A porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum

Abstract

This invention provides a porous hydrogel for leaching phosphorus and fluorine from phosphogypsum. The porous hydrogel has a dual-network structure, comprising two layers. The first layer is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline. The second layer is formed by covalently bonding pullulan, which contains silver ions. The dual-network porous hydrogel prepared in this invention provides a larger specific surface area and more adsorption sites, thereby increasing the anion adsorption capacity and enabling efficient leaching of phosphorus and fluorine.

Description

Technical Field

[0001] This invention relates to the fields of hazardous waste treatment and water treatment, and particularly to a porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum. Background Technology

[0002] Phosphogypsum is a byproduct formed during the production of fertilizers, pesticides, and phosphoric acid. It is a grayish-white, loose, and relatively dry waste, typically containing abundant phosphates, uranium, nickel, and thorium. The main component of phosphogypsum is calcium sulfate dihydrate (CaSO4·2H2O), and it also contains small amounts of impurities, primarily phosphorus, fluorine, silicon dioxide, and organic matter.

[0003] Currently, common methods for extracting phosphorus and fluorine from phosphogypsum include lime neutralization, calcination, flotation, acid leaching, and sieving. Among these, water washing is simple to operate and has high impurity removal efficiency, making it an effective method for removing water-soluble phosphorus and fluorine from phosphogypsum. However, these commonly used methods have drawbacks to varying degrees, such as high energy consumption and cumbersome processes. Soluble phosphorus in phosphogypsum mainly exists as H3PO4 and H2PO4. - and HPO4 2- Phosphorus and fluoride exist in various forms, including fluorides and fluorophosphates. The presence of phosphorus and fluoride can be harmful to water bodies, soil, and human health, so it is necessary to extract phosphorus and fluoride from phosphogypsum. Summary of the Invention

[0004] Technical problem to be solved: The purpose of this invention is to provide a porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum, so as to achieve the purpose of efficient extraction of phosphorus and fluorine elements from phosphogypsum.

[0005] Technical solution:

[0006] A porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the porous hydrogel has a double-layer network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions.

[0007] Preferably, the method for preparing the porous hydrogel includes the following steps:

[0008] S1. Add the mixed clay to a 0.1-1 mol / L inorganic acid solution and react at 25-45℃ for 0.5-1 h to obtain acidified mixed clay;

[0009] S2. Mix and dissolve dimethyl diallyl ammonium chloride, crosslinking agent and water in a certain proportion, then add acidified composite clay, initiator and accelerator to react and obtain polydimethyl diallyl ammonium chloride liquid;

[0010] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 is freeze-polymerized at -20 to -10°C for 6 to 15 hours to obtain the initial hydrogel with the first layer network structure.

[0011] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. Then, the mixed sol was freeze-polymerized at -20 to -10℃ for 6 to 15 hours to obtain a porous hydrogel with a bilayer network structure.

[0012] Preferably, the mixed clay in S1 is montmorillonite and sodium nepheline, the mass ratio of montmorillonite to sodium nepheline is 1-5:1-3, the mass ratio of the mixed clay to the inorganic acid solution is 1:40-60, and the inorganic acid includes any one or more of nitric acid, hydrochloric acid, or sulfuric acid.

[0013] Preferably, the montmorillonite has a particle size of 300–600 nm and the nepheline has a particle size of 100–200 nm.

[0014] Preferably, the molar ratio of dimethyl diallyl ammonium chloride, crosslinking agent, water, acidified mixed clay, initiator and accelerator in S2 is 10-15: 2-4: 2-8: 5-9: 0.02-0.03: 0.01-0.03.

[0015] Preferably, in S2, the crosslinking agent is N,N'-methylenebisacrylamide, the initiator is one or both of potassium persulfate or ammonium persulfate, the accelerator is ethylenediaminetetraacetic acid, and the reaction temperature is 50-90°C for 6-10 hours.

[0016] Preferably, in step S4, the mass ratio of the initial hydrogel to the pullulan solution containing silver ions is 1:30-50, the mass ratio of the silver ions to pullulan is 1:2-4, and the silver ions are introduced by one or both of silver nitrate or silver sulfate.

[0017] Preferably, the concentration of pullulan polysaccharide solution containing metallic silver ions in S4 is 15-35 wt%.

[0018] Preferably, porous hydrogel is added to phosphogypsum wastewater to adsorb phosphorus and fluorine elements at room temperature for 30-60 minutes.

[0019] Preferably, the phosphorus concentration in the phosphogypsum wastewater is 200–400 mg / L, the fluorine concentration is 80–150 mg / L, the pH value is 3–9, and the amount of porous hydrogel added is 3000–5000 mg per liter of phosphogypsum wastewater.

[0020] Beneficial effects:

[0021] 1. In this invention, montmorillonite and nepheline are acidified. Acidification increases the interlayer spacing of montmorillonite, thereby increasing its specific surface area and enhancing its anion adsorption capacity. Furthermore, acidification also balances the vacancies of aluminum and iron regions in the nepheline lattice with metal ions (such as K+). + Or Na + When dissolved in acid, positively charged cavities are formed on the surface, which enhances its anion adsorption capacity and chemical activity. Furthermore, combining montmorillonite and sodium nepheline with different particle sizes can regulate the pore structure, which is beneficial for the adsorption of anions.

[0022] 2. In this invention, the first layer network structure obtained by the self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, montmorillonite, and sodium nepheline contains quaternary ammonium salt cationic groups. The quaternary ammonium salt cationic groups can achieve the adsorption of phosphorus ions and fluoride ions through chemical adsorption. Furthermore, the acidified montmorillonite and sodium nepheline have a high specific surface area, thereby achieving the leaching of phosphorus ions and fluoride ions through physical adsorption. The synergistic effect of physical adsorption and chemical adsorption jointly improves the leaching efficiency of phosphorus ions and fluoride ions.

[0023] 3. In this invention, the hydroxyl, carbonyl and hemiacetal hydroxyl groups of pullulan polysaccharide can form covalent bonds with the hydrogen atoms of polydimethyldiallylammonium chloride in the first network structure, thereby forming a second network structure. The second network structure contains metallic silver ions, which can form insoluble precipitates with phosphorus ions and fluoride ions, thereby achieving the leaching of phosphorus ions and fluoride ions.

[0024] 4. The porous hydrogel with a dual-network structure prepared in this invention can provide a larger specific surface area and more adsorption sites, thereby increasing the capacity for anion adsorption. It also has good water permeability, providing a fast channel for ions to diffuse from the solution into the hydrogel, thereby accelerating the adsorption rate. In addition, the porous hydrogel with a dual-network structure contains acidified montmorillonite and acidified sodium nepheline, which gives it good mechanical properties, thus endowing the porous hydrogel with a dual-network structure with stability and durability. Attached Figure Description Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments:

[0026] Example 1

[0027] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0028] The method for preparing the porous hydrogel includes the following steps:

[0029] S1. Montmorillonite and nepheline were added to a 0.1 mol / L nitric acid solution at a mass ratio of 1:1. The particle size of montmorillonite was 300 nm and the particle size of nepheline was 100 nm. The mass ratio of montmorillonite and nepheline to the inorganic acid solution was 1:40. The reaction was carried out at 25 °C for 0.5 h to obtain acidified composite clay.

[0030] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added. The mixture is reacted at 50°C for 6 hours. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 10:2:2:5:0.02:0.01 to obtain polydimethyl diallyl ammonium chloride liquid.

[0031] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -20°C for 6 hours to obtain the initial hydrogel with the first layer network structure;

[0032] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing silver ions was 1:30, the mass fraction of the pullulan polysaccharide solution containing silver ions was 15wt%, the mass ratio of silver ions to pullulan polysaccharide was 1:2, and the silver ions were introduced by silver nitrate solution. Then the mixed sol was freeze-polymerized at -20℃ for 6h to obtain a porous hydrogel with a double-layer network structure.

[0033] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 200 mg / L, a fluorine concentration of 80 mg / L, and a pH value of 3. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 30 minutes.

[0034] Example 2

[0035] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0036] The method for preparing the porous hydrogel includes the following steps:

[0037] S1. Montmorillonite and nepheline were added to a 0.1 mol / L nitric acid solution at a mass ratio of 5:3. The particle size of montmorillonite was 300 nm and the particle size of nepheline was 100 nm. The mass ratio of montmorillonite and nepheline to the inorganic acid solution was 1:40. The reaction was carried out at 25 °C for 0.5 h to obtain acidified composite clay.

[0038] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added. The mixture is reacted at 50°C for 6 hours. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 10:2:2:5:0.02:0.01 to obtain polydimethyl diallyl ammonium chloride liquid.

[0039] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -20°C for 6 hours to obtain the initial hydrogel with the first layer network structure;

[0040] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing silver ions was 1:30, the mass fraction of the pullulan polysaccharide solution containing silver ions was 15wt%, the mass ratio of silver ions to pullulan polysaccharide was 1:2, and the silver ions were introduced by silver nitrate solution. Then the mixed sol was freeze-polymerized at -20℃ for 6h to obtain a porous hydrogel with a double-layer network structure.

[0041] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 200 mg / L, a fluorine concentration of 80 mg / L, and a pH value of 3. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 30 minutes.

[0042] Example 3

[0043] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0044] The method for preparing the porous hydrogel includes the following steps:

[0045] S1. Montmorillonite and sodium nepheline were added to a 0.5 mol / L sulfuric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 600 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0046] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0047] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0048] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing metallic silver ions was 1:50, the mass fraction of the pullulan polysaccharide solution containing metallic silver ions was 35wt%, and the mass ratio of metallic silver ions to pullulan polysaccharide was 1:4. The metallic silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 15h to obtain a porous hydrogel with a double-layer network structure.

[0049] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 230 mg / L, a fluorine concentration of 90 mg / L, and a pH value of 3. The amount of porous hydrogel added is 4000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 60 min.

[0050] Example 4

[0051] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0052] The method for preparing the porous hydrogel includes the following steps:

[0053] S1. Montmorillonite and sodium nepheline were added to a 0.5 mol / L sulfuric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 600 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0054] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0055] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0056] S4. The initial hydrogel obtained in S3 was immersed in a pullulan polysaccharide solution containing silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing silver ions was 1:50, the mass fraction of the pullulan polysaccharide solution containing silver ions was 35wt%, and the mass ratio of silver ions to pullulan polysaccharide was 1:2. The silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 15h to obtain a porous hydrogel with a double-layer network structure.

[0057] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 240 mg / L, a fluorine concentration of 95 mg / L, and a pH value of 9. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 60 min.

[0058] Example 5

[0059] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0060] The method for preparing the porous hydrogel includes the following steps:

[0061] S1. Montmorillonite and sodium nepheline were added to a 0.5 mol / L sulfuric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 600 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0062] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0063] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0064] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing metallic silver ions was 1:50, the mass fraction of the pullulan polysaccharide solution containing metallic silver ions was 35wt%, the mass ratio of metallic silver ions to pullulan polysaccharide was 1:3, and the metallic silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 15h to obtain a porous hydrogel with a double-layer network structure.

[0065] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 240 mg / L, a fluorine concentration of 95 mg / L, and a pH value of 9. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 60 min.

[0066] Example 6

[0067] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0068] The method for preparing the porous hydrogel includes the following steps:

[0069] S1. Montmorillonite and sodium nepheline were added to a 0.5 mol / L sulfuric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 600 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0070] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0071] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0072] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing metallic silver ions was 1:50, the mass fraction of the pullulan polysaccharide solution containing metallic silver ions was 35wt%, and the mass ratio of metallic silver ions to pullulan polysaccharide was 1:4. The metallic silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 15h to obtain a porous hydrogel with a double-layer network structure.

[0073] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 240 mg / L, a fluorine concentration of 95 mg / L, and a pH value of 9. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 60 min.

[0074] Example 7

[0075] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0076] The method for preparing the porous hydrogel includes the following steps:

[0077] S1. Montmorillonite and sodium nepheline were added to a 0.5 mol / L sulfuric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 600 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0078] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0079] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0080] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing metallic silver ions was 1:50, the mass fraction of the pullulan polysaccharide solution containing metallic silver ions was 35wt%, the mass ratio of metallic silver ions to pullulan polysaccharide was 1:3, and the metallic silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 15h to obtain a porous hydrogel with a double-layer network structure.

[0081] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 260 mg / L, a fluorine concentration of 100 mg / L, and a pH value of 5. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 60 min.

[0082] Example 8

[0083] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0084] The method for preparing the porous hydrogel includes the following steps:

[0085] S1. Montmorillonite and sodium nepheline were added to a 0.8 mol / L hydrochloric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 500 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0086] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0087] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0088] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing metallic silver ions was 1:45, the mass fraction of the pullulan polysaccharide solution containing metallic silver ions was 35wt%, and the mass ratio of metallic silver ions to pullulan polysaccharide was 1:4. The metallic silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 12h to obtain a porous hydrogel with a double-layer network structure.

[0089] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a phosphorus concentration of 240 mg / L, a fluorine concentration of 120 mg / L, and a pH value of 6. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature for 40 min.

[0090] Comparative Example 1

[0091] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0092] The method for preparing the porous hydrogel includes the following steps:

[0093] S1. Montmorillonite and nepheline were added to a 0.1 mol / L nitric acid solution at a mass ratio of 6:7. The particle size of montmorillonite was 300 nm, the particle size of nepheline was 100 nm, and the mass ratio of montmorillonite and nepheline to the inorganic acid solution was 1:40. The reaction was carried out at 25 °C for 0.5 h to obtain acidified composite clay.

[0094] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added. The mixture is reacted at 50°C for 6 hours. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 10:2:2:5:0.02:0.01 to obtain polydimethyl diallyl ammonium chloride liquid.

[0095] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -20°C for 6 hours to obtain the initial hydrogel with the first layer network structure;

[0096] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing silver ions was 1:30, the mass fraction of the pullulan polysaccharide solution containing silver ions was 15wt%, the mass ratio of silver ions to pullulan polysaccharide was 1:2, and the silver ions were introduced by silver nitrate solution. Then the mixed sol was freeze-polymerized at -20℃ for 6h to obtain a porous hydrogel with a double-layer network structure.

[0097] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a concentration of 80 mg / L and a pH value of 3. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature, and the adsorption time is 30 min.

[0098] Table 1. Effect of different mass ratios of montmorillonite to nepheline on elemental leaching efficiency

[0099]

[0100]

[0101] Comparative Example 2

[0102] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0103] The method for preparing the porous hydrogel includes the following steps:

[0104] S1. Montmorillonite and sodium nepheline were added to a 0.5 mol / L sulfuric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 600 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0105] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0106] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0107] S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing metallic silver ions was 1:50, the mass fraction of the pullulan polysaccharide solution containing metallic silver ions was 35wt%, and the mass ratio of metallic silver ions to pullulan polysaccharide was 1:4. The metallic silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 15h to obtain a porous hydrogel with a double-layer network structure.

[0108] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a concentration of 150 mg / L and a pH value of 9. The amount of porous hydrogel added is 4000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature, and the adsorption time is 60 min.

[0109] Table 2. Effects of different mass ratios of montmorillonite and sodium nepheline to inorganic acid solution on elemental leaching efficiency.

[0110]

[0111] Comparative Example 3

[0112] The difference between this comparative example and Examples 1, 2 and 3 is that neither montmorillonite nor sodium nepheline has been acidified.

[0113] Table 3. Effects of different mass ratios of montmorillonite and nepheline to inorganic acid solution on elemental leaching efficiency.

[0114]

[0115] Comparative Example 4

[0116] The difference between this comparative example and Examples 4, 5 and 6 is that no metallic silver ions were added.

[0117] Table 4. Effect of the mass ratio of silver ions to pullulan on elemental leaching efficiency.

[0118]

[0119] Comparative Example 5

[0120] The difference between this comparative example and Example 7 is that no second-layer network structure was generated.

[0121] Table 5. Effect of the number of network structure layers on element leaching efficiency

[0122]

[0123] Comparative Example 6

[0124] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0125] The method for preparing the porous hydrogel includes the following steps:

[0126] S1. Montmorillonite and sodium nepheline were added to a 0.8 mol / L hydrochloric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 500 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0127] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0128] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0129] S4. The initial hydrogel obtained in S3 was immersed in a pullulan solution containing silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan solution containing silver ions was 1:20, the mass fraction of the pullulan solution containing silver ions was 35wt%, and the mass ratio of silver ions to pullulan was 1:4. The silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 12h to obtain a porous hydrogel with a double-layer network structure.

[0130] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a concentration of 100 mg / L and a pH value of 6. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature, and the adsorption time is 40 min.

[0131] Comparative Example 7

[0132] A porous hydrogel for extracting phosphorus and fluorine from phosphogypsum, characterized in that: the porous hydrogel is a porous hydrogel with a double network structure, wherein the first network structure is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline, and the second network structure is obtained by pullulan polysaccharide through covalent bonding, wherein the pullulan polysaccharide contains metallic silver ions;

[0133] The method for preparing the porous hydrogel includes the following steps:

[0134] S1. Montmorillonite and sodium nepheline were added to a 0.8 mol / L hydrochloric acid solution at a mass ratio of 4:3. The particle size of montmorillonite was 500 nm and the particle size of sodium nepheline was 200 nm. The mass ratio of montmorillonite and sodium nepheline to the inorganic acid solution was 1:60. The reaction was carried out at 45 °C for 1 h to obtain acidified composite clay.

[0135] S2. Dimethyl diallyl ammonium chloride, crosslinking agent and water are thoroughly mixed and dissolved, and then acidified composite clay, N,N'-methylenebisacrylamide, potassium persulfate and ethylenediaminetetraacetic acid are added and reacted at 90°C for 10 h. The molar ratio of dimethyl diallyl ammonium chloride, N,N'-methylenebisacrylamide, water, acidified composite clay, potassium persulfate and ethylenediaminetetraacetic acid is 15:4:8:9:0.03:0.03 to obtain polydimethyl diallyl ammonium chloride liquid;

[0136] S3. The polydimethyldiallylammonium chloride liquid obtained in S2 was freeze-polymerized at -10℃ for 15h to obtain the initial hydrogel with the first layer network structure;

[0137] S4. The initial hydrogel obtained in S3 was immersed in a pullulan polysaccharide solution containing silver ions and ultrasonically dispersed. The mass ratio of the initial hydrogel to the pullulan polysaccharide solution containing silver ions was 1:60, the mass fraction of the pullulan polysaccharide solution containing silver ions was 35wt%, and the mass ratio of silver ions to pullulan polysaccharide was 1:4. The silver ions were introduced by silver sulfate solution. Then the mixed sol was freeze-polymerized at -10℃ for 12h to obtain a porous hydrogel with a double-layer network structure.

[0138] The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum is as follows: the porous hydrogel is added to phosphogypsum wastewater with a concentration of 100 mg / L and a pH value of 6. The amount of porous hydrogel added is 3000 mg per liter of phosphogypsum wastewater, which adsorbs phosphorus and fluorine elements at room temperature, and the adsorption time is 40 min.

[0139] Table 6. Effect of different initial hydrogel and pullulan polysaccharide solution containing silver ions on element leaching efficiency.

[0140]

[0141] Comparative Example 8

[0142] The difference between this comparative example and Example 8 is that montmorillonite was not added.

[0143] Comparative Example 9

[0144] The difference between this comparative example and Example 8 is that sodium nepheline was not added.

[0145] Table 7 shows the effect of the type of clay added on the element leaching effect.

[0146]

[0147] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum, characterized in that: The porous hydrogel is a porous hydrogel with a dual-network structure. The porous hydrogel has a double-layer network structure, wherein the first network structure is the inner layer, which is obtained by self-polymerization and cross-linking of dimethyl diallyl ammonium chloride, acidified montmorillonite, and acidified sodium nepheline; the second network structure is the outer layer, which is obtained by pullulan polysaccharide through covalent bonding, and the pullulan polysaccharide contains metallic silver ions.

2. The method for preparing a porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum according to claim 1, characterized in that: The method for preparing the porous hydrogel includes the following steps: S1. Montmorillonite and sodium nepheline are added to an inorganic acid solution of 0.1~1 mol / L and reacted at 25~45℃ for 0.5~1 h to obtain acidified mixed clay; S2. Mix and dissolve dimethyl diallyl ammonium chloride, crosslinking agent and water in a certain proportion, then add acidified composite clay, initiator and accelerator to react and obtain polydimethyl diallyl ammonium chloride liquid; S3. The polydimethyldiallylammonium chloride liquid obtained in S2 is freeze-polymerized at -20~-10℃ for 6~15h to obtain the initial hydrogel with the first layer network structure; S4. The initial hydrogel obtained in S3 was immersed in pullulan polysaccharide solution containing metallic silver ions and ultrasonically dispersed. Then, the mixed sol was freeze-polymerized at -20~-10℃ for 6~15h to obtain a porous hydrogel with a double-layer network structure.

3. The method for preparing porous hydrogels for extracting phosphorus and fluorine elements from phosphogypsum according to claim 2, characterized in that: The mass ratio of montmorillonite to nepheline in S1 is 1~5:1~3, and the mass ratio of montmorillonite and nepheline to the inorganic acid solution is 1:40~60. The inorganic acid includes any one or more of nitric acid, hydrochloric acid, or sulfuric acid.

4. The method for preparing a porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum according to claim 3, characterized in that: The montmorillonite has a particle size of 300-600 nm, and the nepheline has a particle size of 100-200 nm.

5. The method for preparing a porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum according to claim 2, characterized in that: The molar ratio of dimethyl diallyl ammonium chloride, crosslinking agent, water, acidified mixed clay, initiator and accelerator in S2 is 10~15:2~4:2~8:5~9:0.02~0.03:0.01~0.

03.

6. The method for preparing a porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum according to claim 2, characterized in that: The crosslinking agent in S2 is N,N'-methylenebisacrylamide, the initiator is one or both of potassium persulfate or ammonium persulfate, and the accelerator is ethylenediaminetetraacetic acid. The reaction temperature is 50~90℃ and the time is 6~10h.

7. The method for preparing a porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum according to claim 2, characterized in that: The mass ratio of the initial hydrogel and the pullulan polysaccharide solution containing silver ions in S4 is 1:30~50, the mass ratio of silver ions to pullulan polysaccharide is 1:2~4, and the silver ions are introduced by one or both of silver nitrate or silver sulfate.

8. The method for preparing porous hydrogels for extracting phosphorus and fluorine elements from phosphogypsum according to claim 2, characterized in that: The concentration of pullulan polysaccharide solution containing metallic silver ions in S4 is 15~35wt%.

9. The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum according to claim 1, characterized in that: Porous hydrogels were added to phosphogypsum wastewater to adsorb phosphorus and fluorine elements at room temperature for 30-60 minutes.

10. The method of using the porous hydrogel for extracting phosphorus and fluorine elements from phosphogypsum according to claim 9, characterized in that: The phosphorus concentration in the phosphogypsum wastewater is 200-400 mg / L, the fluorine concentration is 80-150 mg / L, the pH value is 3-9, and the porous hydrogel is added at a rate of 3000-5000 mg per liter of phosphogypsum wastewater.

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