A method for preparing a regenerated soil using phosphogypsum

Abstract

The application provides a method for preparing regenerated soil by using phosphogypsum, which takes bulk solid waste phosphogypsum as raw material, and through harmless treatment, microbial alternate fermentation and trace element compound treatment, a regenerated soil with high fertility, stable structure and strong water and fertilizer retention capacity is obtained, which can be directly used for crop planting. The method can promote the plant absorption of Ca, S, P and other elements in the phosphogypsum, and realize the land utilization of all components of the phosphogypsum. In addition, through the formation of organic-inorganic complex by the compounding fermentation technology, the complex can not only promote the formation of soil aggregate structure, but also improve the biological effectiveness of trace elements and the stability of organic matter in the soil, and then build a high-quality regenerated soil with strong water retention and air permeability and long-lasting fertilizer efficiency. The application can not only effectively solve the problem of phosphogypsum storage, but also apply the prepared regenerated soil to farmland improvement, land reclamation and crop planting, and realize the goal of turning waste into treasure.

Description

[0001] This invention is a divisional application. The original application was entitled "A Method for Preparing Regenerated Soil Using Phosphogypsum and Its Application", with application number 202510197155.7 and application date of February 21, 2025. Technical Field

[0002] This invention belongs to the field of solid waste resource utilization, and in particular relates to a method for preparing recycled soil using phosphogypsum and its application. Background Technology

[0003] Phosphogypsum is a byproduct of the wet process for producing phosphoric acid. For every ton of phosphoric acid produced, 4-5 tons of phosphogypsum are generated, making it one of my country's major industrial solid wastes. The main component of phosphogypsum is CaSO4·2H2O, along with acid-insoluble matter, small amounts of phosphoric acid, phosphates, fluorides, and unreacted phosphate rock. Currently, the primary method of phosphogypsum disposal in my country is stockpiling. This method not only requires a large land area, but also releases leachate containing phosphorus and phosphorus (P and F) into water bodies with rainfall, harming the ecosystems of rivers, lakes, and seas. Therefore, the comprehensive utilization of phosphogypsum waste is crucial for the sustainable development of the phosphorus chemical industry. Phosphogypsum contains essential nutrients for crop growth, such as phosphorus, sulfur, calcium, silicon, magnesium, and iron. Converting it into soil for reuse can achieve large-scale utilization of phosphogypsum resources. However, phosphogypsum typically contains harmful impurities such as heavy metals, free fluorine, and organic matter, making it unsuitable for direct land application. In addition, the calcium sulfate dihydrate in phosphogypsum has low solubility in water, and phosphorus mainly exists in the form of insoluble phosphorus such as phosphate precipitate, undecomposed phosphate rock powder and eutectic phosphorus, making it difficult for plants to absorb and utilize elements such as Ca, S and P.

[0004] Therefore, there is an urgent need for a new method that is harmless and can achieve efficient utilization of all components of phosphogypsum in order to promote the large-scale application of phosphogypsum in the soil field. Summary of the Invention

[0005] To address the problems in the background art, this invention provides a method for preparing regenerated soil using phosphogypsum and its application. This method can effectively remove toxic and harmful elements from phosphogypsum and fully release the abundant Ca, S, P and other nutrients required by plants, thereby achieving the efficient and safe application of phosphogypsum in the soil field.

[0006] Another objective of this invention is to provide a regenerated soil with high fertility, stable structure, and strong water and fertilizer retention capacity. This regenerated soil is rich in various nutrients required for plant growth, while also possessing good water retention and aeration properties, which can effectively improve soil structure and promote plant growth.

[0007] Another object of the present invention is to provide an application of a method for preparing recycled soil using phosphogypsum.

[0008] The present invention adopts the following technical solution:

[0009] A method for preparing recycled soil using phosphogypsum includes the following steps:

[0010] Step S1. Thoroughly mix phosphogypsum and an organic acid solution with a molar concentration of 0.1-1 mol / L, react for 1-24 h, wash with water and dry to obtain modified phosphogypsum.

[0011] Step S2. The modified phosphogypsum, clay minerals, microbial agents, and organic matter from step S1 are mixed evenly in a certain proportion using a stepwise mixing method. The mixture is then transferred to a fermentation device. By changing the atmosphere in the fermentation device, aerobic-anaerobic alternating microbial fermentation is carried out to obtain fermented phosphogypsum rich in organic matter.

[0012] Step S3. Add trace element compounding agent to the fermented phosphogypsum from step S2, mix evenly, and obtain regenerated soil.

[0013] Furthermore, the organic acid in step S1 is an organic acid with a strong ability to complex heavy metals, preferably one or more of the following: oxalic acid, ethylenediaminetetraacetic acid, citric acid, formic acid, acetic acid, propionic acid, lactic acid, succinic acid, malonic acid, maleic acid, tartaric acid, succinic acid, malic acid, benzoic acid, phenylacetic acid, phthalic acid, terephthalic acid, valeric acid, hexanoic acid, decanoic acid, stearic acid, and acrylic acid.

[0014] Furthermore, the goal of the reaction between phosphogypsum and organic acid in step S1 is to make the element content in phosphogypsum meet the national standard "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB15618-2018).

[0015] Furthermore, the clay mineral in step S2 is one or more of montmorillonite, kaolinite, halloysite, palygorskite, sepiolite, illite, talc, sericite, and vermiculite.

[0016] Furthermore, the microbial agent in step S2 is a mixture of yeast, actinomycete, lactic acid bacteria, sulfate-reducing bacteria, phosphate-solubilizing bacteria, nitrogen-fixing bacteria, and potassium-solubilizing bacteria.

[0017] Furthermore, the organic matter in step S2 is one or more of the following: livestock and poultry manure, livestock and poultry carcasses, kitchen waste, biogas residue, mushroom residue, urban sludge, and crop straw. The element content of these substances all comply with the national standard "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB15618-2018).

[0018] Furthermore, in step S2, the stepwise mixing method involves first mixing organic matter, clay minerals, and microbial agents in a mass ratio of 1:0.01-0.2:0.01-0.1 to obtain a primary mixture, and then uniformly mixing modified phosphogypsum and the primary mixture in a mass ratio of 1:0.1-0.6, controlling the moisture content of the mixture to be 60%.

[0019] Furthermore, in step S2, the aerobic-anaerobic alternating microbial fermentation involves the mixture undergoing aerobic fermentation followed by anaerobic fermentation, and this alternation is repeated several times.

[0020] The aerobic fermentation is a microbial fermentation carried out in an air atmosphere, with the gaseous oxygen content in the fermentation device controlled at 5-21% and the fermentation time being 4-20 days.

[0021] The anaerobic fermentation involves introducing a nitrogen atmosphere into the fermentation bottle, controlling the gaseous oxygen content in the fermentation device to be below 5% (Vol%), and the fermentation time to be 3-15 days.

[0022] The aerobic-anaerobic alternating fermentation is carried out 1-10 times.

[0023] Furthermore, the trace element compound in step S3 is a natural mineral conditioning material or an inorganic reagent.

[0024] Furthermore, the natural mineral conditioning material is one or more of feldspar, mica, amphibole, pyroxene, peridot, garnet, dolomite, diaspore, and iron oxide.

[0025] Furthermore, the inorganic reagent is one or more of ammonium sulfate, zinc sulfate, magnesium sulfate, borax, and calcium nitrate.

[0026] Furthermore, in step S3, the amount of trace element compound agent added accounts for less than 10% of the total mass.

[0027] A type of recycled soil prepared using phosphogypsum is prepared by the above-described method.

[0028] Furthermore, the recycled soil can be used in crop cultivation.

[0029] The beneficial effects of this invention are:

[0030] (1) This invention uses bulk solid waste phosphogypsum as raw material, and removes harmful substances such as heavy metals and free fluorine through acid washing via organic acid adsorption and complexation, achieving harmless treatment. Then, through alternating aerobic-anaerobic microbial fermentation and micronutrient compounding, regenerated soil with high fertility, stable structure, and strong water and fertilizer retention capacity is obtained. This method not only effectively solves the problem of phosphogypsum stockpiling, but also allows the resulting regenerated soil to be applied to farmland improvement, soil reclamation, and crop planting, achieving the goal of turning waste into treasure.

[0031] (2) The clay-organic matter-phosphogypsum mixture is fermented using an alternating aerobic-anaerobic microbial fermentation method. This method can effectively promote the release of Ca, S and P elements in phosphogypsum and improve soil fertility. In addition, the organic-inorganic co-fermentation helps to form an organic-inorganic complex. This complex can not only promote the formation of soil aggregates and improve soil structure, but also improve the stability of organic matter in the soil, thereby constructing a high-quality regenerated soil with strong water retention and aeration, high fertility and long-lasting fertilizer effect. At the same time, the high temperature environment generated during the fermentation process can effectively kill pathogens and parasite eggs, thereby avoiding pests and ensuring the biological safety of the regenerated soil.

[0032] (3) The prepared recycled soil can be used for crop planting without the need for compounding other fertilizers and can be used directly for crop planting. Attached Figure Description

[0033] Figure 1 Photograph of the regenerated soil from the product prepared in Example 1 of this invention;

[0034] Figure 2 This is a schematic diagram of the method for preparing regenerated soil based on phosphogypsum according to the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0036] The preparation methods of Examples 1-6 can all be referred to Figure 2 .

[0037] Example 1

[0038] A method for preparing recycled soil using phosphogypsum includes the following steps:

[0039] 1) Take 5 kg of phosphogypsum and 10 L of 0.1 mol / L oxalic acid solution, mix them thoroughly and react for 12 h. Wash with ultrapure water and dry to obtain modified phosphogypsum.

[0040] 2) Mix 9 kg of straw powder, 1 kg of cow dung, 100 g of kaolin, and 100 g of microbial inoculant evenly to obtain a primary mixture. Then, mix 5 kg of modified phosphogypsum with 1 kg of the primary mixture, ensuring the moisture content of this mixture is around 60%. Transfer this mixture to an anaerobic fermentation bottle, maintaining the gaseous oxygen content at 20% (Vol%), and ferment for 10 days. Afterward, introduce nitrogen gas into the anaerobic bottle, maintaining the gaseous oxygen content below 5% (Vol%), and ferment for 4 days to obtain fermented phosphogypsum rich in organic matter. Repeat this alternating fermentation process once.

[0041] 3) Add 1% by weight (by weight of total weight) of magnesium sulfate and zinc sulfate composite conditioning material to the fermented phosphogypsum system, mix evenly, and obtain regenerated soil.

[0042] The prepared recycled soil is brown and has a relatively loose texture (e.g., Figure 1 (As shown). The soil bulk density is 1.3 g / cm³, pH value is 6.5, electrical conductivity is 2.37 mS / cm, organic matter content is 30 g / kg, available phosphorus content is 565 mg / kg, available potassium content is 2620 mg / kg, available nitrogen content is 303 mg / kg, available calcium content is 378 mg / kg, available magnesium content is 35 mg / kg, and available sulfur content is 15 mg / kg. According to the nutrient classification standards of the Second National Soil Survey, the nutrients in this regenerated soil belong to Class I. In addition, the contents of heavy metals such as Hg, Cd, As, Pb, Cr, Cu, and Ni in the soil are all lower than the screening values ​​of the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB15618-2018), which meets the agricultural land standards.

[0043] Example 2

[0044] A method for preparing recycled soil using phosphogypsum includes the following steps:

[0045] 1) Take 5 kg of phosphogypsum and 10 L of 0.2 mol / L malic acid solution, mix them thoroughly and react for 24 h. Wash with ultrapure water and dry to obtain modified phosphogypsum.

[0046] 2) Mix 9 kg of straw powder, 1 kg of cow dung, 100 g of kaolin, and 100 g of microbial inoculant evenly to obtain a primary mixture. Then, mix 5 kg of modified phosphogypsum with 500 g of the primary mixture evenly, maintaining the moisture content of the mixture at approximately 60%. Transfer this mixture to an anaerobic fermentation bottle, maintaining the gaseous oxygen content at 20% (vol%) for 8 days. Afterward, introduce nitrogen gas into the anaerobic bottle, maintaining the gaseous oxygen content below 5% (vol%), and ferment for 4 days to obtain fermented phosphogypsum rich in organic matter. Repeat this alternating fermentation process once.

[0047] 3) Add 1% by weight of magnesium sulfate and zinc sulfate composite conditioning material to the fermented phosphogypsum, mix evenly, and obtain regenerated soil.

[0048] The regenerated soil has a bulk density of 1.25 g / cm³, a pH of 6, an electrical conductivity of 2.1 mS / cm, an organic matter content of 25 g / kg, an available phosphorus content of 620 mg / kg, an available potassium content of 2750 mg / kg, an alkaline available nitrogen content of 280 mg / kg, an available calcium content of 375 mg / kg, an available magnesium content of 33 mg / kg, and an available sulfur content of 14 mg / kg. According to the nutrient classification standards of the Second National Soil Survey, the nutrients in this regenerated soil belong to Grade I. Furthermore, the contents of heavy metals such as Hg, Cd, As, Pb, Cr, Cu, and Ni in the regenerated soil are all lower than the screening values ​​of the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB15618-2018), meeting the agricultural use standards.

[0049] Example 3

[0050] A method for preparing recycled soil using phosphogypsum includes the following steps:

[0051] 1) Take 5 kg of phosphogypsum and 5 L of 0.1 mol / L tartaric acid solution, mix them thoroughly and react for 6 h. Wash with ultrapure water and dry to obtain modified phosphogypsum.

[0052] 2) Mix 9 kg of straw powder, 500 g of pig manure, 100 g of vermiculite, and 100 g of microbial inoculant evenly to obtain a primary mixture. Then, mix 5 kg of modified phosphogypsum with 1500 g of the primary mixture evenly, ensuring the moisture content of the mixture is around 60%. Transfer the mixture to an anaerobic fermentation bottle, maintaining the gaseous oxygen content at 20% (Vol%) for 4 days. Afterward, introduce nitrogen gas into the anaerobic bottle, maintaining the gaseous oxygen content below 5% (Vol%) for 3 days. Repeat this alternating fermentation process once more to obtain fermented phosphogypsum rich in organic matter.

[0053] 3) Add 1% by weight of magnesium sulfate and zinc sulfate composite conditioning material to the fermented phosphogypsum, mix evenly, and obtain regenerated soil.

[0054] The regenerated soil has a bulk density of 1.15 g / cm³, a pH of 6.8, an electrical conductivity of 2.42 mS / cm, an organic matter content of 51 g / kg, an available phosphorus content of 400 mg / kg, an available potassium content of 2150 mg / kg, an alkaline available nitrogen content of 310 mg / kg, an available calcium content of 357 mg / kg, an available magnesium content of 32 mg / kg, and an available sulfur content of 12 mg / kg. According to the nutrient classification standards of the Second National Soil Survey, the nutrients in this regenerated soil belong to Grade I. Furthermore, the contents of heavy metals such as Hg, Cd, As, Pb, Cr, Cu, and Ni in the regenerated soil are all lower than the screening values ​​of the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB15618-2018), meeting the agricultural use standards.

[0055] Example 4

[0056] A method for preparing recycled soil using phosphogypsum includes the following steps:

[0057] 1) Take 5 kg of phosphogypsum and 10 L of 1 mol / L oxalic acid solution, mix them thoroughly, react for 12 h, wash with ultrapure water and dry to obtain modified phosphogypsum.

[0058] 2) Mix 9 kg of straw powder, 200 g of bentonite, and 150 g of microbial inoculant evenly to obtain a primary mixture. Then, mix 5 kg of modified phosphogypsum with 1 kg of the primary mixture, ensuring the moisture content of this mixture is around 60%. Transfer this mixture to an anaerobic fermentation bottle, maintaining the gaseous oxygen content at 20% (Vol%), and ferment for 10 days. Afterward, introduce nitrogen gas into the anaerobic bottle, maintaining the gaseous oxygen content below 5% (Vol%), and ferment for another 4 days to obtain fermented phosphogypsum rich in organic matter. Fermentation is performed only once.

[0059] 3) Add 1% by weight of magnesium sulfate and zinc sulfate composite conditioning material to the fermented phosphogypsum, mix evenly, and obtain regenerated soil.

[0060] The regenerated soil has a bulk density of 1.26 g / cm³, a pH of 6.3, an electrical conductivity of 2.28 mS / cm, an organic matter content of 45 g / kg, an available phosphorus content of 560 mg / kg, an available potassium content of 2650 mg / kg, an alkaline available nitrogen content of 260 mg / kg, an available calcium content of 378 mg / kg, an available magnesium content of 30 mg / kg, and an available sulfur content of 15 mg / kg. According to the nutrient classification standards of the Second National Soil Survey, the nutrients in this regenerated soil belong to Grade I. Furthermore, the contents of heavy metals such as Hg, Cd, As, Pb, Cr, Cu, and Ni in the regenerated soil are all lower than the screening values ​​of the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB15618-2018), meeting the standards for agricultural land.

[0061] Example 5

[0062] A method for preparing recycled soil using phosphogypsum includes the following steps:

[0063] 1) Take 5 kg of phosphogypsum and 10 L of 0.2 mol / L tartaric acid solution, mix them thoroughly, react for 12 h, wash with ultrapure water and dry to obtain modified phosphogypsum.

[0064] 2) Mix 9 kg of straw powder, 1 kg of cow dung, 200 g of bentonite, and 150 g of compound microbial agent evenly to obtain a primary mixture. Then, mix 5 kg of modified phosphogypsum with 1 kg of the primary mixture evenly, controlling the moisture content of the mixture to approximately 60%. Transfer this mixture to an anaerobic fermentation bottle, maintaining the gaseous oxygen content at 20% (vol%), and ferment for 15 days. Afterward, introduce nitrogen gas into the anaerobic bottle, maintaining the gaseous oxygen content below 5% (vol%), and ferment for another 8 days to obtain fermented phosphogypsum rich in organic matter. Repeat this alternating fermentation process once.

[0065] 3) Add 0.5% by weight of magnesium sulfate and zinc sulfate composite conditioning material to the fermented phosphogypsum, mix evenly, and obtain regenerated soil.

[0066] The regenerated soil has a bulk density of 1.24 g / cm³, a pH of 6.8, an electrical conductivity of 2.42 mS / cm, an organic matter content of 47 g / kg, an available phosphorus content of 572 mg / kg, an available potassium content of 2750 mg / kg, an alkaline available nitrogen content of 310 mg / kg, an available calcium content of 368 mg / kg, an available magnesium content of 29 mg / kg, and an available sulfur content of 13 mg / kg. According to the nutrient classification standards of the Second National Soil Survey, the nutrients in this regenerated soil belong to Grade I. Furthermore, the contents of heavy metals such as Hg, Cd, As, Pb, Cr, Cu, and Ni in the regenerated soil are all lower than the screening values ​​of the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial) (GB15618-2018)," meeting the standards for agricultural land.

[0067] Example 6

[0068] A method for preparing recycled soil using phosphogypsum includes the following steps:

[0069] 1) Take 5 kg of phosphogypsum and 10 L of 0.1 mol / L tartaric acid solution, mix them thoroughly, sonicate them in a microwave for 20 min, wash them with ultrapure water and dry them to obtain modified phosphogypsum.

[0070] 2) Mix 9 kg of straw powder, 1 kg of cow dung, 500 g of attapulgite, and 150 g of compound microbial agent evenly to obtain a primary mixture. Then, mix 5 kg of modified phosphogypsum with 1 kg of the primary mixture evenly, controlling the moisture content of the mixture to around 60%. Transfer the mixture to an anaerobic fermentation bottle, controlling the gaseous nitrogen content in the fermentation bottle to 20% (vol%), and ferment for 6 days. Then, introduce nitrogen gas into the anaerobic bottle, controlling the gaseous oxygen content in the fermentation bottle to below 5% (vol%), and ferment for 3 days. Repeat this alternating fermentation process once more to obtain fermented phosphogypsum rich in organic matter.

[0071] 3) Add 1% by mass of olivine mineral conditioning material to the fermented phosphogypsum to obtain regenerated soil.

[0072] The regenerated soil has a bulk density of 1.29 g / cm³, a pH of 6.5, an electrical conductivity of 2.36 mS / cm, an organic matter content of 42 g / kg, an available phosphorus content of 550 mg / kg, an available potassium content of 2632 mg / kg, an alkaline available nitrogen content of 295 mg / kg, an available calcium content of 370 mg / kg, an available magnesium content of 25 mg / kg, and an available sulfur content of 15 mg / kg. According to the nutrient classification standards of the Second National Soil Survey, the regenerated soil belongs to Grade I. Furthermore, the contents of heavy metals such as Hg, Cd, As, Pb, Cr, Cu, and Ni in the regenerated soil are all lower than the screening values ​​of the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB15618-2018), meeting the standards for agricultural land.

[0073] Comparative Example 1

[0074] This comparative example uses phosphogypsum as soil, applied directly to crop cultivation without organic acid treatment or alternating aerobic-anaerobic fermentation. The sample has a pH of 3.3, an electrical conductivity of 4.656 Ms / cm, an organic matter content of 1.69 g / kg, available phosphorus of 1779 g / kg, available calcium of 130 mg / kg, available magnesium of 8 mg / kg, and available sulfur of 7 mg / kg. According to the nutrient grading standards of the Second National Soil Survey, the organic matter quality of this soil belongs to Grade IV (lower-middle) quality.

[0075] Application Examples

[0076] The regenerated soils prepared in Examples 1, 2, and Comparative Example 1 were placed in flowerpots with an upper diameter of 25 cm and a height of 20 cm, and *Rhizophora stylosa* was planted. During the planting process, the soil was watered every 3 days to replenish the soil moisture to 80% of the field drainage capacity. The plant height, diameter, tillering, and other parameters of *Rhizophora stylosa* were recorded during the planting period. The experimental results are as follows:

[0077] Comparative table of traits of *King Grass* grown in regenerated soil under different conditions

[0078]

[0079] The data in the table show that the regenerated soil obtained from phosphogypsum after organic acid treatment and alternating aerobic-anaerobic fermentation is more conducive to the growth of *King Grass*.

[0080] In summary, this invention provides a method and application for preparing recycled soil using phosphogypsum, belonging to the field of solid waste resource utilization. The method involves: modifying phosphogypsum with an organic acid solution to remove impurities and meet land use requirements. Next, the modified phosphogypsum undergoes alternating aerobic and anaerobic fermentation by microorganisms to promote its dissolution and humus formation, thereby enhancing the bioavailability and long-lasting effectiveness of nutrients in the phosphogypsum-based recycled soil. Finally, the fermented phosphogypsum is mixed with trace element additives to form plantable soil.

[0081] This invention uses bulk solid waste phosphogypsum as raw material, making full use of elements such as Ca, S, and P in the phosphogypsum. Through harmless treatment (organic acid washing), alternating aerobic-anaerobic microbial fermentation, and compounding with trace element additives, a regenerated soil with high fertility, stable structure, and strong water and fertilizer retention capacity is obtained. This method not only effectively solves the problem of phosphogypsum storage, but also enables the regenerated soil to be applied to farmland improvement, land reclamation, and crop planting, achieving the goal of turning waste into treasure.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of recycled soil for crop cultivation, characterized in that, Made from phosphogypsum.

2. The method for preparing recycled soil as described in claim 1, characterized in that, Includes the following steps: Step S1: Thoroughly mix phosphogypsum and an organic acid solution with a molar concentration of 0.1-1 mol / L, react for 1-24 h, wash with water and dry to obtain modified phosphogypsum; Step S2: The modified phosphogypsum, clay minerals, microbial agents and organic matter from step S1 are mixed evenly in a certain proportion by a stepwise mixing method, and then transferred into a fermentation device. By changing the atmosphere in the fermentation device, aerobic-anaerobic alternating microbial fermentation is carried out to obtain fermented phosphogypsum rich in organic matter. Step S3: Add a trace element compound agent to the fermented phosphogypsum in step S2, mix evenly, and obtain regenerated soil; The organic acid solution in step S1 is one or more of the following: oxalic acid, ethylenediaminetetraacetic acid, citric acid, formic acid, acetic acid, propionic acid, lactic acid, succinic acid, malonic acid, maleic acid, tartaric acid, succinic acid, malic acid, benzoic acid, phenylacetic acid, phthalic acid, terephthalic acid, valeric acid, hexanoic acid, decanoic acid, stearic acid, and acrylic acid. The clay mineral in step S2 is one or more of montmorillonite, kaolinite, halloysite, palygorskite, sepiolite, illite, talc, sericite, and vermiculite; the microbial agent is a mixture of yeast agent, antifungal agent, lactic acid bacteria agent, sulfate-reducing bacteria agent, phosphate-solubilizing bacteria, nitrogen-fixing bacteria, and potassium-solubilizing bacteria; the organic matter is one or more of livestock and poultry manure, livestock and poultry carcasses, kitchen waste, biogas residue, mushroom residue, urban sludge, and crop straw. In step S3, the trace element compound agent is a natural mineral conditioning material or an inorganic reagent, and the amount of the trace element compound agent added accounts for less than 10% of the total mass. The natural mineral conditioning material is one or more of feldspar, mica, amphibole, pyroxene, olivine, garnet, dolomite, diaspore, and iron oxide; the inorganic reagent is one or more of ammonium sulfate, zinc sulfate, magnesium sulfate, borax, and calcium nitrate.

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