A method for removing impurity metal cations from wet-process phosphoric acid

Abstract

The application provides a method for removing impurity metal cations in wet-process phosphoric acid, and relates to the technical field of impurity removal of phosphoric acid. The method comprises the following steps: mixing wet-process phosphoric acid with a settling agent for settling treatment to obtain supernatant and bottom slag; performing pressure filtration washing treatment on the bottom slag to obtain a filtrate; mixing the supernatant and the filtrate to obtain first clear liquid, mixing the first clear liquid with an impurity removal agent for impurity removal treatment to obtain clear acid; performing post-treatment on the impurity removal agent; the post-treatment comprises the following steps: after the impurity removal agent is saturated with metal cations, the impurity removal agent is mixed with a regenerating agent, and the regenerated impurity removal agent is reused; the regenerating agent is subjected to recovery treatment to obtain concentrated liquid, and the concentrated liquid is subjected to neutralization treatment. The method for removing metal cation impurities in wet-process phosphoric acid provided by the application has a wide application range, and can effectively solve the problem of high content of impurity metal cations in the production process of wet-process phosphoric acid and downstream chemical products.

Description

Technical Field

[0001] This application relates to the field of phosphoric acid impurity removal technology, and in particular to a method for removing impurity metal cations from wet-process phosphoric acid. Background Technology

[0002] Phosphoric acid, as an important basic chemical raw material, has applications determined by its purity. Low-purity phosphoric acid is generally used to produce low-end products such as phosphate fertilizers and animal feed, while high-purity phosphoric acid can be applied to high-value-added fields such as food, pharmaceuticals, and electronics. Currently, there are two main production processes for phosphoric acid: a thermal process based on the redox principle and a wet process based on the metathesis principle. Wet-process phosphoric acid has abundant raw material sources, low energy consumption, and low pollution, and has become dominant in industrial phosphoric acid production. The core challenge is removing impurity ions. Currently, solvent extraction is commonly used industrially, but the extraction rate is only about 50-60%, resulting in 40-50% residual acid that cannot be effectively treated. Developing new purification processes for wet-process phosphoric acid is of great significance for improving the comprehensive utilization rate and added value of phosphorus resources. Summary of the Invention

[0003] The purpose of this application is to provide a method for removing impurity metal cations from wet-process phosphoric acid, so as to solve the above-mentioned problems.

[0004] To achieve the above objectives, this application adopts the following technical solution: This application provides a method for removing impurity metal cations from wet-process phosphoric acid, comprising: mixing wet-process phosphoric acid with a settling agent for settling treatment to obtain a supernatant and a bottom residue; performing pressure filtration and washing treatment on the bottom residue to obtain a filtrate; mixing the supernatant and the filtrate to obtain a first clear liquid; mixing the first clear liquid with a purification agent for purification treatment to obtain purified acid; and performing post-treatment on the purification agent. The post-processing includes: the impurity remover is mixed with a regenerator after being saturated with adsorbed metal cations; the regenerated impurity remover is reused; the regenerator is recycled to obtain a concentrated solution; and the concentrated solution is neutralized.

[0005] The method for preparing the impurity remover includes: Under a protective gas atmosphere, nonionic guar gum is added to an alkaline solution to obtain the first solution; The first solution was continuously stirred and heated to a first temperature. After maintaining the temperature, ammonium persulfate solution was added to carry out the first reaction to obtain the first reaction product. The first reaction product was cooled to a second temperature, and methyl acrylate, functional molecules and montmorillonite were added to carry out a second reaction to obtain the second reaction product. The impurity remover is obtained by drying, pulverizing, and sieving the reaction mixture. The functional molecules include one of hydroxyethylidene diphosphate, aminotrimethylphosphonic acid, and 5-aminosalicylic acid.

[0006] Optionally, the protective gas includes nitrogen.

[0007] Optionally, the alkaline solution includes a NaOH solution with a pH of 10-12.

[0008] Optionally, the first temperature is 60°C.

[0009] Optionally, the constant temperature holding time is 0.5-1 hour.

[0010] Optionally, the first reaction time is 10-20 min.

[0011] Optionally, the concentration of the ammonium persulfate solution is 5 wt%.

[0012] Optionally, the temperature of the second reaction is 40°C.

[0013] Optionally, the mass ratio of the nonionic guar gum, the methyl acrylate, the functional molecule, and the montmorillonite is 20:5:5:10.

[0014] Optionally, the second reaction takes 5-8 hours.

[0015] Optionally, the montmorillonite is nano-montmorillonite.

[0016] Optionally, the drying conditions are: drying at 60°C until the second reaction product reaches a constant weight.

[0017] Optionally, the mesh size of the sieve used in the sieving process is 40 mesh.

[0018] Optionally, the settling agent is a dual-system settling agent, which includes settling agent A and settling agent B; The settling agent A comprises a silica-adsorbed polymerized guar gum composite; the settling agent B comprises a hydroxide sol-hybridized guar gum grafted with ethylene monomers composite.

[0019] Optionally, the sedimentation treatment includes: mixing the wet-process phosphoric acid with the sedimentation agent A to obtain a mixed solution, stirring and reacting at 50-80°C for 5-10 minutes; mixing the mixed solution with the sedimentation agent B and stirring for 3-5 minutes to allow sedimentation.

[0020] Optionally, the dosage of flocculant A is 500-1000 mg / L, and the dosage of flocculant B is 5-10 mg / L.

[0021] Optionally, the filter press washing process includes: using a diaphragm filter press, and before pressing, passing clean water through to wash the mud cake, with the amount of clean water being 2-5 times the chamber volume of the diaphragm filter press.

[0022] Optionally, the conditions for the impurity removal treatment are: a temperature of 50-80℃ and a time of 30-60 minutes.

[0023] Optionally, the volume ratio of the first clear liquid to the impurity removal agent is 0.5-2:1.

[0024] Optionally, the regenerant includes sulfuric acid or phosphoric acid; the concentration of the sulfuric acid and the phosphoric acid is independently 5-10 wt%.

[0025] Optionally, the regeneration reaction time of the impurity remover is 10-30 min, and the volume ratio of the impurity remover to the regenerator is 1-2:1.

[0026] Optionally, the recycling process includes electrodialysis and / or diffusion dialysis.

[0027] Optionally, the wet-process phosphoric acid includes dilute phosphoric acid, concentrated phosphoric acid, and residual acid from raffination.

[0028] Compared with the prior art, the beneficial effects of this application include: This application provides a complete method for removing metal cation impurities from wet-process phosphoric acid, effectively solving the problem of deep removal of polyvalent metal ions in wet-process phosphoric acid and significantly reducing the content of impurity ions such as aluminum, magnesium, and iron in the purified acid. Through the technical solution provided in this application, wet-process phosphoric acid is first mixed with a flocculant to form a suspension system, and stirred at a specific temperature to promote the formation of sediments from impurities. The separated bottom residue is treated by a filter press to recover residual phosphoric acid, and the resulting filtrate is combined with the upper clear liquid to form a preliminary purified liquid. When this purified liquid comes into contact with a specially formulated impurity remover, the functional groups in the impurity remover coordinate with the metal ions, and the layered structure provides physical adsorption sites, achieving deep purification through a combined effect. During the preparation of the impurity remover, guar gum unfolds its molecular chains under alkaline conditions to form a three-dimensional network, methyl acrylate grafting enhances the mechanical strength of the material, the introduction of functional molecules imparts selective adsorption capacity, and montmorillonite composites optimize the pore structure of the material.

[0029] On the other hand, the impurity removal agent provided in this application effectively solves the technical problems of low adsorption capacity and poor regeneration performance of impurity removal agents in the wet phosphoric acid purification process. Nitrogen protection ensures the integrity of the guar gum molecular structure, and a staged temperature control strategy optimizes the grafting reaction process, thereby resulting in the uniform distribution of functional components. The introduction of nano-montmorillonite significantly increases the specific surface area. The impurity removal agent prepared in this way can efficiently capture metal ions such as aluminum, magnesium, and iron in phosphoric acid, and can still recover a high initial adsorption capacity after simple acid washing and regeneration, significantly reducing the cost of wet phosphoric acid purification. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0031] Figure 1 This is a schematic diagram of the process flow for removing metal cation impurities from wet-process phosphoric acid provided in the embodiments. Detailed Implementation

[0032] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0033] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0034] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0035] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0036] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0037] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0038] To better illustrate the technical solution provided in this application, a general description of the technical solution provided in this application will be given before proceeding with specific implementation methods: This application provides a method for removing impurity metal cations from wet-process phosphoric acid, comprising: mixing wet-process phosphoric acid with a settling agent for settling treatment to obtain a supernatant and a bottom residue; performing pressure filtration and washing treatment on the bottom residue to obtain a filtrate; mixing the supernatant and the filtrate to obtain a first clear liquid; mixing the first clear liquid with a purification agent for purification treatment to obtain purified acid; and performing post-treatment on the purification agent. The post-treatment includes: after the impurity remover is saturated with adsorbed metal cations, it is mixed with a regenerator, and the regenerated impurity remover is reused; the regenerator is recovered through a recycling process, and the resulting concentrated liquid is neutralized and then disposed of in compliance with regulations, while the waste liquid is treated as general sewage.

[0039] The method for preparing the impurity remover includes: Under a protective gas atmosphere, nonionic guar gum is added to an alkaline solution to obtain the first solution; The first solution was continuously stirred and heated to a first temperature. After maintaining the temperature, ammonium persulfate solution was added to carry out the first reaction to obtain the first reaction product. The first reaction product was cooled to a second temperature, and methyl acrylate, functional molecules and montmorillonite were added to carry out a second reaction to obtain the second reaction product. The impurity remover is obtained by drying, pulverizing, and sieving the reaction mixture. The functional molecules include one of hydroxyethylidene diphosphate, aminotrimethylphosphonic acid, and 5-aminosalicylic acid.

[0040] Understandably, wet-process phosphoric acid first undergoes primary sedimentation with a dual-system settling agent. The bottom sludge after sedimentation enters the filter press washing process, while the supernatant enters the secondary impurity removal process. The solid waste after filter press washing is disposed of in compliance with regulations. The filtrate and supernatant are mixed and then a secondary impurity removal agent is added for further impurity removal, resulting in purified acid with low metal cation content. After the impurity removal agent becomes saturated, it is regenerated using a regenerator. The regenerated impurity removal agent is then reused and recovered through a recycling process. The resulting concentrated liquid is neutralized, and the solid waste is disposed of in compliance with regulations. The waste liquid is treated as general wastewater.

[0041] Furthermore, the primary sedimentation achieves efficient sedimentation and separation of the solid phase in wet-process phosphoric acid by adding an A / B dual-system sedimentation agent. While separating the solid phase, the two sedimentation agents can also destroy the stable chelation system formed by impurity metal cations in phosphoric acid, creating favorable conditions for secondary impurity removal.

[0042] In one alternative embodiment, the protective gas includes nitrogen.

[0043] In an optional embodiment, the alkaline solution comprises a NaOH solution with a pH of 10-12.

[0044] In one alternative implementation, the first temperature is 60°C.

[0045] In one optional implementation, the constant temperature holding time is 0.5-1 hour.

[0046] In one optional implementation, the first reaction takes 10-20 minutes.

[0047] In one optional embodiment, the concentration of the ammonium persulfate solution is 5 wt%.

[0048] In one optional embodiment, the temperature of the second reaction is 40°C.

[0049] In one optional embodiment, the mass ratio of the nonionic guar gum, the methyl acrylate, the functional molecule, and the montmorillonite is 20:5:5:10.

[0050] In one optional implementation, the second reaction takes 5-8 hours.

[0051] In one alternative embodiment, the montmorillonite is nano-montmorillonite.

[0052] In one optional embodiment, the drying conditions are: drying at 60°C until the second reaction product reaches a constant weight.

[0053] In one optional embodiment, the sieve used in the sieving process has a mesh size of 40.

[0054] In one optional embodiment, the settling agent is a dual-system settling agent, which includes settling agent A and settling agent B; The settling agent A comprises a silica-adsorbed polymerized guar gum composite; the settling agent B comprises a hydroxide sol-hybridized guar gum grafted with ethylene monomers composite.

[0055] Specifically, this application uses a natural plant gum modified impurity remover, which is prepared based on natural plant guar gum. On the one hand, it can utilize the hydroxyl groups in the molecular structure to chelate with metal ions. On the other hand, by introducing functional molecules to enhance its competitive chelating ability, it further destroys the stable chelation system formed by metal cations and phosphoric acid, thereby achieving efficient separation. Nano-montmorillonite has good adsorption capacity and can provide a good framework structure for the impurity remover. Several components work together to achieve efficient separation of metal impurity ions.

[0056] In an optional embodiment, the sedimentation treatment includes: mixing the wet-process phosphoric acid with the sedimentation agent A to obtain a mixed solution, stirring and reacting at 50-80°C for 5-10 minutes; mixing the mixed solution with the sedimentation agent B and stirring for 3-5 minutes to allow sedimentation.

[0057] In one optional embodiment, the amount of flocculant A is 500-1000 mg / L, and the amount of flocculant B is 5-10 mg / L.

[0058] Optionally, the settling time of the mixed solution after wet-process phosphoric acid and flocculant A can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any value between 5 and 10 min; the mixing time of the mixed solution and flocculant B can be 3 min, 4 min, 5 min, or any value between 3 and 5 min.

[0059] Optionally, the dosage of flocculant A can be 500 mg / L, 550 mg / L, 600 mg / L, 650 mg / L, 700 mg / L, 750 mg / L, 800 mg / L, 850 mg / L, 900 mg / L, 950 mg / L, 1000 mg / L, or any value between 500 and 1000 mg / L; the dosage of flocculant B can be 5 mg / L, 6 mg / L, 7 mg / L, 8 mg / L, 9 mg / L, 10 mg / L, or any value between 5 and 10 mg / L.

[0060] In an optional embodiment, the filter press washing process includes: using a diaphragm filter press, and before pressing, passing clean water through the filter cake to wash it, wherein the amount of clean water is 2-5 times the volume of the diaphragm filter press chamber.

[0061] In one optional embodiment, the conditions for the impurity removal process are: a temperature of 50-80°C and a time of 30-60 minutes.

[0062] Optionally, the temperature for the impurity removal treatment can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, or any value between 50℃ and 80℃; the time for the impurity removal treatment can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any value between 30 min and 60 min.

[0063] In one optional embodiment, the volume ratio of the first clarified liquid to the impurity removal agent is 0.5-2:1.

[0064] Optionally, the volume ratio of the first supernatant to the impurity remover can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or any value between 0.5 and 2:1.

[0065] In an optional embodiment, the regenerant comprises sulfuric acid or phosphoric acid; the concentration of the sulfuric acid and the phosphoric acid are each independently 5-10 wt%.

[0066] Optionally, the concentrations of sulfuric acid and phosphoric acid can be independently 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, 10wt%, or any value between 5 and 10wt%.

[0067] Optionally, the regeneration reaction time of the impurity remover is 10-30 min, and the volume ratio of the impurity remover to the regenerator is 1-2:1.

[0068] In one alternative implementation, the recycling process includes electrodialysis and / or diffusion dialysis.

[0069] Optionally, the wet-process phosphoric acid includes dilute phosphoric acid, concentrated phosphoric acid, and residual acid from raffination.

[0070] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0071] In the examples and comparative examples: Flocculant A is a silica-adsorbed polymerized guar gum composite, prepared by the following method: (1) Take 10.0g of carboxymethyl guar gum and disperse it in 490mL of deionized water. Heat the water to 50℃, add 0.2g of ammonium persulfate, and react for 2h to obtain a low molecular weight carboxymethyl guar gum solution with a molecular weight of 80000Da.

[0072] (2) Take 2g of nano-silica powder and add it to the low molecular weight carboxymethyl guar gum solution prepared in (1) under high speed stirring. Purge nitrogen for 20 minutes to remove oxygen, raise the temperature to 40℃, add 5mL of 10wt% ammonium persulfate solution with a syringe, and stir slowly for 8h under nitrogen protection. After low temperature vacuum spray drying, it is obtained.

[0073] Flocculant B is a hydroxide sol-hybridized guar gum grafted with ethylene monomers, prepared by the following method: (1) Dissolve 15.4g of ferric chloride in 190mL of deionized water, and dissolve 16.6g of ammonium carbonate in 110mL of deionized water. Place the prepared ferric chloride solution under high speed stirring, and use a titration pump to add the above ammonium carbonate solution to the ferric chloride solution to obtain ferric hydroxide sol.

[0074] (2) Take 2.0g of quaternary ammonium salt cationic guar gum and disperse it in 100mL of deionized water. After transferring it into the reactor, purge it with nitrogen for 20 minutes to remove oxygen. Heat it to 50℃ and add 20mL of 1% cerium ammonium sulfate solution with a syringe. Dissolve 2g of acrylamide in 20mL of ferric hydroxide sol prepared in step (1). Then add it dropwise into the reactor with a syringe. Stir the reaction slowly for 8h and dry it under low temperature vacuum.

[0075] Example 1 This embodiment provides a natural plant-based impurity remover, and the preparation steps are as follows: 350 mL of NaOH (pH=12) solution was added to a 500 mL four-necked flask equipped with a mechanical stirrer, reflux tube, nitrogen delivery tube, and constant pressure dropping funnel. 20 g of guar gum was added and dispersed evenly. Under continuous stirring, the solution was heated to 60 °C and held at this temperature for 1 hour. Then, 10 mL of 5% ammonium persulfate solution was added. After 20 minutes, the reactants were cooled to 40 °C, and 50 mL of a mixed solution containing 5 g of methyl acrylate, 5 g of hydroxyethylidene diphosphonic acid, and 10 g of nano-montmorillonite was added. The reaction was continued at this constant temperature for 5 hours. The entire experiment was conducted under nitrogen protection. After the reaction, the resulting product was placed in a forced-air drying oven and dried at 60 °C to constant weight. It was then pulverized and passed through a 40-mesh sieve to obtain the impurity remover.

[0076] Example 2 This embodiment provides a natural plant-based impurity remover. The difference from Example 1 is that hydroxyethylidene diphosphonic acid is replaced with aminotrimethylphosphonic acid. The remaining steps and raw materials are the same as in Example 1, and will not be repeated here.

[0077] Example 3 This embodiment provides a natural plant-based impurity remover. The difference from Example 1 is that hydroxyethylidene diphosphonic acid is replaced with 5-aminosalicylic acid. The remaining steps and raw materials are the same as in Example 1, and will not be repeated here.

[0078] Example 4 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid, the process flow of which is as follows: Figure 1 As shown, the specific steps are as follows: Add 500 mL of wet-process concentrated phosphoric acid with a P2O5 content of 48% to a beaker placed in a constant temperature water bath (65℃). After the temperature stabilizes, add 5 mL of a 10% concentration of silica-adsorbed polymerized guar gum composite and stir for 10 min. Then add 5 mL of a 0.1% concentration of hydroxide sol-hybridized guar gum grafted with ethylene monomer composite and stir for 5 min. Let the mixture stand in the constant temperature water bath for 3 h to settle. Take 400 mL of the mixture of supernatant and bottom residue filtrate. The bottom residue is filtered using a diaphragm filter press. Before pressing, the filter cake is washed with clean water, and the amount of clean water used is twice the chamber volume of the diaphragm filter press.

[0079] Add 200 mL of the impurity removal agent prepared in Example 1, stir and react in a 65°C constant temperature water bath for 60 min. After the reaction is complete, filter to obtain clear acid. Add 200 mL of 10 wt% sulfuric acid as a regenerator to the impurity removal agent and stir and react for 30 min. Filter and wash twice with clean water spray. After mixing the washing liquid with the regenerator, recover by electrodialysis with a recovery rate of 70%. Add lime to the remaining concentrated liquid for neutralization. The waste residue after neutralization is treated as general solid waste, and the waste liquid is treated as general sewage.

[0080] Example 5 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid. The difference from Example 4 is that the impurity remover is replaced with the impurity remover prepared in Example 2. The remaining steps and methods are the same as in Example 4, and will not be repeated here.

[0081] Example 6 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid. The difference from Example 4 is that the impurity remover is replaced with the impurity remover prepared in Example 3. The remaining steps and methods are the same as in Example 4, and will not be repeated here.

[0082] Example 7 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid, the specific steps of which are as follows: Add 500 mL of raffinate with a P2O5 content of 46% to a beaker placed in a constant temperature water bath (65℃). After the temperature stabilizes, add 5 mL of a 10% concentration of silica-adsorbed polymerized guar gum composite and stir for 10 min. Then add 5 mL of a 0.1% concentration of hydroxide sol-hybridized guar gum grafted with ethylene monomer composite and stir for 5 min. Let the mixture stand in the constant temperature water bath for 5 h to settle. Take 400 mL of the mixture of supernatant and bottom residue filtrate. The bottom residue is filtered using a diaphragm filter press. Before pressing, the filter cake is washed with clean water, and the amount of clean water used is twice the chamber volume of the diaphragm filter press.

[0083] Add 400 mL of the impurity removal agent prepared in Example 1, stir and react in a 65°C constant temperature water bath for 60 min. After the reaction is complete, filter to obtain clear acid. Add 400 mL of 10 wt% sulfuric acid to the impurity removal agent and stir and react for 30 min. Filter and wash twice with clean water spray. Mix the washing liquid with the regenerator and recover by electrodialysis. The recovery rate is 70%. Add lime to the remaining concentrated liquid for neutralization. The waste residue after neutralization is treated as general solid waste, and the waste liquid is treated as general sewage.

[0084] Example 8 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid. The difference from Example 7 is that the impurity remover is replaced with the impurity remover prepared in Example 2. The remaining steps and methods are the same as in Example 7, and will not be repeated here.

[0085] Example 9 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid. The difference from Example 7 is that the impurity remover is replaced with the impurity remover prepared in Example 3. The remaining steps and methods are the same as in Example 7, and will not be repeated here.

[0086] Example 10 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid, the specific steps of which are as follows: Add 500 mL of dilute phosphoric acid with a P2O5 content of 25% to a beaker placed in a constant temperature water bath (65℃). After the temperature stabilizes, add 2.5 mL of a 10% concentration of silica-adsorbed polymerized guar gum composite and stir for 10 min. Then add 2.5 mL of a 0.1% concentration of oxide sol hybrid guar gum grafted with ethylene monomer composite and stir for 5 min. Let it stand in the constant temperature water bath for 1 h to settle. Take 400 mL of the mixture of supernatant and bottom residue filtrate. The bottom residue is filtered using a diaphragm filter press. Before pressing, the filter cake is washed with clean water, and the amount of clean water used is twice the chamber volume of the diaphragm filter press.

[0087] Add 100 mL of the impurity removal agent prepared in Example 1, stir and react in a 65°C constant temperature water bath for 60 min. After the reaction is complete, filter to obtain clear acid. Add 100 mL of 10 wt% sulfuric acid to the impurity removal agent and stir and react for 30 min. Filter and wash twice with clean water spray. Mix the washing liquid with the regenerator and recover by electrodialysis. The recovery rate is 70%. Add lime to the remaining concentrated liquid for neutralization. The waste residue after neutralization is treated as general solid waste, and the waste liquid is treated as general sewage.

[0088] Example 11 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid. The difference from Example 10 is that the impurity remover is replaced with the impurity remover prepared in Example 2. The remaining steps and methods are the same as in Example 7, and will not be repeated here.

[0089] Example 12 This embodiment provides a method for removing impurity metal cations from wet-process phosphoric acid. The difference from Example 10 is that the impurity remover is replaced with the impurity remover prepared in Example 3. The remaining steps and methods are the same as in Example 10, and will not be repeated here.

[0090] The removal effects of metal cation impurities in Examples 4-12 are shown in Table 1: Comparative Example 1 This comparative example provides a method for removing impurity metal cations from wet-process phosphoric acid. The only difference from Example 4 is the use of a strong acid cation exchange resin (a conventional impurity remover, model Amberlite® IR-120, purchased from Aladdin) as the impurity remover. All other steps and methods are the same as in Example 4 and will not be repeated here.

[0091] Comparative Example 2 This comparative example provides a method for removing impurity metal cations from wet-process phosphoric acid. The only difference from Example 7 is the use of a strong acid cation exchange resin (a conventional impurity remover, model Amberlite® IR-120, purchased from Aladdin) as the impurity remover. All other steps and methods are the same as in Example 7 and will not be repeated here.

[0092] Comparative Example 3 This comparative example provides a method for removing impurity metal cations from wet-process phosphoric acid. The only difference from Example 10 is the use of a strong acid cation exchange resin (a conventional impurity remover, model Amberlite® IR-120, purchased from Aladdin) as the impurity remover. All other steps and methods are the same as in Example 10 and will not be repeated here.

[0093] Table 1. Removal effect of metal cation impurities by examples and comparative examples.

[0094] As shown in Table 1, the method for removing metal cation impurities from wet-process phosphoric acid and the method for preparing the impurity remover provided in this application, through a stepwise treatment using a dual-system precipitant and impurity remover, combined with a regeneration and reuse process, significantly reduce Al... 3+ Mg 2+ Fe 2+ With a certain metal ion content, this method offers advantages such as efficient removal of metal cation impurities, improved phosphoric acid purity, and increased resource recycling rate. Compared to existing technologies, traditional extraction methods require large amounts of organic solvents and generate difficult-to-treat residual acid. As shown in the examples, this application achieves impurity removal through a synergistic effect of sedimentation and adsorption, eliminating the need for organic solvents. The impurity remover, through a multi-component composite design, possesses both chemical chelation and physical adsorption functions and can be regenerated and reused through acid washing. Conventional purification processes often employ multi-stage treatment units; this solution organically combines sedimentation and adsorption processes, simplifying the production process.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0096] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for removing impurity metal cations from wet-process phosphoric acid, characterized in that, include: Wet-process phosphoric acid is mixed with a flocculant and subjected to sedimentation treatment to obtain a supernatant and a bottom residue; the bottom residue is then subjected to pressure filtration and washing treatment to obtain a filtrate. The supernatant and the filtrate are mixed to obtain a first clear liquid. The first clear liquid is then mixed with a purification agent for purification treatment to obtain a purified acid. The impurity removal agent undergoes post-treatment; The post-treatment includes: the impurity remover is mixed with a regenerator after being saturated with adsorbed metal cations; the regenerated impurity remover is reused; the regenerator is recycled to obtain a concentrated solution; and the concentrated solution is neutralized. The method for preparing the impurity remover includes: Under a protective gas atmosphere, nonionic guar gum is added to an alkaline solution to obtain the first solution; The first solution was continuously stirred and heated to a first temperature. After maintaining the temperature, ammonium persulfate solution was added to carry out the first reaction to obtain the first reaction product. The first reaction product was cooled to a second temperature, and methyl acrylate, functional molecules and montmorillonite were added to carry out a second reaction to obtain the second reaction product. The impurity remover is obtained by drying, pulverizing, and sieving the reaction mixture. The functional molecule includes one of hydroxyethylidene diphosphate, aminotrimethylphosphonic acid, and 5-aminosalicylic acid. The settling agent is a dual-system settling agent, comprising settling agent A and settling agent B; settling agent A comprises a silica-adsorbed polymerized guar gum composite; settling agent B comprises a hydroxide sol-polymerized guar gum grafted with ethylene monomers composite.

2. The method for removing impurity metal cations from wet-process phosphoric acid according to claim 1, characterized in that, At least one of the following conditions must be met: a. The protective gas includes nitrogen; b. The alkaline solution includes a NaOH solution with a pH value of 10-12; c. The first temperature is 60℃; d. The constant temperature holding time is 0.5-1 hour; e. The time for the first reaction is 10-20 minutes; f. The concentration of the ammonium persulfate solution is 5 wt%; g. The temperature of the second reaction is 40°C; h. The mass ratio of the nonionic guar gum, the methyl acrylate, the functional molecule, and the montmorillonite is 20:5:5:10; i. The second reaction takes 5-8 hours; j. The montmorillonite described is nano-montmorillonite; k. The drying conditions are: 60°C until the second reaction product reaches a constant weight; l. The mesh size of the sieve used in the sieving process is 40 mesh.

3. The method for removing impurity metal cations from wet-process phosphoric acid according to claim 1, characterized in that, The sedimentation treatment includes: mixing the wet-process phosphoric acid with the sedimentation agent A to obtain a mixed solution, stirring and reacting at 50-80°C for 5-10 minutes; mixing the mixed solution with the sedimentation agent B and stirring for 3-5 minutes, and sedimenting for 2-3 hours.

4. The method for removing impurity metal cations from wet-process phosphoric acid according to claim 3, characterized in that, The dosage of settling agent A is 500-1000 mg / L; the dosage of settling agent B is 5-10 mg / L.

5. The method for removing impurity metal cations from wet-process phosphoric acid according to claim 1, characterized in that, The filter press washing process includes: using a diaphragm filter press, and before pressing, passing clean water through the filter cake to wash it, with the amount of clean water being 2-5 times the chamber volume of the diaphragm filter press.

6. The method for removing impurity metal cations from wet-process phosphoric acid according to claim 1, characterized in that, The conditions for the impurity removal process are: temperature 50-80℃ and time 30-60min.

7. The method for removing impurity metal cations from wet-process phosphoric acid according to claim 6, characterized in that, The volume ratio of the first clear liquid to the impurity removal agent is 0.5-2:

1.

8. The method for removing impurity metal cations from wet-process phosphoric acid according to claim 1, characterized in that, At least one of the following conditions must be met: n. The regenerant includes sulfuric acid or phosphoric acid; the concentration of the sulfuric acid and the phosphoric acid are each independently 5-10 wt%; o. The regeneration reaction time of the impurity remover is 10-30 min, and the volume ratio of the impurity remover to the regenerator is 1-2:1; p. The recycling process includes electrodialysis and / or diffusion dialysis.

9. The method for removing impurity metal cations from wet-process phosphoric acid according to any one of claims 1-8, characterized in that, The wet-process phosphoric acid includes dilute phosphoric acid, concentrated phosphoric acid, and residual acid from raffination.

Images