Method for separating chlorophosphonate from chlorophosphonate-ammonium chlorophosphonate mixture by using anion membrane

Abstract

This invention discloses a method for separating chlorine and phosphorus from a mixture of chlorophosphoric acid and ammonium chlorophosphate using an anion exchange membrane. The method includes the following steps: adding hydrochloric acid to a low-grade phosphate rock slurry for decomposition to obtain a calcium-containing chlorophosphoric acid solution; adding a decalcifying agent to the calcium-containing chlorophosphoric acid solution to remove calcium salts from the chlorophosphoric acid, resulting in a mixed solution of chlorophosphoric acid and ammonium chlorophosphate; and performing membrane separation of the mixed solution using an anion exchange membrane. After separation, ammonium chlorate or phosphoric acid solution is obtained on the feed side, and hydrochloric acid with a mass concentration of 15-30% is obtained on the water side. This invention utilizes a simple anion exchange membrane to treat the mixed solution of chlorophosphoric acid and ammonium chlorophosphate, removing chloride ions from the mixed solution, making the high-value utilization of phosphorus in the mixed solution possible, and providing a possibility for the high-value promotion of the hydrochloric acid decomposition process for low-grade phosphate rock.

Description

Technical Field

[0001] This invention belongs to the field of chemical production, and specifically relates to a method for separating chlorine and phosphorus in a mixture of chlorophosphoric acid and ammonium chlorophosphate using anion exchange membranes. Background Technology

[0002] In my country, the sulfur-based fertilizer and chlor-alkali industries produce large quantities of hydrochloric acid that is difficult to utilize. However, using hydrochloric acid to decompose phosphate rock is an effective way to ensure the normal utilization of low-grade phosphate rock in the future. However, the chlorine and phosphorus elements in the chlorophosphoric acid or chlorophosphine ammonium solution obtained after decalcification during the hydrochloric acid decomposition of phosphate rock are difficult to separate. Chlorophosphoric acid or chlorophosphine ammonium solution can only be used to produce chlorine-based fertilizers. The value of chlorine-based fertilizers is far lower than that of sulfur-based fertilizers or phosphate ammonium, and they cannot be used in many crops such as tobacco. Currently, the commonly used separation methods are cooling chlorophosphoric acid to crystallize calcium chloride, or heating the system to volatilize hydrogen chloride. Both methods are characterized by high energy consumption, high corrosiveness, large equipment investment, and high cost, and large-scale production facilities are not currently available. Therefore, how to remove chlorine from chlorophosphoric acid or chlorophosphine ammonium solution has become a major challenge in the hydrochloric acid decomposition of phosphate rock process, limiting its large-scale application. Summary of the Invention

[0003] This invention addresses the problem of separating chlorine and phosphorus in hydrochloric acid decomposition of low-grade phosphate rock chlorophosphoric acid or ammonium chlorophosphate solution in the prior art, and aims to provide a method for separating chlorine and phosphorus in a mixture of hydrochloric acid and ammonium chlorophosphate using anion exchange membranes.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for separating chlorine and phosphorus from a mixture of chlorophosphoric acid and ammonium chlorophosphate using an anion exchange membrane includes the following steps:

[0006] Hydrochloric acid is added to low-grade phosphate rock slurry to decompose it and obtain a calcium-containing chlorophosphoric acid solution. A decalcifying agent is added to the calcium-containing chlorophosphoric acid solution to remove the calcium salt from the chlorophosphoric acid, resulting in a mixed solution of chlorophosphoric acid and ammonium chlorophosphoric acid.

[0007] A mixed solution of chlorophosphoric acid and ammonium chlorophosphate is separated by an anion exchange membrane. After separation, ammonium phosphate or phosphoric acid solution is obtained on the feed side, and hydrochloric acid with a mass concentration of 15-30% is obtained on the water side.

[0008] Furthermore, when hydrochloric acid is added to low-grade phosphate rock slurry, the molar ratio of CaO to hydrochloric acid in the phosphate rock is 1:1.9, the decomposition temperature is 40-75℃, and the time is 2-8h.

[0009] Furthermore, the grade of low-grade phosphate rock is 16-24%.

[0010] Furthermore, the decalcifying agent is ammonium sulfate or sulfuric acid.

[0011] Furthermore, the molar ratio of the decalcifying agent to calcium ions in chlorophosphoric acid is 1.0-1.1:1.

[0012] Furthermore, the hydrochloric acid concentration is 20-33%.

[0013] Furthermore, the removal of calcium salts from chlorophosphoric acid is carried out at a temperature of 40-75℃ for 2-8 hours.

[0014] Furthermore, the mixed solution of chlorophosphoric acid and ammonium chlorophosphate was subjected to membrane separation via anion exchange membrane at 35-90°C.

[0015] Furthermore, the preparation method of the anion exchange membrane is as follows: the anion membrane material is dissolved in an organic solvent, and after complete dissolution, it is ultrasonically degassed and allowed to stand to obtain a casting solution; the base membrane is fully impregnated in the organic solvent, and then the base membrane is transferred to the casting solution for full impregnation; the impregnated base membrane is fixed on a polytetrafluoroethylene plate, and then the base membrane is coated by scraping, and then placed in an oven to dry to obtain an anion exchange membrane.

[0016] Furthermore, the molecular weight of the anion exchange membrane material is 50,000 to 150,000; the base membrane is preferably at least one of PVDF membrane, PTFE membrane, PP membrane, nylon mesh and PP mesh, wherein the pore size of PVDF membrane, PTFE membrane and PP membrane is 0.22μm to 30μm, and the mesh number of nylon mesh and PP mesh is 100 to 400 mesh.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This invention utilizes an anion exchange membrane to effectively separate chlorine and phosphorus in a mixed solution of chlorophosphoric acid and ammonium chlorophosphate, producing high-purity hydrochloric acid. This overcomes the biggest application challenge in the decomposition of low-grade phosphate rock with hydrochloric acid, expanding the application scope and value of the mixed solution and enabling high-value utilization of low-grade phosphate rock. It effectively protects my country's phosphate resources and provides a new method for separating chlorine and phosphorus in the mixed solution. This invention can effectively reduce production costs for manufacturing enterprises and promote the widespread implementation of hydrochloric acid decomposition of low-grade phosphate rock. Attached Figure Description

[0019] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0020] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0021] See Figure 1 The present invention discloses a method for separating chlorine and phosphorus from a chlorophosphate (ammonium) mixture using an anion exchange membrane, comprising the following steps:

[0022] (a) Add a decalcifying agent to the chlorophosphoric acid obtained by hydrochloric acid decomposition of low-grade phosphate rock, decompose it, remove the calcium salt in the chlorophosphoric acid, and obtain an acidic chlorophosphoric acid (ammonium) mixed solution.

[0023] The preferred concentration of hydrochloric acid is 20-33%, the preferred decomposition temperature is 40-75℃, the preferred decomposition time is 2-8h, and the preferred grade of phosphate rock is 16-24%. The preferred decalcifying agent is ammonium sulfate or sulfuric acid (sulfuric acid concentration is 10-98%), and the molar ratio of the decalcifying agent to calcium ions in chlorophosphoric acid is 1.0-1.1:1.

[0024] (b) The obtained chlorophosphate (ammonium) mixed solution is separated by anion exchange membrane at a temperature of 35-90°C. The remaining ammonium phosphate (or phosphoric acid) solution on the raw material side after separation is used for monoammonium phosphate production; hydrochloric acid with a mass concentration of 15-30% is obtained on the water side and returned to the hydrochloric acid decomposition phosphate rock unit.

[0025] The anion exchange membrane is prepared as follows: the anion membrane material is dissolved in an organic solvent, and after complete dissolution, it is ultrasonically degassed for 5-30 minutes and allowed to stand for 1-2 hours to obtain a casting solution; the base membrane is fully impregnated in the organic solvent, and then the base membrane is transferred to the casting solution for full impregnation; the impregnated base membrane is fixed on a polytetrafluoroethylene plate, and then the base membrane is coated by scraping, and then placed in an oven to dry for 5-7 hours to obtain an anion exchange membrane with a thickness of 120-200 μm.

[0026] The base film is preferably at least one of PVDF film, PTFE film, PP film, nylon mesh and PP mesh, wherein the pore size of PVDF film, PTFE film and PP film is 0.22μm to 30μm, and the mesh number of nylon mesh and PP mesh is 100 to 400 mesh.

[0027] The viscosity of the casting solution at 25°C is 10,000–20,000 mPa·s;

[0028] The purity of the anion exchange membrane material is >95%, and the molecular weight is 50,000 to 150,000, preferably around 70,000 to 140,000.

[0029] The mass ratio of the anion exchange membrane material to the organic solvent is 1:1 to 9;

[0030] The organic solvent is preferably dimethyl sulfoxide, 2-pyrrolidone, N,N-dimethylformamide, or N,N-dimethylacetamide.

[0031] The preferred anion exchange membrane is a cyclic ammonium phenolphthalein polyarylether sulfone membrane material. This cyclic ammonium phenolphthalein polyarylether sulfone membrane material is prepared through the following process: Under nitrogen protection, cyclic ammonium phenolphthalein, 4,4-difluorodiphenyl sulfone, biphenyl phenol, a basic compound, DMSO, and toluene are added to a reaction flask and refluxed at 140°C for 8 hours. After reflux, toluene and water are removed by azeotropic distillation. The reaction is then carried out at 180°C for 12 hours to obtain a viscous polymerization solution. After cooling to room temperature, DMSO is added for dilution, the solid is filtered off, and the solution is poured into water at 70°C to obtain the polymer product. The polymer product is then vacuum-dried at 120°C for 20–28 hours to obtain a PES-PPH-Pi polymer. The PES-PPH-Pi polymer is dissolved in DMSO, and iodomethane (twice the molar amount of amino groups in the PES-PPH-Pi polymer) is added. The mixture is stirred at room temperature for 6–8 hours, then precipitated in ethanol to obtain the polymer. After filtration, the polymer is vacuum-dried at 80°C for 24 hours to obtain the anion exchange membrane material.

[0032] The cyclic ammonium phenolphthalein structure is shown in formula (1):

[0033]

[0034] In formula (1), the R group is a nitrogen-containing heterocycle, preferably piperidinyl, tetrahydropyrroleyl or morpholinyl;

[0035] The alkaline compound is preferably sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, magnesium hydroxide, barium carbonate, or barium hydroxide.

[0036] The following are specific examples.

[0037] Example 1

[0038] Preparation of membrane material: A 500 mL three-necked flask was purged with nitrogen and fitted with a condenser and a water separator. 11.7 mmol piperidinium cycloammonium phenolphthalein (PPH-Pi), 14.6 mmol 4,4-difluorodiphenyl sulfone, 2.9 mmol biphenyl hydroquinone, 43.8 mmol K₂CO₃, 46 mL DMSO, and 6 mL toluene were added. The mixture was refluxed at 140 °C for 8 h. After reflux, the toluene and water were removed by azeotropic distillation. The mixture was then reacted at 180 °C for 12 h to obtain a viscous polymerization solution. After cooling to room temperature, 100 mL of [the solution] was added... The solid was filtered off by diluting the product with DMSO and then poured into water at 70°C to obtain the polymer product. The polymer was then vacuum dried at 120°C for 20 hours and then dissolved in DMSO. Iodomethane with twice the molar amount of amino groups in the polymer was added. The mixture was stirred at room temperature for 6 hours, and the polymer was precipitated in ethanol. After filtration, the polymer was vacuum dried at 80°C for 24 hours to obtain the cyclic ammonium phenolphthalein polyarylene ether sulfone membrane, i.e., the iodinated membrane material PES-PPH-Pi, with a molecular weight of approximately 70,000.

[0039] Preparation of the anion exchange membrane: 2g of iodinated membrane material PES-PPH-Pi with a piperidinyl R group was dissolved in 8g of DMSO and stirred for 3 hours until completely dissolved. The solution was then ultrasonically degassed for 10 minutes and allowed to stand for 1 hour to obtain the casting solution. A 0.22μm PP base membrane was thoroughly immersed in the DMSO solution to remove air bubbles. The 0.22μm PP base membrane was then immersed in the prepared casting solution. The immersed 0.22μm PP base membrane was laid flat on a polytetrafluoroethylene (PTFE) plate and rolled with a roller to ensure a tight bond between the base membrane and the casting solution, eliminating air bubbles. The PTFE plate was transferred to a 70℃ oven and dried for 7 hours to obtain an anion exchange membrane (150μm thick). The anion exchange membrane was repeatedly rinsed in deionized water and then immersed in deionized water for later use.

[0040] Hydrochloric acid with a mass concentration of 31% was added dropwise to the phosphate rock slurry (24% grade), and decomposed at 75°C (the molar ratio of CaO to hydrochloric acid in the phosphate rock was 1:1.9). After 2 hours, the undecomposed silica slag was removed by filtration, yielding a calcium-containing chlorophosphoric acid solution. Ammonium sulfate (the molar ratio of ammonium sulfate to calcium ions was 1.05:1) was added to the chlorophosphoric acid solution, and the reaction was stirred for 1 hour. After aging and crystallization for 2 hours, the solution was filtered to obtain a mixed solution of calcium sulfate and ammonium chlorophosphoric acid. At this point, the phosphorus yield was 98%, the chloride ion mass concentration in the ammonium chlorophosphoric acid solution was 20%, and the phosphorus pentoxide mass concentration was 10%.

[0041] A mixed solution of calcium sulfate and chlorophosphate was added to the feed side of the anion exchange membrane cell, and water was added to the product side of the cell for automatic diffusion. After 5 hours, hydrochloric acid with a mass concentration of 15% was obtained on the water side, while the feed side was an ammonium phosphate solution (chloride ion mass concentration less than 1%).

[0042] The separation efficiency of chlorine in this embodiment is 98.4%.

[0043] Example 2

[0044] Preparation of membrane material: A 500 mL three-necked flask was purged with nitrogen and fitted with a condenser and a water separator. 12.1 mmol of morpholinocycloammonium phenolphthalein (PPH-Mor), 14.6 mmol of 4,4-difluorodiphenyl sulfone, 3.1 mmol of biphenyl phenol, 88 mmol of potassium hydroxide, 46 mL of DMSO, and 6 mL of toluene were added. The mixture was refluxed at 140 °C for 6 h. After reflux, the toluene and water were removed by azeotropic distillation. The mixture was then reacted at 180 °C for 12 h to obtain a viscous polymerization solution. After cooling to room temperature, 120 mL of DMSO was added for dilution, the solid was filtered off, and the solution was poured into water at 70 °C to obtain the polymer product. The polymer was vacuum dried at 120 °C for 28 h, then dissolved in DMSO. Iodomethane with a molar amount twice that of the amino group in the polymer was added. The mixture was stirred at room temperature for 8 h, precipitated in ethanol, filtered, and vacuum dried at 80 °C for 24 h to obtain the iodinated membrane material PES-PPH-Mor, with a molecular weight of approximately 85,000.

[0045] Preparation of the anion exchange membrane: PES-PPH-Mor (3g), a membrane material with a morpholino group (R group), was dissolved in 10g of 2-pyrrolidone. The mixture was stirred for 5 hours until completely dissolved, followed by ultrasonic degassing for 20 minutes and standing for 2 hours to obtain the casting solution. A 0.22μm PVDF base membrane was thoroughly immersed in the 2-pyrrolidone solution to remove air bubbles. Then, the 0.22μm PVDF base membrane was immersed in the prepared casting solution. The immersed 0.22μm PVDF base membrane was laid flat on a polytetrafluoroethylene (PTFE) plate and rolled with a roller to ensure a tight bond between the base membrane and the casting solution, eliminating air bubbles. The PTFE plate was transferred to a 70℃ oven and dried for 7 hours to obtain an anion exchange membrane (120μm thick). The anion exchange membrane was repeatedly rinsed in deionized water and then immersed in deionized water for later use.

[0046] 31% hydrochloric acid was added dropwise to the phosphate rock slurry (16% grade), and the mixture was decomposed at 75°C (the molar ratio of CaO to hydrochloric acid in the phosphate rock was 1:1.9). After 3 hours, the undecomposed silica slag was removed by filtration, yielding a calcium-containing chlorophosphoric acid solution. Sulfuric acid (molar ratio of sulfuric acid to calcium ions was 1.05:1) was added to the chlorophosphoric acid solution, and the mixture was stirred for 1 hour. After aging and crystallization for 2 hours, the mixture was filtered to obtain a mixed solution of calcium sulfate and chlorophosphoric acid. At this point, the phosphorus yield was 96%, the chloride ion concentration in the chlorophosphoric acid solution was 15%, and the phosphorus pentoxide concentration was 9%.

[0047] A mixed solution of calcium sulfate and chlorophosphate was added to the feed side of the anion exchange membrane cell, and water was added to the product side of the cell for automatic diffusion. After 5 hours, hydrochloric acid with a mass concentration of 20% was obtained on the water side, while ammonium phosphate solution (chloride ion mass concentration less than 1%) was obtained on the feed side.

[0048] The separation efficiency of chlorine in this embodiment is 98%.

[0049] Example 3

[0050] Preparation of membrane material: A 500 mL three-necked flask was purged with nitrogen and fitted with a condenser and a water separator. 11.5 mmol tetrahydropyrrolidone cycloammonium phenolphthalein (PPH-Py), 14.6 mmol 4,4-difluorodiphenyl sulfone, 3.3 mmol biphenyl phenol, 88 mmol sodium hydroxide, 46 mL DMSO, and 6 mL toluene were added. The mixture was refluxed at 140 °C for 7 h. After reflux, the toluene and water were removed by azeotropic distillation. The mixture was then reacted at 180 °C for 12 h to obtain a viscous polymerization solution. After cooling to room temperature, 115 mL DMSO was added for dilution, the solid was filtered off, and the solution was poured into water at 70 °C to obtain the polymer product. The polymer was vacuum dried at 120 °C for 28 h, then dissolved in DMSO. Iodomethane with a molar amount twice that of the amino group in the polymer was added. The mixture was stirred at room temperature for 8 h, precipitated in ethanol, filtered, and vacuum dried at 80 °C for 24 h to obtain the iodinated membrane material PES-PPH-Py, with a molecular weight of approximately 140,000.

[0051] Preparation of the anion exchange membrane: 5g of PES-PPH-Py membrane material with a tetrahydropyrrole group (R group) was dissolved in 20g of DMSO and stirred for 3 hours until completely dissolved. The solution was then ultrasonically degassed for 30 minutes and allowed to stand for 2 hours to obtain the casting solution. A 0.22μm PP base membrane was thoroughly immersed in the DMSO solution to remove air bubbles. The 0.22μm PP base membrane was then immersed in the prepared casting solution. The immersed 0.22μm PP base membrane was laid flat on a polytetrafluoroethylene (PTFE) plate and rolled with a roller to ensure a tight bond between the base membrane and the casting solution, eliminating air bubbles. The PTFE plate was transferred to a 70℃ oven and dried for 5 hours to obtain an anion exchange membrane (200μm thick). The anion exchange membrane was repeatedly rinsed in deionized water and then immersed in deionized water for later use.

[0052] 20% hydrochloric acid was added dropwise to the phosphate rock slurry (20% grade), and decomposed at 75°C (the molar ratio of CaO to hydrochloric acid in the phosphate rock was 1:1.9). After 2 hours, the undecomposed silica slag was removed by filtration, and a calcium-containing chlorophosphoric acid solution was obtained. Ammonium sulfate (the molar ratio of ammonium sulfate to calcium ions was 1:1) was added to the chlorophosphoric acid solution, and the reaction was stirred for 1 hour. After aging and crystallization for 2 hours, a mixed solution of calcium sulfate and chlorophosphoric acid was obtained by filtration.

[0053] A mixed solution of calcium sulfate and chlorophosphoric acid was added to the feed side of the anion exchange membrane cell, and water was added to the product side of the cell. Automatic diffusion was carried out at 35°C. After 5 hours, hydrochloric acid was obtained on the water side, and ammonium phosphate solution was obtained on the feed side.

[0054] Example 4

[0055] Preparation of membrane material: Same as in Example 1;

[0056] Preparation of the anion exchange membrane: 1 g of iodinated membrane material PES-PPH-Pi with a piperidinyl R group was dissolved in 9 g of DMSO and stirred for 3 h until completely dissolved. The solution was then ultrasonically degassed for 5 min and allowed to stand for 1.5 h to obtain the casting solution. A 30 μm PTFE membrane was thoroughly immersed in the DMSO solution to remove air bubbles from the base membrane. The PTFE membrane was then immersed in the prepared casting solution. The immersed PTFE membrane was laid flat on a polytetrafluoroethylene (PTFE) plate and rolled with a roller to ensure a tight bond between the base membrane and the casting solution, eliminating air bubbles. The PTFE plate was transferred to a 70 °C oven and dried for 7 h to obtain the anion exchange membrane. The anion exchange membrane was repeatedly rinsed in deionized water and then immersed in deionized water for later use.

[0057] 33% hydrochloric acid was added dropwise to the phosphate rock slurry (18% grade), and the phosphate rock was decomposed at 40°C (the molar ratio of CaO to hydrochloric acid in the phosphate rock was 1:1.9). After 8 hours, the undecomposed silica slag was removed by filtration, and a calcium-containing chlorophosphoric acid solution was obtained. 10% sulfuric acid (the molar ratio of sulfuric acid to calcium ions was 1.1:1) was added to the chlorophosphoric acid solution, and the reaction was stirred for 1 hour. After aging and crystallization for 2 hours, a mixed solution of calcium sulfate and chlorophosphoric acid was obtained by filtration.

[0058] A mixed solution of calcium sulfate and chlorophosphate was added to the feed side of the anion exchange membrane cell, and water was added to the product side of the cell. Automatic diffusion was carried out at 90°C. After 5 hours, hydrochloric acid was obtained on the water side, and ammonium phosphate solution was obtained on the feed side.

[0059] Example 5

[0060] Preparation of membrane material: Same as in Example 1;

[0061] Preparation of anion exchange membrane: 1 g of iodinated membrane material PES-PPH-Pi with a piperidinyl R group was dissolved in 1 g of DMSO and stirred for 3 h until completely dissolved. The solution was then ultrasonically degassed for 15 min and allowed to stand for 1 h to obtain the casting solution. A nylon mesh with a mesh size of 100–400 mesh was thoroughly immersed in the DMSO solution to remove air bubbles from the base membrane. The nylon mesh was then immersed in the prepared casting solution. The immersed nylon mesh was laid flat on a polytetrafluoroethylene (PTFE) plate and rolled with a roller to ensure a tight bond between the base membrane and the casting solution, eliminating air bubbles. The PTFE plate was transferred to a 70°C oven and dried for 7 h to obtain the anion exchange membrane. The anion exchange membrane was repeatedly rinsed in deionized water and then immersed in deionized water for later use.

[0062] 25% hydrochloric acid was added dropwise to the phosphate rock slurry (22% grade), and decomposed at 55℃ (the molar ratio of CaO to hydrochloric acid in the phosphate rock was 1:1.9). After 6 hours, the undecomposed silica slag was removed by filtration, and a calcium-containing chlorophosphoric acid solution was obtained. 98% sulfuric acid (the molar ratio of sulfuric acid to calcium ions was 1.03:1) was added to the chlorophosphoric acid solution, and the reaction was stirred for 1 hour. After aging and crystallization for 2 hours, a mixed solution of calcium sulfate and chlorophosphoric acid was obtained by filtration.

[0063] A mixed solution of calcium sulfate and chlorophosphoric acid was added to the feed side of the anion exchange membrane cell, and water was added to the product side of the cell. Automatic diffusion was carried out at 60°C. After 5 hours, hydrochloric acid was obtained on the water side, and ammonium phosphate solution was obtained on the feed side.

[0064] This invention improves a method for separating chlorine and phosphorus from a mixture of ammonium chlorate and phosphate using an anion exchange membrane by studying the pore size, charge distribution, and selectivity of the anion exchange membrane. The anion exchange membrane material is prepared from cyclic ammonium phenolphthalein polyarylether sulfone membrane material. By selecting quaternary ammonium salt functional groups, the pore size can be effectively adjusted, resulting in different diffusion properties for different anions, thus achieving anion separation. Simultaneously, it effectively blocks the passage of cations in the ammonium chlorate system. This membrane material also exhibits acid resistance, alkali resistance, and high-temperature resistance, demonstrating high stability. This invention fabricates the membrane material into membrane cell modules, offering high flexibility in production. It effectively separates phosphorus and chlorine, reducing total project investment, production costs, energy consumption, and environmental risks. It represents a green, low-energy, high-efficiency, and lower-cost novel chlorine and phosphorus separation technology.

[0065] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for separating chlorine and phosphorus in a mixture of chlorophosphoric acid and ammonium chlorophosphate using an anion exchange membrane, characterized in that, Includes the following steps: Hydrochloric acid is added to low-grade phosphate rock slurry to decompose it and obtain a calcium-containing chlorophosphoric acid solution. A decalcifying agent is added to the calcium-containing chlorophosphoric acid solution to remove the calcium salt from the chlorophosphoric acid, resulting in a mixed solution of chlorophosphoric acid and ammonium chlorophosphoric acid. A mixed solution of chlorophosphoric acid and ammonium chlorophosphate is separated by an anion exchange membrane. After separation, ammonium phosphate or phosphoric acid solution is obtained on the feed side, and hydrochloric acid with a mass concentration of 15-30% is obtained on the water side. When hydrochloric acid is added to low-grade phosphate rock slurry, the molar ratio of CaO to hydrochloric acid in the phosphate rock is 1:1.9, the decomposition temperature is 40-75℃, and the time is 2-8h. The molar ratio of calcium ions in the decalcifying agent to chlorophosphoric acid is 1.0-1.1:1; The mixed solution of chlorophosphoric acid and ammonium chlorophosphate was subjected to membrane separation via anion exchange membrane at 35-90℃. The preparation method of anion exchange membrane is as follows: dissolve the anion membrane material in an organic solvent, degas it by ultrasonication after complete dissolution, let it stand, and obtain the casting solution; fully impregnate the base membrane in the organic solvent, and then transfer the base membrane to the casting solution for full impregnation; The impregnated base film is fixed on a polytetrafluoroethylene plate, then the base film is coated with a scraper, and then placed in an oven to dry to obtain an anion exchange membrane. The anion exchange membrane material is a cyclic ammonium phenolphthalein polyarylether sulfone membrane material, which is prepared by the following process: Under nitrogen protection, cyclic ammonium phenolphthalein, 4,4-difluorodiphenyl sulfone, biphenyl phenol, a basic compound, DMSO and toluene are added to a reaction flask and refluxed at 140°C for 8 hours. After the reaction, toluene and water are removed by azeotropic distillation. Then, the reaction is carried out at 180°C for 12 hours to obtain a viscous polymerization solution. After cooling to room temperature, DMSO is added for dilution, the solid is filtered off, and the solution is poured into water at 70°C to obtain a polymer product. The polymer product is vacuum dried at 120°C for 20-28 hours to obtain a PES-PPH-Pi polymer. The PES-PPH-Pi polymer is dissolved in DMSO, and iodomethane with twice the molar amount of amino groups in the PES-PPH-Pi polymer is added. The mixture is stirred at room temperature for 6-8 hours, and then precipitated in ethanol to obtain the polymer. After filtration, the polymer is vacuum dried at 80°C for 24 hours to obtain the anion exchange membrane material. The cyclic ammonium phenolphthalein structure is shown in formula (1): （1） In formula (1), the R group is a nitrogen-containing heterocycle, which is piperidinyl, tetrahydropyrroleyl or morpholinyl.

2. The method for separating chlorine and phosphorus in a mixture of chlorophosphoric acid and ammonium chlorophosphate using an anion exchange membrane according to claim 1, characterized in that, The grade of low-grade phosphate rock is 16-24%.

3. The method for separating chlorine and phosphorus in a mixture of chlorophosphoric acid and ammonium chlorophosphoric acid using an anion exchange membrane according to claim 1, characterized in that, The decalcifying agent is ammonium sulfate or sulfuric acid.

4. The method for separating chlorine and phosphorus in a mixture of chlorophosphoric acid and ammonium chlorophosphate using an anion exchange membrane according to claim 1, characterized in that, The mass concentration of hydrochloric acid is 20-33%.

5. The method for separating chlorine and phosphorus in a mixture of chlorophosphoric acid and ammonium chlorophosphoric acid using an anion exchange membrane according to claim 1, characterized in that, The removal of calcium salts from chlorophosphoric acid is carried out at a temperature of 40-75℃ for 2-8 hours.

6. The method for separating chlorine and phosphorus from a mixture of chlorophosphoric acid and ammonium chlorophosphate using an anion exchange membrane according to claim 1, characterized in that, The molecular weight of the anion exchange membrane material is 50,000 to 150,000; the base membrane is at least one of PVDF membrane, PTFE membrane, PP membrane, nylon mesh and PP mesh, wherein the pore size of PVDF membrane, PTFE membrane and PP membrane is 0.22μm to 30μm, and the mesh number of nylon mesh and PP mesh is 100 to 400 mesh.

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