Method for decoloring and whitening phosphogypsum

Abstract

The present disclosure belongs to the field of phosphogypsum treatment and resource utilization, and particularly relates to a method for decolorizing and whitening phosphogypsum. The method for decolorizing and whitening phosphogypsum provided by the present disclosure removes organic matter from phosphogypsum by reverse flotation using a decolorizing collector, then precipitates soluble phosphorus and fluorine by adjusting pH, and separates insoluble phosphorus and fluorine precipitates, undecomposed phosphate rock and quartz by two cyclone grading, thereby obtaining phosphogypsum CaSO4·2H2O with high content and good whiteness. The decolorizing collector of the present disclosure mainly consists of diesel oil, a foaming agent and naphthenic acid soap. The diesel oil makes the ore slurry hydrophobic, while the naphthenic acid soap contains a polar carboxylic acid group at one end and a cycloalkane group connected to a methylene group at the other end, which has very strong hydrophobicity and strong adsorption to charged slime and fine particles of carbon in the decolorizing process. Meanwhile, the decolorizing collector also contains a foaming agent, which provides a large amount of stable foam during reverse flotation, thereby achieving better decolorizing and desliming effects.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the field of phosphogypsum treatment and resource utilization, and particularly relates to a method for decolorizing and whitening phosphogypsum. BACKGROUND

[0002] Phosphogypsum refers to a solid waste residue produced by treating phosphorite with sulfuric acid in the production of phosphoric acid, and the main component is calcium sulfate dihydrate. In the production of phosphoric acid, phosphorite, phosphates and fluorides that are not completely filtered, or additives used in the production process, all of which will make phosphogypsum contain various impurities such as phosphorus and fluorine; and the presence of these impurities affects the performance of phosphogypsum, so that it cannot be directly applied to the production of gypsum building materials, thereby restricting the use of phosphogypsum.

[0003] Phosphogypsum impurities are divided into two categories: (1) insoluble impurities: such as quartz, un-decomposed apatite, insoluble P2O5, eutectic P2O5, fluorides, and phosphates and sulfates of fluorine, aluminum and magnesium; (2) soluble impurities: such as water-soluble P2O5, fluorides and sulfates with low solubility.

[0004] At present, a large amount of research on the application of phosphogypsum has been carried out in China, and certain achievements have been made. Flotation is a technology for separating minerals at the gas-liquid-solid three-phase interface, and flotation is a relatively suitable and efficient method for separating phosphogypsum. At present, the main methods for treating phosphogypsum include multiple water washing, reverse selection first and then positive selection, but the effect of phosphogypsum treatment is not ideal. SUMMARY

[0005] Therefore, the purpose of the present disclosure is to provide a method for decolorizing and whitening phosphogypsum, which removes organic matter, soluble phosphorus, fluorine, silicates and the like in phosphogypsum to meet the requirements of industrial gypsum. The method is simple in process, high in purification efficiency of phosphogypsum, low in cost and easy to industrialize.

[0006] To achieve the above purpose, the present disclosure provides the following technical solutions:

[0007] A method for decolorizing and whitening phosphogypsum, comprising the following steps:

[0008] S1: slurry the phosphogypsum raw ore, add sulfuric acid to adjust the pH to below 2, add a decolorizing collector, aerate, and perform reverse flotation to float out the organic matter slurry, and the remaining slurry is denoted as the first phosphogypsum slurry;

[0009] The decolorizing collector comprises diesel oil, naphthenic acid soap and a foaming agent.

[0010] S2: Add lime to the first phosphogypsum slurry from step S1 to adjust the pH to above 11, and then pass it sequentially into the first hydrocyclone separator and the second hydrocyclone separator; the first hydrocyclone separator overflows to separate fine particulate slurry, the particle size of the fine particulate slurry is less than 20μm, the second hydrocyclone separator overflows to release the second phosphogypsum slurry, and the bottom flow of the second hydrocyclone separator is a quartz mixture;

[0011] S3: The second phosphogypsum slurry from step S2 is subjected to sedimentation, concentration, pressure filtration, and drying to obtain phosphogypsum.

[0012] The decolorizing collector of phosphogypsum disclosed herein is produced by compounding different industrial-grade raw materials, mainly composed of diesel oil, a foaming agent, and naphthenic acid soap. Diesel oil primarily hydrophobizes the slurry, while naphthenic acid soap, due to its unique molecular structure, contains a polar carboxylic acid group at one end and a cycloalkyl group linked to a methylene group at the other, exhibiting strong hydrophobicity. During the decolorization process, it strongly adsorbs charged sludge and fine carbon particles. Simultaneously, a foaming agent is added to the decolorizing collector, providing a large amount of stable foam during reverse flotation aeration, thus improving the decolorization and desliming effects. Conventional decolorizing collectors, mainly mineral oil-based substances, only hydrophobize the slurry during decolorization and desliming, then separate fine sludge and carbon particles under aeration. Compared to conventional decolorizing collectors, the decolorizing collector disclosed herein has a significant advantage in decolorization and desliming effects.

[0013] In the phosphogypsum decolorization and whitening method disclosed herein, organic matter is first removed by reverse flotation, and then the pH of the first phosphogypsum slurry is adjusted to above 11, causing the water-soluble phosphorus and fluorine in the first phosphogypsum slurry to be converted into fine-particle calcium phosphate, calcium fluoride, and other insoluble substances. Because these insoluble substances have relatively fine particles, with a particle size below 20 μm, the phosphogypsum particle size is between 20-60 μm, and the quartz particles have a particle size above 74 μm. Therefore, based on the difference in particle size, the cyclone separation effect of the first and second cyclone separators separates the insoluble substances such as calcium phosphate and calcium fluoride, phosphogypsum, and quartz. In the first phosphogypsum slurry, the residual decolorizing collector plays a positive role in separating the insoluble substances. The residual foaming agent will generate a certain amount of bubbles under the action of cyclone, and the residual diesel oil (non-polar oil) will reduce the interaction force between the slurry particles, which can more quickly separate the insoluble substances such as calcium phosphate and calcium fluoride with a particle size of less than 20 μm, as well as the mixture of phosphogypsum and quartz.

[0014] Compared with other phosphogypsum flotation processes, the phosphogypsum decolorization and whitening method disclosed herein directly utilizes the decolorizing collector to perform reverse flotation on the phosphogypsum. Then, soluble phosphorus and fluorine are settled as insoluble substances using chemical precipitation. After two cyclone classifications, the insoluble phosphorus and fluorine precipitates, undecomposed phosphate rock, and quartz are separated. The phosphogypsum decolorization and whitening method disclosed herein uses less reagent and yields phosphogypsum with high CaSO4·2H2O content and good whiteness.

[0015] In one embodiment, in step S1, the whiteness of the phosphogypsum ore is 15%-25%. More preferably, the whiteness of the phosphogypsum ore is 20%-25%.

[0016] In one scheme, in step S1, the mass concentration of the slurry after conditioning the phosphogypsum ore is 30 wt%.

[0017] In one scheme, in step S1, the added sulfuric acid has a mass concentration of 20-40 wt%.

[0018] In one embodiment, in step S1, the amount of sulfuric acid added is 1.4-2.08 kg / t of raw ore.

[0019] In one embodiment, in step S1, the amount of the decolorizing collector added is 0.2-0.4 kg / t of raw ore.

[0020] In one embodiment, the mass ratio of diesel oil, naphthenic acid soap, and foaming agent in the decolorizing collector is 1:7:2.

[0021] In one embodiment, the foaming agent comprises a nonionic surfactant.

[0022] In one embodiment, the nonionic surfactant includes a polyoxyethylene nonionic surfactant, wherein the polyoxyethylene nonionic surfactant is one or more of long-chain fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine, and polyoxyethylene alkylamide.

[0023] In one scheme, in step S1, the inflation volume is 80m³. 3 / h.

[0024] In one scheme, in step S1, after the organic slurry is floated out, the organic slurry is settled, concentrated, and filtered to obtain solid organic matter.

[0025] In one embodiment, in step S2, the added quicklime is industrial calcium oxide with a calcium oxide content ≥90 wt%.

[0026] In one scheme, the amount of lime added is 4.2-6.67 kg / t of raw ore.

[0027] In one embodiment, in step S2, the first cyclone separator is an LZFX50 cyclone separator and the second cyclone separator is an LZFX100 cyclone separator; both the LZFX50 cyclone separator and the LZFX100 cyclone separator are developed and manufactured by Oasis Mineral Processing Equipment Manufacturing Co., Ltd.

[0028] In one embodiment, in step S3, the drying temperature is 45°C.

[0029] The beneficial effects of this disclosure are:

[0030] This method, through reverse flotation decolorization, lime neutralization and sedimentation, and cyclone classification, can recover and reuse phosphogypsum ore with a whiteness of approximately 20%. It achieves high purity and effectively removes water-soluble phosphorus and fluoride from the ore. The final phosphogypsum product meets the following requirements: CaSO4·2H2O content ≥90wt%, water-soluble phosphorus pentoxide (P2O5) ≤0.20wt%, and water-soluble fluoride ion content (F...). - The requirement of ≤0.10wt% was met, and the different components in the phosphogypsum ore were separated, which is more conducive to preparation for recycling.

[0031] Compared to existing technologies, current methods for treating phosphogypsum mainly involve multiple water washings and a process of reverse and forward flotation. In contrast, the flotation reagents used in this scheme (i.e., the decolorizing collector) are partially derived from industrial waste, and separation is achieved through lime neutralization and sedimentation. This method requires less reagent and results in lower treatment costs. Further defluorination through sedimentation and cyclone classification after phosphorus treatment yields phosphogypsum with high whiteness. This scheme avoids generating large amounts of wastewater through water washing and the use of expensive cationic decolorizing collectors. Detailed Implementation

[0032] In the following embodiments or comparative examples:

[0033] The sulfuric acid used had a mass concentration of 20 wt%.

[0034] The amount of sulfuric acid added is 1.4 kg / t of raw ore.

[0035] The decolorizing collector used includes diesel oil, naphthenic acid soap, and a foaming agent; wherein the ratio of diesel oil, naphthenic acid soap, and foaming agent is 1:7:2. The foaming agent is OP-10. This decolorizing collector is designated as decolorizing collector ZC-1.

[0036] The added quicklime is industrial calcium oxide with a calcium oxide content ≥90wt%; the amount of quicklime added is 6.67kg / t of raw ore.

[0037] Both the LZFX50 and LZFX100 hydrocyclones are developed and manufactured by Oasis Mineral Processing Equipment Manufacturing Co., Ltd.

[0038] Example 1

[0039] This embodiment describes the decolorization and whitening of phosphogypsum ore from Yichang, Hubei Province. The phosphogypsum ore contains 88.43 wt% CaSO4·2H2O, has a whiteness of 22.16%, and contains 3.68 wt% SiO2.

[0040] This embodiment of a method for decolorizing and whitening phosphogypsum includes the following steps:

[0041] S1: Prepare the phosphogypsum ore slurry to a concentration of 30 wt% in a flotation cell. Stir at 1860 rpm to ensure thorough dispersion of the phosphogypsum ore in the water. Add 20 wt% dilute sulfuric acid to adjust the pH to below 2, stir for 2 minutes, then add 0.3 kg / t of decolorizing collector ZC-1. After the reagent is fully dispersed, aerate the solution at an aeration rate of 80 m³ / t. 3 / h, reverse flotation is performed, and the organic slurry that has been floated out is settled, concentrated, and filtered to obtain solid organic matter; the slurry remaining in the flotation cell is recorded as the first phosphogypsum slurry.

[0042] S2: Lime is added to the first phosphogypsum slurry to raise the pH above 11, converting the water-soluble fluorine and phosphorus in the first phosphogypsum slurry into insoluble substances such as calcium phosphate and calcium fluoride. The reacted slurry is then sequentially fed into LZFX50 and LZFX100 hydrocyclones. The overflow from LZFX50 separates insoluble substances such as calcium phosphate and calcium fluoride with a particle size of less than 20 μm, the overflow from LZFX100 separates the second phosphogypsum slurry, and the bottom flow from LZFX100 separates a quartz mixture.

[0043] S3: The second phosphogypsum slurry was settled, concentrated, filtered under pressure, and dried at 45°C to obtain phosphogypsum. The phosphogypsum contained 95.23 wt% CaSO4·2H2O, 0.55 wt% SiO2, and had a yield of 77.77 wt% and a whiteness of 84.94%.

[0044] Example 2

[0045] This embodiment describes the decolorization and whitening of phosphogypsum ore from Yichang, Hubei Province. The phosphogypsum ore contains 88.43 wt% CaSO4·2H2O, has a whiteness of 22.16%, and contains 3.68 wt% SiO2.

[0046] This embodiment of a method for decolorizing and whitening phosphogypsum includes the following steps:

[0047] S1: Prepare the phosphogypsum ore slurry to a concentration of 30 wt% in a flotation cell. Stir at 1860 rpm to ensure thorough dispersion of the phosphogypsum ore in the water. Add 20 wt% dilute sulfuric acid to adjust the pH to below 2, stir for 2 minutes, then add 0.2 kg / t of decolorizing collector ZC-1. After the reagent is fully dispersed, aerate the solution at an aeration rate of 80 m³ / t. 3 / h, reverse flotation is performed, and the organic slurry that has been floated out is settled, concentrated, and filtered to obtain solid organic matter; the slurry remaining in the flotation cell is recorded as the first phosphogypsum slurry.

[0048] S2: Lime is added to the first phosphogypsum slurry to raise the pH above 11, converting the water-soluble fluorine and phosphorus in the first phosphogypsum slurry into insoluble substances such as calcium phosphate and calcium fluoride. The reacted slurry is then sequentially fed into LZFX50 and LZFX100 hydrocyclones. The overflow from LZFX50 separates insoluble substances such as calcium phosphate and calcium fluoride with a particle size of less than 20 μm, the overflow from LZFX100 separates the second phosphogypsum slurry, and the bottom flow from LZFX100 separates a quartz mixture.

[0049] S3: The second phosphogypsum slurry was settled, concentrated, filtered, and dried at 45°C to obtain dihydrate gypsum. The phosphogypsum contained 94.51 wt% CaSO4·2H2O and 0.62 wt% SiO2. The yield of phosphogypsum was 78.67 wt%, and the whiteness of phosphogypsum was 81.48%.

[0050] Example 3

[0051] This embodiment describes the decolorization and whitening of phosphogypsum ore from Yichang, Hubei Province. The phosphogypsum ore contains 88.43 wt% CaSO4·2H2O, has a whiteness of 22.16%, and contains 3.68 wt% SiO2.

[0052] This embodiment of a method for decolorizing and whitening phosphogypsum includes the following steps:

[0053] S1: Prepare the phosphogypsum ore slurry to a concentration of 30 wt% in a flotation cell. Stir at 1860 rpm to ensure thorough dispersion of the phosphogypsum ore in the water. Add 20 wt% dilute sulfuric acid to adjust the pH to below 2, stir for 2 minutes, then add 0.4 kg / t of decolorizing collector ZC-1. After the reagent is fully dispersed, aerate the solution at an aeration rate of 80 m³ / t. 3 / h, reverse flotation is performed, and the organic slurry that has been floated out is settled, concentrated, and filtered to obtain solid organic matter; the slurry remaining in the flotation cell is recorded as the first phosphogypsum slurry.

[0054] S2: Lime is added to the first phosphogypsum slurry to raise the pH to above 11, converting the water-soluble fluorine and phosphorus in the first phosphogypsum slurry into insoluble substances such as calcium phosphate and calcium fluoride. The reacted slurry is then sequentially fed into LZFX50 and LZFX100 hydrocyclones. The overflow from LZFX50 separates insoluble substances such as calcium phosphate and calcium fluoride with a particle size of less than 20 μm, while the overflow from LZFX100 is the second phosphogypsum slurry, and the bottom flow from LZFX100 is a quartz mixture.

[0055] S3: The second phosphogypsum slurry was settled, concentrated, filtered, and dried at 45°C to obtain dihydrate gypsum. The phosphogypsum contained 95.53 wt% CaSO4·2H2O and 0.53 wt% SiO2. The phosphogypsum yield was 76.34 wt%, and the whiteness of the phosphogypsum was 84.86%.

[0056] Comparative Example 1

[0057] This comparative example demonstrates the decolorization and whitening of phosphogypsum ore from Yichang, Hubei Province. The phosphogypsum ore contains 88.43 wt% CaSO4·2H2O, has a whiteness of 22.16%, and contains 3.68 wt% SiO2.

[0058] This comparative example describes a method for decolorizing and whitening phosphogypsum, comprising the following steps:

[0059] S1: Prepare the phosphogypsum ore slurry to a concentration of 30 wt% in a flotation cell. Stir at 1860 rpm to ensure thorough dispersion of the phosphogypsum ore in the water. Add 20 wt% dilute sulfuric acid to adjust the pH to below 2, stir for 2 minutes, then add 0.3 kg / t of decolorizing collector ZC-1. After the reagent is fully dispersed, aerate the solution at an aeration rate of 80 m³ / t. 3 / h, flotation is carried out, and the organic slurry obtained by flotation is settled, concentrated and filtered to obtain solid organic matter; the slurry remaining in the flotation cell is recorded as the first phosphogypsum slurry.

[0060] S2: Lime is added to the first phosphogypsum slurry to raise the pH to above 11, converting the water-soluble fluorine and phosphorus in the slurry into insoluble substances such as calcium phosphate and calcium fluoride. The reacted slurry is then fed into an LZFX100 hydrocyclone separator. The overflow from the LZFX100 separates the insoluble substances such as calcium phosphate and calcium fluoride with a particle size of less than 20 μm from the phosphogypsum slurry mixture, while the bottom flow from the LZFX100 contains a quartz mixture.

[0061] S3: The mixture of insoluble substances with a particle size of less than 20 μm, such as overflowing calcium phosphate and calcium fluoride, and phosphogypsum slurry was settled, concentrated, filtered under pressure, and dried at 45 °C to obtain dihydrate gypsum. The phosphogypsum contained 93.42 wt% CaSO4·2H2O, 0.68 wt% SiO2, and had a yield of 80.36 wt% and a whiteness of 78.34%.

[0062] Comparative Example 2

[0063] This comparative example demonstrates the decolorization and whitening of phosphogypsum ore from Yichang, Hubei Province. The phosphogypsum ore contains 88.43 wt% CaSO4·2H2O, has a whiteness of 22.16%, and contains 3.68 wt% SiO2.

[0064] This comparative example describes a method for decolorizing and whitening phosphogypsum, comprising the following steps:

[0065] S1: Prepare the phosphogypsum ore slurry to a concentration of 30 wt% in a flotation cell. Stir at 1860 rpm to ensure thorough dispersion of the phosphogypsum ore in the water. Add 20 wt% dilute sulfuric acid to adjust the pH to below 2, stir for 2 minutes, then add 0.3 kg / t of decolorizing collector ZC-1. After the reagent is fully dispersed, aerate at 80 m³ / t. 3 / h, flotation is carried out, and the organic slurry obtained by flotation is settled, concentrated and filtered to obtain solid organic matter; the slurry remaining in the flotation cell is recorded as the first phosphogypsum slurry.

[0066] S2: Lime is added to the first phosphogypsum slurry to raise the pH to above 11, converting the water-soluble fluorine and phosphorus in the slurry into insoluble substances such as calcium phosphate and calcium fluoride with a particle size of less than 20 μm. The reacted slurry is then fed into an LZFX50 hydrocyclone separator. The overflow of the LZFX50 separates the insoluble substances such as calcium phosphate and calcium fluoride with a particle size of less than 20 μm, while the bottom flow of the LZFX50 is a mixture of phosphogypsum and quartz slurry.

[0067] S3: The mixture of phosphogypsum and quartz slurry flowing out from the bottom is settled, concentrated, filtered under pressure, and dried at 45°C to obtain dihydrate gypsum. The phosphogypsum contains 91.56 wt% CaSO4·2H2O, 2.72 wt% SiO2, has a yield of 85.86 wt%, and a whiteness of 65.37%.

[0068] Compared to existing technologies, the phosphogypsum decolorization and whitening method disclosed in this invention can remove organic matter, soluble phosphorus, fluorine, silicates, etc. from phosphogypsum, meeting the requirements of industrial gypsum. This method is simple, highly efficient in purifying phosphogypsum, low in cost, and easily industrialized. The decolorizing collector ZC-1 is produced by compounding different industrial-grade raw materials, mainly composed of diesel oil, a frother, and naphthenic acid soap. Diesel oil primarily hydrophobizes the slurry, while naphthenic acid soap, due to its unique molecular structure, contains a polar carboxylic acid group at one end and a cycloalkyl group linked to a methylene group at the other, exhibiting extremely strong hydrophobicity. During the decolorization process, it has a strong adsorption effect on charged sludge and fine carbon particles. Simultaneously, a certain amount of frother is added to the decolorizing collector, providing a large amount of stable foam during flotation aeration, thus improving the decolorization and desliming effects. Adding lime to the first phosphogypsum slurry adjusts the pH of the phosphogypsum aqueous solution and also causes the water-soluble phosphorus and fluoride in the second phosphogypsum slurry to precipitate as insoluble calcium salts such as calcium phosphate and calcium fluoride. These insoluble calcium salt particles are relatively fine, with a particle size of approximately less than 20 μm, while the phosphogypsum particles are between 20-60 μm, and the quartz particles are larger than 74 μm. Therefore, the insoluble calcium salts, phosphogypsum, and quartz are separated through cyclone separation. The residual decolorizing collector ZC-1 in the slurry plays a positive role in separating the insoluble calcium salts; the residual frother generates bubbles under the action of cyclone, and the residual non-polar oil reduces the interaction forces between slurry particles, enabling faster separation of the insoluble calcium salt particles, phosphogypsum, and quartz mixture.

[0069] The embodiments described above are merely examples of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and this disclosure also intends to include these modifications and variations.

Claims

1. A method for decolorizing and whitening phosphogypsum, characterized by: The method comprises the following steps: S1: slurry the raw phosphogypsum, add sulfuric acid to adjust the pH to below 2, add a decolorizing collector, aerate, and perform reverse flotation to float the organic matter slurry, and the remaining slurry is referred to as the first phosphogypsum slurry; The decolorizing collector comprises diesel oil, naphthenic acid soap, and a foaming agent. S2: add lime to the first phosphogypsum slurry of step S1 to adjust the pH to above 11, wherein the amount of lime added is 4.2-6.67 kg / t of raw ore, and then sequentially pass through a first cyclone separator and a second cyclone separator; the first cyclone separator separates fine particle slurry from the overflow, the fine particles in the fine particle slurry have a particle size of less than 20 μm, and the second cyclone separator overflows the second phosphogypsum slurry and underflows a quartz mixture. S3: perform settling, concentration, pressure filtration, and drying on the second phosphogypsum slurry of step S2 to obtain phosphogypsum.

2. The method for decolorizing and whitening phosphogypsum according to claim 1, characterized in that: In step S1, the raw phosphogypsum has a whiteness of 15%-25%.

3. The method for decolorizing and whitening phosphogypsum according to claim 1, characterized in that: In step S1, the concentration of the slurry after slurry treatment of the raw phosphogypsum is 30 wt%.

4. The method of decolorizing and whitening phosphogypsum according to claim 1, characterized in that: In step S1, the mass concentration of the added sulfuric acid is 20-40 wt%.

5. The method of decolorizing and whitening phosphogypsum according to claim 1, characterized in that: The amount of sulfuric acid added is 1.4-2.08 kg / t of raw ore.

6. The method of decolorizing and whitening phosphogypsum according to claim 1, characterized in that: In step S1, the amount of the decolorizing collector added is 0.2-0.4 kg / t of raw ore.

7. The method of decolorizing and whitening phosphogypsum according to claim 1, characterized in that: In the decolorizing collector, the mass ratio of diesel oil, naphthenic acid soap, and foaming agent is 1:7:

2.

8. The method of decolorizing and whitening phosphogypsum according to claim 1, characterized in that: The foaming agent comprises a non-ionic surfactant.

9. The method of claim 8, wherein the phosphogypsum is decolorized and whitened by the process of claim 8. The non-ionic surfactant comprises a polyoxyethylene non-ionic surfactant, and the polyoxyethylene non-ionic surfactant is one or more of a long-chain fatty alcohol polyoxyethylene ether, an alkyl phenol polyoxyethylene ether, a fatty acid polyoxyethylene ester, a polyoxyethylene alkyl amine, and a polyoxyethylene alkyl amide.

10. The method of decolorizing and whitening phosphogypsum according to claim 1, characterized in that: In step S1, the inflation amount at the time of inflation is 80 m 3 / h.

11. The method of decolorizing and whitening phosphogypsum according to claim 1, characterized in that: In step S1, after the organic matter slurry is floated, the organic matter slurry is subjected to settling, concentration, and pressure filtration to obtain solid organic matter.

12. The method of whitening of phosphogypsum according to claim 1, characterized in that: In step S2, the added quicklime is industrial calcium oxide, and the calcium oxide content is ≥90 wt%.

13. The method of whitening of phosphogypsum according to claim 1, characterized in that: In step S2, the first cyclone separator is an LZFX50 cyclone separator, and the second cyclone separator is an LZFX100 cyclone separator; both the LZFX50 cyclone separator and the LZFX100 cyclone separator are developed and produced by the Green Oasis Mineral Processing Equipment Manufacturing Co., Ltd.

14. The method of whitening of phosphogypsum according to claim 1, characterized in that: In step S3, the drying temperature during drying is 45°C.