Multi-source solid waste composite type soil-like substrate and mine ecological restoration method

Abstract

This invention belongs to the field of mine ecological restoration technology, specifically relating to a multi-source solid waste composite soil-like matrix and a method for mine ecological restoration. It includes a support and conditioning layer and an ecological engine layer. The support and conditioning layer is laid on the damaged mine foundation, and the ecological engine layer is laid on top of the support and conditioning layer. The support and conditioning layer prevents the collapse and erosion of the entire restoration structure, while the ecological engine layer continuously drives vegetation growth. The combination of these two layers solves the problem of easy failure of single-layer structures, ensuring long-term stability. An in-situ activator slowly releases signaling substances and nutrients, migrating from the upper to the lower layers, activating inert elements in the lower layers, forming an expanded rhizosphere micro-ecosystem spanning both layers. This invention utilizes local solid waste from mining operations for long-term and effective mine ecological restoration, achieving multiple goals of waste-to-waste treatment, mine ecological restoration, and solid waste resource utilization. The method is simple, easy to implement, and suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of mine ecological restoration technology, specifically relating to a multi-source solid waste composite soil matrix and a mine ecological restoration method. Background Technology

[0002] Mining activities generate large amounts of solid waste, such as coal gangue and tailings produced during coal mining. This solid waste not only occupies a large amount of land but also poses environmental risks such as landslides, dust storms, and heavy metal pollution. At the same time, mining also severely damages the original landform and soil structure, leading to vegetation loss and ecosystem degradation.

[0003] Traditional mine ecological restoration methods mainly include the topsoil method, which involves transporting high-quality soil from elsewhere to cover the damaged area. This method suffers from problems such as damaging new sites during soil extraction, high costs, and significant carbon emissions during transportation. Utilizing local solid waste for restoration is an ideal approach, but single solid wastes often suffer from poor structure and nutrient deficiency. For example, coal tailings have a dense structure and poor permeability; coal gangue is highly acidic and low in nutrients; and fly ash is too loose and has poor water and fertilizer retention capacity. While existing technologies have attempted to mix two or three types of solid waste, these are mostly simple physical blending methods, resulting in a homogeneous matrix structure and poor restoration effects. Another approach focuses on landfilling and physical stabilization, lacking ecological function design. Therefore, how to effectively restore mine ecology using local solid waste generated from mining is a challenge that needs to be overcome. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a multi-source solid waste composite soil-like matrix and a method for mine ecological restoration. The multi-source solid waste composite soil-like matrix provided by this invention has a gradient functional structure and in-situ activation capability. This matrix is ​​not a homogeneous mixture, but a biomimetic ecosystem in which physical structure, chemical properties, and biological functions change in a gradient from bottom to top, thereby achieving an unexpected restoration effect that is completely different from that of a single mixture.

[0005] The core concept of this invention is to design the remediation body as a two-layer structure of a support conditioning layer and an ecological engine layer, and to trigger the synergistic effect between the two layers through a specific in-situ activator to form a stable and vibrant soil-like profile.

[0006] This invention is specifically implemented through the following technical solutions: The first objective of this invention is to provide a multi-source solid waste composite soil-like matrix, comprising a support conditioning layer and an ecological engine layer.

[0007] The supporting conditioning layer is laid on the damaged base of the mine and is made of the following raw materials by mass percentage: 40%~60% coal mine tailings, 20%~40% crushed coal gangue, 3%~8% quicklime, and the balance is fly ash, totaling 100%.

[0008] The ecological engine layer is laid on the support conditioning layer and is made of the following raw materials by weight percentage: 40%~60% urban sludge compost, 20%~30% plant fiber material, and the remainder is in-situ activator, totaling 100%.

[0009] The in-situ activator uses fly ash-based porous ceramic microspheres as a carrier, loaded with humic acid and magnesium ammonium phosphate to form an intermediate structure, and coated with a biochar layer on the outer layer of the intermediate structure.

[0010] The thickness ratio of the support conditioning layer to the ecological engine layer is 1~3:1.

[0011] It should be noted that, as Figure 1 As shown, the supporting conditioning layer acts as a foundation, preventing the collapse and erosion of the entire restoration; the ecological engine layer continuously drives vegetation growth. The combination of these two layers solves the problem of easy failure in single-layer structures, ensuring long-term stability. In-situ activators slowly release signaling substances and nutrients that migrate from the upper to the lower layers, activating inert elements in the lower layers and forming an expanded rhizosphere micro-ecosystem spanning two layers. This effect cannot be achieved with simple mixtures or ordinary layered structures, giving the system self-sustaining capabilities.

[0012] Specifically, the support and conditioning layer comprises framework particles, microporous materials, and pH conditioners. The framework particles are solid particles with high strength and large particle size. Their function is to form a stable physical framework within the matrix, creating and maintaining large pore channels to ensure the restoration has good water permeability, air permeability, and resistance to compression deformation, preventing matrix compaction. In this invention, the framework particles refer to coal mine tailings and gangue that have undergone crushing and screening. Coal mine tailings particles have sharp edges and strong interlocking ability; coal gangue particles themselves have a certain porosity. Together, they construct the macroscopic framework structure of the support and conditioning layer. Furthermore, to prevent spontaneous combustion of coal gangue, this invention prepares a flame-retardant layer on the surface of the coal gangue. The microporous materials are lightweight materials with abundant nano- to micron-sized internal pores. Their function is to adsorb and retain moisture, adsorb nutrient ions such as ammonium nitrogen, and provide a microenvironment for microbial attachment. In this invention, the microporous material refers to fly ash, whose unique spherical glass microsphere structure endows it with a huge specific surface area and pore volume. It can effectively regulate the water, fertilizer, air, and heat conditions of the supporting conditioning layer, acting like a miniature reservoir and nutrient transfer station, and complements the macroporous structure of the framework particles. The pH conditioner is used to rapidly neutralize the extreme acidity of the mine substrate, creating a suitable living environment for microorganisms and plant roots. Quicklime is preferred in this invention (for acidic substrates).

[0013] The ecological engine layer consists of a nutrient source, a fiber network, and an in-situ activator. Urban sludge compost provides the nutrient source, and the fiber network, formed by plant fibers, is not only a filler in the ecological engine layer but also a key structure for building the rhizosphere microenvironment, forming a three-dimensional network to regulate water and air. The in-situ activator uses fly ash-based porous ceramic microspheres as a carrier, loaded with humic acid and magnesium ammonium phosphate to form an intermediate structure. A biochar layer coats the outer layer of this intermediate structure. The in-situ activator slowly releases signaling substances and nutrients, supporting the slow release of H+ from the coal gangue in the conditioning layer during weathering and neutralization. + This creates a weakly acidic local microenvironment. When the in-situ activator particles of this invention are in this environment, the outer alkaline biochar coating layer will first undergo a neutralization reaction and gradually be consumed and disintegrated, thereby triggering the release of nutrients from the inner layer. The tailings in the support and conditioning layer typically contain metal oxides such as Fe, Mn, and Al. The specially formulated fly ash porous ceramic carrier of this invention contains semiconductor phases (such as Fe2O3) after sintering. When moisture is present, a weak galvanic cell electric field effect is formed between the biochar (electron donor) and the tailings particles (electron acceptor). This micro-electric field can drive negatively charged humic acid molecules to migrate more effectively into the depth of the support and conditioning layer after being released from the activator. To ensure that the system contains water, the system is watered during the repair process, especially in the early stages, to promote the release of nutrients. It should be noted that the role of quicklime in the support conditioning layer is to neutralize the extreme acidity of the mine base. Its dosage can be added according to actual conditions to avoid excessive amounts affecting the H₂ released from the coal gangue during weathering and neutralization. + This causes interference. First, use quicklime to neutralize the extremely acidic environment of the mine base. In the initial stage, some of the H in the base... + It will be neutralized by quicklime and will consume quicklime; some H will also be present in the substrate. + The escape of quicklime neutralizes the precipitate and acts as a starting signal to activate the aforementioned in-situ activator, causing the nutrients in the inner layer to begin to be released.

[0014] In a preferred embodiment of the present invention, the method for preparing the in-situ activator includes the following steps: Fly ash-based porous ceramic microspheres were prepared by mixing fly ash, clay, and sodium bicarbonate pore-forming agent, adding water, granulating, and then sintering.

[0015] Humic acid and struvite were mixed to form a solution; the solution was then adsorbed into the pores of the fly ash-based porous ceramic microspheres using a vacuum impregnation method to obtain an intermediate structure. It should be noted that magnesium ammonium phosphate is struvite, an excellent slow-release phosphorus and nitrogen source, recovered from anaerobic digestion sludge, demonstrating the synergistic utilization of multiple solid waste sources.

[0016] The intermediate structure and sludge biochar powder are mixed and rolled under the action of a binder to form a uniform biochar coating layer, thus obtaining an in-situ activator.

[0017] In a preferred embodiment of the present invention, in the preparation step of fly ash-based porous ceramic microspheres, water is added to granulate into 3mm~5mm microspheres. In the mixture composed of fly ash, clay and sodium bicarbonate pore-forming agent, the mass fraction of fly ash is 80%~85%, clay is 10%~15%, and the balance is sodium bicarbonate pore-forming agent, totaling 100%. The sintering temperature is 1100℃~1200℃, and the sintering time is 40min~60min.

[0018] In a preferred embodiment of the present invention, the mass ratio of humic acid to struvite is 1:1 to 1.5.

[0019] In a preferred embodiment of the present invention, the sludge biochar powder is sludge biochar powder that has passed through a 200-mesh sieve, the mass ratio of the intermediate structure to the sludge biochar powder is 3~4:1, the binder is an aqueous solution of carboxymethyl cellulose, and the particle size of the in-situ activator formed is 4mm~6mm.

[0020] In a preferred embodiment of the present invention, the particle size of the coal mine tailings is 8mm~10mm. To prevent spontaneous combustion of the coal gangue, a flame-retardant layer is prepared on the surface of the coal gangue. The coal gangue is impregnated in a flame-retardant slurry and then dried. The flame-retardant slurry is prepared by mixing fly ash, lime, cement, water glass, and water. The mass ratio of fly ash, lime, and cement is 2~4:1~2:1. The mass of water glass added is 1%~5% of the mass of fly ash. The total mass concentration of fly ash, lime, and cement in the flame-retardant slurry is 60%~70%. The particle size of the flame-retardant modified coal gangue is 5mm~20mm.

[0021] In a preferred embodiment of the present invention, the plant fiber material is cotton stalk or reed dust, with a fiber length of 3mm to 15mm and an aspect ratio of 10 to 15.

[0022] The second objective of this invention is to provide a method for mine ecological restoration, comprising the following steps: Dry mixtures of the support conditioning layer and the ecological engine layer were prepared separately. On the site to be repaired, first lay the support and conditioning layer and compact it; then lay the ecological engine layer and lightly compact it. After laying, watering and curing will trigger the in-situ activator to start working.

[0023] Compared with the prior art, the present invention has the following beneficial effects: This invention breaks away from the traditional approach of treating solid waste as a homogeneous material, proposing a gradient functional structure of a support and conditioning layer and an ecological engine layer. It simulates the subsoil-topsoil profile of natural soil, with the lower support and conditioning layer focusing on structural stability and moisture regulation, and the upper ecological engine layer focusing on nutrient supply and biological activity. This invention introduces an in-situ activator into the aforementioned support and conditioning layer-ecological engine layer. This activator is not a common fertilizer or microbial agent, but a smart-release system initiator. Through the slow-release of humic acid and magnesium ammonium phosphate, it actively establishes chemical and biological connections between the two layers, achieving interlayer synergy rather than simple layering.

[0024] The supporting conditioning layer acts as a foundation, preventing the collapse and erosion of the entire restoration; the ecological engine layer continuously drives vegetation growth. The combination of these two layers solves the problem of single-layer structures being prone to failure, ensuring long-term stability. In-situ activators slowly release signaling substances and nutrients that migrate from the upper to the lower layers, activating inert elements such as phosphorus and potassium in the lower layers, forming an expanded rhizosphere micro-ecosystem spanning two layers. In the presence of water, a weak galvanic cell electric field effect is formed between biochar (electron donor) and tailings particles (electron acceptor). This micro-electric field drives negatively charged humic acid molecules to migrate more effectively into the depths of the supporting conditioning layer after being released from the activator. Furthermore, the coal gangue in the supporting conditioning layer slowly releases H₂ during weathering and neutralization. + This creates a weakly acidic local microenvironment. When the activator particles of this invention are in this environment, their outer alkaline biochar coating layer will first undergo a neutralization reaction and gradually be consumed and disintegrated, thereby triggering the release of nutrients from the inner layer. Additionally, in the initial stage of repair, some H in the substrate... + It will be neutralized by quicklime and will consume quicklime; some H will also be present in the substrate. + The escape of quicklime neutralizes the nutrients and acts as a starting signal, initiating the release of inner-layer nutrients by the aforementioned in-situ activator. The effects of this in-situ activator are unattainable with simple mixtures or ordinary layered structures, giving the system self-sustaining capabilities. The pH regulator in the support conditioning layer continuously neutralizes acidity in the lower layers, while humic acid integrates heavy metals, significantly improving plant survival rates under stress conditions. Magnesium ammonium phosphate provides a slow-release source of phosphorus and nitrogen.

[0025] This invention provides a solid waste-based ecological restoration material that can simulate the structure of natural soil profiles and has self-sustaining and stress-resistant capabilities. It utilizes local solid waste from mining to carry out long-term and effective restoration of the mine ecology, achieving multiple goals of waste-to-waste treatment, mine ecological restoration, and solid waste resource utilization. Furthermore, the method is simple, easy to implement, and suitable for widespread application. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the mechanism of the mine ecological restoration method provided by the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.

[0028] Preparation Example 1 The preparation method of the in-situ activator includes the following steps: (1) Fly ash, clay and sodium bicarbonate pore-forming agent are mixed. The mass fraction of fly ash is 80%, clay is 15%, and the remainder is sodium bicarbonate pore-forming agent. After adding water to granulate into small balls with an average particle size of 4 mm, the temperature is raised to 1100℃ for sintering. The sintering time is 60 min to prepare fly ash-based porous ceramic microspheres.

[0029] (2) Humic acid and struvite are mixed to form a saturated mixture with a mass ratio of 1:1. Under vacuum conditions, fly ash-based porous ceramic microspheres are placed in the mixture to allow the mixture to be adsorbed into the pores of the fly ash-based porous ceramic microspheres, thus obtaining an intermediate structure.

[0030] (3) The dried intermediate structure and the sludge biochar powder that has passed through a 200-mesh sieve are mixed in a sugar coating machine at a mass ratio of 3:1. A 5% carboxymethyl cellulose aqueous solution is sprayed as a binder and rolled to form a uniform biochar coating layer, finally obtaining in-situ activator particles with a diameter of 4mm~6mm.

[0031] Preparation Example 2 The preparation method of the in-situ activator includes the following steps: (1) Fly ash, clay and sodium bicarbonate pore-forming agent are mixed. The mass fraction of fly ash is 85%, clay is 10%, and the remainder is sodium bicarbonate pore-forming agent. After adding water to granulate into 3 mm balls, the temperature is raised to 1100℃ for sintering. The sintering time is 40 min to prepare fly ash based porous ceramic microspheres.

[0032] (2) Prepare a saturated mixture of humic acid and struvite, with a mass ratio of 1:1.5. Use a vacuum impregnation method to adsorb the mixture into the pores of the fly ash-based porous ceramic microspheres to obtain an intermediate structure.

[0033] (3) The dried intermediate structure and the sludge biochar powder that has passed through a 200-mesh sieve are mixed in a sugar coating machine at a mass ratio of 4:1. A 5% carboxymethyl cellulose aqueous solution is sprayed as a binder and rolled to form a uniform biochar coating layer, finally obtaining in-situ activator particles with a diameter of 4mm~6mm.

[0034] The in-situ activator prepared in Example 1 will be used in the following examples and comparative examples. The plant fiber materials used in the following examples and comparative examples are cotton stalks and reed dust, with fiber lengths of 3-15 mm and aspect ratios of 10-15. The coal gangue is modified coal gangue after flame retardant modification. The flame retardant modification method is as follows: the coal gangue is impregnated in a flame retardant slurry and then dried. The flame retardant slurry is prepared by mixing fly ash, lime, cement, water glass, and water. The mass ratio of fly ash, lime, and cement is 4:2:1, and the added mass of water glass is 4% of the mass of fly ash. The total mass concentration of fly ash, lime, and cement in the flame retardant slurry is 65%, and the particle size of the flame-retardant modified coal gangue is 10 mm-15 mm.

[0035] Example 1 A method for ecological restoration of mines includes the following steps: Step 1: Mix the raw materials according to the following mass percentages to prepare the mixture for the support and conditioning layer: 50% coal tailings, 30% coal gangue, 3% quicklime, and the remainder is fly ash, totaling 100%.

[0036] Mix the raw materials according to the following mass percentages to prepare the mixture for the ecological engine layer: 50% urban sludge compost, 30% plant fiber material, and the remainder is an in-situ activator, totaling 100%.

[0037] Step 2: On the simulated acidic tailings substrate (pH≈4.5), first lay a support conditioning layer, compact it, and make it 10cm thick; then lay the ecological engine layer, lightly compact it, and make it 10cm thick.

[0038] Step 3: After laying, water and cure to trigger the in-situ activator to start working.

[0039] Example 2 A method for ecological restoration of mines includes the following steps: Step 1: Mix the raw materials according to the following mass percentages to prepare the mixture for the support and conditioning layer: 40% coal tailings, 40% coal gangue, 8% quicklime, and the remainder is fly ash, totaling 100%.

[0040] Mix the raw materials according to the following mass percentages to prepare the mixture for the ecological engine layer: 60% urban sludge compost, 30% plant fiber material, and the remainder is an in-situ activator, totaling 100%. Step 2: On the simulated acidic tailings substrate (pH≈4.5), first lay a support conditioning layer, compact it, and make it 10cm thick; then lay the ecological engine layer, lightly compact it, and make it 10cm thick.

[0041] Step 3: After laying, water and cure to trigger the in-situ activator to start working.

[0042] Example 3 A method for ecological restoration of mines includes the following steps: Step 1: Mix the raw materials according to the following mass percentages to prepare the mixture for the support and conditioning layer: 60% coal mine tailings, 20% crushed coal gangue, 8% quicklime, and the remainder is fly ash, totaling 100%.

[0043] Mix the raw materials according to the following mass percentages to prepare the mixture for the ecological engine layer: 40% urban sludge compost, 30% plant fiber material, and the remainder is an in-situ activator, totaling 100%. Step 2: On the simulated acidic tailings substrate (pH≈4.5), first lay a support conditioning layer, compact it, and make it 10cm thick; then lay the ecological engine layer, lightly compact it, and make it 10cm thick.

[0044] Step 3: After laying, water and cure to trigger the in-situ activator to start working.

[0045] Example 4 A method for ecological restoration of mines includes the following steps: Step 1: Mix the raw materials according to the following mass percentages to prepare the mixture for the support and conditioning layer: 55% coal mine tailings, 20% crushed coal gangue, 4% quicklime, and the remainder is fly ash, totaling 100%.

[0046] Mix the raw materials according to the following mass percentages to prepare the mixture for the ecological engine layer: 60% urban sludge compost, 20% plant fiber material, and the remainder is an in-situ activator, totaling 100%. Step 2: On the simulated acidic tailings substrate (pH≈4.5), first lay a support conditioning layer, compact it, and make it 10cm thick; then lay the ecological engine layer, lightly compact it, and make it 10cm thick.

[0047] Step 3: After laying, water and cure to trigger the in-situ activator to start working.

[0048] Ryegrass was uniformly sown on the soils prepared in the above embodiments, and measurements were taken after 90 days of cultivation under the same conditions. The results of the following indicators were obtained by testing using the following methods: The bulk density was determined using the ring cutter method. Total porosity was calculated based on the measured bulk density and the specific gravity of each matrix component (measured using a hydrometer bottle method), using the formula: Total porosity (%) = (1 - bulk density / average specific gravity) × 100%. The content of water-stable aggregates (>0.25 mm) was determined using the wet sieving method: the air-dried matrix sample was placed on a set of sieves with decreasing pore sizes from top to bottom (top 0.25 mm), shaken in water, and then the aggregates on each sieve were collected and dried. The percentage of aggregates larger than 0.25 mm in the total sample mass was calculated. Organic matter was determined using the potassium dichromate external heating method, available phosphorus was determined using the sodium bicarbonate extraction-molybdenum antimony colorimetric method, and available potassium was determined using the ammonium acetate extraction-flame photometry method. At the end of the experiment, each group of plants was cut off at the matrix surface to separate the aboveground parts from the roots. After carefully rinsing to remove the attached substrate, the roots, along with the above-ground parts, were blanched at 105°C for 30 minutes, then dried at 65°C to constant weight, and the dry weight was measured using an analytical balance. Average root depth: At harvest, the entire soil column was carefully removed, and the vertical distance from the substrate surface to the deepest visible root tip was measured using a ruler. At least five representative roots were measured in each replicate, and the average value was taken. Vegetation cover: At the end of the experiment, a grid method was used for estimation. Photos were taken perpendicular to the pot surface, and the photos were divided into 100 equal-area grids. The percentage of grids with green vegetation cover was counted.

[0049] The physical properties data are shown in Table 1.

[0050] Table 1. Material property data

[0051] The chemical properties are shown in Table 2.

[0052] Table 2 Chemical property data

[0053] Plant growth indicators are shown in Table 3.

[0054] Table 3 Plant growth indicators

[0055] To demonstrate the data effectiveness of the above embodiments of the present invention, the present invention also provides the following comparative examples.

[0056] Comparative Example 1 Compared to Example 1, only 20cm thick coal mine tailings were laid.

[0057] Comparative Example 2 Compared to Example 1, the supporting conditioning layer material and the ecological engine layer base material are simply mixed at a 1:1 volume ratio and laid in a 20cm thickness, without containing an in-situ activator.

[0058] Comparative Example 3 Compared to Example 1, the layered but ecological engine layer contains no in-situ activator.

[0059] The physical properties of Example 1 and Comparative Examples 1 to 3 are shown in Table 4.

[0060] Table 4 Material property data

[0061] The chemical properties are shown in Table 5.

[0062] Table 5 Chemical property data

[0063] Plant growth indicators are shown in Table 6.

[0064] Table 6 Plant growth indicators

[0065] As can be seen from the above data, compared with Comparative Example 1, all indicators of the present invention show an order-of-magnitude improvement, fully demonstrating the great success and absolute advantage of transforming multi-source solid waste into a soil-like matrix through the present invention. Compared with Comparative Example 2 (simple mixing), the non-obviousness of the combination of gradient structure and in-situ activator is demonstrated. Example 1 has lower bulk density, higher porosity, and higher aggregate content, indicating that the layered design effectively constructs a more stable ideal structure with a loose upper layer and a solid lower layer. The available phosphorus, available potassium, and microbial biomass carbon of Example 1 are significantly higher than those of the simple mixing in Comparative Example 2. This directly proves the interlayer synergistic effect triggered by the in-situ activator, which can more efficiently activate nutrients in the lower layer of solid waste. The aboveground and root biomass of Example 1 is about 80% higher than that of Comparative Example 2. The difference in root depth is particularly crucial: the roots of Example 1 penetrate the entire matrix layer and establish a close connection with the lower layer; while the roots of Comparative Example 2 are still mainly confined within the mixed layer. This intuitively reflects the unique advantages of the matrix of the present invention in constructing a deep and stable rhizosphere environment. Compared to Comparative Example 3 (layered without activator), the crucial role of the in-situ activator was isolated. Comparative Example 3 outperformed Comparative Example 2 in all metrics, confirming the effectiveness of the layered structure itself. However, Example 1 significantly outperformed Comparative Example 3 in terms of available phosphorus, microbial activity, and all plant growth metrics. This clearly demonstrates that the in-situ activator, acting as a system initiator, achieves deeper chemical and biological activation beyond simple physical layering through its pH-triggered release and micro-electric field-driven migration mechanism, resulting in unexpected additional growth.

[0066] This invention also tested the leaching toxicity of heavy metals: the acetic acid buffer solution method (HJ / T 300-2007) was used to simulate the leaching risk of harmful substances under acidic precipitation conditions. The concentrations of lead (Pb), cadmium (Cd), and chromium (Cr) in the leachate were determined. The results are shown in Table 7.

[0067] Table 7 Heavy metal leaching data

[0068] As shown in Table 7, the leaching concentrations of all heavy metals in Example 1 were far below the national standard limits and significantly lower than those in the original tailings (Comparative Example 1) and the simple mixture (Comparative Example 2). Crucially, the heavy metal leaching concentrations in Example 1 were even lower than those in Comparative Example 3, which only had a layered structure. The humic acid released by the in-situ activator underwent a strong complexing / chelating reaction with the metal oxides (from the tailings) in the supporting conditioning layer, fixing the heavy metals to the surface or interior of the particles. Simultaneously, the abundant organic matter in the ecological engine layer promoted the transformation of heavy metals into a more stable residual state. This multi-layered, multi-interface heavy metal stabilization mechanism reduced the risk of heavy metal leaching.

[0069] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A multi-source solid waste composite soil-like matrix, characterized in that, This includes a support conditioning layer and an ecosystem engine layer; The supporting conditioning layer is laid on the damaged base of the mine and is made of the following raw materials by mass percentage: 40%~60% coal mine tailings, 20%~40% coal gangue, 3%~8% quicklime, and the balance is fly ash, totaling 100%; The ecological engine layer is laid on top of the support and conditioning layer and is made of the following raw materials by weight percentage: 40%~60% sludge compost, 20%~30% plant fiber material, and the remainder is in-situ activator, totaling 100%; The in-situ activator uses fly ash-based porous ceramic microspheres as a carrier, loaded with humic acid and magnesium ammonium phosphate to form an intermediate structure, and coated with a biochar layer on the outer layer of the intermediate structure. The thickness ratio of the support conditioning layer to the ecological engine layer is 1~3:

1.

2. The multi-source solid waste composite soil matrix according to claim 1, characterized in that, The preparation method of the in-situ activator includes the following steps: Fly ash-based porous ceramic microspheres were prepared by mixing fly ash, clay and sodium bicarbonate pore-forming agent, adding water and granulating the mixture, and then sintering it. Humic acid and struvite were mixed to form a solution; the solution was then impregnated into the pores of the fly ash-based porous ceramic microspheres using a vacuum impregnation method to obtain an intermediate structure. The intermediate structure and sludge biochar powder are mixed and rolled under the action of a binder to form a uniform biochar coating layer, thus obtaining an in-situ activator.

3. The multi-source solid waste composite soil matrix according to claim 2, characterized in that, In the preparation steps of fly ash-based porous ceramic microspheres, water is added to granulate into 3mm~5mm small spheres. In the mixture composed of fly ash, clay and sodium bicarbonate pore-forming agent, the mass fraction of fly ash is 80%~85%, clay is 10%~15%, and the balance is sodium bicarbonate pore-forming agent, totaling 100%. The sintering temperature is 1100℃~1200℃, and the sintering time is 40min~60min.

4. The multi-source solid waste composite soil matrix according to claim 2, characterized in that, The mass ratio of humic acid to struvite is 1:1 to 1.

5.

5. The multi-source solid waste composite soil matrix according to claim 2, characterized in that, The sludge biochar powder is sludge biochar powder that has passed through a 200-mesh sieve. The mass ratio of the intermediate structure to the sludge biochar powder is 3~4:

1. The binder is an aqueous solution of carboxymethyl cellulose, and the particle size of the in-situ activator formed is 4mm~6mm.

6. The multi-source solid waste composite soil-like matrix according to claim 1, characterized in that, The particle size of coal mine tailings is 8mm~10mm.

7. The multi-source solid waste composite soil matrix according to claim 1, characterized in that, The coal gangue is a modified coal gangue after flame retardant modification. The flame retardant modification method is as follows: the coal gangue is impregnated in a flame retardant slurry and then dried. The flame retardant slurry is prepared by mixing fly ash, lime, cement, water glass and water. The mass ratio of fly ash, lime and cement is 2~4:1~2:

1. The mass of water glass added is 1%~5% of the mass of fly ash. The total mass concentration of fly ash, lime and cement in the flame retardant slurry is 60%~70%. The particle size of the flame retardant modified coal gangue is 5mm~20mm.

8. The multi-source solid waste composite soil matrix according to claim 1, characterized in that, The plant fiber material is cotton stalks or reed dust, with a fiber length of 3mm to 15mm and an aspect ratio of 10 to 15.

9. A method for ecological restoration of a mine, characterized in that, The remediation using the multi-source solid waste composite soil matrix as described in claim 1 includes the following steps: Dry mixtures of the support conditioning layer and the ecological engine layer were prepared separately. On the site to be repaired, first lay the support and conditioning layer and compact it; then lay the ecological engine layer and lightly compact it. After laying, watering and curing will trigger the in-situ activator to start working.

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