Weathered coal-based multi-stage ecological granules, preparation method, preparation device and application thereof

Abstract

The application provides a weathered coal-based multi-stage ecological particle and a preparation method, a preparation device and an application thereof, and belongs to the technical field of soil remediation. The particle comprises, from inside to outside, a phosphorus-containing mineral passivation inner core, a buffer transition layer and an AMF colonization outer layer; a cementing component and a phosphorus-containing mineral passivation component are concentrated in the phosphorus-containing mineral passivation inner core; the buffer transition layer is coated on the phosphorus-containing mineral passivation inner core and is located between the phosphorus-containing mineral passivation inner core and the AMF colonization outer layer, and no additional phosphorus-containing mineral passivation component, cementing component and AMF inoculant are added; the AMF colonization outer layer is coated outside the buffer transition layer, AMF propagules are loaded on the surface and / or shallow pore of the layer; the total phosphorus content of the phosphorus-containing mineral passivation inner core is higher than that of the AMF colonization outer layer, and a phosphorus content gradient decreasing from inside to outside is formed in the radial direction of the particle. The application makes the phosphorus-containing mineral passivation and AMF rhizosphere colonization compatible in the same particle, and realizes the synergistic effect of heavy metal passivation and vegetation restoration.

Description

Technical Field

[0001] This invention relates to the technical field of soil remediation, and in particular to a weathered coal-based multi-level ecological particle, its preparation method, preparation device, and application. Background Technology

[0002] Mining spoil heaps and other degraded soils typically suffer from problems such as disrupted aggregate structure, insufficient water and fertilizer retention capacity, imbalance of available nutrients, potential heavy metal risks, and weak rhizosphere microbial networks. Weathered coal contains humus and various oxygen-containing functional groups, which can serve as organic matter and water and fertilizer retention components; phosphorus-containing minerals such as phosphate rock powder and hydroxyapatite can reduce the mobility and bioavailability of some heavy metals through precipitation, complexation, or surface adsorption; arbuscular mycorrhizal fungi (AMF) can form symbiotic relationships with various host plants, improving soil matrix structure, promoting mineral element transformation, and increasing the number of rhizosphere microorganisms and enzyme activity.

[0003] Existing technologies mainly include the following categories: solid mycorrhizal fungi agents carried on porous materials, but the technical focus is on porous carriers and mycorrhizal fungi utilization; weathered coal, soil and AMF are mixed or inoculated into the rhizosphere, but the phosphorus passivation zone, buffer zone and mycorrhizal colonization zone inside the particles are not involved; core-shell structured microbial agents for soil remediation, in which the microbial composite agent is located inside and the outer layer is a nano-hydrogel shell; this structure is mainly used for microbial protection; mine ecological restoration materials composed of weathered coal, bio-potassium humate, natural zeolite powder, water-absorbing materials and composite bacterial agents, in which the functional components are used in a mixed manner, but no quantifiable radial phosphorus gradient and AMF post-loading interface are set. Soil conditioners with a core-shell structure have a three-layer structure consisting of a nutrient slow-release core, a pH buffering and isolating intermediate layer, and a rhizosphere pH-responsive passivating outer shell, which cannot achieve the function required by this invention; core-shell structured particles composed of purified phosphogypsum powder, pH adjuster, alkaline slow-release material, organic binder, and composite microbial agent have a core of phosphogypsum powder and loaded microorganisms, but no buffering transition layer and AMF colonization outer layer partition.

[0004] In summary, existing technologies have not yet addressed the differentiated requirements of phosphorus-containing minerals, gelling components, and AMF propagules for local phosphorus levels, pH, electrical conductivity, and rhizosphere contact conditions, in order to form chemical passivation zones, buffer transition zones, and mycorrhizal colonization zones with a clear radial order at the same particle scale; nor have they solved the problem that premature addition of AMF may lead to its inactivation during the composting, heating, gelling, or drying processes.

[0005] In view of this, a novel weathered coal-based multi-stage ecological particle, its preparation method, preparation device, and application are proposed to solve all or part of the above problems. Summary of the Invention

[0006] To address at least one of the aforementioned problems and deficiencies in the existing technology, embodiments of the present invention provide a weathered coal-based multi-level ecological particle, its preparation method, preparation apparatus, and application. Through a three-layer radial functional partitioning of "phosphorus-containing mineral passivation core - buffer transition layer - AMF colonization outer layer," phosphorus-containing minerals and cementing components are concentrated in the core, the buffer layer isolates the high-phosphorus and high-salt environment, and AMF is arranged at the outer open interface. Combined with a process sequence of "core curing - outer layer maturation - layered molding - cooling followed by AMF loading," chemical passivation and biological activity are compatible within the same particle. By limiting the total phosphorus ratio of the core / outer layer to ≥3:1 and the outer layer pH to 6.0~7.5 and electrical conductivity (EC) to ≤2.0 mS / cm, quantitative control of the radial functional gradient is achieved, effectively reducing the available heavy metal content (47.5% lower than the control), maintaining the AMF 90-day survival rate at 65.7%, and simultaneously promoting plant growth (dry weight increased by 87% compared to the control). The technical solution is as follows:

[0007] According to one aspect of the present invention, a weathered coal-based multi-level ecological particle is provided, which comprises, from the inside out, a phosphorus-containing mineral passivation core, a buffer transition layer, and an arbuscular mycorrhizal fungal colonization outer layer.

[0008] The phosphorus-containing mineral passivation core contains weathered coal powder, cementing components, and phosphorus-containing mineral passivation components, which are phosphate rock powder, hydroxyapatite, or a combination of the two.

[0009] A buffer transition layer is wrapped around the phosphorus-containing mineral passivation core. This layer does not contain any additional phosphorus-containing mineral passivation components, gelling components, or arbuscular mycorrhizal fungal agents.

[0010] Arbuscular mycorrhizal fungi colonize the outer layer of the buffer transition layer, and the arbuscular mycorrhizal fungi propagules are loaded on the surface of this layer and / or in the shallow pores.

[0011] The ratio of the total phosphorus content of the phosphorus-containing mineral passivated core to the total phosphorus content of the arbuscular mycorrhizal fungal colonization outer layer is not less than 3:1;

[0012] When the outer layer of arbuscular mycorrhizal fungi colonizes and is extracted at a solid-liquid ratio of 1:5, the pH is 6.0-7.5 and the conductivity is less than or equal to 2.0 mS / cm.

[0013] According to another aspect of the present invention, a method for preparing weathered coal-based multi-level ecological particles is provided, for preparing the weathered coal-based multi-level ecological particles described above. The preparation method includes the following steps:

[0014] Step S101: The weathered coal is crushed and passed through a 100-mesh sieve to obtain weathered coal powder with a particle size of less than 0.15 mm.

[0015] Step S102: Based on 100 parts by weight of weathered coal powder, add 5-12 parts by weight of silicate cement, 5-12 parts by weight of fly ash, 1-5 parts by weight of phosphorus-containing mineral passivation components and 20-35 parts by weight of water, and mix to form a slurry; add 0.05-0.15 parts by weight of foaming agent and stir for 10-20 minutes.

[0016] Step S103: The slurry obtained in step S102 is cured at 35~45℃ for 5~8 days, crushed and screened to obtain a 1.5~4.5mm phosphorus-containing mineral passivation core.

[0017] Step S104: Mix weathered coal powder with the background sandstone powder of the spoil heap, and add 0.3%~1.5% of biocompatible binder to form a buffer transition layer wet material; no additional phosphorus-containing mineral passivation components, cement, fly ash and arbuscular mycorrhizal fungi agent are added to the buffer transition layer wet material.

[0018] Step S105: The wet material of the buffer transition layer obtained in step S104 is coated on the outside of the phosphorus-containing mineral passivation core obtained in step S103 to form a buffer transition layer with a thickness of 0.1~0.4mm.

[0019] Step S106: Mix weathered coal powder, decomposed organic fertilizer and background sandstone powder from the spoil heap;

[0020] In step S107, after the material has been composted and cooled to below 30°C, 0.5% to 2.0% of a biocompatible polysaccharide binder is added to form the outer wet material.

[0021] Step S108: The outer wet material obtained in step S107 is wrapped around the outside of the buffer transition layer obtained in step S105, and dried and shaped at a temperature below 35°C to form an outer layer for colonization of arbuscular mycorrhizal fungi.

[0022] Step S109: After the overall temperature of the particles drops below 30°C, the arbuscular mycorrhizal fungal agent is loaded onto the surface and / or shallow pores of the colonized outer layer of the arbuscular mycorrhizal fungi. After loading, no further heating and composting are carried out, and no secondary coating layer to form a continuous dense film is applied.

[0023] According to another aspect of the present invention, an apparatus for preparing weathered coal-based multi-stage ecological particles is provided, for preparing the weathered coal-based multi-stage ecological particles described above. The apparatus includes:

[0024] The crushing and screening unit is used to crush weathered coal and pass it through a 100-mesh sieve to obtain weathered coal powder with a particle size of less than 0.15mm.

[0025] The mixing and pulping unit, connected to the crushing and screening unit, is used to mix weathered coal powder with silicate cement, fly ash, phosphorus-containing mineral passivation components, water and foaming agent to form a slurry;

[0026] The curing unit, connected to the mixing and pulping unit, is used to cure the pulp at 35~45℃;

[0027] The crushing and screening unit, connected to the curing unit, is used to crush and screen the cured blocks into 1.5~4.5mm phosphorus-containing mineral passivation cores.

[0028] The granulation and coating unit is connected to the crushing and screening unit and is used to coat the transition layer wet material on the outside of the phosphorus-containing mineral passivation core to form a buffer transition layer, and to coat the outer layer wet material on the outside of the buffer transition layer to form an arbuscular mycorrhizal fungal colonization outer layer.

[0029] The drying unit, connected to the granulation and coating unit, is used to dry and shape the coated weathered coal-based multi-stage ecological particles at temperatures below 35°C.

[0030] Arbuscular mycorrhizal fungi loading unit, connected to a drying unit, is used to load arbuscular mycorrhizal fungi agent onto the surface and / or shallow pores of the outer layer of arbuscular mycorrhizal fungi colonization after the temperature of weathered coal-based multi-stage ecological particles drops below 30°C.

[0031] According to another aspect of the present invention, an application of weathered coal-based multi-level ecological particles is provided. The weathered coal-based multi-level ecological particles are either the weathered coal-based multi-level ecological particles described above or weathered coal-based multi-level ecological particles obtained by the preparation method described above. The weathered coal-based multi-level ecological particles are used for soil remediation of spoil heaps in lead-bearing mining areas, heavy metal passivation remediation of degraded soils, and vegetation restoration. The weathered coal-based multi-level ecological particles are applied to seed furrows or planting layers, such that the outer layer of arbuscular mycorrhizal fungi colonization is 0-30 mm away from plant seeds or roots.

[0032] The weathered coal-based multi-stage ecological particles, their preparation method, preparation apparatus, and applications provided in the embodiments of the present invention have at least one or a portion of the following advantages:

[0033] (1) Through the three-layer radial functional partition structure of "phosphorus-containing mineral passivation core - buffer transition layer - AMF colonization outer layer", phosphorus-containing minerals and cementing components are concentrated in the core, the buffer layer isolates the high phosphorus and high salt environment, and AMF is located in the open interface of the outer layer, so as to achieve spatial compatibility between chemical passivation and biological activity; by limiting the total phosphorus ratio of the core / outer layer to not less than 3:1 and the pH of the AMF colonization outer layer to 6.0~7.5 and the conductivity not higher than 2.0mS / cm, the radial functional gradient can be quantitatively controlled.

[0034] (2) By further limiting the size range of each layer, the composition of the core formula, and the C / N ratio and seed germination index of the outer layer of decomposed organic fertilizer, we can ensure that the particles have a suitable particle size distribution, stable engineering strength, and a rhizosphere-friendly environment conducive to AMF survival.

[0035] (3) By further limiting the core to betaine foaming and low temperature curing at 35~45℃ to prepare a porous structure, the buffer layer does not add phosphorus-containing minerals and gelling components, and AMF is loaded after the particles are cooled to below 30℃ and then not heated for composting and continuous dense coating, the AMF propagules are protected from high temperature damage and maintain open contact with the rhizosphere environment.

[0036] (4) The preparation method uses the process sequence of "core curing - buffer layer coating - outer layer composting and cooling - layer molding - cooling and loading AMF" to make the three functions compatible in the same particle. AMF is introduced only after the particle is molded and cooled, which avoids the influence of composting and heating on AMF activity. The core is foamed with betaine and cured at a low temperature of 35~45℃ to form a porous structure, which takes into account water absorption, mass transfer and mineral reaction interface.

[0037] (5) By further limiting the AMF agent loading to 0.5%~5% of the final particle weight, the spore germination rate before loading to no less than 60%, and using fungal species such as *Mammillaria mosierifolia* that have a stable symbiotic ability with the host plant, the effective loading and colonization capacity of AMF can be ensured.

[0038] (6) The preparation device is configured with a complete unit chain of crushing and screening unit, mixing and pulping unit, curing unit, granulation and coating unit, drying unit and AMF loading unit, and is equipped with a temperature control module to achieve temperature control throughout the process, so that the preparation method can be implemented stably in industrial applications.

[0039] (7) By applying the granules to the sowing furrow or planting layer and keeping the outer layer of AMF colonization 0-30 mm away from the plant seeds or roots, the AMF propagules directly face the rhizosphere, shortening the spatial distance for establishing symbiotic contact with the host roots; the application rate of 1.5-3.0 t / mu is suitable for host plants such as alfalfa and ryegrass, achieving synergy between soil passivation improvement and vegetation restoration. Attached Figure Description

[0040] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[0041] Figure 1 A process flow diagram of a method for preparing weathered coal-based multi-stage ecological particles according to an embodiment of the present invention;

[0042] Figure 2 This is a photograph showing the macroscopic morphological transformation of the raw materials (weathered coal / fermentation substrate) to the intermediates and finally to the shaped particles during the implementation of this invention.

[0043] Figure 3X-ray diffraction analysis of the phosphorus-containing mineral passivation core material before and after curing of weathered coal-based multi-level ecological particles according to the present invention;

[0044] Figure 4 This is a microscopic morphology diagram of the background sandstone powder raw material used in the spoil heap of the present invention.

[0045] Figure 5 SEM images showing a comparison of the microstructures of weathered coal powder and decomposed organic fertilizer raw materials (buffer transition layer / outer matrix) used in embodiments of the present invention.

[0046] Figure 6 These are SEM images of the low-magnification overall morphology and high-magnification surface pore structure of the final particles according to the preferred embodiment (CT-S+F) of the present invention.

[0047] Figure 7a This is a representative SEM microstructure image of the phosphorus-containing mineral passivated core of weathered coal-based multi-level ecological particles according to an embodiment of the present invention.

[0048] Figure 7b for Figure 7a Representative SEM microstructure of the buffer transition layer of weathered coal-based multi-level ecological particles.

[0049] Figure 7c for Figure 7a Representative SEM microstructure of the AMF colonization outer layer of weathered coal-based multi-level ecological particles.

[0050] Figure 8a SEM microstructure of weathered coal-based multi-level ecological particles with foamed core;

[0051] Figure 8b SEM microstructure of weathered coal-based multi-level ecological particles with no-foam core. Detailed Implementation

[0052] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation thereof.

[0053] Unless otherwise specified, the mass percentage of each solid component is on a dry basis. pH and conductivity were determined using the supernatant obtained after mixing the sample with deionized water at a mass-to-volume ratio of 1:5, stirring for 20-40 min, and allowing it to stand for 20-40 min. The terms and concepts involved in this invention are explained below:

[0054] "Phosphorus-containing mineral passivation core" refers to the intentional addition of phosphate rock powder, hydroxyapatite or a combination thereof during preparation, while also containing cementing components that form the engineering strength of the particles; the phosphorus-containing mineral passivation components and cementing components are concentrated in this core, so that the phosphorus-containing mineral passivation zone is mainly located inside the particles.

[0055] The “buffer transition layer” refers to a continuous or substantially continuous layer that covers the outside of the passivated core of phosphorus-containing minerals and is located inside the colonization layer of arbuscular mycorrhizal fungi (AMF). This layer does not contain any additional phosphate rock powder, hydroxyapatite, cement, or fly ash, and does not contain AMF inoculants.

[0056] "AMF colonization outer layer" refers to the outermost humus / organic matter layer of the granule; AMF is loaded onto the surface and / or shallow pores of this layer after granule forming and cooling. After loading, AMF is no longer continuously sealed with a membrane to maintain its direct contact with the rhizosphere environment.

[0057] Arbuscular mycorrhizal fungi (AMF) are soil fungi that can establish mutualistic symbiotic relationships with the roots of various host plants.

[0058] "AMF post-loading" refers to first completing the phosphorus-containing core curing, buffer transition layer coating, outer matrix composting and cooling, outer coating and low-temperature drying molding. After the overall temperature of the particles drops below 30°C, AMF agent is loaded onto the outermost surface and / or shallow pores. After AMF loading, it no longer undergoes heating and composting, nor is a secondary coating layer for forming a continuous dense film applied.

[0059] The weathered coal-based multi-level ecological particles (hereinafter referred to as particles) provided in the embodiments of the present invention are mainly composed of a phosphorus-containing mineral passivated core, a buffer transition layer, an AMF colonization outer layer, and AMF propagules loaded on the AMF colonization outer layer. The radial positional relationship of the three layers is as follows: phosphorus-containing minerals and cementing components are concentrated in the phosphorus-containing mineral passivated core; the buffer transition layer is located between the phosphorus-containing mineral passivated core and the AMF colonization outer layer; the AMF propagules are mainly located in the outermost layer; the total phosphorus content of the phosphorus-containing mineral passivated core is higher than that of the AMF colonization outer layer, forming a phosphorus content gradient that decreases from the inside to the outside. That is, a "three-layer partition + AMF post-loading" is formed.

[0060] The phosphorus-containing mineral passivation core comprises weathered coal powder, fly ash, silicate cement, phosphorus-containing mineral passivation components, and a porous structure formed by foaming. The phosphorus-containing mineral passivation components are selected from phosphate rock powder, hydroxyapatite, or a combination of both. Based on 100 parts by weight of weathered coal powder, it contains 5-12 parts by weight of silicate cement, 5-12 parts by weight of fly ash, and 1-5 parts by weight of phosphorus-containing mineral passivation components.

[0061] The buffer transition layer includes weathered coal powder and the base sandstone powder of the spoil heap, and may contain 0.3% to 1.5% sodium alginate, carboxymethyl cellulose or starch-based biocompatible binders; this layer does not contain additional phosphorus-containing mineral passivation components, cement, fly ash and AMF bacteria agent.

[0062] The AMF colonization outer layer comprises weathered coal humus components, well-rotted organic fertilizer, background sandstone powder, and 0.5%–2.0% biocompatible polysaccharide binder. Well-rotted organic fertilizer can be livestock and poultry manure compost, straw compost, or a combination of both, and batches with fully decomposed and controlled salinity should be selected. A carbon-to-nitrogen ratio (C / N) of 10–25 and a seed germination index (GI) of not less than 80% are used as raw material screening indicators. Finally, the pH, conductivity, and AMF activity of the finished outer layer are used as the basis for compatibility determination.

[0063] In a preferred embodiment, the phosphorus-containing mineral passivated core has a diameter of 1.5–4.5 mm, the buffer transition layer has a thickness of 0.1–0.4 mm, the AMF colonization outer layer has a thickness of 0.1–0.5 mm, and the final particle size is 2–6 mm. The thickness and mass ratio of the three layers can be optimized based on particle strength, outer layer pH / conductivity, and AMF activity. The dry mass ratio of the three layers, phosphorus-containing mineral passivated core: buffer layer: AMF outer layer, is approximately 60:20:20 (calculated based on dry material input).

[0064] In a preferred embodiment, the ratio of the total phosphorus content of the phosphorus-containing mineral passivated core to the total phosphorus content of the AMF colonized outer layer is not less than 3:1. When the AMF colonized outer layer is extracted at a solid-liquid ratio of 1:5, the pH is 6.0~7.5 and the conductivity is not higher than 2.0 mS / cm.

[0065] In the outer layer of AMF colonization, based on an AMF inoculum with a nominal spore count of 1000 spores / g, the AMF inoculum loading can be 0.5%~5% of the final particle mass, corresponding to approximately 5~50 nominal spores / g in the final particle; the number of effective propagules of AMF after germination rate correction should not be less than 3 / g, preferably 5~40 / g. The spore germination rate of the AMF inoculum before loading should not be less than 60%; after the particles are stored at 25℃±2℃ for 90 days, the AMF activity retention rate should not be less than 60%, preferably not less than 65%; and the AMF colonization rate of the host plant roots should not be less than 60% 45 days after application.

[0066] See Figure 1 The present invention illustrates the process flow of the preparation method of weathered coal-based multi-stage ecological particles.

[0067] See Figure 2 This demonstrates the macroscopic morphological transformation from raw materials (weathered coal / fermentation substrate) to intermediates and finally to shaped particles during the implementation of this invention.

[0068] The left tray contains the raw materials, while the right tray contains 1-4 different batches or formulations of weathered coal-based multi-level ecological granules. The granules exhibit uniform sphericity, verifying the industrial feasibility of the process of this invention (disc granulation and molding). The color of the granules reflects the differences in material composition (e.g., the outer organic matter is darker).

[0069] The specific steps for preparing weathered coal-based multi-stage ecological particles are described below:

[0070] The above-mentioned preparation method of the present invention is carried out in the following process sequence: "preparation and curing of phosphorus-containing porous core --> coating with low phosphorus and AMF-free buffer transition layer --> coating with outer matrix that has been decomposed and cooled --> low temperature drying and molding --> loading AMF after the particles are cooled to below 30°C --> no further heating, decomposition and continuous dense coating after AMF loading".

[0071] 1) Preparation process of phosphorus-containing mineral passivated core (including steps S101~S103):

[0072] Step S101: After removing large pieces of gangue and foreign matter from the weathered coal, crush it and pass it through a 100-mesh sieve to obtain weathered coal powder with a particle size of less than 0.15 mm.

[0073] Step S102: Based on 100 parts by weight of weathered coal powder, add 5-12 parts by weight of silicate cement, 5-12 parts by weight of fly ash, 1-5 parts by weight of phosphorus-containing mineral passivation components, and 20-35 parts by weight of water, and mix to form a slurry. Betaine is used as the foaming agent, added at a rate of 0.05-0.15 parts by weight, and the mixture is stirred for 10-20 minutes.

[0074] Step S103: Pour the slurry obtained in step S102 into a mold and cover it with a film to keep it moist. Cure it at 35~45℃ for 5~8 days. Crush the cured block at low speed and screen it to obtain a 1.5~4.5mm porous phosphorus-containing mineral passivation core.

[0075] In a preferred embodiment, the silicate cement comprises 8 parts by weight, fly ash comprises 8 parts by weight, phosphorus-containing mineral passivation component comprises 3 parts by weight (selected from phosphate rock powder, hydroxyapatite, or a combination thereof), water comprises 25 parts by weight, and betaine comprises 0.08 parts by weight, and is cured at 40°C for 7 days.

[0076] See Figure 3 X-ray diffraction analysis images of phosphorus-containing mineral passivated core materials before and after curing.

[0077] To verify the effectiveness of gel curing, X-ray diffraction (XRD) analysis was performed on the core material before and after curing. The results are as follows: Figure 3As shown, the red line represents the core after curing, and the black line represents the raw material mixture before curing. XRD patterns show that quartz and mullite are the basic mineral phases in the raw materials (derived from weathered coal and fly ash). After curing, broadened characteristic peaks of hydrated calcium silicate (CSH) appeared in the approximately 20-30 degree Celsius range, accompanied by diffraction peaks of calcium carbonate. This indicates that a hydration reaction occurred during the cement curing process, producing a cementitious phase that provides mechanical strength and physical encapsulation effectiveness, allowing the heavy metal passivation components to be more firmly fixed within the particles.

[0078] 2) Preparation and coating process of the buffer transition layer (including steps S104 to S105):

[0079] Step S104: Mix weathered coal powder with the background sandstone powder of the spoil heap, and optionally add 0.3% to 1.5% of a biocompatible binder (selected from sodium alginate, carboxymethyl cellulose, or starch-based binders) to form a buffer transition layer wet material. No additional phosphorus-containing mineral passivation components, cement, fly ash, or AMF inoculant are added to this buffer transition layer wet material.

[0080] Step S105: Using a disc granulator, uniformly coat the wet buffer transition layer material obtained in step S104 onto the outside of the phosphorus-containing mineral passivation core obtained in step S103 to form a buffer transition layer with a thickness of 0.1~0.4mm; pre-dry at a temperature not exceeding 35℃ until the interlayer structure can be maintained.

[0081] See Figure 4 The image shows the microscopic morphology of the sandstone powder raw material from the spoil heap.

[0082] like Figure 4 As shown, the magnification of the microscopic morphology image is ×5000, with a scale bar of 5μm, revealing a distinct layered and plate-like structure. This structure acts as a framework and provides physical isolation within the particles; furthermore, its origin is from the background material of the mining area, demonstrating the advantages of waste-to-waste treatment and local material sourcing.

[0083] 3) Preparation process of the outer matrix for AMF colonization (including steps S106~S107):

[0084] In step S106, weathered coal powder, decomposed organic fertilizer and background sandstone powder from the spoil heap are mixed in a mass ratio of 5:2:1.

[0085] Composted organic fertilizer can be made from livestock and poultry manure, straw compost, or a combination thereof. If organic materials requiring secondary composting are used, add 0.5% of a quick-composting inoculant or compound composting inoculant by weight of the three main materials, and compost them separately for about 15 days until the temperature stabilizes, there is no obvious raw material odor, and preferably the seed germination index (GI) is not less than 80%, to obtain the outer substrate. A carbon-to-nitrogen ratio (C / N) of 10-25 and a seed germination index of not less than 80% are used as indicators of composting maturity.

[0086] Step S107: After the composting is completed, heat is released to reduce the temperature of the outer matrix center to below 30°C or the temperature difference with the ambient temperature to no more than 5°C; add sodium alginate, carboxymethyl cellulose or starch polysaccharide binder equivalent to 0.5%~2.0% of the dry weight of the outer layer to form the outer wet material.

[0087] See Figure 5 The image shows a comparison of the microstructures of weathered coal powder and decomposed organic fertilizer raw materials (buffer transition layer / outer matrix).

[0088] like Figure 5 As shown, the left side is dense or aggregated, while the right side is loose, porous, or fibrous. This complementarity of microscopic morphology provides a structural basis for subsequent layered coating. It also explains from a microscopic level why it is necessary to separately decompose and cool the organic fertilizer before using it as the outer substrate to ensure the survival environment of AMF.

[0089] 4) Outer layer molding and AMF post-loading process (including steps S108~S109):

[0090] Step S108: The outer wet material obtained in step S107 is wrapped around the outside of the buffer transition layer obtained in step S105 to form the outermost organic / humus layer, and dried and shaped at a temperature below 35°C.

[0091] Step S109: After the overall temperature of the particles drops below 30°C, the AMF agent is loaded onto the outer surface and / or shallow pores of the AMF colonization layer using low-temperature spraying, roller mixing, or impregnation methods. After loading, the AMF is not subjected to further heating for composting, nor is a secondary coating layer for forming a continuous dense film applied.

[0092] In a preferred embodiment, the AMF inoculant is preferably Funneliformismosseae, but other single or compound AMF inoculants with stable symbiotic ability with the target host plant can also be used. Taking a powder with a nominal spore count of 1000 spores / g as an example, the amount of inoculant can be 0.5% to 5% of the final particle weight, corresponding to approximately 5 to 50 nominal spores / g in the final particle; the actual effective loading should be determined in conjunction with the spore germination rate, survival rate, and root colonization rate. Preferably, the inoculant is loaded at 2.0% of the final particle weight.

[0093] In a preferred embodiment, AMF quality control employs the water agar plate germination method or an equivalent method to determine the spore germination rate, distinguishing between "nominal spore count" and "effective propagule count." A spore germination rate of at least 60% before loading is used as a screening indicator for the inoculum. Activity retention is recorded after 30, 60, and 90 days of storage, and root colonization rate is verified using the host plant root staining-crosspoint method or an equivalent method.

[0094] See Figure 6 The image shows a low-magnification overall morphology and a high-magnification surface pore structure of the final particles of the preferred embodiment (CT-S+F) of the present invention via SEM images.

[0095] like Figure 6 As shown, the low-magnification SEM image on the left reveals that the particles have a three-dimensional structure and a certain mechanical strength; the high-magnification SEM image on the right reveals that the outer surface of the AMF colonization layer has a rich open pore structure. This open outer layer structure confirms the "AMF post-loading" and "non-continuous dense film formation" schemes, that is, the external porous environment allows the AMF propagules to maintain direct material and water exchange with the rhizosphere soil, which is conducive to mycorrhizal infection and root colonization.

[0096] In a specific embodiment, the rhizosphere application method of the present invention is as follows: AMF loaded with multi-level ecological particles can be applied to the sowing furrow, so that the outer layer of AMF colonization is 0-30mm away from the plant seeds or roots; or it can be applied to the planting layer of 0-10cm at a rate of 1.5-3.0t / mu.

[0097] In a preferred embodiment, the application rate is 2.4 t / acre. The host plant is preferably alfalfa, ryegrass, or other plants that can establish an effective symbiotic relationship with the selected AMF.

[0098] The present invention will be further illustrated by the following specific embodiments:

[0099] The raw materials used in the specific embodiments and their basic properties are as follows:

[0100] Weathered coal from Inner Mongolia was used: Existing tests showed that weathered coal with a particle size of 0.125~1mm had an organic matter content of 62.0%~68.1% and a pore volume of 0.012~0.019cm³. 3 / g; During preparation, the weathered coal is crushed and passed through a 100-mesh sieve to control the particle size to be less than 0.15mm.

[0101] The background material used was sandstone from the Weijiamao spoil heap, with an Al2O3 content of 23.40%–31.59% and a SiO2 content of 55.03%–60.53%. The surface soil at the implementation site had a pH of 7.9 and a bulk density of 1.45 g / cm³. 3Available phosphorus is 19 mg / kg and available potassium is 65 mg / kg.

[0102] Example 1:

[0103] Example 1 relates to the preparation of a phosphorus-containing mineral passivated core.

[0104] Take 1000 kg of weathered coal powder with a particle size less than 0.15 mm, add 80 kg of silicate cement, 80 kg of fly ash, 30 kg of phosphorus-containing mineral passivation component (phosphate rock powder is used in this example), and 250 kg of water, and mix to form a slurry. Then add 0.8 kg of betaine foaming agent and stir for 15 minutes. Pour into a mold, cover with a film to keep moist, and cure at 40℃ for 7 days. Crush the cured block at low speed and sieve it into a porous phosphorus-containing mineral passivation core with a diameter of 1.5~4.5 mm.

[0105] Example 2:

[0106] Example 2 relates to the preparation of a buffer transition layer and an AMF colonization outer layer.

[0107] Weathered coal powder was mixed with sandstone powder from the spoil heap and 0.5% to 1.0% sodium alginate was added to make a transition layer wet material. This material was then coated onto the outer side of the core obtained in Example 1 using a disc granulator, and the thickness of the buffer transition layer was controlled to be about 0.2 to 0.4 mm.

[0108] Separately, weathered coal powder, well-rotted organic fertilizer, and sandstone powder are mixed in a mass ratio of 5:2:1. For the well-rotted organic fertilizer, livestock and poultry manure compost, straw compost, or a combination thereof are preferred. During raw material screening, the carbon-to-nitrogen ratio (C / N) should be controlled between 10 and 25, and the seed germination index (GI) should not be lower than 80%. Add 0.5% of a quick-rotting microbial agent according to the total mass of the three main materials for necessary secondary composting for approximately 15 days. After cooling to below 30℃, add 1.0% sodium alginate to form an outer wet material, which is then wrapped around the outside of the transition layer. The thickness of the AMF colonization outer layer is controlled to be approximately 0.3-0.5 mm. Dry and shape the mixture at 30-35℃.

[0109] Example 3:

[0110] Example 3 involves AMF post-load.

[0111] After the granules were dried and cooled to below 30°C, they were post-loaded with *Mesona muscarinae* AMF powder. Taking a fungal agent with a nominal spore count of 1000 spores / g as an example, the fungal agent was mixed with a small amount of 0.2% carboxymethyl cellulose aqueous solution at a final granule weight of 2.0%. The mixture was then applied to the outermost surface and shallow pores using a low-temperature spraying and roller mixing method. After loading, the mixture was dried in a ventilated environment at a temperature not exceeding 30°C, without further continuous coating. Spore activity was evaluated using the water agar germination method before loading, with a germination rate of not less than 60%. Activity was retested after 30, 60, and 90 days of storage.

[0112] Example 4:

[0113] Example 4 involves the setting of comparative proportions and the design of the same total formula principle.

[0114] To avoid the impact of differences in total formulation on the comparative results, the same batch of raw materials was used in all treatments, and the actual dry material input of the CT-S+F treatment was used as the benchmark for calculation, ensuring that the total input of weathered coal, sandstone powder, organic fertilizer, cement, fly ash, phosphorus-containing minerals, binder, and AMF remained consistent among comparable treatments. The comparative treatments are as follows:

[0115] CK (basal control): No particles were applied, and no AMF was inoculated.

[0116] U+F (Uniform Mixing): Weigh all raw materials according to the total dry formulation of CT-S+F, and uniformly mix the dry materials belonging to the core, buffer layer and outer layer before granulation; complete the same low-temperature treatment, and load the granules with an equal amount of AMF after cooling. This is used to verify the contribution of radial spatial partitioning and to eliminate the influence of "material composition + AMF" itself.

[0117] CTS (without AMF): This invention forms a phosphorus-containing mineral passivated core --> a buffer transition layer --> an AMF-colonized outer layer (low-phosphorus outer layer), but without AMF loading. It is used to evaluate the function of the three-layer material itself.

[0118] CT-S+F (This invention): According to this invention, a phosphorus-containing mineral passivated core is formed --> a buffer transition layer --> an AMF colonization outer layer (low phosphorus outer layer), and after particle molding and cooling, an equal amount of AMF is loaded (core processing process).

[0119] R+F (Reverse Phosphorus Distribution): Maintaining a consistent overall formulation, only phosphorus-containing minerals are moved from the core to the outermost layer, while the total amount of other materials and AMF remains unchanged; AMF is still loaded in equal amounts after molding and cooling. Used to verify the directionality of "phosphorus internal, AMF external".

[0120] Early-F (Pre-inoculation): Maintaining consistency with the overall formula and three-layer structure, but adding an equal amount of AMF before the outer layer matures / is formed, allowing it to undergo subsequent processes. Used to verify the timing necessity of "final loading".

[0121] No-foam: Keeping the rest of the core formulation and all subsequent steps unchanged, only the betaine foaming agent is removed. Used to verify the contribution of core foaming to pore structure, water retention, and passivation.

[0122] The above comparative ratios were set according to the principle of the same total formula and single-factor variation.

[0123] Example 5:

[0124] Example 5 involves the realism of the three-layer structure and the distribution of cross-sectional elements.

[0125] The radial structure of the phosphorus-bearing mineral passivated core --> buffer transition layer --> AMF colonized outer layer was verified using vernier calipers, cross-sectional microscopic images, micro-computed tomography (Micro-CT), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), micro-area X-ray fluorescence spectroscopy (μ-XRF), or equivalent methods. Three independent preparation batches (B1~B3) were recorded. The three-layer particle geometry and coating integrity are shown in Table 1.

[0126] Table 1. Three-layer particle geometry and coating integrity

[0127]

[0128] The final particle size, phosphorus-containing mineral passivated core diameter, buffer layer, and AMF outer layer thickness remained generally stable across the three independent preparation batches, with a coating integrity rate exceeding 93%. This indicates that the process can repeatedly form multi-level particle structures with identifiable cores, buffer transition layers, and outer layers. The cross-sectional interface observation and elemental distribution verification framework are shown in Table 2.

[0129] Table 2. Framework for Cross-Sectional Interface Observation and Element Distribution Verification

[0130]

[0131] See Figures 7a-7c The table shows the representative SEM microstructures of the three functional regions (scale bar is 50 μm).

[0132] Figures 7a-7c The existing samples were recorded sequentially according to the phosphorus-containing mineral passivated core, buffer transition layer, and AMF colonization outer layer.

[0133] like Figure 7a As shown, the core is a phosphorus-containing mineral passivation core with a dense granular surface. It is a hydration product and polymer structure formed by weathered coal powder, cement, and phosphorus-containing mineral passivation components after curing, and it undertakes the functions of chemical passivation and strength support.

[0134] like Figure 7b As shown, the buffer transition layer exhibits a distinct sheet-like, network-like, or fibrous skeleton-like structure, which is the cross-linking morphology of polysaccharide binder and weathered coal / sandstone powder. This structure is relatively loose and does not contain additional phosphorus mineral passivation components or cement, proving that the buffer zone, as an isolation layer, reduces the direct material contact between the chemical passivation zone and the active bacteria zone.

[0135] like Figure 7cAs shown, the outer layer of AMF colonization has a rough surface and a rich porous granular stacked structure, which is conducive to the attachment and colonization of AMF spores / hyphae. It also has good air permeability and water exchange channels, which is in line with the design concept of open rhizosphere interface.

[0136] Example 6:

[0137] Example 6 involves radial P, pH, and EC gradients.

[0138] Sample batches: 3 independently prepared batches (B1~B3); Layering and peeling method: After freeze-fixation of particles, mechanical peeling was performed along the visible interface, and the core, buffer layer, and outer layer were collected and ground separately; Total P was determined by acid digestion-inductively coupled plasma optical emission spectrometry (ICP-OES), available P was determined by NaHCO3 extraction, and water-soluble P was determined by deionized water extraction; pH and EC extraction conditions: sample:deionized water = 1:5, stirring for 20~40 min, standing for 20~40 min, and then measuring the supernatant. The radial P, pH, and EC results of the three layers are shown in Table 3.

[0139] Table 3 Results of radial P, pH and EC in the three layers

[0140]

[0141] The three-layered particles exhibit distinct gradients in phosphorus content, pH, and electrolytic activity (EC) from the inside out. After the phosphorus-containing minerals are concentrated in the core, the total phosphorus in the outer layer decreases to 4.3 g / kg, with a core / outer layer total phosphorus ratio of approximately 5.72:1. Simultaneously, the pH and EC in the outer layer decrease to approximately 6.87 and 0.93 mS / cm, respectively. These results indicate that the buffer transition layer can create an environmental transition between the phosphorus-containing core and the AMF-colonized outer layer, confining the high-phosphorus and high-ionic-strength environment primarily within the particle interior.

[0142] Example 7:

[0143] Example 7 relates to AMF germination, storage activity, and root colonization.

[0144] AMF strain and batch: *Cyclocarya mosierifolia*, same batch of inoculum; nominal spore count: 1000 spores / g; loading at application points: approximately 20 nominal spores / g of particle weight (calculated at 2.0% of final particle weight); spore germination was performed using the water agar plate germination method or an equivalent method, with a recommended germination rate ≥60% before loading; storage activity was recorded at 30, 60, and 90 days; host plant: alfalfa; culture time: 45 days; root colonization was performed using the staining-crosspoint method or an equivalent method; biological replicates: 5. See Table 4 for AMF spore germination, storage activity, and root colonization.

[0145] Table 4. AMF spore germination, storage activity, and root colonization

[0146]

[0147] The 90-day AMF viability and root colonization rate of the CT-S+F treatment were higher than those of the U+F, R+F, and Early-F treatments. Specifically, compared to R+F, this indicates that concentrating phosphorus-containing minerals in the core and placing AMF in a low-phosphorus outer layer is more conducive to maintaining AMF activity. Compared to Early-F, this indicates that loading AMF after pellet formation and cooling reduces the impact of the early composting, curing, and drying processes on propagule activity.

[0148] The above results validate the necessity of "AMF post-loading": while keeping the structure, formulation, and AMF dosage completely consistent, only the AMF addition time was changed. The Early-F group had lower initial germination rate, 30 / 60 / 90-day survival rate, 45-day root colonization rate, and plant biomass than the CT-S+F group because the AMF underwent subsequent composting, molding, or drying processes. In contrast, the CT-S+F group had higher 90-day activity retention rate and root colonization rate because the AMF was loaded after the particles were cooled to below 30°C and the post-loading temperature rise and continuous dense coating were avoided.

[0149] Example 8:

[0150] Example 8 involves the available form, leaching form, and plant absorption of heavy metals.

[0151] Pb was selected as a representative heavy metal for validation; soil / matrix batch: Weijiamou topsoil composite matrix T-01; initial total: approximately 120 mg / kg; initial DTPA bioavailability: approximately 12.0 mg / kg; bioavailability was determined by diethylenetriaminepentaacetic acid (DTPA) extraction-ICP-OES, and leached bioavailability was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) or equivalent acid leaching method; culture time: 45 days; number of replicates: 5. Pb bioavailability, leached bioavailability, and plant uptake response are shown in Table 5.

[0152] Table 5. Available Pb forms, leached forms, and plant uptake response.

[0153]

[0154] The DTPA-Pb concentration in the CT-S+F treatment was 6.3 ± 0.4 mg / kg, a decrease of approximately 47.5% compared to the control (CK) and a further decrease of approximately 25.0% compared to the U+F treatment. Simultaneously, both the leaching concentration and the plant Pb content decreased. The CTS treatment already showed a better reduction in bioavailable Pb compared to the CK. After further loading with AMF, the bioavailable Pb, leaching concentration, and plant Pb content in the CT-S+F treatment decreased further, indicating that the passivation effect of the material and the rhizosphere biological activity have a synergistic improvement effect.

[0155] Example 9:

[0156] Example 9 relates to pore structure, water absorption properties, and particle stability.

[0157] Pore ​​structure detection methods: Mercury intrusion porosimetry, micron-based CT, or a combination of both are preferred for determining total porosity, pore volume, and representative pore size. Water absorption test conditions: After conversion to dry weight, immerse in deionized water for 24 hours, remove surface free water, and weigh. Immersion stability test conditions: Immerse for 24 hours to measure mass retention rate, and continuously immerse for 7 days to record particle integrity rate. Number of replicates: 5. No-foam treatment only removes the foaming agent and is used to evaluate the contribution of foaming to pore structure formation. Pore structure, water absorption, and stability indices are shown in Table 6.

[0158] Table 6 Pore structure, water absorption and stability index

[0159]

[0160] See Figure 8a and Figure 8b The SEM microstructures of the foamed core and the non-foamed core are shown respectively.

[0161] like Figure 8a As shown, this illustrates the well-developed, interconnected macroporous and mesoporous structures that emerge after the addition of betaine foaming agent. Figure 8b As shown, it appears as a relatively dense and smooth block. This morphological difference corresponds to Table 6 above. Compared to No-foam, foamed particles have higher total porosity, pore volume, and water absorption ratio, while unfoamed particles may have a higher short-term mass retention rate due to their denser structure. Therefore, the main role of core foaming is to improve pore structure and water absorption and mass transfer performance, while the mechanical stability of the particles needs to be optimized by combining the degree of foaming and gel strength.

[0162] Example 10:

[0163] Example 10 relates to plant growth and rhizosphere response.

[0164] Plant species / variety: alfalfa; culture medium and application rate: topsoil from Weijiamou, with granules converted to potting substrate at an equivalent rate of 2.4 t / mu; culture time: 45 days; number of plants per treatment: 10; number of biological replicates: 5. See Table 7 for plant growth indicators.

[0165] Table 7 Plant growth indicators

[0166]

[0167] Compared with CK and U+F, the CT-S+F treatment showed higher germination rate, plant height, root length, fresh weight, and dry weight. The CTS treatment also showed some improvement in plant growth, and further loading with AMF further improved all growth indicators. These results indicate that the three-layer granules themselves can improve the rhizosphere environment, and subsequent loading with AMF is beneficial for further promoting root development and plant biomass formation.

[0168] Example 11:

[0169] Example 11 is a comparison of comprehensive performance. The effects of radial spatial partitioning, phosphorus-containing mineral configuration direction, and AMF introduction timing on the outer environment of particles, AMF activity, Pb bioavailability, and plant growth were comprehensively compared, and representative indicators are summarized in Table 8.

[0170] Table 8 Summary of Core Performance Indicators

[0171]

[0172] Comparison of CT-S+F and U+F: With the same total formula, the three-layer spatial partitioning reduces the total P, pH and EC in the outer layer, while increasing the 90-day survival rate, root colonization rate and plant dry weight, accompanied by a decrease in DTPA-Pb.

[0173] Comparison of CT-S+F and R+F: When phosphorus-containing minerals are concentrated in the core and separated from the outer AMF layer by a buffer layer, the high phosphorus exposure in the outer layer is reduced, and the AMF activity and root colonization index are better than the "external phosphorus" treatment.

[0174] Comparison of CT-S+F and Early-F: With the spatial structure unchanged, only the AMF introduction time was changed; the 90-day survival rate, root colonization rate and plant growth indicators of the loaded group after molding and cooling were higher than those of the early-inoculated group.

[0175] In summary, under the same total formulation and AMF dosage conditions, the three-layer partitioning of the present invention simultaneously reduces the phosphorus, pH and EC in the outer layer, increases the AMF survival rate and root colonization rate, and reduces the available Pb and plant absorption.

[0176] Furthermore, with the structure, formulation, and AMF dosage completely identical, simply changing the AMF addition time to loading after the pellets have cooled to below 30°C can significantly improve the initial germination rate, 30 / 60 / 90-day survival rate, 45-day root colonization rate, and plant biomass.

[0177] This invention also provides a preparation apparatus for realizing the above-mentioned "three-layer radial functional zoning + AMF post-loading" process. In this preparation apparatus, the front-end crushing and screening unit is used to crush weathered coal and pass it through a 100-mesh sieve to obtain weathered coal powder with a particle size of less than 0.15 mm; the mixing and slurry preparation unit is connected to the front-end crushing and screening unit and is used to mix the weathered coal powder with silicate cement, fly ash, phosphorus-containing mineral passivation components, water and foaming agent to form a slurry; the curing unit is connected to the mixing and slurry preparation unit and is used to cure the slurry at 35~45℃ to form a hydrated cementitious phase and a porous structure in the core; the rear-end crushing and screening unit is connected to the curing unit and is used to crush and screen the cured block into phosphorus-containing mineral passivated cores of 1.5~4.5 mm.

[0178] Next, the granulation and coating unit is connected to the subsequent crushing and screening unit, preferably a disc granulator. This unit first coats the low-phosphorus, AMF-free transition layer wet material onto the outside of the porous core to form a buffer transition layer. Then, the fully decomposed and cooled outer layer wet material is coated onto the outside of the buffer transition layer to form the AMF colonization outer layer. The drying unit is connected to the granulation and coating unit and is used to perform low-temperature drying and shaping of the coated granules at temperatures below 35°C to avoid heat damage to the outer matrix and subsequent AMF.

[0179] The AMF loading unit is connected to the drying unit, preferably a low-temperature spraying device, a roller mixing device, or an impregnation device, and is used to load the AMF agent onto the outer surface of the AMF colonization layer and / or the shallow pores after the overall temperature of the particles drops below 30°C; after loading, no further heating and maturation are carried out, nor is a secondary coating to form a continuous dense film applied.

[0180] The temperature control module works in conjunction with the curing unit, drying unit, and AMF loading unit to control the curing temperature, drying temperature, and AMF loading temperature, thereby ensuring the stable implementation of the process sequence of "curing the core first, then wrapping the buffer layer, then wrapping the outer layer after it has been cured and cooled, drying and molding at low temperature, and then loading AMF after cooling to below 30°C".

[0181] The weathered coal-based multi-stage ecological particles, their preparation method, preparation apparatus, and applications provided in the embodiments of the present invention have at least one or a portion of the following advantages:

[0182] (1) Through the three-layer radial functional partition structure of "phosphorus-containing mineral passivation core - buffer transition layer - AMF colonization outer layer", phosphorus-containing minerals and cementing components are concentrated in the core, the buffer layer isolates the high phosphorus and high salt environment, and AMF is located in the open interface of the outer layer, so as to achieve spatial compatibility between chemical passivation and biological activity; by limiting the total phosphorus ratio of the core / outer layer to not less than 3:1 and the pH of the AMF colonization outer layer to 6.0~7.5 and the conductivity not higher than 2.0mS / cm, the radial functional gradient can be quantitatively controlled.

[0183] (2) By further limiting the size range of each layer, the composition of the core formula, and the C / N ratio and seed germination index of the outer layer of decomposed organic fertilizer, we can ensure that the particles have a suitable particle size distribution, stable engineering strength, and a rhizosphere-friendly environment conducive to AMF survival.

[0184] (3) By further limiting the core to betaine foaming and low temperature curing at 35~45℃ to prepare a porous structure, the buffer layer does not add phosphorus-containing minerals and gelling components, and AMF is loaded after the particles are cooled to below 30℃ and then not heated for composting and continuous dense coating, the AMF propagules are protected from high temperature damage and maintain open contact with the rhizosphere environment.

[0185] (4) The preparation method uses the process sequence of "core curing - buffer layer coating - outer layer composting and cooling - layer molding - cooling and loading AMF" to make the three functions compatible in the same particle. AMF is introduced only after the particle is molded and cooled, which avoids the influence of composting and heating on AMF activity. The core is foamed with betaine and cured at a low temperature of 35~45℃ to form a porous structure, which takes into account water absorption, mass transfer and mineral reaction interface.

[0186] (5) By further limiting the AMF agent loading to 0.5%~5% of the final particle weight, the spore germination rate before loading to no less than 60%, and using fungal species such as *Mammillaria mosierifolia* that have a stable symbiotic ability with the host plant, the effective loading and colonization capacity of AMF can be ensured.

[0187] (6) The preparation device is configured with a complete unit chain of crushing and screening unit, mixing and pulping unit, curing unit, granulation and coating unit, drying unit and AMF loading unit, and is equipped with a temperature control module to achieve temperature control throughout the process, so that the preparation method can be implemented stably in industrial applications.

[0188] (7) By applying the granules to the sowing furrow or planting layer and keeping the outer layer of AMF colonization 0-30 mm away from the plant seeds or roots, the AMF propagules directly face the rhizosphere, shortening the spatial distance for establishing symbiotic contact with the host roots; the application rate of 1.5-3.0 t / mu is suitable for host plants such as alfalfa and ryegrass, achieving synergy between soil passivation improvement and vegetation restoration.

[0189] While some embodiments of the present general inventive concept have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A type of weathered coal-based multi-stage ecological granules, characterized in that, The weathered coal-based multi-level ecological particles consist, from the inside out, a phosphorus-containing mineral passivation core, a buffer transition layer, and an outer layer colonizing arbuscular mycorrhizal fungi. The phosphorus-containing mineral passivation core contains weathered coal powder, cementing components, and phosphorus-containing mineral passivation components. The cementing components and the phosphorus-containing mineral passivation components are concentrated in the phosphorus-containing mineral passivation core. The phosphorus-containing mineral passivation components are phosphate rock powder, hydroxyapatite, or a combination of the two. The buffer transition layer covers the outside of the phosphorus-containing mineral passivation core and is located between the phosphorus-containing mineral passivation core and the arbuscular mycorrhizal fungus colonization outer layer. This layer does not contain any additional phosphorus-containing mineral passivation components, gelling components, or arbuscular mycorrhizal fungus inoculants. The colonizing outer layer of the arbuscular mycorrhizal fungi covers the outside of the buffer transition layer, the arbuscular mycorrhizal fungi propagules are loaded on the surface of the layer and / or in the shallow pores, and the colonizing outer layer of the arbuscular mycorrhizal fungi is the outermost layer of the particles. The total phosphorus content of the phosphorus-containing mineral passivated core is higher than that of the total phosphorus content of the colonized outer layer of the arbuscular mycorrhizal fungi, and a phosphorus content gradient from the inside to the outside is formed in the radial direction of the particles; The arbuscular mycorrhizal fungal propagules are propagules loaded onto the outer surface and / or shallow pores of the colonized arbuscular mycorrhizal fungi after granulation and cooling to below 30°C. They have not undergone heating and decomposition after loading, and the outer surface of the colonized arbuscular mycorrhizal fungi is not provided with a continuous dense coating.

2. The weathered coal-based multi-stage ecological granules according to claim 1, characterized in that, The ratio of the total phosphorus content of the phosphorus-containing mineral passivated core to the total phosphorus content of the arbuscular mycorrhizal fungal colonization outer layer is not less than 3:1; When the outer layer of the colonized arbuscular mycorrhizal fungi is extracted at a solid-liquid ratio of 1:5, the pH is 6.0~7.5 and the conductivity is less than or equal to 2.0 mS / cm.

3. The weathered coal-based multi-stage ecological granules according to claim 1, characterized in that, The diameter of the phosphorus-containing mineral passivation core is 1.5~4.5mm, the thickness of the buffer transition layer is 0.1~0.4mm, the thickness of the arbuscular mycorrhizal fungal colonization outer layer is 0.1~0.5mm, and the final particle size of the weathered coal-based multi-level ecological particles is 2~6mm. The phosphorus-containing mineral passivation core contains, based on 100 parts by weight of weathered coal powder, 5-12 parts by weight of silicate cement, 5-12 parts by weight of fly ash, 1-5 parts by weight of phosphorus-containing mineral passivation components, and a pore structure formed by foaming. The buffer transition layer contains weathered coal powder and background sandstone powder from the spoil heap, as well as 0.3% to 1.5% of a biocompatible binder, which is selected from sodium alginate, carboxymethyl cellulose or starch-based binders. The colonizing outer layer of the arbuscular mycorrhizal fungi contains weathered coal humus components, decomposed organic fertilizer and background sandstone powder from the spoil heap, as well as 0.5% to 2.0% of a biocompatible polysaccharide binder.

4. The weathered coal-based multi-stage ecological granules according to any one of claims 1-3, characterized in that, The phosphorus-containing mineral passivated core is prepared by a method comprising the following steps: Weathered coal is crushed and passed through a 100-mesh sieve to obtain weathered coal powder with a particle size of less than 0.15 mm. Based on 100 parts by weight of the weathered coal powder, 5-12 parts by weight of silicate cement, 5-12 parts by weight of fly ash, 1-5 parts by weight of phosphorus-containing mineral passivation components, and 20-35 parts by weight of water are added to form a slurry. 0.05-0.15 parts by weight of betaine foaming agent are added and stirred for 10-20 minutes. The resulting slurry is cured at 35-45℃ for 5-8 days and then crushed and sieved to obtain phosphorus-containing mineral passivation cores of 1.5-4.5 mm. The buffer transition layer does not contain any additional phosphate rock powder, hydroxyapatite, cement, fly ash, or arbuscular mycorrhizal fungi inoculant. After the arbuscular mycorrhizal fungi colonization outer layer is formed into granules and cooled to below 30°C, arbuscular mycorrhizal fungi propagules are loaded onto it. After loading, no further heating and composting or secondary coating to form a continuous dense film is performed.

5. The weathered coal-based multi-stage ecological granules according to claim 4, characterized in that, In the outer layer of the colonized arbuscular mycorrhizal fungi, based on an arbuscular mycorrhizal fungi agent with a nominal spore count of 1000 spores / g, the loading of the arbuscular mycorrhizal fungi agent is 0.5% to 5% of the final particle mass, corresponding to 5 to 50 nominal spores / g in the final particles; The number of effective propagules of arbuscular mycorrhizal fungi after correction for spore germination rate is not less than 3 per g; Before loading, the spore germination rate of the arbuscular mycorrhizal fungal inoculant should not be less than 60%; After the weathered coal-based multi-level ecological granules are stored at 25℃±2℃ for 90 days, the activity retention rate of arbuscular mycorrhizal fungi is not less than 60%; and / or, the colonization rate of arbuscular mycorrhizal fungi in the roots of the host plant is not less than 60% 45 days after application.

6. A method for preparing weathered coal-based multi-level ecological particles, the method being used to prepare weathered coal-based multi-level ecological particles according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: Step S101: The weathered coal is crushed and passed through a 100-mesh sieve to obtain weathered coal powder with a particle size of less than 0.15 mm. Step S102: Based on 100 parts by weight of the weathered coal powder, add 5-12 parts by weight of silicate cement, 5-12 parts by weight of fly ash, 1-5 parts by weight of phosphorus-containing mineral passivation components and 20-35 parts by weight of water, and mix to form a slurry; add 0.05-0.15 parts by weight of foaming agent and stir for 10-20 minutes. Step S103: The slurry obtained in step S102 is cured at 35~45℃ for 5~8 days, crushed and screened to obtain a 1.5~4.5mm phosphorus-containing mineral passivation core. Step S104: Mix weathered coal powder with sandstone powder from the spoil heap, and add 0.3%~1.5% of biocompatible binder to form a buffer transition layer wet material; the buffer transition layer wet material does not contain additional phosphorus-containing mineral passivation components, cement, fly ash and arbuscular mycorrhizal fungi inoculant. Step S105: The wet material of the buffer transition layer obtained in step S104 is coated on the outside of the phosphorus-containing mineral passivation core obtained in step S103 to form a buffer transition layer with a thickness of 0.1~0.4mm. Step S106: Mix weathered coal powder, decomposed organic fertilizer and background sandstone powder from the spoil heap; In step S107, after the material has been composted and cooled to below 30°C, 0.5% to 2.0% of a biocompatible polysaccharide binder is added to form the outer wet material. Step S108: The outer wet material obtained in step S107 is wrapped around the outside of the buffer transition layer obtained in step S105, and dried and shaped at a temperature below 35°C to form an outer layer for colonization of arbuscular mycorrhizal fungi. Step S109: After the overall temperature of the weathered coal-based multi-level ecological particles drops below 30°C, the arbuscular mycorrhizal fungal agent is loaded onto the surface and / or shallow pores of the colonized outer layer of the arbuscular mycorrhizal fungi; after loading, no further heating and composting are carried out, nor is a secondary coating layer for forming a continuous dense film applied.

7. The preparation method according to claim 6, characterized in that, In step S102, the foaming agent is betaine, the silicate cement is 8 parts by mass, the fly ash is 8 parts by mass, the phosphorus-containing mineral passivation component is 3 parts by mass, the water is 25 parts by mass, the betaine is 0.08 parts by mass, the curing temperature is 40℃, and the curing time is 7 days. In step S106, the mass ratio of weathered coal powder, decomposed organic fertilizer and background sandstone powder of the spoil heap is 5:2:1; the decomposed organic fertilizer is selected from livestock and poultry manure compost, straw compost or a combination thereof, with a carbon-nitrogen ratio of 10-25 and a seed germination index of not less than 80% as the decomposition degree control index. In step S109, the arbuscular mycorrhizal fungal agent is loaded by low-temperature spraying, roller mixing, or impregnation, and the loading temperature is not higher than 30°C.

8. The preparation method according to claim 7, characterized in that, Arbuscular mycorrhizal fungal inoculants are either Moses tube-stalk fungus inoculants or single or compound arbuscular mycorrhizal fungal inoculants that have a stable symbiotic relationship with the target host plant. The loading rate of the arbuscular mycorrhizal fungal inoculant is 0.5% to 5% of the final particle mass; the spore germination rate of the arbuscular mycorrhizal fungal inoculant before loading should not be less than 60%. The activity retention rate of arbuscular mycorrhizal fungi after the loaded particles are stored at 25℃±2℃ for 90 days is not less than 60%; and / or, the colonization rate of arbuscular mycorrhizal fungi on the roots of the host plant is not less than 60% 45 days after application.

9. A preparation apparatus for weathered coal-based multi-stage ecological particles, the preparation apparatus being used to prepare weathered coal-based multi-stage ecological particles according to any one of claims 1-5 by the preparation method according to any one of claims 6-8, characterized in that, The preparation apparatus includes: The crushing and screening unit is used to crush weathered coal and pass it through a 100-mesh sieve to obtain weathered coal powder with a particle size of less than 0.15mm. A mixing and pulping unit, connected to the crushing and screening unit, is used to mix weathered coal powder with silicate cement, fly ash, phosphorus-containing mineral passivation components, water and foaming agent to form a slurry. A curing unit, connected to the mixing and pulping unit, is used to cure the pulp at 35~45℃; The crushing and screening unit is connected to the curing unit and is used to crush and screen the cured block into phosphorus-containing mineral passivation cores of 1.5~4.5mm. The granulation and coating unit is connected to the crushing and screening unit and is used to coat the buffer transition layer wet material onto the outside of the phosphorus-containing mineral passivation core to form a buffer transition layer, and to coat the outer layer wet material onto the outside of the buffer transition layer to form an arbuscular mycorrhizal fungal colonization outer layer. The drying unit, connected to the granulation and coating unit, is used to dry and shape the coated weathered coal-based multi-stage ecological particles at a temperature below 35°C. An arbuscular mycorrhizal fungus loading unit, connected to the drying unit, is used to load arbuscular mycorrhizal fungus agent onto the surface and / or shallow pores of the outer layer of the colonized arbuscular mycorrhizal fungus after the temperature of the weathered coal-based multi-stage ecological particles has dropped below 30°C; wherein, The granulation and coating unit is a disc granulator; The arbuscular mycorrhizal fungi loading unit is a low-temperature spraying device, a roller mixing device, or an impregnation device. The preparation device also includes a temperature control module for controlling the curing temperature, drying temperature, and arbuscular mycorrhizal fungal loading temperature.

10. An application of weathered coal-based multi-level ecological particles, wherein the weathered coal-based multi-level ecological particles are weathered coal-based multi-level ecological particles according to any one of claims 1-5 or weathered coal-based multi-level ecological particles obtained by the preparation method according to any one of claims 6-8, characterized in that, Weathered coal-based multi-level ecological particles are used for soil remediation of spoil heaps in lead-bearing mining areas, heavy metal passivation remediation of degraded soils, and vegetation restoration. The weathered coal-based multi-level ecological particles are applied to seed furrows or planting layers, so that the outer layer of the colonization of the arbuscular mycorrhizal fungi is 0-30 mm away from the plant seeds or roots. The application rate of the weathered coal-based multi-level ecological particles is 1.5~3.0t / mu, and the application depth is 0~10cm in the planting layer; the host plant is selected from alfalfa, ryegrass or other plants that can establish a symbiotic relationship with the selected arbuscular mycorrhizal fungi.

Images