Comprehensive utilization method and application of phosphate tailings

Abstract

The invention discloses a comprehensive utilization method and application of phosphate tailings, and the method comprises the following steps: S1, carrying out primary acidolysis on the phosphate tailings to obtain slag and a primary acidolysis solution; s2, the slag is subjected to flotation, and flotation concentrate, flotation tailings and flotation filtrate are obtained; the flotation filtrate is recycled to the flotation procedure; s3, the flotation concentrate is subjected to secondary acidolysis, and gypsum and secondary acidolysis liquid are obtained; s4, the gypsum is subjected to reverse flotation, and reverse flotation filtrate and white gypsum are obtained; the reverse flotation filtrate is recycled to a reverse flotation procedure; combining the primary acidolysis solution and the secondary acidolysis solution, and carrying out evaporation concentration to obtain a crystal filtrate and magnesium sulfate; recycling the crystallization filtrate to a primary acidolysis and / or secondary acidolysis process; the method integrates multiple acidolysis, flotation and reverse flotation operations to realize efficient recovery of calcium, magnesium and phosphorus, and the obtained recovered product is high in recovery rate and high in purity.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of phosphate tailings waste, and in particular to a comprehensive utilization method and application of phosphate tailings. Background Art

[0002] Phosphate tailings are solid waste generated during the beneficiation of phosphate ore and are low-grade phosphate ore. Phosphate tailings mainly contain dolomite, apatite and silica slag, with a CaO content of about 30-34%, a P2O5 content of about 5-8%, and a MgO content of about 12-18%. A large amount of surplus phosphate tailings are piled up in tailings ponds and farmland, which not only occupies a large amount of land resources and leads to a waste of mineral resources, but also causes serious pollution to the environment. Phosphate tailings are secondary resources rich in calcium and magnesium and low in phosphorus. Efficient and comprehensive utilization of phosphate tailings is an effective way to save resources, be green and environmentally friendly, improve economic benefits, and achieve sustainable development.

[0003] In the related art, the valuable elements in the phosphate tailings are recovered by flotation separation technology, but the recovery rate of the valuable elements is still low and the purity of the recovered products is low.

[0004] Therefore, a comprehensive utilization scheme of phosphate tailings needs to be provided to achieve high-value utilization of phosphate tailings. Summary of the invention

[0005] In view of this, the present application provides a comprehensive utilization method and application of phosphate tailings, which is used to solve the problem of how to achieve high-value utilization of phosphate tailings.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a method for comprehensive utilization of phosphate tailings, comprising the following steps: S1. The phosphate tailings are subjected to an acid hydrolysis to obtain slag and an acid hydrolysis solution; S2. Flotation slag to obtain flotation concentrate, flotation tailings and flotation filtrate; the flotation filtrate is recycled to the flotation process; S3. The flotation concentrate is subjected to secondary acid hydrolysis to obtain gypsum and secondary acid hydrolysis liquid; S4. The gypsum is reverse-floated to obtain a reverse-flotation filtrate and white gypsum; the reverse-flotation filtrate is reused in the reverse-flotation process; The primary acid hydrolysis solution and the secondary acid hydrolysis solution are combined and evaporated and concentrated to obtain a crystallization filtrate and magnesium sulfate; the crystallization filtrate is recycled to the primary acid hydrolysis and / or secondary acid hydrolysis process.

[0007] Preferably, the acid used for the primary acid hydrolysis is 10-40wt% sulfuric acid, and the molar ratio of sulfuric acid to dolomite in the phosphate tailings is (0.3-0.8):1.

[0008] Preferably, the temperature of the primary acid hydrolysis is 15-50°C and the time is 50-100 min.

[0009] Preferably, the flotation agent used in flotation is 1-5wt% of an alkylamine modified flotation agent, the flotation concentrate comprises a mixture of dolomite and gypsum, and the flotation tailings comprises a mixture of apatite and silicon slag.

[0010] Preferably, the acid used in the secondary acid hydrolysis is 20-50wt% sulfuric acid, and the mass ratio of sulfuric acid to flotation concentrate is (2-3):1.

[0011] Preferably, the temperature of the secondary acid hydrolysis is 50-100°C and the time is 50-100 min.

[0012] Preferably, the reverse flotation agent used for reverse flotation is a mixture of 1-5 wt % of an alkylphenol ether flotation agent and 0.1-0.5 wt % of a polyol.

[0013] Preferably, the method further comprises using flotation tailings as raw materials to prepare phosphate rock powder fertilizer.

[0014] Preferably, the primary acid hydrolysis, flotation, secondary acid hydrolysis and reverse flotation steps are all followed by suction filtration.

[0015] In a second aspect, the present application provides a comprehensive utilization method of phosphate tailings for use in recovering calcium, magnesium and phosphorus resources.

[0016] The beneficial effects of the present application are as follows: the present application first activates the tailings by sulfuric acid hydrolysis to improve the surface properties of the minerals, then efficiently separates apatite and silicon slag by flotation, further acidizes the flotation concentrate to convert all the remaining dolomite into gypsum, and then removes organic matter by reverse flotation to obtain high-quality gypsum, combines the two acid hydrolysis solutions, evaporates and concentrates them, and then crystallizes them to obtain magnesium sulfate crystals. This method can achieve efficient recovery of calcium, magnesium, and phosphorus, and the recovered product has a high recovery rate and high purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the process flow chart of this application; Figure 2 This is a scanning electron microscope image of the white gypsum obtained in Example 1; Figure 3 This is the particle size distribution diagram of the white gypsum obtained in Example 1. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] The present application provides a method for comprehensive utilization of phosphate tailings, comprising the following steps: S1. The phosphate tailings are subjected to an acid hydrolysis to obtain slag and an acid hydrolysis solution; S2. Flotation slag to obtain flotation concentrate, flotation tailings and flotation filtrate; the flotation filtrate is recycled to the flotation process; S3. The flotation concentrate is subjected to secondary acid hydrolysis to obtain gypsum and secondary acid hydrolysis liquid; S4. The gypsum is reverse-floated to obtain a reverse-flotation filtrate and white gypsum; the reverse-flotation filtrate is reused in the reverse-flotation process; The primary acid hydrolysis solution and the secondary acid hydrolysis solution are combined and evaporated and concentrated to obtain a crystallization filtrate and magnesium sulfate; the crystallization filtrate is recycled to the primary acid hydrolysis and / or secondary acid hydrolysis process.

[0020] The present application first activates the tailings by sulfuric acid hydrolysis to improve the surface properties of the minerals, then efficiently separates apatite and silicon slag by flotation, further acidizes the flotation concentrate to convert all the remaining dolomite into gypsum, and then removes organic matter by reverse flotation to obtain high-quality gypsum, combines the two acid hydrolysis solutions, evaporates and concentrates them, and then crystallizes them to obtain magnesium sulfate crystals. This method can achieve efficient recovery of calcium, magnesium and phosphorus, and the recovered product has high recovery rate and high purity.

[0021] In some embodiments, the acid used for the primary acid hydrolysis is 10-40 wt % sulfuric acid, and the molar ratio of sulfuric acid to dolomite in the phosphate tailings is (0.3-0.8):1.

[0022] In some embodiments, the temperature of the primary acid hydrolysis is 15-50° C. and the time is 50-100 min.

[0023] Specifically, in the primary acid hydrolysis step, the phosphate tailings are first prepared into a 15-40wt% slurry and then subjected to primary acid hydrolysis. The reaction is stopped when the pH value of the primary acid hydrolysis liquid reaches 4.7-5.5, and then filtered to obtain slag and the primary acid hydrolysis liquid. The slag contains incompletely decomposed dolomite, gypsum, apatite lime and silicon slag.

[0024] In some embodiments, the flotation agent used for flotation is 1-5 wt % of an alkylamine modified flotation agent; the flotation concentrate includes a mixture of dolomite and gypsum, and the flotation tailings includes a mixture of apatite and silicon slag.

[0025] Specifically, the slag is prepared into a 20-50wt% slurry, an alkylamine modified flotation agent is used as a flotation reagent, and the pH value is adjusted to 4.9-5.3 with 5wt% sulfuric acid, and flotation is carried out at room temperature. After flotation, filtration is performed to obtain flotation concentrate (gypsum, dolomite), flotation tailings (apatite, silica slag) and flotation filtrate. The preparation method of the alkylamine modified flotation agent is as follows: dodecylamine and acrylonitrile are mixed in a mass ratio of 3-5:1, heated under reflux at 40-60°C to obtain N-cyanoethyldodecylamine, Raney nickel is added to the N-cyanoethyldodecylamine in a mass ratio of 10:1-2 to obtain a mixed solution, and then an alkaline solution of NaBH4 is added dropwise to the mixed solution at 50-70°C. After the addition is completed, the mixture is stirred at room temperature for 8 hours, filtered, extracted with dichloromethane, and dried with anhydrous sodium sulfate. After filtering, the filtrate is evaporated to remove the solvent to obtain N-aminopropyldodecylamine solid, that is, the alkylamine modified flotation agent.

[0026] In some embodiments, the acid used for the secondary acid hydrolysis is 20-50 wt % sulfuric acid, and the mass ratio of sulfuric acid to flotation concentrate is (2-3):1.

[0027] In some embodiments, the secondary acid hydrolysis is carried out at a temperature of 50-100° C. and for a time of 50-100 min.

[0028] Specifically, the process of secondary acid hydrolysis is to mix sulfuric acid and concentrate, stir at room temperature until bubbles are no longer generated, heat to 50-100°C for acid hydrolysis, cool down and filter to obtain gypsum and secondary acid hydrolysis liquid.

[0029] In some embodiments, the reverse flotation agent used for reverse flotation is a mixture of 1-5 wt % of an alkylphenol ether flotation agent and 0.1-0.5 wt % of a polyol.

[0030] Specifically, reverse flotation is carried out at room temperature, and after removing organic matter, reverse flotation filtrate and white gypsum are obtained by suction filtration. Alkylphenol ether flotation reagents include one or more of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, tributylphenol polyoxyethylene ether, alkylphenol polyoxyethylene ether polyoxypropylene ether emulsifier No. 11, and phenethylphenol polyoxypropylene polyoxyethylene ether emulsifier No. 12.

[0031] In some embodiments, the method further includes using flotation tailings as raw materials to prepare phosphate rock fertilizer.

[0032] In some embodiments, the primary acid hydrolysis, flotation, secondary acid hydrolysis, and reverse flotation steps are followed by suction filtration.

[0033] The present application provides an application of a comprehensive utilization method of phosphate tailings in the recovery of calcium, magnesium and phosphorus resources.

[0034] The present solution is further described below through specific embodiments.

[0035] Example 1 A comprehensive utilization method of phosphate tailings comprises the following steps: S1. After the phosphate tailings are crushed, they are sieved through a 100-mesh sieve for later use. The contents of CaO, MgO and P2O5 in the phosphate tailings powder are analyzed by chemical analysis, and the consumption of 98% (mass concentration) sulfuric acid is calculated. Sulfuric acid is weighed according to 60% of the amount of sulfuric acid required for dolomite, and a 10% dilute sulfuric acid solution is prepared for later use. Add the phosphate tailings powder to the acidolysis reactor, and add water to prepare a 40% slurry. Under stirring conditions, the dilute sulfuric acid solution is slowly added dropwise, and the temperature is controlled at 25 ° C. After the addition is completed, an acidolysis is performed. When the pH of the acidolysis solution is measured to be 5.2, the acidolysis reaction is stopped, and the slag and the primary acidolysis solution are obtained by suction filtration; S2. The slag is prepared into a 26% slurry, and a 1wt% alkylamine modified flotation agent is used for flotation, and a 5% sulfuric acid solution is used as a pH adjuster to adjust the flotation pH to 5.2, and then flotation is carried out at room temperature (25°C). After filtration, flotation concentrate, flotation tailings and flotation filtrate are obtained; the flotation filtrate is recycled to the flotation process; the flotation tailings are used as phosphate rock powder fertilizer; S3. The flotation concentrate is added to the acid hydrolysis reactor, sulfuric acid is added dropwise according to the mass ratio of flotation concentrate: 30wt% sulfuric acid solution of 1:2.2, stirred at room temperature, and after bubbles are no longer generated, the temperature is raised to 70 ° C, reacted for 60 min, cooled, and filtered to obtain gypsum and secondary acid hydrolysis solution; S4. The gypsum is configured into a 26% slurry, and a mixture of 1wt% alkylphenol ether and 0.1wt% polyol is used as a reverse flotation agent for reverse flotation at room temperature (25°C) to remove organic matter. After filtration, a reverse flotation filtrate and white gypsum are obtained, and the reverse flotation filtrate is reused in the reverse flotation process; The primary acid hydrolysis solution and the secondary acid hydrolysis solution were combined, and the volume of the mixed solution (MgO content was 7.0wt%) was evaporated and concentrated to 0.8 times at 80°C, and the temperature was naturally lowered to obtain a crystallization filtrate and magnesium sulfate crystals; the crystallization filtrate was recycled to the sulfuric acid preparation process in step S1.

[0036] Example 2 A comprehensive utilization method of phosphate tailings comprises the following steps: S1. After the phosphate tailings are crushed, they are sieved through a 100-mesh sieve for later use. The contents of CaO, MgO and P2O5 in the phosphate tailings powder are analyzed by chemical analysis, and the consumption of 98% (mass concentration) sulfuric acid is calculated. Sulfuric acid is weighed according to 62% of the amount of sulfuric acid required for dolomite, and a 12% dilute sulfuric acid solution is prepared for later use. Add the phosphate tailings powder to the acid hydrolysis reactor, and add water to prepare a 30% slurry. Under stirring conditions, the dilute sulfuric acid solution is slowly added dropwise, and the temperature is controlled at 25 ° C. After the addition is completed, an acid hydrolysis is performed. When the pH of the acid hydrolysis solution is measured to be 5.24, the acid hydrolysis reaction is stopped, and the slag and the primary acid hydrolysis solution are obtained by suction filtration; S2. The slag is prepared into a 30% slurry, and a 2wt% alkylamine modified flotation agent is used for flotation, and an 8% sulfuric acid solution is used as a pH adjuster to adjust the flotation pH to 5, and then flotation is carried out at room temperature (25°C). After filtration, flotation concentrate, flotation tailings and flotation filtrate are obtained; the flotation filtrate is recycled to the flotation process; the flotation tailings are used as phosphate rock powder fertilizer; S3. The flotation concentrate is added to the acid hydrolysis reactor, sulfuric acid is added dropwise according to the mass ratio of flotation concentrate: 30wt% sulfuric acid solution of 1:2.0, stirred at room temperature, and after bubbles are no longer generated, the temperature is raised to 60 ° C, reacted for 80 min, cooled, and filtered to obtain gypsum and secondary acid hydrolysis solution; S4. The gypsum is configured into a 25% slurry, and a mixture of 2wt% alkylphenol ether and 0.3wt% polyol is used as a reverse flotation agent for reverse flotation at room temperature (25°C) to remove organic matter. After filtration, a reverse flotation filtrate and white gypsum are obtained, and the reverse flotation filtrate is reused in the reverse flotation process; The first acid hydrolysis solution and the second acid hydrolysis solution were combined, and the volume of the mixed solution (MgO content was 6.8wt%) was evaporated and concentrated to 0.75 times at 90°C, and the temperature was naturally lowered to obtain a crystallization filtrate and magnesium sulfate crystals; the crystallization filtrate was recycled to the sulfuric acid preparation process in step S1.

[0037] Example 3 A comprehensive utilization method of phosphate tailings comprises the following steps: S1. After the phosphate tailings are crushed, they are sieved through a 100-mesh sieve for later use. The contents of CaO, MgO and P2O5 in the phosphate tailings powder are analyzed by chemical analysis, and the consumption of 98% (mass concentration) sulfuric acid is calculated. Sulfuric acid is weighed according to 75% of the amount of sulfuric acid required for dolomite, and a 15% dilute sulfuric acid solution is prepared for later use. Add the phosphate tailings powder to the acid hydrolysis reactor, and add water to prepare a 30% ore slurry. Under stirring conditions, the dilute sulfuric acid solution is slowly added dropwise, and the temperature is controlled at 25 ° C. After the addition is completed, an acid hydrolysis is performed. When the pH of the primary acid hydrolysis solution is measured at 5.1, the acid hydrolysis reaction is stopped, and the slag and the primary acid hydrolysis solution are obtained by suction filtration; S2. The slag is prepared into a 28% slurry, and a 3wt% alkylamine modified flotation agent is used for flotation, and a 10% sulfuric acid solution is used as a pH adjuster to adjust the flotation pH to 4.8, and then flotation is carried out at room temperature (25°C). After filtration, flotation concentrate, flotation tailings and flotation filtrate are obtained; the flotation filtrate is recycled to the flotation process; the flotation tailings are used as phosphate rock powder fertilizer; S3. The flotation concentrate is added to the acid hydrolysis reactor, sulfuric acid is added dropwise according to the mass ratio of flotation concentrate: 35wt% sulfuric acid solution of 1:2.5, stirred at room temperature, and after bubbles are no longer generated, the temperature is raised to 80 ° C, reacted for 60 min, cooled, and filtered to obtain gypsum and secondary acid hydrolysis solution; S4. The gypsum is configured into a 30% slurry, and a mixture of 1wt% alkylphenol ether and 0.2wt% polyol is used as a reverse flotation agent for reverse flotation at room temperature (25°C) to remove organic matter. After filtration, a reverse flotation filtrate and white gypsum are obtained, and the reverse flotation filtrate is reused in the reverse flotation process; The primary acid hydrolysis solution and the secondary acid hydrolysis solution were combined, and the volume of the mixed solution (MgO content was 7.2wt%) was evaporated and concentrated to 0.72 times at 95°C, and the temperature was naturally lowered to obtain a crystallization filtrate and magnesium sulfate crystals; the crystallization filtrate was recycled to the sulfuric acid preparation process in step S1.

[0038] Example 4 A comprehensive utilization method of phosphate tailings comprises the following steps: S1. After the phosphate tailings are crushed, they are sieved through a 100-mesh sieve for later use. The contents of CaO, MgO and P2O5 in the phosphate tailings powder are analyzed by chemical analysis, and the consumption of 98% (mass concentration) sulfuric acid is calculated. Sulfuric acid is weighed according to 70% of the amount of sulfuric acid required for dolomite, and a 20% dilute sulfuric acid solution is prepared for later use. Add the phosphate tailings powder to the acidolysis reactor, and add water to prepare a 28% slurry. Under stirring conditions, the dilute sulfuric acid solution is slowly added dropwise, and the temperature is controlled at 25 ° C. After the addition is completed, an acidolysis is performed. When the pH of the acidolysis solution is measured at 4.9, the acidolysis reaction is stopped, and the slag and the primary acidolysis solution are obtained by suction filtration; S2. The slag is prepared into a 32% slurry, and a 2wt% alkylamine modified flotation agent is used for flotation, and a 10% sulfuric acid solution is used as a pH adjuster to adjust the flotation pH to 5.2, and then flotation is carried out at room temperature (25°C). After filtration, flotation concentrate, flotation tailings and flotation filtrate are obtained; the flotation filtrate is recycled to the flotation process; the flotation tailings are used as phosphate rock powder fertilizer; S3. The flotation concentrate is added to the acid hydrolysis reactor, sulfuric acid is added dropwise according to the mass ratio of flotation concentrate: 40wt% sulfuric acid solution of 1:2.8, stirred at room temperature, and after bubbles are no longer generated, the temperature is raised to 85 ° C, reacted for 60 min, cooled, and filtered to obtain gypsum and secondary acid hydrolysis solution; S4. The gypsum is configured into a 28% slurry, and a mixture of 1wt% alkylphenol ether and 0.3wt% polyol is used as a reverse flotation agent for reverse flotation at room temperature (25°C) to remove organic matter. After filtration, a reverse flotation filtrate and white gypsum are obtained, and the reverse flotation filtrate is reused in the reverse flotation process; The first acid hydrolysis solution and the second acid hydrolysis solution were combined, and the volume of the mixed solution (MgO content was 7.1wt%) was evaporated and concentrated to 0.8 times at 95°C, and the temperature was naturally lowered to obtain a crystallization filtrate and magnesium sulfate crystals; the crystallization filtrate was recycled to the sulfuric acid preparation process in step S1.

[0039] Comparative Example 1 A method for comprehensive utilization of phosphate tailings, the other contents of which are the same as those of Example 1, except that the primary acid hydrolysis process of step S1 is not included.

[0040] Comparative Example 2 A method for comprehensive utilization of phosphate tailings, other contents of which are the same as those of Example 1, except that the secondary acid hydrolysis process of step S3 is not included.

[0041] Test and Evaluation The SEM image of the white gypsum obtained in Example 1 was tested by electron microscopy, and the results were as follows: Figure 1 As shown, the particle size distribution of the white gypsum obtained in Example 1 is as follows Figure 2 shown.

[0042] The content of P2O5 was determined according to GB / T 23456-2018; the purity of magnesium sulfate was determined according to HG / T 2680-95, and the relevant parameters of the components obtained in each embodiment and comparative example were tested, and the results are shown in Table 1. After the first acid hydrolysis, the content of each component in the first acid hydrolysis solution, flotation concentrate, and flotation tailings is shown in Table 2.

[0043] Table 1 Test results of each component

[0044] As can be seen from Table 1, the P2O5 content obtained in Examples 1-4 is high, the recovery rate, purity and whiteness of white gypsum are high, the purity of magnesium sulfate reaches more than 94.2%, the apatite is less decomposed in one acid hydrolysis, and part of the apatite can be recycled and retained in the slag after flotation and can be directly used as a phosphate fertilizer, indicating that the scheme of the present application can achieve efficient recovery of calcium, magnesium and phosphorus, and the recovery rate and purity of the recovered product are high.

[0045] Table 2 Detection results of each component after one acid hydrolysis

[0046] The above results show that the present application first activates the tailings by sulfuric acid hydrolysis to improve the surface properties of the minerals, then efficiently separates apatite and silicon slag by flotation, further acidizes the flotation concentrate to convert all the remaining dolomite into gypsum, and then removes organic matter by reverse flotation to obtain high-quality gypsum, combines the two acid hydrolysis solutions, evaporates and concentrates them, and then crystallizes them to obtain magnesium sulfate crystals. This method can achieve efficient recovery of calcium, magnesium, and phosphorus, and the recovered product has high recovery rate and high purity.

[0047] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A comprehensive utilization method of phosphate tailings, characterized in that: The following steps are involved: The phosphate tailings are subjected to primary acid hydrolysis to obtain slag and primary acid hydrolysis liquid; Floating the slag to obtain flotation concentrate, flotation tailings and flotation filtrate; the flotation filtrate is recycled to the flotation process; The flotation concentrate is subjected to secondary acid hydrolysis to obtain gypsum and secondary acid hydrolysis liquid; Reverse flotation is performed on the gypsum to obtain reverse flotation filtrate and white gypsum, and the reverse flotation filtrate is recycled to the reverse flotation process; The primary acid hydrolysis solution and the secondary acid hydrolysis solution are combined and evaporated and concentrated to obtain a crystallization filtrate and magnesium sulfate. The crystallization filtrate is recycled to the primary acid hydrolysis and / or secondary acid hydrolysis step.

2. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The acid used in the primary acid hydrolysis is 10-40wt% sulfuric acid, and the molar ratio of the sulfuric acid to the dolomite in the phosphate tailings is (0.3-0.8):

1.

3. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The temperature of the primary acid hydrolysis is 15-50°C and the time is 50-100 minutes.

4. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The flotation agent used in the flotation is 1-5wt% of an alkylamine modified flotation agent; the flotation concentrate comprises a mixture of dolomite and gypsum, and the flotation tailings comprises a mixture of apatite and silicon slag.

5. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The acid used in the secondary acid hydrolysis is 20-50wt% sulfuric acid, and the mass ratio of the sulfuric acid to the flotation concentrate is (2-3):

1.

6. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The temperature of the secondary acid hydrolysis is 50-100° C. and the time is 50-100 min.

7. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The reverse flotation agent used in the reverse flotation is a mixture of 1-5wt% of alkylphenol ether flotation agent and 0.1-0.5wt% of polyol.

8. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The method also includes using the flotation tailings as a raw material to prepare phosphate rock powder fertilizer.

9. The comprehensive utilization method of phosphate tailings according to claim 1, characterized in that: The primary acid hydrolysis, flotation, secondary acid hydrolysis and reverse flotation steps are all followed by suction filtration.

10. Use of the comprehensive utilization method of phosphate tailings as described in any one of claims 1 to 9 in recovering calcium, magnesium and phosphorus resources.

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