Method for resource utilization of lithium iron phosphate battery phosphorus iron slag

Abstract

The application discloses a method for recycling and utilizing lithium iron phosphate battery phosphorus iron slag resources, in which copper in lithium extraction residue is washed away by oxidizing acid washing, and only a small amount of copper exists in lithium extraction residue leaching liquor, so that the product quality is not affected. Subsequently, crude lithium iron phosphate is obtained, and aluminum is washed and removed, and the washing liquid can be returned to the leaching section for reuse, so that the process is simple, the cost is low, and the recovery of battery-grade lithium iron phosphate is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium iron phosphate battery recycling, in particular to a method for resource utilization of lithium iron phosphate battery phosphorus iron slag. BACKGROUND

[0002] Lithium iron phosphate (LiFePO4) batteries are widely used in electric vehicles and large-scale energy storage facilities due to their excellent thermal stability, long service life and relatively safe characteristics. With the rapid growth of these fields, the number of waste lithium iron phosphate batteries is also increasing. These waste lithium iron phosphate batteries contain a large amount of valuable metals such as lithium, iron and phosphorus, which are valuable resources. By recycling the iron and phosphorus in the lithium extraction residue of waste lithium iron phosphate batteries, the demand for natural mineral resources can be reduced, resources can be saved, a closed-loop economy can be established, the dependence on new resources for battery production can be reduced, and the burden of waste disposal can be reduced.

[0003] Some scholars have studied the recovery of lithium iron phosphate waste, such as patent CN116854112A "Method for recycling and preparing lithium carbonate from waste lithium iron phosphate battery", which mainly mixes waste lithium iron phosphate battery powder with water, oxidizing agent, acid solution and surfactant, reacts, solid-liquid separation, obtains leaching solution with pH = 2-2.5, and repeats the use of leaching solution three times to enrich the concentration of lithium. The lithium-rich solution is used to recover lithium carbonate, and then the recovery of iron and phosphorus is not mentioned. Patent CN116730307A reports "Method for removing copper and aluminum from lithium iron phosphate waste leaching solution", which dissolves the retired lithium iron phosphate positive electrode waste with acid to obtain a leaching solution containing copper and aluminum impurities, then adds sulfide to remove copper and fluoride to remove aluminum. Although good impurity removal effect is achieved, the introduction of sulfur ions and fluoride ions will increase the processing difficulty of subsequent processes. SUMMARY

[0004] The purpose of the present application is to provide a method for resource utilization of lithium iron phosphate battery phosphorus iron slag to solve the above problems. The present application takes the lithium extraction residue of lithium iron phosphate as the treatment object, and through the processes of oxidation acid washing, leaching, precipitation regeneration, washing and calcination, battery-grade lithium iron phosphate is prepared from the lithium extraction residue of lithium iron phosphate, realizing effective disposal of lithium extraction residue and recycling of iron and phosphorus resources in the residue.

[0005] The existing patent is difficult to remove impurities in depth when recovering lithium iron phosphate, and after extracting lithium from lithium iron phosphate waste, the phosphorus and iron resources in the slag are idle or sold at a low price. Even if the method of removing impurities is used to remove copper and aluminum impurities, the cost is usually high. The present technology first washes the copper in the lithium extraction slag with an oxidizing acid, leaving only a small amount of copper in the lithium extraction slag leaching solution, which does not affect the product quality. Then the obtained crude phosphoric acid iron is pickled, and the aluminum is washed and removed, and the washing liquid can be returned to the leaching section for reuse, the process is simple, the cost is low, and the recovery of battery-grade phosphoric acid iron is realized.

[0006] The present application achieves the above-mentioned purpose by the following technical solutions:

[0007] A method for resource utilization of phosphorus iron slag of lithium iron phosphate battery, comprising the following steps:

[0008] Step 1, the phosphorus iron slag is washed with acid and oxidizing agent to obtain slag washing liquid and washing slag; the pH of the system is controlled at 0.5-2 and the oxidation potential is 300-600 mV during washing;

[0009] Step 2, the washing slag is dissolved with an acidic leaching agent and then filtered to obtain a first acidic solution containing iron, phosphorus, aluminum and copper, and a carbon residue;

[0010] Step 3, the pH value of the first acidic solution obtained in step 2 is adjusted by alkali to obtain solid hydrated phosphoric acid iron and a second acidic solution; filtering to obtain crude hydrated phosphoric acid iron product and a synthesis mother liquor;

[0011] Step 4, the crude hydrated phosphoric acid iron product obtained in step 3 is washed, first washed with dilute acid at low temperature for three times, then washed with dilute acid at high temperature for one time, and then washed with water to wash away the excess acid ions in the product;

[0012] Step 5, the washed product obtained in step 4 is dried and calcined to obtain battery-grade phosphoric acid iron product.

[0013] Further, in step 1, the acid is one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and the oxidizing agent is one or more of hydrogen peroxide, sodium chlorate, ammonium hypochlorite, ammonium persulfate and sodium persulfate; the ore pulp concentration is 15-50% during washing, and the washing is carried out at 30-90°C for 0.5-4h.

[0014] Further, in step 1, the acid is sulfuric acid, the pH value is 1-2, the oxidation potential is 400-600 mV, the ore pulp concentration is 30-50%, and the washing is carried out at 60-90°C for 0.5-2h.

[0015] Further, in step 2, the acid is sulfuric acid, the ore pulp concentration is 10-30% during leaching, and the leaching is carried out at 50-90°C for 0.5-4h.

[0016] Further, in the step 3, the alkali solution is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and aqueous ammonia solution.

[0017] When the solid hydrated iron phosphate is obtained, the pH value is 1.5-2.5, and the reaction is carried out at 25-50℃ for 0.5-4h.

[0018] Further, in the step 4, when the low-temperature washing with dilute acid is used, the acid is sulfuric acid, the pH value of the acid solution is 1.5-2.5, and the washing is carried out at 30-60℃ for 0.5-2h; when the high-temperature washing with dilute acid is used, the acid is phosphoric acid, the pH value of the acid solution is 1.0-2.0, and the washing is carried out at 70-90℃ for 2-8h.

[0019] Further, in the step 5, the hydrated iron phosphate is calcined at 550-700℃ for 2-6h to obtain the battery-grade anhydrous iron phosphate.

[0020] The present application has the following advantages:

[0021] The present application is a method for resource utilization of lithium iron phosphate battery phosphorus iron slag, which regenerates battery-grade iron phosphate at low cost by washing the lithium extraction residue and regenerated crude iron phosphate. The present application has high iron and phosphorus recovery rate, simple process flow, low reagent cost, good economic benefit, and great industrial application potential. DETAILED DESCRIPTION

[0022] The technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] Example 1

[0024] A method for resource utilization of lithium iron phosphate battery phosphorus iron slag, comprising:

[0025] A 500 g material was slurried with 40% ore slurry concentration, then washed with sulfuric acid and hydrogen peroxide to adjust the pH to 1.8 and the oxidation potential to 550 mV, and washed at 60°C for 1 h. The washed residue was leached with 2 mol / L sulfuric acid at 80°C for 2 h to obtain an acidic solution containing iron, phosphorus, aluminum, and copper. The pH of the acidic solution was then adjusted to 2.0 using sodium hydroxide, and the solution was stirred at 50°C for 2 h to obtain crude iron phosphate. The crude iron phosphate was countercurrently washed three times with dilute sulfuric acid solutions having pH values of 1.5, 1.7, and 2.0 at 50°C, and then washed once more with a phosphoric acid solution having a pH of 1.5 at 90°C. After water washing, the product was dried and filtered, and then calcined at 600°C for 5 h to obtain battery-grade iron phosphate having a copper content of 24 ppm, an aluminum content of 93 ppm, a sodium content of 55 ppm, and an iron and phosphorus recovery rate of 96%.

[0026] Example 2

[0027] The difference from Example 1 is that the pH was adjusted to 1.7 and the oxidation potential was 600 mV when washing the lithium extraction residue with sulfuric acid and hydrogen peroxide to obtain battery-grade iron phosphate having a copper content of 22 ppm, an aluminum content of 95 ppm, and an iron and phosphorus recovery rate of 94%.

[0028] Example 3

[0029] The difference from Example 1 is that the pH was adjusted to 1.6 when precipitating the crude iron phosphate from the acidic solution using sodium hydroxide to obtain battery-grade iron phosphate having a copper content of 25 ppm, an aluminum content of 91 ppm, a sodium content of 34 ppm, and an iron and phosphorus recovery rate of 92%.

[0030] Example 4

[0031] The difference from Example 1 is that the pH values of the dilute sulfuric acid solutions were 1.7, 1.7, and 1.9 when washing the crude iron phosphate to obtain battery-grade iron phosphate having a copper content of 28 ppm, an aluminum content of 105 ppm, a sodium content of 54 ppm, and an iron and phosphorus recovery rate of 97%.

[0032] Example 5

[0033] The difference from Example 1 is that the temperature was 80°C when washing the crude iron phosphate with a phosphoric acid solution to obtain battery-grade iron phosphate having a copper content of 26 ppm, an aluminum content of 93 ppm, a sodium content of 88 ppm, and an iron and phosphorus recovery rate of 95%.

[0034] Comparative Example 1

[0035] The difference from Example 1 is that the phosphorus-iron residue was not washed by oxidation, but was directly leached to obtain iron phosphate having a copper content of 130 ppm, an aluminum content of 94 ppm, and a sodium content of 67 ppm.

[0036] Comparative Example 2

[0037] The difference from Example 1 is that the crude iron phosphate is precipitated by adjusting the acid solution with sodium hydroxide, and the reaction is carried out at 90°C for 2h, and the copper content in the obtained iron phosphate is 74ppm, the aluminum content is 246ppm, and the sodium content is 87ppm.

[0038] Comparative Example 3

[0039] The difference from Example 1 is that the crude iron phosphate is washed with pure water, and then washed with phosphoric acid, and the copper content in the obtained iron phosphate is 34ppm, the aluminum content is 690ppm, and the sodium content is 67ppm.

[0040] Comparative Example 4

[0041] The difference from Example 1 is that the crude iron phosphate is washed with dilute sulfuric acid solution, and the pH is 1.0, 1.3, and 1.5, respectively, to obtain battery-grade iron phosphate, and the copper content is 22ppm, the aluminum content is 90ppm, the sodium content is 38ppm, and the iron and phosphorus recovery rate is 75%.

[0042] Comparative Example 5

[0043] The difference from Example 1 is that the crude iron phosphate is not washed with phosphoric acid solution, and the copper content in the obtained iron phosphate is 45ppm, the aluminum content is 140ppm, and the sodium content is 322ppm.

[0044] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, various possible combinations are not described again in the present application. Furthermore, various different embodiments of the present application can be combined in any manner, as long as it does not violate the idea of the present application, it should also be considered as disclosed by the present application.

Claims

1. A method for resource utilization of lithium iron phosphate battery phosphorus iron slag, characterized in that, The method comprises the following steps: Step 1, washing the phosphorus iron slag with acid and oxidant to obtain a slag washing solution and a washing residue; the pH value of the system is controlled to be 0.5-2 and the oxidation potential is 300-600 mV during the washing; Step 2, dissolving the washing residue with an acidic leaching agent and then filtering to obtain a first acidic solution containing iron, phosphorus, aluminum and copper and a carbon residue; Step 3, adjusting the pH value of the first acidic solution obtained in Step 2 with an alkali solution to obtain solid hydrated ferric phosphate and a second acidic solution; filtering to obtain a crude hydrated ferric phosphate product and a synthesis mother liquor; the alkali solution is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and an ammonia water solution; when the solid hydrated ferric phosphate is obtained, the pH value is 1.5-2.5 and the reaction is carried out at 25-50 DEG C for 0.5-4 h; Step 4, washing the crude hydrated ferric phosphate product obtained in Step 3, first washing three times at low temperature with dilute acid, then washing once at high temperature with dilute acid, and then washing off the excess acid ions in the product with water; when washing at low temperature with dilute acid, the acid is sulfuric acid, the pH value of the acid solution is 1.5-2.5, and the washing is carried out at 30-60 DEG C for 0.5-2 h; when washing at high temperature with dilute acid, the acid is phosphoric acid, the pH value of the acid solution is 1.0-2.0, and the washing is carried out at 70-90 DEG C for 2-8 h; Step 5, drying and calcining the washed product obtained in Step 4 to obtain a battery-grade ferric phosphate product.

2. The method for resource utilization of lithium iron phosphate battery phosphorus iron slag according to claim 1, characterized in that, In Step 1, the acid is one or more selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and the oxidant is one or more selected from the group consisting of hydrogen peroxide, sodium chlorate, ammonium hypochlorite, ammonium persulfate and sodium persulfate; the pulp concentration during the washing is 15-50%, and the washing is carried out at 30-90 DEG C for 0.5-4 h.

3. The method for resource utilization of lithium iron phosphate battery phosphorus iron slag according to claim 1, characterized in that, In Step 1, the acid is sulfuric acid, the pH value is 1-2, the oxidation potential is 400-600 mV, the pulp concentration is 30-50%, and the washing is carried out at 60-90 DEG C for 0.5-2 h.

4. The method for resource utilization of lithium iron phosphate battery phosphorus iron slag according to claim 1, characterized in that, In Step 2, the acid is sulfuric acid, the pulp concentration during the leaching is 10-30%, and the leaching is carried out at 50-90 DEG C for 0.5-4 h.

5. The method for resource utilization of lithium iron phosphate battery phosphorus iron slag according to claim 1, characterized in that, In Step 5, the hydrated ferric phosphate is calcined at 550-700 DEG C for 2-6 h to obtain a battery-grade anhydrous ferric phosphate.