Wet-process phosphoric acid defluorination extraction agent and wet-process phosphoric acid extraction defluorination method

Abstract

The invention relates to a wet-process phosphoric acid defluorination extraction agent and a wet-process phosphoric acid extraction defluorination method, and belongs to the technical field of chemical engineering. The extraction agent is prepared from organic amine, a cosolvent and a diluent according to the volume ratio of (10-100): (0-30): (0-90), and the content of the cosolvent and the content of the diluent are not 0; the organic amine comprises at least one of primary amine RNH2 of primary amine, secondary amine R2NH of secondary amine, tertiary amine R3N of tertiary amine and quaternary ammonium alkali R4N < + > OH <->, and R is alkyl; the cosolvent is prepared from at least one of n-butyl alcohol, n-hexanol, cyclohexanol, 2-ethyl-1-hexanol and n-octyl alcohol. The wet-process phosphoric acid can be directly treated, the phosphoric acid loss rate is low, the energy consumption is low, silica gel blockage is avoided, three types of high-value products including SiF4, HF and phosphate are produced, and phosphorus-fluorine-silicon resources are recycled.

Description

Technical Field

[0001] The invention relates to a wet-process phosphoric acid defluorination extractant and a wet-process phosphoric acid extraction defluorination method, belonging to the technical field of chemical industry. Background Art

[0002] Defluorination is a key step in balancing environmental protection, cost and product quality in the processing of wet-process phosphoric acid. The difficulty lies in efficient separation and resource utilization. Fluorine in wet-process phosphoric acid (in the form of free HF, SiF62-, AlF63-, etc.) will reduce the purity of the product and affect downstream applications. For example: food-grade / electronic-grade phosphoric acid requires a fluorine content of less than 10ppm, otherwise it will corrode equipment or affect food safety; fluorine in fertilizer production will cause phosphate fertilizer to agglomerate or soil pollution. In addition, fluoride is toxic, and the HF gas volatilized during the processing will corrode equipment and endanger the health of workers. Fluorine-containing wastewater and exhaust gas emissions may cause pollution to surrounding soil and water bodies (such as chronic diseases such as fluorosis). In production, HF and fluorosilicic acid will corrode stainless steel and glass-lined equipment, increasing maintenance costs.

[0003] The traditional defluorination method has the following defects: calcium salt precipitation method introduces Ca 2+ Impurities require secondary purification; the evaporation concentration method has high energy consumption and is prone to generating silica gel to clog the equipment; the existing extraction process cannot directly process low-concentration fluorosilicic acid (<1.5%), and the loss rate of phosphoric acid is high; the recovery rate of fluorine and silicon resources is low, and the coupled utilization of the phosphorus, fluorine and silicon industries has not been realized.

[0004] CN118125452A discloses a method for converting hydrofluoric acid and fluorosilicic acid, by-products of phosphate rock, into anhydrous hydrogen fluoride with low energy consumption. The method comprises: a. extraction; b. inorganic alkali stripping; or inorganic salt stripping; c. removing water from the aqueous fluorosilicate solution to obtain a fluorosilicate solid; d. pyrolysis; or acidolysis. The present invention is different from the currently used method of preparing anhydrous hydrogen fluoride from dilute fluorosilicic acid, a by-product of phosphate rock.

[0005] Compared with the process of silicon tetrafluoride, the invention has a wide range of applications, the difficulty of the fluosilicic acid preparation process is reduced, and the production energy consumption is greatly reduced; the economic value of the invention lies in the ability to simultaneously obtain high-value fluorination products, high-purity silicon tetrafluoride gas and anhydrous hydrogen fluoride gas, and the final products are all recycled or can be used as

[0006] The product is sold, and no by-products or waste require further treatment. However, it has limitations: it is only applicable to fluorosilicic acid, a by-product of phosphate rock, which requires defluorination first and cannot be directly used in wet-process phosphoric acid systems; it does not address the problem of phosphoric acid entrainment losses; it lacks a pretreatment process, and is not adaptable to low-concentration fluorine. Summary of the Invention

[0007] The first object of the present invention is to provide a wet-process phosphoric acid defluorination extractant.

[0008] In order to achieve the first object of the present invention, the extractant is an organic amine, a cosolvent, and a diluent prepared in a volume ratio of 10-100:0-30:0-90, and the content of the cosolvent and the diluent is not 0; the organic amine includes a primary amine RNH2, a secondary amine R2NH, a tertiary amine R3N, a quaternary ammonium base R4N + OH - At least one of, wherein R is a hydrocarbon group; the cosolvent includes at least one of n-butanol, n-hexanol, cyclohexanol, 2-ethyl-1-hexanol, and n-octanol; the diluent includes at least one of sulfonated kerosene, n-dodecane, isomeric dodecane, n-tetradecane, n-hexadecane, and 260# solvent oil.

[0009] Preferably, the extractant is an organic amine, a cosolvent, and a diluent prepared in a volume ratio of 10-15:10-20:65-75.

[0010] The second object of the present invention is to provide a method for extractive defluorination of wet-process phosphoric acid.

[0011] To achieve the second object of the present invention, the method for extractive defluorination of wet-process phosphoric acid comprises:

[0012] A extraction: using the above-mentioned extractant to extract fluorosilicic acid in the wet-process phosphoric acid raw material at 10-70°C, and phase separation to obtain purified phosphoric acid and an organic phase loaded with fluorosilicate;

[0013] B. Stripping: reacting the organic phase with a stripping agent, separating the phases to obtain a fluorosilicate solution and a regenerated organic phase, wherein the stripping agent is an inorganic alkali aqueous solution or an inorganic salt aqueous solution;

[0014] C. Extractant regeneration: adding ammonia water to the regenerated organic phase to obtain an ammonium salt solution and a regenerated extractant, or heating the regenerated organic phase to obtain an aqueous solution and a regenerated extractant. The regenerated extractant is returned to step A for recycling, and the aqueous solution is returned to step B for preparing a stripping agent.

[0015] In a specific embodiment, the method further includes pretreating the wet-process phosphoric acid raw material before extraction in step A: adding a silicon replenisher to the wet-process phosphoric acid raw material, the silicon replenishing amount being 1.1 to 1.2 times the theoretical value, reacting at 10 to 90° C. for 20 to 40 minutes, aging for 1 hour, and filtering to obtain the pretreated wet-process phosphoric acid raw material.

[0016] The theoretical value of the amount of silicon supplement is the amount of silicon supplement required to convert all of the raw acid into fluorosilicic acid after adding the silicon source so that the F:Si molar ratio in the raw acid is 6:1.

[0017] In a specific embodiment, the silicon supplementing agent is silicon dioxide, diatomaceous earth or sodium silicate.

[0018] In a specific embodiment, the wet-process phosphoric acid raw material in step A includes wet-process phosphoric acid, slag acid produced during wet-process phosphoric acid concentration, first-stage acid during wet-process phosphoric acid concentration, second-stage acid during wet-process phosphoric acid concentration, raffinate acid produced as a by-product of refined phosphoric acid, or two raffinate acids from a TBP process; preferably, the mass concentration of P2O5 in the wet-process phosphoric acid raw material is 20% to 48%.

[0019] In a specific embodiment, the mass concentration of fluorine in the wet-process phosphoric acid raw material in step A is 0.1 wt.% to 10.0 wt.%, preferably 1.5 wt.% to 2.0 wt.%; the extraction time in step A is preferably 10 to 90 minutes, and the volume ratio of the extractant to the wet-process phosphoric acid raw material is preferably 1 to 2; more preferably, the volume ratio of the extractant to the wet-process phosphoric acid raw material is 1.5 to 2.

[0020] In a specific embodiment, the fluorine extraction rate of the extraction in step A is above 60%, and the phosphoric acid extraction rate is below 30%; preferably, the fluorine extraction rate is above 82%.

[0021] In a specific embodiment, the volume ratio of the organic phase in step B to the stripping agent is 2:1 to 1:5, the stripping temperature is 10 to 70° C., and the inorganic base is preferably KOH or NaOH.

[0022] In a specific embodiment, the method further comprises recovering fluorine resources:

[0023] The fluorosilicate solution of step B and step C is subjected to solid-liquid separation at 70-90° C. to obtain a fluorosilicate ointment and a filtrate, the fluorosilicate ointment is dried to obtain a solid product fluorosilicate, and the solid product fluorosilicate is pyrolyzed at 200-800° C. to generate SiF4 and a fluoride salt, or acidolyzed at 95-105% sulfuric acid to generate SiF4 and HF;

[0024] Preferably, the pyrolysis is carried out under a nitrogen atmosphere, the pyrolysis temperature of fluorosilicate K2SiF6 is 400-600°C, and the pyrolysis temperature of Na2SiF6 is 300-800°C;

[0025] Phosphoric acid recovery: the filtrate is cooled and crystallized, and solid-liquid separation is performed to obtain phosphate solid and mother liquor, and the mother liquor is recycled for the stripping step.

[0026] Beneficial effects:

[0027] 1. The present invention can directly process wet-process phosphoric acid: it breaks through the limitation of existing technology that is only applicable to by-product fluorosilicic acid and is extended to the main process of wet-process phosphoric acid;

[0028] 2. Low phosphoric acid loss rate: Through stripping-crystallization, the phosphoric acid recovery rate is >99%;

[0029] 3. Energy consumption advantage: compared with the evaporation method, it saves more than 40% energy and avoids silica gel clogging;

[0030] 4. Industrial chain collaboration: produce three types of high-value products, namely SiF4, HF and phosphate, and realize the recycling and utilization of phosphorus-fluorine-silicon resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a process flow chart of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to achieve the first object of the present invention, the extractant is an organic amine, a cosolvent, and a diluent prepared in a volume ratio of 10-100:0-30:0-90, and the content of the cosolvent and the diluent is not 0; the organic amine includes a primary amine RNH2, a secondary amine R2NH, a tertiary amine R3N, a quaternary ammonium base R4N + OH - At least one of the following, wherein R is a hydrocarbon group; the cosolvent includes at least one of n-butanol, n-hexanol, cyclohexanol, 2-ethyl-1-hexanol, and n-octanol; the diluent includes at least one of sulfonated kerosene, n-dodecane, isomeric dodecane, n-tetradecane, n-hexadecane, and 260# solvent oil.

[0033] Preferably, the extractant is an organic amine, a cosolvent, and a diluent prepared in a volume ratio of 10-15:10-20:65-75.

[0034] To achieve the second object of the present invention, the method for extractive defluorination of wet-process phosphoric acid comprises:

[0035] A extraction: using the above-mentioned extractant to extract fluorosilicic acid in the wet-process phosphoric acid raw material at 10-70°C, and phase separation to obtain purified phosphoric acid and an organic phase loaded with fluorosilicate;

[0036] B. Stripping: reacting the organic phase with a stripping agent, separating the phases to obtain a fluorosilicate solution and a regenerated organic phase, wherein the stripping agent is an inorganic alkali aqueous solution or an inorganic salt aqueous solution;

[0037] C. Extractant regeneration: adding ammonia water to the regenerated organic phase to obtain an ammonium salt solution and a regenerated extractant, or heating the regenerated organic phase to obtain an aqueous solution and a regenerated extractant. The regenerated extractant is returned to step A for recycling, and the aqueous solution is returned to step B for preparing a stripping agent.

[0038] In a specific embodiment, the method further includes pretreating the wet-process phosphoric acid raw material before extraction in step A: adding a silicon replenisher to the wet-process phosphoric acid raw material, the silicon replenishing amount being 1.1 to 1.2 times the theoretical value, reacting at 10 to 90° C. for 20 to 40 minutes, aging for 1 hour, and filtering to obtain the pretreated wet-process phosphoric acid raw material.

[0039] In a specific embodiment, the silicon supplementing agent is silicon dioxide, diatomaceous earth or sodium silicate.

[0040] In a specific embodiment, the wet-process phosphoric acid raw material in step A includes wet-process phosphoric acid, slag acid produced during wet-process phosphoric acid concentration, first-stage acid during wet-process phosphoric acid concentration, second-stage acid during wet-process phosphoric acid concentration, raffinate acid produced as a by-product of refined phosphoric acid, or two raffinate acids from a TBP process; preferably, the mass concentration of P2O5 in the wet-process phosphoric acid raw material is 20% to 48%.

[0041] In a specific embodiment, the mass concentration of fluorosilicic acid in the wet-process phosphoric acid raw material in step A is 0.1wt.% to 10.0wt.%, preferably 1.5wt.% to 2.0wt.%; the extraction time in step A is preferably 10 to 90 minutes, and the volume ratio of the extractant to the wet-process phosphoric acid raw material is preferably 1 to 2; more preferably, the volume ratio of the extractant to the wet-process phosphoric acid raw material is 1.5 to 2.

[0042] In a specific embodiment, the fluorine extraction rate of the extraction in step A is 60% to 95%, and the phosphoric acid extraction rate is less than 30%; preferably, the fluorine extraction rate is above 82%.

[0043] In one embodiment, the volume ratio of the organic phase to the stripping agent in step B is 2:1 to 1:5, the stripping temperature is 10 to 70° C., and the inorganic base is preferably KOH or NaOH. The inorganic salt solution for stripping can be at least one of a soluble potassium salt K2SO4, KCl, or KNO3, or a sodium salt solution Na2SO4, NaCl, or NaCl.

[0044] In a specific embodiment, the inorganic alkali stripping time is 0.25 to 2 hours, the volume ratio of the organic phase to the inorganic alkali stripping agent is preferably 2:1 to 1:5, the concentration of the stripping agent is preferably 0.5 to 20 mol / L, and the stripping rate of the stripping is preferably >98%.

[0045] In a specific embodiment, the inorganic salt stripping time is 0.25 to 4 hours, the volume ratio of the organic phase to the inorganic salt stripping agent is preferably 2:1 to 1:5, the concentration of the stripping agent is preferably 0.5 to 10 mol / L, and the stripping rate of the stripping is preferably >98%.

[0046] In a specific embodiment, the method further comprises recovering fluorine resources:

[0047] The fluorosilicate solution of step B is subjected to solid-liquid separation at 70-90° C. to obtain a fluorosilicate ointment and a filtrate, the fluorosilicate ointment is dried to obtain a solid product fluorosilicate, and the solid product fluorosilicate is pyrolyzed at 200-800° C. to generate SiF4 and a fluoride salt, or acidolyzed at 95-105% sulfuric acid to generate SiF4 and HF;

[0048] Preferably, the pyrolysis is carried out under a nitrogen atmosphere, the pyrolysis temperature of fluorosilicate K2SiF6 is 400-600°C, and the pyrolysis temperature of Na2SiF6 is 300-800°C;

[0049] Phosphoric acid recovery: the filtrate is cooled and crystallized, and solid-liquid separation is performed to obtain phosphate solid and mother liquor, and the mother liquor is recycled for the stripping step.

[0050] The solid-liquid separation is preferably performed by filtration, and the filtered water is recovered for use in preparing the inorganic alkaline solution, salt solution or ammonia water for secondary stripping; the drying temperature is preferably controlled at 100° C. to 300° C., and the moisture content after drying is less than 0.1%.

[0051] Filtration can be carried out by plate and frame filter pressing, belt vacuum filtration, fully automatic vertical filter pressing, etc. After filtration, the filter residue obtained is K2SiF6 and Na2SiF6 fluorosilicates according to the different alkali and salt used.

[0052] The pyrolysis is kept at high temperature for a period of time to remove the residual organic solvent, and the silicon tetrafluoride gas obtained after the pyrolysis is separated and purified, and the fluorides KF and NaF are recovered and sold.

[0053] In a specific embodiment, the process further includes purifying the silicon tetrafluoride gas obtained after pyrolysis, wherein the method for purifying the silicon tetrafluoride gas includes at least one of condensation, dust removal, and purification, and finally separating and recovering the fluoride products KF and NaF.

[0054] In a specific embodiment, the acidolysis includes high-temperature acidolysis or low-temperature acidolysis, the fluorosilicate solid for the high-temperature acidolysis is at least one of K2SiF6 and Na2SiF6, the temperature for the high-temperature acidolysis is 19°C to 450°C, and the reaction time for the high-temperature acidolysis is preferably 30 to 90 minutes; the fluorosilicate solid for the low-temperature acidolysis is at least one of K2SiF6 and Na2SiF6, the temperature for the low-temperature acidolysis is less than 19°C, and the reaction time for the low-temperature acidolysis is preferably 30 to 180 minutes; the sulfuric acid concentration of the acidolysis is preferably 95 to 105 wt%.

[0055] The sulfuric acid used in the present invention is fuming sulfuric acid, and its concentration is based on the sulfate SO4 2- Determined, because there is gaseous sulfate ion SO4 in fuming sulfuric acid 2- , so there is a case where it may be greater than 100wt%.

[0056] In a specific embodiment, the separation method includes: performing high-temperature acid hydrolysis to obtain a mixed gas of anhydrous hydrogen fluoride and silicon tetrafluoride, and performing rectification to obtain high-purity anhydrous hydrogen fluoride and silicon tetrafluoride respectively; performing low-temperature acid hydrolysis to directly collect anhydrous silicon tetrafluoride gas, and then heating the liquid after low-temperature acid hydrolysis to 20°C to 60°C and reacting for 20 to 55 minutes to separate the anhydrous hydrogen fluoride gas;

[0057] Preferably, the separated sulfate is returned to the recycling stripping process;

[0058] The methods used for the rectification and purification include but are not limited to adsorption method, freezing method, fluorine gas method and fluorinating agent method.

[0059] The specific embodiments of the present invention are further described below in conjunction with examples, but the present invention is not limited to the scope of the examples.

[0060] Example 1

[0061] Inorganic base KOH stripping

[0062] Silica was added to wet-process phosphoric acid at a dosage of 1.2 times the theoretical value. The mixture was reacted at 40°C for 40 minutes, aged for 1 hour, and filtered to obtain pretreated wet-process phosphoric acid. Extraction was then performed at 40°C. A separatory funnel was charged with an extractant (volume ratio: 2:1) and wet-process phosphoric acid (0.44 wt% F and 25 wt% P2O5). The extractant composition (volume ratio: trioctylamine (TOA): n-octanol: sulfonated kerosene = 0.15:0.20:0.65) was added. After 60 minutes, the phases separated to produce aqueous phase 1 and oil phase 1, which is the purified wet-process phosphoric acid. KOH aqueous solution was added to oil phase 1 for stripping. The volume ratio of KOH aqueous solution to organic phase was 1:2. The mixture was reacted at 30°C for 40 minutes, allowed to stand, and separated to produce aqueous phase 2 and oil phase 2. Aqueous phase 2 is heated and filtered at 70°C. The filtrate is a potassium dihydrogen phosphate solution. The filter cake is dried at 120°C for 6 hours to obtain potassium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate is cooled, crystallized, and filtered to obtain potassium dihydrogen phosphate crystals. The filtered mother liquor can be used to dissolve KOH and return to the stripping stage. Oil phase 2 is heated to 50°C, allowed to stand for 40 minutes, and then separated to obtain oil phase 3, trioctylamine, which is recovered for re-extraction. Aqueous phase 3 is water, which can dissolve KOH and return to the stripping stage. The dried filter cake, K2SiF6 fluorosilicate, is ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas is collected using a gas bag. After the reaction is complete, the pyrolyzed solid KF is recovered as a byproduct. The SiF4 gas is purified by cryogenic distillation with liquid nitrogen and further recovered. The final gas purity is >95%. In this case, the final fluorine extraction rate reached 90.52%, and the phosphoric acid extraction rate was 29.83%.

[0063] Example 2

[0064] Inorganic base NaOH stripping

[0065] Extraction was performed at 40°C. A separatory funnel was charged with an extractant (volume ratio of 1.5:1) and wet-process phosphoric acid (F concentration of 0.40 wt% and P2O5 concentration of 25 wt%). The extractant composition (volume ratio of TOA: n-octanol: sulfonated kerosene = 0.15:0.20:0.65). After 60 minutes, the extractant was separated to produce aqueous phase 1 and oil phase 1, which is the purified wet-process phosphoric acid. NaOH solution was added to oil phase 1 for back extraction. The volume ratio of NaOH solution to organic phase was 1:2. The reaction was allowed to stand at 30°C for 40 minutes, followed by separation to produce aqueous phase 2 and oil phase 2. Aqueous phase 2 was heated and filtered at 70°C. The filtrate was a sodium dihydrogen phosphate solution. The filter cake was dried at 120°C for 6 hours to produce sodium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate was cooled, crystallized, and filtered to produce sodium dihydrogen phosphate crystals. The filtered mother liquor was then dissolved with NaOH and returned to the back extraction process. The oil phase is heated to 50°C for 2 minutes, allowed to stand for 40 minutes, and then separated. The resulting oil phase 3 is trioctylamine, which is recovered and recycled for extraction. The aqueous phase 3 is water, which can dissolve NaOH and then return to the stripping stage. The dried filter cake, fluorosilicate Na2SiF6, is ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas is collected using an air bag. After the reaction is complete, the solid NaF after pyrolysis is collected as a byproduct. The SiF4 gas is purified by liquid nitrogen cryogenic distillation and further recovered. The final gas purity is >95%. In this example, the final fluorine extraction rate reached 85.06%, and the phosphoric acid extraction rate was 28.87%.

[0066] Example 3

[0067] Inorganic salt NaCl stripping

[0068] Extraction was performed at 40°C. A separatory funnel was charged with an extractant (volume ratio of 2:1) and wet-process phosphoric acid (F concentration of 0.40 wt% and P2O5 concentration of 25%). The extractant composition (volume ratio of TOA: n-octanol: sulfonated kerosene = 0.10:0.20:0.70). After 60 minutes, the extractant was separated to produce aqueous phase 1 and oil phase 1, which is the purified wet-process phosphoric acid. NaCl solution was added to oil phase 1 for back extraction. The volume ratio of NaCl solution to organic phase was 1:2. The reaction was allowed to stand at 30°C for 40 minutes, followed by separation to produce aqueous phase 2 and oil phase 2. Aqueous phase 2 was heated and filtered at 70°C. The filtrate was a sodium dihydrogen phosphate solution. The filter cake was dried at 120°C for 6 hours to produce sodium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate was cooled, crystallized, and filtered to produce sodium dihydrogen phosphate crystals. The filtered mother liquor was then used to dissolve the NaCl and return to the back extraction process. Ammonia was added to the oil phase 2 for secondary stripping. After 40 minutes of standing and stratification, the oil phase 3 was separated to obtain trioctylamine, which was recovered and recycled for extraction. The aqueous phase 3 was an ammonium chloride salt solution. The dried filter cake, Na2SiF6 fluorosilicate, was ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas was collected using an air bag. After the reaction was complete, the solid NaF after pyrolysis was collected as a byproduct. The SiF4 gas was purified by liquid nitrogen cryogenic distillation and further recovered. The final gas purity was >95%. In this example, the final fluorine extraction rate reached 88.14%, and the phosphoric acid extraction rate was 25.18%.

[0069] Example 4

[0070] Inorganic salt KCl stripping

[0071] Extraction was performed at 40°C. A separatory funnel was charged with an extractant (volume ratio of 2:1) and wet-process phosphoric acid (F concentration of 0.4 wt% and P2O5 concentration of 25%). The extractant composition (volume ratio of TOA: n-octanol: sulfonated kerosene = 0.10:0.20:0.70). After 60 minutes, the extractant was separated to produce aqueous phase 1 and oil phase 1, which is the purified wet-process phosphoric acid. KCl solution was added to oil phase 1 for back extraction. The volume ratio of KCl solution to organic phase was 1:2. The reaction was allowed to proceed at 30°C for 40 minutes, followed by stratification. Separation then yielded aqueous phase 2 and oil phase 2. Aqueous phase 2 was heated and filtered at 70°C. The filtrate was a potassium dihydrogen phosphate solution. The filter cake was dried at 120°C for 6 hours to produce potassium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate was cooled, crystallized, and filtered to produce potassium dihydrogen phosphate crystals. The filtered mother liquor was then used to dissolve the KCl and return to the back extraction process. Ammonia was added to the oil phase 2 for secondary stripping. After 40 minutes of standing and stratification, the oil phase 3 was separated to obtain trioctylamine, which was recovered and recycled for extraction. The aqueous phase 3 was an ammonium chloride salt solution. The dried filter cake, K2SiF6 fluorosilicate, was ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas was collected using an air bag. After the reaction was complete, the pyrolyzed solid KF was collected as a byproduct. The SiF4 gas was purified by cryogenic distillation with liquid nitrogen and further recovered. The final gas purity was >95%. In this case, the final fluorine extraction rate reached 82.30%, and the phosphoric acid extraction rate was 22.19%.

[0072] Example 5

[0073] Inorganic salt KNO3 stripping

[0074] Extraction was performed at 40°C. A separatory funnel was charged with a 1:1 volume ratio of extractant and wet-process phosphoric acid (F concentration: 0.32 wt% and P2O5 concentration: 25%). The extractant composition (volume ratio: TOA: n-octanol: sulfonated kerosene = 0.15:0.15:0.70). After 60 minutes, the extractant was separated to produce aqueous phase 1 and oil phase 1, which is the purified wet-process phosphoric acid. KNO3 solution was added to oil phase 1 for stripping. The volume ratio of KNO3 solution to organic phase was 1:2. The reaction was allowed to proceed at 30°C for 40 minutes, followed by stratification. Separation then yielded aqueous phase 2 and oil phase 2. Aqueous phase 2 was heated and filtered at 70°C. The filtrate was a potassium dihydrogen phosphate solution. The filter cake was dried at 120°C for 6 hours to produce potassium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate was cooled, crystallized, and filtered to produce potassium dihydrogen phosphate crystals. The filtered mother liquor was then used to dissolve KNO3 and return to the stripping stage. Ammonia was added to the oil phase 2 for secondary stripping. After 40 minutes of standing and stratification, the layers were separated to obtain the oil phase 3, trioctylamine N235, which was recovered and recycled for extraction. The aqueous phase 3 was an ammonium nitrate salt solution. The dried filter cake, fluorosilicate K2SiF6, was ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas was collected using an air bag. After the reaction was complete, the pyrolyzed solid KF was collected as a byproduct. The SiF4 gas was purified by cryogenic distillation with liquid nitrogen and further recovered. The final gas purity was >95%. In this case, the final fluorine extraction rate reached 64.79%, and the phosphoric acid extraction rate was 13.31%.

[0075] Comparative Example 1

[0076] Inorganic base KOH stripping

[0077] Extraction was performed at 40°C. A separatory funnel was charged with a 1:1 volume ratio of extractant and wet-process phosphoric acid (F concentration: 0.32 wt% and P2O5 concentration: 25 wt%). The extractant composition (volume ratio: TOA: n-octanol: sulfonated kerosene = 0.05:0.15:0.70). After 60 minutes, the extractant was separated to produce aqueous phase 1 and oil phase 1, which is the purified wet-process phosphoric acid. KOH solution was added to oil phase 1 for back extraction. The volume ratio of KOH solution to organic phase was 1:2. The reaction was allowed to proceed at 30°C for 40 minutes, and after stratification, the extractant was separated to produce aqueous phase 2 and oil phase 2. Aqueous phase 2 was heated and filtered at 70°C. The filtrate was a potassium dihydrogen phosphate solution. The filter cake was dried at 120°C for 6 hours to produce potassium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate was cooled, crystallized, and filtered to produce potassium dihydrogen phosphate crystals. The filtered mother liquor was then dissolved with KOH and returned to the back extraction process. The oil phase is heated to 50°C for 2 minutes, allowed to stand for 40 minutes, and then separated. The resulting oil phase 3 is trioctylamine, which is recovered for re-extraction. The aqueous phase 3 is water, which can dissolve KOH and then be returned to the stripping stage. The dried filter cake, K2SiF6 fluorosilicate, is ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas is collected using a gas bag. After the reaction is complete, the pyrolyzed solid KF is collected as a byproduct. The SiF4 gas is purified by cryogenic distillation with liquid nitrogen and further recovered. The final gas purity is >95%. In this case, the final fluorine extraction rate reached 18.86%, and the phosphoric acid extraction rate was 6.82%.

[0078] Comparative Example 2

[0079] Inorganic salt KCl stripping

[0080] Extraction was performed at 40°C. A separatory funnel was charged with an extractant (volume ratio of 0.25:1) and wet-process phosphoric acid (F concentration of 0.40 wt% and P2O5 concentration of 25%). The extractant composition (volume ratio of TOA: n-octanol: sulfonated kerosene = 0.15:0.20:0.65). After 60 minutes, the extractant was separated to produce aqueous phase 1 and oil phase 1, which is the purified wet-process phosphoric acid. KCl solution was added to oil phase 1 for back extraction. The volume ratio of KCl solution to organic phase was 1:2. The reaction was allowed to proceed at 30°C for 40 minutes, followed by stratification. The resulting phases were then separated to produce aqueous phase 2 and oil phase 2. Aqueous phase 2 was heated and filtered at 70°C. The filtrate was a potassium dihydrogen phosphate solution. The filter cake was dried at 120°C for 6 hours to produce potassium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate was cooled, crystallized, and filtered to produce potassium dihydrogen phosphate crystals. The filtered mother liquor was then used to dissolve the KCl and return to the back extraction process. Ammonia was added to the oil phase 2 for secondary stripping. After 40 minutes of standing and stratification, the oil phase 3 was separated, resulting in trioctylamine N235. This was recovered and recycled for extraction. The aqueous phase 3 was an ammonium chloride salt solution. The dried filter cake, fluorosilicate K2SiF6, was ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas was collected using an air bag. After the reaction was complete, the pyrolyzed solid KF was collected as a byproduct. The SiF4 gas was purified by cryogenic distillation with liquid nitrogen and further recovered. The final gas purity was >95%. In this case, the final fluorine extraction rate reached 33.91%, and the phosphoric acid extraction rate was 10.02%.

[0081] Comparative Example 3

[0082] Inorganic salt KNO3 stripping

[0083] Extraction was performed at 25°C. A separatory funnel was charged with an extractant (volume ratio of 3:1) and wet-process phosphoric acid (F concentration of 0.4 wt% and P2O5 concentration of 25%). The extractant composition was TOA: n-octanol: sulfonated kerosene (volume ratio = 0.10:0.10:0.80). After 60 minutes, the extractant was separated to produce aqueous phase 1 and oil phase 1, which was the purified wet-process phosphoric acid. KNO3 solution was added to oil phase 1 for stripping. The volume ratio of KNO3 solution to organic phase was 1:2. The reaction was allowed to proceed at 30°C for 40 minutes, followed by stratification. Separation then yielded aqueous phase 2 and oil phase 2. Aqueous phase 2 was heated and filtered at 70°C. The filtrate was a potassium dihydrogen phosphate solution. The filter cake was dried at 120°C for 6 hours to produce potassium fluorosilicate solid with a moisture content of less than 0.1% after drying. The filtrate was cooled, crystallized, and filtered to produce potassium dihydrogen phosphate crystals. The filtered mother liquor was then used to dissolve KNO3 and returned to the stripping stage. Ammonia was added to the oil phase 2 for secondary stripping. After 40 minutes of standing and stratification, the oil phase 3 was separated, resulting in trioctylamine N235, which was recovered and recycled for extraction. The aqueous phase 3 was an ammonium nitrate salt solution. The dried filter cake, K2SiF6 fluorosilicate, was ground and calcined at 500°C under a nitrogen atmosphere for 2 hours. SiF4 gas was collected using an air bag. After the reaction was complete, the pyrolyzed solid KF was collected as a byproduct. The SiF4 gas was purified by cryogenic distillation with liquid nitrogen and further recovered. The final gas purity was >95%. In this case, the final fluorine extraction rate reached 82.42%, and the phosphoric acid extraction rate was 35.14%.

[0084] Table 1: Comparison of fluorine and phosphorus extraction rates in cases

[0085]

Claims

1. A wet-process phosphoric acid defluorination extractant, characterized in that: The extractant is prepared by mixing an organic amine, a cosolvent and a diluent in a volume ratio of 10-100:0-30:0-90, and the content of the cosolvent and the diluent is not 0; the organic amine includes a primary amine RNH2, a secondary amine R2NH, a tertiary amine R3N, a quaternary ammonium base R4N + OH - At least one of the following, wherein R is a hydrocarbon group; the cosolvent includes at least one of n-butanol, n-hexanol, cyclohexanol, 2-ethyl-1-hexanol, and n-octanol; the diluent includes at least one of sulfonated kerosene, n-dodecane, isomeric dodecane, n-tetradecane, n-hexadecane, and 260# solvent oil.

2. The wet-process phosphoric acid defluorination extractant according to claim 1, characterized in that: The extractant is prepared by mixing organic amine, cosolvent and diluent in a volume ratio of 10-15:10-20:65-75.

3. A method for defluorination by wet-process phosphoric acid extraction, characterized in that: The method for defluorination by wet-process phosphoric acid extraction comprises: A extraction: using the extractant according to claim 1 or 2 to extract fluorosilicic acid in the wet-process phosphoric acid raw material at 10-70° C., and phase separation to obtain purified phosphoric acid and an organic phase loaded with fluorosilicate; B. Stripping: reacting the organic phase with a stripping agent, separating the phases to obtain a fluorosilicate solution and a regenerated organic phase, wherein the stripping agent is an inorganic alkali aqueous solution or an inorganic salt aqueous solution; C. Extractant regeneration: adding ammonia water to the regenerated organic phase to obtain an ammonium salt solution and a regenerated extractant, or heating the regenerated organic phase to obtain an aqueous solution and a regenerated extractant. The regenerated extractant is returned to step A for recycling, and the aqueous solution is returned to step B for preparing a stripping agent.

4. The method for defluorination by wet-process phosphoric acid extraction according to claim 3, characterized in that: The method further comprises pre-treating the wet-process phosphoric acid raw material before extraction in step A: adding a silicon replenisher to the wet-process phosphoric acid raw material, wherein the silicon replenisher is 1.1 to 1.2 times the theoretical value, reacting at 10 to 90° C. for 20 to 40 minutes, aging for 1 hour, and filtering to obtain the pre-treated wet-process phosphoric acid raw material.

5. The method for defluorination by wet-process phosphoric acid extraction according to claim 4, characterized in that: The silicon supplementing agent is silicon dioxide, diatomaceous earth or sodium silicate.

6. The method for defluorination by extraction of wet-process phosphoric acid according to claim 3 or 4, characterized in that: The wet-process phosphoric acid raw material in step A includes wet-process phosphoric acid, slag acid produced during the wet-process phosphoric acid concentration process, first-stage acid during the wet-process phosphoric acid concentration process, second-stage acid during the wet-process phosphoric acid concentration process, raffinate acid produced as a by-product of refined phosphoric acid, or two raffinate acids from a TBP process; preferably, the wet-process phosphoric acid raw material has a mass concentration of 20% to 48% in terms of P2O5.

7. The method for defluorination by extraction of wet-process phosphoric acid according to claim 3 or 4, characterized in that: The mass concentration of fluorine in the wet-process phosphoric acid raw material in step A is 0.1 wt.% to 10.0 wt.%, preferably 1.5 wt.% to 2.0 wt.%; the extraction time in step A is preferably 10 to 90 minutes, and the volume ratio of the extractant to the wet-process phosphoric acid raw material is preferably 1 to 2; more preferably, the volume ratio of the extractant to the wet-process phosphoric acid raw material is 1.5 to 2.

8. The method for defluorination by extraction of wet-process phosphoric acid according to claim 3 or 4, characterized in that: The fluorine extraction rate of the extraction in step A is above 60%, and the phosphoric acid extraction rate is below 30%; preferably, the fluorine extraction rate is above 82%.

9. The method for defluorination by extraction of wet-process phosphoric acid according to claim 3 or 4, characterized in that: In step B, the volume ratio of the organic phase to the stripping agent is 2:1 to 1:5, the stripping temperature is 10 to 70° C., and the inorganic base is preferably KOH or NaOH.

10. The method for defluorination by extraction of wet-process phosphoric acid according to claim 3 or 4, characterized in that: The method also includes fluorine resource recovery: The fluorosilicate solution of step B is subjected to solid-liquid separation at 70-90° C. to obtain a fluorosilicate ointment and a filtrate, the fluorosilicate ointment is dried to obtain a solid product fluorosilicate, and the solid product fluorosilicate is pyrolyzed at 200-800° C. to generate SiF4 and a fluoride salt, or acidolyzed at 95-105% sulfuric acid to generate SiF4 and HF; Preferably, the pyrolysis is carried out under a nitrogen atmosphere, the pyrolysis temperature of fluorosilicate K2SiF6 is 400-600°C, and the pyrolysis temperature of Na2SiF6 is 300-800°C; Phosphoric acid recovery: the filtrate is cooled and crystallized, and solid-liquid separation is performed to obtain phosphate solid and mother liquor, and the mother liquor is recycled for the stripping step.

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