Phosphogypsum ecological restoration material and preparation process thereof

Abstract

This invention discloses a process for preparing ecological restoration materials using phosphogypsum containing organic matter, comprising: adding water to phosphogypsum containing organic matter and stirring to adjust the slurry, washing with water until the pH of the slurry is greater than 6; placing the slurry in a flotation cell, adding a frother and an organic amine collector for flotation until the foam changes from black to grayish-white, obtaining a concentrate slurry and foam; washing the concentrate slurry a second time with water 2-3 times until the pH of the concentrate slurry is 6.5-7.5; after dewatering the concentrate slurry, adding a modifier and stirring to adjust its pH to 8-9, and dewatering again to obtain the phosphogypsum ecological restoration material. This invention weakens the acidity of the slurry through water washing, and then uses a frother and a collector for flotation, effectively improving the removal of organic matter by flotation and reducing the interference of organic matter on the removal of other harmful substances; the second water washing effectively removes soluble harmful substances; the combination of organic amine collector and frother as flotation reagents results in excellent organic matter removal.

Description

Technical Field

[0001] This invention belongs to the technical field of harmless treatment and comprehensive utilization of phosphogypsum, and more specifically, relates to an ecological restoration material of phosphogypsum and its preparation process. Background Technology

[0002] Phosphogypsum is a solid byproduct generated during the wet process of phosphoric acid production. For every ton of phosphoric acid produced, 4-5 tons of phosphogypsum are generated. As of 2023, my country's stockpile of phosphogypsum was approximately 870 million tons, with an annual increase of about 80 million tons. Although the utilization rate of phosphogypsum has been increasing year by year, the consumption is still limited. At present, it is still disposed of by stockpiling, resulting in a waste of land resources.

[0003] Because phosphogypsum contains various impurities such as phosphates, fluorides, organic matter, copper, zinc, lead, and chromium, it enters the soil and groundwater through natural rainfall and leaching, posing a serious pollution risk to the environment. Therefore, harmless treatment of phosphogypsum, improving its material properties, reducing environmental pollution risks, and using it for mine ecological restoration can not only solve the problems of high storage pressure and difficulties in commercial utilization of phosphogypsum, but also replace materials such as soil, sand, and stone to reduce mine restoration costs. This is of great practical significance for the sustainable and healthy development of the phosphate chemical industry.

[0004] Existing technologies for the harmless treatment of phosphogypsum have limited effectiveness in removing characteristic pollutants contained in phosphogypsum and cannot meet the requirements for mine ecological restoration materials.

[0005] Currently, most domestic processes for treating phosphogypsum as a mine ecological restoration material primarily involve adding curing agents. Chinese invention patent application CN 115611602A discloses a phosphogypsum-containing mine filling and ecological restoration material and its preparation method. By adding a certain proportion of fluoride-fixing agents, heavy metal curing agents, and activators, it can effectively fix phosphates, fluorides, and heavy metals. However, it does not explain the effect on organic matter removal, and the long-term effectiveness of the added curing agents remains uncertain. Therefore, there is an urgent need for an efficient and stable harmless treatment process for phosphogypsum to prepare phosphogypsum ecological restoration materials that meet the needs of mine ecological restoration.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a phosphogypsum ecological restoration material and its preparation process. The preparation process is simple and efficient, and the resulting product can be directly used for mine ecological restoration.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A process for preparing eco-remediation materials using organic phosphogypsum includes: S1. Add water to the phosphogypsum containing organic matter and stir to form a slurry. Wash the slurry with water until the pH of the slurry is greater than 6. S2. Place the slurry from S1 into a flotation cell, add frother and collector and carry out flotation until the foam changes from black to grayish-white, to obtain concentrate slurry and foam. S3. Wash the concentrate slurry from S2 with water 2-3 times until the pH of the concentrate slurry is 6.5-7.5. S4. After dehydrating the concentrate slurry that has undergone two water washings in S3, add a modifier and adjust its pH to 8-9 by stirring. Then dehydrate to obtain phosphogypsum ecological restoration material.

[0009] In the above technical solution, in step S2, the concentration of the slurry in the flotation cell is 20-25 wt%.

[0010] In the above technical solution, in step S2, the foaming agent is one or more of methyl isobutyl methanol, butyl phthalate, and α-terpene alcohol oil.

[0011] Specifically, in the above technical solution, in step S2, the collector is an organic amine-based collector.

[0012] Preferably, in the above technical solution, in step S2, the collector is dodecylamine and / or coconut oil diamine.

[0013] Specifically, in the above technical solution, in step S2, based on the different hydrophobicities of organic matter, a highly efficient organic amine scavenger and frother are selected through flotation process to remove organic matter from phosphogypsum.

[0014] Furthermore, in the above technical solution, in step S2, corresponding to 1 ton of phosphogypsum containing organic matter, the amount of foaming agent and the amount of collector added are 0.1-0.5 Kg and 0.05-0.5 Kg, respectively.

[0015] In the above technical solution, in step S4, the modifier is at least one of calcium oxide, calcium hydroxide, and carbide slag.

[0016] Specifically, in the above technical solution, in step S4, by adding a modifier, the pH of the concentrate slurry is adjusted on the one hand, and the remaining impurities such as phosphorus and fluorine are fixed on the other hand.

[0017] In the above technical solution, in step S4, the water content of the dehydrated phosphogypsum ecological restoration material is 10-15 wt%.

[0018] Furthermore, in the above technical solution, in step S1, during the stirring and slurry preparation process, the amount of water added is to control the concentration of the slurry after preparation to be 20-25 wt%.

[0019] Furthermore, in the above technical solution, in step S1, the organic matter content in the phosphogypsum containing organic matter is 2-20 wt%.

[0020] Furthermore, the above technical solution also includes adjusting the pH of the overflow from the water washing process in step S1 to 7-9 by adding lime, placing it in a sedimentation tank, allowing it to stand until it becomes clear, separating it, reusing the supernatant obtained from the separation in the water washing process after slurry preparation, and adding the bottom slurry (containing SS) obtained from the separation to the raw material containing organic matter, phosphogypsum.

[0021] Furthermore, the above technical solution also includes the following: after the overflow from the secondary washing in step S3 is subjected to pH adjustment and post-treatment, the resulting supernatant is reused in the secondary washing process of the concentrate slurry.

[0022] In a preferred embodiment, when the concentrate slurry is washed three times, the overflow from the third secondary washing is reused in the second secondary washing process of the concentrate slurry, the overflow from the second secondary washing is reused in the first secondary washing process of the concentrate slurry, and the overflow from the first secondary washing is collected, lime is added to adjust the pH to 7-9, and then after two stages of sand filtration and one stage of ion exchange, the resulting supernatant is reused in the third secondary washing process of the concentrate slurry.

[0023] Specifically, in the above preferred embodiment, the backwashing impurities from the second-stage sand filter are combined and added to the phosphogypsum raw material containing organic matter, and the backwashing liquid from the first-stage ion exchange is treated and discharged into the tailings pond; in addition, fresh water is added as needed during the third secondary water washing process of the concentrate slurry.

[0024] Specifically, in the above technical solution, in step S1, soluble impurities such as phosphorus and fluorine are dissolved in water by washing, while the acidity of the phosphogypsum raw material is weakened, which helps to improve the effect of the frother in the subsequent flotation process.

[0025] In a preferred embodiment of the present invention, step S2 further includes collecting and dehydrating the foam generated during the flotation process to recover and prepare organic fertilizer.

[0026] In a preferred embodiment of the present invention, step S4 further includes adding the filtrate generated during the dehydration process to the phosphogypsum raw material containing organic matter for recycling, forming a closed-loop cycle.

[0027] Specifically, in a specific embodiment of the present invention: First, water is added to the phosphogypsum containing organic matter, and the mixture is stirred to form a slurry. Since the wet-process phosphogypsum contains phosphoric acid and sulfuric acid, the slurry becomes acidic after adding water. Through continuous stirring, soluble impurities (such as soluble phosphorus and soluble fluorine) are fully dissolved under acidic conditions. In addition, small amounts of heavy metals (Cu, As, Cd, Pb, and Cr, etc.) are released as free heavy metal ions through acid leaching. These ions are then washed with water and discharged with the overflow, thus removing water-soluble phosphorus, water-soluble fluorine, and small amounts of heavy metals. Furthermore, washing effectively weakens the acidity of the slurry, which helps improve the effectiveness of flotation reagents. Next, the washed slurry is subjected to flotation, primarily to remove organic matter. A frother is added to the slurry. The principle is that the frother's molecular structure is a heteropolar organic substance, with a polar group at one end and a nonpolar group at the other. The hydrophilic and non-polar gas-loving properties of the foaming agent molecules allow for directional alignment at the air-water interface, significantly reducing interfacial tension and facilitating the formation of more fine bubbles. Adding organic amine scavengers to the slurry allows them to adhere to the mineral surface, primarily through their hydrophobic effect via hydrocarbon groups. This reduces the interaction area between the mineral surface and water molecules, weakens the interaction forces, and enhances surface hydrophobicity, making it easier for organic matter attached to the phosphogypsum surface to float with the bubbles, thus achieving organic matter removal. The concentrate slurry is then subjected to 2-3 secondary water washes until the content of harmful impurities such as fluorine in the concentrate slurry is less than 10 mg / L. After dehydration, a modifier (at least one of calcium oxide, calcium hydroxide, and carbide slag) is added to ensure its pH is between 7 and 9. The main purpose of this is to solidify the remaining phosphorus and fluorine, reducing the total phosphorus and total fluorine in the phosphogypsum leachate.

[0028] The chemical equation for the reaction that occurred is: In another aspect, the present invention provides an ecological restoration material of phosphogypsum prepared using the above-described process.

[0029] Compared with the prior art, the present invention has the following advantages: (1) This invention weakens the acidity of the pulp by washing with water, and then uses frothers and catchers for flotation, which effectively improves the removal effect of organic matter. In addition, the combination of organic amine catchers and frothers as flotation reagents has excellent effect on removing organic matter. (2) The present invention solves the difficulties of removing organic matter and the uncertainty of long-term fixation in the existing technology of adding heavy metal curing agents, fluorine fixation agents and activators. At the same time, it also avoids the problem of unstable pH in the dry neutralization method in the existing technology. (3) The phosphogypsum ecological restoration material prepared by the process provided by the present invention using organic phosphogypsum as raw material can be directly used for mine ecological restoration, avoiding the step of long-term aging and greatly reducing time costs. (4) The overflow liquid from the washing process provided by the present invention can be recycled for the washing process after standing. The foam collected during the flotation process can be used to prepare organic fertilizer after dehydration. The filtrate produced by the final dehydration can be added to the raw material of high organic matter phosphogypsum for recycling. That is, the entire process removes or fixes harmful components in phosphogypsum while minimizing pollutants in organic matter phosphogypsum, so as to consider resource recycling and not cause secondary pollution. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of preparing ecological restoration materials using phosphogypsum containing organic matter in an embodiment of the present invention; Figure 2 This is a process flow diagram of the reuse of the overflow liquid generated during the water washing process in step S1 of the preparation of ecological restoration materials in this embodiment of the invention. Figure 3 This is a process flow diagram of the reuse of the overflow liquid generated by the secondary water washing in step S3 during the preparation of ecological restoration materials in this embodiment of the invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0032] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] In the embodiments, unless otherwise specified, all methods used are conventional methods in the art.

[0034] The terms “comprising,” “including,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0035] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0036] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] In this embodiment of the invention, the methods shown in Table 1 below are used to detect the organic matter-containing phosphogypsum raw materials and the prepared phosphogypsum ecological restoration materials according to the detection methods for total amount of solid waste pollutants and leachate.

[0039] Table 1. Detection methods for total pollutants and leachate in solid waste. ; Example 1 This invention provides a method for preparing eco-remediation materials using phosphogypsum containing organic matter, such as... Figure 1 As shown, the details are as follows: Organic phosphogypsum, a solid waste material from a phosphate plant in Hubei Province, was used as raw material. Its moisture content was found to be 29.2%. At the same time, the concentration of pollutants in the solid waste and the leachate was determined.

[0040] (1) Weigh 1 kg of solid waste phosphogypsum sample (of which, the dry basis phosphogypsum mass is 708 g), add it to a 2 L flotation cell, add 1.5 L of water, stir and adjust the slurry, while scraping the upper layer of liquid with a scraper and continuously adding water to keep the liquid level unchanged, and after washing with water for 30 min, the pH of the slurry is measured to be 6.1. (2) Add 0.22 g of frother (diethyl phthalate) and 0.18 g of organic amine collector (dodecylamine), start flotation, scrape off the foam layer with a scraper until the foam color changes from black to grayish-white, and obtain concentrate slurry and foam; (3) Add water to keep the liquid level unchanged, continue to scrape off the upper liquid with a scraper, wash twice with water for 30 minutes each time, and after 60 minutes, the pH of the slurry was measured to be 7.0; (4) Vacuum filter dewatering of the slurry, add modified carbide slag solid to the dewatered concentrate, stir and measure its pH. The amount of carbide slag added is to control the overall pH to 8-9, and obtain phosphogypsum ecological restoration material with a water content of 10-15 wt%.

[0041] In addition, the foam collected during the flotation process is dehydrated and recycled for the preparation of organic fertilizer.

[0042] Meanwhile, the filtrate collected during the vacuum filtration and dewatering process of the slurry is added to the raw materials of the solid waste phosphogypsum sample for recycling.

[0043] The prepared phosphogypsum ecological restoration material was tested according to the detection methods for total amount of pollutants in solid waste and leachate. The results are shown in Table 2-3 below.

[0044] Table 2. Results of total content detection of characteristic pollutants ; Table 3. Detection results of leachate content of characteristic pollutants ; Example 2 This invention provides a method for preparing eco-remediation materials using phosphogypsum containing organic matter, such as... Figure 1-3 As shown, the details are as follows: Solid waste phosphogypsum (same as in Example 1) from a phosphate plant in Hubei Province was used as raw material. Its moisture content was found to be 29.2%. At the same time, the concentration of pollutants in the solid waste and the leachate was determined according to the total amount of pollutants in the solid waste and the concentration of the leachate.

[0045] (1) Weigh 1 kg of solid waste phosphogypsum sample (of which, the dry basis phosphogypsum mass is 708 g), add it to a 3L flotation cell, add 2.5 L of water, stir and adjust the slurry, while scraping the upper layer of liquid with a scraper and continuously adding water to keep the liquid level unchanged, and after washing with water for 30 min, the pH of the slurry is measured to be 6.6. (2) Add 0.36 g of frother (methyl isobutyl methanol) and 0.22 g of organic amine collector (cocoa oil diamine), start flotation, scrape off the foam layer with a scraper until the foam color changes from black to grayish white, and obtain concentrate slurry and foam. (3) Add water to keep the liquid level unchanged, continue to scrape off the upper layer of liquid with a scraper, and wash three times with water for 20 minutes each time. After 60 minutes, the pH of the slurry is measured to be 7.5. (Specifically, after collecting the overflow of the first secondary washing, lime is added to adjust the pH to 7-9. Then, after two-stage sand filtration and one-stage ion exchange, the supernatant obtained is reused in the third secondary washing process of the concentrate slurry; the overflow of the third secondary washing is reused in the second secondary washing process of the concentrate slurry; the overflow of the second secondary washing is reused in the first secondary washing process of the concentrate slurry; in addition, fresh water is added according to the actual situation during the third secondary washing process of the concentrate slurry.) (4) Vacuum filter dewatering of the slurry, add calcium hydroxide as a modifier to the dewatered concentrate, stir and measure its pH. The amount of calcium hydroxide added is to control the overall pH to 8-9, and obtain phosphogypsum ecological restoration material with a water content of 10-15 wt%.

[0046] In addition, the foam collected during the flotation process is dehydrated and recycled for the preparation of organic fertilizer.

[0047] Meanwhile, the filtrate collected after vacuum filtration and dehydration is added to the raw material of high organic matter phosphogypsum for recycling.

[0048] Meanwhile, the backwashing impurities from the second-stage sand filter were combined and added to the raw material of the solid waste phosphogypsum sample, and the backwashing liquid from the first-stage ion exchange was treated and discharged into the tailings pond.

[0049] Similarly, the phosphogypsum ecological restoration material was tested according to the detection methods for total amount of solid waste pollutants and leachate, and the results are shown in Table 4-5 below.

[0050] Table 4. Results of total content detection of characteristic pollutants ; Table 5. Detection results of leachate content of characteristic pollutants ; Comparative Example 1 The present invention provides a comparative example of a method for preparing eco-remediation materials using phosphogypsum containing organic matter, as detailed below: Solid waste phosphogypsum (same as in Example 1) from a phosphate plant in Hubei Province was used as raw material. Its moisture content was found to be 29.2%. At the same time, the concentration of pollutants in the solid waste and the leachate was determined according to the total amount of pollutants in the solid waste and the concentration of the leachate.

[0051] (1) Weigh 1 kg of solid waste phosphogypsum sample (of which, the dry basis phosphogypsum mass is 708 g), add it to a 2 L flotation cell, add 1.5 L of water, stir and adjust the slurry, and measure the pH of the slurry to be 3.1. While scraping the upper layer of liquid with a scraper, continuously add water to keep the liquid level unchanged, add water (3.6 L) to the slurry for washing, and measure the pH of the slurry to be 6.2. Vacuum filter the slurry to dehydrate and obtain water-washed purified phosphogypsum with a water content of 10-15 wt%.

[0052] Similarly, the water-washed purified phosphogypsum was tested according to the detection methods for total amount of solid waste pollutants and leachate, and the results are shown in Table 6-7 below.

[0053] Table 6. Results of total content detection of characteristic pollutants ; Table 7. Detection results of leachate content of characteristic pollutants ; Comparative Example 2 This invention provides a comparative example of a method for preparing eco-remediation materials using high-organic-matter phosphogypsum, as detailed below: Solid waste phosphogypsum (same as in Example 1) from a phosphate plant in Hubei Province was used as raw material. Its moisture content was found to be 29.2%. At the same time, the concentration of pollutants in the solid waste and the leachate was determined according to the total amount of pollutants in the solid waste and the concentration of the leachate.

[0054] (1) Weigh 1 kg of solid waste phosphogypsum sample (of which, the dry basis phosphogypsum mass is 708 g), add it to a 2 L flotation cell, add 1.5 L of water, stir and adjust the slurry, and measure the slurry pH to be 3.2. (2) While scraping out the upper liquid with a scraper, water was continuously added to keep the liquid level unchanged. After washing the slurry with water (3.6 L) for 30 min, the pH of the slurry was measured to be 6.1. (3) Add 0.22 g of frother (diethyl phthalate) and 0.18 g of organic amine collector (dodecylamine), stir and float until the foam changes from black to grayish-white, to obtain concentrate slurry and foam; (4) Vacuum filter the concentrate slurry to dewater it and obtain water-washed and flotation-purified phosphogypsum with a water content of 10-15 wt%.

[0055] Similarly, the water-washed + flotation purified phosphogypsum was tested according to the detection methods for total pollutant content and leachate in solid waste, and the results are shown in Table 8-9 below.

[0056] Table 8. Results of total content detection of characteristic pollutants ; Table 9. Detection results of leachate content of characteristic pollutants ; Comparative Example 3 This invention provides a comparative example of a method for preparing eco-remediation materials using high-organic-matter phosphogypsum, as detailed below: Solid waste phosphogypsum (same as in Example 1) from a phosphate plant in Hubei Province was used as raw material. Its moisture content was found to be 29.2%. At the same time, the concentration of pollutants in the solid waste and the leachate was determined according to the total amount of pollutants in the solid waste and the concentration of the leachate.

[0057] (1) Weigh 1 kg of solid waste phosphogypsum sample (of which, the dry basis phosphogypsum mass is 708 g), add it to a 3 L flotation cell, add 2.5 L of water, stir and adjust the slurry, and measure the slurry pH to be 3.3. (2) While scraping out the upper liquid with a scraper, water was continuously added to keep the liquid level unchanged. Water (5 L) was added to the slurry and washed for 30 min. The pH of the slurry was measured to be 6.7. (3) Subsequently, 0.36 g of frother (methyl isobutyl methanol) and 0.22 g of collector (paraffin oxide) were added, and the flotation was stirred until the foam changed from black to grayish-white, to obtain concentrate slurry and foam; (4) Vacuum filter the concentrate slurry to dehydrate it and obtain phosphogypsum ecological restoration material with a water content of 10-15 wt%.

[0058] Similarly, the phosphogypsum ecological restoration material was tested according to the detection methods for total amount of pollutants in solid waste and leachate, and the results are shown in Table 10-11 below.

[0059] Table 10 Results of total content detection of characteristic pollutants ; Table 11 Detection results of leachate content of characteristic pollutants ; The above embodiments are merely examples of several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent.

[0060] It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A process for preparing ecological restoration materials using phosphogypsum containing organic matter, characterized in that, include: S1. Add water to the phosphogypsum containing organic matter and stir to form a slurry. Wash the slurry with water until the pH of the slurry is greater than 6. S2. Place the slurry from S1 into a flotation cell, add frother and collector and carry out flotation until the foam changes from black to grayish-white, to obtain concentrate slurry and foam. S3. Wash the concentrate slurry from S2 with water 2-3 times until the pH of the concentrate slurry is 6.5-7.

5. S4. After dehydrating the concentrate slurry that has undergone two water washings in S3, add a modifier and adjust its pH to 8-9 by stirring. Then dehydrate to obtain phosphogypsum ecological restoration material.

2. The process according to claim 1, characterized in that, In step S2, The concentration of the slurry in the flotation cell is 20-25 wt%; And / or, the foaming agent is one or more of methyl isobutyl methanol, butyl phthalate, and α-terpene alcohol oil; And / or, the collector is an organic amine scavenger, preferably dodecylamine and / or coconut oil diamine.

3. The process according to claim 2, characterized in that, In step S2, for 1 ton of phosphogypsum containing organic matter, the amount of foaming agent and the amount of collector added are 0.1-0.5 kg and 0.05-0.5 kg, respectively.

4. The process according to claim 1, characterized in that, In step S4, The modifier is at least one of calcium oxide, calcium hydroxide, and carbide slag; And / or, the water content of the phosphogypsum ecological restoration material obtained by dehydration is 10-15 wt%.

5. The process according to any one of claims 1-4, characterized in that, In step S1, During the mixing and slurry preparation process, the amount of water added is such that the concentration of the slurry after preparation is controlled to be 20-25 wt%. And / or, the organic matter content in the phosphogypsum containing organic matter is 2-20 wt%.

6. The process according to any one of claims 1-5, characterized in that, It also includes adjusting the pH of the overflow from the water washing process in step S1 to 7-9 by adding lime, allowing it to stand until it becomes clear, separating it, reusing the supernatant obtained from the separation in the water washing process after slurry preparation, and adding the bottom slurry obtained from the separation to the raw material containing organic matter, phosphogypsum.

7. The process according to any one of claims 1-5, characterized in that, It also includes the process of adjusting the pH and post-treating the overflow from the secondary washing in step S3, and then reusing the resulting supernatant in the secondary washing process of the concentrate slurry. Preferably, when the concentrate slurry is washed three times, the overflow from the third secondary washing is reused in the second secondary washing process of the concentrate slurry, the overflow from the second secondary washing is reused in the first secondary washing process of the concentrate slurry, and the overflow from the first secondary washing is collected, lime is added to adjust the pH to 7-9, and then after two-stage sand filtration and one-stage ion exchange, the supernatant obtained is reused in the third secondary washing process of the concentrate slurry.

8. The process according to any one of claims 1-7, characterized in that, Step S2 also includes collecting and dehydrating the foam generated during the flotation process to recycle it into organic fertilizer; And / or, step S4 may further include adding the filtrate generated during the dehydration process to the phosphogypsum raw material containing organic matter for recycling.

9. The process according to any one of claims 1-8, characterized in that, All equipment used in the water washing process in step S1, the flotation process in step S2, and the secondary water washing process in step S3 are existing mineral processing flotation machines. Preferably, in the water washing process in step S1 and the secondary water washing process in step S3, the scum tank of the mineral processing flotation machine is used to collect the water washing overflow.

10. The phosphogypsum ecological restoration material prepared by the process described in any one of claims 1-9.

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