Preparation method of iron tailing compound fertilizer and mining wasteland ecological restoration method

Abstract

The invention discloses a preparation method of an iron tailing compound fertilizer and an ecological restoration method of a mining wasteland, and belongs to the technical field of ecological restoration of the mining wasteland. According to the invention, a biomass fertilizer and a mineral fertilizer are respectively prepared, the biomass fertilizer and the mineral fertilizer are uniformly mixed to obtain the iron tailing compound fertilizer, and the biomass fertilizer is prepared by fully mixing wood sections, straw bark fibers, chippings and livestock and poultry manure and then spraying a microbial agent into the mixture for fermentation. The mineral fertilizer is prepared by uniformly mixing bentonite, fly ash, steel slag and iron tailings in sequence; the ecological restoration method for the mining wasteland comprises the following steps: transporting the iron tailing compound fertilizer to the iron mine wasteland to be ecologically restored, paving, irrigating, maintaining and performing field management to form an ecological protection layer under the combined action of vegetation, a mixed soil layer, a silk screen and wood nails in the mining wasteland. The iron tailings can be directly transformed into the soil suitable for plant growth, the usage amount of the iron tailings is large, the economical efficiency is good, the construction efficiency is high, and the remediation effect is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of ecological restoration of mine wastelands, and specifically relates to a method for preparing a composite fertilizer for iron tailings and an ecological restoration method for mine wastelands. Background Art

[0002] Iron tailings are fine-grained solid waste remaining after valuable components such as iron are selected through processes such as crushing and separation of iron ore. China is a major steel-producing country, generating more than 500 million tons of iron tailings annually, with an overall utilization rate of less than 20%. According to statistics, the historical stockpile of iron tailings in China exceeds 8 billion tons and is still increasing rapidly at a rate of 400 - 500 million tons per year. The large-scale stockpiling of iron tailings occupies a large amount of land, pollutes the atmosphere, water bodies, and soil, and large-scale tailing ponds also pose serious safety risks such as dam failures.

[0003] At the same time, large-scale spoil banks and exposed open-pit mines formed during iron ore mining need to quickly restore vegetation to reduce the ecological damage and environmental hazards caused by mining activities. The dry beach surfaces of the sub-dams and closed tailing ponds of tailing ponds also need to quickly restore vegetation to reduce dust and improve the stability of the dam body and slope. Large-scale ecological restoration of iron mine wastelands requires a large amount of soil materials. Existing ecological restoration methods for mine wastelands, such as GB / T 43933-2024 "Technical Specifications for Land Reclamation and Ecological Restoration of Metal Mines", mainly use the topsoil stripped in the early stage or borrow soil from other places to cover the surface of mine wastelands, and plant vegetation after spreading into a soil layer of a certain thickness. Such methods require a huge amount of stripped topsoil or borrow soil, resulting in high transportation costs and low construction efficiency. The restoration effect has great uncertainty due to differences in the quality and storage management quality of the stripped topsoil, and the quality and properties of the borrow soil, and it comes at the cost of damaging the land environment of the borrowing location, which does not meet the requirements of high-quality economic and social development. There are also some technologies that use the high-silicon characteristics of general iron tailings to make silicon fertilizers, or modify iron tailings for the improvement of alkaline paddy soils. These technical methods use very little iron tailings, and their implementation scenarios and objectives are not the ecological restoration of mine wastelands.

[0004] The properties of iron tailings are quite different from those of general natural soils, and it is very difficult to directly transform them into soils suitable for plant growth. First of all, there is no organic matter in iron tailings, and the nitrogen nutrient is extremely lacking; generally containing phosphorus and sulfur, but the content varies greatly; the potassium content is small or none; silicon, calcium, and magnesium are generally not lacking, but the available effectiveness is poor. Secondly, the average particle size of iron tailings is large, the sand content is high, the clay content is low, the specific surface area is small, and the water-holding and fertilizer-holding capacity is extremely poor; the bonding force between particles is weak or there is no bonding force, and the resistance to water erosion and wind erosion is poor; the total porosity is small, there are many large voids, and the ventilation and water permeability are strong, resulting in air leakage and moisture loss. Patent CN117862195A proposes a method for soilization of iron tailings using an off-site mineral decomposition biological fermentation bed. In this method, iron tailings powder, straw powder, vinegar residue, and distiller's grains are mixed, and live bacteria domesticated by iron tailings powder are inoculated to form a biological fermentation bed with a strong mineral decomposition effect. On this basis, pig breeding and high-protein forage planting are carried out, so that the physical and chemical properties and structure of iron tailings are significantly improved, and finally mature soil is formed. In this method, the use of iron tailings is deeply tied to pig breeding, involving frequent transportation, material mixing, paving, maintenance, and re-collection of iron tailings. The amount of iron tailings used is strictly restricted by the scale of pig breeding around the mining area. The soilization transformation period is long, the efficiency is low, the economy is poor, and the amount of iron tailings used is small, which is not suitable for large-scale implementation.

[0005] Therefore, it is very necessary to develop an ecological restoration directly targeting the abandoned land of iron mines, which can directly transform iron tailings into soils suitable for plant growth, without the need to take the topsoil or imported soil stripped in the early stage, with a large amount of iron tailings used, good economy, high construction efficiency, and good restoration effect, as well as a method for preparing iron tailings compound fertilizer and ecological restoration of abandoned mine land. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the above-mentioned existing technologies, and provide a method for preparing iron tailings compound fertilizer and ecological restoration of abandoned mine land, which directly targets the ecological restoration of abandoned land of iron mines, can directly transform iron tailings into soils suitable for plant growth, without the need to take the topsoil or imported soil stripped in the early stage, with a large amount of iron tailings used, good economy, high construction efficiency, and good restoration effect.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing iron tailings compound fertilizer, comprising the following steps:

[0009] Step 1: Cut the branches of woody plants into wood segments, cut and rub the crop straws into stem bark fibers and debris, and fully mix the wood segments, straw stem bark fibers and debris, and livestock and poultry manure to obtain a biomass base material;

[0010] Step 2: Activate, multiply, and dilute the EM bacterial agent into effective bacteria to obtain a microbial bacterial agent. Spray the microbial bacterial agent onto the biomass base material and stir evenly. During the stirring process, spray water at 25°C - 35°C to keep the mixture in a moist state, obtaining a biomass mixture.

[0011] Step 3: Ferment the biomass mixture. During the fermentation process, perform temperature adjustment, humidity adjustment, turning, and ventilation operations. After fermentation is completed, obtain biomass fertilizer.

[0012] Step 4: Mix bentonite, fly ash, steel slag, and iron tailings evenly in sequence to obtain mineral fertilizer.

[0013] Step 5: Mix the biomass fertilizer and the mineral fertilizer evenly to obtain iron tailings compound fertilizer.

[0014] Furthermore, for the branches of woody plants in Step 1, select the branches of arbors and / or shrubs, and cut them into wood segments with a length of 1 cm - 3 cm; the crop straw includes the remaining parts after harvesting one or several of corn, sorghum, rice, wheat, reed, peanut, soybean, potato, rape, cotton, or sugarcane, and is cut and shredded into stem bark fibers and debris with a length of 1 cm - 4 cm.

[0015] Preferably, the arbor branches refer to elm, Chinese scholartree, black locust, poplar, apple tree, etc., and the shrub branches refer to Amorpha fruticosa, lilac, boxwood, vitex, etc.

[0016] Furthermore, for the livestock and poultry manure in Step 1, it is a mixed manure formed by cow and / or sheep manure and chicken and / or pig manure, and the dry mass ratio of cow and / or sheep manure to chicken and / or pig manure is 2:(1 - 4);

[0017] The dry mass ratio of the three biomass materials of wood segments, straw stem bark fibers and debris, and livestock and poultry manure is 2:(1 - 4):(1 - 4).

[0018] Furthermore, in Step 2, the number concentration of the effective bacteria is 1×10 7 CFU / mL - 9×10 7 CFU / mL, and the moisture content of the moist state is 35% - 60%.

[0019] Furthermore, in Step 3, the fermentation lasts for 4 - 14 days.

[0020] Furthermore, in Step 4, the dry mass ratio of bentonite, fly ash, steel slag, and iron tailings is (10 - 20):(1 - 4):(1 - 4):(10 - 20). Both bentonite and steel slag are processed into powder, and the mineral fertilizer is in a dry state or a moist state with a moisture content of 30% or less.

[0021] Furthermore, in step 5, the dry mass ratio of the biomass fertilizer to the mineral fertilizer is 2:(3-6), and watering is performed according to the dryness and wetness of the biomass fertilizer and the mineral fertilizer to keep the iron tailings compound fertilizer in a moist state with an overall moisture content of 20%-40%.

[0022] The invention also provides an iron tailings compound fertilizer, which is prepared by using the preparation method of the iron tailings compound fertilizer.

[0023] The present invention also provides a method for ecological restoration of abandoned mine land, comprising the following steps:

[0024] Step 1: transporting the iron tailings compound fertilizer prepared by a method for preparing an iron tailings compound fertilizer to an abandoned iron mine site to be ecologically restored, spreading the iron tailings compound fertilizer by 3cm-5cm on the outer slope of the tailings reservoir dam or the dry beach of the tailings reservoir after closure, and then using a mixing machine to mix the site surface materials to form a 15cm-25cm mixed soil layer, and then digging trenches and ridges, sowing plants, and covering with soil;

[0025] For spoil dumps or exposed open-pit mines, the original site is renovated into a trapezoid, and then the iron tailings are spread and rolled in layers of 10cm-25cm, and water is sprinkled while rolling. Then, the iron tailings are spread by 15cm-25cm, and then the iron tailings compound fertilizer is spread by 3cm-5cm. Then, a mixing machine is used to mix the site surface materials to form a 15cm-25cm mixed soil layer, and then trenches are opened, ridges are formed, plants are sown, and soil is covered;

[0026] Preferably, a water retaining agent may be spread after the iron tailings are spread in layers and rolled.

[0027] Step 2: Lay a wire mesh on the cultivated surface of the mixed soil layer in step 1. The mesh has an aperture of 2cm-5cm. Press it with a roller. Then fix the wire mesh to the soil below with wooden nails. The length of the wooden nails is 15cm-25cm and the depth of the nails in the soil is 10cm-20cm. Then plant the plants.

[0028] Step 3: Irrigation, maintenance, and field management to form an ecological protection layer composed of vegetation in abandoned mines, mixed soil layer, wire mesh, and wooden nails.

[0029] Furthermore, the sowing method in step 1 is a combination of row sowing and broadcast sowing, and the sowing plants are mainly Gramineae, supplemented by Leguminosae and Asteraceae;

[0030] Preferably, the planted plants are Amorpha fruticosa, Syringa syringae, Vitex negundo, Hippophae rhamnoides, Platycladus orientalis and the like.

[0031] Further, before laying the wire mesh on the tillage surface of the mixed soil layer in Step 2, straw fibers and / or wood segments and / or leaves are evenly spread, with a coverage rate of over 60%. The planted plants are shrubs and / or small trees. After irrigation, maintenance, and field management in Step 3, an ecological protection layer is formed by the combined action of the vegetation on the mine waste land, the mixed soil layer, the wire mesh, the straw fibers and / or wood segments and / or leaves, and the wooden pegs.

[0032] The preparation method of an iron tailings compound fertilizer and the ecological restoration method for mine waste land of the present invention, compared with the prior art, has the following beneficial effects:

[0033] (1) It can directly transform iron tailings into soil suitable for plant growth without taking the previously stripped topsoil or imported soil. The iron tailings have a large usage amount and good economy. It can be constructed by large-scale mechanization. The sub-dams and dry beach surfaces of the tailing pond can be in-situ ecologically restored locally, and for other mine waste lands, after spreading a certain thickness of iron tailings, the iron tailings layer can be ecologically restored. The construction efficiency is high and the restoration effect is good.

[0034] (2) The reasonable combination of the wood segments of woody plants, the stem bark fibers and debris of crop straws, and the feces of cattle (sheep) and chickens (pigs) enables the biomass fertilizer to maintain good ventilation and humidity during the composting process, with good conditions for the growth and reproduction of microorganisms. The nutrient content and nutrient availability of the biomass fertilizer are both good, and at the same time, the tillage property of the mixed soil layer is improved. The wood segments play a role in supporting and arching, which can improve the air permeability during the fermentation process of the biomass fertilizer and in the mixed soil layer. The water-holding capacity and nutrient adsorption capacity of a large number of pores on the surface and inside of the wood segments are strong, and at the same time, they provide a habitat for microorganisms and are beneficial to the growth and reproduction of microorganisms. The decomposition rate of the wood segments is slow, which can keep the mixed soil layer having high air permeability, water-holding capacity, and fertilizer-holding capacity for a long time. The straw stem bark fibers and debris play a role in fluffing, which can improve the air permeability during the fermentation process of the biomass fertilizer and in the mixed soil layer. The specific surface area of the straw stem bark fibers and debris is extremely large, with extremely many tiny pores on the surface and inside, and the water-holding capacity and nutrient adsorption capacity are extremely strong. At the same time, they provide a habitat for microorganisms and are beneficial to the growth and reproduction of microorganisms. The decomposition rate of the stem bark fibers and debris is faster than that of the wood segments but much slower than that of other organic materials, which can improve the tillage quality of the mixed soil layer and maintain high air permeability, water-holding capacity, and fertilizer-holding capacity during the critical young plant growth period. The stem bark fibers are softened into filaments by rubbing, which can effectively connect and wind the mixed soil layer materials to form an integral whole, improving the resistance to water erosion and wind erosion. A large number of fine fibers, debris, and viscous substances in the feces of cattle and sheep bond and wind small particles to form large colloidal particles, which are an important basis for forming large soil aggregates. The addition of chicken manure and pig manure effectively increases the nitrogen, phosphorus, and potassium nutrient content in the biomass fertilizer, while reducing the overall C / N ratio of the biomass mixture, accelerating the composting speed of the biomass fertilizer, and improving the quick-acting property of the nutrients in the biomass fertilizer.

[0035] (3) The reasonable combination of iron tailings, bentonite, fly ash, and steel slag results in a mineral fertilizer with an appropriate ratio of coarse and fine particles, rich mineral nutrients, and an appropriate release rate. The addition of bentonite can increase the clay content in the mixed soil layer. Its large specific surface area and water absorption and swelling properties improve the water-holding, fertilizer-holding, and buffering capacities of the mixed soil layer. The increase in clay content can enhance the cohesion of each component in the mixed soil layer, improving its resistance to water and wind erosion. The increase in clay content can also increase the total porosity of the mixed soil layer, reduce the volume of large pores, lower the connectivity of large pores, increase the number and volume of small pores, and endow the mixed soil layer with appropriate aeration and water permeability. The increase in clay content is also conducive to the humification of organic matter in the mixed soil layer. Most of the humus in the soil layer combines with clay and exists in the form of organic-inorganic complexes, which can improve the water-holding, fertilizer-holding, and buffering capacities of the mixed soil layer and simultaneously improve the tillage properties of the mixed soil layer.

[0036] (4) Fly ash can disperse bentonite particles. At the same time, the spherical morphology of fly ash can improve the workability of the mineral fertilizer and prevent caking and uneven mixing caused by the direct mixing of bentonite with other wet materials. Fly ash is weakly alkaline and can adjust the pH value of the mixed soil layer. Fly ash contains available silicon and slow-release silicon components, which can provide the silicon nutrients required for the growth of plants (especially gramineous plants) and microorganisms. After fly ash is applied to the soil, a large amount of calcium ions can be released. The humus bound by calcium ion bonds has strong water stability, which helps soil aggregation and improves soil structure.

[0037] (5) Steel slag powder can further disperse bentonite particles. Steel slag powder is weakly alkaline and can adjust the pH value of the mixed soil layer. Steel slag powder contains a large amount of available silicon components, which can quickly provide the silicon nutrients required for the growth of plants (especially gramineous plants) and microorganisms. After steel slag powder is applied to the soil, a large amount of calcium ions can be released. The humus bound by calcium ion bonds has strong water stability, which helps soil aggregation and improves soil structure.

[0038] (6) Iron tailings can further disperse and homogenize each component in the mineral fertilizer. The crushing of iron ore results in a large number of mineral crystal fractures on the surface of iron tailings particles. The silicon, calcium, magnesium, etc. at the crystal fracture positions are easily activated into effective nutrients, continuously providing silicon, calcium, magnesium, etc. nutrients under the action of microorganisms and chemistry, promoting the growth of plants and microorganisms, and being conducive to the decomposition and humification of organic matter.

[0039] (7) The reasonable combination of biological fertilizer and mineral fertilizer makes the prepared iron tailings compound fertilizer contain rich available and slow-release nutrients, which can provide sufficient nutrients for all life stages of plants and soil microorganisms, contributing to the continuous generation of humus and the continuous improvement of soil structure.

[0040] (8) After spreading the iron tailings compound fertilizer, a mixing machine is used to mix the surface materials of the site to form a mixed soil layer, which can be mechanized on a large scale and has high construction efficiency. Layered spreading and rolling of the iron tailings can fill the gaps between the rock and soil materials at the bottom of the mixed soil layer, reduce the permeability coefficient at the bottom of the mixed soil layer, and reduce the loss of water and fertilizer.

[0041] (9) Laying a wire mesh on the cultivated surface can connect the straw fibers and wood segments on the upper part of the mixed soil layer, thereby improving the ability of the cultivated surface to resist rain and wind erosion; wooden nails can firmly connect the wire mesh - straw fibers and / or wood segments and / or leaves to the lower soil, further improving the ability of the cultivated surface to resist rain and wind erosion.

[0042] (10) The plants planted, such as the Poaceae family, can grow rapidly under good irrigation, maintenance and field management. The strong root system has a strong holding and connection ability, forming a protective layer of vegetation-mixed soil layer-wire mesh-straw fiber and / or wood segments and / or leaves-wooden nails, which has a good ecological restoration effect.

[0043] (11) As time goes by, inorganic particles such as iron tailings on the upper part of the mixed soil layer move downward, and the proportion of straw fibers and wood segments on the surface of the mixed soil layer increases, forming a three-dimensional blanket structure together with the wire mesh, which continues to maintain a strong ability to resist water and wind erosion; under the continuous action of microorganisms, chemistry, physics, etc., particles of iron tailings, fly ash, steel slag, etc. are continuously broken and decomposed, and the surface becomes rough from smooth, the edges disappear, the particles become smaller, the specific surface area increases, and mineral nutrients are continuously released, and the soil structure and quality of the mixed soil layer continue to improve. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with embodiments.

[0045] Example 1

[0046] A method for preparing an iron tailings compound fertilizer comprises the following steps:

[0047] Step 1: Cut elm branches into wood segments with a length of 1cm-3cm, cut corn stalks into segments and shred them into stem bark fibers and debris with a length of 1cm-4cm, mix cow dung and chicken dung, the dry mass ratio of cow dung to chicken dung is 3:2, fully mix the wood segments, straw stem bark fibers and debris, and livestock and poultry manure, the dry mass ratio of the three biomass materials is 2:3:3, prepare biomass base material, and adjust the temperature of the biomass base material to 15°C-40°C;

[0048] Step 2: The outdoor temperature is low, so adjust the temperature in the greenhouse to 15℃-35℃. Activate, expand and dilute the EM bacteria in the greenhouse to a concentration of 3×10 7Microbial inoculant at CFU / mL; in the greenhouse, spray the microbial inoculant onto the biomass base material and stir evenly at the same time. During the stirring process, spray warm water at 30 °C to make the mixture in a moist state with a moisture content of 50%. The biomass mixture is obtained. The criterion for judging the moist state is as follows: tightly hold a handful of the mixed material, there is water mark between the fingers but no water dripping, and it can be scattered when loosened and dropped to the ground is appropriate. If water juice can be squeezed out and it does not disperse when dropped to the ground, the moisture content is greater than 70%, which is not conducive to fermentation;

[0049] Step 3: Ferment the biomass mixture prepared in Step 2 in the greenhouse. During the fermentation process, carry out operations such as temperature adjustment, humidity adjustment, turning over, and ventilation to improve the fermentation efficiency and effect. When the temperature exceeds 60 °C during the fermentation process, turn over the material. Ferment for 10 days to obtain biomass fertilizer; generally, when the material is piled up for 2 to 4 days, the temperature can rise to 50 °C to 60 °C, and it can reach above 65 °C on the 3rd to 5th day. At this time, the material needs to be turned over once. Generally, there will be two more high temperatures above 60 °C during the subsequent fermentation process. When the high temperature appears, turn over the material. It can be normally fermented and completed in 7 to 10 days. The criterion for the completion of fermentation is that the stench basically disappears, the material is dark brown, and the temperature drops to normal temperature;

[0050] Step 4: Process both bentonite and steel slag into dry powder form. Mix dry fly ash into the bentonite, then mix in dry steel slag, and then mix in dry iron tailings. The mass ratio of the four materials of bentonite, fly ash, steel slag, and iron tailings is 10:3:1:15 to obtain mineral fertilizer, and the mineral fertilizer is in a dry state;

[0051] Step 5: Mix the biomass fertilizer prepared in Step 3 and the mineral fertilizer evenly while sprinkling water. The dry mass ratio of the biomass fertilizer to the mineral fertilizer is 1:2 to make an iron tailings compound fertilizer with a moisture content of 25%.

[0052] A method for ecological restoration of mine wastelands, applied to the outer slope dam and dry beach surface of the Xiaoxigou tailings pond of the Waitoushan Iron Mine as the implementation site. Construction started in mid-April 2024, including the following steps:

[0053] Step 1: Transport the iron tailings compound fertilizer to the Xiaoxigou tailings pond of the Waitoushan Iron Mine to be ecologically restored. At the outer slope of the sub-dam of the tailings pond and the implementation site of the dry beach surface of the tailings pond, spread the iron tailings compound fertilizer 4 cm thick, and then use a mixing machine to mix the surface materials of the site to form a 20 cm thick mixed soil layer. Then, dig ditches and form ridges, and broadcast the seeds of Setaria viridis, Eleusine indica, and alfalfa in rows at an interval of 30 cm. Scatter a small amount of seeds of Setaria viridis and Eleusine indica, and cover the soil about 2 cm - 4 cm thick after sowing;

[0054] Step 2: Evenly spread a thin layer of shredded rice straw fibers and wood segments on the cultivated surface completed in Step 1. The wood segments are cut from trees with a length of 1 cm - 3 cm, and the coverage rate reaches over 70%. Then, lay a wire mesh with a pore size of 3 cm and roll it with a roller. After that, fix the wire mesh to the underlying soil with wooden pegs. The length of the wooden pegs is 20 cm, and the depth of driving into the soil is 16 cm. Then, plant 2-year-old Amorpha fruticosa seedlings with a height of 60 cm in rows with a row spacing of 6 m (plant spacing is 50 cm);

[0055] Step 3: Irrigate, maintain, and conduct field management to form an ecological protection layer with the combined action of the vegetation on the abandoned mine land - the mixed soil layer - the wire mesh - the straw fibers and wood segments - the wooden pegs.

[0056] Observation in late September 2024 showed that the vegetation coverage rate of the implementation area on the outer slope of the sub-dam of the tailings pond reached 84%. The stems and roots of the plants, straw fibers, wood segments, and the wire mesh were intertwined and cross-linked with the surface soil to form a carpet-like shape, and there were no obvious erosion gullies on the slope, achieving a good ecological restoration effect; the vegetation coverage rate of the implementation area on the dry beach surface of the tailings pond reached 90%. The stems and roots of the plants, straw fibers, wood segments, and the wire mesh were intertwined and cross-linked with the surface soil to form a carpet-like shape, and there was no rain splash erosion on the surface, achieving a good ecological restoration effect.

[0057] Example 2

[0058] A preparation method of an iron tailings compound fertilizer, comprising the following steps:

[0059] Step 1: Cut the branches of Robinia pseudoacacia into wood segments with a length of 1 cm - 3 cm, cut and shred the rice straw into stem bark fibers and debris with a length of 1 cm - 4 cm, mix cow manure, sheep manure, and pig manure, and the dry mass ratio of cow manure, sheep manure, and pig manure is 3:1:3. Fully mix the wood segments, straw stem bark fibers and debris, and livestock manure, and the dry mass ratio of the three biomass materials is 2:2:3 to obtain a biomass base material;

[0060] Step 2: When the outdoor temperature is relatively low, adjust the temperature in the greenhouse to 15°C - 35°C, activate, propagate, and dilute the EM bacterial agent in the greenhouse to a microbial bacterial agent with an effective bacteria concentration of 4×10 7 CFU / mL; in the greenhouse, spray the microbial bacterial agent into the biomass base material and stir evenly at the same time. During the stirring process, spray warm water at 30°C to make the mixture in a moist state with a moisture content of 50% to obtain a biomass mixture;

[0061] Step 3: Ferment the biomass mixture prepared in Step 2. During the fermentation process, perform operations such as temperature adjustment, humidity adjustment, turning, and ventilation to improve the fermentation efficiency and effect, and ferment for 12 days to obtain a biomass fertilizer;

[0062] Step 4: Process bentonite and steel slag into dry powder, mix dry fly ash into bentonite, then mix dry steel slag, and then mix wet iron tailings, the dry weight ratio of bentonite, fly ash, steel slag and iron tailings is 10:3:1:15, and obtain a mineral fertilizer with a moisture content of 15%;

[0063] Step 5: The biomass fertilizer prepared in step 3 and the mineral fertilizer prepared in step 4 are mixed evenly while being sprinkled with water, the dry weight ratio of the biomass fertilizer to the mineral fertilizer being 2:3, and an iron tailings compound fertilizer having a moisture content of 30% is prepared.

[0064] A method for ecological restoration of abandoned mine land is applied to the south slope of the Waitoushan Iron Mine spoil dump as the implementation site. Construction will begin in mid-April 2024 and include the following steps:

[0065] Step 1: Repair the dump site into a trapezoidal shape, then spread and roll the iron tailings in layers for 15m, sprinkle water while rolling to improve the compaction efficiency and effect, and then spread the iron tailings for 20cm; transport the iron tailings compound fertilizer to the dump site and spread 5cm, then use a mixing machine to mix the site surface materials to form a 25cm mixed soil layer, then dig trenches and ridges, sow white spear and bluegrass seeds at 30cm row spacing, sow a small amount of crabgrass and goosegrass seeds, and cover with 2cm-4cm of soil after sowing;

[0066] Step 2: evenly spread a thin layer of a mixture of wheat straw shredded fiber, wood segments and leaves on the cultivated surface completed in step 1, wherein the wood segments are shrubs cut into a length of 1cm-3cm, and the leaves are a mixture of elm leaves, willow leaves and locust leaves, with a coverage rate of more than 60%, and then lay a wire mesh with an aperture of 4cm; use a roller to press it, and then use wooden nails to fix the wire mesh to the soil below, the length of the wooden nails is 22cm, and the depth of the nails in the soil is 20cm, and then plant 2-year-old, 60cm high Amorpha fruticosa seedlings (plant spacing 50cm) and 2-year-old, 30cm high seabuckthorn seedlings (plant spacing 100cm) in rows with a row spacing of 10m;

[0067] Step 3: Irrigation, maintenance, and field management to form an ecological protection layer composed of vegetation on abandoned mine land - mixed soil layer - wire mesh - straw fiber and wood segments - wooden nails.

[0068] According to observations in late September 2024, the vegetation coverage rate of the spoil dump site reached 85%. The stems and roots of plants, straw fibers, wood segments, and wire mesh intertwined and cross-linked surface soil formed a carpet-like shape, and there were no obvious gullies on the slope, achieving good ecological restoration effects.

[0069] Example 3

[0070] A method for preparing an iron tailings compound fertilizer comprises the following steps:

[0071] Step 1: Cut the branches of Robinia pseudoacacia into woody segments with a length of 1cm-3cm, cut rice straw into segments and shred the stem bark fibers and debris with a length of 1cm-4cm; mix cow dung, sheep dung and pig dung, and the dry mass ratio of cow dung, sheep dung and pig dung is 3:1:3; fully mix the woody segments, straw stem bark fibers and debris, and livestock and poultry manure, and the dry mass ratio of the three biomass materials is 2:2:3, to obtain a biomass base material;

[0072] Step 2: When the outdoor average temperature exceeds 12°C, adjust the indoor temperature to 15°C-35°C, activate, propagate and dilute the EM bacteria to a concentration of 4×10 7 CFU / mL of microbial agent; spray the microbial agent into the biomass base material outdoors and stir it evenly at the same time, and spray warm water at 30°C during the stirring process to make the mixture in a moist state with a moisture content of 45%, thereby preparing a biomass mixture;

[0073] Step 3: fermenting the biomass mixture obtained in step 2, performing temperature and humidity control, turning over, ventilation and other operations during the fermentation process to improve the fermentation efficiency and effect, and obtaining the biomass fertilizer after fermentation for 8 days;

[0074] Step 4: Process bentonite and steel slag into dry powder. Mix dry fly ash into bentonite, then dry steel slag, and then wet iron tailings. The mass ratio of bentonite, fly ash, steel slag and iron tailings is 10:3:2:20, and a mineral fertilizer with a moisture content of 18% is obtained;

[0075] Step 5: The biomass fertilizer prepared in step 3 and the mineral fertilizer prepared in step 4 are mixed evenly while being sprinkled with water, the dry weight ratio of the biomass fertilizer to the mineral fertilizer being 2:4, to prepare an iron tailings compound fertilizer with a moisture content of 25%.

[0076] A method for ecological restoration of abandoned mine land is applied to the southern slope of the abandoned open-pit mine of Dadingzi, Beitai Iron Mine. Construction will start in mid-May 2024, including the following steps:

[0077] Step 1: The implementation site on the south slope of the abandoned open-pit mine in Dadingzi was renovated into a trapezoidal shape, and then the iron tailings were spread and rolled in layers for 15m, and water was sprinkled during rolling to improve the compaction efficiency and effect, and then the iron tailings were spread for 25cm; the iron tailings compound fertilizer was transported to the implementation site and spread for 4cm, and then a mixing machine was used to mix the surface materials of the site to form a 25cm mixed soil layer, and white spear and bluegrass seeds were sown, and a small amount of crabgrass and goosegrass seeds were sown, and then 2cm-4cm of soil was covered;

[0078] Step 2: Evenly spread a thin layer of wheat straw shredded fibers and wood segments on the tillage surface completed in Step 1. The wood segments are cut from trees and shrubs with a length of 1 cm - 3 cm, and the coverage rate reaches over 70%. Then lay a wire mesh with a pore size of 3 cm; use a roller to compact it, and then fix the wire mesh to the underlying soil with wooden pegs. The length of the wooden pegs is 22 cm, and the depth of driving into the soil is 20 cm. Then plant 2 rows of 2-year-old Amorpha fruticosa seedlings with a height of 60 cm (spacing between plants is 50 cm) at a row spacing of 4 m, and then plant 1 row of 2-year-old Hippohae rhamnoides seedlings with a height of 30 cm (spacing between plants is 100 cm) in rows at a row spacing of 6 m. Then plant 2 rows of 2-year-old Amorpha fruticosa seedlings with a height of 60 cm (spacing between plants is 50 cm) and 1 row of 2-year-old Hippohae rhamnoides seedlings with a height of 30 cm (spacing between plants is 100 cm) at intervals of 6 m, 4 m, and 6 m, and so on to form a combination of 2 rows of Amorpha fruticosa and 1 row of Hippohae rhamnoides;

[0079] Step 3: Irrigate, maintain, and conduct field management to form an ecological protection layer with the combined action of the vegetation on the abandoned mine land - mixed soil layer - wire mesh - straw fibers and wood segments - wooden pegs.

[0080] Observation in late September 2024 showed that the vegetation coverage rate of the implementation site on the south slope of the abandoned open-pit mine of Dadingshan in Beitai Iron Mine reached 85%. The stems and roots of plants, straw fibers, wood segments, and the wire mesh were wound and cross-linked with the surface soil to form a carpet-like shape, and there were no obvious gullies on the slope, achieving a good ecological restoration effect.

[0081] Example 4

[0082] A preparation method of an iron tailing compound fertilizer includes the following steps:

[0083] Step 1: Cut the branches of Robinia pseudoacacia into wood segments with a length of 1 cm - 3 cm, and cut and shred the rice straw into stem skin fibers and debris with a length of 1 cm - 4 cm. Mix cow manure, sheep manure, chicken manure, and pig manure, and the dry mass ratio of cow manure, sheep manure, chicken manure, and pig manure is 3:1:1:1; fully mix the wood segments, straw stem skin fibers and debris, and livestock and poultry manure, and the dry mass ratio of the three biomass materials is 2:4:1 to obtain a biomass base material;

[0084] Step 2: At an environmental temperature of 15°C - 35°C, activate, propagate, and dilute the EM bacterial agent into a microbial bacterial agent with an effective bacteria number concentration of 1×10 7 CFU / mL; outdoors, spray the microbial bacterial agent into the biomass base material and stir evenly at the same time. During the stirring process, spray warm water at 25°C to make the mixture in a moist state with a moisture content of 35% to obtain a biomass mixture;

[0085] Step 3: Ferment the biomass mixture obtained in Step 2. During the fermentation process, operations such as temperature adjustment, humidity adjustment, turning, and ventilation are carried out to improve the fermentation efficiency and effect. Ferment for 14 days to obtain bio-fertilizer;

[0086] Step 4: Process both bentonite and steel slag into dry powder form. Mix dry fly ash into bentonite, then mix in dry steel slag, and then mix in wet iron tailings. The mass ratio of the four materials of bentonite, fly ash, steel slag, and iron tailings is 15:1:3:10 to obtain mineral fertilizer with a moisture content of 20%;

[0087] Step 5: While sprinkling water, uniformly mix the bio-fertilizer obtained in Step 3 and the mineral fertilizer obtained in Step 4. The dry mass ratio of the bio-fertilizer to the mineral fertilizer is 2:5 to prepare iron tailings compound fertilizer with a moisture content of 20%.

[0088] A method for ecological restoration of mine wastelands, applied to the outer slope dam and dry beach surface of the Xiaoxigou tailings pond of the Waitoushan Iron Mine. Construction started in mid-April 2024 and includes the following steps:

[0089] Step 1: Transport the iron tailings compound fertilizer to the Xiaoxigou tailings pond of the Waitoushan Iron Mine to be ecologically restored. On the outer slope of the tailings pond sub-dam and the dry beach surface of the tailings pond, spread the iron tailings compound fertilizer 3 cm thick, and then use a mixing machine to mix the surface materials of the site to form a 15 cm thick mixed soil layer. Then, dig ditches and form ridges, plant 2-year-old, 60 cm tall Amorpha fruticosa seedlings in rows with a row spacing of 6 m (plant spacing 50 cm), broadcast Setaria viridis, Eleusine indica, and alfalfa seeds in strips with a row spacing of 30 cm, scatter a small amount of Setaria viridis and Eleusine indica seeds, and cover the soil about 2 cm - 4 cm after sowing;

[0090] Step 2: Lay a wire mesh on the tillage surface completed in Step 1. The aperture of the wire mesh is 2 cm, use a roller to press it, and then fix the wire mesh to the underlying soil with wooden pegs. The length of the wooden pegs is 15 cm, and the depth of driving into the soil is 10 cm. Then, plant 1-year-old, 30 cm tall Amorpha fruticosa seedlings in rows with a row spacing of 6 m (plant spacing 50 cm);

[0091] Step 3: Irrigate, maintain, and conduct field management to form an ecological protection layer with the combined action of mine wasteland vegetation - mixed soil layer - wire mesh - wooden pegs.

[0092] Observation in late September 2024 showed that the vegetation coverage rate of the implementation site on the outer slope of the tailings pond sub-dam reached 80%. The stems and roots of the plants, and the wire mesh wound and cross-linked the surface soil into a carpet shape, and there were no obvious erosion gullies on the slope, achieving a good ecological restoration effect; the vegetation coverage rate of the implementation site on the dry beach surface of the tailings pond reached 83%. The stems and roots of the plants, and the wire mesh wound and cross-linked the surface soil into a carpet shape, and there was no rain splash erosion phenomenon on the surface, achieving a good ecological restoration effect.

[0093] Example 5

[0094] A method for preparing an iron tailings compound fertilizer comprises the following steps:

[0095] Step 1: Cut the branches of Robinia pseudoacacia into woody segments with a length of 1cm-3cm, cut rice straw into segments and shred the stem bark fibers and debris with a length of 1cm-4cm, mix sheep manure, chicken manure and pig manure, the dry mass ratio of the sheep manure, chicken manure and pig manure is 1:1:4, fully mix the woody segments, straw stem bark fibers and debris, and livestock and poultry manure, the dry mass ratio of the three biomass materials is 2:1:4, and prepare the biomass base material;

[0096] Step 2: Activate, expand and dilute the EM agent to a concentration of 9×10 effective bacteria at an ambient temperature of 15°C-35°C. 7 CFU / mL of microbial agent; spray the microbial agent on the biomass base material outdoors and stir it evenly at the same time, and spray warm water at 35°C during the stirring process to make the mixture in a moist state with a moisture content of 55%, thereby preparing a biomass mixture;

[0097] Step 3: fermenting the biomass mixture obtained in step 2, performing temperature and humidity control, turning over, ventilation and other operations during the fermentation process to improve the fermentation efficiency and effect, and obtaining biomass fertilizer after fermentation for 4 days;

[0098] Step 4: Process bentonite and steel slag into dry powder. Mix dry fly ash into bentonite, then dry steel slag, and then wet iron tailings. The mass ratio of bentonite, fly ash, steel slag and iron tailings is 20:4:4:10, and a mineral fertilizer with a moisture content of 25% is obtained;

[0099] Step 5: The biomass fertilizer prepared in step 3 and the mineral fertilizer prepared in step 4 are mixed evenly while being sprinkled with water, the dry weight ratio of the biomass fertilizer to the mineral fertilizer being 2:6, and an iron tailings compound fertilizer having a moisture content of 35% is prepared.

[0100] A method for ecological restoration of abandoned mine land is applied to the south slope of the Waitoushan Iron Mine spoil dump as the implementation site. Construction will begin in mid-April 2024 and include the following steps:

[0101] Step 1: Repair the dump site into a trapezoidal shape, then spread and roll the iron tailings 10 cm in layers, sprinkle water while rolling to improve the compaction efficiency and effect, and then spread the iron tailings 15 cm; transport the iron tailings compound fertilizer to the dump site and spread 3 cm, then use a mixing machine to mix the site surface materials to form a 15 cm mixed soil layer, then dig trenches and ridges, sow white spear and bluegrass seeds at 30 cm row spacing, sow a small amount of crabgrass and goosegrass seeds, and cover with 2 cm-4 cm of soil after sowing;

[0102] Step 2: Evenly spread a thin layer of wheat straw shredded fibers and wood segments on the cultivated surface completed in Step 1. The wood segments are cut from trees and shrubs with a length of 1 cm - 3 cm, and the coverage rate reaches more than 80%. Then lay a wire mesh with a pore size of 5 cm; use a roller to compact it, and then fix the wire mesh to the underlying soil with wooden pegs. The length of the wooden pegs is 25 cm, and the depth of driving into the soil is 20 cm; then plant 1-year-old Amorpha fruticosa seedlings with a height of 30 cm (spacing between plants is 50 cm) and 2-year-old Hippohae rhamnoides seedlings with a height of 30 cm (spacing between plants is 100 cm) in rows at an interval of 10 m.

[0103] Step 3: Irrigate, maintain, and conduct field management to form an ecological protection layer with the combined action of the vegetation on the mine waste land - the mixed soil layer - the wire mesh - the straw fibers and wood segments - the wooden pegs.

[0104] Observation in late September 2024 shows that the vegetation coverage rate of the waste dump implementation site reaches 85%. The stems and roots of plants, straw fibers, wood segments, and the wire mesh are wound and cross-linked with the surface soil to form a carpet-like shape, and there are no obvious gullies on the slope, achieving a good ecological restoration effect.

[0105] Example 6

[0106] A preparation method of an iron tailing compound fertilizer includes the following steps:

[0107] Step 1: Cut the branches of Robinia pseudoacacia into wood segments with a length of 1 cm - 3 cm, and cut and shred the rice straw into stem bark fibers and debris with a length of 1 cm - 4 cm. Mix cow manure, sheep manure, and pig manure, and the dry mass ratio of cow manure, sheep manure, and pig manure is 3:1:3; fully mix the wood segments, straw stem bark fibers and debris, and livestock and poultry manure, and the dry mass ratio of the three biomass materials is 2:2:3 to obtain a biomass base material.

[0108] Step 2: At an environmental temperature of 15°C - 35°C, activate, propagate, and dilute the EM bacterial agent into a microbial bacterial agent with an effective bacteria concentration of 4×10 7 CFU / mL; outdoors, spray the microbial bacterial agent into the biomass base material and stir evenly at the same time. During the stirring process, spray warm water at 30°C to make the mixture in a moist state with a moisture content of 60% to obtain a biomass mixture; Step 3: Ferment the biomass mixture prepared in Step 2. During the fermentation process, conduct operations such as temperature adjustment, humidity adjustment, turning over, and ventilation to improve the fermentation efficiency and effect, and ferment for 12 days to obtain a biomass fertilizer.

[0109] Step 4: Process bentonite and steel slag into dry powder form. Mix dry fly ash into bentonite, then mix in dry steel slag, and then mix in moist iron tailings. The mass ratio of the four materials of bentonite, fly ash, steel slag, and iron tailings is 10:3:1:15 to obtain a mineral fertilizer with a moisture content of 30%.

[0110] Step 5: While sprinkling water, evenly mix the biomass fertilizer prepared in Step 3 with the mineral fertilizer prepared in Step 4. The dry mass ratio of the biomass fertilizer to the mineral fertilizer is 2:3, and an iron tailings compound fertilizer with a moisture content of 40% is prepared.

[0111] A method for ecological restoration of mine wasteland, which is applied to the outer slope dam and dry beach surface of the Xiaoxigou Tailings Pond of the Waitoushan Iron Mine as the implementation site. Construction started in mid-April 2024 and includes the following steps:

[0112] Step 1: Transport the iron tailings compound fertilizer to the Xiaoxigou Tailings Pond of the Waitoushan Iron Mine to be ecologically restored. At the outer slope of the sub-dam of the tailings pond and the dry beach surface of the tailings pond implementation site, spread the iron tailings compound fertilizer with a thickness of 5 cm, and then use a mixing machine to mix the surface materials of the site to form a mixed soil layer with a thickness of 25 cm. Then, dig ditches and form ridges, and broadcast the seeds of Setaria viridis, Eleusine indica, and Medicago sativa in rows at an interval of 30 cm row spacing, and scatter a small amount of seeds of Setaria viridis and Eleusine indica. After sowing, cover the soil with a thickness of about 2 cm - 4 cm;

[0113] Step 2: Evenly spread a thin layer of wheat straw shredded fibers and wood segments on the cultivated surface completed in Step 1. The wood segments are cut from trees and shrubs with a length of 1 cm - 3 cm, and the coverage rate reaches more than 60%. Then, lay a wire mesh with a pore size of 4 cm, and use a roller to press it. Then, fix the wire mesh to the underlying soil with wooden nails. The length of the wooden nails is 22 cm, and the depth of driving into the soil is 20 cm. Then, plant 1-year-old Amorpha fruticosa seedlings with a height of 30 cm in rows at a row spacing of 6 m (plant spacing is 50 cm);

[0114] Step 3: Irrigate, maintain, and conduct field management to form an ecological protection layer with the combined action of mine wasteland vegetation - mixed soil layer - wire mesh - straw fibers and wood segments - wooden nails.

[0115] Observation in late September 2024 showed that the vegetation coverage rate of the implementation site on the outer slope of the sub-dam of the tailings pond reached 85%. The stems and roots of the plants, straw fibers, wood segments, and wire mesh were wound and cross-linked with the surface soil to form a carpet-like shape, and there were no obvious gullies on the slope, achieving a good ecological restoration effect; the vegetation coverage rate of the implementation site on the dry beach surface of the tailings pond reached 95%. The stems and roots of the plants, straw fibers, wood segments, and wire mesh were wound and cross-linked with the surface soil to form a carpet-like shape, and there was no rain splash erosion phenomenon on the surface, achieving a good ecological restoration effect.

[0116] Example 7

[0117] A method for preparing an iron tailings compound fertilizer, including the following steps:

[0118] Step 1: Cut the branches of Robinia pseudoacacia into woody segments with a length of 1cm-3cm, cut rice straw into segments and shred the stem bark fibers and debris with a length of 1cm-4cm. Mix cow dung, sheep dung and pig dung, with the dry mass ratio of cow dung, sheep dung and pig dung being 3:1:3; fully mix the woody segments, straw stem bark fibers and debris, and livestock and poultry dung, with the dry mass ratio of the three biomass materials being 2:2:3, to obtain the biomass base material;

[0119] Step 2: Activate, expand and dilute the EM agent to a concentration of 6×10 effective bacteria at an ambient temperature of 15°C-35°C. 7 CFU / mL of microbial agent; spray the microbial agent into the biomass base material outdoors and stir it evenly at the same time, and spray warm water at 30°C during the stirring process to make the mixture in a moist state with a moisture content of 45%, thereby preparing a biomass mixture;

[0120] Step 3: fermenting the biomass mixture obtained in step 2, and performing temperature and humidity control, overturning, ventilation and other operations during the fermentation process to improve the fermentation efficiency and effect, and obtaining the biomass fertilizer after fermentation for 7 days;

[0121] Step 4: Process bentonite and steel slag into dry powder. Mix dry fly ash into bentonite, then dry steel slag, and then wet iron tailings. The mass ratio of bentonite, fly ash, steel slag and iron tailings is 10:3:2:20, and a mineral fertilizer with a moisture content of 18% is obtained;

[0122] Step 5: The biomass fertilizer prepared in step 3 and the mineral fertilizer prepared in step 4 are mixed evenly while being sprinkled with water, the dry weight ratio of the biomass fertilizer to the mineral fertilizer being 2:4, to prepare an iron tailings compound fertilizer with a moisture content of 25%.

[0123] A method for ecological restoration of abandoned mine land is applied to the southern slope of the abandoned open-pit mine of Dadingzi, Beitai Iron Mine. Construction will start in mid-May 2024, including the following steps:

[0124] Step 1: The implementation site on the south slope of the abandoned open-pit mine in Dadingzi was renovated into a trapezoidal shape, and then the iron tailings were spread and rolled in layers for 25m, and water was sprinkled during rolling to improve the compaction efficiency and effect, and then the iron tailings were spread for 25cm; the iron tailings compound fertilizer was transported to the implementation site and spread for 4cm, and then a mixing machine was used to mix the surface materials of the site to form a 20cm mixed soil layer, and white spear and bluegrass seeds were sown, and a small amount of crabgrass and goosegrass seeds were sown, and then 2cm-4cm of soil was covered;

[0125] Step 2: Evenly spread a thin layer of wheat straw shredded fibers and wood segments on the cultivated surface completed in Step 1. The wood segments are cut from trees and shrubs with a length of 1 cm - 3 cm, and the coverage rate reaches over 75%. Then lay a wire mesh with a pore size of 3 cm; roll it with a roller, and then fix the wire mesh to the underlying soil with wooden pegs. The length of the wooden pegs is 20 cm, and the depth of driving into the soil is 18 cm. Then plant 2 rows of 2-year-old Amorpha fruticosa seedlings with a height of 60 cm (spacing between plants is 50 cm) at a row spacing of 4 m, and then plant 1 row of 2-year-old Hippohae rhamnoides seedlings with a height of 30 cm (spacing between plants is 100 cm) in rows at a row spacing of 6 m. Then plant 2 rows of 2-year-old Amorpha fruticosa seedlings with a height of 60 cm (spacing between plants is 50 cm) and 1 row of 2-year-old Hippohae rhamnoides seedlings with a height of 30 cm (spacing between plants is 100 cm) at intervals of 6 m, 4 m, and 6 m. And so on to form a combination of 2 rows of Amorpha fruticosa and 1 row of Hippohae rhamnoides;

[0126] Step 3: Irrigate, maintain, and conduct field management to form an ecological protection layer with the combined action of the vegetation on the abandoned mine land, the mixed soil layer, the wire mesh, the straw fibers and wood segments, and the wooden pegs.

[0127] Observed in late September 2024, the vegetation coverage rate of the implementation site on the south slope of the abandoned open-pit mine of Dadingshan in Beitai Iron Mine reached 80%. The stems, roots of plants, straw fibers, wood segments, and the wire mesh were wound and cross-linked with the surface soil to form a carpet-like shape, and only a small number of shallow grooves appeared on the slope, achieving a good ecological restoration effect.

[0128] As mentioned above, it is only the best embodiment of the present invention and does not impose any formal restrictions on the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, may make many possible changes and modifications to the technical solution of the present invention by using the disclosed method content, and all of them fall within the protection scope of the present invention.

Claims

1. A preparation method of an iron tailing compound fertilizer, characterized in that, The following steps are involved: Step 1: Cut the branches of woody plants into woody segments, cut the crop straw into segments and shred them into stem bark fibers and debris, and fully mix the woody segments, the straw stem bark fibers and debris, and livestock and poultry manure to obtain a biomass base material; Step 2: Activate, propagate and dilute the EM bacterial agent into effective bacteria to obtain a microbial agent, spray the microbial agent into the biomass base material, stir evenly, spray 25°C-35°C water during the stirring process, keep the mixture in a moist state, and obtain a biomass mixture; Step 3: The biomass mixture is fermented, and temperature, humidity, overturning and ventilation operations are performed during the fermentation process, and biomass fertilizer is obtained after the fermentation is completed; Step 4: Evenly mix bentonite, fly ash, steel slag and iron tailings in sequence to obtain mineral fertilizer; Step 5: Evenly mix the biomass fertilizer and the mineral fertilizer to obtain the iron tailings compound fertilizer.

2. The preparation method of a kind of iron tailing compound fertilizer as described in claim 1, characterized in that, Step 1: The branches of woody plants are selected from branches of trees and / or shrubs, which are cut into woody segments with a length of 1 cm-3 cm; the crop straw includes the remaining parts of one or more of corn, sorghum, rice, wheat, reed, peanut, soybean, potato, rapeseed, cotton or sugarcane after harvest, which are cut into segments and kneaded into stem bark fibers and debris with a length of 1 cm-4 cm; The livestock and poultry manure is a mixture of cattle and / or sheep manure and chicken and / or pig manure, and the dry mass ratio of cattle and / or sheep manure to chicken and / or pig manure is 2:(1-4); The dry mass ratio of the three biomass materials, namely wood segments, straw bark fibers and debris, and livestock and poultry manure, is 2:(1-4):(1-4).

3. The preparation method of an iron tailing compound fertilizer according to claim 1, characterized in that, In Step 2, the number concentration of the effective bacteria is 1×10 7 CFU / mL - 9×10 7 CFU / mL, and the moisture content maintaining the wet state is 35% - 60%.

4. The preparation method of an iron tailing compound fertilizer according to claim 1, characterized in that, Step 3 Fermentation lasts 4-14 days.

5. The preparation method of an iron tailing compound fertilizer according to claim 1, wherein, Step 4: The dry mass ratio of bentonite, fly ash, steel slag and iron tailings is (10-20):(1-4):(1-4):(10-20). The bentonite and steel slag are processed into powder, and the mineral fertilizer is in a dry state or a wet state with a moisture content of less than 30%.

6. The preparation method of an iron tailing composite fertilizer according to claim 1, characterized in that, Step 5: The dry mass ratio of biomass fertilizer to mineral fertilizer is 2:(3-6), and watering is performed according to the dryness and wetness of the biomass fertilizer and the mineral fertilizer to keep the iron tailings compound fertilizer in a moist state with an overall moisture content of 20%-40%.

7. A composite fertilizer for iron tailings, characterized in that, The compound fertilizer is prepared using the method for preparing the iron tailings compound fertilizer described in claim 1.

8. An ecological restoration method for abandoned mine land, characterized in that, The following steps are involved: Step 1: transport the iron tailings compound fertilizer prepared in claim 1 to the abandoned iron mine site to be ecologically restored, spread the iron tailings compound fertilizer 3cm-5cm on the outer slope of the tailings dam or the dry beach of the tailings pond after closure, and then use a mixing machine to mix the site surface materials to form a 15cm-25cm mixed soil layer, then dig trenches and ridges, sow plants, and cover with soil; For spoil dumps or exposed open-pit mines, the original site is renovated into a trapezoid, and then the iron tailings are spread and rolled in layers of 10cm-25cm, and water is sprinkled while rolling. Then, the iron tailings are spread by 15cm-25cm, and then the iron tailings compound fertilizer is spread by 3cm-5cm. Then, a mixing machine is used to mix the site surface materials to form a 15cm-25cm mixed soil layer, and then trenches are opened, ridges are formed, plants are sown, and soil is covered; Step 2: Lay a wire mesh on the tillage surface of the mixed soil layer. The aperture of the wire mesh is 2 cm - 5 cm. Roll it with a roller, and then fix the wire mesh to the underlying soil with wooden pegs. The length of the wooden pegs is 15 cm - 25 cm, and the depth of the pegs driven into the soil is 10 cm - 20 cm. Then plant the plants. Step 3: Irrigate, maintain, and conduct field management to form an ecological protection layer with the combined action of the vegetation on the mine waste land - the mixed soil layer - the wire mesh - the wooden pegs.

9. The ecological restoration method for mine waste land according to claim 8, wherein, In Step 1, the sowing method is a combination of drilling and broadcasting. The sown plants are mainly Gramineae, supplemented by Leguminosae and Compositae.

10. The ecological restoration method for mine waste land as described in claim 8, wherein, In Step 2, straw fibers and / or wood segments and / or leaves are evenly spread on the tillage surface of the mixed soil layer before laying the wire mesh, with a coverage rate of over 60%. The planted plants are shrubs and / or small trees. After the irrigation, maintenance, and field management in Step 3, an ecological protection layer with the combined action of the vegetation on the mine waste land - the mixed soil layer - the wire mesh - the straw fibers and / or wood segments and / or leaves - the wooden pegs is formed.