A method for preparing soil conditioner by treating phosphogypsum with lime nitrogen residue and soil conditioner

Abstract

The present application relates to phosphogypsum resource utilization technical field, especially to a kind of method for preparing soil conditioner by using lime nitrogen slag to treat phosphogypsum and soil conditioner, using lime nitrogen slag, phosphogypsum natural air-drying to moisture content≤25%, respectively, powder is prepared after being crushed, sieved, and lime nitrogen slag powder and phosphogypsum powder are mixed uniformly with proper mass ratio, make full use of the nutrient components in lime nitrogen slag and phosphogypsum, so that adding to soil supplement nutrients, guarantee the nutrient combination in conditioner is reasonable, realize the improvement and conditioning effect to soil;Activated slag is added to be mixed uniformly, modified treatment, aging treatment after adjusting pH value, granulation, to make free acid radical (phosphate radical, sulfuric radical, etc.) in phosphogypsum be solidified, and heavy metal content in the obtained soil conditioner is very low, meet the requirements of "phosphogypsum soil conditioner" (HG / T 4219).

Description

Technical Field

[0001] This invention relates to the field of phosphogypsum resource utilization technology, and in particular to a method for preparing soil conditioners by treating phosphogypsum with lime cyanide slag, and the soil conditioner itself. Background Technology

[0002] Phosphogypsum is an acidic solid waste produced by the wet-process phosphoric acid production method. Its main component is calcium sulfate dihydrate, and it also contains arsenic, cadmium, lead, chromium, mercury, thallium, and sulfur. - The presence of harmful elements such as phosphorus gypsum during storage or resource utilization can easily lead to secondary pollution, hindering the development of the phosphorus chemical industry. Therefore, how to utilize phosphorus gypsum as a resource has become a pressing technical challenge for the development of the phosphorus chemical industry, attracting extensive research and resulting in numerous technical solutions for preparing fertilizers, soil conditioners, and soil amendments using phosphorus gypsum as a raw material. For example, patent number 202110434000.2 discloses a phosphorus gypsum soil amendment and its preparation method. This amendment uses phosphorus gypsum treated with active microorganisms as a carrier, adding modified activated carbon and adsorbents to fully utilize the plant nutrients such as phosphorus, calcium, sulfur, and silicon contained in phosphorus gypsum, improving soil remediation capacity and enhancing the treatment effect on heavy metals.

[0003] For example, patent number 202111294235.2 discloses a method for preparing a soil conditioner for passivating heavy metals in soil using phosphogypsum as a raw material. The method involves grinding and filtering phosphogypsum with water to prepare a filtrate, then adding a crystallizing agent and a modifier, stirring and mixing, allowing it to stand and filter, returning the waste liquid to grind phosphogypsum, and drying the solid to a constant weight to prepare a soil conditioner, thereby achieving the purpose of passivating heavy metals in the soil and reducing the risk of heavy metal re-migration.

[0004] For example, patent number 202111294239.0 discloses a method for preparing a soil conditioner for saline-alkali land by fermenting and adjusting the moisture content of phosphogypsum. The method involves grinding phosphogypsum to adjust its moisture content, thereby exposing nutrients such as fluorine and phosphorus. Dry chicken manure is added to absorb the moisture content of the ground phosphogypsum, thus meeting the requirements for fermentation. The mixture is then bagged, sealed, and fermented. When added to the soil, it can reduce the soil salinity, lower the pH, and promote the normal growth of crops.

[0005] Calcium cyanide slag is a black solid waste produced during the production of fungicides such as carbendazim and thiourea. It is alkaline, has a slightly pungent odor, and its main components are calcium hydroxide and calcium carbonate. It also contains elements such as silicon, aluminum, iron, and magnesium. In addition, calcium cyanide slag contains nitrogen-containing substances such as cyanamide and dicyandiamide, resulting in a high total nitrogen content. Currently, calcium cyanide slag is not seen in the field of soil conditioners, but calcium cyanide has been widely used in the preparation of soil conditioners. For example, patent number 201510564109.2 discloses a multifunctional granular soil conditioner with calcium cyanide and its preparation method. It is prepared by mixing calcium cyanide, auxiliary materials, lignite, potassium humate, zeolite powder, hot melt binder, urea, polyphosphoric acid, and solid paraffin. The hot melt binder is used as a water-retaining agent and chelating agent, and the auxiliary materials are used as neutralizing agents, activators, and synergists. Continuous granulation results in a low moisture content in the product, solving the problem of ammonia volatilization in calcium cyanide.

[0006] For example, patent application number 201610651250.0 discloses a composite acidic tobacco field soil conditioner and its application method. It is prepared by crushing, sieving, and mixing tobacco stalk black charcoal, calcium magnesium phosphate, magnesium hydroxide, potassium feldspar, and calcium cyanamide. It uses calcium cyanamide and other substances to adjust soil acidity, alleviate soil aluminum toxicity, and provide nutrients such as nitrogen and phosphorus.

[0007] For example, patent number 201510501481.9 discloses a multifunctional acidic soil conditioner and its application method. It is prepared by mixing magnesium hydroxide, calcium carbonate, calcium hydroxide, calcium magnesium phosphate fertilizer, calcium cyanamide, lignite, weathered coal, peat, borax and zinc sulfate to solve problems such as severe soil acidification, structural degradation and frequent soil-borne diseases, promote crop growth and improve crop yield and quality.

[0008] It is evident that both phosphogypsum and calcium cyanamide have been applied in the preparation of soil conditioners and soil amendments, resulting in a large body of technical literature. However, there are no reports on the combined application of calcium cyanamide slag and phosphogypsum in the preparation of soil conditioners, especially no research on the preparation of soil conditioners by mixing phosphogypsum with calcium cyanamide slag. Summary of the Invention

[0009] Based on the above-mentioned technical problems, our research team mixed calcium cyanamide slag and phosphogypsum in an appropriate ratio. After the calcium cyanamide slag and phosphogypsum materials were mixed and treated, they were prepared into a soil conditioner. This fully utilized the beneficial nutrients for crop growth such as phosphorus, sulfur, calcium and silicon contained in phosphogypsum, while reducing the content of arsenic, cadmium, lead, chromium and mercury in the soil conditioner.

[0010] The specific technical solution is as follows:

[0011] A method for preparing soil conditioners using calcium cyanamide slag to treat phosphogypsum includes the following steps:

[0012] (1) The phosphogypsum and calcium cyanamide slag are air-dried naturally until the moisture content is ≤25%, and then crushed and sieved to obtain phosphogypsum powder and calcium cyanamide slag powder; the crushing and sieving is through an 80-100 mesh sieve;

[0013] (2) Mix phosphogypsum powder and calcium cyanamide slag powder evenly at a mass ratio of 10:0.1-2 to obtain a mixture;

[0014] (3) The mixture is modified by adding 1-20% activated slag to phosphogypsum, adjusting the pH value to 5-6.5, aging for at least 24 hours, and then granulating.

[0015] After naturally air-drying calcium cyanamide slag and phosphogypsum to a moisture content of ≤25%, they are pulverized and sieved into powder. The calcium cyanamide slag powder and phosphogypsum powder are then mixed in an appropriate mass ratio to fully utilize the nutrients in the calcium cyanamide slag and phosphogypsum. This ensures that the soil is supplemented with nutrients and that the nutrient composition in the conditioner is reasonable, thereby achieving the effect of soil improvement and conditioning. Activated slag is added, mixed, and modified. After pH adjustment and aging, the mixture is granulated to solidify the free acid radicals (phosphate, sulfate, etc.) in the phosphogypsum. The resulting soil conditioner has extremely low heavy metal content, meeting the requirements of "Phosphogypsum Soil Conditioner" (HG / T4219).

[0016] In order to improve the activation and modification effect of activated slag on the mixture, enhance the solidification effect on free acid radicals, and improve the synergistic effect of mixing lime nitrogen slag and phosphogypsum, preferably, the activated slag is obtained by crushing and sieving phosphorus tailings, then roasting at 850-950℃ for 30 minutes and cooling to room temperature under natural conditions to obtain phosphorus tailings powder; or the activated slag is obtained by crushing and sieving phosphorus tailings, then acidifying them with industrial waste acid, and then air-drying them to a moisture content of ≤25%.

[0017] More preferably, the moisture content of the phosphorus tailings powder is ≤10%.

[0018] More preferably, the moisture content of the phosphorus tailings powder is 0.67%.

[0019] To achieve waste acid recycling and utilization, reduce the difficulty and cost of treating residual acid from phosphoric acid purification processes or waste acid from sulfuric acid production processes, and turn waste into treasure, preferably, the pH adjustment is performed using industrial waste acid. More preferably, the industrial waste acid is residual acid produced during phosphoric acid purification; or the industrial waste acid is waste acid produced during sulfuric acid production.

[0020] To ensure the effective mixing of lime cyanide slag and phosphogypsum after the addition of activated slag, and to enhance the conditioning properties of the conditioner, the aging treatment time is preferably 24-72 hours. More preferably, the aging treatment time is 48 hours.

[0021] The second objective of this invention is to provide a soil conditioner prepared by the above method.

[0022] Compared with the prior art, the technical effects of this invention are reflected in:

[0023] This invention uses a mixture of lime cyanide slag and phosphogypsum in an appropriate ratio, and then incorporates activated slag to modify the mixture. After adjusting the pH value and aging, the mixture promotes the synergistic effect of lime cyanide slag and phosphogypsum, improves the soil conditioning effect, and helps promote crop growth and increase yield.

[0024] The soil conditioner created by this invention has a low heavy metal content and can solidify free acid radicals (phosphate, sulfate, fluorine) in phosphogypsum. - This process improves soil conditioning effects. Simultaneously, it transforms waste materials such as phosphogypsum, calcium cyanamide slag, phosphate tailings, and industrial waste acid into valuable resources, fully utilizing elements like phosphorus, nitrogen, calcium, sulfur, silicon, iron, and magnesium in these materials to ensure effective soil conditioning and balance soil pH. Furthermore, it replenishes the soil with micronutrients, ensuring a balanced nutrient composition.

[0025] This invention enables the large-scale utilization of phosphogypsum, increases phosphogypsum disposal, reduces phosphogypsum stockpiling, and alleviates the environmental pressure caused by phosphogypsum landfill and stockpiling.

[0026] The process of this invention is simple and easy to industrialize and promote. Attached Figure Description

[0027] In order to enable those skilled in the art to fully understand the technical solution of the present invention, the present invention is now described in conjunction with the technical solution content and the accompanying drawings.

[0028] Figure 1 A process flow diagram is provided for this invention.

[0029] Figure 2 A process flow diagram for another embodiment of the present invention is provided.

[0030] Figure 3 Photos showing the growth of strawberries in a potted strawberry experiment.

[0031] Figure 4 A photograph of the growth of mint plants in a potted mint experiment.

[0032] Figure 5 The purpose is to provide a test report for the sample prepared in Example 8 to a third-party testing agency. Detailed Implementation

[0033] To facilitate a correct understanding of the present invention by those skilled in the art, and to enable them to fully understand the technical content of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. However, this description does not limit the scope of protection claimed by the present invention. Those skilled in the art should not limit the scope of protection of the present invention to the following description. Any equivalent substitutions or changes made by those skilled in the art or those familiar with the art based on the present invention, and based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0034] like Figure 1 As shown, in some embodiments, the method for preparing soil conditioners by treating phosphogypsum with calcium cyanamide slag includes the following steps:

[0035] (1) The phosphogypsum and calcium cyanamide slag are air-dried naturally until the moisture content is ≤25%, and then crushed and passed through an 80-100 mesh sieve, such as 80 mesh, 90 mesh, 100 mesh, etc., to obtain phosphogypsum powder and calcium cyanamide slag powder.

[0036] (2) Mix phosphogypsum powder and calcium cyanamide slag powder in a mass ratio of 10:0.1-2, for example: 10:0.1, 10:0.5, 10:0.8, 10:1, 10:1.2, 10:1.5, 10:1.7, 5:2, etc., to obtain a mixture;

[0037] (3) The mixture is modified by adding 1-20% (e.g., 1%, 5%, 7%, 14%, 17%, 20%) of activated slag, adjusting the pH value to between 5 and 6.5, and aging for at least 24 hours (e.g., 24h, 36h, 48h, 60h, 72h). The mixture is then granulated into 1-4mm particles (e.g., 1mm, 2mm, 3mm, 4mm). The activated slag is obtained by crushing phosphate tailings through an 80-100 mesh sieve (e.g., 80 mesh, 90 mesh, 100 mesh), calcining at 850-950℃ (e.g., 850℃, 900℃, 950℃) for 30 minutes, and then cooling to room temperature under natural conditions to obtain phosphate tailings powder.

[0038] By controlling the appropriate ratio of calcium cyanamide slag and phosphogypsum, and combining it with activated slag prepared from activated phosphate tailings, the mixture is added and mixed to modify the soil. This enhances the synergistic effect of the calcium cyanamide slag and phosphogypsum mixture, reduces the heavy metal content, solidifies the free acid radicals in the phosphogypsum, improves the soil conditioning effect, and helps promote crop growth and increase yield.

[0039] like Figure 2As shown, in some embodiments, the activated slag is obtained by crushing phosphorus tailings through an 80-100 mesh sieve (e.g., 80, 90, 100 mesh), then acidifying it with industrial waste acid, and finally air-drying it to a moisture content ≤25% (e.g., 6%, 7.3%, 8%, 10%, 13%, 15%, 20%, 23%, 25%) to obtain phosphorus tailings powder. Activating the phosphorus tailings through acidification allows the tailings, previously discarded as solid waste, to be activated and added to a mixture of calcium cyanamide slag and phosphogypsum. This enhances the synergistic effect of the calcium cyanamide slag and phosphogypsum in conditioning the soil, and also achieves the recycling of industrial waste acid, turning waste into treasure and reducing the cost of phosphorus tailings treatment.

[0040] In some embodiments, the pH adjustment is performed using industrial waste acid. The industrial waste acid is residual acid produced during the purification of phosphoric acid production; or it is waste acid produced during sulfuric acid production. This achieves the recycling and utilization of industrial waste acid.

[0041] In some embodiments of this invention, the industrial waste acid acidification treatment involves directly adding industrial waste acid to the crushed and sieved phosphate tailings, ensuring that the mass ratio of industrial waste acid added is controlled to prevent significant liquid seepage from the phosphate tailings, and then stirring and mixing after addition. In some embodiments, the stirring speed is 100 r / min for 10 min, and the mass ratio of industrial waste acid to phosphate tailings is 1:25.

[0042] To better verify the technical effects of this invention, our research team conducted the following experimental studies, the details of which are described below:

[0043] Phosphogypsum was sourced from a wet-process phosphoric acid production enterprise in Guizhou Province. Its physicochemical properties are shown in Table 1 below:

[0044] Table 1

[0045]

[0046] The lime cyanide slag originated from a thiourea production enterprise in Guizhou Province, and its elemental composition is shown in Table 2 below:

[0047] Table 2

[0048]

[0049] The phosphorus tailings slag originated from a phosphate mine beneficiation enterprise in Guizhou Province, and its composition is shown in Table 3 below:

[0050] Table 3

[0051]

[0052] The residual acid was sourced from a wet-process phosphoric acid purification production enterprise in Guizhou Province, and its composition is shown in Table 4 below:

[0053] Table 4

[0054]

[0055] The industrial waste sulfuric acid originated from a sulfuric acid production enterprise in Guizhou Province, and its sulfate content was 165,199.27 ppm.

[0056] Experiment 1: Study on the effect of activated slag addition on the performance of soil conditioner.

[0057] 1. Sample preparation:

[0058] Example 1:

[0059] Phosphogypsum was air-dried to a moisture content of 23.4%, then pulverized through a 100-mesh sieve to obtain phosphogypsum powder. Phosphate tailings were pulverized through a 100-mesh sieve, then roasted at 900℃ for 30 minutes and naturally cooled to room temperature to obtain activated slag. Phosphogypsum and activated slag were mixed at a mass ratio of 10:0.5, and industrial waste acid (extracting acid from phosphoric acid purification process) was added to adjust the pH value to between 5 and 6.5. The mixture was then aged for 48 hours and granulated into particles with a particle size between 1 and 4 mm to obtain the final product.

[0060] Example 2:

[0061] The calcium cyanide slag was air-dried to a moisture content of 24.5%, then crushed and passed through a 100-mesh sieve to obtain calcium cyanide slag powder. Activated slag was prepared according to the preparation method in Example 1. The calcium cyanide slag powder and activated slag were mixed at a mass ratio of 1:1, and industrial waste acid (extractant acid produced by phosphoric acid purification process) was added to adjust the pH value to between 5 and 6.5. After aging for 48 hours, the mixture was granulated into particles with a particle size between 1 and 4 mm to obtain the final product.

[0062] Example 3:

[0063] Phosphogypsum powder and activated slag were prepared according to the preparation method of Example 1, and calcium cyanamide slag powder was prepared according to the preparation method of Example 2. The phosphogypsum powder and calcium cyanamide slag powder were mixed at a mass ratio of 10:1, and then 5% of the mass of activated slag was added. Industrial waste acid (extracted acid produced by phosphoric acid purification process) was added to adjust the pH value to between 5 and 6.5. After aging for 48 hours, the mixture was granulated into particles with a particle size between 1 and 4 mm.

[0064] Example 4:

[0065] Phosphogypsum powder was prepared according to the preparation method in Example 1, and calcium cyanamide slag powder was prepared according to the preparation method in Example 2. The phosphogypsum powder and calcium cyanamide slag powder were mixed at a mass ratio of 10:0.5, and industrial waste acid (extracted acid produced by phosphoric acid purification process) was added to adjust the pH value to between 5 and 6.5. After aging for 48 hours, the mixture was granulated into particles with a particle size between 1 and 4 mm.

[0066] 2. Testing

[0067] The samples prepared in Examples 1 to 4 were subjected to pH and F... - The following parameters were tested: (%), arsenic (mg / kg), cadmium (mg / kg), lead (mg / kg), chromium (mg / kg), mercury (mg / kg), thallium (mg / kg), etc., and the results are recorded in Table 5 below:

[0068] Table 5

[0069]

[0070]

[0071] As shown in Tables 1 to 5, when phosphogypsum, calcium cyanamide slag, and activated slag are mixed in appropriate proportions, pH is adjusted, the mixture is aged, and granulated to prepare a soil conditioner, the soil conditioner can synergistically solidify heavy metals, reduce the detectable amount of heavy metals, and improve the quality of the soil conditioner.

[0072] 3. Application Test

[0073] 3.1 Strawberry pot experiment

[0074] The soil conditioner obtained in Example 3 was used in a potted strawberry experiment. All other treatments were the same for the potted strawberries. In the experimental group (2 pots), the soil conditioner prepared in Example 3 was added to the soil at 30% of the soil mass and mixed thoroughly. In the control group (1 pot), strawberries were directly cultivated in soil without the added soil conditioner. The total weight of soil and soil conditioner in the experimental group was equal to the soil weight in the control group.

[0075] The soil condition indicators used are shown in Table 6 below:

[0076] A: Hydrolyzable nitrogen, mg / kg; B: Available phosphorus, mg / kg; C: Cation exchange capacity, cmol(+) / kg; D: Available sulfur, mg / kg.

[0077] Table 6

[0078]

[0079] Observe the growth of strawberries (e.g.) Figure 3As shown in the figure: the strawberry plants in the experimental group grew vigorously and uniformly; the strawberry plants in the control group had small roots, uneven growth, and yellowing leaves.

[0080] 3.2 Mint Potted Plant Experiment

[0081] Following the procedure for strawberry pot experiments, the soil conditioner prepared in Example 3 was used in potted mint experiments. The soil conditioner was added to the soil at a concentration of 30% of the soil mass and mixed thoroughly. The growth of the mint was then observed (e.g., ...). Figure 4 As shown in the figure: The experimental group (3 pots) had tall and robust mint plants with uniform growth; the control group (1 pot) had small roots and stems with uneven growth.

[0082] 3.3 Testing of soil indicators for potted plants

[0083] The soil parameters after conditioning in the experimental group were tested, and the results are shown in Table 7 below:

[0084] Table 7

[0085]

[0086] It is evident that the soil conditioner created in this invention can improve soil properties and promote the growth of strawberry plants.

[0087] Experiment 2: Study on the Influence of Different Preparation Methods on the Performance of Soil Conditioners

[0088] 1. Preparation of test samples

[0089] Example 5

[0090] Phosphogypsum powder and activated slag were prepared according to the preparation method of Example 1, and calcium cyanamide slag powder was prepared according to the preparation method of Example 2. The phosphogypsum powder and calcium cyanamide slag powder were mixed in a mass ratio of 10:1.3 to form a mixture. Then, activated slag was added at 5% of the mass of phosphogypsum powder, and industrial waste acid (extracted acid from phosphoric acid purification process) was added to adjust the pH value to between 5 and 6.5. After aging for 48 hours, the mixture was granulated into particles with a particle size between 1 and 4 mm to obtain the final product.

[0091] Example 6

[0092] Phosphogypsum powder and activated slag were prepared according to the preparation method of Example 1, and calcium cyanamide slag powder was prepared according to the preparation method of Example 2. The phosphogypsum powder and calcium cyanamide slag powder were mixed in a mass ratio of 10:1 to form a mixture. Then, activated slag was added at 1% of the mass of phosphogypsum powder, and industrial waste acid (extracted acid from phosphoric acid purification process) was added to adjust the pH value to between 5 and 6.5. After aging for 48 hours, the mixture was granulated into particles with a particle size between 1 and 4 mm to obtain the final product.

[0093] Example 7

[0094] Phosphogypsum powder and activated slag were prepared according to the preparation method of Example 1, and calcium cyanamide slag powder was prepared according to the preparation method of Example 2. The phosphogypsum powder and calcium cyanamide slag powder were mixed in a mass ratio of 10:0.8 to form a mixture. Then, activated slag was added at 12% of the mass of phosphogypsum powder, and industrial waste acid (extracted acid produced by phosphoric acid purification process) was added to adjust the pH value to between 5 and 6.5. After aging for 72 hours, the mixture was granulated into particles with a particle size between 1 and 4 mm to obtain the final product.

[0095] Example 8

[0096] Based on Example 5, phosphogypsum powder and calcium cyanamide slag powder were mixed in a mass ratio of 5:1 to form a mixture, and all other aspects were the same as in Example 5.

[0097] Example 9

[0098] Based on Example 5, activated slag was added at 20% of the mass of phosphogypsum powder, and all other aspects were the same as in Example 5.

[0099] Example 10

[0100] Based on Example 5, all other aspects are the same as in Example 5. The activated slag is obtained by crushing phosphorus tailings through a 100-mesh sieve, then acidifying it with industrial waste acid (extracting acid produced by phosphoric acid purification process) (stirring at 100 r / min for 10 min, with a mass ratio of industrial waste acid to phosphorus tailings of 1:25), and then air-drying it to a moisture content of 0.67%.

[0101] 2. Testing

[0102] The samples prepared in Examples 5 to 10 were subjected to pH and F... - The following parameters were tested: (%), arsenic (mg / kg), cadmium (mg / kg), lead (mg / kg), chromium (mg / kg), mercury (mg / kg), thallium (mg / kg), etc., and the test results are recorded in Table 8 below:

[0103] Table 8

[0104]

[0105] Note: The samples obtained in Example 8 were tested by a third party for cadmium (mg / kg), lead (mg / kg), chromium (mg / kg), mercury (mg / kg), and thallium (mg / kg).

[0106] As shown in Tables 5 and 8, changes in the raw material ratio and preparation process will affect the quality of soil conditioners, leading to changes in the detectable heavy metal content in soil conditioners.

[0107] For any other matters not covered in this invention, they can be addressed by referring to existing technologies or common knowledge known to those skilled in the art, and by conventional technical means. For example, the industrial waste acid used in this invention can be waste acid produced by the sulfuric acid production process or residual acid produced by the phosphoric acid purification process.

Claims

1. A method for preparing a soil conditioner by treating phosphogypsum with lime cyanide slag, characterized in that, Includes the following steps: (1) The phosphogypsum and calcium cyanamide slag were air-dried to a moisture content of ≤25%, and then crushed and sieved to obtain phosphogypsum powder and calcium cyanamide slag powder. (2) Mix phosphogypsum powder and calcium cyanamide slag powder evenly at a mass ratio of 10:0.1-2 to obtain a mixture; (3) The mixture is modified by adding 1-20% activated slag to phosphogypsum, adjusting the pH to 5-6.5, aging for at least 24 hours, and then granulating. The activated slag is obtained by crushing and sieving phosphorus tailings, roasting them at 850-950℃ for 30 minutes, and then cooling them to room temperature under natural conditions; or the activated slag is obtained by crushing and sieving phosphorus tailings, acidifying them with industrial waste acid, and then air-drying them to a moisture content of ≤25%. The pH value is adjusted using industrial waste acid; the industrial waste acid is the residual acid produced during the purification of phosphoric acid production; or the industrial waste acid is the waste acid produced during the sulfuric acid production process.

2. The method as described in claim 1, characterized in that, The crushing and sieving process involves passing the material through an 80-100 mesh sieve.

3. The method as described in claim 1, characterized in that, The moisture content of the phosphorus tailings powder is ≤10%.

4. The method as described in claim 1 or 3, characterized in that, The moisture content of the phosphorus tailings powder is 0.67%.

5. The method as described in claim 1, characterized in that, The aging process takes 24-72 hours.

6. The method as described in claim 1 or 5, characterized in that, The aging process takes 48 hours.

7. The method as described in claim 1, characterized in that, The granulation process involves granulating particles with a diameter of 1-4 mm.

8. A soil conditioner prepared by the method according to any one of claims 1-7.

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