A high-efficiency recycling method of lithium-extracted waste residue

Abstract

The application discloses a kind of efficient recycling methods of lithium extraction waste residue, comprising the following steps: into the water mixture of lithium extraction phosphorus iron slag, solid-liquid separation, obtain acid leaching solution;Then join phosphorus source and iron source and adjust iron phosphorus ratio, again join precipitant and adjust pH so that iron, phosphorus element precipitates and obtains intermediate;Calcine intermediate to iron phosphate.The application has short recovery cycle, low cost, low corrosivity to equipment, simple operation, and is suitable for industrial use;The recovery rate of obtained iron phosphate is high, and the purity is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery recycling, and in particular to a high-efficiency recycling method for waste residues after lithium extraction. BACKGROUND

[0002] Lithium ion batteries, as a device for converting chemical energy and electrical energy, are widely used in new energy electric vehicles, portable electronic devices and other fields. Lithium iron phosphate batteries, due to their low price, good safety and high cycle times, have gradually become mainstream with a global shipment volume of 172.1 GWh in 2021. The huge production capacity has brought the problem of scrap after the end of the life of lithium iron phosphate batteries. Currently, the valuable elements in the recycled lithium iron phosphate battery powder are mainly extracted by acid leaching to leach out lithium. However, the lithium-extracted phosphorus iron slag is mostly treated as hazardous waste. The lithium-extracted phosphorus iron graphite slag contains about 50% iron and phosphorus elements. If it is directly discarded or improperly treated, it will not only pollute the environment, but also waste resources. How to effectively treat the lithium-extracted phosphorus iron graphite slag to effectively utilize the iron and phosphorus elements is a problem to be solved.

[0003] CN115448279A discloses a method for recovering and preparing battery-grade lithium iron phosphate material from lithium-extracted phosphorus iron slag. The method comprises the following steps: mixing the lithium-extracted phosphorus iron slag with concentrated sulfuric acid, adding iron powder for reduction, adding oxalic acid for complexation in the acid leaching solution, adjusting the pH to remove impurities to obtain a ferrous sulfate solution, adding hydrogen peroxide to the filtered ferrous sulfate solution, diluting with water, precipitating ferrous phosphate at high temperature, adding phosphoric acid solution to convert the entrained iron hydroxide into ferrous phosphate, and filtering the ferrous phosphate precipitate to remove the entrained complexing agent by high-temperature calcination. CN111646447A provides a method for recovering lithium iron phosphate from lithium-extracted phosphorus iron slag of lithium iron phosphate batteries. The method comprises the following steps: mixing the lithium-extracted phosphorus iron slag of lithium iron phosphate batteries with water to form a slurry, reacting with acid, and then separating the solid and liquid to obtain a leaching solution containing iron and phosphorus ions. The leaching solution is then treated by adding iron to remove copper and resin to remove aluminum to obtain a purified solution. The P: Fe ratio of the synthesized stock solution is adjusted by adding ferrous phosphate heptahydrate or phosphoric acid. Hydrogen peroxide and ammonia water are added to adjust the pH to obtain a lithium iron phosphate precursor precipitate. After post-treatment, a battery-grade lithium iron phosphate precursor product is obtained.

[0004] The method in CN115448279A and CN111646447A uses excessive oxidizing agent and strong acid in the acid leaching process, and a large amount of alkali in the impurity removal and precipitation process, which has high production cost, low economic benefit, large amount of waste salt, and strong corrosion to equipment. Meanwhile, the process in CN115448279A is complicated because iron powder reduction is performed after acid leaching and oxidation is performed later, and the yield of iron and phosphorus elements leached by strong acid is low, resulting in large waste of iron and phosphorus resources; the leaching solution in CN111646447A is subjected to a series of impurity removal, which not only introduces impurity elements, but also makes the impurity removal process complicated. Therefore, improvement is needed. SUMMARY

[0005] Based on the technical problems in the background art, the present application provides a high-efficiency recycling method for lithium-extracted waste residue, which has short recycling period, low cost, low corrosion to equipment, simple operation, and is suitable for industrial use; and the obtained iron phosphate has high recovery rate and high purity.

[0006] The present application provides a high-efficiency recycling method for lithium-extracted waste residue, which comprises the following steps: introducing chlorine gas into a water mixture of lithium-extracted phosphorus-iron residue, performing solid-liquid separation to obtain an acid leaching solution; then adding a phosphorus source and an iron source to adjust the iron-phosphorus ratio, adding a precipitant, and adjusting the pH to make iron and phosphorus elements precipitate to obtain an intermediate; and calcining the intermediate into iron phosphate.

[0007] In the present application, chlorine gas is introduced into a water mixture of lithium-extracted phosphorus-iron residue, which can generate dilute hydrochloric acid and hypochlorous acid with oxidizing property at the same time, achieving P and Fe leaching and oxidizing Fe 2+ in one step, which can greatly shorten the recycling time, simplify the steps, fully leach Fe and P, and improve the yield; the corrosion of chlorine gas to equipment is lower than that of concentrated sulfuric acid and strong alkali, which can reduce the damage to equipment; and the impurity removal steps in the present application are fewer, which can avoid the loss of Fe and P in multiple and various impurity removal processes. The whole recycling method is simple to operate and can realize industrial production. The iron phosphate recycled in the present application has high purity and can be directly used in batteries.

[0008] The chlorine gas can be industrial chlorine gas or recycled chlorine gas, which can reduce the cost.

[0009] Preferably, the flow rate of chlorine gas is 2.5-3.5 mL / min.

[0010] Preferably, the time for introducing chlorine gas is 0.4-0.6 h.

[0011] Preferably, the temperature during the introduction of chlorine gas is 70-90℃, and after the introduction of chlorine gas is completed, the reaction is kept for 0.8-1.2 h.

[0012] Preferably, the pH of the acid leaching solution is ≤1.2.

[0013] By adjusting the proper chlorine flow, time and pH of the acid leaching solution, the Fe and P in the lithium-extracted phosphorous iron slag can be fully leached, and the yield is improved; and by adjusting the pH of the acid leaching solution, the Cu 2+ and other impurities are less dissolved in the leaching solution.

[0014] Preferably, the iron-phosphorus ratio is 0.96-0.98:1.

[0015] The above iron-phosphorus ratio refers to the molar ratio of Fe and P.

[0016] Preferably, the precipitant is at least one of polyacrylamide and oxalic acid.

[0017] Preferably, after adjusting the iron-phosphorus ratio, the molar weight ratio of iron element to precipitant is 0.01-0.1 mol:0.1-0.3 g.

[0018] Preferably, the precipitant is added and the pH is adjusted to 1.8-2.5.

[0019] Preferably, the temperature during precipitation is 70-90℃.

[0020] By selecting a proper iron-phosphorus ratio, a proper amount of precipitant and a proper pH, the precipitation of iron and phosphorus can be accelerated, the recovery time is shortened, the impurity elements generated during precipitation can be avoided from being mixed in the ferric sulfate, the iron and phosphorus can be fully separated, the yield is improved, and the impurities are further removed.

[0021] Preferably, the calcination temperature is 200-600℃; the calcination can also remove the crystal water in the ferriphosphite dihydrate and the organic precipitant, avoid the introduction of impurities, and prepare a battery-grade ferric phosphate.

[0022] Preferably, the phosphorus source is at least one of ammonium phosphate and phosphoric acid.

[0023] Preferably, the iron source is at least one of iron powder and ferric chloride.

[0024] The pH can be adjusted by using a 32% mass fraction sodium hydroxide aqueous solution, a 20% mass fraction ammonia water, a hydrochloric acid aqueous solution, etc.

[0025] Beneficial effects:

[0026] After the chlorine gas is introduced into the phosphorous iron slag, the P and Fe are leached, and the Fe 2+The method reduces the problems of high cost and strong corrosion caused by using strong acid and oxidant, shortens the recovery time and improves the recovery efficiency, and can make Fe and P in the lithium-extracted phosphorous iron slag fully leach by selecting appropriate chlorine flow, time and pH of the acid leaching solution, improve the yield, accelerate the precipitation of iron and phosphorus by selecting appropriate iron-phosphorus ratio, appropriate amount of precipitant and appropriate pH, shorten the recovery time, and make the iron and phosphorus fully precipitate and separate, improve the yield, and the pH of each step can well remove impurities, so that the iron phosphate has high purity and can be directly used in batteries. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A process flow chart of the efficient recycling method of the lithium-extracted waste slag is shown in the figure. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be described in detail below through specific examples.

[0029] Example 1

[0030] An efficient recycling method of lithium-extracted waste slag, comprising the following steps:

[0031] Take 20g of lithium-extracted phosphorous iron slag, add 60g of water and mix well, start the stirring and heating device, heat to 80℃, and pass industrial chlorine gas at a flow rate of 3mL / min for 0.5h, then keep stirring for 1h, filter out the graphite slag to obtain an acid leaching solution with pH=1.0; add phosphoric acid and iron powder to the acid leaching solution to adjust the iron-phosphorus ratio to 0.97:1 (at this time the molar number of iron elements in the solution is 0.03mol), then add 0.2g of polyacrylamide and adjust the pH to 2.0 with dilute hydrochloric acid, adjust the temperature to 80℃, stir and mix well for 0.5h, then stand for 10min to make the iron and phosphorus elements precipitate quickly, filter the filter cake to obtain an intermediate; take the intermediate and calcine at 600℃ for 1h to remove impurities such as crystal water and polyacrylamide to obtain iron phosphate.

[0032] Example 2

[0033] An efficient recycling method of lithium-extracted waste slag, comprising the following steps:

[0034] Take 20 g of lithium extraction phosphorus iron slag, add 60 g of water and mix well, turn on the stirring and heating device, heat to 70℃, and pass in industrial chlorine gas at a flow rate of 2.5 mL / min for 0.5 h, then keep stirring for 1 h, filter out the graphite slag to obtain an acid leaching solution with pH = 1.2; add ammonium phosphate and ferric chloride to the acid leaching solution to adjust the iron-phosphorus ratio to 0.96:1 (at this time the number of moles of iron elements in the solution is 0.02 mol), then add 0.1 g of polyacrylamide and adjust the pH to 1.80 with dilute hydrochloric acid, adjust the temperature to 70℃, stir and mix for 0.5 h, then stand for 10 min to make the iron and phosphorus elements precipitate quickly, filter the filter cake to obtain an intermediate; calcine the intermediate at 200℃ for 1 h to remove impurities such as crystal water and polyacrylamide to obtain ferric phosphate.

[0035] Example 3

[0036] A high-efficiency recycling method for waste slag after lithium extraction, comprising the following steps:

[0037] Take 20 g of lithium extraction phosphorus iron slag, add 60 g of water and mix well, turn on the stirring and heating device, heat to 70℃, and pass in industrial chlorine gas at a flow rate of 3.5 mL / min for 0.5 h, then keep stirring for 1 h, filter out the graphite slag to obtain an acid leaching solution with pH = 0.8; then adjust the pH of the acid leaching solution to 4 with 20% ammonia water, filter out the impurities and take the filtrate; add phosphoric acid and iron powder to the acid leaching solution to adjust the iron-phosphorus ratio to 0.98:1 (at this time the number of moles of iron elements in the solution is 0.015 mol), then add 0.3 g of polyacrylamide and adjust the pH to 2.2 with dilute hydrochloric acid, adjust the temperature to 70℃, stir and mix for 0.5 h, then stand for 10 min to make the iron and phosphorus elements precipitate quickly, filter the filter cake to obtain an intermediate; calcine the intermediate at 400℃ for 1 h to remove impurities such as crystal water and polyacrylamide to obtain ferric phosphate.

[0038] Comparative Example 1

[0039] The pH of the acid leaching solution is 1.5, and the other conditions are the same as in Example 1. The lithium extraction phosphorus iron slag used in Example 1 and Comparative Example 1 is the same batch, and their weights are the same.

[0040] Comparative Example 2

[0041] Add polyacrylamide and adjust the pH to 3 with dilute hydrochloric acid, and the other conditions are the same as in Example 1. The lithium extraction phosphorus iron slag used in Example 1 and Comparative Example 2 is the same batch, and their weights are the same.

[0042] The ferric phosphate obtained in Examples 1-3 and Comparative Examples 1-2 was detected, and the yield was calculated. The results are shown in Table 1.

[0043] Table 1 Detection results

[0044] Test item HG / T 4701-2021 Yield % Recovery time h Example 1 Comply with Type I requirements 95.45 4 Example 2 Comply with Type I requirements 94.67 4 Example 3 Comply with Type I requirements 95.21 4 Comparative Example 1 Comply with Type II requirements 90.75 4 Comparative Example 2 Not comply with requirements 84.48 4

[0045] Note: HG / T 4701-2021 is the quality standard for iron phosphate for batteries.

[0046] As can be seen from Table 1, the iron phosphate obtained by the present application has better quality and high yield.

[0047] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacements or changes according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for the efficient recycling of waste residue after lithium extraction, characterized in that, The process includes the following steps: chlorine gas is introduced into the aqueous mixture of lithium-phosphorus iron slag to separate the solid and liquid phases and obtain an acid leaching solution; then phosphorus and iron sources are added to adjust the iron-phosphorus ratio, and a precipitant is added and the pH is adjusted to precipitate iron and phosphorus elements to obtain an intermediate; the intermediate is calcined to obtain iron phosphate. The flow rate of chlorine gas is 2.5-3.5 mL / min; The pH of the acid leaching solution is 1.0-1.2; The iron-to-phosphorus ratio is 0.96-0.98:1; The precipitant is polyacrylamide; Add a precipitant and adjust the pH to 1.8-2.

5.

2. The method for efficient recycling of lithium extraction waste residue according to claim 1, characterized in that, The calcination temperature is 200-600℃.

3. The method for efficient recycling of lithium extraction waste residue according to claim 1 or 2, characterized in that, The phosphorus source is at least one of ammonium phosphate and phosphoric acid.

4. The method for efficient recycling of lithium extraction waste residue according to claim 1 or 2, characterized in that, The iron source is at least one of iron powder and ferric chloride.

Images