Method for changing stone desertification land into black land by using solid waste coal gangue phosphogypsum

Abstract

Based on the mineralization conditions and mineral composition of coal gangue, and the characteristics of phosphogypsum mineral crystals and the adsorption of mineral components onto gypsum crystals, mechanical separation and impurity removal technology is used to separate coal gangue into material A, which is rich in carbon fragments, and material B, which is rich in humus and contains a large number of mineral trace elements. Material A is used for resource utilization in cement plants, thermal power plants, or flotation plants. Material B, which is naturally rich in humus and contains a large number of mineral trace elements, is transformed into artificial mature black soil through water retention and air permeability modification, microbial modification with poultry and livestock manure, and continuous activation modification with earthworms and plant roots. Modified phosphogypsum and shale gangue that expands to form clay are used to make greenable concrete base layers and black soil layers, effectively transforming rocky desertification soil into high-quality black soil and continuously enhancing soil fertility.

Description

Technical Field

[0001] This invention relates to a method for the comprehensive utilization of solid waste coal gangue and phosphogypsum, and more particularly to a method for transforming rocky desertification land into high-quality arable black soil using solid waste coal gangue and phosphogypsum as the main raw materials. Background Technology

[0002] As is well known, most agricultural and forestry soils are formed from the weathering of shale, aluminosilicate minerals, on the Earth's surface. Black soil, often called the "giant panda of arable land," is the most fertile, suitable for agriculture, and possesses the greatest production potential. Black soil does not refer to black soil in general, but rather to soil with a very high humus content. Its black color comes from the blackness of the humus; the extremely high humus content gives the soil its pure black appearance. Essentially, black soil is formed by the accumulation of organic matter residue on top of the original shale weathered loess layer, which then permeates and forms a humus layer. The formation of black soil is inextricably linked to specific climatic and geological conditions. The world's three major black soil regions are all located around the 47th parallel north in the Northern Hemisphere, in the Dnieper River, Mississippi River, and Heilongjiang River basins. The soil-forming conditions are characterized by mild and humid summers and cold, dry winters, coupled with poor surface drainage leading to stagnant water. Each year, the accumulation of organic matter exceeds its decomposition, allowing plant residues to be deposited as humus over many years. This accumulation of organic matter causes the humus layer to thicken gradually, typically taking hundreds of years to form a layer just one centimeter thick. Over tens of thousands of years, this accumulation has resulted in the black soil layers in the world's three major black soil regions averaging about one meter thick (with some reaching two meters). Black soil has an extremely high content of humus and organic matter, and contains abundant essential minerals such as nitrogen, phosphorus, potassium, and magnesium, making it highly fertile. Furthermore, its good water retention capacity facilitates plant absorption. After the black soil is cultivated, the soil's water and heat conditions change, the waterlogging layer is eliminated to varying degrees, the soil aeration is improved, the heat absorption capacity is increased, the microbial activity is strengthened, the decomposition of organic matter is accelerated, more nutrients are released, the effective fertility of the soil is improved, and the soil maturation process is accelerated.

[0003] Currently, soil fertility in most parts of my country has declined beyond the red line. The average organic matter content of arable land has dropped from 6.7% to about 1.8%, and in dry land it is only about 1.2%, far below the 5%-8% level in Europe and the United States. Soil organic matter, mainly humus, is the foundation of soil fertility, and soil fertility is an important indicator of soil fertility, a key factor determining high-quality agricultural production and sustainable soil resource utilization. The gradual reduction of organic matter in arable land can even lead to land degradation (desertification, desertification, and rocky desertification). Today, rocky desertification is severe in parts of my country, affecting multiple counties and cities in eight provinces (autonomous regions and municipalities): Yunnan, Guizhou, Guangxi, Sichuan, Hunan, Hubei, Chongqing, and Guangdong. The most severe cases are concentrated in Yunnan, Guizhou, and Guangxi. As a major form of land degradation, rocky desertification inevitably impacts people's lives and livelihoods in many ways. With vegetation degradation and the intensification of rocky desertification, the soil layer becomes thinner, soil structure gradually deteriorates, soil erosion resistance decreases, and the soil becomes increasingly infertile. This directly leads to a serious consequence: a reduction in arable land output and arable land area. Simultaneously, soil erosion causes various natural disasters, severely harming people's lives and livelihoods.

[0004] On the other hand, coal remains an indispensable basic fossil energy source in my country. Coal gangue, as a major solid waste product of the coal industry, is mainly composed of aluminosilicate minerals such as shale, carbonate rock, sandstone, and residual carbon, depending on the geological and mineral conditions of the mining area. Among them, shale gangue accounts for more than 80%. It is well known that coal is formed by the slow reaction of plants under high temperature and high pressure geological conditions. However, what has been overlooked for a long time is that during the process of plants forming coal through thermal pressure, most of the humus is absorbed by aluminosilicate minerals such as shale, forming black shale. Most of the free heavy metals and fluorine are adsorbed by the natural adsorption of carbon into pure coal blocks or exist as independent mineral crystals such as arsenopyrite and phosphate rock. Through our long-term tracking and sampling analysis, we found that on average, about 81.33% of the humus in the coal formation process of shale mining areas exists in black shale, and the proportion of humus in pure coal blocks is about 18.67% on average. Harmful heavy metals such as lead, mercury, arsenic, and chromium, as well as fluorine, are mainly adsorbed in pure coal blocks or exist as independent ores. The total heavy metal content in black shale is only 14.31% on average, and the total heavy metal content of most shale coal gangue is within the safe range. Objectively speaking, shale gangue is easily weathered and expands when exposed to water. It contains abundant organic matter (mostly 15-36%) and various trace elements such as nitrogen, phosphorus, potassium, zinc, copper, selenium, and germanium, which are needed for plant growth. Its heavy metal content is safe. After decarbonization and impurity removal, it belongs to the "clean" waste residue category. It is a pure natural potential high-quality "black soil" raw material formed underground.

[0005] Because the migration, osmosis, and adsorption effects of various compounds during coal formation have long been overlooked, coupled with the interdisciplinary nature of agricultural, forestry, and arable land soil research, the resource utilization of coal gangue, a major solid waste, in my country, a country that relies heavily on coal as its primary energy source, has yielded unsatisfactory results despite decades of rapid development. The existing technological approaches for the resource utilization of coal gangue are summarized below:

[0006] 1. The technology of using coal gangue in building materials, including using coal gangue as a raw material for cement, as an admixture for cement concrete, for brick making, for making ceramsite, and for making non-fired bricks / boards with cement, has several drawbacks: firstly, the amount of coal gangue that can be disposed of is limited; secondly, it can easily lead to problems with the process or product quality stability during production; and thirdly, it increases secondary pollution.

[0007] 2. The technology of directly crushing coal gangue for roadbed / backfill material wastes valuable organic and clay resources, and poses safety hazards because shale gangue absorbs water, expands and weathers naturally.

[0008] 3. Directly crushing coal gangue and using it for coal blending wastes valuable organic and clay resources, objectively reduces the combustion performance and burnout rate of coal, and increases secondary pollution.

[0009] 4. The technology of extracting silicon and aluminum from coal gangue or extracting precious metals from kaolin has several drawbacks: firstly, the amount that can be processed is limited; secondly, it wastes valuable organic matter and clay resources; and thirdly, it increases energy consumption and causes serious secondary pollution.

[0010] 5. Coal gangue compound fertilizer production technology: Coal gangue compound fertilizer production is currently an advanced technology for the resource utilization of coal gangue worldwide. Scientists from various countries have conducted various technical studies on coal gangue fertilizer production. For example, CN202211023638.8 involves a method for preparing humic acid fertilizer from coal gangue, including the following steps: a) Obtaining powdered coal gangue as raw material for preparing humic acid fertilizer; b) Obtaining Thiobacillus ferrooxidans, diluting it, and spraying it onto the powdered coal gangue obtained in step a, and thoroughly mixing it for biological treatment and primary fermentation to form coal gangue sludge; c) Mixing the coal gangue sludge formed in step b with a specific fraction of mineral humic acid and biomass to form a mixture; d) Adding compound fermentation bacteria powder to the mixture obtained in step c, stirring and mixing it repeatedly until uniform, and then carrying out conventional solid-state fermentation treatment to complete secondary fermentation. CN202110204747.9 discloses a coal gangue mineral fertilizer and its preparation method. The fertilizer is made from coal gangue as raw material, treated with *Bacillus molybdenum* GZU-Bac01. *Bacillus molybdenum* GZU-Bac01 dissociates and releases insoluble nutrients such as phosphorus, potassium, calcium, and nitrogen from the coal gangue, converting them into available phosphorus, readily available potassium, exchangeable calcium, and hydrolyzable nitrogen—nutrients that plants can absorb—thus enabling the resource utilization of coal gangue. CN202010818225.3 provides a method for producing a coal gangue microbial fertilizer, using coal gangue as raw material and treated with *Bacillus fusiformis* GZU-Lys01 for dissociation. CN202110989784.5 discloses a microbial fungal fertilizer for coal gangue and its preparation method. The fertilizer components include or are products obtained by treating raw materials with Aspergillus fumigatus GZT-Asp01. The main component of the raw materials is coal gangue. The method of treating the raw materials with Aspergillus fumigatus GZT-Asp01 is as follows: the raw materials are crushed, and Aspergillus fumigatus GZT-Asp01 is prepared into a bacterial solution. Under continuous stirring, the bacterial solution is sprayed onto the crushed raw materials, stirred evenly, turned regularly, and the temperature is controlled. The materials are then dried to obtain the product. The microbial fungal fertilizer for coal gangue uses Aspergillus fumigatus GZT-Asp01 to treat coal gangue, which can effectively transform insoluble phosphorus, potassium, calcium, nitrogen, and other components in coal gangue into nutrients that plants can absorb, such as available phosphorus, available potassium, exchangeable calcium, and hydrolyzable nitrogen, thereby realizing the resource reuse of coal gangue. CN201910098876.7 discloses a method for producing microbial fertilizer using coal gangue as raw material. The method uses coal gangue as the base material, mixed with low-grade phosphate rock and potassium ore, and then uses *Aureobacterium* GZU-Ch01 to dissociate the coal gangue and release its useful nutrients. CN201910806578.9 discloses a method for producing coal gangue microbial mineral fertilizer, using coal gangue as raw material and dissociating it using *Stenotrophomonas maltophilia* GZU-Stm01.CN201910098301.5 This invention discloses a method for producing microbial fertilizer, which uses coal gangue as the base raw material, mixed with low-grade phosphate rock and potassium rock, and then dissociates it using Micrococcus luteus GZU-MiO2 to produce microbial fertilizer. CN202210746002.X A method for preparing silicon fertilizer from activated coal gangue includes the following steps: crushing coal gangue and organic solid waste separately to obtain coal gangue powder and organic solid waste powder; mixing the coal gangue powder and organic solid waste powder to obtain a mixture; subjecting the mixture to pyrolysis, calcination and stabilization in sequence to obtain activated material; and quenching and pulverizing the activated material in sequence to obtain the silicon fertilizer. CN202310759814.2 discloses a coal gangue fertilizer for improving soil nutrient content and its preparation method. The method transforms coal gangue into soil fertilizer containing various nutrients through steps such as crushing and screening, heating, drying, and decarbonization. The decarbonization of the coal gangue is achieved through heating. The chemical composition of the coal gangue contains more than 80% SiO2 and Al2O3. The crushing and screening selects coal gangue particles with a diameter less than 1 mm. The heating temperature is 300℃-800℃, and the heating time is 30 minutes to 2 hours. The drying temperature is 80℃-120℃, and the drying time is 2 hours to 6 hours. The decarbonization temperature is 600℃-900℃, and the decarbonization time is 30 minutes to 1 hour. CN202210151862.9 discloses a bio-organic fertilizer for saline-alkali land improvement based on coal gangue and its preparation method. The method involves grinding coal gangue using microorganisms, followed by primary crushing, drying, ball milling, and sieving through a 0.05mm sieve. Microbial inoculum and fermentation agent are added to a pit-type fermentation tank for aerobic fermentation, releasing carbon, phosphorus, potassium, silicon, calcium, and magnesium nutrients from the coal gangue. After uniform mixing, well-rotted cow and sheep manure is added, with a weight ratio of 70% coal gangue to 30% cow and sheep manure. The mixture is then balled, fermented a second time with added microbial inoculum, and dried to obtain the organic fertilizer based on coal gangue. CN201911390984.8 discloses a method for preparing an ecological improvement substrate based on coal gangue and sludge. The method involves crushing coal gangue, composting sludge, adding fly ash and a heavy metal-tolerant growth-promoting microbial agent, mixing and letting it stand for two weeks to obtain a matured ecological improvement substrate. The addition of sludge compost can release inert nutrients in coal gangue, and microbial agents can control the risk of heavy metals in sludge and coal gangue. After the coal gangue and sludge compost are mixed, the physical and chemical properties and microbial indicators of the substrate are improved and enhanced, forming an ecologically improved substrate that is similar to soil, promoting plant growth, and ultimately realizing the resource utilization of coal gangue and sludge.CN202211631712.4 discloses a method for comprehensive utilization of coal gangue, comprising the following steps: Step 1: first crushing of coal gangue; Step 2: second crushing of coal gangue fragments; Step 3: spraying diluted biological agent onto coal gangue particles, causing the coal gangue particles to undergo first fermentation to produce mixture A; Step 4: adding animal manure, animal bone meal, straw, urea, green grass, leaves, fly ash, compound fermentation bacteria powder and mixture A into a reaction vessel according to a certain proportion, stirring and mixing evenly, and allowing it to stand for second fermentation to produce mixture B; Step 5: drying; Step 6: pelletizing; Step 7: drying again. CN201510442511.3 discloses a method for producing carbonized nutrient soil from coal gangue. The key technical point is that the raw materials for carbonized coal gangue are first mixed and extruded into flaky granules, then carbonized to obtain carbonized coal gangue. The raw materials are then granulated, sterilized, and packaged as carbonized nutrient soil. The carbonized nutrient soil is composed of coal gangue, activated clay waste, attapulgite clay, bentonite, zeolite, crushed waste, water-fermented waste, vermiculite, diammonium phosphate, perlite, ferrous sulfate, and superabsorbent resin. Coal gangue carbonized nutrient soil contains a large amount of nitrogen, phosphorus, potassium, organic matter and trace elements. It is a high-quality nutrient soil with complete nutrients, high fertilizer efficiency, non-toxicity, sterility, harmlessness, odorlessness and good water retention. Coal gangue carbonized nutrient soil is suitable for planting flowers and seedlings. The production method of coal gangue carbonized nutrient soil is suitable for producing carbonized nutrient soil and nutrient substrate. CN202210247639.4 A modified coal gangue bio-organic fertilizer and its preparation method and application, wherein the modified coal gangue bio-organic fertilizer is prepared from the following components in parts by mass: 80-120 parts modified coal gangue, 20-30 parts wheat bran, 20-30 parts corn flour, 12-18 parts tea bran, 12-18 parts cottonseed flour, 8-14 parts attapulgite clay, and 26-36 parts compound microbial agent; through the calcination modification of coal gangue, the nutrients contained in the coal gangue can be fully released, and the calcined coal gangue can also serve as a carrier for the adsorption of beneficial bacteria. CN202211253441.3 discloses a method for preparing matrixed coal gangue and a seedling substrate based on coal gangue. The preparation of matrixed coal gangue includes: crushing coal gangue to obtain coal gangue particles, and mixing coal gangue particles of different particle sizes in a certain proportion; mixing biomass and water and adding it to a high-pressure hydrothermal reactor for hydrothermal carbonization reaction, and obtaining solid hydrothermal carbon and hydrothermal solution after solid-liquid separation; thoroughly mixing the mixed coal gangue particles, hydrothermal carbon, and soil to prepare matrixed coal gangue. The obtained coal gangue substrate is mixed with hydrothermal carbonization solution and a small amount of chemical fertilizer to obtain a seedling substrate. This invention fully utilizes the organic matter, oxygen-containing functional groups, and nitrogen-containing functional groups on the surface of solid hydrothermal carbon to improve the nutrient content, water retention rate, and passivation of heavy metals in the coal gangue substrate.CN202210048662.0 discloses a method for preparing coal gangue compound fertilizer and the product thereof. The preparation steps are as follows: acidic phosphate fertilizer, acidic nitrogen fertilizer and potassium permanganate are dissolved in water, and coal gangue particles are added to obtain a mixture; the mixture is microwave heated and then the water is removed to obtain coal gangue compound fertilizer. CN201310526978.7 discloses a water-retaining slow-release fertilizer material based on hollow coal gangue spheres and its preparation method. The novel water-retaining slow-release fertilizer material based on hollow coal gangue spheres of this invention consists of a hollow coal gangue sphere shell and a fertilizer core layer. The shell layer is a micron-sized hollow coal gangue sphere or a micron-sized hollow coal gangue sphere with an organic coating material on its surface. The core layer is composed of fertilizer material or a composite material containing both fertilizer and water-retaining material. The material of the core layer is first dissolved in water and then loaded into the hollow cavity of the hollow coal gangue spheres by vacuum, ultrasonic or pressure impregnation. Then, an organic coating material is applied to the outside of the hollow coal gangue spheres, sealing the porous structure of the shell and increasing the slow-release effect. As can be seen from the above and existing patents, current coal gangue fertilizer production technologies and methods mainly rely on fermentation composting, microbial decomposition, or combustion, pyrolysis, and hot water hydrolysis. Firstly, coal gangue fermentation composting, secondary fermentation, and microbial decomposition fertilizer production all require long cycles, resulting in high fertilizer production costs, low consumption volumes, and difficulty in widespread adoption. Secondly, coal gangue fertilizer production through combustion, pyrolysis, and hot water hydrolysis all require grinding and additional heat treatment, leading to extremely high energy consumption and hindering large-scale industrial processing. Thirdly, most of the aforementioned coal gangue fertilizer production methods are inadequate in treating heavy metals in the coal gangue, or may have long-term negative impacts on plant growth. 6. The simple soil covering and vegetation planting technique for coal gangue involves constructing dams, piling up coal gangue, and then covering it with soil and planting vegetation. This method has been widely adopted by coal mines in recent years due to environmental protection requirements. The basic operating model involves the coal mine acquiring land, usually nearby farmland or gullies, building dams, piling up coal gangue, and hiring people to bulldoze and fill the dams at a price of 30 yuan per ton of coal gangue, and then planting vegetation on top. The paper "Pilot Experimental Study on Artificial Soil Construction and Greening of Coal Gangue Hills" in "Safety and Environmental Engineering" (Vol.30 No.3 May 2023) fully affirms the successful experience of the Xiangshui Coal Mine in Guizhou Province in using farmland to construct dams, pile up coal gangue, and cover it with vegetation. This technique is simple and easy to implement and meets current environmental protection and greening requirements. However, it occupies existing farmland, wastes a large amount of valuable organic matter and clay resources (i.e., a large waste of naturally formed black soil resources), and is prone to causing groundwater and soil pollution.

[0011] In fact, to this day, billions of tons of humus-rich shale-type coal gangue and phosphogypsum, containing a large amount of minerals necessary for plant growth, are still being stored on land or simply covered with soil without effective treatment, continuing to harm the atmospheric environment and groundwater and soil resources. Faced with my country's current land degradation, the annual decrease in soil organic humus, the gradual depletion of land, severe desertification, and the large quantities of shale-type coal gangue "black soil" resources formed naturally over hundreds of thousands of years and phosphogypsum resources containing a large amount of trace elements needed by plants, a breakthrough new technological approach and method are urgently needed.

[0012] Secondly, in Yunnan, Guizhou, Hubei and other areas currently suffering from severe desertification, phosphogypsum, as a byproduct of the phosphate chemical industry, is a major solid waste. It has a large output, low comprehensive utilization rate, and hundreds of millions of tons of land and stockpiles. Because phosphogypsum contains unreacted phosphate rock and water-soluble phosphorus, it is acidic, and a certain amount of heavy metal ions are adsorbed on the mineral crystals of phosphogypsum, causing serious water and soil pollution incidents, which has to some extent restricted the development of the phosphate chemical industry. Existing technologies for the comprehensive utilization of phosphogypsum mainly include the production of cement retarders, building material gypsum, granular ammonium sulfate, sulfuric acid, soil amendments, agricultural compound fertilizers, mine backfilling, and roadbed materials. However, these technologies either have limited capacity for phosphogypsum disposal, or are prone to safety hazards or secondary pollution. To address the problem of phosphogypsum treatment difficulties affecting the development of the phosphate chemical industry, governments and phosphate chemical companies have had to introduce various subsidy and support policies. A completely new technological approach is needed to eliminate the heavy metal hazards in phosphogypsum, effectively utilize phosphorus, sulfur, fluorine, calcium, magnesium, potassium, and other elements in phosphogypsum while taking advantage of its recrystallization and solidification characteristics, and achieve large-scale disposal of phosphogypsum. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for transforming rocky desertification land into black soil using solid wastes such as coal gangue and phosphogypsum.

[0014] The technical solution adopted by this invention to solve its technical problem is: a method for transforming rocky desertification land into black soil using solid waste coal gangue and phosphogypsum, comprising:

[0015] (1) Solid waste pretreatment

[0016] 1) Coal gangue pretreatment: Based on the fact that carbon is difficult to biodegrade into organic humus, and that carbon has a natural adsorption characteristic for heavy metals, heavy metals in coal are either adsorbed in crystalline granular coal or exist as lumpy ore. Coal gangue is mechanically pre-separated into material A (i.e., carbon-containing debris obtained after decarbonization) and material B1 (i.e., granular shale-like gangue containing humus, after removing visible lumpy harmful minerals such as pyrite and arsenopyrite, which can be called "primary black soil"). Material A (carbon-containing material) is carbon-enriched coal gangue containing most of the small carbon particles and most of the heavy metal impurities naturally adsorbed by the coal. Material B1 (primary black soil) is coal gangue pre-separated and impurity-removed, i.e., removing most of the carbon particles that are difficult to degrade and have no practical fertilizer effect, and minimizing the possible heavy metal content, resulting in a relatively clean shale-like gangue containing humus-containing aluminosilicate minerals. Material B1 is then crushed to 1µm~1mm using crushing machinery. A mixture of 10-70% and 1mm-5mm particles, 10-50% and 5mm-20mm particles, yields raw black soil, designated as B2 material.

[0017] The A material produced from pre-separated coal gangue is a mixture of carbon-containing aluminosilicate minerals. It can be directly supplied or modified into energy-saving slag powder and then supplied to cement clinker production lines as a material for comprehensive resource utilization and coal saving, or supplied to thermal power plants for fuel power generation, or used for carbon flotation. The limestone and sandstone aggregates produced from pre-separation and impurity removal can be used to produce building sand and gravel. The pyrite and other materials produced from pre-separation and impurity removal can be used as special ore materials.

[0018] 2) Pretreatment of phosphogypsum into modified phosphogypsum: Phosphogypsum and heavy metal curing agent are mixed evenly with a mixing machine at a mass ratio of 100:1 to 15 to obtain modified phosphogypsum, designated as C1 material; or phosphogypsum is mixed evenly with cement and heavy metal curing agent at a mass ratio of 100:5 to 20:1 to 15 to obtain modified phosphogypsum, designated as C2 material; when C1 or C2 material is not completely cured, it can be used as a cementitious material; after C1 or C2 material is completely cured and granulated, it can be used as sand with potential bio-fertilizer effect;

[0019] 3) Preparation of initiating agent for poultry and livestock manure waste: Naturally age and ferment poultry and livestock manure waste for more than seven days, and use it as a fertilizer-enhancing microbial initiating agent, code-named D material;

[0020] 4) Preparation of biological phagocytic activator: Prepare healthy earthworms or soil containing earthworm eggs and excrement, code-named E material;

[0021] (2) Construct a "greenable concrete" layer for the base layer (also known as the "base layer") of rocky desertification land:

[0022] Using water-absorbing and expandable native black soil B1 (shale gangue) as aggregate and mixed with incompletely cured modified phosphogypsum C2 as cementing material, the mixture is laid on the rocky desertification land and compacted to a thickness of 200-2000 mm to form a modified phosphogypsum shale gangue layer, named the "greenable concrete" layer, which constitutes the stable layer for transforming "rocky desertification land" into "black soil". The curing and recrystallization characteristics of modified phosphogypsum not only meet the requirements of a stable and impermeable bottom layer of rocky desertification land, but also ensure that plant roots can extract elements such as phosphorus, sulfur, calcium, magnesium, and potassium from phosphogypsum, and also ensure that plant roots can fully extend into the longitudinal rock fissures below.

[0023] (3) Creating a black soil layer in rocky desertification areas: Using a mixing machine, mix raw black soil B2 material, solidified sand-granulated modified phosphogypsum C1 or C2 material, poultry and livestock manure waste initiator D material, and manure soil containing earthworm eggs E material in a mass ratio of 100:10~50:0.5~35:0.05~5 evenly, and lay it on the "green concrete" layer set in step (2) with a thickness of 500~5000mm to form a "black soil layer". Then, spray water-retaining and dust-proofing agent to make the moisture content of the black soil layer reach 10~30% by mass, forming a biochemical black soil layer; if earthworms are directly selected as the biological phagocytic activator E material, earthworms in E material can be introduced into the black soil intermittently after laying the black soil layer to phagocytose and activate the black soil.

[0024] (4) Plants continuously mature the black soil: Economic crops that can improve soil structure and fertility are planted on the black soil layer of rocky desertification land created in step (3) to continuously mature the black soil. In this way, we can quickly obtain output benefits and continuously activate and mature the black soil layer through plant biochemistry.

[0025] Furthermore, in step (1), the heavy metal ion curing agent is a commercially available aqueous solution of water glass and / or aluminate, methylsilicate, water-soluble silicone resin and / or acrylic resin.

[0026] Further, in step (3), during the process of creating the black soil layer in the rocky desertification area, a water-retaining and air-permeable agent can be directly added and mixed into the black soil. The water-retaining and air-permeable agent is 0.1 to 15% of the mass of the shale gangue raw black soil B2 material.

[0027] Furthermore, the water-retaining and breathable agent is at least one of the following: modified bentonite, montmorillonite mineral powder, sodium alginate, methylcellulose, grafted starch, carboxymethylated starch, phosphorylated starch, starch xanthate, grafted cellulose, carboxymethylated cellulose, hydroxypropylated cellulose, xanthate cellulose, water-soluble polyacrylate, polyvinyl alcohol, polyoxyalkylene, soy protein, silk protein, gluten, pectin, alginic acid, chitosan, heparin, and superabsorbent resin.

[0028] Further, in step (3), a black soil layer is created in the rocky desertification area, and modified granulated phosphogypsum or modified granulated electrolytic manganese slag can be added; the phosphorus, sulfur, iron, calcium, magnesium and manganese in the modified granulated phosphogypsum or granulated electrolytic manganese slag are used as trace element fertilizers.

[0029] Furthermore, the modified granulated phosphogypsum / modified granulated electrolytic manganese slag uses a heavy metal solidifying agent to effectively fix the heavy metal ions in the phosphogypsum / electrolytic manganese slag, preventing their migration. The granulation and solidification of heavy metals in the phosphogypsum / electrolytic manganese slag solves the problems of acidity and heavy metal ion migration, increases the permeability of the artificial soil, and inhibits the effect of sulfate ions on soil compaction.

[0030] Furthermore, the total ratio of modified granulated phosphogypsum / modified granulated electrolytic manganese slag is 1%–35% of the mass of raw black soil C material.

[0031] Furthermore, in step (3), during the process of creating the black soil layer in rocky desertification areas, one or more of the following can be added in appropriate amounts: nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, fermented kitchen waste, wood ash and biomass powder, natural soil, and burnt clay.

[0032] Furthermore, in steps (2) and (3), a heavy metal ion solidifying agent may also be added. The heavy metal ion solidifying agent is used to solidify, adsorb, and capture heavy metal ions in artificial black soil materials to form precipitates that are insoluble in water and not easily absorbed by plants, so as to achieve the purpose of removing heavy metal biological pollution; the heavy metal ion solidifying agent also includes at least one of modified bentonite powder, montmorillonite mineral powder as a cell interlayer adsorbent, xanthate esters, dithiocarbamates, and acrylic chelating agents.

[0033] Furthermore, in step (4), the economic crop that can improve soil structure and fertility is preferably one or more of the following: tallow tree, giant reed, red sorghum, super reed, tobacco, etc.

[0034] Based on the mineralization conditions and mineral composition characteristics of coal gangue, a major solid waste from the coal industry, and the mineral crystal characteristics and mineral composition distribution of phosphogypsum, a simple, low-energy-consumption, and pollution-free mechanical separation and impurity removal technology is used to separate coal gangue into material A, which is rich in carbon fragments, and material B, which is rich in humus and contains a large number of mineral trace elements. Material A is then used for resource utilization in cement plants to achieve comprehensive resource utilization and reduce physical coal consumption, or for use as fuel for power generation in thermal power plants. Material B (original black soil formed underground), which is naturally rich in humus and contains a large amount of minerals and trace elements, is transformed into artificial mature black soil through water retention and aeration modification, microbial modification with poultry and livestock manure, and continuous activation modification using earthworms and plant roots. Phosphogypsum is modified into heavy metal solidified phosphogypsum cementitious material and solidified sand granulation material. Modified phosphogypsum and shale gangue that absorbs water and expands into clay are used to make greenable concrete base layer and black soil layer, respectively. This can effectively transform rocky desertification soil into high-quality black soil and continuously enhance soil fertility.

[0035] The beneficial effects of this invention are as follows: 1. The method of producing black soil from solid waste effectively solves the problems of large-scale stockpiling and pollution of coal gangue and phosphogypsum, as well as the low resource recycling rate. It is expected to avoid the instability and potential pollution of groundwater and soil caused by using such bulk solid waste as roadbed and pit filling materials. The technology of creating black soil through decarbonization of solid waste is expected to fundamentally address the problems of nutrient deficiency, poor soil structure, low fertility, and severe wind erosion in rocky desertification areas, and can be used on a large scale for the ecological restoration of rocky desertification land; 2. It is expected to effectively resolve the problem of occupying limited farmland and continuously polluting soil and water caused by the simple soil covering and planting of billions of tons of coal gangue every year due to environmental pressure and land acquisition for dam construction and vegetation cover; 3. It can efficiently utilize various mineral components in bulk solid waste coal gangue with low energy consumption and no secondary pollution, including carbon-containing materials enriched in low-quality coal gangue for use in cement plants to reduce physical coal consumption and replace clay, the silica part of hard limestone sandstone can be used as general building sand and gravel aggregate, and shale gangue rich in humus and minerals—"natural raw black soil"—to produce artificial black soil. 4. It has pioneered the technology of using heavy metal solidified and modified phosphogypsum to make "green concrete" and solidified heavy metal granulated phosphogypsum to fertilize soil, creating technical conditions for large-scale disposal of phosphogypsum while effectively utilizing its mineral characteristics and plant nutrients; 5. It has effectively solved the problem that the quantity of "above-ground black soil" resources is very limited and non-renewable. Coal gangue pre-separation and impurity removal can obtain a large amount of valuable clean "raw black soil" buried deep underground for hundreds of thousands of years. Through simple and low-cost water-retaining and aeration modification, poultry and livestock manure induction modification, and earthworm biological phagocytosis biochemical modification, it can be quickly transformed into high-quality "mature black soil" suitable for cultivation, providing a solid technical and material foundation for the transformation of rocky desertification soil into high-quality farmland and forestry land in my country. Detailed Implementation

[0036] The embodiments of the present invention will be further described in detail below with reference to examples. Example 1

[0037] Includes the following steps:

[0038] (1) Solid waste pretreatment:

[0039] 1) Coal gangue pretreatment: Based on the fact that carbon is difficult to biodegrade into organic humus, and carbon has natural adsorption characteristics for heavy metals, heavy metals in coal are either adsorbed in crystalline granular coal or exist as lumpy ore. Coal gangue with a calorific value of 720 KJ / KG is mechanically separated into material A (i.e. carbon-containing debris obtained after decarbonization, with an average calorific value of 1217 KJ / kg after separation) and material B1 (i.e. granular shale gangue containing humus, after removing visible lumpy harmful minerals such as pyrite and arsenopyrite). Material A (carbon-containing material) is carbon-enriched coal gangue material, which contains most of the small carbon particles and most of the heavy metal impurities naturally adsorbed by coal. Coal gangue pre-separation and impurity removal removes most of the carbon particles that are difficult to degrade and have no actual fertilizer effect, and minimizes the content of possible heavy metals to obtain relatively clean shale gangue containing humic aluminosilicate minerals (B1 material - primary black soil); the B material (primary black soil) is crushed by crushing machinery to a mixed particle size of 1um~1mm (46.5%), 1mm~5mm (31.8%), and 5mm~20mm (21.7%) to obtain raw black soil (B2 material);

[0040] The A material produced from pre-separated coal gangue is a mixture of carbonaceous aluminosilicate minerals enriched with a large amount of carbon fragments. After being modified and processed into energy-saving slag powder, it is supplied to cement clinker production lines as a material for comprehensive resource utilization and coal saving. The limestone and sandstone aggregates produced from pre-separation and impurity removal are used to produce building sand and gravel; the pyrite and other materials produced from pre-separation and impurity removal are used as special ore materials.

[0041] 2) Pretreatment of phosphogypsum into modified phosphogypsum (C material): Phosphogypsum and heavy metal curing agent are mixed evenly at a mass ratio of 100:10 using a mixing machine to obtain modified phosphogypsum (C1 material). When the mixed C1 material is not completely cured, it can be used as a cementing material. After the mixed C1 material is completely cured and granulated, it can be used as sand with potential bio-fertilizer effect.

[0042] The heavy metal ion curing agent is a commercially available aqueous solution of water glass and aluminate.

[0043] 3) Preparation of initiating agent (D material) for poultry and livestock manure waste: poultry and livestock manure waste is naturally aged and fermented for fifteen days as a fertilizer-enhancing microbial initiating agent;

[0044] 4) Preparation of biological phagocytic activator (E material): Prepare soil containing earthworm eggs and excrement;

[0045] (2) Set up a "green concrete" layer on the base layer (base layer) of rocky desertification land:

[0046] Using water-absorbing and expandable material B1 (shale gangue native black soil) as aggregate and mixed with incompletely cured modified phosphogypsum C2 as cementing and solidifying material, the mixture is laid on the rocky desertification land and compacted to a thickness of 200mm to form a modified phosphogypsum shale gangue "greenable concrete" layer, which constitutes a stable layer for transforming "rocky desertification land" into "black soil". The solidification and recrystallization characteristics of modified phosphogypsum not only satisfy the bottom layer stability and impermeability of rocky desertification land, but also ensure that plant roots can extract elements such as phosphorus, sulfur, calcium, magnesium, and potassium from phosphogypsum, and also ensure that plant roots can fully extend into the longitudinal rock fissures below.

[0047] (3) Creating a black soil layer in rocky desertification areas: Using a mixing machine, shale gangue raw black soil (B2 material), solidified sand-granulated modified phosphogypsum (C1 material), poultry and livestock manure waste initiator (D material), and earthworm egg-containing manure soil (E material) are mixed evenly in a mass ratio of 100:40:20:0.5 and laid on the "green concrete" layer set in step (2) with a thickness of 500mm to form a "black soil layer". Then, a water-retaining and dust-proofing agent is sprayed to make the moisture content of the black soil layer reach 10-30% to make a biochemical black soil layer.

[0048] (4) Planting continuously matures black soil: On the black soil layer of rocky desertification land created in step (3), economic crops are planted to continuously activate and mature the black soil.

[0049] An experiment was conducted on rocky desertification land in Guizhou. Directly planting sorghum on the rocky desertification land resulted in a seedling survival rate of less than 70%, and the plants required multiple applications of nitrogen and phosphorus fertilizers during their growth. However, after modification using the method of this invention, not only was soil and water conservation effectively maintained, but the seedling survival rate also reached 98%, with vigorous growth and lush root systems. Most of the plant roots penetrated directly into the 200mm thick "greenable concrete layer," achieving high yields without the need for fertilization. After multiple sampling and homogenization, soil fertility was tested, and the fertility was basically stable, with no heavy metals detected. Example 2

[0050] Includes the following steps:

[0051] (1) Solid waste pretreatment:

[0052] 1) Coal gangue pretreatment: Based on the fact that carbon is difficult to biodegrade into organic humus, and carbon has natural adsorption characteristics for heavy metals, heavy metals in coal are either adsorbed in crystalline granular coal or exist as lumpy ore. Coal gangue with a calorific value of 850 KJ / KG is mechanically separated into material A (i.e. carbon-containing debris obtained after decarbonization, with an average calorific value of 1400 KJ / kg after separation) and material B1 (i.e. granular shale gangue containing humus, after removing visible lumpy harmful minerals such as pyrite and arsenopyrite). Material A (carbon-containing material) is carbon-enriched coal gangue, which contains most of the small carbon particles and most of the heavy metal impurities naturally adsorbed by coal. Coal gangue pre-separation and impurity removal removes most of the carbon particles that are difficult to degrade and have no actual fertilizer effect, and minimizes the content of possible heavy metals to obtain relatively clean shale gangue containing humic aluminosilicate minerals (B1 material - native black soil); B material (native black soil) is crushed into mixed particle size materials of 1um~1mm (50.2%), 1mm~5mm (36.1%), and 5mm~20mm (13.7%) using crushing machinery to obtain raw black soil (B2 material).

[0053] The A material produced by pre-separation of coal gangue is a mixture of carbonaceous aluminosilicate minerals that is enriched and directly supplied to cement clinker production lines as a material for comprehensive resource utilization and coal saving. The limestone and sandstone aggregates produced by pre-separation and impurity removal are used to produce building sand and gravel; the pyrite and other materials produced by pre-separation and impurity removal are used as special ore materials.

[0054] 2) Pretreatment of phosphogypsum into modified phosphogypsum (C material): Phosphogypsum is mixed with cement and heavy metal curing agent in a mass ratio of 100:10:5 to obtain modified phosphogypsum (C2 material); when the mixed C2 material is not completely cured, it can be used as a cementing material; when the mixed C2 material is completely cured and granulated, it can be used as sand with potential bio-fertilizer effect.

[0055] The heavy metal ion curing agent is a commercially available aqueous solution of water glass and acrylic resin.

[0056] 3) Preparation of initiator for poultry and livestock manure waste (D material): poultry and livestock manure waste that has been naturally aged and fermented for ten days is used as an initiator for fattening microorganisms.

[0057] 4) Preparation of biological phagocytic activator (E material): Prepare healthy earthworms.

[0058] (2) Set up a "green concrete" layer on the base layer (base layer) of rocky desertification land:

[0059] Using water-absorbing and expandable material B1 (shale gangue) as aggregate and mixed with incompletely cured modified phosphogypsum C2 as cementing and solidifying material, the mixture is laid on the rocky desertification land and compacted to a thickness of 1000mm to form modified phosphogypsum shale gangue "greenable concrete". This forms a stable layer for transforming "rocky desertification land" into "black soil". The solidification and recrystallization characteristics of modified phosphogypsum not only satisfy the bottom layer stability and impermeability of rocky desertification land, but also ensure that plant roots can extract elements such as phosphorus, sulfur, calcium, magnesium, and potassium from phosphogypsum, and also ensure that plant roots can fully extend into the longitudinal rock fissures below.

[0060] (3) Creating a black soil layer in rocky desertification areas: Using a mixing machine, shale gangue raw black soil (B2 material), solidified sand-granulated modified phosphogypsum (C2 material), and poultry and livestock manure waste initiator (D material) are mixed evenly in a mass ratio of 100:25:20 and laid on the "green concrete" set in step (2) with a thickness of 2500mm to form a "black soil layer". Then, a water-retaining and dust-proofing agent is sprayed to make the black soil layer have a moisture content of about 30% to make biochemical black soil; Biological phagocytosis activator preparation (E material): Earthworms are introduced into the black soil intermittently after the black soil layer is laid to phagocytize and activate the black soil.

[0061] (4) Plants continuously mature the black soil: Red sorghum is planted on the black soil layer of rocky desertification land created in step (3). The survival rate of seedlings is as high as 100%, which effectively retains water and increases fertilizer. The root system of red sorghum is well developed, which can effectively mature the black soil and achieve high yield without additional fertilization. Example 3

[0062] Includes the following steps:

[0063] (1) Solid waste pretreatment:

[0064] 1) Coal gangue pretreatment: Based on the fact that carbon is difficult to biodegrade into organic humus, and carbon has natural adsorption characteristics for heavy metals, heavy metals in coal are either adsorbed in crystalline granular coal or exist as lumpy ore. Coal gangue with a calorific value of 1350 KJ / KG is mechanically separated into material A (i.e., carbon-containing debris obtained after decarbonization, with an average calorific value of 2630 KJ / kg after separation) and material B1 (i.e., granular shale gangue containing humus, after removing visible lumpy harmful minerals such as pyrite and arsenopyrite). Material A (carbon-containing material) is carbon-enriched coal gangue material, which contains most of the small carbon particles and most of the heavy metal impurities naturally adsorbed by coal. Coal gangue pre-separation and impurity removal removes most of the carbon particles that are difficult to degrade and have no actual fertilizer effect, and minimizes the content of possible heavy metals to obtain relatively clean shale gangue containing humic aluminosilicate minerals (B1 material - primary black soil); the B material (primary black soil) is crushed by crushing machinery to a mixed particle size of 1um~1mm (22.3%), 1mm~5mm (46.1%), and 5mm~20mm (31.6%) to obtain raw black soil (B2 material);

[0065] The A material produced from pre-separated coal gangue is a mixture of carbonaceous aluminosilicate minerals that is enriched and contains a large amount of carbonaceous debris. It is directly supplied to the cement clinker production line as a material for comprehensive resource utilization and coal saving. The limestone and sandstone aggregates produced from pre-separation and impurity removal are used to produce building sand and gravel. Pyrite and other materials produced from pre-separation and impurity removal are used as special ore materials.

[0066] 2) Pretreatment of phosphogypsum into modified phosphogypsum (C material): Phosphogypsum and heavy metal curing agent are mixed evenly at a mass ratio of 100:5.5 using a mixing machine to obtain modified phosphogypsum (C1 material); when the mixed C1 material is not completely cured, it can be used as a cementing material; when the mixed C1 material is completely cured and granulated, it can be used as sand with potential bio-fertilizer effect.

[0067] The heavy metal ion curing agent is a commercially available aqueous solution of aluminate and water-soluble silicone resin.

[0068] 3) Preparation of initiating agent (D material) for poultry and livestock manure waste: poultry and livestock manure waste is naturally aged and fermented for ten days as a fertilizer-enhancing microbial initiating agent;

[0069] 4) Preparation of biological phagocytic activator (E material): Prepare healthy earthworm eggs, excrement, and soil;

[0070] (2) Install "green concrete" on the base layer (subbase) of rocky desertification land:

[0071] Using water-absorbing and expandable B1 material (shale gangue) as aggregate and mixed with incompletely cured modified phosphogypsum C1 material as cementing and solidification material, the mixture is laid on the rocky desertification land and compacted to a thickness of 800mm to form modified phosphogypsum shale gangue "greenable concrete". This forms a stable layer for transforming "rocky desertification land" into "black soil". The solidification and recrystallization characteristics of modified phosphogypsum not only satisfy the bottom layer stability and impermeability of rocky desertification land, but also ensure that plant roots can extract elements such as phosphorus, sulfur, calcium, magnesium, and potassium from phosphogypsum, and also ensure that plant roots can fully extend into the longitudinal rock fissures below.

[0072] (3) Creating a black soil layer in rocky desertification areas: Using a mixing machine, shale gangue raw black soil (B2 material), solidified sand-granulated modified phosphogypsum (C1 material), poultry and livestock manure waste initiator (D material), earthworm egg-containing manure soil (E material), and water-retaining and breathable agent modified bentonite are mixed evenly in a mass ratio of 100:32:25:5:15 and laid on the "green concrete" set in step (2) with a thickness of 3000mm to form a "black soil layer". Then, water-retaining and dust-proof agent is sprayed to make the water content of the black soil layer between 10% and 30% to make biochemical black soil.

[0073] (4) Plants continuously mature the black soil: Giant Napier grass is planted on the black soil layer of the rocky desertification area created in step (3). Giant Napier grass has a well-developed root system, grows vigorously, and has a high grass yield, which can provide green fodder continuously and effectively activate and mature the black soil. Example 4

[0074] Includes the following steps:

[0075] (1) Solid waste pretreatment:

[0076] 1) Coal gangue pretreatment: Based on the fact that carbon is difficult to biodegrade into organic humus, and carbon has natural adsorption characteristics for heavy metals, heavy metals in coal are either adsorbed in crystalline granular coal or exist as lumpy ore. Coal gangue with a calorific value of 1300 KJ / KG is mechanically separated into material A (i.e., carbon-containing debris obtained after decarbonization, with an average calorific value of 2270 KJ / kg after separation) and material B1 (i.e., granular shale gangue containing humus, after removing visible lumpy harmful minerals such as pyrite and arsenopyrite). Material A (carbon-containing material) is carbon-enriched coal gangue material, which contains most of the small carbon particles and most of the heavy metal impurities naturally adsorbed by coal. Coal gangue pre-separation and impurity removal removes most of the carbon particles that are difficult to degrade and have no actual fertilizer effect, and minimizes the content of possible heavy metals to obtain relatively clean shale gangue containing humic aluminosilicate minerals (B1 material - primary black soil); the B material (primary black soil) is crushed by crushing machinery to a mixed particle size of 1um~1mm (51.5%), 1mm~5mm (26.4%), and 5mm~20mm (22.1%) to obtain raw black soil (B2 material);

[0077] The A material produced from pre-separated coal gangue is a mixture of carbonaceous aluminosilicate minerals that is enriched and contains a large amount of carbonaceous debris. It is directly supplied to the cement clinker production line as a material for comprehensive resource utilization and coal saving. The limestone and sandstone aggregates produced from pre-separation and impurity removal are used to produce building sand and gravel. Pyrite and other materials produced from pre-separation and impurity removal are used as special ore materials.

[0078] 2) Pretreatment of phosphogypsum into modified phosphogypsum (C material): Phosphogypsum and heavy metal curing agent are mixed evenly at a mass ratio of 100:12.5 using a mixing machine to obtain modified phosphogypsum (C1 material); when the mixed C1 material is not completely cured, it can be used as a cementing material; when the mixed C1 material is completely cured and granulated, it can be used as sand with potential bio-fertilizer effect.

[0079] The heavy metal ion curing agent is a commercially available aqueous solution of water glass, methyl silicate, and acrylic resin.

[0080] 3) Pretreatment of poultry and livestock manure waste with initiating agents (D material): poultry and livestock manure waste is naturally aged and fermented for ten days as a fertilizer-enhancing microbial initiating agent;

[0081] 4) Preparation of biological phagocytic activator (E material): Soil containing earthworm eggs and excrement;

[0082] (2) Set up a "green concrete" layer on the base layer (base layer) of rocky desertification land:

[0083] Using water-absorbing and expandable B1 material (shale gangue) as aggregate and mixed with incompletely cured modified phosphogypsum C1 material as cementing and solidification material, the mixture is laid on the rocky desertification land and compacted to a thickness of 700mm to form a modified phosphogypsum shale gangue "greenable concrete" layer, which constitutes a stable layer for transforming "rocky desertification land" into "black soil". The solidification and recrystallization characteristics of modified phosphogypsum not only meet the requirements of the bottom layer of rocky desertification land to be stable and impermeable, but also ensure that plant roots can extract elements such as phosphorus, sulfur, calcium, magnesium, and potassium from phosphogypsum, and also ensure that plant roots can fully extend into the longitudinal rock fissures below.

[0084] (3) Creating a black soil layer in rocky desertification areas: Using a mixing machine, shale gangue raw black soil (B2 material), solidified sand-granulated modified phosphogypsum (C1 material), poultry and livestock manure waste initiator (D material), earthworm egg-containing manure soil (E material), and modified sand-granulated electrolytic manganese slag are mixed evenly in a mass ratio of 100:40:15:1.2:10 and laid on the "green concrete" set in step (2) with a thickness of 2800mm to form a "black soil layer". Then, a water-retaining and dust-proofing agent is sprayed to make the water content of the black soil layer between 10% and 30% to make a biochemical black soil layer.

[0085] (4) Plants continuously mature the black soil layer: Chinese tallow trees are planted on the black soil layer of the rocky desertification land created in step (3) to continuously mature the black soil, effectively retain water and facilitate the greening of the rocky desertification land and the regeneration of organic matter. At the same time, Chinese tallow trees can create high economic value for people. Example 5

[0086] Includes the following steps:

[0087] (1) Solid waste pretreatment:

[0088] 1) Coal gangue pretreatment: Based on the fact that carbon is difficult to biodegrade into organic humus, and carbon has natural adsorption characteristics for heavy metals, heavy metals in coal are either adsorbed in crystalline granular coal or exist as lumpy ore. Coal gangue with a calorific value of 1530 KJ / KG is mechanically separated into material A (i.e., carbon-containing debris obtained after decarbonization, with an average calorific value of 2820 KJ / kg after separation) and material B1 (i.e., granular shale gangue containing humus, after removing visible lumpy harmful minerals such as pyrite and arsenopyrite). Material A (carbon-containing material) is carbon-enriched coal gangue, which contains most of the small carbon particles and most of the heavy metal impurities naturally adsorbed by coal. Coal gangue pre-separation and impurity removal removes most of the carbon particles that are difficult to degrade and have no actual fertilizer effect, and minimizes the content of possible heavy metals to obtain relatively clean shale gangue containing humic aluminosilicate minerals (B1 material - primary black soil); B material (primary black soil) is crushed by crushing machinery to a mixed particle size of 1um~1mm (42.2%), 1mm~5mm (36.3%), and 5mm~20mm (21.5%) to obtain raw black soil (B2 material);

[0089] The A material produced from pre-separated coal gangue is a mixture of carbonaceous aluminosilicate minerals that is enriched and contains a large amount of carbonaceous debris. It is directly supplied to the cement clinker production line as a material for comprehensive resource utilization and coal saving. The limestone and sandstone aggregates produced from pre-separation and impurity removal are used to produce building sand and gravel. Pyrite and other materials produced from pre-separation and impurity removal are used as special ore materials.

[0090] 2) Pretreatment of phosphogypsum into modified phosphogypsum (C material): Phosphogypsum and heavy metal curing agent are mixed evenly with a mixing machine at a mass ratio of 100:4.5 to obtain modified phosphogypsum (C1 material); when the mixed C1 material is not completely cured, it can be used as a cementing material; when the mixed C1 material is completely cured and granulated, it can be used as sand with potential bio-fertilizer effect.

[0091] The heavy metal ion curing agent is a commercially available aqueous solution containing aluminate and acrylic resin;

[0092] 3) Preparation of initiating agent (D material) for poultry and livestock manure waste: poultry and livestock manure waste is naturally aged and fermented for ten days as a fertilizer-enhancing microbial initiating agent;

[0093] 4) Preparation of biological phagocytic activator (E material): Soil containing earthworm eggs, excrement, etc.

[0094] (2) Set up a "green concrete" layer on the base layer (base layer) of rocky desertification land:

[0095] Using water-absorbing and expandable B1 material (shale gangue) as aggregate and mixed with incompletely cured modified phosphogypsum C1 material as cementing and solidifying material, the mixture is laid on the rocky desertification land and compacted to a thickness of 700mm to form a modified phosphogypsum shale gangue "greenable concrete" layer, which constitutes a stable layer for transforming "rocky desertification land" into "black soil". The solidification and recrystallization characteristics of modified phosphogypsum not only satisfy the bottom layer stability and impermeability of rocky desertification land, but also ensure that plant roots can extract elements such as phosphorus, sulfur, calcium, magnesium, and potassium from phosphogypsum, and also ensure that plant roots can fully extend into the longitudinal rock fissures below.

[0096] (3) Creating a black soil layer in rocky desertification areas: Using a mixing machine, shale gangue raw black soil (B2 material), solidified sand-granulated modified phosphogypsum (C1 material), poultry and livestock manure waste initiator (D material), earthworm egg-containing manure soil (E material), modified sand-granulated electrolytic manganese slag, and heavy metal solidifying agent are mixed evenly in a mass ratio of 100:22:15:1.2:10:3 and laid on the "green concrete" set in step (2) with a thickness of 1300mm to form a "black soil layer". Then, a water-retaining and dust-proofing agent is sprayed to make the water content of the black soil layer between 10% and 30% to make a biochemical black soil layer.

[0097] (4) Plants continuously mature the black soil: Economic crops such as tobacco are planted on the black soil layer of the rocky desertification area created in step (3). The tobacco planted on the black soil layer has lush branches and leaves, grows rapidly, and has high output and income. Moreover, the tobacco root system is well developed and easy to activate and mature the black soil, so that the soil fertility will last for a long time.

Claims

1. A method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum, characterized in that, Includes the following steps: (1) Solid waste pretreatment 1) Coal gangue pretreatment: Based on the fact that carbon is difficult to biodegrade into organic humus, and that carbon has natural adsorption characteristics for heavy metals, heavy metals in coal are either adsorbed in crystalline granular coal or exist as lumpy ore. Coal gangue is mechanically sorted and pre-separated into material A and material B1. Material A is carbon-rich coal gangue containing most of the small carbon particles and most of the heavy metal impurities naturally adsorbed by the coal. Material B1 is primary black soil, which is a relatively clean humus-containing aluminosilicate mineral shale gangue obtained by pre-separation and impurity removal of coal gangue, i.e., removing most of the carbon particles that are difficult to degrade and have no actual fertilizer effect, and minimizing the possible heavy metal content. Material B1 is crushed by crushing machinery to a mixed particle size of 1um~1mm 10~70%, 1mm~5mm 10~50%, and 5mm~20mm 10~50%, to obtain primary black soil, which is designated as material B2. The A material produced from pre-separated coal gangue can be directly supplied or modified and processed into energy-saving slag powder for cement clinker production lines as a material for comprehensive resource utilization and coal saving, or supplied to thermal power plants for fuel power generation, or used for carbon flotation; the limestone and sandstone aggregates produced from pre-separation and impurity removal can be used to produce building sand and gravel; the pyrite produced from pre-separation and impurity removal can be used as a special ore material. 2) Pretreatment of phosphogypsum into modified phosphogypsum: Phosphogypsum and heavy metal curing agent are mixed evenly with a mixing machine at a mass ratio of 100:1 to 15 to obtain modified phosphogypsum, designated as C1 material; or phosphogypsum is mixed evenly with cement and heavy metal curing agent at a mass ratio of 100:5 to 20:1 to 15 to obtain modified phosphogypsum, designated as C2 material; when C1 or C2 material is not completely cured, it can be used as a cementitious material; after C1 or C2 material is completely cured and granulated, it can be used as sand with potential bio-fertilizer effect; 3) Preparation of initiating agent for poultry and livestock manure waste: Naturally age and ferment poultry and livestock manure waste for more than seven days, and use it as a fertilizer-enhancing microbial initiating agent, code-named D material; 4) Preparation of biological phagocytic activator: Prepare healthy earthworms or soil containing earthworm eggs and excrement, code-named E material; (2) Construct a "greenable concrete" layer as the base layer of the rocky desertification area: Using water-absorbing and expandable native black soil B1 as aggregate and mixed with incompletely cured modified phosphogypsum C2 as cementing and solidifying material, the mixture is laid on the rocky desertification land and compacted to a thickness of 200-2000 mm to form a modified phosphogypsum shale gangue layer, named "greenable concrete" layer, which constitutes a stable layer for transforming "rocky desertification land" into "black soil". The solidification and recrystallization characteristics of modified phosphogypsum not only satisfy the bottom layer stability and impermeability of rocky desertification land, but also ensure that plant roots can extract phosphorus, sulfur, calcium, magnesium and potassium elements from phosphogypsum, and also ensure that plant roots can fully extend into the longitudinal rock fissures below. (3) Creating a black soil layer in rocky desertification areas: Using a mixing machine, mix raw black soil B2 material, solidified sand-granulated modified phosphogypsum C1 or C2 material, poultry and livestock manure waste initiator D material, and manure soil containing earthworm eggs E material in a mass ratio of 100:10~50:0.5~35:0.05~5 evenly, and lay it on the "green concrete" layer set in step (2) with a thickness of 500~5000mm to form a "black soil layer". Then, spray water-retaining and dust-proofing agent to make the moisture content of the black soil layer reach 10~30% by mass to form a biochemical black soil layer. If earthworms are directly selected as the biological phagocytic activator E material, earthworms in E material can be introduced into the black soil intermittently after laying the black soil layer to phagocytose and activate the black soil. (4) Plants continuously mature the black soil: Economic crops that can improve soil structure and fertility are planted on the black soil layer of rocky desertification land created in step (3) to continuously mature the black soil layer.

2. The method for transforming rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 1, characterized in that, In step (1), the heavy metal curing agent is an aqueous solution containing water glass and / or aluminate, methylsilicate, water-soluble silicone resin and / or acrylic resin.

3. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 1 or 2, characterized in that, Step (3): During the process of creating the black soil layer in the rocky desertification area, a water-retaining and air-permeable agent is directly added and mixed into the black soil. The water-retaining and air-permeable agent is 0.1 to 15% of the mass of the shale gangue raw black soil B2 material.

4. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 3, characterized in that, The water-retaining and breathable agent is at least one of the following: modified bentonite, montmorillonite mineral powder, sodium alginate, methylcellulose, grafted starch, carboxymethylated starch, phosphorylated starch, starch xanthate, grafted cellulose, carboxymethylated cellulose, hydroxypropylated cellulose, xanthate cellulose, water-soluble polyacrylate, polyvinyl alcohol, polyoxyalkylene, soy protein, silk protein, gluten, pectin, alginic acid, chitosan, heparin, and superabsorbent resin.

5. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 1 or 2, characterized in that, Step (3) involves creating a black soil layer in rocky desertification areas, and also adding modified granulated phosphogypsum or modified granulated electrolytic manganese slag.

6. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 5, characterized in that, The modified granulated phosphogypsum / modified granulated electrolytic manganese slag is a modified granulated phosphogypsum / granulated electrolytic manganese slag that uses a heavy metal curing agent to effectively fix heavy metal ions in the phosphogypsum / electrolytic manganese slag, preventing their migration.

7. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 5, characterized in that, The total proportion of modified granulated phosphogypsum / granulated electrolytic manganese slag is 1%-35% of the mass of raw black soil B.

8. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 1 or 2, characterized in that, In step (3), during the process of creating the black soil layer in the rocky desertification area, one or more of the following are also added: nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, fermented kitchen waste, wood ash and biomass powder, natural soil, and burnt clay.

9. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 1 or 2, characterized in that, In steps (2) and (3), a heavy metal ion curing agent is also added. The heavy metal ion curing agent also includes at least one of modified bentonite powder, montmorillonite mineral powder as an intercellular adsorbent, and xanthate, dithiocarbamate, and acrylic chelating agents.

10. The method for converting rocky desertification land into black soil using solid waste coal gangue and phosphogypsum according to claim 1 or 2, characterized in that, In step (4), the economic crops that can improve soil structure and fertility are one or more of the following: tallow tree, giant reed, red sorghum, super reed, and tobacco.