A method for harmless treatment of phosphogypsum and removal and / or recovery of phosphorus, fluorine

Abstract

The present application belongs to the technical field of mineralization solidification auxiliary treatment, and more particularly relates to a method for harmless treatment of phosphogypsum and removal and / or recovery of phosphorus and fluorine. The present application adopts a solidifying agent to solidify and treat phosphogypsum leaching solution, and then adopts polymeric aluminum ferric sulfate for flocculation treatment, so that the phosphorus and fluorine in the phosphogypsum leaching solution can be removed and / or recovered after filtration. The method provided by the present application can significantly reduce the solidifying agent dosage, reduce the residual amount of soluble phosphorus and fluorine in the phosphogypsum leaching solution, improve the removal rate of soluble phosphorus and fluorine in the leaching solution, and further improve the recovery rate of soluble phosphorus and fluorine in the phosphogypsum, thereby reducing the cost of harmless treatment of the phosphogypsum leaching solution and realizing the recycling of phosphogypsum, phosphorus, fluorine and other resources. The method provided by the present application is simple in process, low in requirement for equipment, free of environmental pollution and low in cost, and is suitable for popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of mineralization and solidification auxiliary treatment technology, and more specifically, relates to a method for harmlessly treating phosphogypsum and removing and / or recovering phosphorus and fluorine. Background Technology

[0002] Phosphogypsum is a solid waste generated during the wet process of phosphoric acid production. Besides containing phosphogypsum formed during the acidolysis of phosphate concentrate, undecomposed acid-insoluble matter, and undecomposed phosphate rock powder, it also contains large amounts of soluble phosphorus, fluorine, and other harmful impurities. During phosphogypsum stockpiling, these soluble phosphorus and fluorine substances dissolve into leachate and pollute water systems, posing a significant threat to the ecological environment. Furthermore, residual phosphorus and fluorine can affect the performance of materials made from phosphogypsum, severely hindering its resource utilization. Currently, the stockpiled amount of phosphogypsum is enormous. Achieving harmless treatment of phosphogypsum and recovering its soluble phosphorus and fluorine will bring significant environmental and economic benefits. Therefore, the harmless treatment of phosphorus and fluorine in phosphogypsum is crucial for its resource utilization.

[0003] Common methods for the harmless treatment of phosphogypsum include flotation, acid leaching, neutralization, and washing. Flotation can remove silicon, residual fine phosphate rock, and organic matter from phosphogypsum, but it is costly. Acid leaching can improve the removal rate of insoluble phosphorus and fluoride from phosphogypsum, but it cannot remove soluble phosphorus and fluoride. Neutralization removes soluble phosphorus and fluoride by adding alkaline substances such as quicklime, but it cannot be recycled. The traditional water washing method for phosphogypsum involves mixing phosphogypsum and lime water, stirring, and then filtering. The soluble phosphorus and fluoride in the phosphogypsum react with the lime to form calcium phosphate and calcium fluoride, which are then filtered and stockpiled together with the phosphogypsum. The separated wash water is concentrated by reverse osmosis and recycled. Although this water washing process can solidify most of the soluble phosphorus and fluoride in phosphogypsum, these phosphorus and fluoride impurities are difficult to recycle after solidification. These phosphorus and fluoride impurities remain in the phosphogypsum, wasting resources and affecting the resource utilization of phosphogypsum. Furthermore, subsequent water treatment methods suffer from high membrane filtration costs and the potential for secondary pollution from phosphorus and fluoride-containing wastewater generated after membrane filtration.

[0004] In the traditional lime neutralization method for solidifying soluble phosphorus and fluoride in phosphogypsum, the resulting calcium phosphate and calcium fluoride solid particles are small, making the recovery of solidified soluble phosphorus and fluoride difficult. Therefore, it is necessary to further improve the removal and recovery rates of soluble phosphorus and fluoride in phosphogypsum / phosphogypsum leaching solutions. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for harmlessly treating phosphogypsum and removing and / or recovering phosphorus and fluorine, so as to solve the technical problems of high cost, large amount of curing agent added, high content of soluble phosphorus and fluorine in the treated leaching solution, low phosphorus and fluorine recovery rate, and inability to achieve resource recycling and reuse in the prior art.

[0006] To achieve the above objectives, the present invention provides a method for harmlessly treating phosphogypsum and removing and / or recovering phosphorus and fluorine, comprising the following steps:

[0007] S1. Mix and stir the curing agent and phosphogypsum rinsing solution, and then perform a curing treatment to obtain a suspension;

[0008] S2. Mix and stir the polyaluminum ferric sulfate and the suspension, perform flocculation treatment, and filter to remove and / or recover soluble phosphorus and fluorine from the phosphogypsum leaching solution.

[0009] Preferably, in step S1, the phosphogypsum rinsing solution is prepared by mixing and stirring phosphogypsum with water, rinsing, and filtering to obtain the phosphogypsum rinsing solution.

[0010] More preferably, the stirring speed is 400 r / min to 600 r / min, and the rinsing time is 0.5 h to 1 h.

[0011] Preferably, in step S1, the curing agent is one or more of calcium oxide, calcium hydroxide, calcium carbonate, and carbide slag.

[0012] Preferably, in step S1, the mass ratio of phosphate ions in the curing agent and the phosphogypsum rinsing solution is (2.4-4.2):1, and the mass ratio of fluoride ions in the curing agent and the phosphogypsum rinsing solution is (62.5-112.5):1.

[0013] Preferably, in step S2, the polyaluminum ferric sulfate contains 15% to 20% aluminum and 0.5% to 2% iron.

[0014] More preferably, the polyaluminum ferric sulfate contains 16% to 18% aluminum and 0.5% to 1% iron.

[0015] Preferably, the mass ratio of the curing agent to the polyaluminum ferric sulfate is 1:(0.5-3).

[0016] More preferably, the mass ratio of the curing agent to the polyaluminum ferric sulfate is 1:(0.5-1.5).

[0017] Preferably, in steps S1 and S2, the stirring speed is 300 r / min to 500 r / min, and the stirring time is 20 min to 40 min.

[0018] In summary, compared with the prior art, the above-described technical solutions conceived by this invention have the following advantages:

[0019] Beneficial effects:

[0020] (1) This invention provides a method for the harmless treatment of phosphogypsum and the removal and / or recovery of phosphorus and fluorine. First, a curing agent is used to solidify the phosphogypsum leaching solution. Then, polyaluminum ferric sulfate is added for flocculation treatment, allowing soluble phosphorus and fluorine in the phosphogypsum leaching solution to enter the hydrolytic precipitate generated by the polyaluminum ferric sulfate, promoting the flocculation and removal of soluble phosphorus and fluorine from the leaching solution. The method provided by this invention significantly reduces the amount of curing agent added while significantly reducing the residual amount of soluble phosphorus and fluorine in the phosphogypsum leaching solution, improving the removal rate and recovery rate of soluble phosphorus and fluorine, reducing the cost of harmless treatment of the phosphogypsum leaching solution, and realizing the recycling and reuse of resources such as phosphogypsum, phosphorus, and fluorine. The method provided by this invention has a simple process, low equipment requirements, no environmental pollution, and low cost, making it suitable for industrial application.

[0021] (2) In a preferred embodiment of the present invention, phosphogypsum is leached to obtain a phosphogypsum leaching solution, which is then treated using the method provided above. Testing showed that the turbidity of the treated leaching solution was only 21.8 NTU, and the removal rate of soluble phosphorus in the treated leaching solution reached 99.99%, while the removal rate of soluble fluoride reached 94.82%. The phosphorus and fluoride content in the treated leaching solution meets the requirements of GB 8978-1996 "Integrated Wastewater Discharge Standard," enabling the leaching solution to be recycled and bringing greater environmental and economic benefits. Furthermore, it can improve the recovery rate of soluble phosphorus and fluoride in phosphogypsum, allowing the recovered phosphorus and fluoride to be reused in the wet-process phosphoric acid production process (wet-process acid production process), while simultaneously achieving low-cost, harmless treatment of phosphogypsum. Attached Figure Description

[0022] Figure 1 A flowchart for the harmless treatment of phosphogypsum provided by the present invention;

[0023] Figure 2 The removal rates of soluble phosphorus and soluble fluoride in the phosphogypsum leaching solution after treatment in Example 1 and Comparative Examples 1-3;

[0024] Figure 3 The removal rate of soluble phosphorus in the phosphogypsum leaching solution after treatment in Example 3. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] Traditional methods use only lime water as a harmless modifier for phosphogypsum, requiring large amounts of quicklime to achieve a good solidification effect of soluble phosphorus and fluoride. Furthermore, the generated calcium phosphate and calcium fluoride cannot be recycled. This not only wastes resources but also creates secondary wastewater treatment problems. Therefore, this invention provides a method for harmlessly treating phosphogypsum and removing and / or recovering phosphorus and fluoride, such as... Figure 1 As shown, it includes the following steps:

[0027] S1. Mix and stir the curing agent and phosphogypsum rinsing solution, and then perform a curing treatment to obtain a suspension;

[0028] S2. Mix and stir the polyaluminum ferric sulfate and the suspension, perform flocculation treatment, and filter to remove and / or recover soluble phosphorus and fluorine from the phosphogypsum leaching solution.

[0029] In this application, "soluble phosphorus" includes phosphate, hydrogen phosphate, dihydrogen phosphate, phosphite, and hydrogen phosphite, and "soluble fluorine" refers to fluoride ions.

[0030] The curing agent described in this application can effectively solidify soluble phosphorus and fluorine, and also create an alkaline reaction environment. This not only promotes the hydrolysis reaction of subsequently added polyaluminum ferric sulfate, but also effectively reduces the acidity of phosphogypsum, enabling it to meet the pollution control standards for general industrial solid waste storage and landfill (GB18599-2020). The curing agent used in this application is preferably a low-cost, high-efficiency, and pollution-free curing agent, such as, but not limited to, one or more of calcium oxide, calcium hydroxide, calcium carbonate, and carbide slag. In a specific embodiment of this invention, the curing agent is selected from calcium oxide, with the aim of low-cost solidification of the phosphogypsum leaching solution. This curing agent also has the advantages of being pollution-free and having minimal impact on subsequent phosphorus and fluorine recovery processes.

[0031] This application does not limit the source of the above-mentioned phosphogypsum leaching solution. In some embodiments, the source of the above-mentioned phosphogypsum leaching solution includes, but is not limited to, production in actual application, laboratory preparation, etc. In some embodiments, the preparation method of the above-mentioned phosphogypsum leaching solution is as follows: phosphogypsum is mixed with water, stirred and leached, and then filtered to obtain the above-mentioned phosphogypsum leaching solution.

[0032] In some embodiments, the stirring speed is 400 r / min to 600 r / min, and the rinsing time is 0.5 h to 1 h. The purpose is to ensure that the soluble phosphorus and fluorine in the phosphogypsum are fully dissolved in the water. In practical applications, appropriately increasing / decreasing the stirring speed and extending / shortening the stirring time according to the amount of phosphogypsum added, the solid-liquid ratio, and the stirring method is also within the scope of protection of this invention.

[0033] In some embodiments, in step S1, the mass ratio of phosphate ions in the curing agent and the phosphogypsum eluent is (2.4–4.2):1, and the mass ratio of fluoride ions in the curing agent and the phosphogypsum eluent is (62.5–112.5):1. If the amount of curing agent added is too small, it cannot fully react with the soluble phosphorus and fluoride in the eluent, thus affecting the flocculation effect of polyaluminum ferric sulfate and reducing the removal rate of soluble phosphorus and fluoride in the eluent. Conversely, if the amount of curing agent added is too large, it will consume the acid in the phosphorus and fluoride recovery process, affecting the recovery rate and increasing the recovery cost.

[0034] In this application, the aluminum content of the aforementioned polyaluminum ferric sulfate is 15%–20%, and the iron content is 0.5%–2%. In a preferred embodiment, the aluminum content of the aforementioned polyaluminum ferric sulfate is 16%–18%, and the iron content is 0.5%–1%. This is because a small amount of iron is beneficial for increasing floc density, increasing floc volume, and accelerating floc settling, making filtration easier. Excessive iron content will cause the filtrate to be pale yellow, and excessive iron in the filtrate is not conducive to the subsequent recovery and utilization of phosphorus and fluorine. It should be understood that the aforementioned polyaluminum ferric phosphate in this application can be prepared by techniques known to those skilled in the art, or it can be purchased commercially.

[0035] In some embodiments, the mass ratio of the curing agent to the polyaluminum ferric sulfate is 1:(0.5-3). In a preferred embodiment, the mass ratio of the curing agent to the polyaluminum ferric sulfate is 1:(0.5-1.5). This is because too little polyaluminum ferric sulfate results in poor flocculation, affecting the phosphorus and fluoride curing rate, leading to excessively small flocculent solid particles and excessive phosphorus and fluoride content in the filtered solution; too much polyaluminum ferric sulfate increases the content of flocculent solids and impurities in the filtrate.

[0036] This application does not limit the stirring method in steps S1 and S2 described above. In some embodiments, the stirring speed is 300 r / min to 500 r / min, and the stirring time is 20 min to 40 min. In practical applications, appropriately increasing / decreasing the stirring speed and extending / shortening the stirring time according to the stirring method are also within the scope of protection of this invention.

[0037] This invention provides a method for the harmless treatment of phosphogypsum and the removal and / or recovery of phosphorus and fluorine. First, a curing agent is used to solidify the phosphogypsum leaching solution. Then, polyaluminum ferric sulfate is added for flocculation treatment, allowing soluble phosphorus and fluorine in the phosphogypsum leaching solution to enter the hydrolytic precipitate generated by the polyaluminum ferric sulfate, promoting the flocculation and removal of soluble phosphorus and fluorine from the leaching solution. This method significantly reduces the amount of curing agent required while significantly reducing the residual amount of soluble phosphorus and fluorine in the phosphogypsum leaching solution, improving the removal rate of soluble phosphorus and fluorine in the leaching solution, increasing the recovery rate of soluble phosphorus and fluorine in phosphogypsum, reducing the cost of harmless treatment of phosphogypsum leaching solution, and achieving the recycling and reuse of resources such as phosphogypsum, phosphorus, and fluorine. The method provided by this invention is simple, requires minimal equipment, is environmentally friendly, and has low cost, making it suitable for industrial application.

[0038] The above technical solution will be described in detail below with reference to specific embodiments.

[0039] Example 1

[0040] Polyaluminum ferric sulfate was used to remove soluble phosphorus and soluble fluoride from phosphogypsum / phosphogypsum leaching solution, as detailed below:

[0041] 1) Preparation of phosphogypsum leaching solution

[0042] 10g of solid phosphogypsum was weighed into a beaker, 100mL of distilled water was added, the beaker was sealed with plastic wrap, and stirred on a magnetic stirrer at 500r / min for 1h. After stirring, the mixture was filtered, and the filtrate was stored in a beaker and sealed with plastic wrap for later use. The soluble phosphorus content in the eluent was measured to be 4200mg / L, and the soluble fluorine content was 156.67mg / L.

[0043] 2) Determine the removal rates of soluble phosphorus and soluble fluoride in the phosphogypsum leaching solution.

[0044] Take 100 mL of the prepared phosphogypsum leaching solution, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, then add 2.2 g of polyaluminum ferric sulfate (purchased from Yiwu Xinbang Environmental Protection Technology Co., Ltd., with an aluminum content of 16.5% and an iron content of 0.5%), stir for 30 min at a reaction speed of 100 r / min, filter, and determine the residual amounts of soluble phosphorus and soluble fluorine in the solution.

[0045] The eluent obtained after treatment in this embodiment is colorless and transparent. Testing showed that the removal rates of soluble phosphorus and soluble fluoride in the treated eluent were 99.99% and 94.82%, respectively (see...). Figure 2At this point, the phosphorus content in the leaching solution is 0.42 mg / L and the fluoride ion content is 9.59 mg / L, which meets the discharge standard (GB 8978-1996 Integrated Wastewater Discharge Standard: the phosphorus content in the leaching solution should be below 0.5 mg / L and the fluoride content should be below 10 mg / L). The treated leaching solution can be recycled and reused.

[0046] Comparative Example 1

[0047] The removal of soluble phosphorus and soluble fluoride from phosphogypsum / phosphogypsum leaching solution without using flocculants is as follows:

[0048] Take 100 mL of the phosphogypsum leaching solution prepared in Example 1, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, filter, and determine the residual amounts of soluble phosphorus and soluble fluorine in the solution.

[0049] Tests showed that the removal rates of soluble phosphorus and soluble fluoride in the treated eluent were 95.41% and 76.93%, respectively (see...). Figure 2 At this point, the phosphorus content in the leachate was 192.78 mg / L and the fluoride ion content was 36.91 mg / L, which did not meet the emission standards.

[0050] Comparing Example 1 and Comparative Example 1, it can be seen that after adding polyaluminum ferric sulfate for flocculation treatment, the residual amounts of phosphorus and fluoride ions in the eluent are significantly reduced, and the removal rates of soluble phosphorus and soluble fluoride in the eluent are increased by 5% to 10%, enabling the recycling of phosphogypsum eluent. The reason for this may be that the aluminum and iron ions in polyaluminum ferric sulfate generate a large amount of hydrolyzed precipitates after being added to the eluent. During the rapid precipitation process, the colloidal particles in the eluent are swept (or captured) by these hydrolyzed precipitates, resulting in co-precipitation. This causes the small colloidal particles in the eluent to form larger flocs, reducing particle residue in the eluent, accelerating the precipitation rate, and ultimately achieving a better removal effect of soluble phosphorus and fluoride in the eluent. In addition, the addition of calcium oxide makes the phosphogypsum leaching solution alkaline. Under alkaline conditions and at a certain temperature, polyaluminum ferric sulfate can accelerate the hydrolysis reaction of aluminum and iron ions, producing more hydrolyzed precipitates. This allows more soluble phosphorus and fluorine in the leaching solution to be adsorbed into the hydrolyzed precipitates and react with substances in the alkaline suspension. It may also further promote the flocculation and removal of soluble phosphorus and fluorine in the phosphogypsum leaching solution.

[0051] Comparative Example 2

[0052] Polyaluminum sulfate was used to remove soluble phosphorus and soluble fluoride from phosphogypsum / phosphogypsum leaching solution, as detailed below:

[0053] Take 100 mL of the phosphogypsum leaching solution prepared in Example 1, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, then add 2.2 g of polyaluminum sulfate (purchased from Shanghai McLean Technology Co., Ltd., with an aluminum content of 16.5%), stir for 30 min at a reaction speed of 100 r / min, filter, and determine the residual amounts of soluble phosphorus and soluble fluorine in the solution.

[0054] The eluent after treatment in this comparative example was colorless and transparent. Tests showed that the removal rates of soluble phosphorus and soluble fluoride in the treated eluent were 96.58% and 84.93%, respectively (see...). Figure 2 At this point, the phosphorus content in the leaching solution was 143.64 mg / L and the fluoride ion content was 24.12 mg / L, which did not meet the requirements of GB 8978-1996 "Integrated Wastewater Discharge Standard".

[0055] Comparative Example 3

[0056] Polyferric sulfate was used to remove soluble phosphorus and soluble fluoride from phosphogypsum / phosphogypsum leaching solution, as detailed below:

[0057] Take 100 mL of the phosphogypsum leaching solution prepared in Example 1, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, then add 2.2 g of polyferric sulfate (purchased from Hubei Anaiji Environmental Protection Technology Co., Ltd., with an iron content of 19%), stir for 30 min at a reaction speed of 100 r / min, filter, and determine the residual amounts of soluble phosphorus and soluble fluorine in the solution.

[0058] The treated eluent was distinctly yellow. Tests showed that the removal rates of soluble phosphorus and soluble fluoride in the treated eluent were 97.41% and 89.68%, respectively (see...). Figure 2 At this point, the phosphorus content in the eluent was 108.78 mg / L and the fluoride ion content was 16.52 mg / L, which did not meet the requirements of GB 8978-1996 "Integrated Wastewater Discharge Standard". Comparing Example 1 with Comparative Examples 2 and 3, it can be seen that polyaluminum ferric sulfate, as a flocculant, significantly outperformed polyaluminum sulfate and polyferric sulfate in removing soluble phosphorus and fluoride from the eluent, and even surpassed the simple sum of their effects.

[0059] Comparative Example 4

[0060] Polyaluminum ferric sulfate was used to remove soluble phosphorus and soluble fluoride from phosphogypsum / phosphogypsum leaching solution, as detailed below:

[0061] Take 100 mL of the phosphogypsum leaching solution prepared in Example 1, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, then add 2.2 g of polyaluminum ferric sulfate (purchased from Yiwu Xinbang Environmental Protection Technology Co., Ltd., with an aluminum content of 16.5% and an iron content of 5%), stir for 30 min at a reaction speed of 100 r / min, and then filter. It can be seen that the treated leaching solution is light yellow.

[0062] Comparative Example 5

[0063] Polyaluminum ferric sulfate was used to remove soluble phosphorus and soluble fluoride from phosphogypsum / phosphogypsum leaching solution, as detailed below:

[0064] Take 100 mL of the phosphogypsum leaching solution prepared in Example 1, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, then add 2.2 g of polyaluminum ferric sulfate (purchased from Yiwu Xinbang Environmental Protection Technology Co., Ltd., with an aluminum content of 10% and an iron content of 0.5%), stir for 30 min at a reaction speed of 100 r / min, filter, and determine the residual amounts of soluble phosphorus and soluble fluorine in the solution.

[0065] Tests showed that the phosphorus content in the treated leaching solution was 126 mg / L and the fluoride ion content was 14.1 mg / L, which did not meet the requirements of GB 8978-1996 "Integrated Wastewater Discharge Standard".

[0066] Example 2

[0067] Take 100 mL of the phosphogypsum leaching solution prepared in Example 1, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, then add 2.2 g of polyaluminum ferric sulfate (same as in Example 1), stir for 30 min at a reaction speed of 100 r / min, filter, and measure the turbidity of the filtrate.

[0068] The turbidity of the filtrate was measured to be 21.8 (NTU).

[0069] Comparative Example 6

[0070] Take 100 mL of the phosphogypsum leaching solution prepared in Example 1, then add 1.6 g of calcium oxide, stir for 30 min at a reaction speed of 500 r / min, filter, and measure the turbidity of the filtrate.

[0071] The turbidity of the filtrate was measured to be 141 NTU at this time.

[0072] As can be seen from Example 2 and Comparative Example 4, after adding polyaluminum ferric sulfate for flocculation treatment, the turbidity of the eluent decreased by 119.8 (NTU). The reason may be that the originally insoluble small particles in the eluent were aggregated into large particles under the action of polyaluminum ferric sulfate, thereby reducing the turbidity of the eluent.

[0073] Example 3

[0074] The phosphogypsum leaching solution prepared in Example 1 was divided into a group without flocculant and a group with flocculant.

[0075] In the group without flocculant, 100 mg, 200 mg, 300 mg, 400 mg, 500 mg, 600 mg, and 700 mg of calcium oxide were added to 30 mL of phosphogypsum leaching solution, respectively. After stirring for 30 min at a reaction speed of 500 r / min, the solution was filtered, and the residual amount of soluble phosphorus in the leaching solution was determined.

[0076] Add flocculant group: Add 500 mg of calcium oxide to 30 mL of phosphogypsum leaching solution and stir for 30 min at a reaction speed of 500 r / min. Then add 400 mg, 450 mg, 500 mg, 550 mg and 600 mg of polyaluminum ferric sulfate (same as in Example 1) respectively, stir for 30 min at a reaction speed of 100 r / min and filter. Measure the residual amount of soluble phosphorus in the solution.

[0077] The results are as follows Figure 3 As shown in the figure, without flocculant, the removal rate of soluble phosphorus in the leachate gradually increased with the increase of calcium oxide dosage. When the calcium oxide dosage was 700 mg, the residual soluble phosphorus in the leachate after treatment was 4.2 mg / L, and the removal rate of soluble phosphorus in the leachate reached a maximum of 99.9%. In the group with flocculant, the calcium oxide dosage was 500 mg, and the removal rate of soluble phosphorus in the leachate remained stable at 99.99%, with a residual soluble phosphorus content of 0.42 mg / L. Furthermore, with the gradual increase of flocculant dosage, the removal rate of soluble phosphorus in the leachate remained stable and did not increase further. In summary, the addition of polyaluminum ferric sulfate for flocculation treatment significantly reduced the residual soluble phosphorus in the leachate while reducing the curing agent dosage by 28%.

[0078] In summary, comparing the results of the above embodiments and comparative examples shows that adding polyaluminum ferric sulfate as a flocculant after lime solidification of the phosphogypsum eluent can achieve a 99.99% removal rate of soluble phosphorus and a 94.8% removal rate of soluble fluoride in the phosphogypsum eluent. In practical applications, using the method provided by this invention for the harmless treatment of phosphogypsum can not only significantly reduce the cost of harmless treatment but also improve the recovery rate of soluble phosphorus and fluoride in the eluent, thus better recovering these substances. Simultaneously, the recovered phosphorus and fluoride can also be used in wet acid production processes, achieving resource recycling and reuse.

[0079] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for harmlessly treating phosphogypsum and removing and / or recovering phosphorus and fluorine, characterized in that, Includes the following steps: S1. Mix and stir the curing agent and phosphogypsum rinsing solution, and then perform a curing treatment to obtain a suspension; The mass ratio of phosphate ions in the curing agent and the phosphogypsum leaching solution is (2.4~4.2):1, and the mass ratio of fluoride ions in the curing agent and the phosphogypsum leaching solution is (62.5~112.5):

1. S2. Mix and stir the polyaluminum ferric sulfate and the suspension, perform flocculation treatment, and filter to remove and / or recover soluble phosphorus and fluorine in the phosphogypsum leaching solution; The polyaluminum ferric sulfate contains 15% to 20% aluminum and 0.5% to 2% iron. The mass ratio of the curing agent to the polyaluminum ferric sulfate is 1:(0.5~3).

2. The method according to claim 1, characterized in that, In step S1, the preparation method of the phosphogypsum rinsing solution is as follows: phosphogypsum is mixed with water and stirred for rinsing, and then filtered to obtain the phosphogypsum rinsing solution.

3. The method according to claim 2, characterized in that, The stirring speed is 400 r / min to 600 r / min, and the rinsing time is 0.5 h to 1 h.

4. The method according to claim 1, characterized in that, In step S1, the curing agent is one or more of calcium oxide, calcium hydroxide, calcium carbonate, and carbide slag.

5. The method according to claim 1, characterized in that, The polyaluminum ferric sulfate contains 16% to 18% aluminum and 0.5% to 1% iron.

6. The method according to claim 1, characterized in that, The mass ratio of the curing agent to the polyaluminum ferric sulfate is 1:(0.5~1.5).

7. The method according to claim 1, characterized in that, In steps S1 and S2, the stirring speed is 300 r / min to 500 r / min, and the stirring time is 20 min to 40 min.

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