A method of increasing the filtration rate of calcium sulfate complexes

Abstract

The application discloses a method for increasing the filtering speed of a calcium sulfate complex, and steps are as follows: step 1, a solution containing a calcium sulfate complex is mixed with a composite solvent for reaction; and step 2, after the reaction is completed, the suspension is separated by suction filtration to obtain a clear filtrate and a phosphogypsum residue. In the production process of purifying phosphogypsum to prepare high-purity calcium sulfate by using a complexing agent to interact with calcium sulfate in the phosphogypsum, the organic impurities in the phosphogypsum adhere to the surface of the phosphogypsum residue, and other metal ion impurities in the phosphogypsum are complexed with the complexing agent, so that the viscosity of the phosphogypsum residue is large, the filtering speed is slow, and the production efficiency is reduced. The composite solvent is added to effectively increase the complexing efficiency of the complexing agent and the calcium sulfate, reduce the mass of the phosphogypsum residue, further increase the filtering speed, improve the production efficiency, and lay a solid foundation for large-scale comprehensive application of the phosphogypsum.

Description

Technical Field

[0001] This invention relates to the field of separation science and technology, to the treatment of industrial solid waste and the treatment and resource utilization of phosphogypsum, and specifically to a method for increasing the filtration speed of calcium sulfate complexes. Background Technology

[0002] Phosphogypsum is a byproduct of the wet-process phosphoric acid production. Its main component is calcium sulfate dihydrate, followed by free water, organic matter, heavy metals, rare earth elements, and potentially radioactive elements. Additionally, phosphogypsum contains surfactants introduced during mineral processing and impurities such as phosphoric acid dissolved in water. Generally, producing one ton of phosphoric acid generates approximately five tons of phosphogypsum. The presence of various impurities limits the feasibility of directly using phosphogypsum as gypsum, and the global utilization rate of phosphogypsum is less than 20%. Phosphogypsum is primarily disposed of through stockpiling, with global stockpiles exceeding 6 billion tons. Long-term stockpiling of phosphogypsum continuously exposes various serious environmental problems.

[0003] Low-cost reduction and high-value utilization of phosphogypsum are the most critical factors in solving the problem of phosphogypsum stockpiling and accumulation.

[0004] In the current production process of purifying phosphogypsum to prepare high-purity calcium sulfate by using complexing agents to interact with calcium sulfate in phosphogypsum, the presence of various impurities in phosphogypsum leads to a high viscosity of the slurry formed by phosphogypsum and complexing agents, and the phosphogypsum residue is prone to agglomeration. This makes the filtration process of separating phosphogypsum residue and calcium complex extremely slow, which greatly reduces production efficiency. Summary of the Invention

[0005] This invention solves the current problem of easy agglomeration of phosphogypsum residue, the problem of slow filtration speed when separating phosphogypsum residue from calcium complex, and the problem of environmental pollution caused by long-term storage of phosphogypsum.

[0006] To achieve the above objectives, the present invention provides a method for increasing the filtration rate of calcium sulfate complexes, comprising the following steps: S1. Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; S2. Add the phosphogypsum suspension obtained in step S1 to a composite solvent to obtain a mixed solution; S3. The mixed solution obtained in step S2 is heated and stirred to react. After the reaction is completed, the solution is filtered to obtain a clear calcium complex solution filtrate and phosphogypsum residue.

[0007] The organic solvents in step S1 include hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution, with a volume ratio of hydroxyethylidene diphosphonic acid solution: ethylenediaminetetraacetic acid solution: aminotriacetic acid solution = 1:1:1~1:10:10.

[0008] In step S1, the concentrations of the hydroxyethylidene diphosphonic acid solution, the ethylenediaminetetraacetic acid solution, and the aminotriacetic acid solution in the organic solvents are 1-10 g / L, 5-50 g / L, and 5-50 g / L, respectively.

[0009] In step S2, the ratio of composite solvent to phosphogypsum suspension is 1:100 to 1:1000 by volume.

[0010] In step S2, the composite solvent includes one or more of the following: sulfosalicylic acid solution, citric acid solution, triammonium citrate solution, lactic acid solution, humic acid solution, polyacrylic acid solution, succinic acid solution, sodium polyaspartate solution, sodium gluconate solution, and sodium tripolyphosphate solution.

[0011] In step S2, the concentrations of the following solutions are as follows: sulfosalicylic acid solution 100 g / L, citric acid solution 100 g / L, triammonium citrate solution 100 g / L, lactic acid solution 100 g / L, humic acid solution 100 g / L, polyacrylic acid solution 100 g / L, succinic acid solution 100 g / L, sodium polyaspartate solution 200 g / L, sodium gluconate solution 100 g / L, and sodium tripolyphosphate solution 200 g / L.

[0012] In step S3, the heating temperature is 20℃~80℃, and the reaction time is 0.5~3h.

[0013] In step S3, the stirring rate is 100 r / min to 1000 r / min.

[0014] In step S3, the moisture content of the phosphogypsum residue is ≤40 wt%.

[0015] In step S1, the phosphogypsum comprises calcium sulfate, silicon dioxide, water, and impurities, with the following mass fractions: calcium sulfate 70%, silicon dioxide 13%, water 15%, and impurities 2%.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention reduces the adhesion of organic impurities in phosphogypsum to the surface of phosphogypsum residue by adding a composite solvent, which greatly accelerates the filtration speed of phosphogypsum residue. At the same time, the added organic solvent complexes with other metal ion impurities in phosphogypsum, effectively increasing the complexing efficiency of the complexing agent, reducing the mass of phosphogypsum residue, and further increasing the filtration speed.

[0017] 2. This invention improves the filtration speed of phosphogypsum residue, with a simple process and low production cost. The process has a series of advantages such as high efficiency, simple operation, low energy consumption, green environmental protection, and easy industrialization. The phosphogypsum residue obtained is mainly composed of silica sand, which can be used in road paving, cement production and processing and other fields, realizing the reduction and high-value utilization of phosphogypsum.

[0018] 3. The organic solvent used in this invention acts as a complexing agent to complex calcium sulfate in phosphogypsum to form a calcium complex solution. The complex is then decomplexed to obtain calcium sulfate with a purity of over 99%. Calcium sulfate can be directly used as a raw material in the construction and papermaking industries. Detailed Implementation

[0019] To make the present invention easier to understand, the present invention will be further described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of the present invention. Unless otherwise specified, the raw materials or components used in the present invention can be purchased commercially or obtained by conventional methods.

[0020] In some preferred embodiments of the present invention, in step A, the composite solvent includes one or more of sulfosalicylic acid, citric acid, triammonium citrate, lactic acid, humic acid, polyacrylic acid, succinic acid, sodium polyaspartate, sodium gluconate, and sodium tripolyphosphate.

[0021] Phosphogypsum mainly contains 70% calcium sulfate, 13% silicon dioxide, 15% water, and 2% impurities by mass.

[0022] The concentrations of the following solutions are: sulfosalicylic acid solution (100 g / L), citric acid solution (100 g / L), triammonium citrate solution (100 g / L), lactic acid solution (100 g / L), humic acid solution (100 g / L), polyacrylic acid solution (100 g / L), succinic acid solution (100 g / L), sodium polyaspartate solution (200 g / L), sodium gluconate solution (100 g / L), and sodium tripolyphosphate solution (200 g / L).

[0023] In some embodiments and comparative examples, the preferred composite solvent comprises a citric acid solution and a sodium gluconate solution, with a volume ratio of citric acid solution:sodium gluconate solution = 1:0.5~1.

[0024] Preferably, the composite solvent includes sodium polyaspartate solution and triammonium citrate solution, with a volume ratio of sodium polyaspartate solution:triammonium citrate solution = 1:0.5~1.

[0025] Preferably, the composite solvent includes humic acid solution and sodium gluconate solution, with a volume ratio of humic acid solution: sodium gluconate solution = 1: 0.5~1.

[0026] Preferably, the composite solvent comprises a sulfosalicylic acid solution and a citric acid solution, wherein the ratio of the sulfosalicylic acid solution to the citric acid solution is 1:0.5~1.

[0027] Preferably, the composite solvent is composed of a lactic acid solution and a succinic acid solution, with the volume ratio of lactic acid solution to succinic acid solution being 1:0.5~1.

[0028] Preferably, the composite solvent is composed of humic acid solution and sulfosalicylic acid solution, and the volume ratio of humic acid solution to sulfosalicylic acid solution is 1:0.5~1.

[0029] Preferably, the composite solvent includes sulfosalicylic acid solution, citric acid solution, lactic acid solution, polyacrylic acid solution, succinic acid solution, sodium tripolyphosphate solution, and polyaspartic acid solution, in a volume ratio of sulfosalicylic acid solution: citric acid solution: lactic acid solution: polyacrylic acid solution: succinic acid solution: sodium tripolyphosphate solution: polyaspartic acid solution = 1: 0.5~1: 0.5~1: 0.5~1: 0.5~1: 0.5~1: 0.5~1.

[0030] Example 1 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The phosphogypsum suspension contains phosphogypsum with a concentration of 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0031] Then, the organic solvent is obtained by mixing hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10.

[0032] Step 2: Add the phosphogypsum suspension obtained in Step 1 to a composite solvent to obtain a mixed solution; The composite solvent consists of 100 g / L citric acid solution and 100 g / L sodium gluconate solution, with a ratio of 1:0.5~1 between the citric acid solution and the sodium gluconate solution. The amount added is 1:100 between the composite solvent and the phosphogypsum suspension.

[0033] Step 3: The mixed solution obtained in Step 2 is reacted at 40℃ with a stirring speed of 600 r / min for 0.5 h. After the reaction is completed, the solution is filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time of 1 L of reaction solution is 32 s. The phosphogypsum residue obtained by filtration is in powder form without agglomeration, and the water content of the phosphogypsum residue is 35.16%.

[0034] Example 2 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The phosphogypsum suspension contains phosphogypsum with a concentration of 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0035] Then, the organic solvent is obtained by mixing hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10.

[0036] Step 2: Add the phosphogypsum suspension obtained in Step 1 to a composite solvent to obtain a mixed solution.

[0037] The composite solvent consists of 100 g / L humic acid solution and 100 g / L sodium gluconate solution, with a ratio of 1:0.5~1 between the humic acid solution and the sodium gluconate solution. The amount added is 1:400 for the composite solvent to the phosphogypsum suspension.

[0038] Step 3: The mixed solution obtained in Step 2 is reacted at 50℃ with a stirring speed of 800 r / min for 1 h. After the reaction is completed, the solution is filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time of 1 L of reaction solution is 67 s. The phosphogypsum residue obtained by filtration is in powder form without agglomeration, and the water content of the phosphogypsum residue is 37.59%.

[0039] Example 3 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The phosphogypsum suspension contains phosphogypsum with a concentration of 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0040] Then, mix the hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10 to obtain the organic solvent; Step 2: Add the phosphogypsum suspension obtained in Step 1 to a composite solvent to obtain a mixed solution.

[0041] The composite solvent consists of 100 g / L sulfosalicylic acid solution and 100 g / L citric acid solution, with a ratio of 1:0.5~1 between the sulfosalicylic acid solution and the citric acid solution. The amount added is composite solvent: phosphogypsum suspension = 1:800.

[0042] Step 3: The mixed solution obtained in Step 2 is reacted at 80℃ with a stirring speed of 1000 r / min for 2 h. After the reaction is completed, the solution is filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time of 1 L of reaction solution is 46 s. The phosphogypsum residue obtained by filtration is in powder form without agglomeration. The water content of the phosphogypsum residue is 36.31%.

[0043] Example 4 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The phosphogypsum suspension contains phosphogypsum with a concentration of 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0044] Then, mix the hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10 to obtain the organic solvent; Step 2: Add the phosphogypsum suspension obtained in Step 1 to a composite solvent to obtain a mixed solution.

[0045] The composite solvent consists of 100 g / L lactic acid solution and 100 g / L succinic acid solution, with a ratio of 1:0.5~1 between the lactic acid solution and the succinic acid solution. The amount added is 1:100 for the composite solvent to phosphogypsum suspension.

[0046] Step 3: The mixed solution obtained in Step 2 was reacted at 40℃ with a stirring speed of 600 r / min for 0.5 h. After the reaction was completed, the solution was filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time of 1 L of reaction solution was 58 s. The phosphogypsum residue obtained by filtration was powdery and without agglomeration. The water content of the phosphogypsum residue was 37.14%.

[0047] Example 5 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The phosphogypsum suspension contains phosphogypsum with a concentration of 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0048] Then, the organic solvent is obtained by mixing hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10.

[0049] Step 2: Add the phosphogypsum suspension obtained in Step 1 to a composite solvent to obtain a mixed solution.

[0050] The composite solvent consists of a 100 g / L humic acid solution and a 100 g / L sulfosalicylic acid solution, with a ratio of 1:0.5~1 between the humic acid solution and the sulfosalicylic acid solution. The amount added is composite solvent: phosphogypsum suspension = 1:100.

[0051] Step 3: The mixed solution obtained in Step 2 is reacted at 40℃ with a stirring speed of 600 r / min for 0.5 h. After the reaction is completed, the solution is filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time of 1 L of reaction solution is 65 s. The phosphogypsum residue obtained by filtration is in powder form without agglomeration, and the water content of the phosphogypsum residue is 37.50%.

[0052] Comparative Example 1 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The concentration of phosphogypsum in the phosphogypsum suspension is 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0053] Then, the organic solvent is obtained by mixing hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10.

[0054] Step 2: Without adding a composite solvent, the phosphogypsum suspension from Step 1 was directly reacted at 40℃ with a stirring speed of 600 r / min for 0.5 h. After the reaction, the solution was filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time for 1 L of reaction solution was 663 s. The phosphogypsum residue obtained by filtration showed agglomeration and had a water content of 50.82%.

[0055] Comparative Example 2 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The phosphogypsum suspension contains phosphogypsum with a concentration of 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0056] Then, the organic solvent is obtained by mixing hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10.

[0057] Step 2: Add the phosphogypsum suspension obtained in Step 1 to a composite solvent to obtain a mixed solution.

[0058] The composite solvent is a 100 g / L citric acid solution, and the ratio of composite solvent to phosphogypsum suspension is 1:100.

[0059] Step 3: The mixed solution obtained in Step 2 is reacted at 40℃ with a stirring speed of 600 r / min for 0.5 h. After the reaction is completed, the solution is filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time of 1 L of reaction solution is 85 s. The phosphogypsum residue obtained by filtration is in powder form without agglomeration, and the water content of the phosphogypsum residue is 38.55%.

[0060] Comparative Example 3 Step 1: Add phosphogypsum to an organic solvent to obtain a phosphogypsum suspension; The phosphogypsum suspension contains phosphogypsum with a concentration of 100 g / L. Hydroxyethylidene diphosphonic acid, ethylenediaminetetraacetic acid, and aminotriacetic acid are dissolved in water to obtain hydroxyethylidene diphosphonic acid solutions with concentrations of 1-10 g / L, ethylenediaminetetraacetic acid solutions with concentrations of 5-50 g / L, and aminotriacetic acid solutions with concentrations of 1-5 g / L, respectively.

[0061] Then, mix the hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution in a volume ratio of 1:1:1 to 1:10:10 to obtain the organic solvent; Step 2: Add the phosphogypsum suspension obtained in Step 1 to a composite solvent to obtain a mixed solution.

[0062] The composite solvent consists of 100 g / L sulfosalicylic acid, 100 g / L citric acid, 100 g / L lactic acid, 100 g / L polyacrylic acid, 100 g / L succinic acid, 200 g / L sodium tripolyphosphate, and 200 g / L polyaspartic acid. The solution ratio of sulfosalicylic acid, citric acid, lactic acid, polyacrylic acid, succinic acid, sodium tripolyphosphate, and polyaspartic acid is 1: 0.5~1: 0.5~1: 0.5~1: 0.5~1: 0.5~1, and the added amount is composite solvent: phosphogypsum suspension = 1:100.

[0063] Step 3: The mixed solution obtained in Step 2 is reacted at 40℃ with a stirring speed of 600 r / min for 0.5 h. After the reaction is completed, the solution is filtered at 0.1 MPa and 25℃ to obtain phosphogypsum residue and calcium complex solution. According to analysis and calculation, the filtration time of 1 L of reaction solution is 71 s. The phosphogypsum residue obtained by filtration is in powder form without agglomeration, and the water content of the phosphogypsum residue is 38.25%.

[0064] Add a decomplexing agent to the calcium complex solution, react for 0.5-2 hours at a temperature of 20-80℃. The concentration of the decomplexing agent is 10-50 g / L, and the volume ratio of decomplexing agent to calcium complex solution is 1:50 mL / mL to 1:500 mL / mL. The decomplexing agent can be one or more of sulfuric acid, hydrochloric acid, ammonium sulfate, ammonium bisulfate, formic acid, and acetic acid. After the reaction, pure calcium sulfate with a purity of over 99% is obtained.

[0065] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for increasing the filtration rate of calcium sulfate complexes, characterized in that, Includes the following steps: S1. Phosphogypsum is added to an organic solvent to obtain a phosphogypsum suspension; the organic solvent includes hydroxyethylidene diphosphonic acid solution, ethylenediaminetetraacetic acid solution, and aminotriacetic acid solution, with a volume ratio of hydroxyethylidene diphosphonic acid solution: ethylenediaminetetraacetic acid solution: aminotriacetic acid solution = 1:1:1~1:10:10; the concentration of hydroxyethylidene diphosphonic acid solution in the organic solvent is 1~10 g / L, the concentration of ethylenediaminetetraacetic acid solution is 5~50 g / L, and the concentration of aminotriacetic acid solution is 5~50 g / L; S2. Add the phosphogypsum suspension obtained in step S1 to a composite solvent to obtain a mixed solution. The composite solvent consists of 100 g / L citric acid solution and 100 g / L sodium gluconate solution, with a ratio of citric acid solution to sodium gluconate solution of 1:0.5~1, and the amount added is composite solvent:phosphogypsum suspension = 1:100; or, the composite solvent consists of 100 g / L humic acid solution and 100 g / L sodium gluconate solution, with a ratio of humic acid solution to sodium gluconate solution of 1:0.5~1, and the amount added is composite solvent:phosphogypsum suspension = 1:400; or, the composite solvent consists of 100 g / L sulfosalicylic acid solution and 100 g / L citric acid solution, with a ratio of sulfosalicylic acid solution to citric acid solution of 1:0.5~1, and the amount added is composite solvent:phosphogypsum suspension = 1:800; or, the composite solvent consists of 100 g / L lactic acid solution and 100 g / L sulfosalicylic acid solution. The solution is composed of 100 g / L succinic acid solution, with a lactic acid solution to succinic acid solution ratio of 1:0.5~1, and the amount added is the composite solvent: phosphogypsum suspension = 1:100; or, the composite solvent is composed of 100 g / L humic acid solution and 100 g / L sulfosalicylic acid solution, with a humic acid solution to sulfosalicylic acid solution ratio of 1:0.5~1, and the amount added is the composite solvent: phosphogypsum suspension = 1:100; S3. The mixed solution obtained in step S2 is heated and stirred to react. After the reaction is completed, the solution is filtered to obtain a clear calcium complex solution filtrate and phosphogypsum residue.

2. The method for increasing the filtration rate of calcium sulfate complex according to claim 1, characterized in that, In step S3, the heating temperature is 20℃~80℃, and the reaction time is 0.5~3h.

3. The method for increasing the filtration rate of calcium sulfate complex according to claim 1, characterized in that, In step S3, the stirring rate is 100 r / min to 1000 r / min.

4. The method for increasing the filtration rate of calcium sulfate complex according to claim 1, characterized in that, In step S3, the moisture content of the phosphogypsum residue is ≤40 wt%.

5. The method for increasing the filtration rate of calcium sulfate complex according to claim 1, characterized in that, In step S1, the phosphogypsum comprises calcium sulfate, silicon dioxide, water, and impurities, with the following mass fractions: calcium sulfate 70%, silicon dioxide 13%, water 15%, and impurities 2%.