CN113415793A - Method for preparing high-purity iron phosphate from lithium iron phosphate battery waste - Google Patents
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Abstract
The invention discloses a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste, and belongs to the technical field of battery waste resource recovery. The method comprises the steps of firstly, separating and enriching valuable metal lithium in lithium iron phosphate battery waste by adopting an oxidation lithium extraction process, then carrying out high-phosphoric acid iron-soluble treatment on leaching residues, and carrying out solid-liquid separation after the reaction is finished to obtain insoluble substances and leaching liquid; diluting the leachate, adjusting the pH value, and preparing high-purity iron phosphate through high-temperature crystallization; the crystallized residual liquid is subjected to a phosphoric acid regeneration-evaporation concentration process to realize the regeneration cycle of the initial phosphoric acid. The method has short process flow, no additional neutralizer, precipitator and acid introduction, low cost and environmental friendliness; the prepared high-purity ferric phosphate can be used for preparing materials such as lithium ion batteries, ceramics, catalysts and the like, and has high added value. The invention solves the problems of environmental pollution and resource waste caused by the waste of the lithium iron phosphate batteries, and provides a new idea for the efficient and economic recycling of the waste of the lithium iron phosphate batteries.
Description
Technical Field
The invention belongs to the technical field of battery waste resource recovery, and particularly relates to a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste.
Background
In recent years, the new energy industry has been rapidly developed, and among them, the development of lithium ion batteries is most remarkable. At present, lithium ion batteries are widely applied in industries such as mobile phones, computers, new energy vehicles and energy storage stations. The lithium iron phosphate lithium ion battery has the advantages of high safety, good thermal stability, low price and little pollution, and the loading capacity of the lithium iron phosphate in China in 2019 reaches 13.8GWH only used for a power battery of an electric motor coach. When lithium iron phosphate is widely applied, a large number of lithium iron phosphate batteries are scrapped and eliminated, and the quantity of lithium iron phosphate battery wastes is increased rapidly.
At present, the recovery of lithium iron phosphate battery waste mainly adopts a wet recovery process: one is to realize the comprehensive recovery of valuable metals through the procedures of strong acid leaching, impurity removal, neutralization and precipitation and the like; and the other method is to realize the repair and regeneration of the lithium iron phosphate battery by supplementing lithium, iron and phosphorus. The Chinese patent application CN 104362408A discloses a method for comprehensively recycling lithium iron phosphate battery waste, which comprises the steps of firstly processing pole pieces of the lithium iron phosphate battery waste at high temperature, then separating lithium iron phosphate from a current collector aluminum foil, then baking and screening the stripped lithium iron phosphate at high temperature to obtain lithium iron phosphate powder, and finally regenerating a lithium iron phosphate positive electrode material by repairing. Due to the fact that the lithium iron phosphate battery waste has large component fluctuation, the purity of the regenerated material is low, and the electrical performance is poor, the method cannot achieve comprehensive recycling of a large amount of lithium iron phosphate battery waste. The Chinese patent application CN 103280610A discloses a method for recovering a lithium iron phosphate battery positive plate, which comprises the steps of firstly, treating the lithium iron phosphate positive plate by adopting alkali dissolution to obtain a lithium-containing solution and filter residue containing ferric phosphate, adding a 95 ℃ saturated sodium carbonate solution into the lithium-containing solution, and preparing lithium carbonate by precipitation; the filter residue is firstly dissolved by mixed acid, so that iron exists in the form of ferric phosphate precipitate and is separated from impurities such as carbon black and the like. The method has the advantages of high acid and alkali consumption, incapability of realizing the regeneration and cyclic utilization of acid and alkali, high process cost, generation of a large amount of waste water and waste residues, and no contribution to the economic and efficient treatment of the lithium iron phosphate battery waste.
Therefore, the method develops a simple, efficient and environment-friendly recovery process of the lithium iron phosphate battery waste, realizes resource utilization of the lithium iron phosphate battery waste, and has important significance.
Disclosure of Invention
Aiming at the problems of complex working procedures, high reagent consumption, incapability of recycling reagents, high cost, low purity of the recovered iron phosphate and the like in the recovery process of the lithium iron phosphate battery waste in the prior art, the invention provides a method for preparing high-purity iron phosphate from the lithium iron phosphate battery waste, which comprises the steps of firstly separating and enriching valuable metallic lithium in the lithium iron phosphate battery waste by adopting an oxidation lithium extraction process, then carrying out concentrated phosphoric acid iron dissolution treatment on leaching slag, and carrying out solid-liquid separation after the reaction is finished to obtain insoluble substances and leaching solution; diluting the leachate, adjusting the pH value, and preparing high-purity iron phosphate through high-temperature crystallization; the crystallized residual liquid is subjected to a phosphoric acid regeneration-evaporation concentration process to realize the regeneration cycle of the initial phosphoric acid. The method has the advantages of short process flow, no introduction of additional neutralizing agent, precipitator and acid, low cost and environmental friendliness; the prepared high-purity ferric phosphate can be used for preparing materials such as lithium ion batteries, ceramics, catalysts and the like, and has high added value.
The purpose of the invention is realized by the following technical scheme:
a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste comprises the following steps:
(1) and (3) oxidizing to extract lithium: adding an oxidant and low-concentration organic acid into the lithium iron phosphate battery waste to be treated, and performing solid-liquid separation after the reaction is finished to obtain a lithium-rich leaching solution and leaching residues with main phases of iron phosphate;
(2) concentrated phosphoric acid dissolved iron: adding high-concentration phosphoric acid into the leaching residue, and after the reaction is finished, carrying out solid-liquid separation to obtain insoluble substances and a leaching solution;
(3) high-temperature crystallization: adding water into the leachate obtained in the step (2) for dilution, then adding iron phosphate seed crystals and a surfactant, completing crystallization of iron phosphate at high temperature, carrying out solid-liquid separation to obtain a crystallization residual liquid and a crystallization product, and drying the crystallization product to obtain iron phosphate;
(4) regeneration of phosphoric acid: treating the crystallized residual liquid in the step (3) by adopting a membrane separation process, and controlling the temperature and pressure of phosphoric acid feeding and the flow rate of phosphoric acid production to obtain phosphoric acid which is preliminarily concentrated to 40-60% in mass fraction;
(5) and (3) evaporation and concentration: and (3) further concentrating the phosphoric acid obtained in the step (4) by adopting an evaporation concentration process to obtain regenerated phosphoric acid, and returning to the step (2) for recycling.
Further, the waste lithium iron phosphate batteries in the step (1) include one or more of waste lithium iron phosphate batteries, waste pole pieces and waste lithium iron phosphate.
Further, the oxidizing agent in step (1) comprises hydrogen peroxide or oxygen.
Further, the organic acid in step (1) comprises one or more of citric acid, tartaric acid and malic acid.
Further, the concentration of the phosphoric acid in the step (2) is 3-6 mol/L.
Further, the solid-to-liquid ratio of the concentrated iron phosphate in the step (2) is 1:4-1:10g/mL, the reaction temperature is controlled at 70-95 ℃, the stirring speed is set at 300-500rpm, and the reaction time is 0.5-5 h.
Further, the adding amount of water in the step (3) is 1-4 times of the volume of the leaching solution, and the pH control range is 1.2-2.6.
Further, the adding amount of the iron phosphate seed crystal in the step (3) is 10-50% of the mass fraction of the iron content in the leachate in the step (2).
Further, the type of the surfactant in the step (3) comprises one of CTAB, SDS and SDBS, and the addition amount of the surfactant is 0.1-0.5% of the mass fraction of the iron content in the leachate in the step (2).
Further, the crystallization temperature in the step (3) is 85-95 ℃, the time is 1-12h, and the stirring speed is 150-400 rpm.
Further, the crystalline product in the step (3) is dried in an oven at 60 ℃ for 8 hours to obtain the iron phosphate.
Further, the membrane separation process in the step (4) comprises one or more combined processes of microfiltration, ultrafiltration, nanofiltration, bipolar membrane, reverse dialysis and electrodialysis.
Further, in the step (4), the phosphoric acid feeding temperature is 25-75 ℃, the phosphoric acid feeding pressure is 1.2-4.0MPa, and the phosphoric acid production flow is controlled to be 40-150L/h.
Further, the evaporation concentration process in the step (5) adopts an MVR evaporator or a multi-effect evaporator, and the mass fraction of the concentrated phosphoric acid is 65-85%.
The technical scheme of the invention is realized by the following principle:
in the step (2) of the method, concentrated iron phosphate reacts with ferric phosphate in the leaching residue of the oxidized lithium extraction by high-concentration phosphoric acid to generate iron phosphate acid salt, so that the dissolution of iron is efficiently separated from other impurities, and the main reaction is as follows:
2FePO4+H3PO4→Fe2HPO4 4++2HPO4 2- (2)
FePO4+H3PO4→FeHPO4 ++H2PO4 - (3)
and (3) crystallizing in the range of pH not less than 1.2 and not more than 2.6 in the step (3), and realizing the preparation of the high-purity iron phosphate by utilizing the characteristics that the iron phosphate has low solubility at high temperature and is easy to precipitate. The mass fraction of the iron content in the prepared iron phosphate is 29.2-30%, and the mass fraction of the phosphorus content is 16.5-17%. The main reactions that occur are:
in the step (4), when the phosphoric acid is regenerated, impurity elements are removed by adopting a membrane separation technology and utilizing the separation performance of different membranes, so that the method can be used for lithium extraction operation, and further improves the comprehensive economic benefit of the method.
The technical scheme shows that: according to the scheme for preparing the high-purity iron phosphate by using the lithium iron phosphate battery waste, valuable metal lithium is efficiently separated and enriched, and the dissolution of iron in the lithium iron phosphate battery waste and the preparation of the high-purity iron phosphate are realized by using the characteristic that the iron phosphate is soluble in high-concentration phosphoric acid and the property that the solubility of the iron phosphate is reduced when the temperature is increased. The crystallized residual liquid can be regenerated and recycled by phosphoric acid regeneration-evaporation concentration. The method flexibly utilizes the iron phosphate dissolution characteristic, only needs a small amount of supplementary phosphoric acid in the whole process, does not introduce other reagents, realizes efficient and economic recycling of the waste of the lithium iron phosphate battery, and has the advantages of simple process flow, high resource utilization rate and small influence on the environment. The invention flexibly utilizes the solubility characteristic of the lithium iron phosphate in high-concentration phosphoric acid and the property that the solubility of the iron phosphate is reduced along with the rise of the temperature, solves the problems of environmental pollution and resource waste caused by the waste of the lithium iron phosphate battery, and provides a new idea for the efficient and economic recycling of the waste of the lithium iron phosphate battery.
Compared with the prior art, the technical scheme of the invention has the following technical advantages or positive effects:
(1) the method has strong adaptability of raw materials, and waste lithium iron phosphate batteries, waste pole pieces, lithium iron phosphate waste materials and the like can be used as the raw materials in the technical scheme of the invention;
(2) the method has the advantages of low reagent consumption, no need of additional neutralizing agent and precipitating agent, and realization of high-efficiency separation and enrichment of valuable metal lithium;
(3) the method fully utilizes iron and phosphorus resources in the lithium iron phosphate waste to produce the high-purity iron phosphate, the phosphoric acid in the whole process can be recycled, the phosphoric acid supplement amount is very small, the process cost is low, and the environment friendliness is high;
(4) the method has simple process flow and high added value of the iron phosphate product, and is suitable for recycling and treating a large amount of lithium iron phosphate battery waste.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a process flow diagram for preparing high-purity iron phosphate from the waste lithium iron phosphate battery according to the present invention.
Fig. 2 is a microscopic topography of iron phosphate prepared in example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.
Example 1
As shown in fig. 1, a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste comprises: adding hydrogen peroxide and a small amount of tartaric acid into the lithium iron phosphate battery waste to complete oxidation lithium extraction, and obtaining a lithium-rich leaching solution and leaching residues; then adding 4mol/L phosphoric acid into the leaching residue, wherein the solid-to-liquid ratio is as follows: 1:4g/mL, controlling the reaction temperature to be 85 ℃, setting the stirring speed to be 500rpm, and controlling the reaction time to be 2 hours; separating solid from liquid to obtain insoluble substance and leachate. Adding 1 volume of water into the leachate for dilution, maintaining the pH of the system at 1.2, adding 10% of ferric phosphate serving as a seed crystal and CTAB (cetyltrimethyl ammonium bromide) serving as a surfactant, wherein the iron content is 0.1%, the crystallization temperature is 95 ℃, the time is 6 hours, and the stirring speed is 150 rpm; and after the crystallization is finished, carrying out solid-liquid separation, drying the crystallized product in a 60 ℃ oven for 8h to obtain ferric phosphate dihydrate, wherein the microscopic morphology of the prepared ferric phosphate is shown in figure 2. The regeneration of phosphoric acid is realized by adopting an ultrafiltration-bipolar membrane-electrodialysis combined process for the crystallization residual liquid, and the regeneration conditions are as follows: the phosphoric acid inlet temperature is 75 ℃, the phosphoric acid inlet pressure is 4.0MPa, the phosphoric acid production flow is 150L/h, and the phosphoric acid concentration is 45%. The removal of large-particle-size impurity ions is realized through ultrafiltration, and then the high-efficiency separation of lithium ions and the preliminary concentration of phosphoric acid are realized by utilizing the combination process of electrodialysis and a bipolar membrane. The phosphoric acid obtained by membrane separation is evaporated and concentrated by a multi-effect evaporator to obtain phosphoric acid with the concentration of 65 percent, and the phosphoric acid can be continuously recycled.
Example 2
As shown in fig. 1, a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste comprises: adding a small amount of citric acid into the lithium iron phosphate battery waste, and introducing oxygen to complete oxidation lithium extraction to obtain a lithium-rich leaching solution and leaching residues; then adding 5mol/L phosphoric acid into the leached residues, wherein the solid-liquid ratio is as follows: 1:6g/mL, controlling the reaction temperature to be 90 ℃, setting the stirring speed to be 500rpm, and controlling the reaction time to be 4 hours; separating solid from liquid to obtain insoluble substance and leachate. Adding 1 volume of water into the leachate for dilution, maintaining the pH of the system at 1.8, adding 20% of ferric phosphate serving as seed crystal and SDBS (sodium dodecyl benzene sulfonate) serving as surfactant, wherein the iron content is 0.5%, the crystallization temperature is 95 ℃, the time is 12 hours, and the stirring speed is 150 rpm; and after the crystallization is finished, carrying out solid-liquid separation, and drying the crystallized product in a 60 ℃ oven for 8 hours to obtain ferric phosphate dihydrate, wherein the iron content in the ferric phosphate is 29.6 percent, and the phosphorus content is 16.5 percent. The regeneration of phosphoric acid is realized by adopting an ultrafiltration-nanofiltration combined process for the crystallized residual liquid, and the regeneration conditions are as follows: the phosphoric acid inlet temperature is 30 ℃, the phosphoric acid inlet pressure is 1.8MPa, the phosphoric acid production flow is 120L/h, and the phosphoric acid concentration is 40%. Ultrafiltration is adopted to realize the removal of impurity ions with large particle size, and then the nanofiltration process is utilized to achieve the aim of purifying and concentrating the phosphoric acid. And (3) evaporating and concentrating the phosphoric acid obtained by membrane separation by adopting an MVR evaporator to obtain 85% phosphoric acid, and continuously recycling.
Example 3
As shown in fig. 1, a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste comprises: adding hydrogen peroxide and a small amount of citric acid into the lithium iron phosphate battery waste to complete oxidation lithium extraction, and obtaining a lithium-rich leaching solution and leaching residues; then adding 6mol/L phosphoric acid into the leached residues, wherein the solid-liquid ratio is as follows: 1:8g/mL, controlling the reaction temperature at 70 ℃, setting the stirring speed at 400rpm for 5 hours; separating solid from liquid to obtain insoluble substance and leachate. Adding 4 times volume of water into the leachate for dilution, maintaining the pH value of the system at 2.6, adding 50% of ferric phosphate serving as seed crystal and SDBS (sodium dodecyl benzene sulfonate) serving as surfactant with the iron content of 0.2%, wherein the crystallization temperature is 90 ℃, the time is 1h, and the stirring speed is 300 rpm; and after the crystallization is finished, carrying out solid-liquid separation, and drying the crystallized product in a 60 ℃ oven for 8 hours to obtain the ferric phosphate dihydrate. Removing impurity elements from the crystallized residual liquid by adopting a nanofiltration process to realize phosphoric acid regeneration, wherein the regeneration conditions are as follows: the temperature of the phosphoric acid is 25 ℃, the pressure of the phosphoric acid is 2.5MPa, the flow rate of the phosphoric acid is 80L/h, and the concentration of the phosphoric acid is 60 percent. And (3) evaporating and concentrating the phosphoric acid obtained by membrane separation by adopting an MVR evaporator to obtain 85% phosphoric acid, and continuously recycling.
Example 4
As shown in fig. 1, a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste comprises: adding hydrogen peroxide and a small amount of malic acid into the lithium iron phosphate battery waste to complete oxidation lithium extraction, and obtaining a lithium-rich leaching solution and leaching residues; then adding 3mol/L phosphoric acid into the leached residues, wherein the solid-liquid ratio is as follows: 1:10g/mL, controlling the reaction temperature at 95 ℃, setting the stirring speed at 350rpm for 0.5 h; separating solid from liquid to obtain insoluble substance and leachate. Adding 3 times volume of water into the leachate for dilution, maintaining the pH of the system at 1.5, adding 40% of ferric phosphate serving as a seed crystal and SDS (sodium dodecyl sulfate) with the iron content of 0.4% serving as a surfactant, wherein the crystallization temperature is 90 ℃, the time is 6 hours, and the stirring speed is 400 rpm; and after the crystallization is finished, carrying out solid-liquid separation, and drying the crystallized product in a 60 ℃ oven for 8 hours to obtain the ferric phosphate dihydrate. The regeneration of phosphoric acid is realized by adopting a bipolar membrane-electrodialysis combined process for the crystallization residual liquid, and the regeneration conditions are as follows: the phosphoric acid inlet temperature is 60 ℃, the phosphoric acid inlet pressure is 1.2MPa, the phosphoric acid production flow is 40L/h, and the phosphoric acid concentration is 60%. Under the action of an electric field, the lithium ions and the phosphate radicals are separated efficiently. The phosphoric acid obtained by membrane separation is evaporated and concentrated by a multi-effect evaporator to obtain 85% phosphoric acid, which can be recycled.
Example 5
As shown in fig. 1, a method for preparing high-purity iron phosphate from lithium iron phosphate battery waste comprises: adding a small amount of tartaric acid into the lithium iron phosphate battery waste, and introducing oxygen to complete oxidation lithium extraction to obtain a lithium-rich leaching solution and leaching residues; then adding 6mol/L phosphoric acid into the leached residues, wherein the solid-liquid ratio is as follows: 1:10g/mL, controlling the reaction temperature at 90 ℃, setting the stirring speed at 300rpm for 1 h; separating solid from liquid to obtain insoluble substance and leachate. Adding 2 times volume of water into the leachate for dilution, maintaining the pH value of the system at 2.2, adding 40% of ferric phosphate serving as a seed crystal and CTAB (cetyl trimethyl ammonium bromide) serving as a surfactant with the iron content of 0.5%, wherein the crystallization temperature is 85 ℃, the crystallization time is 6 hours, and the stirring speed is 200 rpm; and after the crystallization is finished, carrying out solid-liquid separation, and drying the crystallized product in a 60 ℃ oven for 8 hours to obtain ferric phosphate dihydrate, wherein the iron content in the ferric phosphate is 29.8 percent, and the phosphorus content is 16.6 percent. The regeneration of phosphoric acid is realized by adopting a reverse dialysis-ultrafiltration combined process for the crystallized residual liquid, and the regeneration conditions are as follows: the phosphoric acid inlet temperature is 30 ℃, the phosphoric acid inlet pressure is 3.0MPa, the phosphoric acid production flow is 130L/h, and the phosphoric acid concentration is 54 percent. And (3) evaporating and concentrating the phosphoric acid obtained by membrane separation by adopting an MVR evaporator to obtain 85% phosphoric acid, and continuously recycling.
In conclusion, in the embodiment of the invention, the high-concentration phosphoric acid is used for treating the lithium iron phosphate battery waste to dissolve out iron in the lithium iron phosphate battery waste, the leachate is crystallized at high temperature to prepare high-purity iron phosphate, the crystallized residual liquid is subjected to regeneration and cyclic utilization of phosphoric acid through a phosphoric acid regeneration-evaporation concentration process, no neutralizer or precipitator is introduced in the whole process, and valuable metal lithium is efficiently separated and enriched, so that a new idea is provided for efficient utilization and industrial application of the lithium iron phosphate battery waste.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. The method for preparing high-purity iron phosphate from the lithium iron phosphate battery waste is characterized by comprising the following steps of:
(1) and (3) oxidizing to extract lithium: adding an oxidant and low-concentration organic acid into the lithium iron phosphate battery waste to be treated, and performing solid-liquid separation after the reaction is finished to obtain a lithium-rich leaching solution and leaching residues with main phases of iron phosphate;
(2) concentrated phosphoric acid dissolved iron: adding high-concentration phosphoric acid into the leaching residue, and after the reaction is finished, carrying out solid-liquid separation to obtain insoluble substances and a leaching solution;
(3) high-temperature crystallization: adding water into the leachate obtained in the step (2) for dilution, then adding iron phosphate seed crystals and a surfactant, completing crystallization of iron phosphate at high temperature, carrying out solid-liquid separation to obtain a crystallization residual liquid and a crystallization product, and drying the crystallization product to obtain iron phosphate;
(4) regeneration of phosphoric acid: treating the crystallized residual liquid in the step (3) by adopting a membrane separation process, and controlling the temperature and pressure of phosphoric acid feeding and the flow rate of phosphoric acid production to obtain phosphoric acid which is preliminarily concentrated to 40-60% in mass fraction;
(5) and (3) evaporation and concentration: and (3) further concentrating the phosphoric acid obtained in the step (4) by adopting an evaporation concentration process to obtain regenerated phosphoric acid, and returning to the step (2) for recycling.
2. The method for preparing high-purity iron phosphate from the waste lithium iron phosphate batteries according to claim 1, wherein the waste lithium iron phosphate batteries in the step (1) comprise one or more of waste lithium iron phosphate batteries, waste pole pieces and waste lithium iron phosphate.
3. The method for preparing high-purity iron phosphate from lithium iron phosphate battery waste according to claim 1, wherein the oxidizing agent in step (1) comprises hydrogen peroxide or oxygen; the organic acid comprises one or more of citric acid, tartaric acid and malic acid.
4. The method for preparing high-purity iron phosphate from lithium iron phosphate battery waste according to claim 1, wherein the concentration of phosphoric acid in the step (2) is 3 to 6 mol/L; the solid-liquid ratio of the concentrated iron phosphate is 1:4-1:10g/mL, the reaction temperature is controlled at 70-95 ℃, the stirring speed is set at 300-500rpm, and the reaction time is 0.5-5 h.
5. The method for preparing high-purity iron phosphate from the lithium iron phosphate battery waste according to claim 1, wherein the water is added in the step (3) in an amount of 1-4 times the volume of the leachate, and the pH is controlled within a range of 1.2-2.6; the addition amount of the iron phosphate seed crystal is 10-50% of the mass fraction of the iron content in the leachate obtained in the step (2); the type of the surfactant comprises one of CTAB, SDS and SDBS, and the addition amount of the surfactant is 0.1-0.5% of the mass fraction of the iron content in the leachate obtained in the step (2).
6. The method for preparing high-purity iron phosphate from the lithium iron phosphate battery waste as claimed in claim 1, wherein the crystallization temperature in the step (3) is 85-95 ℃, the time is 1-12h, and the stirring speed is 150-400 rpm.
7. The method for preparing high-purity iron phosphate from the lithium iron phosphate battery waste material as claimed in claim 1, wherein the crystalline product obtained in the step (3) is dried in an oven at 60 ℃ for 8 hours to obtain the iron phosphate.
8. The method for preparing high-purity iron phosphate from the lithium iron phosphate battery waste material as claimed in claim 1, wherein the membrane separation process in the step (4) comprises one or more combined processes of microfiltration, ultrafiltration, nanofiltration, bipolar membrane, reverse dialysis and electrodialysis.
9. The method for preparing high-purity iron phosphate from the lithium iron phosphate battery waste material as claimed in claim 1, wherein the phosphoric acid feeding temperature in the step (4) is 25-75 ℃, the phosphoric acid feeding pressure is 1.2-4.0MPa, and the flow rate of the generated phosphoric acid is controlled to be 40-150L/h.
10. The method for preparing high-purity iron phosphate from the lithium iron phosphate battery wastes as claimed in claim 1, wherein the evaporation concentration process in the step (5) adopts an MVR evaporator or a multi-effect evaporator, and the mass fraction of the concentrated phosphoric acid is 65-85%.
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| CN114394582A (en) * | 2022-01-28 | 2022-04-26 | 四川长虹格润环保科技股份有限公司 | Method for regenerating iron phosphate from phosphorus iron slag after lithium extraction |
| CN114394582B (en) * | 2022-01-28 | 2023-10-27 | 四川长虹格润环保科技股份有限公司 | Method for regenerating ferric phosphate from lithium-extracted ferrophosphorus slag |
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