Method for obtaining iron phosphate and lithium-rich solution from lithium iron phosphate battery powder

Abstract

The invention belongs to the field of lithium ion battery recovery, and relates to a method for obtaining iron phosphate and a lithium-rich solution from lithium iron phosphate battery powder. Adding acid into the lithium iron phosphate battery powder for acid leaching, carrying out ultrasonic treatment and gradient temperature control, and then filtering to obtain an acid leaching solution; copper and aluminum are removed from the pickle liquor in an ion flotation mode, and phosphorus is self-supplemented in situ; chlorine dioxide and ferrate are used as oxidants, ultraviolet irradiation is assisted to strengthen the oxidation synergistic effect, ferrous oxide is added, and pH is adjusted to achieve the purpose of iron precipitation; and separating to obtain iron phosphate precipitate and ferrophosphorus post-liquid, washing the iron phosphate precipitate to obtain iron phosphate, and carrying out activated carbon decoloration, ammonia resin adsorption and vacuum evaporation crystallization on the ferrophosphorus post-liquid to obtain the battery-grade lithium carbonate. According to the method, the technological process is green and safe, a dangerous oxidizing agent is not used, lithium, iron and phosphorus in the lithium iron phosphate battery powder can be efficiently recycled, and differentiated innovation is formed in four core links of leaching efficiency, impurity removal and phosphorus supplement cooperation, oxidation depth and product purity.

Description

Technical Field

[0001] This invention relates to a method for the synergistic recovery of high-purity iron phosphate and battery-grade lithium salt from lithium iron phosphate battery powder, belonging to the field of lithium-ion battery recycling. Background Art

[0002] With the rapid development of the new energy vehicle and energy storage markets, the demand for lithium iron phosphate batteries is constantly increasing, which also brings about a large number of waste battery disposal and recycling problems. Recycling waste lithium iron phosphate batteries not only helps reduce environmental pollution but is also an important way to achieve resource recycling. Lithium iron phosphate battery recycling technologies mainly include physical, chemical, and biological methods. Physical methods achieve preliminary separation of materials through crushing, screening, and magnetic separation, but often cannot achieve high-purity metal recovery. Chemical methods, especially hydrometallurgy, achieve metal leaching and purification through chemical processes such as acid leaching and alkali leaching, and are currently the most widely used recycling methods. Biological methods utilize microbial metabolic processes for metal leaching, but are still in the laboratory research stage.

[0003] In terms of patented technology, several patents already relate to the recycling and reuse of lithium iron phosphate batteries. For example, a method for preparing lithium iron phosphate cathode material from waste lithium iron phosphate batteries maximizes the utilization of useful resources in waste batteries through steps such as acid leaching, impurity removal, and lithium precipitation. The recovered lithium iron phosphate has high purity, with iron and phosphorus recovery rates exceeding 95% and lithium recovery rates exceeding 90%, effectively achieving full component recovery. Traditional processes use hydrogen peroxide to oxidize ferrous iron, posing a risk of storage explosion (CN112299457A); while acid leaching for impurity removal often relies on solvent extraction, generating organic pollution (CN113293272A). This invention addresses safety issues through a chlorine dioxide / ferrate synergistic oxidation system, combined with ion flotation for self-compensation impurity removal technology to avoid phosphorus loss, forming a green closed-loop process.

[0004] With continuous technological advancements and growing market demand, the lithium iron phosphate battery recycling industry is gradually maturing. It is anticipated that future technological innovations and industrial applications will drive improvements in recycling efficiency and reduce costs, leading to more environmentally friendly and economical lithium battery recycling. Simultaneously, government policy support and standardized market management will play a crucial role in the healthy development of the industry. Summary of the Invention

[0005] Technical problems to be solved In existing lithium iron phosphate battery recycling technologies, acid leaching efficiency is limited by the dissolution capacity of a single acid system, ion flotation requires additional phosphorus replenishment, leading to a complex process, and iron precipitation due to insufficient oxidant synergy easily leaves residual ferrous iron, and the purity of regenerated lithium salts is difficult to meet battery-grade standards. This invention addresses these problems by achieving efficient recycling through multi-stage technological innovation.

[0006] The purpose of this invention is to provide a method for the synergistic recovery of high-purity iron phosphate and battery-grade lithium salt from lithium iron phosphate battery powder.

[0007] Another objective of this invention is to provide a green and safe method for recycling lithium iron phosphate battery materials that does not use hazardous oxidants. To achieve the above objectives, the present invention includes the following steps: A method for obtaining iron phosphate and lithium-rich solution from lithium iron phosphate battery powder includes the following steps: (1) The lithium iron phosphate battery powder is filtered after acid leaching to obtain the acid leaching solution; (2) Remove copper and aluminum from the acid leaching solution by ion flotation; (3) Add chlorine dioxide solution and ferrate, nano ZnO photocatalyst to the acid leaching solution obtained in step (2), and oxidize it with ultraviolet light to adjust the pH and precipitate iron. (4) The iron phosphate precipitate and the iron phosphate post-liquid are obtained by filtration and separation. The iron phosphate precipitate is washed to obtain iron phosphate. The iron phosphate post-liquid is decolorized and impurities are removed to obtain battery-grade lithium carbonate.

[0008] The acid used in step (1) during the acid leaching process includes one or more combinations of sulfuric acid, hydrochloric acid, and nitric acid. The acid leaching temperature is 10~90℃ and the acid leaching time is 0.5~6h.

[0009] In some preferred embodiments, step (1) involves taking lithium iron phosphate battery powder, adding water to it to form a slurry and stirring, using a hydrochloric acid-phosphoric acid mixture (volume ratio 2:1~7:1, preferably 4:1) for acid leaching, while introducing ultrasonic assistance (200~500W, preferably 300W) and using gradient temperature control (20℃→50℃→80℃, with each stage held for 1 hour), and filtering the slurry to obtain the acid leaching solution; wherein the acid excess is 30%~150%, preferably 30~50%, the solid content after adding acid is 10%~30%, preferably 15~25%, and the total acid leaching time is 1~6 hours, preferably 3-5 hours.

[0010] In step (2), the surfactant used in the ion flotation process is a compound of sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) in a mass ratio of 2:1 to 6:1. The compound surfactant is in excess of 0% to 50%. Air is introduced during flotation at a flow rate of 0.8 to 1.5 L / min to enhance separation efficiency.

[0011] The mass ratio of lauroyl-N-methylaminoacetic acid sodium LS to phosphate ester-based gemini surfactant P-Gemini is 3:1; the composite surfactant is in excess by 10-30%.

[0012] In step (3), acid is first added to adjust the pH of the leaching solution to <1. A chlorine dioxide solution with a concentration of 500~1500mg / L is used as the main oxidant. Ferrate is added and nano ZnO photocatalyst is introduced. Ultraviolet light (wavelength 365nm) is used to enhance the synergistic effect of oxidation and efficiently oxidize the ferrous iron in the leaching solution. Then the pH of the leaching solution is adjusted to 2.0~3.0 to achieve high-purity iron precipitation.

[0013] The concentration of chlorine dioxide in the step is 800~1200 mg / L; the excess is 10%~100%, preferably 20%~50%.

[0014] In step (3), the molar ratio of ferrate to chlorine dioxide is 1:10 to 1:2, preferably 1:6.

[0015] The ferrate is one or more of potassium ferrate, sodium ferrate, ammonium ferrate, and lithium ferrate, preferably lithium ferrate.

[0016] The nano-ZnO photocatalyst has a particle size of 100~200nm and is irradiated with ultraviolet light for 0.5~2h, preferably 1h. In step (4), ferric phosphate precipitate and ferric phosphate post-liquid are obtained by filtration separation. The ferric phosphate precipitate is washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain ferric phosphate with a purity ≥99.5%. The ferric phosphate post-liquid is then subjected to activated carbon decolorization, adsorption with aminophosphonic acid chelating resin, and vacuum evaporation crystallization at 40~80℃ to obtain battery-grade lithium carbonate.

[0017] The aminophosphonic acid chelating resin is one of polystyrene skeleton aminophosphonic acid resin, polyacrylic acid skeleton aminophosphonic acid resin, and phenolic resin skeleton aminophosphonic acid resin.

[0018] The chelating resin adsorption flow rate is 1-2 BV / h, preferably 1.5 BV / h.

[0019] This method has a simple process flow, is green and safe, does not use dangerous oxidants, and can efficiently recover lithium iron phosphate from lithium iron phosphate battery powder.

[0020] The acid leaching stage employs a synergistic approach of "mixed acid + ultrasound - gradient temperature control," increasing the leaching rate by 5%~8% and shortening the leaching time by 50% compared to single acid leaching. Ion flotation achieves integrated "impurity removal - phosphorus replenishment" through composite surfactants, eliminating the need for an additional phosphorus source and increasing phosphorus utilization by 40%. The iron oxide precipitation process introduces a "photocatalysis - dual oxidant" system, increasing the ferrous iron oxidation rate from 95% to over 99.9% while reducing oxidant usage by 30%. The lithium-rich solution undergoes deep purification through "chelation-crystallization," raising the lithium purity from industrial grade (95%~98%) to battery grade (≥99.8%), allowing for direct use in cathode material regeneration. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0022] To better understand the present invention, the following description, in conjunction with embodiments and related tables, further illustrates the content of the present invention, but the content of the present invention is not limited to the embodiments described below.

[0023] The lithium iron phosphate battery powder came from a battery recycling and crushing company. Key indicators are shown in Table 1.

[0024] Example 1 (1) Weigh 1 kg of lithium iron phosphate battery powder and calculate the content of lithium, iron, copper, aluminum, titanium and other metals. The volume ratio of hydrochloric acid to phosphoric acid is 4:1, with an acid excess of 30%. Add water to make a slurry and stir, and control the solid content at 20%. Use ultrasonic assistance (300W) and gradient temperature control (20℃→50℃→80℃, keep warm for 1 hour in each stage). The total acid leaching time is 3 hours. After leaching, filter to obtain the acid leaching solution.

[0025] (2) Sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) are compounded at a certain mass ratio of 3:1, with the composite surfactant in excess by 20% (based on the total concentration of aluminum and copper ions in the acid leaching solution). Air is introduced during flotation (flow rate 0.8L / min) to enhance the separation efficiency.

[0026] (3) Add acid to adjust the pH of the acid leaching solution to <1, use chlorine dioxide solution with a concentration of 800 mg / L as the main oxidant, add lithium ferrate and introduce nano ZnO photocatalyst (particle size 100 nm), the molar ratio of lithium ferrate to chlorine dioxide is 1:6, chlorine dioxide is in excess by 20%, and irradiate with ultraviolet light (wavelength 365 nm) for 1 h; then adjust the pH of the acid leaching solution to 2.5 to achieve high-purity iron precipitation.

[0027] (4) The phosphate precipitate and the phosphate effluent were obtained by filtration. The phosphate precipitate was washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain phosphate. The phosphate effluent was then subjected to activated carbon decolorization, polystyrene skeleton aminophosphonic acid resin adsorption (flow rate 1.5 BV / h), and vacuum evaporation crystallization at 70℃ to obtain lithium carbonate.

[0028] The final lithium separation rate, phosphorus and iron recovery rate, and lithium carbonate purity are shown in Table 2, and the main indicators of iron phosphate are shown in Table 3.

[0029] Example 2 First, weigh 1 kg of lithium iron phosphate battery powder. Calculate the content of metals such as lithium, iron, copper, aluminum, and titanium. The volume ratio of hydrochloric acid to phosphoric acid is 4:1, with an acid excess of 50%. Add water to make a slurry and stir, controlling the solid content at 18%. Use ultrasonic assistance (300W) and gradient temperature control (20℃→50℃→80℃, holding for 1 hour at each stage). The total acid leaching time is 4 hours. After leaching, filter to obtain the acid leaching solution. Sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) are compounded at a certain mass ratio of 3:1, with an excess of 10% of the compound surfactant (based on the total concentration of aluminum and copper ions in the acid leaching solution). Air is introduced during flotation (flow rate 0.8 L / min) to enhance the separation efficiency. The pH of the acid leaching solution was adjusted to <1 by adding acid. A chlorine dioxide solution with a concentration of 800 mg / L was used as the main oxidant. Lithium ferrate was added and nano-ZnO photocatalyst (particle size 200 nm) was introduced. The molar ratio of lithium ferrate to chlorine dioxide was 1:6, and chlorine dioxide was added in excess by 50%. The solution was then irradiated with ultraviolet light (wavelength 365 nm) for 1 hour. Subsequently, the pH of the acid leaching solution was adjusted to 2.5 to achieve high-purity iron precipitation. Ferric phosphate precipitate and ferric phosphate post-liquid were obtained by filtration separation. The ferric phosphate precipitate was washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain ferric phosphate. The ferric phosphate post-liquid was then subjected to activated carbon decolorization, adsorption with polyacrylic acid skeleton aminophosphonic acid resin (flow rate 1.5 BV / h), and vacuum evaporation crystallization at 60℃ to obtain lithium carbonate.

[0030] The final lithium separation rate, phosphorus and iron recovery rate, and lithium carbonate purity are shown in Table 2, and the main indicators of iron phosphate are shown in Table 3.

[0031] Example 3 First, weigh 1 kg of lithium iron phosphate battery powder and calculate the content of metals such as lithium, iron, copper, aluminum, and titanium. The volume ratio of hydrochloric acid to phosphoric acid is 4:1, with an acid excess of 40%. Add water to make a slurry and stir, and control the solid content at 25%. Use ultrasonic assistance (300W) and gradient temperature control (20℃→50℃→80℃, with each stage holding for 1 hour). The total acid leaching time is 5 hours. After leaching, filter to obtain the acid leaching solution. Sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) are compounded at a certain mass ratio of 3:1, with the compound surfactant in excess by 30% (based on the total concentration of aluminum and copper ions in the acid leaching solution). Air is introduced during flotation (flow rate 0.8 L / min) to enhance separation efficiency. The pH of the acid leaching solution was adjusted to <1 by adding acid. A chlorine dioxide solution with a concentration of 1000 mg / L was used as the main oxidant. Lithium ferrate was added and nano-ZnO photocatalyst (particle size 150 nm) was introduced. The molar ratio of lithium ferrate to chlorine dioxide was 1:6, and chlorine dioxide was in excess by 30%. The solution was then irradiated with ultraviolet light (wavelength 365 nm) for 1 hour. Subsequently, the pH of the acid leaching solution was adjusted to 2.1 to achieve high-purity iron precipitation. Ferric phosphate precipitate and ferric phosphate post-liquid were obtained by filtration separation. The ferric phosphate precipitate was washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain ferric phosphate. The ferric phosphate post-liquid was then subjected to activated carbon decolorization, phenolic resin skeleton aminophosphonic acid resin adsorption (flow rate 1.5 BV / h), and vacuum evaporation crystallization at 70℃ to obtain lithium carbonate.

[0032] The final lithium separation rate, phosphorus and iron recovery rate, and lithium carbonate purity are shown in Table 2, and the main indicators of iron phosphate are shown in Table 3.

[0033] Example 4 First, weigh 1 kg of lithium iron phosphate battery powder and calculate the content of metals such as lithium, iron, copper, aluminum, and titanium. The volume ratio of hydrochloric acid to phosphoric acid is 4:1, with an acid excess of 30%. Add water to make a slurry and stir, and control the solid content at 22%. Use ultrasonic assistance (300W) and gradient temperature control (20℃→50℃→80℃, with each stage holding for 1 hour). The total acid leaching time is 4 hours. After leaching, filter to obtain the acid leaching solution. Sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) are compounded at a certain mass ratio of 3:1, with the compound surfactant in excess by 20% (based on the total concentration of aluminum and copper ions in the acid leaching solution). Air is introduced during flotation (flow rate 0.8 L / min) to enhance separation efficiency. The pH of the acid leaching solution was adjusted to <1 by adding acid. A chlorine dioxide solution with a concentration of 1200 mg / L was used as the main oxidant. Lithium ferrate was added and nano-ZnO photocatalyst (particle size 100 nm) was introduced. The molar ratio of lithium ferrate to chlorine dioxide was 1:6, and chlorine dioxide was in excess by 40%. The solution was then irradiated with ultraviolet light (wavelength 365 nm) for 1 hour. Subsequently, the pH of the acid leaching solution was adjusted to 2.3 to achieve high-purity iron precipitation. Ferric phosphate precipitate and ferric phosphate post-liquid were obtained by filtration separation. The ferric phosphate precipitate was washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain ferric phosphate. The ferric phosphate post-liquid was then subjected to activated carbon decolorization, adsorption with polystyrene skeleton aminophosphonic acid resin (flow rate 1.5 BV / h), and vacuum evaporation crystallization at 60℃ to obtain lithium carbonate.

[0034] The final lithium separation rate, phosphorus and iron recovery rate, and lithium carbonate purity are shown in Table 2, and the main indicators of iron phosphate are shown in Table 3.

[0035] Example 5 (1) Weigh 1 kg of lithium iron phosphate battery powder and calculate based on the content of metals such as lithium, iron, copper, aluminum and titanium. The volume ratio of hydrochloric acid to phosphoric acid is 4:1, with an acid excess of 40%. Add water to make a slurry and stir, and control the solid content at 20%. Use ultrasonic assistance (300W) and gradient temperature control (20℃→50℃→80℃, keep warm for 1 hour in each stage). The total acid leaching time is 5 hours. After leaching, filter to obtain the acid leaching solution. (2) Sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) are compounded at a certain mass ratio of 3:1, with an excess of 30% of the compound surfactant (based on the total concentration of aluminum and copper ions in the acid leaching solution). Air is introduced during flotation (flow rate 0.8 L / min) to enhance the separation efficiency. (3) Add acid to adjust the pH of the acid leaching solution to <1, use chlorine dioxide solution with a concentration of 800 mg / L as the main oxidant, add lithium ferrate and introduce nano ZnO photocatalyst (particle size 200 nm), the molar ratio of lithium ferrate to chlorine dioxide is 1:6, chlorine dioxide is in excess by 20%, and irradiate with ultraviolet light (wavelength 365 nm) for 1 h; then adjust the pH of the acid leaching solution to 2.2 to achieve high-purity iron precipitation; (4) The phosphate precipitate and the phosphate effluent were obtained by filtration. The phosphate precipitate was washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain phosphate. The phosphate effluent was then subjected to activated carbon decolorization, adsorption with polyacrylic acid skeleton aminophosphonic acid resin (flow rate 1.5 BV / h) and vacuum evaporation at 70℃ to obtain lithium carbonate.

[0036] The final lithium separation rate, phosphorus and iron recovery rate, and lithium carbonate purity are shown in Table 2, and the main indicators of iron phosphate are shown in Table 3.

[0037] Example 6 (Counterexample) (1) Weigh 1 kg of lithium iron phosphate battery powder and calculate the content of lithium, iron, copper, aluminum, titanium and other metals. The volume ratio of hydrochloric acid to phosphoric acid is 4:1, with an acid excess of 30%. Add water to make a slurry and stir, and control the solid content at 20%. Use ultrasonic assistance (300W) and gradient temperature control (20℃→50℃→80℃, keep warm for 1 hour in each stage). The total acid leaching time is 3 hours. After leaching, filter to obtain the acid leaching solution.

[0038] (2) Sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) are compounded at a certain mass ratio of 3:1, with the composite surfactant in excess by 20% (based on the total concentration of aluminum and copper ions in the acid leaching solution). Air is introduced during flotation (flow rate 0.8L / min) to enhance the separation efficiency.

[0039] (3) Add acid to adjust the pH of the acid leaching solution to <1, use chlorine dioxide solution with a concentration of 800mg / L as the main oxidant, add lithium ferrate, the molar ratio of lithium ferrate to chlorine dioxide is 1:6, chlorine dioxide is in excess by 20%, and irradiate with ultraviolet light (wavelength 365nm) for 1h; then adjust the pH of the acid leaching solution to 2.5 to achieve high-purity iron precipitation.

[0040] (4) The phosphate precipitate and the phosphate effluent were obtained by filtration. The phosphate precipitate was washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain phosphate. The phosphate effluent was then subjected to activated carbon decolorization, polystyrene skeleton aminophosphonic acid resin adsorption (flow rate 1.5 BV / h), and vacuum evaporation crystallization at 70℃ to obtain lithium carbonate.

[0041] The final lithium separation rate, phosphorus and iron recovery rate, and lithium carbonate purity are shown in Table 2, and the main indicators of iron phosphate are shown in Table 3.

[0042] Example 7 (1) Weigh 1 kg of lithium iron phosphate battery powder and calculate the content of lithium, iron, copper, aluminum, titanium and other metals. The volume ratio of hydrochloric acid to phosphoric acid is 4:1, with an acid excess of 40%. Add water to make a slurry and stir, and control the solid content at 20%. Use ultrasonic assistance (300W) and gradient temperature control (20℃→50℃→80℃, keep warm for 1 hour in each stage). The total acid leaching time is 5 hours. After leaching, filter to obtain the acid leaching solution. (2) Sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) are compounded at a certain mass ratio of 3:1, with an excess of 30% of the compound surfactant (based on the total concentration of aluminum and copper ions in the acid leaching solution). Air is introduced during flotation (flow rate 0.8 L / min) to enhance the separation efficiency. (3) Add acid to adjust the pH of the acid leaching solution to <1, use chlorine dioxide solution with a concentration of 800 mg / L as the main oxidant, add lithium ferrate and introduce nano ZnO photocatalyst (particle size 200 nm), the molar ratio of lithium ferrate to chlorine dioxide is 1:6, chlorine dioxide is in excess by 20%, and irradiate with ultraviolet light (wavelength 365 nm) for 1 h; then adjust the pH of the acid leaching solution to 2.2 to achieve high-purity iron precipitation; (4) The phosphate precipitate and the phosphate effluent were obtained by filtration. The phosphate precipitate was washed with a gradient of deionized water-ethanol mixture (volume ratio 1:1) to obtain phosphate. The phosphate effluent was decolorized by activated carbon and then evaporated and crystallized under vacuum at 70°C to obtain lithium carbonate.

[0043] The final lithium separation rate, phosphorus and iron recovery rate, and lithium carbonate purity are shown in Table 2, and the main indicators of iron phosphate are shown in Table 3.

[0044] Table 2

[0045] Table 3

Claims

1. A method for obtaining iron phosphate and lithium-rich solution from lithium iron phosphate battery powder, characterized in that, Includes the following steps: (1) The lithium iron phosphate battery powder is filtered after acid leaching to obtain the acid leaching solution; (2) Remove copper and aluminum from the acid leaching solution by ion flotation; (3) Add chlorine dioxide solution and ferrate, nano ZnO photocatalyst to the acid leaching solution obtained in step (2), and oxidize it with ultraviolet light to adjust the pH and precipitate iron. (4) The iron phosphate precipitate and the iron phosphate post-liquid are obtained by filtration and separation. The iron phosphate precipitate is washed to obtain iron phosphate. The iron phosphate post-liquid is decolorized and impurities are removed to obtain battery-grade lithium carbonate.

2. The method according to claim 1, characterized in that: The acid used in step (1) during the acid leaching process includes one or more combinations of sulfuric acid, hydrochloric acid, and nitric acid. The acid leaching temperature is 10~90℃ and the acid leaching time is 0.5~6h.

3. The method according to claim 1, characterized in that: The surfactant used in the ion flotation process described in step (2) is a compound of sodium lauroyl-N-methylaminoacetate (LS) and phosphate ester-based gemini surfactant (P-Gemini) in a mass ratio of 2:1 to 6:

1. The compound surfactant is in excess of 0% to 50%, and air is introduced during flotation.

4. The method according to claim 3, characterized in that: The mass ratio of lauroyl-N-methylaminoacetic acid sodium LS to phosphate ester-based gemini surfactant P-Gemini is 3:1; the composite surfactant is in excess by 10-30%.

5. The method according to claim 1, characterized in that: After adjusting the pH of the obtained acid leaching solution to <1, add 500~1500mg / L of chlorine dioxide solution; The molar ratio of ferrate to chlorine dioxide is 1:10 to 1:

2.

6. The method according to claim 5, characterized in that: The ferrate is one or more of potassium ferrate, sodium ferrate, ammonium ferrate, and lithium ferrate.

7. The method according to claim 6, characterized in that: The nano-ZnO photocatalyst has a particle size of 100~200nm, and its dosage is 0.2%~0.4% of the mass of the acid leaching solution. The ultraviolet light irradiation time is 0.5~2h.

8. The method according to claim 1, characterized in that: In step (3), the phosphorus-iron liquid is decolorized by activated carbon, impurities are removed by adsorption with aminophosphonic acid chelating resin, and then vacuum evaporated and crystallized at 40~80℃ to obtain battery-grade lithium carbonate.

9. The method according to claim 8, characterized in that: The aminophosphonic acid chelating resin is one of polystyrene skeleton aminophosphonic acid resin, polyacrylic acid skeleton aminophosphonic acid resin, and phenolic resin skeleton aminophosphonic acid resin.

10. The method according to claim 9, characterized in that: The chelating resin adsorption flow rate is 1-2 BV / h, and the concentration of calcium and magnesium ions in the solution after adsorption is <0.1 ppm.

Images