A porous soil matrix based on coal gangue as raw material and its preparation method and application

Abstract

The present invention belongs to the technical field of solid waste resource utilization. The present invention provides a porous soil matrix based on coal gangue as raw material, and its preparation method and application. The preparation method comprises the following steps: crushing, screening, and fluidizing calcining the coal gangue in sequence to obtain a porous soil matrix. The preparation method of the porous soil matrix of the present invention can significantly improve the total porosity of the coal gangue, increase the air permeability porosity and the water holding porosity of 0.0001 to 0.03 mm; remove the excess carbon and organic pollutants in the coal gangue that are prone to spontaneous combustion, retain sulfur, calcium, potassium and other elements, which is beneficial to plant growth while eliminating environmental pollution factors; the porous soil matrix prepared by the present invention can be combined with certain additives to make coal gangue microbial fertilizer, and can also be directly or in conjunction with biomass and gypsum solid waste to prepare coal gangue-based composite ecological soil for the restoration of the ecological environment in mining areas and the improvement of desertified soil.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization, and in particular to a porous soil matrix based on coal gangue as a raw material, and a preparation method and application thereof. Background Art

[0002] Gangue is a solid waste generated during coal mining and washing. It is a dark gray rock that is harder than coal and has a low carbon content. It is present in coal seams during coal formation and accounts for approximately 10-20% of raw coal output. The long-term accumulation of gangue not only wastes valuable land resources but also damages the ecological environment, groundwater quality, and landscape of mining areas.

[0003] Open-pit coal and ore mines lack soil, making vegetation difficult to grow and prone to geological disasters and soil erosion. Furthermore, due to both human and natural factors, the ecological environment has been damaged, leading to increasingly serious desertification. Currently, remediation of mining sites and sandy soils typically requires covering with soil from outside or using imported soil to improve the soil and then plant trees, shrubs, and grasses. In ecologically fragile areas, scarce soil resources necessitate soil from elsewhere. This exodus not only causes secondary damage to the ecological environment but also increases the cost of mine restoration due to the extraction, loading, unloading, and transportation of the soil. Furthermore, this imported soil and sand often require a period of improvement and acclimatization before it can adapt to the local soil.

[0004] Gangue contains a variety of mineral components, including carbon, sulfides, organic matter, illite, chlorite, muscovite, feldspar, pyrite, siderite, hematite, and calcite. Kaolin and quartz account for over 50% of the total, and it also contains significant amounts of trace elements such as Cu, Zn, K, and Ca, essential for crop growth. Heavy metals such as Cd, Hg, Cr, and Pb, which are harmful to crops, are all below the control standards for agricultural land. Furthermore, gangue originates from coal-bearing strata and shares similarities with local rock and soil strata, with similar composition and properties. Therefore, using gangue for ecological restoration of soils in and around mining areas can avoid the time-consuming acclimatization and improvement required due to the incompatibility of externally sourced sand and soil with the local restoration soil, while also achieving efficient resource utilization of gangue.

[0005] Patent CN109438116B discloses a method for preparing a soil conditioner using modified coal gangue and wood ash. The method involves mechanically grinding and ultrafine-activating the coal gangue in a steam mill to obtain a particle size of 2-10 μm. Wood ash (with a potassium content of 10-15%) is then added and dehydrated and ground to a size of 60-200 mesh. The two are then mixed and calcined at 600-900°C for 0.5-2 hours to produce a silicon-potassium fertilizer. This method uses a relatively small amount of coal gangue as an additive, and the calcination of the ultrafine particles obtained from the mechanically ground and ultrafine-activated coal gangue is difficult, making mass production difficult. Patent CN115108869A discloses a method for producing an organic-inorganic composite soil conditioner using coal gangue and its product. The method comprises the following steps: crushing the coal gangue and screening it to obtain coal gangue powder; leaching the coal gangue powder with alkali solution, filtering the slurry to obtain a solution containing humates, and mixing the filter residue with carbonate and sulfate auxiliary materials. The mixture is dried, calcined, cooled, and crushed to obtain a mineral element soil conditioner intermediate; and mixing the intermediate, the humate solution, and a compound containing zinc, selenium, and boron. The mixture is stirred, dried, and granulated. The granules are dried again to obtain an organic-inorganic composite soil conditioner product, which is used to improve acidic soil, replenish soil minerals and organic matter, and prevent soil compaction and pests and diseases. Because the humic acid content in coal gangue is extremely low (approximately 0.1-3%), this method uses alkaline solution to extract the humic acid from the coal gangue, which is then mixed with the calcined coal gangue. This increases the complexity of the treatment process. Furthermore, the organic-inorganic composite soil conditioner has a high alkali content, resulting in low coal gangue consumption. Patent CN109929561A discloses a formula and preparation method for an alkaline soil conditioner using coal gangue. However, this method uses a high calcination temperature and a long calcination time, does not regulate the pore structure, and the conditioner is alkaline and cannot be directly added to the soil. Patent CN113896578A discloses an organic fertilizer prepared from coal gangue and its preparation method, and patent CN115784808A discloses a method for making a soil conditioner using coal gangue. Both methods do not change the dense structure of the coal gangue, do not remove organic pollutants and heavy metals, and have a poor pore structure. Patent CN111117629A discloses a method for preparing a soil conditioner using coal gangue. The molded foam produced by this method is cured at a temperature of 20-70°C for 12-65 hours. A foaming agent, such as aluminum powder, hydrogen peroxide, and baking soda, is added. The conditioner preparation takes a long time, and the foaming agent can easily make the conditioner alkaline. Directly adding coal gangue as a filler also leaves its dense structure unchanged, leaving organic pollutants and heavy metals untreated. The pore structure of the coal gangue is poor, significantly different from that of soil, making it unsuitable for large-scale consumption of coal gangue for use as soil.Patent CN113441533B discloses a method for accelerating the transformation of waste rock into soil using coal gangue; Patent CN116140335A discloses a method for enhancing the weathering of coal gangue into soil using medium- and low-temperature waste heat. Both methods involve complex pile preparation methods and structures, make biomass combustion difficult to control, and fail to effectively regulate the pore structure of the product. Patent CN116351864A discloses a method for grading and fractionating coal gangue, as well as a method for ecological restoration of all coal gangue based on this grading and fractionation process. However, these methods fail to effectively regulate the pore structure of the product, making it unsuitable for direct use as matrix soil.

[0006] In summary, since gangue contains a certain amount of carbon, sulfur and organic pollutants, long-term stacking will cause spontaneous combustion, causing pollution to water, air or soil, and cannot be used directly to improve soil. It is necessary to use gangue as the main raw material to remove excess carbon and organic pollutants, and adjust the pore size distribution and porosity of the gangue to meet the needs of soil ventilation, water retention and fertilizer retention. The existing methods of making soil from gangue are extensive stacking or crushing and screening, which do not pay attention to the removal of harmful substances and the regulation of pore structure. It is difficult to ensure the water retention, fertilizer retention and air permeability of the soil prepared from gangue. Therefore, the research and development of a method for preparing matrix soil from gangue with appropriate pore structure regulation has good application prospects. Summary of the Invention

[0007] The purpose of the present invention is to provide a porous soil matrix based on coal gangue as raw material and a preparation method and application thereof in view of the deficiencies in the prior art.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing a porous soil matrix based on coal gangue as a raw material, comprising the following steps:

[0010] The coal gangue is crushed, screened and fluidized calcined in sequence to obtain a porous soil matrix.

[0011] Preferably, the particle size of the coal gangue after screening is 0.03 to 5 mm.

[0012] Preferably, the fluidized calcination is a one-stage calcination, the temperature of the one-stage calcination is 500-950° C., and the time of the one-stage calcination is 10-60 minutes.

[0013] Preferably, the fluidized calcination is a two-stage calcination, wherein the temperature of the first stage calcination is 500-650°C, the time of the first stage calcination is 10-30 minutes, and the temperature of the second stage calcination is 650-850°C, the time of the second stage calcination is 10-30 minutes.

[0014] The present invention also provides a porous soil matrix prepared by the preparation method, characterized in that the total porosity of the porous soil matrix is greater than 50%, the water-holding pores of 0.0001 to 0.03 mm are 25 to 35%, and the ventilation pores greater than 0.03 mm are 15 to 30%. The porous soil matrix has a pore structure suitable for soil water retention, water conservation, and fertilizer conservation required for plant growth, and the sulfur content is retained at 40 to 70%.

[0015] The present invention also provides a gangue-based composite ecological soil comprising a porous soil matrix, wherein the gangue-based composite ecological soil comprises the following components: a porous soil matrix, biomass fuel, and gypsum solid waste;

[0016] The mass ratio of the porous soil matrix, biomass fuel and gypsum solid waste is 25-100:0-60:0-15.

[0017] Preferably, the biomass fuel is one or more of distiller's grains, Chinese medicine residues, straw, biomass compressed pellet fuel and wood cellulose.

[0018] Preferably, the gypsum solid waste is one or more of phosphogypsum, desulfurized gypsum, gypsum mine waste, citric acid gypsum, fluorinated gypsum, salt gypsum, monosodium glutamate gypsum, copper gypsum, titanium gypsum, boron gypsum and discarded gypsum molds.

[0019] The present invention also provides a gangue microbial fertilizer comprising a porous soil matrix, wherein the gangue microbial fertilizer is a nitrogen-fixing bacterial fertilizer, a phosphorus bacterial fertilizer, a silicate bacterial fertilizer or a potassium bacterial fertilizer.

[0020] Preferably, the gangue microbial fertilizer comprises the following components: a porous soil matrix and additives;

[0021] The mass ratio of the porous soil matrix to the additive is 80-100:40-55.

[0022] The beneficial effects of the present invention include the following:

[0023] 1) The porous soil matrix prepared by the present invention has a pore structure suitable for the water-holding, moisture-retaining and fertilizer-retaining soil required for plant growth.

[0024] 2) When the present invention uses coal gangue as raw material to prepare the porous soil matrix, 40-70% of the sulfur in the coal gangue can be retained in the form of calcium sulfate, which not only reduces the pollution of sulfur oxides but also provides nutrients for plant growth.

[0025] 3) The method for preparing the porous soil matrix of the present invention can not only remove excess carbon and organic matter in coal gangue that are prone to spontaneous combustion, but also retain elements such as sulfur, calcium, and potassium that are beneficial to plant growth.

[0026] 4) The porous soil matrix prepared by the present invention can be combined with certain additives to make coal gangue microbial fertilizer, and can also be directly or collaboratively used with biomass and gypsum solid waste to prepare coal gangue-based composite ecological soil for the restoration of mining ecological environment and the improvement of desertified soil.

[0027] 5) The porous soil matrix prepared by the present invention can synergistically dispose of biomass and gypsum solid waste, thereby achieving comprehensive utilization of various solid wastes.

[0028] 6) The present invention adopts fluidized calcination to calcine the coal gangue, and regulates the orderly and controllable oxidation of carbon in the coal gangue by calcination temperature and time, as well as the decomposition of minerals such as kaolinite, metakaolinite, and calcium carbonate to form a pore structure, thereby controlling the oxidation rate of carbon and the decomposition rate of minerals to achieve the purpose of regulating the pore structure. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a porous soil matrix based on coal gangue as a raw material, comprising the following steps:

[0030] The coal gangue is crushed, screened and fluidized calcined in sequence to obtain a porous soil matrix.

[0031] In the present invention, the particle size of the sieved gangue is preferably 0.03 to 5 mm, more preferably 1 to 4 mm, and even more preferably 2 to 3 mm.

[0032] In the present invention, the fluidized calcination is preferably a primary calcination; the temperature of the primary calcination is preferably 500-950°C, more preferably 600-850°C, and more preferably 700-800°C; the time of the primary calcination is preferably 10-60 min, more preferably 20-50 min, and more preferably 30-40 min.

[0033] In the present invention, the fluidized calcination is preferably a two-stage calcination; wherein the temperature of the first stage calcination is preferably 500-650°C, more preferably 520-600°C, and more preferably 540-560°C; the time of the first stage calcination is preferably 10-30 min, more preferably 15-25 min, and more preferably 20 min; the temperature of the second stage calcination is preferably 650-850°C, more preferably 700-800°C, and more preferably 750°C; the time of the second stage calcination is preferably 10-30 min, more preferably 15-25 min, and more preferably 20 min.

[0034] In the present invention, the fluidized calcination equipment is preferably a fluidized calciner or a circulating fluidized bed calciner.

[0035] In the present invention, the fluidized calcination can not only regulate the pore structure of the coal gangue, but also retain 40-70% of the sulfur element in the coal gangue that is beneficial to plant growth in the form of calcium sulfate.

[0036] In the present invention, the gangue is preferably cooled after fluidized calcination; the cooling temperature is preferably 20-30°C, more preferably 22-26°C, and even more preferably 25°C.

[0037] The present invention also provides a porous soil matrix prepared by the preparation method, characterized in that the total porosity of the porous soil matrix is greater than 50%, the water-holding pores of 0.0001 to 0.03 mm are 25 to 35%, and the ventilation pores greater than 0.03 mm are 15 to 30%. The porous soil matrix has a pore structure suitable for soil water retention, water conservation, and fertilizer conservation required for plant growth, and the sulfur content is retained at 40 to 70%.

[0038] The present invention also provides a gangue-based composite ecological soil comprising a porous soil matrix, wherein the gangue-based composite ecological soil comprises the following components: a porous soil matrix, biomass fuel, and gypsum solid waste;

[0039] The mass ratio of the porous soil matrix, biomass fuel and gypsum solid waste is 25-100:0-60:0-15.

[0040] In the present invention, the mass ratio of the porous soil matrix, biomass fuel and gypsum solid waste is 25-100:0-60:0-15, preferably 45-80:15-45:5-10, more preferably 55-70:25-30:6-8, and more preferably 60-65:26-28:7.

[0041] In the present invention, the biomass fuel is preferably one or more of distiller's grains, Chinese medicine residues, straw, biomass compressed pellet fuel and wood cellulose.

[0042] In the present invention, the gypsum solid waste is preferably one or more of phosphogypsum, desulfurized gypsum, gypsum mine waste, citric acid gypsum, fluorinated gypsum, salt gypsum, monosodium glutamate gypsum, copper gypsum, titanium gypsum, boron gypsum and discarded gypsum molds.

[0043] In the present invention, when preparing composite ecological soil after calcining the coal gangue, whether to add one or more of biomass fuel and gypsum solid waste is determined based on the heavy metal content and fertility, so that the content of passivated heavy metals is within a safe and controllable range of the soil, while assisting combustion and increasing the fertility of the soil matrix.

[0044] In the present invention, the gangue-based composite ecological soil can be used for repairing the ecological environment of mining areas and improving desertified soil.

[0045] The present invention also provides a gangue microbial fertilizer comprising a porous soil matrix, wherein the gangue microbial fertilizer is a nitrogen-fixing bacterial fertilizer, a phosphorus bacterial fertilizer, a silicate bacterial fertilizer or a potassium bacterial fertilizer.

[0046] In the present invention, the gangue microbial fertilizer comprises the following components: a porous soil matrix and additives;

[0047] The mass ratio of the porous soil matrix to the additive is 80-100:40-55.

[0048] In the present invention, the mass ratio of the porous soil matrix to the additive is 80-100:40-55, preferably 85-95:45-50, and more preferably 90:48.

[0049] In the present invention, the additives are preferably biomass and fungi, and the mass ratio of biomass to fungi is preferably 40-50:0.003-0.6, more preferably 42-46:0.1-0.4, and even more preferably 43-45:0.2-0.3.

[0050] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1

[0052] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 2 mm. The gangue particles were then calcined in a fluidized bed calciner at a temperature of 650°C for 30 minutes and then cooled to 25°C to obtain a porous soil matrix.

[0053] The porous soil matrix, sugarcane residue and nitrogen-fixing bacteria were mixed in a mass ratio of 85:45:0.003 to obtain nitrogen-fixing bacterial fertilizer.

[0054] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 61.8%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 6.8 times, a carbon content reduced by 91.5%, and a sulfur content retained by 41%, providing effective pores for the preservation of nutrients, ventilation, water retention, and fertilizer retention required for plant growth.

[0055] Example 2

[0056] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 0.03 mm. The gangue particles were then calcined in a fluidized calciner at a temperature of 700°C for 20 minutes and then cooled to 20°C to obtain a porous soil matrix.

[0057] The porous soil matrix, wheat straw, Bacillus subtilis and Paenibacillus polymyxa are mixed in a mass ratio of 100:50:0.3:0.2 to obtain a silicate bacterial fertilizer.

[0058] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 74.8%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 8 times, a carbon content reduced by 100%, and a sulfur content retained by 62.5%, providing effective pores for the preservation of nutrients, ventilation, water retention, and fertilizer retention required for plant growth.

[0059] Example 3

[0060] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 5 mm. The gangue particles were then calcined in a fluidized calciner at a temperature of 800°C for 10 minutes and then cooled to 30°C to obtain a porous soil matrix.

[0061] The porous soil matrix, lignocellulose and phosphogypsum were mixed in a mass ratio of 85:10:5 to obtain gangue-based composite ecological soil.

[0062] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 84.5%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 6.7 times, a carbon content reduced by 100%, and a sulfur content retained by 47.3%, providing effective pores for the preservation of nutrients, ventilation, water retention, and fertilizer retention required for plant growth.

[0063] Example 4

[0064] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 0.75 mm. The gangue particles were then calcined in a fluidized calciner at a temperature of 550°C for 20 minutes. The fluidized calciner was then heated to 700°C, and the gangue particles were continued to be calcined for 15 minutes before being cooled to 25°C to obtain a porous soil matrix.

[0065] The porous soil matrix and fluorgypsum were mixed in a mass ratio of 85:15 to obtain the gangue-based composite ecological soil.

[0066] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 93.5%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 5.9 times, a carbon content reduced by 100%, and a sulfur content retained by 53.4%, providing effective pores for the preservation of nutrient components, ventilation, water retention, and fertilizer retention required for plant growth.

[0067] Example 5

[0068] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 1 mm. The gangue particles were then calcined in a fluidized bed calciner at a temperature of 500°C for 60 minutes and then cooled to 25°C to obtain a porous soil matrix.

[0069] The porous soil matrix and wheat straw were mixed in a mass ratio of 70:30 to obtain the gangue-based composite ecological soil.

[0070] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 77.7%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 8.9 times, a carbon content reduced by 100%, and a sulfur content retained by 59.7%, providing effective pores for the preservation of nutrients, ventilation, water retention, and fertilizer retention required for plant growth.

[0071] Example 6

[0072] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 3 mm. The gangue particles were then calcined in a fluidized calciner at a temperature of 950°C for 15 minutes and then cooled to 20°C to obtain a porous soil matrix.

[0073] The porous soil matrix, sugarcane residue and nitrogen-fixing bacteria are mixed in a mass ratio of 80:40:0.003 to obtain nitrogen-fixing bacterial fertilizer.

[0074] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 68.3%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 8.3 times, a carbon content reduced by 97.9%, and a sulfur content retained by 46.6%, providing effective pores for the preservation of nutrients, ventilation, water retention, and fertilizer retention required for plant growth.

[0075] Example 7

[0076] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 2.5 mm. The gangue particles were then calcined in a fluidized calciner at a temperature of 500°C for 30 minutes. The fluidized calciner was then heated to 650°C, and the gangue particles were calcined for another 30 minutes before being cooled to 25°C to obtain a porous soil matrix.

[0077] The porous soil matrix, corn straw and phosphogypsum were mixed in a mass ratio of 65:25:10 to obtain coal gangue-based composite ecological soil.

[0078] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 73.5%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 7.5 times, a carbon content reduced by 100%, and a sulfur content retained by 60.3%, providing effective pores for the preservation of nutrients, ventilation, water retention, and fertilizer retention required for plant growth.

[0079] Example 8

[0080] The gangue was crushed and sieved in sequence to obtain gangue particles with a particle size of 1.2 mm. The gangue particles were then calcined in a circulating fluidized bed calciner at a temperature of 650°C for 10 minutes. The fluidized bed calciner was then heated to 850°C, the gangue particles were calcined for another 10 minutes, and then cooled to 25°C to obtain a porous soil matrix.

[0081] The porous soil matrix, corn straw, Bacillus subtilis and Paenibacillus polymyxa are mixed in a mass ratio of 85:40:0.4:0.2 to obtain a silicate bacterial fertilizer.

[0082] Compared with coal gangue, the porous soil matrix prepared in this embodiment has a porosity increased by 87.7%, a water-holding pore size (pores of 0.0001 to 0.03 mm) increased by 7.8 times, a carbon content reduced by 98.7%, and a sulfur content retained by 51.9%, providing effective pores for the preservation of nutrients, ventilation, water retention, and fertilizer retention required for plant growth.

[0083] The pore structure of the coal gangue and the porous soil matrices prepared in Examples 1 to 8 was analyzed, and the results are shown in Table 1.

[0084] Table 1 Pore structure analysis results of coal gangue and porous soil matrix of Examples 1 to 8

[0085]

[0086]

[0087] As shown in Table 1, the preparation method of the porous soil matrix of the present invention can significantly improve the porosity, increase the water-holding porosity by 0.0001 to 0.03 mm, remove excess carbon in the coal gangue that easily causes spontaneous combustion, and retain sulfur that is beneficial to plant growth.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A porous soil matrix based on coal gangue as raw material, characterized in that: The porous soil matrix has a total porosity greater than 50%, water-holding pores of 0.0001 to 0.03 mm account for 25 to 35%, and air-permeable pores greater than 0.03 mm account for 15 to 30%. It has a pore structure suitable for soil water retention, water conservation, and fertilizer conservation required for plant growth, and retains 40 to 70% sulfur content. The method for preparing the porous soil matrix comprises the following steps: The coal gangue is crushed, screened, and fluidized and calcined in sequence to obtain a porous soil matrix; The fluidized calcination is a single-stage calcination or a two-stage calcination; When the fluidized calcination is a first-stage calcination, the temperature of the first-stage calcination is 500-950° C., and the time of the first-stage calcination is 10-60 minutes; When the fluidized calcination is a two-stage calcination, the temperature of the first stage calcination is 500-650°C, the time of the first stage calcination is 10-30 minutes, and the temperature of the second stage calcination is 650-850°C, the time of the second stage calcination is 10-30 minutes.

2. The porous soil matrix based on coal gangue as raw material according to claim 1, characterized in that: The particle size of the coal gangue after screening is 0.03~5mm.

3. A gangue-based composite ecological soil comprising the porous soil matrix based on gangue as raw material according to claim 1 or 2, characterized in that: The gangue-based composite ecological soil comprises the following components: the porous soil matrix according to claim 1 or 2, biomass fuel and gypsum solid waste; The mass ratio of the porous soil matrix, biomass fuel and gypsum solid waste is 25-100:0-60:0-15.

4. The gangue-based composite ecological soil according to claim 3, characterized in that: The biomass fuel is one or more of distiller's grains, Chinese medicine residues, straw, biomass compressed pellet fuel and wood cellulose.

5. The gangue-based composite ecological soil according to claim 4, characterized in that: The gypsum solid waste is one or more of phosphogypsum, desulfurized gypsum, gypsum mine waste, citric acid gypsum, fluorinated gypsum, salt gypsum, monosodium glutamate gypsum, copper gypsum, titanium gypsum, and boron gypsum.

6. A gangue microbial fertilizer comprising the porous soil matrix based on gangue as a raw material according to claim 1 or 2, characterized in that: The gangue microbial fertilizer comprises the following components: the porous soil matrix according to claim 1 or 2 and additives; The mass ratio of the porous soil matrix to the additive is 80-100:40-55; The gangue microbial fertilizer is nitrogen-fixing bacterial fertilizer, phosphorus bacterial fertilizer, silicate bacterial fertilizer or potassium bacterial fertilizer.

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