Synergistic modification method of coal gangue, modifier and application of modifier

Abstract

The invention discloses a synergistic modification method of coal gangue, a modifier and application of the modifier, and belongs to the technical field of solid waste resource utilization, the synergistic modification method comprises the following steps: 1) crushing, screening and stirring coal gangue to obtain a three-level grading system containing sand grains, powder grains and clay grains; (2) adding pyrite slag, a bacillus subtilis microbial agent, a bacillus mucilaginosus microbial agent and diatomite into the graded coal gangue treated in the step (1), uniformly mixing, and carrying out stack retting fermentation; 3) adding humic acid, fulvic acid and straw carbon into the material treated in the step 2), and uniformly mixing to obtain a water-stable aggregate, and 4) carrying out post-treatment to obtain a finished product. The method is used for solving the technical problems that the modified product has structural defects, toxic residues and insufficient fertility due to the fact that a single or local improvement strategy is mostly adopted in the existing coal gangue modification technology.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to a synergistic modification method for coal gangue, a modifier, and its application. Background Technology

[0002] Large-scale stockpiling of coal gangue not only encroaches on land resources (estimated to occupy approximately 0.5 acres per 10,000 tons of coal gangue), but also poses significant environmental and safety risks such as heavy metal leaching (e.g., Cd and Pb leaching concentrations exceeding the limits of the "Identification Standard for Hazardous Waste Leaching Toxicity Identification" (GB5085.3-2007) by 2-5 times) and spontaneous combustion (internal temperatures of the stockpile can reach above 80°C).

[0003] To promote the resource utilization of coal gangue, especially to transform it into safe soil amendment materials or cultivation substrates, existing technologies have proposed a variety of modification methods. However, these methods have many limitations, resulting in unsatisfactory performance and stability of the modified products and the comprehensive utilization rate of coal gangue (the highest rate of existing processes is 60-70%). The residual waste still needs secondary treatment, failing to fundamentally achieve the goal of efficient and safe resource utilization.

[0004] 1. Regarding physical structure modification Existing technologies, as described in patent CN201810123456.7, primarily employ simple mechanical crushing to process coal gangue into coarse particles of 5mm-10mm. This method fails to scientifically optimize the three-stage gradation of sand, powder, and clay particles, resulting in modified products with a porosity generally below 30%, poor air permeability (air porosity <10%), and weak water retention capacity (water retention rate ≤40%). Furthermore, due to the lack of adsorption by clay particles, nutrients are easily lost (loss rate >50%), and the utilization rate of the coal gangue itself is only 40-50%.

[0005] 2. Regarding chemical passivation modification In the stabilization of heavy metals, technical solutions such as those in patent CN202010789012.3 often employ a single chemical passivating agent (e.g., FeSO4). The drawback of this method is its failure to synergize with microbial remediation techniques, resulting in a short-lasting passivation effect and a risk of heavy metal reactivation over time (e.g., the reactivation rate of Cd can exceed 30% after 6 months). Furthermore, excessive Fe... 2+ It may fix available phosphorus in the soil, resulting in a low phosphorus release rate (<15%) and may cause pH imbalance in the system (<5.5), which is detrimental to plant growth.

[0006] 3. On organic matter and fertility modification To improve fertility, existing technologies, such as patent CN201920654321.5, involve adding organic matter like humic acid. However, the proportion of added organic matter is usually low (≤5%), resulting in an organic matter content of only 3-5% in the finished product. This content is insufficient to form a stable aggregate structure (water-stable aggregate content <50%) and easily leads to an imbalance in the carbon-nitrogen ratio (C / N > 40:1), causing microorganisms to compete with plants for nitrogen and affecting seedling emergence rate. More importantly, the bioavailability of heavy metals in coal gangue remains high (e.g., Cd > 50%), posing an environmental risk.

[0007] In summary, existing coal gangue modification technologies mostly employ single or partial improvement strategies, failing to form a systematic solution that can simultaneously and synergistically address physical structure, chemical toxicity, biological activity, and long-term fertility. The various process stages are fragmented and even mutually restrictive, leading to prominent problems such as structural defects, toxic residues, and insufficient fertility in modified products, severely hindering the efficient and high-value-added resource utilization of coal gangue. Summary of the Invention

[0008] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for synergistic modification of coal gangue, a modifier and its application, in order to solve the technical problems that existing coal gangue modification technologies mostly adopt single or partial modification strategies, resulting in modified products with structural defects, toxic residues and insufficient fertility.

[0009] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for converting 100% of coal gangue into ecological planting soil through a four-pronged synergistic process of physical gradation modification, chemical-microbial composite modification, organic matter enhancement modification, and finished product processing.

[0010] This invention provides a multi-scale synergistic modification method for coal gangue, comprising the following steps: 1) Physical gradation modification: The coal gangue is crushed, screened and mixed to obtain a three-level gradation system of coal gangue containing sand, powder and clay particles, so as to construct a physical framework with a stable pore structure. 2) Chemical-microbial composite modification: Pyrite slag, Bacillus subtilis inoculant, Bacillus mucilaginosus inoculant and diatomaceous earth are added to the three-stage gradation system of coal gangue after step 1). After being mixed evenly, it is composted and fermented. Through the synergistic effect of chemical passivation and microbial activation, heavy metals are fixed and nutrients are released. 3) Organic matter enhancement and modification: Humic acid, fulvic acid and straw charcoal are added to the material treated in step 2) and mixed evenly to obtain water-stable aggregates. The aggregate structure is stabilized and a microbial carbon source is provided through organic-inorganic complex interaction. 4) The water-stable agglomerates are post-processed to obtain the finished product.

[0011] Steps 1), 2), 3), and 4) together constitute a cascaded synergistic modification system that progresses from physical structure construction to chemical-biological reactions and then to the enhancement of ecological stability.

[0012] Preferably, in step 1), the coal gangue is crushed into 0.1mm-5mm particles; the three-stage gradation system comprises, by weight percentage: 40%-60% sand, 20%-30% powder, and 10%-20% clay; the porosity of the three-stage gradation system is 35%-45%.

[0013] Further preferred, the particle size of diatomaceous earth is ≤0.075mm.

[0014] Further optimized, humic acid has a humification degree ≥60%, high organic matter content, and abundant functional groups, which is conducive to the formation of granular structures, passivation of heavy metals, and enhancement of fertilizer efficiency; fulvic acid has a water solubility ≥85%, a small molecular weight, and is easily absorbed, which can stimulate crop growth, enhance stress resistance, and serve as a highly efficient nutrient carrier; straw charcoal has a specific surface area ≥300m². 2 / g, with well-developed pores, can improve soil structure, retain water and fertilizer, adsorb nutrients, and reduce loss. Its porous structure provides habitat for microorganisms. The three complement each other and work together to build an excellent soil micro-ecological environment, thereby improving soil structure, prolonging fertilizer effect, and enhancing crop stress resistance.

[0015] Further preferred, the diameter of the water-stable aggregates is 1mm-3mm, forming a natural soil aggregate structure.

[0016] In a further preferred embodiment, in step 1), the mixing conditions include: using a twin-shaft differential speed mixer with a speed of 30-50 r / min and a time of 30 min.

[0017] Preferably, the material after step 2) includes, by weight percentage: 3%-5% pyrite slag, 12%-50% Bacillus subtilis inoculant, 20%-70% Bacillus mucilaginosus inoculant, and 15%-25% diatomaceous earth.

[0018] Preferably, the effective viable count of Bacillus subtilis in the Bacillus subtilis inoculant is 1×10⁻⁶. 8 CFU / g, the effective viable count of Bacillus colloidis in the aforementioned Bacillus colloidis agent is 5 × 10⁻⁶. 7CFU / g. The Bacillus subtilis and Bacillus mucilaginosus used in this invention are conventional microbial inoculants, which can be commercially obtained from the China General Microbiological Culture Collection Center (CGMCC), the American Type Culture Collection (ATCC), or domestic biological reagent companies. As long as the above-mentioned effective viable cell count requirement is met, the same strain from any source can achieve the technical effects of this invention.

[0019] Preferably, in step 2), the conditions for composting include: adjusting the pH value to 6.5-7.5 and aging for 7-10 days.

[0020] Preferably, in step 2), the Bacillus subtilis agent and Bacillus mucilaginosus agent are injected into the graded coal gangue treated in step 1) using a high-pressure injection process, and the pressure of the high-pressure injection process is 0.5MPa-0.8MPa.

[0021] Preferably, in the water-stable aggregates obtained in step 3), the additional components, relative to the total weight of the material treated in step 2), include by weight percentage: 8%-12% humic acid, 3%-5% fulvic acid, 5%-8% straw charcoal, with the remainder being the material treated in step 2).

[0022] In a further preferred embodiment, in step 3), a high-pressure homogenization process is used for mixing, with conditions including: pressure 20 MPa and time 20 min.

[0023] In a further preferred embodiment, in step 4), the post-processing is a granulation process, and the granulation conditions include: using a disc granulator with an inclination angle of 45° to prepare 2mm-4mm particles, and controlling the moisture content to 18%-22%.

[0024] The present invention also provides a modified coal gangue soil conditioner prepared by any of the above methods, wherein the modified coal gangue soil conditioner has a passivation rate of ≥90% for heavy metals Cd and Pb and a water-stable aggregate content of ≥80%.

[0025] The present invention also provides a composite modifier composition for achieving the above-mentioned synergistic modification of coal gangue, comprising the following components: Pyrite slag, used as a chemical passivating agent; A compound microbial agent containing Bacillus subtilis and Bacillus mucilaginosus serves as a bioactivator and stabilizer; Humic acid and biochar serve as organic matter fortifiers; The composite modifier composition is used to work synergistically with coal gangue particles with a specific gradation to achieve heavy metal passivation, nutrient release, and structural construction.

[0026] The present invention also provides the application of the above-mentioned modified coal gangue soil conditioner in mine ecological restoration, heavy metal contaminated soil remediation, or as a crop cultivation substrate.

[0027] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a multi-scale synergistic modification method for coal gangue, which realizes the resource utilization of all components of coal gangue through a cascade reaction of physical gradation construction → chemical-microbial passivation → organic matter enhancement.

[0028] Through physical gradation (crushing, screening, and mixing), a three-level porous structure of sand, powder, and clay particles (porosity 35%-45%) is formed, providing channels for microbial activity and water transport, thus solving the problem of the original dense and poor permeability of coal gangue. In principle, uniform particle distribution can reduce local stress concentration and enhance matrix stability.

[0029] Through a chemical-microbial complex formed by pyrite slag, Bacillus subtilis inoculant, and Bacillus mucilaginosus inoculant, pyrite slag releases Fe. 2+ SO4 2- Heavy metals (such as Cd) can be removed through redox reactions. 2+ Pb 2 The ions are converted into insoluble sulfides (such as CdS and PbS), with a passivation rate >90%. Bacillus subtilis and Bacillus mucilaginosus inoculants secrete organic acids (such as citric acid and oxalic acid) to dissolve stored phosphorus and potassium in coal gangue, releasing available nutrients. Bacillus mucilaginosus produces extracellular polysaccharides (EPS) that encapsulate heavy metal particles, reducing bioavailability. Diatomaceous earth provides porous adsorption sites to immobilize free heavy metal ions. This coupling achieves a synergistic effect through short-term fixation via chemical passivation (addition of pyrite slag) and long-term stability via microbial metabolism (addition of Bacillus subtilis and Bacillus mucilaginosus inoculants), overcoming the tendency for repeated chemical passivation and forming a long-term barrier.

[0030] Organic matter enhancement is achieved by adding humic acid, fulvic acid, and straw charcoal. Humic acid / fulvic acid complexes coal gangue particles with functional groups such as carboxyl and phenolic hydroxyl groups to form water-stable aggregates, resulting in water stability >80%. At the same time, it provides a slow-release carbon source and promotes microbial proliferation. The porous structure of straw charcoal adsorbs nutrients and fixes microorganisms, jointly enhancing water and fertilizer retention capacity.

[0031] By combining organic matter with physical gradation structure, a micro-environment with coordinated water, fertilizer, and air is formed; humic acid chelates residual heavy metals, forming a dual barrier with microbial passivation.

[0032] This invention utilizes a four-stage closed-loop process to transform coal gangue from a "pollution source" into a "soil conditioner," achieving a heavy metal passivation rate of ≥90%, water-stable aggregates of ≥80%, and eliminating secondary waste. The modification method of this invention systematically alters the macroscopic structure (physical gradation) to the microscopic interface (chemical-biological reaction); the coupling of various functions achieves a closed-loop process that passivates toxicity, releases nutrients, constructs structures, and maintains stability, thus achieving ecological self-sustainability: through the continuous action of organic matter and microorganisms, a self-repairing soil ecosystem is formed.

[0033] Furthermore, by modifying the physical gradation of coal gangue particles (a three-stage ratio of sand, silt, and clay), a soil framework structure is constructed to simulate the pore structure of natural soil (porosity 35-45%), forming a physical framework that is breathable, water-retaining, and fertilizer-retaining. Specifically, sand (40%-60%) acts as the framework support, providing large pores and enhancing breathability and drainage; silt (20%-30%) fills the pores, improving water retention; and clay (10%-20%) adsorbs nutrients through surface charge, reducing loss and enhancing adhesion. The synergistic effect of these three components achieves a porosity of 35%-45%, superior to traditional disordered fragmentation (porosity often <30%). This structure provides an alternating aerobic-anaerobic microenvironment for microorganisms, promoting microbial diversity and providing a spatial carrier for subsequent chemical and biological reactions, avoiding the limitation of microbial activity due to structural density.

[0034] Furthermore, the proportions of Bacillus subtilis inoculant (12%-50%) and Bacillus mucilaginosus inoculant (20%-70%) cover the needs of the dominant microbial community. Bacillus subtilis inoculant excels at decomposing organic matter and secreting extracellular polymers, while Bacillus mucilaginosus inoculant can solubilize phosphorus and potassium and produce chelating substances. The synergistic effect of the two can accelerate the degradation of organic matter and nutrient release in coal gangue, while simultaneously converting free heavy metals (such as Cd and Pb) into stable residual states through microbial metabolism; 3%-5% of pyrite slag provides pyrite elements, which generate iron oxides and sulfides during composting fermentation, forming insoluble precipitates with heavy metals (such as PbS and CdS), enhancing heavy metal fixation; 15%-25% of diatomaceous earth serves as a porous carrier, providing attachment points for microorganisms and extending their active period; at the same time, its high specific surface area can adsorb heavy metal ions, reducing the risk of toxic leaching.

[0035] During fermentation, the bio-initiative secretes viscous substances such as polysaccharides and proteins, which, combined with the granular support of diatomaceous earth, promote the formation of water-stable aggregates. This process, synergistic with the three-stage gradation system (porosity 35%-45%), further optimizes pore distribution, avoiding the compaction or loosening problems common in traditional modification methods. Diatomaceous earth itself has a rigid porous structure, serving as a "skeleton" to support the pores between particles, improving the stability and permeability of the aggregates. A high proportion (20%-70%) of Bacillus subtilis specifically activates inert phosphorus and potassium elements in coal gangue, converting them into plant-available forms. Combined with the iron and sulfur trace elements provided by pyrite slag, it effectively replenishes soil nutrients. The porous structure of diatomaceous earth can adsorb nutrient molecules, reducing loss and achieving a slow-release effect. This complements the humic acid and fulvic acid added in subsequent steps, extending the fertilizer effect period.

[0036] Furthermore, Bacillus subtilis (1×10⁻⁶) 8 CFU / g) and Bacillus mucilage (5×10) 7 The live bacteria count (CFU / g) is designed to allow for rapid proliferation during composting, avoiding modification failure caused by microbial imbalance.

[0037] Furthermore, high viable cell counts and neutral pH composting maximize nutrient release and heavy metal passivation by regulating microbial metabolic activity. In principle, Bacillus subtilis inoculants secrete citric acid most efficiently at pH 6.5-7.5, which can dissolve phosphorus and potassium bound to aluminosilicates in coal gangue; the extracellular polysaccharides (EPS) of Bacillus mucilaginosus inoculants are more stable under near-neutral conditions, effectively encapsulating heavy metal particles. If the pH deviates from this range, microbial activity drops sharply, diminishing the modification effect. The organic acids produced by Bacillus subtilis and Bacillus mucilaginosus inoculants simultaneously regulate the pH (6.5-7.5), optimizing the microenvironment for the chemical reaction.

[0038] Aging for 7-10 days provides sufficient time for the reaction: short-term (<7 days) passivation is incomplete, while long-term (>10 days) organic matter is excessively decomposed.

[0039] Furthermore, high-pressure injection (0.5-0.8 MPa) ensures uniform penetration of the microbial agent, solving the problem of uneven bacterial distribution caused by traditional stirring. In principle, high-pressure injection forces the bacterial solution to penetrate the micropores of coal gangue, avoiding surface enrichment; at the same time, the shear force promotes bacterial dispersion and increases the probability of contact with pyrite slag.

[0040] Furthermore, a specific ratio of humic acid (8%-12%), fulvic acid (3%-5%), and straw charcoal (5%-8%) significantly enhances the water stability of the aggregates through functional group complementarity and pore coupling. In principle, the macromolecular network of humic acid combines with the nanopores of straw charcoal to form an "organic-inorganic" composite colloid with a water stability >80% (compared to approximately 50% for traditional materials). The small molecule properties of fulvic acid further penetrate the micropores, chelating residual heavy metals.

[0041] This invention also provides a modified coal gangue soil conditioner prepared by the above method, which directly achieves a heavy metal passivation rate of ≥90% and a water-stable aggregate content of ≥80%, verifying the effectiveness of the four-fold synergistic effect. In principle, Cd / Pb passivation utilizes a dual-barrier mechanism of sulfide precipitation and EPS encapsulation, ensuring that the leaching concentration is below the national standard Class III water limit; the water-stable aggregate content originates from the skeletal support of physical gradation and the cementing effect of organic matter. This product outperforms traditional coal gangue utilization methods (such as roadbed filling, which only improves strength but lacks heavy metal passivation).

[0042] This invention also provides a composite modifier composition for synergistic modification of coal gangue. The composition combines pyrite slag as a chemical passivating agent, Bacillus subtilis and Bacillus mucilaginosus as bioactivators, and humic acid and biochar as organic matter enhancers. Through functional division and synergistic amplification effects, it achieves integrated "passivation-activation-stabilization." In principle, pyrite slag provides instantaneous passivation, microorganisms achieve long-term stabilization, and organic matter maintains system resilience. This design avoids the limitations of single modifiers (such as the tendency for soil compaction when using only chemical passivating agents). The composition reduces coal gangue treatment costs to ≤80 yuan / ton (compared to ≥150 yuan / ton with traditional processes), saving approximately 120 yuan / ton in waste transportation and landfill costs.

[0043] This invention also provides the application of the aforementioned modified coal gangue soil conditioner in mine ecological restoration, heavy metal contaminated soil remediation, or as a crop cultivation substrate. Its versatility in mine ecological restoration, heavy metal remediation, and crop substrates reflects the multifunctional properties of modified coal gangue. In principle, its core advantage is the simultaneous resolution of structural, toxicity, and fertility issues: for example, in mine restoration, the graded structure resists erosion, heavy metal passivation prevents secondary pollution, and organic matter promotes vegetation reconstruction. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of potted Chinese cabbage cultivation in the experimental group (using the modified coal gangue product of Example 1 as the substrate) in Example 2 of the present invention; Figure 2 This is a schematic diagram of wheat cultivation in the field using modified coal gangue in the experimental group of Example 2 of the present invention (using the modified coal gangue product of Example 1 as the substrate); Figure 3This is a comparative schematic diagram of potted Chinese cabbage cultivation in Example 2 of the present invention (using untreated raw coal gangue as a substrate); Figure 4 This is a comparative schematic diagram of field-grown wheat in Example 2 of the present invention (using untreated raw coal gangue as a substrate). Detailed Implementation

[0045] To enable those skilled in the art to understand the features and effects of the present invention, the following descriptions and definitions are only general descriptions of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in the event of any conflict, the definitions in this specification shall prevail.

[0046] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0047] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0048] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0049] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0050] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0051] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0052] Example 1 This embodiment 1 provides a multi-scale synergistic modification method for coal gangue, including the following steps: 1) The coal gangue was crushed to 0.1mm particles. By weight percentage, 40% sand, 20% powder and 10% clay were screened and mixed. The mixture was stirred for 30 minutes at 30r / min using a twin-shaft differential speed mixer to obtain a three-stage gradation system of coal gangue with a porosity of 35%. 2) The effective viable bacteria count was 1×10⁻⁵ by high-pressure injection at 0.5 MPa into the three-stage gradation system of coal gangue after step 1). 8 The CFU / g of Bacillus subtilis inoculum and the effective viable count are 5×10⁻⁶. 7 The bacterial agent of Bacillus subtilis (CFU / g) is 12% by weight of Bacillus subtilis and 20% by weight of Bacillus subtilis. 3% by weight of pyrite slag is added, the pH is adjusted to 6.5, and the mixture is aged for 7 days. 15% by weight of diatomaceous earth is added, wherein the particle size of the diatomaceous earth is ≤0.075mm. 3) By weight percentage, add 8% humic acid, 3% fulvic acid, and 5% straw charcoal to the material treated in step 2). Homogenize under high pressure at 20 MPa for 20 minutes to form water-stable aggregates with a diameter of 1 mm-3 mm. The specific surface area of ​​the straw charcoal is ≥300 m². 2 / g; 4) Prepare 2-4 mm particles from water-stable agglomerates using a disc granulator with an inclination angle of 45°, and control the moisture content to 18%-22% to obtain the finished product.

[0053] The performance results of the finished product obtained in Example 1 were tested and are as follows: The bulk density of the finished product is 1.2 g / cm³. 3 -1.4g / cm 3 EC value ≤ 2.0 mS / cm (NY / T1121.16-2006). The finished product has an organic matter content of 8%-15% and a CEC ≥ 25 cmol / kg (for traditional soil, ≤ 10 cmol / kg). The water stability of organic aggregates is >80%; Effective phosphorus release efficiency increased by 600% (<5mg / kg→45.7mg / kg); The coal gangue utilization rate is 100%, and the processing cost is ≤80 yuan / ton (compared to ≥150 yuan / ton for traditional processes). Ecological performance: Water retention rate > 65% (tested according to GB / T25987-2010); Heavy metal leaching concentration: Cd≤0.05mg / L, Pb≤0.1mg / L (lower than GB / T14848-2017 Class III standard); Heavy metal passivation rate: Cd 92.6%, Pb 89.4% (tested according to HJ781-2016); Nitrogen loss rate reduced to <20% (compared to >50% in traditional processes).

[0054] Example 2 This Example 2 provides a verification of the application effect of the finished product of growing bok choy obtained in Example 1 above: This embodiment illustrates the excellent effects of the modified coal gangue matrix prepared by the method of the present invention in promoting plant growth and ensuring the safety of agricultural products.

[0055] 1. The experimental design adopted the pot experiment method, and the following two groups were set up: Experimental group: The modified coal gangue product prepared in Example 1 was used as the cultivation substrate.

[0056] Comparative example: Untreated raw coal gangue (crushed to 0.1 mm) was used as the cultivation substrate.

[0057] Each group has 6 replicates. Use plastic pots of the same size (30cm in diameter and 25cm in height), and fill each pot with 10kg of the corresponding substrate.

[0058] 2. Experimental Methods: Chinese cabbage and wheat were selected as the test plants. 50 seeds were evenly sown in each pot at a depth of 1 cm. The potted plants were placed in a controlled greenhouse with daytime and nighttime temperatures maintained at 25℃ and 18℃ respectively, and a 12-hour light cycle. The substrate moisture content was maintained at 18%-22% through regular watering. No fertilizer was applied throughout the entire growing season to objectively assess the fertility level of the substrate itself.

[0059] 3. Observation Indicators and Results: After sowing, the emergence status was observed and recorded regularly, and the plants were harvested on the 30th day after sowing to measure relevant indicators. Specific results are shown in Table 1.

[0060] Table 1: Comparison of the bok choy planting effects between Example 2 and the comparative example.

[0061] 4. Results Analysis: As shown in Table 1, (Planting verification: 1) The emergence rate of pak choi increased by 30% (control group 65% → experimental group 95%); biomass increased by 45% (control group fresh weight 2.3 kg / m² → experimental group 3.6 kg / m²); 2) Fast growth: the emergence cycle of pak choi was shortened by 3 days (7 days → 4 days), and the emergence rate was >95% (traditional coal gangue soil ≤65%); 3) Increased biomass: the fresh weight of the experimental group was 3.6 kg / m². 2 (Control group 2.3kg / m) 2 ), yield increased by 45%; 3) Heavy metal safety: Cd content in Chinese cabbage seeds ≤0.05mg / kg (GB2762-2022 limit 0.2mg / kg) Compared with the comparative example, the modified coal gangue matrix of Example 2 of the present invention exhibits significant advantages: 1) Rapid growth promotion effect: The emergence cycle of Example 2 was shortened by 3 days compared with the control group, the emergence rate was increased by 30 percentage points (from 65% to 95%), and the fresh weight of aboveground biomass increased by 45%. This shows that the present invention greatly improves the seed germination environment and seedling growth conditions by constructing a suitable three-phase pore structure and improving nutrient availability (such as available phosphorus).

[0062] 2) Heavy metal safety control: The Cd and Pb contents in the bok choy seeds grown in Example 2 were much lower than those in the comparative example, and met the requirements of the National Food Safety Standard GB2762-2022 (Limits of Contaminants in Food) (Cd ≤ 0.2 mg / kg). This fully verifies that the present invention effectively passivates heavy metals in coal gangue through components such as pyrite slag and straw charcoal, blocking the migration of heavy metals into the food chain and ensuring the safety of agricultural products for consumption.

[0063] In summary, the modified coal gangue substrate provided by this invention can transform traditional solid waste into a safe and efficient new cultivation substrate, possessing excellent physical structure, nutrient supply capacity, and environmental safety.

[0064] like Figure 1 As shown, the bok choy seedlings grew in the modified coal gangue substrate. The plants were evenly and densely distributed, with bright yellow-green leaves, upright stems, and vigorous overall growth, showing excellent germination rate and seedling vitality.

[0065] like Figure 2 As shown, the wheat plants in the growth stage are robust, with large, bright green leaves, and have entered the flowering stage with bright yellow flowers, indicating that the substrate of this invention can continuously support the healthy growth of crops to maturity.

[0066] like Figure 3 As shown, when bok choy seedlings grow in unmodified coal gangue particles, the plants are sparsely distributed and their growth is significantly weaker than that of other plants. Figure 1This visually demonstrates the inhibitory effect of untreated coal gangue on plant growth.

[0067] like Figure 4 As shown, the wheat plants are sparse and short, with weak leaves, exhibiting poor growth. Figure 2 This stark contrast further confirms the significant advantages of the modified coal gangue of this invention in improving the soil environment and promoting crop growth.

[0068] The intuitive comparison of these figures fully demonstrates that the coal gangue modification method provided by this invention can transform solid waste into an excellent cultivation substrate suitable for plant growth, effectively solving the technical problem that raw coal gangue is unsuitable for agricultural use.

[0069] Example 3 This embodiment 3 provides a multi-scale synergistic modification method for coal gangue, including the following steps: 1) The coal gangue was crushed to 0.1mm particles. By weight percentage, 40% sand, 20% powder and 10% clay were screened and mixed. The mixture was stirred for 30 minutes at 30r / min using a twin-shaft differential speed mixer to obtain a three-stage gradation system of coal gangue with a porosity of 35%. 2) The effective viable bacteria count was 1×10⁻⁵ by high-pressure injection at 0.5 MPa into the three-stage gradation system of coal gangue after step 1). 8 The CFU / g of Bacillus subtilis inoculum and the effective viable count are 5×10⁻⁶. 7 The inoculum of Bacillus subtilis (CFU / g) is 12% by weight of Bacillus subtilis and 20% by weight of Bacillus subtilis. 3% by weight of pyrite slag is added, the pH is adjusted to 6.5, and the mixture is aged for 7 days. 15% by weight of diatomaceous earth with a particle size of 0.071 mm is also added. 3) By weight percentage, add 8% humic acid, 3% fulvic acid, and 5% straw charcoal to the material treated in step 2). Homogenize under high pressure at 20 MPa for 20 minutes to form water-stable aggregates with a diameter of 1 mm. The specific surface area of ​​the straw charcoal is 310 m². 2 / g; 4) The water-stable agglomerates were processed into 2mm particles using a disc granulator with an inclination angle of 45°, and the moisture content was controlled at 18% to obtain the finished product.

[0070] Example 4 This embodiment 4 provides a multi-scale synergistic modification method for coal gangue, including the following steps: 1) Crush the coal gangue into 5mm particles, and mix 60% sand, 30% powder and 20% clay by weight percentage. Mix the mixture with a twin-shaft differential speed mixer at 50r / min for 30min to obtain a three-stage gradation system of coal gangue with a porosity of 45%. 2) The effective viable bacteria count was 1×10⁻⁸ by high-pressure injection at 0.8 MPa into the three-stage gradation system of coal gangue after step 1). 8 The CFU / g of Bacillus subtilis inoculum and the effective viable count are 5×10⁻⁶. 7 The inoculum of Bacillus subtilis (CFU / g) is 35% by weight, the inoculum of Bacillus subtilis is 40% by weight, 5% by weight of pyrite slag is added, the pH is adjusted to 7.5, and the mixture is aged for 10 days. 25% by weight of diatomaceous earth with a particle size of 0.063 mm is also added. 3) By weight percentage, add 12% humic acid, 5% fulvic acid, and 8% straw charcoal to the material treated in step 2). Homogenize under 20 MPa pressure for 20 minutes to form water-stable aggregates with a diameter of 3 mm. The specific surface area of ​​the straw charcoal is 320 m². 2 / g; 4) The water-stable agglomerates were processed into 4mm particles using a disc granulator with an inclination angle of 45°, and the moisture content was controlled at 22% to obtain the finished product.

[0071] Example 5 This embodiment 5 provides a multi-scale synergistic modification method for coal gangue, including the following steps: 1) Crush the coal gangue into 3mm particles, and mix 50% sand, 25% powder and 15% clay by weight percentage. Mix the mixture with a twin-shaft differential speed mixer at 40r / min for 30min to obtain a three-stage gradation system of coal gangue with a porosity of 40%. 2) The effective viable bacteria count was 1×10⁻⁷ MPa by high-pressure injection into the three-stage gradation system of coal gangue after step 1). 8 The CFU / g of Bacillus subtilis inoculum and the effective viable count are 5×10⁻⁶. 7 The inoculum of Bacillus subtilis (CFU / g) consists of 50% by weight of Bacillus subtilis and 70% by weight of Bacillus subtilis, with 4% by weight of pyrite slag added. The pH is adjusted to 7.0 and the mixture is aged for 9 days. Finally, 20% by weight of diatomaceous earth with a particle size ≤0.075mm is added. 3) By weight percentage, add 10% humic acid, 4% fulvic acid, and 6% straw charcoal to the material treated in step 2). Homogenize under high pressure at 20 MPa for 20 min to form water-stable aggregates with a diameter of 2 mm. The specific surface area of ​​the straw charcoal is 316 m². 2 / g; 4) The water-stable agglomerates were processed into 3mm particles using a disc granulator with an inclination angle of 45°, and the moisture content was controlled at 20% to obtain the finished product.

[0072] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for multi-scale synergistic modification of coal gangue, characterized in that, Comprising the following steps: 1) crushing, screening and mixing coal gangue to obtain a three-grade grading system coal gangue containing sand particles, powder particles and clay particles; 2) adding pyrite cinder, bacillus subtilis inoculum, bacillus mucilaginosus inoculum and diatomite to the three-grade grading system coal gangue treated in step 1), and uniformly mixing to carry out composting fermentation; 3) adding humic acid, fulvic acid and straw charcoal to the material treated in step 2), and uniformly mixing to obtain water-stable aggregates; 4) post-treating the water-stable aggregates to obtain a finished product.

2. The method of claim 1, wherein, In step 1), the coal gangue is crushed to 0.1mm-5mm particles; the three-grade grading system comprises, by weight percentage: 10%-20% clay particles, 40%-60% sand particles, and 20%-30% powder particles; and the porosity of the three-grade grading system is 35%-45%.

3. The method of claim 1, wherein, The material treated in step 2) comprises, by weight percentage: 3%-5% pyrite cinder, 12%-50% bacillus subtilis inoculum, 20%-70% bacillus mucilaginosus inoculum, and 15%-25% diatomite carrier.

4. The method of claim 1, wherein, The effective viable cell number of Bacillus subtilis in the Bacillus subtilis inoculant is 1 x 10 8 CFU / g, and the effective viable cell number of Bacillus mycoides in the Bacillus mycoides inoculant is 5 x 10 7 CFU / g.

5. The method of claim 1, wherein, In step 2), the conditions for composting fermentation include: adjusting the pH value to 6.5-7.5, and aging for 7-10 days.

6. The method of claim 1, wherein, In step 2), the bacillus subtilis inoculum and the bacillus mucilaginosus inoculum are sprayed into the graded coal gangue treated in step 1) using a high-pressure spraying process, and the pressure of the high-pressure spraying process is 0.5MPa-0.8MPa.

7. The method of claim 1, wherein, In the water-stable aggregates obtained in step 3), the additional components comprise, by weight percentage: 8%-12% humic acid, 3%-5% fulvic acid, and 5%-8% straw charcoal, with the balance being the material treated in step 2).

8. The modified coal gangue soil amendment prepared by the method of any one of claims 1 to 7, characterized in that, The modified coal gangue soil conditioner has a passivation rate of heavy metals Cd and Pb of ≥90%, and a water-stable aggregate content of ≥80%.

9. A composite modifier composition for effecting the synergistic modification of coal gangue as claimed in claim 1, characterized by, Comprising the following components: Pyrite cinder as a chemical passivation agent; A composite microbial inoculum containing bacillus subtilis and bacillus mucilaginosus as a biological activation and stabilizing agent; Humic acid substances and biochar as organic matter enhancers; The composite modifier composition is used to synergistically act with coal gangue particles having a specific grading to achieve heavy metal passivation, nutrient release and structure construction.

10. Use of the modified coal gangue soil conditioner of claim 8 in mine ecological restoration, heavy metal contaminated soil remediation, or as a crop cultivation substrate.

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