Method for deeply purifying phosphate tailing acidolysis gypsum and application

Abstract

The invention provides a method for deep purification of phosphate tailing acidolysis gypsum and application, and belongs to the technical field of phosphate tailing resource utilization, and the method comprises the following steps: mixing the phosphate tailing acidolysis gypsum with a sulfuric acid solution for reaction, and after the reaction is completed, performing suction filtration to obtain recrystallized gypsum; the recrystallized gypsum and water are mixed to prepare ore pulp, the pH of the ore pulp is adjusted to be 1-5, a flotation agent is added for reverse flotation, organic matter and gypsum concentrate are obtained, the gypsum concentrate is dried, and white gypsum is obtained; the flotation agent comprises an alkylphenol ether compound and a polyol compound; the polyol compound is obtained by reaction of 4-methyl benzyl chloride and trihydroxymethyl aminomethane. The method can remove organic matters in the phosphate tailing acidolysis gypsum and improve the whiteness of the gypsum, so that the application range of the recovered gypsum is expanded, and the economic benefit is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phosphorus tailings resource utilization, and particularly relates to a method for deep purification of phosphorus tailings acidolysis gypsum and application. BACKGROUND

[0002] Phosphorus tailings are solid wastes generated in the process of phosphorus ore dressing and belong to low-grade phosphorus ore. The phosphorus tailings mainly contain dolomite, apatite and silicate, wherein the content of CaO is about 29% to 34%, the content of P2O5 is about 5% to 8%, and the content of MgO is about 11.5% to 18%. The accumulation of a large amount of phosphorus tailings not only causes serious environmental pollution, but also is a great waste of mineral resources. Separating calcium, magnesium and phosphorus from the phosphorus tailings and high-value utilization are effective ways for resource saving, green environmental protection, economic benefit improvement and sustainable development. At present, the phosphorus tailings are usually acid leached to recover the gypsum therein. The acid leaching can dissolve the phosphorus tailings and then recrystallize to obtain phosphorus tailings acidolysis gypsum. However, the acid leaching cannot completely remove the organic matter in the phosphorus tailings acidolysis gypsum, resulting in high content of organic matter in the phosphorus tailings acidolysis gypsum and black color, which cannot meet the relevant requirements of chemical filling and seriously affects the application of the phosphorus tailings acidolysis gypsum. SUMMARY

[0003] In view of the technical problems in the background art, the present application provides a method for deep purification of phosphorus tailings acidolysis gypsum and application, aiming at solving the technical problems of high content of organic matter and insufficient whiteness in the phosphorus tailings acidolysis gypsum.

[0004] In a first aspect, the present application provides a method for deep purification of phosphorus tailings acidolysis gypsum, comprising the following steps: S1, mixing and reacting the phosphorus tailings acidolysis gypsum with a sulfuric acid solution, and then obtaining recrystallized gypsum after filtration; S2, mixing the recrystallized gypsum with water to prepare a slurry, adjusting the pH of the slurry to 1 to 5, adding a flotation agent for reverse flotation to remove the organic matter, and then obtaining a gypsum concentrate after filtration, and drying the gypsum concentrate to obtain white gypsum; The flotation agent comprises an alkyl phenol ether compound and a polyol compound. The polyol compound is obtained by reacting 4-methyl chlorobenzyl with a trishydroxymethyl aminomethane.

[0005] In some embodiments, the concentration of the sulfuric acid solution in step S1 is 20 to 40 wt%, the reaction temperature is 60 to 80℃, and the reaction time is 20 to 100 min.

[0006] In some embodiments, the mass ratio of the phosphorus tailings acidolysis gypsum to the sulfuric acid solution is 1:(1.5 to 3.0).

[0007] In some embodiments, the concentration of the recrystallized gypsum in the slurry of step S2 is 25-28 wt%, the mass percentage of the alkyl phenol ether compound in the slurry is 1-5 wt%, and the mass percentage of the polyol compound in the slurry is 0.1-0.5 wt%.

[0008] In some embodiments, the alkyl phenol ether compound comprises at least one of octyl phenol ether, nonyl phenol polyoxyethylene ether, and nonyl phenol polyoxyethylene ether phosphate.

[0009] In some embodiments, the method for preparing the polyol compound comprises the following steps: dispersing 4-methyl chlorobenzyl and trishydroxymethyl aminomethane in ethanol, adding sodium carbonate, heating and refluxing, removing ethanol by distillation under reduced pressure, and obtaining the polyol compound after washing and drying the residue.

[0010] In some embodiments, the molar ratio of 4-methyl chlorobenzyl to trishydroxymethyl aminomethane is (1.1-1.15):1.

[0011] In some embodiments, the temperature of the heating and refluxing is 80-85℃, and the reaction time is 1-2.5 h.

[0012] In some embodiments, the method for preparing the acid-dissolved gypsum from phosphorus tailings comprises the following steps: mixing phosphorus tailings with sulfuric acid, heating to 85℃, and reacting for 2 h to obtain the acid-dissolved gypsum from phosphorus tailings, and the molar ratio of the phosphorus tailings to the sulfuric acid is 1:(1.1-1.15).

[0013] In the second aspect, the embodiments of the present application provide an application of the white gypsum in plastics, wherein the white gypsum is prepared by the method described above, and the white gypsum is modified by a silane coupling agent and applied to the filling of semi-crystalline thermoplastic or thermoplastic biodegradable plastics.

[0014] Compared with the prior art, the beneficial effects of the present application include: The acid-dissolved gypsum from phosphorus tailings is further recrystallized and subjected to reverse flotation treatment, so that other impurity metal oxides and organic matters in the acid-dissolved gypsum from phosphorus tailings can be removed, and the whiteness of the gypsum is improved, thereby expanding the application range of the recovered gypsum and improving the economic benefits. The white gypsum prepared by the present application can be applied to the filling of semi-crystalline thermoplastic (PP) and thermoplastic biodegradable plastics (PBAT) after surface modification, and high-value utilization of the phosphorus tailings is realized.

[0015] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented in accordance with the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0017] Figure 1 Flow chart for deep purification of phosphorus tailings acidolysis gypsum; Figure 2 Particle size distribution graph of white gypsum prepared in Example 1 of the present application; Figure 3 Particle size distribution graph of white gypsum prepared in Example 4 of the present application; Figure 4 Particle size distribution graph of white gypsum prepared in Example 7 of the present application. DETAILED DESCRIPTION

[0018] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0020] The main components in phosphorus tailings are dolomite and calcite, and the phosphorus tailings are acidolysed by using sulfuric acid to convert the calcium ions in dolomite and calcite into calcium sulfate (gypsum), i.e. to obtain phosphorus tailings acidolysis gypsum. The acidolysis of phosphorus tailings by using sulfuric acid is a common method for recovering gypsum in phosphorus tailings. However, the phosphorus tailings acidolysis gypsum obtained by only using acid leaching is black, has high content of organic matter, insufficient whiteness, and narrow application field.

[0021] In order to solve the technical problems of high content of organic matter and insufficient whiteness of phosphorus tailings acidolysis gypsum, the present application provides a method for deep purification of phosphorus tailings acidolysis gypsum, wherein through recrystallization and reverse flotation treatment, the technical effect of removing organic matter in phosphorus tailings acidolysis gypsum and improving the whiteness of gypsum can be achieved, and thus the high value-added utilization of phosphorus tailings is realized.

[0022] In a first aspect, the embodiments of the present application provide a method for deep purification of phosphorus tailings acidolysis gypsum, comprising the following steps: S1, the phosphorus tailing acidolysis gypsum is mixed with a sulfuric acid solution to react, and after the reaction is completed, the recrystallized gypsum is obtained by filtration; S2, after the recrystallized gypsum is mixed with water to prepare a slurry, the pH of the slurry is adjusted to 1-5, a flotation agent is added to perform reverse flotation, the organic matter is removed, and the white gypsum is obtained by filtration and drying of the gypsum concentrate. The flotation agent comprises an alkyl phenol ether compound and a polyol compound. The polyol compound is obtained by reacting 4-methyl chlorobenzyl with a trishydroxymethyl aminomethane.

[0023] In the technical scheme of the embodiment of the application, the phosphorus tailing acidolysis gypsum is treated again with sulfuric acid in step S1, which can further remove the metal oxides in the phosphorus tailing acidolysis gypsum, and the recrystallization reaction of calcium sulfate can be performed under dilute sulfuric acid and high temperature, so that the calcium sulfate is separated from the organic matter, the calcium sulfate is further purified, and the recrystallized gypsum is obtained.

[0024] The recrystallized gypsum is subjected to reverse flotation under the action of the alkyl phenol ether compound and the polyol compound, the alkyl phenol ether compound acts as a foaming agent, and the polyol compound acts as a collector. First, the pH is adjusted to 1-5, which can form a hydrophilic layer on the surface of the recrystallized gypsum, thereby reducing the ability of the recrystallized gypsum to adhere to bubbles. The polyol compound is obtained by reacting 4-methyl chlorobenzyl with a trishydroxymethyl aminomethane. The polyol compound contains hydroxyl groups, which can form hydrogen bonds with the organic matter to combine with the organic matter. The polyol compound has hydrophobicity, which enhances the hydrophobicity of the organic matter after the combination, so that the organic matter is easily adsorbed on the bubbles in the flotation process, and is floated out of the water phase, so that the organic matter is separated from the recrystallized gypsum. Therefore, the polyol compound in the application has a high removal efficiency for the organic matter. The alkyl phenol ether compound acts as a foaming agent, and the generated foam is small in size and low in viscosity, and is easy to defoam, which is conducive to the subsequent treatment.

[0025] In some embodiments, the concentration of the sulfuric acid solution in step S1 is 20-40 wt%, the reaction temperature is 60-80℃, and the reaction time is 20-100 min.

[0026] In some embodiments, the mass ratio of the phosphorus tailing acidolysis gypsum to the sulfuric acid solution is 1:(1.5-3.0).

[0027] In some embodiments, the concentration of the recrystallized gypsum in the slurry of step S2 is 25-28 wt%, the mass percentage of the alkyl phenol ether compound in the slurry is 1-5 wt%, and the mass percentage of the polyol compound in the slurry is 0.1-0.5 wt%.

[0028] In the technical scheme of the embodiment of the application, a small amount of alkyl phenol ether compound and polyol compound is added to remove the organic matter in the phosphorus tailing acidolysis gypsum.

[0029] In some embodiments, the alkyl phenol ether compound includes at least one of octyl phenol ether, nonyl phenol polyoxyethylene ether, nonyl phenol polyoxyethylene ether phosphate.

[0030] In some embodiments, the preparation method of the polyol compound includes the following steps: dispersing 4-methyl chlorobenzyl and trishydroxymethyl aminomethane in ethanol, adding sodium carbonate, heating to reflux, removing ethanol by distillation under reduced pressure, and obtaining the polyol compound after washing and drying the residue.

[0031] In the technical scheme of the embodiments of the present application, 4-methyl chlorobenzyl and trishydroxymethyl aminomethane undergo condensation reaction to generate the polyol compound.

[0032] In the technical scheme of the embodiments of the present application, 4-methyl chlorobenzyl and trishydroxymethyl aminomethane undergo condensation reaction to generate the polyol compound. In some embodiments, the molar ratio of 4-methyl chlorobenzyl to trishydroxymethyl aminomethane is (1.1-1.15):1.

[0033] In some embodiments, the temperature of the heating reflux reaction is 80-85℃, and the reaction time is 1-2.5h.

[0034] In some embodiments, the preparation method of the phosphorus tailings acidolysis gypsum includes the following steps: mixing phosphorus tailings and sulfuric acid, heating to 85℃, reacting for 2h, and obtaining the phosphorus tailings acidolysis gypsum by suction filtration, and the molar ratio of phosphorus tailings to sulfuric acid is 1:(1.1-1.15).

[0035] In the second aspect, the embodiments of the present application provide an application of white gypsum in plastics, the white gypsum is prepared by the above method, and the white gypsum is modified by a silane coupling agent and applied to filling of semi-crystalline thermoplastic or thermoplastic biodegradable plastics.

[0036] Some specific embodiments are listed below, and it should be noted that the embodiments described below are exemplary and are used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not specified in the embodiments, the technology or condition described in the literature in the art or according to the product manual is used. If the reagent or instrument is not specified by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0037] I. Preparation method The polyol compound used in each of the following examples and comparative examples was prepared by the following steps: 0.11 mol of 4-methyl chlorobenzyl and 0.1 mol of trimethylol aminomethane were dissolved in 100 ml of ethanol solution, 0.11 mol of Na2CO3 was added, heated to 85°C, and refluxed for 2.5 hours. After cooling to room temperature, the ethanol was removed by vacuum distillation under a pressure of 20 kPa, and the residue was washed with water and dried at 60°C to obtain the polyol compound (N-(4-methylbenzyl) trimethylol aminomethane).

[0038] The phosphorus tailings acid-decomposed gypsum used in each of the following examples and comparative examples was prepared by the following steps: The phosphorus tailings acid-decomposed gypsum was prepared by mixing phosphorus tailings with 60% by mass sulfuric acid, heating to 85°C, and reacting for 2 hours. The phosphorus tailings acid-decomposed gypsum was obtained by suction filtration, with a molar ratio of phosphorus tailings to sulfuric acid of 1:1.1.

[0039] Example 1 A method for deep purification of phosphorus tailings acid-decomposed gypsum, comprising the following steps: S1, a 20% by mass sulfuric acid solution was prepared, and the sulfuric acid solution was mixed with the phosphorus tailings acid-decomposed gypsum, with a mass ratio of phosphorus tailings acid-decomposed gypsum to sulfuric acid solution of 1:2. The mixture was stirred at 60°C for 45 minutes, and then suction filtration was performed after the reaction was stopped to obtain recrystallized gypsum and a filtrate. The filtrate was reused in the recrystallization reaction process. S2, the recrystallized gypsum was mixed with water to prepare a 25% by mass ore slurry, and 1% by mass octylphenyl ether and 0.1% by mass polyol compound were added as flotation agents. The pH was adjusted to 1 using sulfuric acid, and air flotation was performed at room temperature (25°C) until the foam was white. The organic matter in the foam tank and the gypsum concentrate slurry in the tank were obtained, and the gypsum concentrate slurry was suction filtered to obtain the gypsum concentrate and a flotation filtrate. The flotation filtrate was reused in the reverse flotation process.

[0040] Example 2 An application of white gypsum, comprising the following steps: The gypsum concentrate obtained in Example 1 was dried to obtain white gypsum. A certain amount of white gypsum was weighed, and 2% by mass of silane coupling agent KH-550 was added. The mixture was treated in a high-speed mixer at 80°C for 20 minutes, and then PP plastic was added. The mass ratio of white gypsum to PP was 3:7, and 0.1% by mass of antioxidant 1010 (tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester) and 0.2% by mass of zinc stearate were added. The temperature was raised to 100°C for 20 minutes, and then the temperature was lowered to room temperature for setting. White gypsum-filled PP plastic was obtained.

[0041] Example 3 An application of white gypsum, comprising the following steps: The white gypsum prepared in Example 1 is dried, a certain amount of the dried white gypsum is weighed, 2% of silane coupling agent KH-550 by mass of the white gypsum is added thereto, and the mixture is treated in a high-speed mixer at 80 DEG C for 20 minutes; then PBAT plastic is added, the mass ratio of the white gypsum to the PBAT is 1:4, 0.1% of antioxidant 1010 by mass of the PBAT and 0.2% of zinc stearate by mass of the PP are added, the temperature is raised to 100 DEG C for 20 minutes, and the temperature is lowered to room temperature for setting to obtain white gypsum-filled PBAT.

[0042] Example 4 A method for deep purification of phosphorite tailing acidolysis gypsum, comprising the following steps: S1, a 25% sulfuric acid solution by mass percentage is prepared, the sulfuric acid solution is mixed with phosphorite tailing acidolysis gypsum, the mass ratio of the phosphorite tailing acidolysis gypsum to the sulfuric acid solution is 1:3, the mixture is stirred and reacted at 75 DEG C for 20 minutes, the reaction is stopped, and the recrystallized gypsum and the filtrate are obtained by filtration, and the filtrate is reused in the recrystallization reaction process; S2, the recrystallized gypsum is mixed with water to prepare a slurry with a mass percentage of 28wt%, 1wt% of nonylphenol polyoxyethylene ether and 0.5wt% of a polyol compound are added to the slurry as flotation reagents, the pH is adjusted to 5 by using sulfuric acid, and air-flotation is carried out at room temperature (25 DEG C) until the foam is white, the organic matter in the foam tank and the slurry of the gypsum concentrate in the tank are obtained, the slurry of the gypsum concentrate is filtered to obtain the gypsum concentrate and the flotation filtrate, and the flotation filtrate is reused in the reverse flotation process.

[0043] Example 5 An application of white gypsum, comprising the following steps: The gypsum concentrate prepared in Example 4 is dried to obtain white gypsum, a certain amount of the white gypsum is weighed, 2.5% of silane coupling agent KH-550 by mass of the white gypsum is added thereto, and the mixture is treated in a high-speed mixer at 90 DEG C for 15 minutes; then PP plastic is added, the mass ratio of the white gypsum to the PP is 1:3, 0.1% of antioxidant 1010 by mass of the PP and 0.2% of zinc stearate by mass of the PP are added, the temperature is raised to 100 DEG C for 20 minutes, and the temperature is lowered to room temperature for setting to obtain white gypsum-filled PP plastic.

[0044] Example 6 An application of white gypsum, comprising the following steps: The white gypsum prepared in Example 4 is dried, a certain amount of the dried white gypsum is weighed, 3% of silane coupling agent KH-550 by mass of the white gypsum is added, and the mixture is treated in a high-speed mixer at 90°C for 20 minutes. Then, PBAT plastic is added, the mass ratio of the white gypsum to the PBAT is 3:7, 0.1% of antioxidant 1010 by mass of the PBAT is added, and 0.2% of zinc stearate by mass of the PP is added. The temperature is raised to 100°C for 20 minutes, and then the temperature is lowered to room temperature for setting to obtain white gypsum-filled PBAT.

[0045] Example 7 S1, a 40% sulfuric acid solution by mass percentage is prepared, the sulfuric acid solution is mixed with the acidulated gypsum from the phosphorite tailings, the mass ratio of the acidulated gypsum to the sulfuric acid solution is 1:1.5, and the mixture is stirred and reacted at 80°C for 100 minutes. After the reaction is stopped, the recrystallized gypsum and the filtrate are obtained by filtration, and the filtrate is reused in the recrystallization reaction process. S2, the recrystallized gypsum is mixed with water to prepare a slurry with a mass percentage of 27wt%, 5wt% of nonylphenol polyoxyethylene ether phosphate and 0.1wt% of a polyol compound are added as flotation reagents, the pH is adjusted to 1 using sulfuric acid, and air flotation is carried out at room temperature (25°C) until the foam is white. The organic matter in the foam tank and the slurry of the gypsum concentrate in the tank are obtained, the slurry of the gypsum concentrate is filtered to obtain the gypsum concentrate and the flotation filtrate, and the flotation filtrate is reused in the reverse flotation process.

[0046] Example 8 An application of white gypsum, comprising the following steps: The gypsum concentrate prepared in Example 7 is dried to obtain white gypsum, a certain amount of the white gypsum is weighed, 3% of silane coupling agent KH-550 by mass of the white gypsum is added, and the mixture is treated in a high-speed mixer at 100°C for 15 minutes. Then, PP plastic is added, the mass ratio of the white gypsum to the PP is 1:3, 0.1% of antioxidant 1010 by mass of the PP is added, and 0.2% of zinc stearate by mass of the PP is added. The temperature is raised to 100°C for 30 minutes, and then the temperature is lowered to room temperature for setting to obtain white gypsum-filled PP plastic.

[0047] Example 9 An application of white gypsum, comprising the following steps: The white gypsum prepared in Example 7 is dried, a certain amount of the dried white gypsum is weighed, 3% of silane coupling agent KH-550 by mass of the white gypsum is added, and the mixture is treated in a high-speed mixer at 100°C for 15 minutes. Then, PBAT plastic is added, the mass ratio of the white gypsum to the PBAT is 3:7, 0.1% of antioxidant 1010 by mass of the PBAT is added, and 0.2% of zinc stearate by mass of the PP is added. The temperature is raised to 100°C for 30 minutes, and then the temperature is lowered to room temperature for setting to obtain white gypsum-filled PBAT.

[0048] II. Test method 1. White gypsum whiteness detection method: according to standard ISO 2470 for testing.

[0049] 2. Plastic density detection method: according to standard ISO 1183-1 for testing.

[0050] 3. Plastic melt index detection method: according to standard ISO 1133-1 for testing. 4. Plastic strength detection method: according to standard ISO 527-1 / 2 for testing.

[0051] III. Analysis of test results of each embodiment and comparative example (1) The whiteness of the phosphorus tailings acidolysis gypsum, the white gypsum prepared in Example 1, Example 4 and Example 7 was detected, and the detection data is shown in Table 1.

[0052] Table 1 White gypsum whiteness detection data

[0053] As can be seen from Table 1, the white gypsum obtained by further processing the phosphorus tailings acidolysis gypsum through recrystallization and reverse flotation has a significantly improved whiteness.

[0054] (2) The performance indicators of the PP plastic prepared from the phosphorus tailings acidolysis gypsum, Example 2, Example 5 and Example 8 were detected, and the detection data is shown in Table 2.

[0055] Table 2 Performance indicators detection data of gypsum filled in PP

[0056] The performance indicators of the PBAT plastic prepared from the phosphorus tailings acidolysis gypsum, Example 3, Example 6 and Example 9 were detected, and the detection data is shown in Table 3.

[0057] Table 3 Performance indicators detection data of gypsum filled in PBAT

[0058] As can be seen from Table 2 and Table 3, the gypsum obtained by acidolysis of the phosphorus tailings is further purified in depth, and after surface modification, it is used as a filler for plastics, and is blended with semi-crystalline thermoplastic (PP) and thermoplastic biodegradable plastic (PBAT) respectively, and the related plastic products have higher tensile strength, elongation at break, impact strength and tear performance than the use requirements. The method for deep purification of the phosphorus tailings acidolysis gypsum in the present application improves the whiteness of the gypsum, and the gypsum is used as a filler, realizing high value utilization of the phosphorus tailings.

[0059] (3) The particle size of the white gypsum prepared in Example 1, Example 4 and Example 7 was detected, and the results were as follows: Figures 2-4 As can be seen from the figure, the white gypsum prepared by the method of the present application has a particle size of 3-6 μm, which is small and suitable for being used as a filler for paper or plastic.

[0060] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other modes constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for deep purification of acidulated phosphogypsum from phosphorus tailings, characterized by, The method comprises the following steps: S1, mixing and reacting phosphorus tailing acidolysis gypsum with a sulfuric acid solution, and after the reaction is completed, recrystallized gypsum is obtained by filtration; S2, after the recrystallized gypsum is mixed with water to form an ore slurry, the pH of the ore slurry is adjusted to 1-5, a flotation agent is added for reverse flotation to remove organic matter, and after filtration, a gypsum concentrate is obtained, and the gypsum concentrate is dried to obtain white gypsum; The flotation agent comprises an alkyl phenol ether compound and a polyol compound; The polyol compound is obtained by reacting 4-methyl chlorobenzyl and tris-hydroxymethyl aminomethane.

2. The method for deep purification of acidulated phosphosilicate gypsum according to claim 1, characterized in that, In step S1, the concentration of the sulfuric acid solution is 20-40wt%, the reaction temperature is 60-80℃, and the reaction time is 20-100min.

3. The method for deep purification of acidulated phosphoric rock tailings gypsum according to claim 1, characterized by the fact that, The mass ratio of the phosphorus tailing acidolysis gypsum to the sulfuric acid solution is 1:(1.5-3.0).

4. The method for deep purification of acidulated phosphoric rock tailings gypsum according to claim 1, characterized by the fact that, In step S2, the concentration of the recrystallized gypsum in the ore slurry is 25-28wt%, the mass percentage of the alkyl phenol ether compound in the ore slurry is 1-5wt%, and the mass percentage of the polyol compound in the ore slurry is 0.1-0.5wt%.

5. The method for deep purification of acidulated phosphoric rock tailings gypsum according to claim 1, characterized by the fact that, The alkyl phenol ether compound comprises at least one of octyl phenol ether, nonyl phenol polyoxyethylene ether, and nonyl phenol polyoxyethylene ether phosphate.

6. The method for deep purification of acidulated phosphosilicate gypsum according to claim 1, characterized in that, The preparation method of the polyol compound comprises the following steps: 4-methyl chlorobenzyl and tris-hydroxymethyl aminomethane are dispersed in ethanol, sodium carbonate is added, after heating and refluxing, ethanol is removed by distillation under reduced pressure, and the residue is washed and dried to obtain the polyol compound.

7. The method for deep purification of acidulated phosphosilicate gypsum according to claim 6, characterized in that, The molar ratio of the 4-methyl chlorobenzyl to the tris-hydroxymethyl aminomethane is (1.1-1.15):

1.

8. The method for deep purification of acidulated phosphosilicate gypsum according to claim 6, characterized in that, The heating and refluxing reaction is carried out at a temperature of 80-85℃ for 1-2.5h.

9. The method for deep purification of acidulated phosphosilicate gypsum according to claim 1, characterized in that, The preparation method of the phosphorus tailing acidolysis gypsum comprises the following steps: after phosphorus tailing and sulfuric acid are mixed, heating is carried out to 85℃, and the reaction is carried out for 2h, and the phosphorus tailing acidolysis gypsum is obtained by filtration, and the molar ratio of the phosphorus tailing to the sulfuric acid is 1:(1.1-1.15).

10. Use of white anhydrite in plastics, characterized in that, The white gypsum prepared by the method of any one of claims 1-8 is modified by using a silane coupling agent, and is applied to filling of semi-crystalline thermoplastic plastics or thermoplastic biodegradable plastics.

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