Aluminum ion selective extraction agent and preparation method thereof, and recovery method of waste lithium iron phosphate battery

Abstract

The invention discloses a novel aluminum ion selective extraction agent and a method for recycling waste lithium iron phosphate batteries, by designing a brand new structure, the specific extraction depth of the novel aluminum ion selective extraction agent to aluminum ions is high, the aluminum ions in a solution can be reduced to 10 ppm or below, the structure of the novel aluminum ion selective extraction agent is # imgabs0 #, and R is a C1-C10 saturated carbon chain or a C2-C10 unsaturated carbon chain. According to the method, fully discharged scrapped lithium iron phosphate batteries are sequentially shredded by using a double-shaft shearing type crusher under the protection of an inert gas atmosphere; the solvent in the electrolyte is evaporated while the binder is subjected to high-temperature anaerobic cracking; separating the battery shell, the copper foil and the aluminum foil from the lithium iron phosphate battery powder by using a sieve; selectively leaching lithium from the lithium iron phosphate battery powder by using equivalent dilute sulphuric acid; adding dilute sulphuric acid into the lithium-extracted iron phosphate to dissolve the lithium-extracted iron phosphate, then removing impurity aluminum ions in the solution by using the extracting agent, and re-synthesizing the battery-grade iron phosphate.

Description

Technical Field

[0001] The present invention relates to an aluminum ion selective extractant, a preparation method thereof, and an application thereof in the recycling of waste lithium iron phosphate batteries. Background Art

[0002] In the industry, the problems of solvent residue in the recycled battery powder and excessive impurities such as copper and aluminum have not been solved in the recycling of waste lithium iron phosphate batteries, so that the recycling of waste lithium iron phosphate batteries has not been widely applied and promoted like waste ternary batteries. At present, the existing recycling processes for waste lithium iron phosphate batteries are limited to the recycling of lithium, and the main components of iron and phosphorus elements have not been resourcefully utilized. The main reason is that the iron and phosphorus elements cannot be properly separated from the impurity aluminum, and the prepared iron phosphate is unqualified; although there are many patents such as CN112331949B, CN112093785B and CN109626350B etc. which mention the preparation of battery-grade phosphoric acid from iron and phosphorus elements, they turn a blind eye to the problem of unqualified iron phosphate products caused by impurity elements such as aluminum. CN 114852983 A does have a certain effect in removing aluminum with sodium hydroxide, but the depth is not enough and the aluminum content is still excessive. CN115304042A can indeed obtain a relatively ideal aluminum removal effect on the battery pole piece powder with low aluminum content using citric acid and chloride, but the pole piece powder only accounts for a very small proportion in the battery recycling, and it is difficult to ensure that the aluminum content of the battery powder is lower than 0.2% in actual production; moreover, this scheme introduces chlorine, which will lead to unqualified iron phosphate products, and the water treatment problem brought by citric acid is also quite intractable.

[0003] Therefore, there is an urgent need to develop a more reasonable and effective method for the post-treatment of waste lithium iron phosphate batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide an aluminum ion selective extractant and a preparation method thereof, which have good adsorption selectivity for aluminum ions.

[0005] Another purpose of the present invention is to provide a method for recycling waste lithium iron phosphate batteries, which simplifies the process of recycling stainless steel shells (plastic shells), metallic copper, metallic aluminum, diaphragms, iron phosphate and lithium carbonate from waste lithium iron phosphate batteries, and improves the resource utilization rate of lithium, phosphorus and iron.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] An aluminum ion selective extractant has the following structural formula:

[0008]

[0009] Wherein, R is a saturated carbon chain of C1-C10 or an unsaturated carbon chain of C2-C10 of C1-C10.

[0010] The preparation method of the aluminum ion selective extractant of the present invention comprises the following steps:

[0011] (1) Phosphorus trichloride reacts with 2-methylaminohexanol to form bis(2-methylaminohexyl) phosphite;

[0012] (2) Bis(2-methylaminohexyl) phosphite condenses with 2-R-hexylmethyl chloroalkane in the presence of sodium ethoxide to obtain bis(2-R-hexylmethyl) 2-methylaminohexylphosphonate;

[0013] (3) Bis(2-R-hexylmethyl) 2-methylaminohexylphosphonate is preferably hydrolyzed with ethanolamine to form 2-(methylaminohexyl)-2-R-hexylmethylphosphonic acid monoester.

[0014] Preferably, in the step (1), toluene, DNF or excessive 2-methylaminohexanol is used as the solvent; more preferably, excessive 2-methylaminohexanol is used as the solvent; the molar ratio of phosphorus trichloride to 2-methylaminohexanol is 1:1 to 5. The reaction does not require a catalyst, the reaction temperature is 0 to 100 °C, and the reaction is carried out at normal pressure for 2 to 4 hours.

[0015]

[0016] Preferably, in the step 2), ethanol is used as the solvent; the molar ratio of bis(2-methylaminohexyl) phosphite, 2-R-hexylmethyl chloroalkane, sodium ethoxide to ethanol is 1:1 to 1.2:0.01 to 0.02:500 to 1500. Sodium ethoxide is used as the catalyst, the reaction temperature is 70 to 120 °C, and the reaction is carried out at normal pressure for 1 to 5 hours.

[0017]

[0018] Preferably, in the step (3), bis(2-R-hexylmethyl) 2-methylaminohexylphosphonate is hydrolyzed with 8 to 20 times the weight of deionized water, ethanolamine is used as the catalyst, the molar ratio of ethanolamine to bis(2-R-hexylmethyl) 2-methylaminohexylphosphonate is 1:10 to 100, and the temperature is controlled at 50 to 110 °C; more preferably, the temperature is controlled at 90 to 110 °C, and the reaction is carried out at normal pressure for 1 to 2 hours.

[0019]

[0020] A method for recycling waste lithium iron phosphate batteries comprises the following steps:

[0021] 1) Fully discharge the scrapped lithium iron phosphate battery;

[0022] 2) The battery in step 1) is shredded under the protection of an inert gas atmosphere. Preferably, it is shredded using a double-shaft shear crusher to obtain battery fragments;

[0023] 3) While pyrolyzing the binder of the battery fragments in step 2) at high temperature under anaerobic conditions, the solvent in the electrolyte is evaporated; preferably, the evaporated solvent accounts for about 70% - 90% of the solvent in the battery and needs to be condensed and recovered;

[0024] 4) After high-temperature anaerobic pyrolysis, the battery powder falls off the copper foil and aluminum foil of the electrode. The battery shell, copper foil, and aluminum foil are separated from the lithium iron phosphate battery powder using a sieve; the battery shell, copper foil, and aluminum foil are further separated by gravity separation and color sorting;

[0025] 5) The lithium iron phosphate battery powder obtained in step 4) is treated with equivalent dilute sulfuric acid, and the concentration of the dilute sulfuric acid is 10% - 15%, to selectively leach lithium and aluminum; the slurry is filtered, and the filtrate is a lithium sulfate solution; preferably, based on the lithium content in the lithium iron phosphate powder, 0.5 - 0.8 mol of sulfuric acid is added per 1 mol of lithium;

[0026] 6) After adjusting the pH = 10 - 11 to remove impurities from the lithium sulfate solution, sodium carbonate or potassium carbonate is added to precipitate lithium carbonate and then filtered; preferably, based on the lithium content in the solution, 0.5 - 0.6 mol of sodium carbonate / potassium is added per 1 mol of lithium;

[0027] 7) The filter cake obtained in step 6) is slurried with an appropriate amount of dilute sulfuric acid water to dissolve the iron and phosphorus elements in the filter cake; the filtrate is obtained by filtration; preferably, based on the iron content in the filter cake, 1.5 - 2.5 mol of sulfuric acid is added per 1 mol of iron, and the concentration of the dilute sulfuric acid is 10% - 15%;

[0028] 8) The extractant described in claim 1 is added to the filtrate obtained in step 7), and the iron and phosphorus element content and concentration are adjusted;

[0029] 9) Ammonia water or liquid caustic soda is added dropwise to the solution obtained in step 8), and the pH value is controlled to stably precipitate iron phosphate;

[0030] 10) The reaction system in step 9) is heated to age and kept warm; after cooling, it is filtered, and the filter cake is washed and dried to obtain battery-grade iron phosphate.

[0031] Preferably, for step 1), the method of discharging the scrapped lithium iron phosphate battery can be a discharger or brine discharge; more preferably, the battery discharge method is using a discharger.

[0032] Preferably, the inert gas used in step 2) is one or several of carbon dioxide, nitrogen, argon, and helium; more preferably, the inert gas is nitrogen.

[0033] Preferably, the cracking temperature in step 3) is 300-600°C; more preferably, the cracking temperature is 400-500°C.

[0034] Preferably, the sieve used in step 4) is one or a combination of a linear vibrating sieve, a rotary drum sieve, a circular vibrating sieve, and an ultrasonic vibrating sieve; more preferably, it is a combination of a linear vibrating sieve and a circular vibrating sieve.

[0035] Preferably, the ratio of iron element to phosphorus element in the filtrate in step 8) is 0.98-1.03; more preferably, it is 1-1.02. The concentration is 0.1 mol / L-0.12 mol / L; and / or, the dosage of the extractant is 1-10% of the weight of iron phosphate.

[0036] Preferably, the pH in step 9) is controlled at 1.8-2.5; more preferably, it is 1.8-2.0.

[0037] Preferably, the temperature in step 10) is controlled at 85-99°C; more preferably, it is 90-95°C. The heat preservation time is 2-10 hours.

[0038] The beneficial effects of the present invention are as follows: A method for recycling waste lithium iron phosphate battery powder to prepare battery-grade iron phosphate provided by the present invention selectively removes aluminum ions in the iron-phosphorus dissolution solution by preparing a new extractant, ensuring that the aluminum element content in the product iron phosphate is within the qualified range. And this method has simple reaction steps and is suitable for large-scale industrial production. A new extractant (2-(methylaminohexyl)-2-R-hexyl methylphosphonic acid monoester) structure and its synthesis method are provided. This extractant has particularly high extraction selectivity for aluminum ions under appropriate conditions and has no extraction effect on divalent and trivalent iron ions. Applying it to the recycling of waste lithium iron phosphate batteries solves the problems of high impurity aluminum content in the lithium iron phosphate battery powder and the inability to recycle iron and phosphorus elements. The technological process is short, simple and easy to operate, the reaction conditions are mild, and the recovery rates of lithium, phosphorus, and iron elements are improved.

[0039] Description of the Drawings: Figure 1 It is the 1H NMR spectrum of the extractant prepared in Example 1.

[0040] Figure 2 It is the 1H NMR spectrum of the extractant prepared in Example 2.

[0041] Figure 3 It is the 1H NMR spectrum of the extractant prepared in Example 3. Detailed Description of the Invention

[0042] The present invention will be further described below with specific examples:

[0043] NMR analysis: Bruker 400

[0044] Example 1:

[0045] Into a three-necked flask containing a toluene solution of 3.5 mol of 2-methylaminohexanol, 1 mol of phosphorus trichloride was added dropwise. Stirring was started, and the reaction temperature was controlled below 5 °C in an ice bath. After the addition was complete, the ice bath was removed and a water bath was used. When the system temperature reached 10 °C, HCl gas evolved. At this time, the vacuum device was turned on to extract the HCl evolved from the reaction. The temperature was controlled not to exceed 25 °C and maintained for 0.5 h. When the evolution of HCl gas was not obvious, the temperature was slowly raised to 60 °C and maintained for 4 h.

[0046] It was cooled to room temperature to obtain bis(methylaminohexyl) phosphite; 1 mol of (2-methyl-hexylmethyl) chloroalkane was added to 150 mL of an ethanol solution of 0.5% sodium ethoxide with stirring and condensed at 80 °C for 2 h to obtain bis(2-methyl-hexylmethyl) 2-methylaminohexylphosphonate.

[0047] Then, 0.1 mol of ethanolamine was used for hydrolysis in 6300 g of deionized water at 110 °C for 1 h to form 2-(methylaminohexyl)-2-methyl-hexylmethylphosphonic acid monoester.

[0048] Example 2

[0049] Into a three-necked flask containing a toluene solution of 4 mol of 2-methylaminohexanol, 1 mol of phosphorus trichloride was added dropwise. Stirring was started, and the reaction temperature was controlled below 1 °C in an ice bath. After the addition was complete, the ice bath was removed and a water bath was used. When the system temperature reached 50 °C, HCl gas evolved. At this time, the vacuum device was turned on to extract the HCl evolved from the reaction. The temperature was controlled not to exceed 25 °C and maintained for 0.5 h. When the evolution of HCl gas was not obvious, the temperature was slowly raised to 100 °C and maintained for 2 h.

[0050] It was cooled to room temperature to obtain bis(methylaminohexyl) phosphite; 1 mol of (2-ethyl-hexylmethyl) chloroalkane was added to 800 mL of an ethanol solution of 0.1% sodium ethoxide with stirring and condensed at 120 °C for 1 h to obtain bis(2-ethyl-hexylmethyl) 2-methylaminohexylphosphonate.

[0051] Then, 0.07 mol of ethanolamine was used for hydrolysis in 3200 g of deionized water at 90 °C for 1 h to form 2-(methylaminohexyl)-2-ethyl-hexylmethylphosphonic acid monoester.

[0052] Example 3

[0053] A toluene solution of 5 mol of 2-methylaminohexanol was added dropwise to a three-necked flask containing 1 mol of phosphorus trichloride. Stirring was started, and the reaction temperature was controlled below 3 °C in an ice bath. After the addition was complete, the ice bath was removed and a water bath was used to raise the system temperature to 50 °C, at which point HCl gas evolved. At this time, the vacuum device was turned on to extract the HCl released during the reaction, and the temperature was controlled not to exceed 25 °C and maintained for 0.5 h. When the evolution of HCl gas became less obvious, the temperature was slowly raised to 80 °C and maintained for 2 h.

[0054] It was cooled to room temperature to obtain bis(methylaminohexyl) phosphite; 1 mol of (2-vinyl-hexylmethyl) chloroalkane was added to 500 mL of an ethanol solution of 0.18% sodium ethoxide with stirring, and the condensation reaction was carried out at 90 °C for 5 h to obtain bis(2-vinyl-hexylmethyl) 2-methylaminohexylphosphonate.

[0055] Then, 0.01 mol of ethanolamine was used for hydrolysis in 4000 g of deionized water at 60 °C for 2 h to generate 2-(methylaminohexyl)-2-vinyl-hexylmethylphosphonic acid monoester.

[0056] Example 4:

[0057] The scrapped cylindrical lithium iron phosphate battery was soaked in brine for 3 h for full discharge, and the voltage of each battery was detected to be ≤0.5 V. The battery was taken out and drained; the discharged ICR18650 battery was conveyed by a belt to a double-shaft shear crusher with nitrogen protection for shredding into fragments with a side length of about 2 cm similar to a square; the battery fragments entered a high-temperature anaerobic cracking furnace through a conveyor belt. The high-temperature anaerobic cracking furnace had multiple temperature zones, with the high-temperature section set at 500 °C and the cold section set at 60 °C. The whole material stayed in the furnace for 4 h; the evaporated solvent accounted for about 90% of the solvent in the battery and needed to be condensed and recovered; the nitrogen was returned to the furnace as a protective gas; the material leaving the high-temperature anaerobic cracking furnace directly entered a linear vibrating screen for screening. The material on the screen of the linear vibrating screen entered a rotary screen for re-screening once. The material under the rotary screen was combined with the material under the linear vibrating screen for treatment. After the material on the rotary screen entered an air separator to separate the diaphragm, it entered a magnetic separator to separate the battery shell. The remaining material entered a crusher for crushing and was screened again with a 200-mesh rotary vibrating screen. The material under the rotary vibrating screen was incorporated into the material under the linear vibrating screen for combined treatment. The material on the rotary vibrating screen was separated by a combination of a gravity separator and a color sorter to obtain aluminum foil powder and copper foil powder, which were respectively collected in corresponding bins.

[0058] Take 100 g of lithium iron phosphate battery powder (the effective content of lithium iron phosphate accounts for about 65%) in a bunker and place it in a 500-ml beaker. Add 300 ml of 10% dilute sulfuric acid and stir for 2 hours; filter, adjust the pH of the filtrate to 10 with lime milk, filter again, add 2 g of sodium carbonate to the filtrate and stir for 1 hour to produce a small amount of precipitate. After the third filtration, add 40 g of sodium carbonate to the filtrate, stir and keep it at -5°C for 2 hours, filter and wash the filter cake with deionized water at -5°C. The obtained white filter cake is dried to obtain industrial lithium carbonate. Pulp the filter cake after lithium extraction with 450 g of water, add 1000 g of 10% sulfuric acid dropwise to control the pH value > 0.8 to dissolve the filter cake. Filter the dissolution system to remove a small amount of insoluble substances. Add 50 ml of sulfonated kerosene containing 10% 2-(methylaminohexyl)-2-n-heptyl-hexylmethylphosphonic acid monoester to the filtrate and stir well. After standing and separating the liquid, detect and adjust the iron content in the filtrate: 6%, phosphorus content: 3.3%. At room temperature, add ammonia water dropwise to control the pH = 1.8 to stably precipitate iron phosphate; after adding ammonia water, heat the reaction system to 90°C for aging and keep it for 2 hours. After the reaction system cools down, filter, wash and dry the filter cake to obtain battery-grade iron phosphate.

[0059] Analysis of the aluminum content in the sulfuric acid-dissolved iron and phosphorus solution extracted in Example 4 shows that: Al%: 0.0001% (ICP analysis of aluminum and other impurity contents is performed using Agilent 5900. The main content of phosphorus is titrated with quinoline molybdate citrate, and the iron content is titrated with potassium dichromate.)

[0060] Analysis of the impurity content of the industrial anhydrous iron phosphate prepared in Example 4 shows that: Fe%: 36.1%, P%: 20.8%, Ca%: 0.002%, Mg%: 0.03%, K%: 0.015%, Cu%: 0.001%, Zn%: 0.001%, Mn%: 0.05%, Al%: 0.0005%, Ti%: 0.02%, magnetic substance%: 0.00001%, moisture%: 0.18%, tapped density: 0.6, BET: 8.5 m 2 / g.

[0061] Example 5:

[0062] The steps of Example 5 are basically the same as those of Example 4, except that: After taking 5000 grams of lithium iron phosphate battery powder from the battery powder bin recovered in Example 4 and selectively extracting lithium, 20000 ml of 15% dilute sulfuric acid is added to the filter cake, and it is slurried and stirred for 2 hours; After filtration, 1500 ml of sulfonated kerosene containing 20% 2-(ethylaminohexyl)-2-n-heptyl-hexylmethylphosphonic acid monoester is added to the filtrate and stirred well. After standing for liquid separation by layering, the iron content in the filtrate is detected and adjusted: 6.12%, phosphorus content: 3.4%. At 25 °C, ammonia water is added dropwise, and the pH is controlled at 2.1 to stably precipitate iron phosphate; After adding ammonia water, the reaction system is heated to 96 °C for aging and kept warm for 6 hours. After the reaction system is cooled, it is filtered, and the filter cake is washed and dried to obtain battery-grade iron phosphate.

[0063] Analysis of the impurity content of the industrial anhydrous iron phosphate prepared in Example 5 shows that: Fe%: 35.8%, P%: 20.8%, Ca%: 0.002%, Mg%: 0.03%, K%: 0.015%, Cu%: 0.0009%, Zn%: 0.0015%, Mn%: 0.05%, Al%: 0.005%, Ti%: 0.03%, magnetic substance%: 0.00002%, moisture%: 0.22%, tapped density: 0.9, BET: 8.5m 2 / g.

[0064] Example 6:

[0065] The scrapped soft-pack lithium iron phosphate battery is fully discharged with a discharger for 12 hours, and the voltage of each battery is detected to be ≤0.5V, and the battery is taken out and drained of water; The discharged soft-pack battery is conveyed by a belt to a double-shaft shearing crusher shredded under nitrogen protection and shredded into fragments with a side length of about 2 cm similar to a square; The battery fragments enter a high-temperature anaerobic cracking furnace through a conveyor belt. The high-temperature anaerobic cracking furnace has multiple temperature zones. The high-temperature section is set at 300 °C, and the cold section is set at 60 °C. The whole material stays in the furnace for 4 hours; The solvent evaporated accounts for about 90% of the solvent in the battery and needs to be condensed and recovered; Nitrogen is used as the protective gas; The material leaving the high-temperature anaerobic cracking furnace directly enters a linear vibrating screen for screening. The material on the screen of the linear vibrating screen enters a drum screen for re-screening once. The material under the drum screen is combined with the material under the linear vibrating screen for combined treatment. After the material on the drum screen is separated from the diaphragm by an air separator, the remaining material is pulverized by a pulverizer and then screened again by a 200-mesh rotary vibrating screen. The material under the rotary vibrating screen is incorporated into the material combined with the material under the linear vibrating screen for combined treatment. The material on the rotary vibrating screen is separated into steel shell powder, aluminum foil powder, and copper foil powder through a combination of a gravity separator and a color sorter and collected in the corresponding bins respectively.

[0066] Take 100 kg of lithium iron phosphate battery powder in a bunker and put it into a 500 L reactor. Add 200 L of 16% dilute sulfuric acid and stir for 2 hours for pulping; filter, adjust the pH of the filtrate to 10.5 with lime milk, filter again, add 2 kg of sodium carbonate to the filtrate and stir for 1 hour to produce a small amount of precipitate. After the third filtration, add 40 kg of sodium carbonate to the filtrate, stir and keep it at -5°C for 2 hours, filter and wash the filter cake with deionized water at -5°C. The obtained white filter cake is dried to obtain industrial lithium carbonate. Add 550 kg of 15% sulfuric acid to the filter cake after lithium extraction to control the pH value > 0.8 to dissolve the filter cake. Filter the dissolution system to remove a small amount of insoluble substances. Add 50 L of sulfonated kerosene containing 20% 2-(vinylaminohexyl)-2-n-heptyl-hexylmethylphosphonic acid monoester to the filtrate and stir well. After standing, separating the liquid by layering, detect and adjust the iron content in the filtrate: 5.8%, phosphorus content: 3.15%. Add ammonia water dropwise at 60°C to control the pH = 1.9 to stably precipitate iron phosphate; after adding ammonia water, heat the reaction system to 98°C for aging and keep it warm for 9 hours. After the reaction system cools, filter, wash and dry the filter cake to obtain battery-grade iron phosphate.

[0067] Analysis of the aluminum content in the sulfuric acid-dissolved iron and phosphorus solution extracted in Example 6 shows that: Al%: 0.0002%

[0068] Analysis of the impurity content of the industrial anhydrous iron phosphate prepared in Example 6 shows that: Fe%: 35.7%, P%: 20.9%, Ca%: 0.002%, Mg%: 0.02%, K%: 0.015%, Cu%: 0.002%, Zn%: 0.001%, Mn%: 0.03%, Al%: 0.005%, Ti%: 0.03%, magnetic substance%: 0.00003%, moisture%: 0.32%, tapped density: 0.7, BET: 6.5m 2 / g.

[0069] Analysis of the impurity content of the industrial lithium carbonate prepared in Example 6 shows that:

[0070] Na2O%: 0.2, Fe2O3%: 0.004, CaO%: 0.04%, Cl%: 0.001%, SO4 2- %: 0.3%, acid-insoluble substances 0.004%.

[0071] Example 7:

[0072] The steps of Example 7 are basically the same as those of Example 6, with the differences being as follows: 50 mL of sulfonated kerosene containing 10% 2-(methylaminohexyl)-2-ethyl-hexyl methylphosphonic acid monoester was added to the filtrate and stirred well. After standing for layering and liquid separation, the iron content in the filtrate was detected and adjusted to 6.1%, and the phosphorus content was 3.4%. Ammonia water was added dropwise at 45 °C, and the pH was controlled at 1.8 to stably precipitate iron phosphate. After adding ammonia water, the reaction system was heated to 95 °C for aging and kept warm for 2 hours. After the reaction system was cooled, it was filtered, and the filter cake was washed and dried to obtain battery-grade iron phosphate.

[0073] Analysis of the aluminum content in the iron and phosphorus solution dissolved by sulfuric acid extracted in Example 7 shows that: Al%: 0.0005%

[0074] Analysis of the impurity content of the battery-grade iron phosphate prepared in Example 7 shows that:

[0075] Fe%: 35.7%, P%: 21.0%, Ca%: 0.005%, Mg%: 0.02%, K%: 0.005%, Cu%: 0.0001%, Zn%: 0.001%, Mn%: 0.003%, Al%: 0.005%, Ti%: 0.002%, magnetic substances%: 0.00002%, moisture%: 0.4%, tapped density: 0.7, BET: 8.5 m 2 / g.

[0076] Example 8:

[0077] The steps of Example 8 are basically the same as those of Example 7, with the differences being as follows: 50 mL of sulfonated kerosene containing 10% 2-(methylaminohexyl)-2-methyl-hexyl methylphosphonic acid monoester was added to the filtrate and stirred well. After standing for layering and liquid separation, the iron content in the filtrate was detected and adjusted to 6.05%, and the phosphorus content was 3.35%. Ammonia water was added dropwise at 25 °C, and the pH was controlled at 2.0 to stably precipitate iron phosphate. After adding ammonia water, the reaction system was heated to 85 °C for aging and kept warm for 10 hours. After the reaction system was cooled, it was filtered, and the filter cake was washed and dried to obtain battery-grade iron phosphate.

[0078] Analysis of the aluminum content in the iron and phosphorus solution dissolved by sulfuric acid extracted in Example 8 shows that: Al%: 0.0005%

[0079] Analysis of the impurity content of the battery-grade iron phosphate prepared in Example 8 shows that:

[0080] Fe%: 35.7%, P%: 21.2%, Ca%: 0.003%, Mg%: 0.03%, K%: 0.006%, Cu%: 0.0002%, Zn%: 0.0001%, Mn%: 0.003%, Al%: 0.005%, Ti%: 0.008%, Magnetic substance%: 0.00003%, Moisture%: 0.46%, Tap density: 0.79, BET: 7.8m 2 / g.

[0081] Comparative Example 1:

[0082] The steps of Comparative Example 1 are basically the same as those of Example 8, except that: the filtrate is not treated with an extractant to remove aluminum, the iron content in the filtrate is detected and adjusted: 6.1%, the phosphorus content: 3.32%, ammonia water is added dropwise at 25 °C, and the pH is controlled at 1.9 to stably precipitate iron phosphate; after adding ammonia water, the reaction system is heated to 85 °C for aging and kept warm for 10 hours, and after the reaction system is cooled, it is filtered, and the filter cake is washed and dried to obtain iron phosphate.

[0083] Analysis of the aluminum content in the iron-phosphorus solution dissolved by sulfuric acid extracted in Comparative Example 1 shows that: Al%: 0.06%

[0084] Analysis of the impurity content of the battery-grade iron phosphate prepared in Comparative Example 1 shows that:

[0085] Fe%: 35.7%, P%: 21.1%, Ca%: 0.003%, Mg%: 0.03%, K%: 0.005%, Cu%: 0.0001%, Zn%: 0.0002%, Mn%: 0.003%, Al%: 0.32%, Ti%: 0.008%, Magnetic substance%: 0.000013%, Moisture%: 0.38%, Tap density: 0.9, BET: 8.0m 2 / g.

[0086] In summary, the present invention provides a brand-new extractant structure design and a method for recycling stainless steel shells (plastic shells), metallic copper, metallic aluminum, diaphragms, iron phosphate, and lithium carbonate from waste lithium iron phosphate batteries, improving the treatment efficiency of waste lithium iron phosphate batteries, shortening the recycling process of waste lithium iron phosphate batteries (requiring low pretreatment), reducing the content of impurity aluminum in the powder of lithium iron phosphate batteries, and efficiently and selectively removing the impurity aluminum dissolved in the iron-phosphorus solution, and finally preparing qualified battery-grade iron phosphate. It realizes the resource recycling of iron and phosphorus elements, solves the situation that iron and phosphorus elements are solid wastes after lithium is recycled in the current process. It improves the utilization value and economic benefits of waste materials in waste lithium iron phosphate.

[0087] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0088] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An aluminum ion selective extractant, characterized in that its structural formula is: wherein, R is a saturated carbon chain with 1 to 10 carbon atoms or an unsaturated carbon chain with 2 to 10 carbon atoms.

2. The preparation method of the aluminum ion selective extractant according to claim 1, characterized in that, It includes the following steps: (1) Phosphorus trichloride reacts with 2-methylaminohexanol to form bis(2-methylaminohexyl) phosphite; (2) In the presence of sodium ethoxide, bis(2-methylaminohexyl) phosphite reacts with 1-chloro(2-R-hexylmethyl) alkane to obtain bis(2-R-hexylmethyl) 2-methylaminohexyl phosphonate; (3) Bis(2-R-hexylmethyl) 2-methylaminohexyl phosphonate is hydrolyzed to form 2-(methylaminohexyl)-2-R-hexylmethyl phosphonic acid monoester.

3. The preparation method according to claim 2, wherein In step (1), the molar ratio of phosphorus trichloride to 2-methylaminohexanol is 1:1 to 5; and / or, the reaction temperature is 0 to 100 °C, and the reaction time is 2 to 4 hours.

4. The preparation method according to claim 2 or 3, characterized in that, In step (2), the molar ratio of bis(2-methylaminohexyl) phosphite, 1-chloro(2-R-hexylmethyl) alkane, and sodium ethoxide is 1:1 to 1.2:0.01 to 0.02; and / or, the reaction temperature is 70 to 120 °C, and the reaction is carried out for 1 to 5 hours.

5. The preparation method according to any one of claims 2-4, characterized in that, Step (3) uses ethanolamine as a catalyst, and the molar ratio of ethanolamine to bis(2-R-hexylmethyl) 2-methylaminohexyl phosphonate is: 1:10 to 100; and / or, the reaction temperature is 50 to 110 °C; the reaction time is 1 to 2 hours.

6. A recycling method for waste lithium iron phosphate batteries, characterized in that, It includes the following steps: 1) Fully discharge the scrapped lithium iron phosphate battery; 2) Tear the battery obtained in step 1) under the protection of an inert gas atmosphere to obtain battery fragments, preferably tear it with a double-shaft shear crusher; 3) Pyrolyze the binder of the battery fragments obtained in step 2) under high temperature and anaerobic conditions while evaporating the solvent in the electrolyte; preferably, the evaporated solvent accounts for 70 to 90% of the solvent in the battery and needs to be condensed and recovered; 4) After high temperature and anaerobic pyrolysis, the battery powder falls off from the copper foil and aluminum foil of the electrode, and a sieve is used to separate the battery shell, copper foil, aluminum foil from the lithium iron phosphate battery powder; the battery shell, copper foil, and aluminum foil are further separated by gravity separation and color sorting; 5) Selectively leach lithium and aluminum from the lithium iron phosphate battery powder obtained in step 4) with dilute sulfuric acid; filter the slurry, and the filtrate is a lithium sulfate solution; 6) After adjusting the pH to remove impurities from the lithium sulfate solution, add sodium carbonate or potassium carbonate to precipitate lithium carbonate and filter; 7) Pulverize the filter cake obtained in step 6) with dilute sulfuric acid water to dissolve the iron and phosphorus elements in the filter cake; filter to obtain a filtrate; 8) Add the extractant described in claim 1 to the filtrate obtained in step 7) and adjust the iron and phosphorus element content and concentration; 9) Drop ammonia water or liquid caustic soda into the solution obtained in step 8), and control the pH value to stably precipitate iron phosphate; 10) Heat up and age the reaction system obtained in step 9) and keep it warm; After cooling, filter, wash, and dry the filter cake to obtain battery-grade iron phosphate.

7. The recovery method according to claim 6, wherein The discharging method in step 1) is discharging through a discharger or brine; and / or, the inert gas used in step 2) is one or more of carbon dioxide, nitrogen, argon, and helium.

8. The recycling method according to claim 6 or 7, characterized in that, The cracking temperature in step 3) is 300 to 600 °C; and / or, in step 7), the molar ratio of sulfuric acid to iron element in the filter cake is 1.5 to 2.5, and the concentration of dilute sulfuric acid is 10% to 15%.

9. The recovery method according to any one of claims 6-8, characterized in that, In step 8), the molar ratio of iron element to phosphorus element in the filtrate is 0.98 to 1.03, and the concentration is 0.1 mol / L to 0.12 mol / L; and / or, the dosage of the extractant is 1% to 10% of the weight of iron phosphate.

10. According to the preparation method described in any one of claims 6-9, the pH in step 9) is controlled at 1.8 to 2.5; and / or, the temperature in step 10) is controlled at 85 to 99 °C; the heat preservation time is 2 to 10 hours.

Images