A harmless treatment and resource utilization method of yellow phosphorus slag solid waste and phosphogypsum leachate

Abstract

The application discloses a harmless treatment and resource utilization method of yellow phosphorus slag solid waste and phosphogypsum leachate, relates to the technical field of industrial solid waste treatment and resource utilization, and comprises the following steps: mixing phosphogypsum and ultrapure water to prepare PG suspension liquid, adding ground yellow phosphorus slag for collaborative treatment, and carrying out solid-liquid separation to obtain PG-PS leachate and PG-PS precipitate; adding an additive to the PG-PS leachate to remove harmful components of phosphorus and fluorine; and mixing the PG-PS precipitate with biochar, red mud, carbide slag and cement according to a proportioning ratio, adding water, pouring and curing to prepare modified PG filling material. The application realizes efficient removal of phosphorus and fluorine in the leachate, the water quality meets the discharge standard, the obtained precipitate is resourcefully utilized, the prepared filling material has good environmental safety and engineering applicability, the application uses industrial solid waste as raw material, has simple process and low cost, realizes pollution control and dual utilization of phosphogypsum and yellow phosphorus slag, and has good ecological benefits and application value.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste treatment and resource utilization technology, and in particular to a method for the harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate. Background Technology

[0002] Phosphogypsum is a major byproduct of wet-process phosphoric acid production. However, the comprehensive utilization rate of phosphogypsum is low, less than 50%. Large quantities of phosphogypsum are disposed of through open-air stockpiling, resulting in a waste of land resources. Furthermore, prolonged open-air stockpiling allows rainwater to wash away soluble phosphorus, fluorine, and other impurities, causing them to seep into groundwater or flow into rivers, resulting in significant waste of phosphorus resources and severe environmental pollution. This seriously hinders the green development of the phosphorus chemical industry and the comprehensive utilization of phosphogypsum. Therefore, the harmless treatment and resource utilization of phosphogypsum leachate has become an urgent problem to be solved.

[0003] In recent years, domestic and international research has explored the treatment of phosphogypsum leachate and investigated various methods for treating phosphorus and fluoride-containing wastewater, including ion exchange, biological treatment, membrane separation, electrocoagulation, precipitation, and adsorption. For example, Zhou et al. used quicklime and sodium hydroxide to treat phosphogypsum leachate and recover valuable sediments; Xie et al. prepared acid-modified sulfonate aluminate cement as a neutralizing agent and coagulant to remove fluorides and phosphates from phosphogypsum leachate; Ricardo et al. increased the pH value of acidic phosphogypsum leachate with Ca(OH)2 solution, achieving removal rates of 100% for heavy metals and 90% for fluorides; Kumari et al. prepared a novel adsorbent using ferroalloy electric arc furnace slag as raw material, which can serve as a potential adsorbent for the degradation of industrial wastewater. However, the above methods still have certain limitations in practical applications. The adsorption method is easily interfered with by the high concentration of sulfate in the leachate, which leads to a decrease in the adsorption performance of fluoride. Although the chemical precipitation method has a good treatment effect, its ability to remove fluorine and phosphorus is limited, and the treated products have not yet been effectively utilized as resources. The overall utilization rate of phosphogypsum still needs to be improved.

[0004] Yellow phosphorus slag is another industrial solid waste generated during the electrothermal production of yellow phosphorus. Its main chemical components are SiO2 and CaO, with their content reaching up to 90%. Industrially, approximately 8-10 tons of yellow phosphorus slag are generated for every ton of yellow phosphorus produced. Currently, the comprehensive utilization rate of yellow phosphorus slag is also low. Large-scale stockpiling not only occupies land resources, but also allows harmful elements such as fluorine and phosphorus contained in it to easily enter the surrounding environment after being leached by rainwater, causing pollution. Therefore, the rational utilization of yellow phosphorus slag as a solid waste resource is particularly important. Summary of the Invention

[0005] This invention provides a method for the harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate, aiming to solve the problems of poor removal of harmful components such as phosphorus and fluorine and low resource utilization rate of treated products in the existing technology of phosphogypsum leachate treatment. It achieves dual effective utilization of phosphogypsum and yellow phosphorus slag for pollution control and resource utilization, and protects the ecological environment.

[0006] This invention provides a method for the harmless treatment and resource utilization of leachate from yellow phosphorus slag solid waste and phosphogypsum. Through multi-stage treatment, phosphorus and fluorine in the leachate are efficiently removed, and the separated precipitate is used to prepare backfill material. This method not only protects the ecological environment, but also promotes the efficient utilization of industrial solid waste resources and the green and sustainable development of the phosphorus chemical industry.

[0007] The technical solution of the present invention is as follows: A method for the harmless treatment and resource utilization of leachate from yellow phosphorus residue solid waste and phosphogypsum, comprising the following specific steps: (1) Weigh phosphogypsum (PG) and add it to ultrapure water. Stir well at room temperature to obtain PG suspension; (2) Add the ground yellow phosphorus residue (PS) to the suspension in step (1), stir and mix evenly, and then perform solid-liquid separation to obtain PG-PS leachate and PG-PS precipitate; (3) Add additives to the PG-PS leachate and stir to remove harmful components such as phosphorus and fluorine, and obtain purified leachate; (4) Mix the PG-PS precipitate with biochar, red mud (RM), carbide slag (CS) and cement in a mixer until uniform. Then, add ultrapure water, stir until uniform, pour into a mold with air removed, cast and mold, and cure to prepare modified PG filling material.

[0008] Step (1) The solid-liquid ratio of phosphogypsum to ultrapure water is 1:4~10 g:mL.

[0009] Step (2) Grind the yellow phosphorus slag to a particle size of 200-300 mesh.

[0010] Step (2) The mass ratio of phosphogypsum to yellow phosphorus slag is (1-x):x, where x is 3~20%.

[0011] Step (3) The additives include CaCl2, CaO, La(NO3)3, and γ-Al2O3. The amount of additives added is 0.1-24% of phosphogypsum. Stir the reaction for 20-30 minutes.

[0012] In step (4), the mass ratio of PG-PS precipitate, biochar, RM, CS and cement is 70:1:16:8:5, and the solid-liquid ratio after adding ultrapure water is 5:3 g:mL.

[0013] Step (4) After casting for 1 day, demold the test block and place it under conditions of humidity >90% and temperature 20±2℃ for 28 days.

[0014] (1) This invention makes full use of the component characteristics of yellow phosphorus slag to synergistically treat phosphogypsum leachate, and then further treats it with chemical reagents to efficiently remove harmful components such as phosphorus and fluorine. The effluent quality meets the discharge requirements, realizing the harmless treatment of phosphogypsum leachate. At the same time, the separated precipitate is compounded with various solid wastes to prepare filling materials, which significantly improves the resource utilization rate of the treated products.

[0015] (2) The raw materials used in this invention are all industrial solid waste or conventional reagents, which realizes the high-value utilization of solid waste resources and has the advantages of easy process control, low cost and green environmental protection. Attached Figure Description

[0016] Figure 1 This is a graph showing the effect of CaCl2 on the phosphorus, fluorine and sulfate content in PG-PS leachate in Example 1; Figure 2 This is a graph showing the effect of CaO on the phosphorus, fluorine and sulfate content in PG-PS leachate in Example 2; Figure 3 This is a graph showing the effect of La(NO3)3 on the phosphorus, fluorine and sulfate content in PG-PS leachate in Example 3; Figure 4 This is a graph showing the effect of γ-Al2O3 on the phosphorus, fluorine and sulfate content in PG-PS leachate in Example 4. Detailed Implementation

[0017] The embodiments of the present invention will now be described in more detail with reference to specific examples. However, it should be understood that the present invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention will be more thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0018] This invention provides a method for the harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate. Phosphogypsum is weighed and mixed with ultrapure water, stirred evenly, and then yellow phosphorus slag is added. After mixing evenly, solid-liquid separation is performed to obtain PG-PS leachate and precipitate. Chemical additives are added to the PG-PS leachate to react and obtain purified leachate. At the same time, the PG-PS precipitate is mixed with biochar, RM, CS and cement according to the formula, and after adding water and stirring evenly, it is poured and cured to prepare modified PG filling material.

[0019] Example 1 Weigh 5g of fresh phosphogypsum, add 35mL of ultrapure water at a solid-liquid ratio of 1:7 (g:mL), and stir well to obtain PG suspension. According to the mass ratio of phosphogypsum to yellow phosphorus slag of 9.7:0.3, 0.155g of yellow phosphorus slag passing through a 250-mesh sieve was weighed and added to the PG suspension. After stirring and mixing evenly, solid-liquid separation was carried out to obtain PG-PS leachate and PG-PS precipitate. Add 0-400 mg of CaCl2 to the PG-PS leachate and stir for 25 min. Further treatment removes harmful components such as phosphorus and fluorine, yielding purified PG-PS leachate. Ion chromatography is used to detect phosphorus and fluorine in the purified PG-PS leachate. Figure 1 As shown in Table 1, with the increase of CaCl2 reagent, the phosphorus concentration in the leachate continued to decrease and then tended to stabilize, while the fluoride concentration first decreased and then slightly increased before finally stabilizing. The removal efficiency of CaCl2 reagent for phosphorus and fluoride reached 97.89% and 79.12%, respectively, and the fluoride removal amount was 0.61 mg / g.

[0020] Example 2 Following the method in Example 1, 0-400 mg of CaCl2 reagent was replaced with 0-400 mg of CaO reagent, while other parameters remained unchanged, resulting in purified PG-PS permeate. The phosphorus and fluorine levels in the purified PG-PS permeate were then detected using ion chromatography. Figure 2 As shown in Table 1, with the increase of CaO reagent addition, the phosphorus concentration in the leachate continued to decrease and then tended to stabilize, while the fluoride concentration decreased rapidly and remained at a low level. The removal efficiency of CaO reagent for phosphorus and fluoride reached 99.81% and 95.42%, respectively, and the fluoride removal amount was 8.97 mg / g.

[0021] Example 3 Following the method in Example 1, 0-400 mg of CaCl2 reagent was replaced with 0-50 mg of La(NO3)3 reagent, while other parameters remained unchanged. The purified PG-PS permeate was obtained, and the phosphorus and fluorine levels in the purified PG-PS permeate were detected using ion chromatography. Figure 3 As shown in Table 1, with the increase of the amount of La(NO3)3 reagent added, the phosphorus concentration in the leachate continued to decrease and then tended to stabilize, while the fluoride concentration decreased sharply and then gradually slowed down. The removal efficiency of La(NO3)3 reagent for phosphorus and fluoride reached 99.81% and 78.76%, respectively, and the amount of fluoride removed was 72.13 mg / g.

[0022] Example 4 Following the method in Example 1, 0-400 mg of CaCl2 reagent was replaced with 0-1200 mg of γ-Al2O3 reagent, while other parameters remained unchanged. The purified PG-PS permeate was obtained, and phosphorus and fluorine in the purified PG-PS permeate were detected using ion chromatography. Figure 4As shown in Table 1, with the increase of the amount of γ-Al2O3 reagent added, the phosphorus concentration in the leachate continued to decrease and then tended to stabilize, while the fluoride concentration first rose briefly, then fell rapidly, and finally tended to stabilize. The removal efficiency of γ-Al2O3 reagent for phosphorus and fluoride reached 99.81% and 96.87%, respectively, and the amount of fluoride removed was 8.64 mg / g.

[0023] The effects of different reagents on the harmless treatment of PG-PS leachate in Examples 1-4 are shown in Table 1.

[0024] Table 1. Effects of different chemical reagents on PG-PS leachate

[0025] As shown in Table 1, CaCl2 had the lowest removal efficiency for both phosphorus and fluoride. CaO, La(NO3)3, and γ-Al2O3 had similar removal efficiencies for phosphorus, all reaching 99.81%. CaO and γ-Al2O3 showed better removal efficiencies for fluoride, reaching 95.42% and 96.87%, respectively. The effluent quality met the discharge requirements. However, although La(NO3)3 showed a higher removal efficiency per unit of fluoride under trace conditions, its reagent cost was higher, limiting its economic viability compared to CaO.

[0026] Comparative Example 1 The difference between Comparative Example 1 and Examples 1-4 is that Comparative Example 1 does not involve the addition of additives. The specific steps are as follows: 5g of fresh phosphogypsum was weighed and added to 35mL of ultrapure water at a solid-liquid ratio of 1:7 (g:mL). After stirring evenly, a PG suspension was obtained. The mass ratio of phosphogypsum to yellow phosphorus residue was 9.7:0.3. 0.155g of yellow phosphorus residue that had passed through a 250-mesh sieve was weighed and added to the PG suspension. After stirring and mixing evenly, solid-liquid separation was performed to obtain PG-PS leachate and PG-PS precipitate. The phosphorus and fluorine in the PG-PS leachate were detected by ion chromatography, as shown in Table 2. The concentrations of phosphorus and fluorine were 21.82mg / L and 147.59mg / L, respectively.

[0027] Comparative Example 2 The difference between Comparative Example 2 and Comparative Example 1 is that Comparative Example 2 does not include the co-treatment of yellow phosphorus slag solid waste. The specific steps are as follows: 5g of fresh phosphogypsum was weighed and added to 35mL of ultrapure water at a solid-liquid ratio of 1:7 (g:mL). After stirring evenly, a PG suspension was obtained. The PG suspension was directly subjected to solid-liquid separation to obtain PG permeate and PG precipitate. The phosphorus and fluorine in the PG permeate were detected by ion chromatography, as shown in Table 2. The concentrations of phosphorus and fluorine were 184.40mg / L and 120.05mg / L, respectively.

[0028] Table 2. Phosphorus and fluorine content in Comparative Examples 1 and 2

[0029] In Comparative Example 2, the phosphorus and fluoride concentrations of the phosphogypsum leachate treated without the addition of yellow phosphorus slag were 184.40 mg / L and 129.05 mg / L, respectively. In Comparative Example 1, the phosphorus concentration of the PG-PS leachate treated with only yellow phosphorus slag decreased to 21.82 mg / L, with a phosphorus removal efficiency of 88.17%. However, the fluoride concentration increased from 120.05 mg / L to 147.59 mg / L, an increase of 22.94%. This is mainly because yellow phosphorus slag solid waste also contains harmful elements such as phosphorus and fluoride. The phosphorus and fluoride concentrations in the PG-PS leachate after co-treatment with yellow phosphorus slag alone are still high and do not meet the emission standards. Therefore, further advanced treatment is required.

[0030] Example 5 The resource utilization of the PG-PS precipitates obtained in Example 1 and Comparative Example 1 specifically includes the following steps: The PG-PS precipitate from Example 1, biochar (obtained by pyrolysis of tobacco straw at a heating rate of 20℃ / min to 500℃ for 2 hours under nitrogen atmosphere), red mud RM (a strongly alkaline industrial solid waste produced during the extraction of alumina from bauxite), carbide slag CS (a byproduct of acetylene production, mainly composed of calcium hydroxide), and cement were weighed in a mass ratio of 70:1:16:8:5 and mixed evenly in a mixer. Then, ultrapure water was added at a solid-liquid ratio of 5:3 g:mL. After stirring evenly, the mixture was poured into a mold with all air removed and cast. After casting for 1 day, the mold was removed, and the test block was cured for 28 days under conditions of humidity >90% and temperature 20±2℃ to prepare the modified PG filling material.

[0031] After curing, a compressive strength test was conducted, and crushed samples were taken for environmental characteristic evaluation. The leaching toxicity of the backfill material was determined using the "Solid Waste Toxicity Leaching Method - Reversal Method" (GB5086.1-1997), and the F in the leachate was tested using ion chromatography. - Concentration, results showed F - The leaching concentration was below 1.5 mg / L, indicating that the modification treatment of PG-PS precipitate by the present invention can effectively reduce F. - The concentration of the modified PG filling material prepared meets environmental safety requirements.

[0032] Furthermore, the engineering performance of the modified PG backfill material was evaluated. The setting time, softening coefficient, and unconfined compressive strength (UCS) were selected as indicators. Under optimal conditions, the setting time of the modified PG backfill material after 28 days of curing was 410 min, the softening coefficient was 0.79, and the UCS was 5.04 MPa. All performance indicators met the standards of the "Technical Specification for Backfill Engineering in Metal and Non-metal Mines" (GB / T51450-2022), which can effectively reduce the consumption of natural resources by mine backfilling.

[0033] Example 6 Weigh 5g of fresh phosphogypsum, add 20mL of ultrapure water at a solid-liquid ratio of g:mL of 1:4, and stir well to obtain PG suspension; According to the mass ratio of phosphogypsum to yellow phosphorus residue of 8:2, 1.25g of yellow phosphorus residue sieved through 200 mesh was weighed and added to PG suspension. After stirring and mixing evenly, solid-liquid separation was carried out to obtain PG-PS leachate and PG-PS precipitate. 100 mg of CaCl2 reagent was added to the PG-PS leachate and stirred for 20 min for further treatment to remove harmful components phosphorus and fluorine, resulting in purified PG-PS leachate with removal efficiencies of 97.27% and 79.05% for phosphorus and fluorine, respectively. PG-PS precipitate, biochar, RM, CS, and cement were weighed at a mass ratio of 70:1:16:8:5 and mixed evenly in a mixer. Then, ultrapure water was added at a solid-liquid ratio of 5:3 (g:mL). After stirring evenly, the mixture was poured into an air-removed mold and cast. After casting for 1 day, the mold was removed, and the test block was cured for 28 days under conditions of humidity >90% and temperature 20±2℃. Modified PG filling material was prepared. The test results showed that the filling material met the requirements for use in mining filling materials, thus realizing resource utilization.

[0034] Example 7 Weigh 5g of fresh phosphogypsum, add 50mL of ultrapure water at a solid-liquid ratio of 1:10 (g:mL), and stir well to obtain PG suspension. According to the mass ratio of phosphogypsum to yellow phosphorus slag of 9:1, 0.56g of yellow phosphorus slag sieved through 300 mesh was added to the PG suspension, stirred and mixed evenly, and then solid-liquid separation was carried out to obtain PG-PS leachate and PG-PS precipitate. 100 mg of CaCl2 reagent was added to the PG-PS leachate and stirred for 30 min for further treatment to remove harmful components phosphorus and fluorine, resulting in purified PG-PS leachate with removal efficiencies of 96.17% and 78.91% for phosphorus and fluorine, respectively. PG-PS precipitate, biochar, RM, CS, and cement were weighed at a mass ratio of 70:1:16:8:5 and mixed evenly in a mixer. Then, ultrapure water was added at a solid-liquid ratio of 5:3 (g:mL). After stirring evenly, the mixture was poured into an air-removed mold and cast. After casting for 1 day, the mold was removed, and the test block was cured for 28 days under conditions of humidity >90% and temperature 20±2℃. Modified PG filling material was prepared. The test results showed that the filling material met the requirements for use in mining filling materials, thus realizing resource utilization.

[0035] In summary, this invention achieves harmless treatment of PG-PS leachate, with phosphorus and fluoride pollutant removal rates reaching 99.81% and 96.87%, respectively, and the effluent quality meets discharge standards. Furthermore, the modified PG backfill material prepared using PG-PS precipitate possesses both good environmental safety and engineering applicability, realizing the dual utilization of pollution control and resource recovery for phosphogypsum and yellow phosphorus slag.

[0036] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for the harmless treatment and resource utilization of leachate from yellow phosphorus slag solid waste and phosphogypsum, characterized in that, The specific steps are as follows: (1) Weigh phosphogypsum and add it to ultrapure water. Stir well at room temperature to obtain PG suspension; (2) Add the ground yellow phosphorus residue to the suspension in step (1), stir and mix evenly, and then perform solid-liquid separation to obtain PG-PS leachate and PG-PS precipitate; (3) Add additives to the PG-PS leachate and stir to remove harmful components such as phosphorus and fluorine, and obtain purified leachate; (4) Mix the PG-PS precipitate with biochar, red mud, carbide slag and cement in a mixer, add ultrapure water, stir evenly, pour into a mold with air removed and cast into shape, and cure to prepare modified PG filling material.

2. The method for harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate according to claim 1, characterized in that, Step (1) The solid-liquid ratio of phosphogypsum to ultrapure water is 1:4~10 g:mL.

3. The method for harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate according to claim 1, characterized in that, Step (2) Grind the yellow phosphorus slag to a particle size of 200-300 mesh.

4. The method for harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate according to claim 1, characterized in that, Step (2) The mass ratio of phosphogypsum to yellow phosphorus slag is (1-x):x, where x is 3~20%.

5. The method for harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate according to claim 1, characterized in that, Step (3) The additives include CaCl2, CaO, La(NO3)3, and γ-Al2O3. The amount of additives added is 0~1200mg / 5g phosphogypsum. Stir the reaction for 20~30min.

6. The method for harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate according to claim 1, characterized in that, In step (4), the mass ratio of PG-PS precipitate, biochar, red mud, carbide slag, and cement is 70:1:16:8:5, and the solid-liquid ratio of ultrapure water added is 5:3 g:mL.

7. The method for harmless treatment and resource utilization of yellow phosphorus slag solid waste and phosphogypsum leachate according to claim 1, characterized in that, Step (4) After casting for 1 day, demold the test block and place it under conditions of humidity >90% and 20℃ for 28 days.

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