metals are not treated, which causes secondary pollution ("Preparation and Planting Experiment of Ecological Slope Protection Substrate for Copper Tailings", Nonferrous Metals Engineering, Cheng Cifeng, Liu Wenlian, Zhao Haiyan, Zheng Ting, Feng Zhihong, Dong Wei). Some researchers have used alkaline materials such as lime to solidify heavy metals in order to achieve the reuse of heavy metal tailings. However, this produces flocculated sludge (accounting for 20% of the treatment volume), which requires secondary treatment and has poor solidification stability. In addition, its pH > 9 inhibits the growth of slope protection plants ("Research on the Application of Heavy Metal Collectors in the Treatment of Low-Concentration Mine Wastewater", Master's Thesis, Nanchang University, Liu Xiumei).

[0003] The mechanical properties of existing slope protection materials are not suitable for steep slope protection. During heavy rainfall, the loss rate of slope protection materials is extremely high, resulting in frequent disasters such as debris flows and collapse of the main slope structure. Some materials use binders such as CMC (sodium carboxymethyl cellulose) to improve the cohesion and strength of the material, but this reduces the internal friction angle and weakens the resistance to disintegration. After erosion on steep slopes (>50°), the peeling area is >30% ("Experimental Study on Thick Substrate Sprayed Slope Protection", Bulletin of Soil and Water Conservation, Zhang Junyun, Zhou Depei, Li Shaocai). Other materials improve the water retention of the material by increasing the content of water-retaining agents, thereby increasing the root and stem growth rate of slope protection plants and enhancing the stability of the slope protection material ("Effect of Hydrogel Additives on the Hydraulic Properties and Erosion Resistance of a Slope Soil Cover", Environmental Earth Sciences, 2016). However, this usually comes at the cost of sacrificing adhesion, making the material more susceptible to damage when exposed to rainwater erosion.

[0004] In summary, existing slope protection materials contain an excessive proportion of natural soil, leading to over-exploitation of natural soil. Furthermore, they fail to effectively address the mechanical strength issues of these materials, exhibiting weak resistance to rainwater erosion, particularly in poor performance on steep slopes. Therefore, researchers in this field urgently need to explore a new slope protection material that can remove pollution and recycle waste heavy metal tailings slag, replacing soil and saving on natural soil usage, while also improving the material's mechanical strength, providing strong slope protection and stability in steep slope treatment, and simultaneously considering ecological and environmental protection. Summary of the Invention

[0005] This invention uses a synergistic mixing system as the material, taking into account the advantages of high utilization rate, low cost, strong mechanical properties, and good durability of recycled heavy metal tailings slag. Moreover, the preparation method is simple and easy to promote on a large scale. The specific scheme is as follows: 1. A new slope protection material using recycled heavy metal slag as aggregate. This invention uses recycled heavy metal tailings slag, from which heavy metal ions have been removed, as aggregate, mixed with natural soil in a specific ratio to form a slope protection base material. Fine aggregate, binder, and moisture retention agent are added to the base material, along with structural nutrient regulators, to create a slope protection material. This not only solves the pollution problem caused by the accumulation of heavy metal tailings slag, but also promotes recycling and uses it to replace natural soil, addressing the problem of over-exploitation of natural resources. Furthermore, it overcomes the problems of insufficient strength and poor stability of existing slope protection materials, while also taking into account ecological and environmental protection.

[0006] First, recycled heavy metal tailings are treated with a heavy metal chelating agent to remove heavy metal ions through a chemical reaction. Second, the recycled heavy metal tailings are mixed with natural soil in a specific ratio to form a base material. Third, fine aggregates are added to this base material to improve its basic strength, and industrial-grade sodium alginate with high viscosity and hydrophilicity is added to enhance its binding and moisture retention. Organic matter is added to improve the material's nutritional structure and promote the survival and growth of vegetation roots. Thus, a new slope protection material is formed using recycled heavy metal tailings as aggregate.

[0007] The heavy metal tailings aggregate includes, but is not limited to: lead, zinc, copper, mercury, cadmium, manganese, nickel, and chromium (Pb). 2+ Zn 2+ Cu 2 + Hg 2+ Cd 2+ Mn 2+ Ni 2+ Cr 3+ One or more of the following: tailings slag; When regenerating heavy metal tailings, a heavy metal chelating agent is added as a heavy metal ion capture agent. The heavy metal chelating agent includes, but is not limited to, dithiocarbamate-DTCR (abbreviation for Dithiocarbamate Reactive group-based heavy metal scavenger), hereinafter referred to as DTCR. The amount of DTCR added is 0.05% to 0.2% of the actual amount of heavy metal tailings used. The mechanism of DTCR capturing heavy metal ions is mainly based on the unique -SS- group in its molecular structure. These groups can undergo a strong chelation reaction with heavy metal ions to form water-insoluble chelate precipitates, thereby effectively removing heavy metal ions from the heavy metal tailings. Generally, the higher the concentration of DTCR and the longer the reaction time, the higher the capture rate of heavy metal ions. However, through experiments and practice, it has been found that excessively high DTCR concentrations may lead to unnecessary increases in economic costs and potential pollution (such as organic pollution caused by unreacted organic chelating agent residues, migration of soluble heavy metal complexes, secondary disposal risks of difficult-to-treat sludge, and biotoxic inhibition of soil microorganisms and plant growth). Therefore, 0.1% of the above percentages is the preferred addition amount, which can achieve a good effect of removing heavy metal ions without causing potential pollution. The natural soils include, but are not limited to: in-situ soils in heavy metal mining areas or slope protection engineering implementation areas, and one or more types of wilderness soils from other regions; The mass ratio of the recycled heavy metal tailings aggregate to the natural soil mixture is 1:1.5-2.5. Experiments and practice have shown that when the proportion of heavy metal tailings aggregate in the slope protection material exceeds 50%, the increased gravity due to the high content of heavy metal tailings in the material leads to poor slope stabilization, failing to meet the slope protection purpose of steep slopes under heavy rain erosion. (The recycled heavy metal tailings have a high density (>2.5 g / cm³)). 3The material has poor adhesion and water retention. When its mass proportion in the substrate exceeds 50%, the overall weight of the material increases significantly, leading to a sharp increase in the sliding force it can withstand on steep slopes (>50°). Simultaneously, due to the reduced proportion of natural soil, the cohesion, capillary water retention capacity, and root anchoring capacity of the substrate decrease, causing the material to lose structural stability. Under heavy rainfall, the material is highly susceptible to overall slippage, layered peeling, or disintegration, further exacerbating the risk of slope instability. When the proportion is below 25%, the small amount reduces the utilization rate of recycled heavy metal tailings, failing to achieve the goal of saving natural sand and reducing slope protection costs. A 1:2 mass ratio of heavy metal tailings aggregate to natural sand is the preferred ratio. On the one hand, it effectively reduces the weight of the slope protection material; on the other hand, the heavy metal tailings increase the porosity of the slope protection material, allowing for better water and air management, promoting plant growth, improving material structure, and ultimately improving slope stability and vegetation coverage, reducing the amount of natural soil used, and lowering the cost of the slope protection material. The fine aggregate is fine sand, including either quartz sand or weathered sand, with a particle size of 0.1–0.5 mm (<0.1 mm: close to clay, prone to caking; >0.5 mm: damages the gel network, affecting spraying). The addition amount is 5%–10% of the mixed base material of recycled heavy metal tailings slag aggregate and natural sand, preferably 8%, to balance mechanical improvement and ecological balance. The quartz sand or weathered sand is washed, screened, and tested for heavy metal leaching. The leaching concentrations of lead, cadmium, mercury, chromium, and arsenic meet the limits of GB 5085.3-2007, and the pH value is 6.5–7.5. The bonding and moisture-retaining agents of the slope protection material are selected from high-viscosity hydrophilic compounds, including but not limited to: industrial-grade sodium alginate with enhanced viscosity, preferably sodium alginate with a viscosity greater than 2000 cps. For ease of description, sodium alginate meeting this condition will be referred to as sodium alginate (II) below; the amount of sodium alginate (II) added is 0.5% to 2.0% of the mixed base material of recycled heavy metal tailings slag aggregate and natural sand; sodium alginate (II) will form a hydrogen bond network with the material particles, and by establishing a continuous gel network, enhance the adhesion between material particles, and increase the cohesion to 31 kPa (79.2% higher than that of pure natural soil); its molecular chain hydrophilic groups (-COO) -The alginate (-OH) can adsorb water dozens of times its own weight, swell to form a gel, increasing the water retention rate by 40%, prolonging the wetting time of slag and sand, and improving the survival rate of plants; it penetrates the gaps between slag and sand particles through a high-viscosity solution, encapsulating the slag and sand particles to form a three-dimensional network, improving the material's resistance to erosion; the formed calcium alginate gel has thermal irreversibility, maintaining the integrity of the slope protection structure under extreme climates; its natural polysaccharides are non-toxic and biodegradable, avoiding pollution of soil and water bodies, and meeting the sustainable requirements of ecological engineering; controlling the proportion of sodium alginate (II) at 1.0% is the preferred proportion, because experiments and practice have found that: when the proportion is higher than this, the strength of the substrate is not substantially improved, but the cost increases several times; when the proportion is lower than this, the adhesion of the substrate is not sufficiently improved, and the strength required for steep slope protection is not achieved.

[0008] The added organic matter includes one or more of peat, sphagnum moss, rice straw, sawdust, and humus; the preferred addition amount is 28% of the mixed substrate of recycled heavy metal tailings aggregate and natural soil, which is also determined through experiments and practice; the addition of organic matter peat and sphagnum moss increases the total porosity of the substrate, increases the water holding capacity between particles, alleviates the problem of compaction of recycled heavy metal tailings, and enhances the strength of the substrate; straw fiber, sawdust, or humus form a network structure with sodium alginate (II), reducing soil erosion caused by rainfall; peat neutralizes the alkalinity of recycled heavy metal tailings, stabilizing the overall pH of the substrate between 6.0 and 7.5, promoting the development of most plant roots, and straw, sawdust, or humus decompose to release organic nitrogen and potassium, while peat provides phosphorus, which, combined with the cation exchange capacity of sphagnum moss, enhances the sustainability of fertility of recycled heavy metal tailings and sandy soil; straw and sphagnum moss provide soluble organic carbon, increasing microbial biomass carbon, accelerating the mineralization of organic matter and the biopassivation of recycled heavy metal tailings, and eliminating environmental pollution.

[0009] 2. Preparation method of a new slope protection material composed of recycled heavy metal tailings slag The method and steps are as follows: Step S1: Select the required amount of heavy metal tailings slag according to the specific requirements of the slope protection project. Sieve the slag to obtain a slag with an average particle size of 0.5mm. Add water and stir evenly. The water-to-tailings slag mass ratio (liquid-solid ratio) is 4-6:1. (Before using DTCR chelation treatment, to overcome the problems of easy settling and difficulty in mixing of coarse heavy metal tailings slag and to ensure the effect of heavy metal ion removal reaction, first sieve to a suitable particle size, and then use different mass ratios according to different heavy metal tailings slag. Focus on observing the stirring and mixing effect, settling situation, and combining the stirring intensity and reaction...) The time was optimized to determine the most suitable liquid-to-solid ratio. Then, the heavy metal chelating agent DTCR was added at a rate of 0.05% to 0.2% of the amount of heavy metal tailings. The mixture was stirred thoroughly until it formed a turbid suspension. Then, it was allowed to stand for 7 days to ensure that DTCR was evenly distributed in the heavy metal tailings and had enough time to capture the heavy metal ions in the tailings and form a stable chelated salt precipitate. After 7 days, the water was removed, leaving all the heavy metal tailings precipitate. The precipitate was then dried and used as recycled heavy metal tailings aggregate. Step S2: Select one or more types of soil from the mining area, the original soil from the slope protection project area, or the surrounding and other wasteland soil. The amount should be 1.5-2.5 times the amount of recycled heavy metal tailings aggregate in S1, i.e., the mass ratio is slag: soil = 1:1.5-2.5. Mix the slag aggregate and soil to form a base material. In step S3, 5% to 10% of the amount of fine sand, 0.5% to 2.0% of the amount of industrial-grade alginate with enhanced viscosity, and 28% of the amount of organic matter are added to the substrate formed in S2. Step S4: Based on the natural soil moisture content of the slope protection project area or mining area, add the required amount of water to the substrate of fine sand, industrial-grade enhanced viscosity sodium alginate, and organic matter added in S3, and stir thoroughly to form a slurry. Place this slurry in a closed environment at room temperature for one day to produce a new slope protection material composed of recycled heavy metal tailings slag as aggregate. The one-day placement allows the industrial-grade enhanced viscosity sodium alginate time to fully function in the material, forming a complete gel network and enhancing the adhesion between material particles. When using, spray the slope protection material evenly onto the protected slope surface according to the requirements of the slope protection project.

[0010] In the above preparation method, to ensure that the recycled heavy metal tailings slag and natural soil form a homogeneous mixed structure in the substrate, and to achieve sufficient DTCR chelation reaction, continuity of the sodium alginate gel network, and stability of subsequent spraying construction, this invention specifies that both the tailings slag and natural soil are screened using a 0.5 mm standard sieve. Experiments have shown that when the particle size of any component deviates from the range of 0.5 mm ± 0.1 mm, it will lead to segregation after mixing, decreased chelation efficiency, gel network breakage, spraying blockage, or uneven coverage, ultimately affecting the slope protection capability. Beneficial effects

[0011] This invention achieves the systematic recycling of four resources: waste tailings, soil, water, and vegetation, through a synergistic system that utilizes recycled heavy metal tailings as aggregate, DTCR chelation to remove heavy metal ions, fine sand reinforcement, sodium alginate gel to improve strength and water retention, and organic matter ecological regulation. Simultaneously, the slope protection material of this invention possesses strong physicochemical properties, ensuring the quality of slope protection, especially for steep exposed mining slopes, while also protecting the ecosystem. Specific effects are as follows: Features of this invention: 1. This invention uses recycled heavy metal tailings slag as aggregate, solving the problem of large-scale accumulation of heavy metal tailings slag in abandoned mining areas, which occupies limited land resources: For every hectare of steep slope restored, approximately 1950 tons of tailings slag are consumed, freeing up 0.042 hectares of occupied land; if promoted nationwide, over 4000 hectares of land could be freed up annually, effectively alleviating the pressure of "14.4 million hectares" of stockpiling. It also addresses the social problem of heavy metal ion pollution in mining slag by using recycled heavy metal tailings slag to replace soil in slope protection materials, achieving a heavy metal removal rate of over 65%, with leaching concentrations fully meeting national hazardous waste standards; the utilization rate of heavy metal tailings slag is greater than 45%, reducing the amount of natural soil extracted by 37%; and because no secondary sludge treatment is required, the overall cost is reduced by 30%, resulting in significant social and economic benefits.

[0012] 2. This invention optimizes the physical structure of slope protection materials. Firstly, by introducing clean fine quartz sand or weathered sand as auxiliary fine aggregate, this fine aggregate, being inert mineral particles, does not participate in chemical reactions, does not change the system's pH, and is fully compatible with the sodium alginate gel network and organic matter. Its essential function is physical structure enhancement. Secondly, industrial-grade, high-viscosity sodium alginate, together with recycled heavy metal tailings slag, natural soil, and fine aggregate, forms a composite mineral matrix system. This system, through mechanical interlocking and friction between particles, significantly improves the internal friction angle and shear stability of the matrix, while maintaining good pore structure and construction fluidity. The invented slope protection material has a shear strength of 196.7 kPa (normal stress 200 kPa), which is 61.9% higher than that of traditional materials, and a disintegration rate of 0.881 g / min, which is 19.1% lower. The organic peat and sphagnum moss increase the total porosity of the material, and together with the water retention of sodium alginate, they increase the water holding capacity between particles, alleviate the problem of heavy metal tailings aggregate compaction, ensure the water supply to plant roots, and the straw fiber and sodium alginate form a network structure to lock in the material and reduce soil erosion caused by rainfall. It is particularly effective in the protection of high and steep slopes.

[0013] 3. This invention has low cost and good environmental protection effect: The price of industrial grade high viscosity sodium alginate (sodium alginate (II)) is about RMB30,000-50,000 / ton (while food grade is as high as RMB80,000-145,000 / ton), which is inexpensive; the chelate formed after using DTCR has high stability, low risk of heavy metal leaching, no subsequent sludge disposal cost, non-toxic and biodegradable, and the material cost is more than 30% lower than the traditional "soil replacement method"; the organic matter of the material of this invention can neutralize the alkaline nature of heavy metal tailings waste, stabilize the overall pH of the slope protection material at 6.0-7.5, promote the development of most plant roots, make it more suitable for plant growth, and the plant roots are well developed, resulting in a significant slope stabilization effect. The sediment loss rate after rainwater erosion on a 60-degree steep slope is only 0.44g / min.

[0014] 4. The production and construction process of this invention is simple and can be applied on a large scale: DTCR is a mature raw material suitable for large-scale treatment of heavy metal tailings; its chelation reaction is fast and compatible with existing coagulation and sedimentation equipment, requiring no process modification. In slope protection, the application of sodium alginate gel and other materials requires a premixing step, which can be solved by automated spraying equipment.

[0015] 5. Extension of this invention: The properties of DTCR can be extended to the in-situ fixation of heavy metals in soil (such as the restoration of tailings-occupied land). When combined with ordinary water-retaining agents and organic matter, the remediation cost is 30% lower than that of soil replacement method. The properties of industrial-grade high-viscosity sodium alginate (sodium alginate (II)) can also be used as a coagulant to replace aluminum salts and treat high-turbidity wastewater in mining areas, providing a scalable, quantifiable and replicable green technology path for "carbon-neutral mines" and "waste-free mining areas". Attached Figure Description

[0016] Figure 1 Bar chart of heavy metal ion capture rate; Figure 2 Heavy metal ion content-time variation curve; Figure 3 Curves showing the average number of buds emerging in each group at different times; Figure 4 Average seedling length of each group at 30 days; Figure 5 Maximum seedling length and root length of each group at 30 days; Figure 6 Average root length of each group at 30 days; Figure 7 Dosage-cohesion variation curve; Figure 8 Dosage-internal friction angle variation curve; Figure 9 Fitting curve of sodium alginate (II) dosage-shear strength variation; Figure 10 Curve showing the relationship between dosage and average disintegration rate; Figure 11 Curve showing the relationship between dosage and disintegration rate at the same time; Figure 12 Total runoff under different slope conditions; Figure 13 Total alluvial mass under different slope conditions. Specific Implementation

[0017] Example 1 Slope protection material composition: 41.2% recycled heavy metal tailings slag, 58.8% natural soil, 5% quartz fine sand, 0.5% sodium alginate (II), 20% peat, 6% sphagnum moss, and 2% rice straw; preparation: Step S1, take heavy metal ore copper (containing Cu) 2+ 41.2% of the tailings were ion-treated by sieving with a 0.5mm sieve to remove large particles and impurities. (The process strategy of controlling the particle size of the tailings and subsequent soil within 0.5mm ± 0.1mm is an irreplaceable technical condition for achieving synergistic functions such as "efficient chelation, uniform gelation, stable spraying, and erosion-resistant slope protection." This fundamentally distinguishes it from existing slope protection materials, which suffer from the technical bottlenecks of "mixed coarse and fine particles, uneven reaction, and imprecise and unscientific construction." It transforms recycled tailings from "passive landfill material" into a high-performance material that is "engineerable, sprayable, and ecological," a significant feature that differentiates this invention from existing technologies.) Copper tailings were added to water at a liquid-to-solid ratio of 4:1, and the equipment was started for initial stirring. Then, 0.05% of the tailings were added. The dithiocarbamate-DTCR was mixed in a forced mixer. The mixer, equipped with automatic control, improved mixing efficiency and uniformity, reducing the uncertainty of manual operation. This process dissolved the slag in water, forming a turbid suspension, ensuring that the DTCR was evenly distributed in the copper tailings slag. The mixture was then left to stand for 7 days to allow the DTCR to fully capture copper ions in the tailings slag, forming a stable chelated salt flocculent precipitate. After 7 days, the water was removed, and all the tailings slag chelated precipitate was collected, dried, and used as recycled heavy metal copper tailings aggregate for later use. Step S2: Take 58.8% of the in-situ soil from the mining area, sieve it with a sieve size of 0.5mm, and then mix it with the above-mentioned prepared recycled copper tailings to form a base material. Step S3: Add 5% fine quartz sand (fine sand requirements: particle size 0.1–0.5 mm, heavy metal leaching concentration ≤ GB 5085.3 limit, pH = 6.5–7.5, mud content ≤3%, organic matter content ≤0.5%, no visible impurities) and 0.5% sodium alginate (II) to the mixed substrate in S2 above. Add organic matter: 20% peat, 6% sphagnum moss, and 2% sawdust. Step S4: Add water to the substrate containing quartz fine sand, sodium alginate (II), and organic matter from Step S3, according to the required water content of the in-situ soil in the mining area. Use a mixer for high-intensity stirring to ensure that all components are evenly distributed in a slurry. By sampling and testing, check whether the content of each component in the material is consistent to verify whether the stirring is uniform. If unevenness is found, the stirring time and intensity need to be adjusted until satisfactory uniformity is achieved. The slope protection material prepared above needs to be left in a closed environment at room temperature for 1 day to promote the formation of a gel network of sodium alginate (II) in the material and enhance the adhesion between materials, thereby producing a slope protection material for the recycled copper tailings slag mining area. When applying, spray the slope protection material evenly onto the engineering protection slope (while spraying grass seeds and cultivating and maintaining them according to plant growth standards).

[0018] Example 2

[0019] Slope protection material composition: 33.3% recycled heavy metal slag, 66.7% natural sand, 8% quartz fine sand, 1.0% sodium alginate (II), 20% peat, 6% sphagnum moss, and 2% rice straw; preparation: Step S1, take heavy metal ore lead (containing Pb) 2+ 33.3% of the lead tailings were screened using a 0.5mm sieve to remove large particles and impurities. Water was added to the lead tailings at a liquid-to-solid ratio of 6:1, and the equipment was started for initial stirring. Then, 0.1% of dithiocarbamate-DTCR (based on the amount of lead tailings) was added and mixed in a forced mixer. The mixer, equipped with automatic control, improved stirring efficiency and uniformity, reducing the uncertainty of manual operation. This ensured the tailings dissolved in water to form a turbid suspension, guaranteeing that DTCR was evenly distributed throughout the lead tailings. The mixture was allowed to stand for 7 days to allow DTCR to fully capture lead ions in the tailings, forming a stable chelated flocculent precipitate. (The chelation process of DTCR with heavy metal ions: The sulfur atoms in the DTCR molecule have a high electron cloud density, allowing them to act as ligands and form chelates with heavy metal ions through coordination bonds; the DTCR molecule contains at least two active sulfur atoms, located at both ends of the -SC(=O)NH2 group. These sulfur atoms can react with heavy metal ions such as lead (Pb).) 2+ ), Zinc (Zn) 2+ ), copper (Cu) 2+ These compounds form stable five- or six-membered cyclic chelates; this cyclic structure significantly enhances the stability of the chelate and reduces the mobility and bioavailability of heavy metal ions in the environment. Chelate formation: Primitive lead ions (Pb) form the chelate. 2+ For example, DTCR and Pb 2+ The chelation reaction can be represented as R-NH-CS-S-Pb 2+->[R-NH-CS-S-Pb-S2]↓, in this reaction, the sulfur atom of the DTCR molecule reacts with Pb. 2+ Ions form coordinate bonds, generating chelate salt precipitates that are insoluble in water. R in the reaction formula usually represents an organic group, which can be any combination of non-metallic atoms, determining the lipophilicity of the chelating agent and its stability under specific environmental conditions. After 7 days, the water is removed, and all tailings chelate precipitates are collected, dried, and used as recycled lead tailings aggregate. Step S2: Take 66.7% of the original soil from the construction site of the slope protection project and the surrounding wilderness soil, and after sieving with a sieve size of 0.5mm, mix it with the above-mentioned prepared recycled lead tailings slag aggregate to form the base material. Step S3: Add 8% fine quartz sand (same requirements as in Example 1), 1.0% sodium alginate (II), 20% peat, 6% charcoal, and 2% rice straw to the mixed substrate from Step S2. Step S4: Add water to the mixture of quartz sand, sodium alginate (II), and organic substrate from Step S3 according to the natural moisture content of the soil in the slope protection construction area. Use a mixer for high-intensity stirring to ensure that all components are evenly distributed in a slurry. By sampling and testing, check whether the content of each component in the mixture is consistent to verify whether the stirring is uniform. If unevenness is found, the stirring time and intensity need to be adjusted until satisfactory uniformity is achieved. The above mixed material also needs to be left in a sealed environment at room temperature for 1 day to promote the formation of a gel network of sodium alginate (II) in the slope protection substrate, enhancing the adhesion between the substrates, thereby producing recycled lead tailings slope protection material. When applying, spray the slope protection material evenly onto the protected slope surface (spray grass seeds and cultivate and maintain them according to plant growth standards).

[0020] Example 3

[0021] Slope protection material composition: 28.6% recycled heavy metal slag, 71.4% natural soil, 10% fine weathered sand, 2.0% sodium alginate (II), 20% peat, 6% turf, and 2% humus; preparation: Step S1: Take heavy metal ore mercury and cadmium (containing Hg) 2+ Cd 2+28.6% of the zinc and cadmium tailings were screened using a 0.5mm sieve to remove large particles and impurities. Water (liquid-solid ratio 5:1) was added to the zinc and cadmium tailings, and the equipment was started for initial stirring. Then, 0.2% of dithiocarbamate-DTCR (DTCR) was added to the zinc and cadmium tailings and mixed in a forced mixer. The mixer, equipped with automatic control, improved mixing efficiency and uniformity, reducing the uncertainty of manual operation. This ensured the tailings dissolved in water to form a turbid suspension, guaranteeing that the DTCR was evenly distributed in the zinc and cadmium tailings. The mixture was allowed to stand for 7 days to allow the DTCR to fully capture zinc and cadmium ions in the tailings, forming a stable chelated salt flocculent precipitate. After 7 days, the water was removed, and all the chelated tailings precipitate was collected, dried, and used as recycled zinc-cadmium tailings aggregate. Step S2: Take 71.4% of the original soil from the construction site and the surrounding wilderness soil, sieve it with a sieve size of 0.5mm, and then add it to the above-mentioned prepared recycled zinc and cadmium tailings aggregate to form a mixture base material. Step S3: Add 10% fine weathered sand, 2.0% sodium alginate (II), 20% peat, 6% sphagnum moss, and 2% humus to the mixture substrate from step S2 above. Step S4: Add water to the mixture base material from Step S3 according to the required water content of the soil in the construction area, and use a mixer for high-intensity mixing to ensure that all components are evenly distributed in a slurry state. By taking samples for testing, check whether the content of each component in the mixture is consistent to verify whether the mixing is uniform. If unevenness is found, the mixing time and intensity need to be adjusted until satisfactory uniformity is achieved. The above mixed material also needs to be left in a sealed environment at room temperature for 1 day to promote the formation of a gel network of sodium alginate (II) in the slope protection material, enhance the adhesion between materials, and thus produce recycled zinc-cadmium slag slope protection material. When applying, spray the slope protection material evenly onto the protected slope surface (spray grass seeds and cultivate and maintain them according to plant growth standards).

[0022] To verify the beneficial effects of the present invention, the following comparative experiments were conducted: Comparative Example 1 1. Tests on the capture rate and heavy metal ion content of DTCR in heavy metal mining waste in ecological slope protection substrates. Sample collection: Lead tailings, a waste product from heavy metal mining, was used as the sample. Four equal amounts of lead tailings slag, sieved through a 0.5 mm sieve, were divided into four identical beakers, A1, A2, A3, and A4, forming four groups. Water was added to each group at a liquid-to-solid ratio of 6:1, and the mixture was stirred until a suspension was formed. DTCR was then added using a siphon tube. The amount of DTCR added was 0.05% of the mass of tailings slag used in A1, 0.10% in A2, and 0.20% in A3. The mixture was stirred thoroughly with a stirring rod. A4 served as the control group without DTCR. Three reaction measurement intervals were set: 1 day, 7 days, and 30 days.

[0023] The capture rate of lead by DTCR and the content of lead ions in beakers A1, A2, and A3 were tested by X-ray fluorescence spectroscopy. The experimental results are as follows: from Figure 1 The bar chart of heavy metal ion capture rate shows that the capture rate of heavy metal ions with different dosages first increases and then decreases over time. On the first day, A1 contained 0.05% DTCR and had a heavy metal ion capture rate of 26.1%; when A2 contained 0.10% DTCR, the heavy metal ion capture rate was 32.3%; and when A3 contained 0.20% DTCR, the heavy metal ion capture rate was 37.5%.

[0024] On the seventh day, the capture rate of heavy metal ions was 43.8% for A1, 56.1% for A2, and 65.7% for A3.

[0025] On the thirtieth day, the capture rate of heavy metal ions was 39.7% for A1, 48.8% for A2, and 54.9% for A3.

[0026] from Figure 2 The heavy metal ion content-time curves show that different reaction times have a significant impact on the heavy metal content. With changing reaction time, the heavy metal ion content exhibits a trend of first decreasing and then increasing. On the first day, the heavy metal ion content in samples with different DTCR doping levels all showed a significant decreasing trend. (Pb in A1...) 2+ The content was 1.94 g / kg, compared to the Pb content in the control group A4. 2+ The Pb content in A2 decreased by 0.68 g / kg. 2+ The content was 1.77 g / kg, compared to the control group A4, where Pb was present. 2+ The concentration of Pb in A3 decreased by 0.85 g / kg. 2+ The content was 1.64 g / kg, compared to the Pb content in the control group A4. 2+ It decreased by 0.98g / kg.

[0027] For easier comparison of the data, see Table 1: Changes in heavy metal ion capture rate over time, and Table 2: Changes in heavy metal ion content over time.

[0028] Table 1 shows the change in heavy metal ion capture rate over time:

[0029] Table 2 shows the changes in heavy metal ion content over time:

[0030] Based on comprehensive consideration and experimental practice, this invention has determined that adding DTCR at 0.1% of the heavy metal tailings and a reaction time of 7 days is optimal. This is because mixing DTCR with the heavy metal tailings ensures sufficient reaction time, allowing DTCR to fully react with the heavy metal ions and form water-insoluble chelate precipitates, thereby effectively removing the heavy metal ions. A concentration of 0.05% is too low, resulting in low efficiency in capturing heavy metal ions; while a concentration of 0.2% does not show a significant improvement in chelation effect after 7 days compared to 0.1%, the cost doubles in practical applications.

[0031] 2. DTCR adaptability test in ecological slope protection substrate Sample collection: Lead tailings, a waste product from heavy metal mining, was used as the sample. Divided into groups B1, B2, and B3, each group consists of a plant cultivation box of the same size and volume, containing an equal amount of test samples. B1 contains in-situ soil from a lead tailings slag mining area, which is sieved through a sieve with a mesh size of 0.5 mm. B2 is a mixture of lead tailings and in-situ soil from the mining area, mixed in a 1:2 ratio. All samples were sieved using a 0.5mm sieve. The lead tailings were not treated with a heavy metal ion chelating agent. The mixture was mixed with 8% fine quartz sand, 20% peat, 6% sphagnum moss, 2% rice straw, and 1.0% sodium polyacrylate, a commonly used water-retaining agent. B3 is a mixture of lead tailings and in-situ soil from the mining area, mixed in a 1:2 ratio. All samples were sieved using a 0.5mm sieve. The lead tailings were treated with 0.1% of the heavy metal ion chelating agent DTCR. The mixture also contained 8% fine quartz sand, 20% peat, 6% sphagnum moss, 2% rice straw, and 1% sodium polyacrylate, a commonly used water-retaining agent. In each of the three sample groups, 120 plump and healthy ryegrass seeds were placed in each box. The seeds were pre-treated by spraying water to moisten them the day before sowing and leaving them overnight to awaken them. The prepared substrate in each box was divided into two parts. The larger part was added with an appropriate amount of water and placed in the planting box after it was completely moistened. Then, the 120 seeds were placed on top of it. Finally, the smaller part of the dry substrate was placed on top and watered evenly. Each group of planting boxes was placed near a sunny window. Due to the high indoor temperature, the planting boxes were watered daily, with the amount of water used to keep the soil moist. The planting period ended after 30 days.

[0032] like Figure 3 Average number of buds per group at different times: Group B3 performed the best. In the early stage of the experiment, the average number of buds per group was similar to that of the other two groups, but a significant increase occurred between days 5 and 7, with the average number of buds per group rapidly increasing to 95. The growth rate then slowed down, reaching about 108 on day 30, making it the group with the highest average number of buds per group among the three groups. like Figure 4 At 30 days, the average seedling length of each group was as follows: Group B1 had an average seedling length of 19.7 cm, Group B2 had an average seedling length of 18.9 cm, and Group B3 had an average seedling length of 22.5 cm. Group B3 had the largest average seedling length, Group B2 had a relatively smaller average seedling length, and Group B1 had a seedling length in the middle. like Figure 5 The maximum seedling length and root length of each group at 30 days were as follows: In group B1, the maximum seedling length was 26.3 cm and the maximum root length was 10.6 cm. In group B2, the maximum seedling length was 23.7 cm, a decrease of 9.9% compared to group B1, and the maximum root length was 9.6 cm, a decrease of 9.4% compared to group B1. In group B3, the maximum seedling length increased to 32.1 cm, an increase of 22.1% and 35.4% compared to groups B1 and B2, respectively; the maximum root length reached 18.3 cm, an increase of 72.6% and 90.6% compared to the previous two groups, respectively. like Figure 6 At 30 days, the average root length of each group was: the longest in group B3 was 10.8 cm, the middle in group B1 was 8.3 cm, and the shortest in group B2 was 5.5 cm.

[0033] This verifies that in group B3, treatment with the heavy metal chelating agent DTCR effectively removed heavy metal ions, restored and optimized the plant growth environment, and resulted in good plant growth. The regenerated heavy metal tailings slag could replace natural soil. Conversely, in group B2, heavy metal tailings slag was directly mixed with in-situ soil from the mining area without heavy metal chelating agent treatment. Despite other conditions being the same, the heavy metal pollution significantly damaged the plant growth conditions. Group B1, as the control group, did not contain organic matter or water-retaining agents, so its experimental data was slightly different from group B3, but much better than group B2, which had heavy metal pollution. The experiment in group B3 also shows that if only land restoration and management of the mining area is carried out, there are no requirements for the physical strength of the materials. Only ecological restoration and filling and leveling of the mining area are carried out as part of "soil replacement" environmental protection and management. Using commonly used water-retaining agents can also achieve good ecological restoration results and a high plant survival rate.

[0034] Comparative Example 2 Test on the effect of sodium alginate (II) on the performance of ecological slope protection substrate 1. Direct shear test Sample collection: In-situ soil samples were taken from the lead mining area. The experiment was divided into 4 groups. The soil was sieved through a 0.5mm sieve, with the same amount of soil used in each group. The moisture content was based on the natural moisture content of the local in-situ soil from the lead tailings mining area, which was 19.8%. The soil was stirred into a slurry with a sample density of 1.91 g / cm³. The groups were as follows: The C1 control group consisted of in-situ soil from the mining area. The in-situ soil from the C2 mining area was treated with 0.5% sodium alginate (II). The in-situ soil from the C3 mining area was mixed with 1.0% sodium alginate (II). The in-situ soil from the C4 mining area was mixed with 2.0% sodium alginate (II). All four soil samples were placed in sealed bags for one day, and the samples were prepared and tested on the second day. Each sample was tested on a four-unit strain gauge controlled direct shear apparatus with normal pressures of 50 kPa, 100 kPa, 150 kPa, and 200 kPa. The shear apparatus was used to obtain the degree of the stress ring, and the shear stress data was obtained by the formula τ = C × R. The τ-ΔL relationship curve was plotted with the shear stress τ as the ordinate and the shear displacement ΔL as the abscissa. Since no peak value was found in this test, the τ value corresponding to ΔL = 4 mm was taken as the shear strength. Finally, φ and c were calculated by the least squares method.

[0035] like Figure 7 The dosage-cohesive change curve shows that as the dosage of sodium alginate (II) increases, the cohesive force inside the sample shows an upward trend.

[0036] C1: When the sodium alginate (II) content is "zero", the cohesive force is 17.3 kPa; C2: When the sodium alginate (II) content increased to 0.5%, the cohesive force rose to 21.2 kPa, which was 22.5% higher than when the sodium alginate (II) content was "zero". C3: When the dosage increased to 1.0%, the cohesive strength rose to 25.5 kPa, which was 20.3% higher than when the sodium alginate (II) dosage was 0.5%. C4: When the sodium alginate (II) content is 2.0%, the cohesive force reaches approximately 31 kPa, which is 17.7% higher than when the sodium alginate (II) content is 1.0%. like Figure 8 The content-internal friction angle change curve shows that as the content of sodium alginate (II) gradually increases, the internal friction angle between soil particles also increases synchronously. However, it is worth noting that the growth rate of the internal friction angle is not linear, but rather accelerates first and then slows down. like Figure 9 The fitting curves of sodium alginate (II) content versus shear strength show that, under the same normal stress, the shear strength fitting curve of group C4 with 2.0% sodium alginate content is always at the top, while the shear strength fitting curve of group C1 without sodium alginate (II) content is always at the bottom, and groups C2 and C3 with other content are in the middle. This indicates that the addition of sodium alginate (II) content has different positive effects on the shear strength of soil samples. With the increase of sodium alginate (II) content, not only is the shear strength of the sample significantly improved, but the cohesion and internal friction angle of the soil are also significantly improved.

[0037] 2. Disintegration test The sampling, grouping, and experimental conditions are the same as those for the direct shear test in section 1 above.

[0038] like Figure 10 The curves showing the relationship between dosage and average disintegration rate reveal that the average disintegration rates of the four groups, from highest to lowest, are: Group C1 > Group C2 > Group C3 > Group C4. When the sodium alginate (II) dosage is 0%, the average disintegration rate of the sample is 1.088 g / min. When the sodium alginate (II) dosage is 0.5%, the average disintegration rate is 1.057 g / min, a decrease of 2.8% compared to 0%. When the sodium alginate (II) dosage is 1.0%, the average disintegration rate is 0.973 g / min, a decrease of 10.6% compared to 0%. When the sodium alginate (II) dosage is 2.0%, the average disintegration rate is 0.881 g / min, a decrease of 19.1% compared to 0%. like Figure 11The curve showing the relationship between dosage and disintegration rate at the same time shows that as the dosage of sodium alginate (II) increases, the disintegration rate of the sample at the same time shows a downward trend.

[0039] The above experiments fully demonstrate that the bonding and water-retaining agent sodium alginate (II) used in this invention forms a hydrogen bond network with soil particles. By establishing a continuous gel network, it enhances the adhesion and cohesion between substrates and reduces the soil disintegration rate. Considering the effects of adding 0.5%, 1.0%, and 2.0% sodium alginate (II), adding 1.0% sodium alginate (II) to the soil provides a good balance between enhancing adhesion and water retention. It improves the stability of the substrate while ensuring the water conditions required for plant growth, accelerating cell division in the meristematic zone and cell expansion in the elongation zone, and improving root vitality. Overall, it achieves a relatively ideal balance between effectiveness and cost. 0.5% has insufficient impact on the soil, while 2.0% has a sufficiently strong impact but is also more expensive and may lead to an overly dense gel network, affecting soil permeability and negatively impacting normal plant root growth.

[0040] Comparative Example 3 The performance of the ecological slope protection substrate of the present invention under simulated natural environmental conditions such as different slopes and rainfall: The experiment lasted for three days from start to finish, with slopes of 40°, 50°, and 60° set up to simulate the rain erosion test on steep exposed mining slopes, verifying the rain erosion resistance of the recycled heavy metal tailings slope protection material on steep slopes. To simulate different actual conditions, five test groups were set up, as shown in Table 3. The slope protection material was prepared according to the process of Example 2. The slope protection material was placed in a simulated slope protection engineering material test box with dimensions of 100cm×100cm×8cm. A layer of dense wire mesh was laid at the bottom of the box, and the slope protection material was evenly sprayed on it. Then, depending on whether plants were sown, cultivation was carried out.

[0041] Table 3 Grouping of Rainfall Erosion Tests

[0042] Group D1 was a control group consisting of in-situ soil from the mining area without any added components; Group D2 was a recycled lead tailings slope protection material made with the components of this invention, but without spraying ryegrass seeds; Group D3 was in-situ soil from the mining area without any added components, but with ryegrass seeds sprayed at a density of 10 g / m²; Group D4 simulated the production of the slope protection material of this invention, except that sodium alginate (II) was not used, but the commonly used water-retaining agent sodium polyacrylate was added, and ryegrass seeds were sprayed at a density of 10 g / m²; Group D5 completely simulated the on-site construction scenario of the recycled lead tailings slope protection material made with the components of this invention, with ryegrass seeds sprayed at a density of 10 g / m².

[0043] Slopes of 40°, 50° and 60° were set up, and samples of each group were placed in their respective experimental boxes in equal quantities. A simulated rainfall facility was then set up.

[0044] The sediment loss and runoff volume are collected by a collection device. The erosion resistance index is calculated using the runoff rate formula and the sediment loss rate formula, as follows: Q = V / (A × t) × 100% In the formula: Q: runoff rate, % V: Runoff volume, m 3 A: Water flow area, m 2 t: flushing time, min V_t=M / t Where: V_t: sediment loss rate, g / min M: Mass of lost sediment, g t: flushing time, min from Figure 12 The total runoff under different slope conditions shows that: after 1 hour of rainwater runoff, groups D1 and D3 had relatively high total runoff volumes among the five groups under different slope angles, indicating that these two groups had poor water retention capacity. At a slope angle of 40°, the total runoff volume reached approximately 30L; at 50°, it was approximately 24L; and at 60°, it was approximately 18L. This is mainly because the slope protection capacity of simulated natural soil without any added materials, both with and without vegetation, was relatively weak. Compared to the above two groups, groups D2, D4, and D5, simulating the slope protection material of this invention, had relatively better water retention capacity. The total runoff volume decreased with increasing slope angle, and under the same slope angle, the total runoff volume was not significantly different. However, because D4 used a common water-retaining agent, its total runoff volume was still higher than that of groups D2 and D5 as the slope became steeper, indicating that its material structure was not effectively strengthened. from Figure 13The total alluvial volume under different slope conditions shows that, under the same slope gradient, the total alluvial volume varies significantly. At a slope of 40°, the total alluvial volume of group D1 is approximately 2300g, while that of group D3 is approximately 1100g. Group D1's total alluvial volume is about 2.1 times that of group D3. This is because the plant root system in group D3 provides some resistance to rainwater erosion. Group D5's total alluvial volume is approximately 160g, while that of group D1 is about 14.3 times that of group D5. This is because group D5 uses both the slope protection substrate of this invention and planted vegetation, resulting in the strongest slope protection capability. Under different slope gradients, the total alluvial volume of groups D1 and D3 shows a consistent trend, increasing with slope gradient. Group D4, using a common water-retaining agent, also shows an increase in total alluvial volume with increasing slope gradient. However, the total alluvial volume of groups D2 and D5 does not change significantly with increasing slope gradient. Therefore, in the experiment simulating natural environment slope protection, groups D2 and D5, which used the recycled heavy metal tailings slope protection material of this invention, showed that their overall slope protection ability was far superior to that of other groups that did not use the slope protection material of this invention. The plants in group D4, which used ordinary water-retaining agent, grew normally, but their slope protection ability decreased significantly with the increase of slope, and their resistance to rainwater impact was significantly lower than that of groups D2 and D5, which used sodium alginate (II). This also shows that it will play a more positive role in the restoration and replacement of mining land and environmental management. Group D5 simulated the composition and preparation of the recycled heavy metal tailings slope protection material of this invention throughout the entire process and sprayed ryegrass seeds according to the requirements of the construction site. The plants grew normally. The comprehensive factors such as the material, components, and well-developed plant root system made the overall data of group D5 show that the slope protection efficiency was the best. Group D2, which did not plant any plants, was second best. Group D4, which used ordinary water-retaining agent, was in the middle. Group D3, which planted grass in situ, was the worst, and Group D1, which did not plant grass, was the worst.

[0045] Through comprehensive evaluation of the above embodiments and comparative experiments, this invention, based on experiments and practice, proposes a recycled heavy metal slope protection material and its preparation method. This material uses a mixture of heavy metal tailings aggregate and natural soil in a specific ratio as the main substrate. The addition of an appropriate amount of heavy metal chelating agent solves the pollution and hazard problems of heavy metal ions in the substrate, saving natural soil consumption. Furthermore, the combination of appropriate amounts of fine aggregate, structural nutrient improvement materials, and binding and water-retaining agents optimizes the physical strength, water retention, nutrient, and ecological adaptability of the slope protection material. This not only effectively utilizes industrial waste resources, reduces the environmental burden, and improves socio-economic benefits, but also, by precisely controlling the proportions and addition times of various additives, enables the slope protection material to quickly form a stable structure and achieve the slope protection effect for steep exposed mining slopes in a short time. It is particularly advantageous for the protection and ecological restoration of steep slopes. Because this invention also demonstrates good economic and social benefits in practical applications, it can recycle industrial waste, save a large amount of natural resources, and reduce maintenance costs, thus providing strong support for green and sustainable development.

[0046] This specific embodiment is merely an explanation of the invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection of this invention, they are protected by patent law.

Claims

1. A recycled heavy metal tailings slag slope protection material, characterized in that, include: The composition includes recycled heavy metal tailings aggregate, natural soil, fine aggregate, binder and moisture retainer, structural nutrient regulator, and water. The recycled heavy metal tailings aggregate is prepared by removing heavy metal ions from the tailings using a heavy metal chelating agent. The natural soil is one or more types of soil from the waste heavy metal mining area or the surrounding wilderness area. The recycled heavy metal tailings aggregate is mixed with the natural soil as the base material. The fine aggregate is fine sand. The binder and moisture retainer is industrial-grade sodium alginate for increased viscosity. The structural nutrient regulator is organic matter. The water is added according to the required amount based on the natural soil moisture content of the slope protection project site.

2. The slope protection material according to claim 1, characterized in that, The recycled heavy metal tailings aggregate includes one or more recycled tailings of lead, zinc, copper, cadmium, mercury, manganese, nickel, and chromium.

3. The slope protection material according to claim 1, characterized in that, The heavy metal chelating agent is: dithiocarbamate.

4. The slope protection material according to claim 3, characterized in that, The dithiocarbamate is used to remove heavy metal ions at a dosage of 0.05% to 0.2% of the heavy metal tailings slag.

5. The slope protection material according to claim 1, characterized in that, The recycled heavy metal tailings slag aggregate is mixed with natural soil as the base material, with a mixing ratio of 1:1.5-2.

5.

6. The slope protection material according to claim 1, characterized in that, The fine sand is a type of quartz sand or weathered sand, with a particle size of 0.1–0.5 mm, and is added at 5%–10% of the mixed substrate of the recycled heavy metal tailings slag aggregate and natural soil.

7. The slope protection material according to claim 1, characterized in that, The industrial-grade sodium alginate with enhanced viscosity has a viscosity greater than 2000 cps, and the amount added is 0.5% to 2.0% of the mixed substrate of the recycled heavy metal tailings slag aggregate and natural soil.

8. The slope protection material according to claim 1, characterized in that, The organic matter includes one or more of the following: peat, sphagnum moss, rice straw, wood chips, and humus; the amount added is 28% of the mixture of the recycled heavy metal tailings aggregate and the natural soil substrate.

9. The method for preparing the slope protection material according to any one of claims 1-8, characterized in that: Step S1: According to the actual needs of the slope protection project, take heavy metal tailings slag, add water and stir evenly. The liquid-solid mass ratio of water to slag is 4-6:

1. Then add 0.05% to 0.2% of the amount of heavy metal tailings slag as a heavy metal chelating agent dithiocarbamate, stir evenly again, and let stand for 7 days. After 7 days, remove the water, keep all the heavy metal tailings slag precipitate, and dry it as recycled heavy metal tailings slag aggregate for later use. Step S2: Mix the above-mentioned spare recycled heavy metal tailings slag aggregate with the selected natural soil to form a base material. The mass mixing ratio of slag aggregate and soil is 1:1.5-2.

5. Step S3: Fine sand, industrial-grade sodium alginate for enhanced viscosity, and organic matter are added to the substrate from step S2. The amounts of fine sand added are 5% to 10% of the substrate weight, sodium alginate added are 0.5% to 2.0% of the substrate weight, and organic matter added are 28% of the substrate weight. Step S4: According to the natural moisture content of the soil in the area where the ecological slope protection project is implemented, add the required water to the substrate that has been mixed with fine sand, industrial-grade sodium alginate and organic matter in S3, stir evenly to form a slurry, and place the material in a closed environment at room temperature for one day to make recycled heavy metal tailings slag slope protection material; according to the requirements of the slope protection project, spray the slope protection material evenly onto the protected slope surface.

10. The method for preparing the slope protection material according to claim 9, characterized in that: The recycled heavy metal tailings aggregate and natural soil were screened using a 0.5 mm standard sieve before mixing, and the particle size was controlled within the range of 0.4–0.6 mm after sieving.

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