A method for jointly recovering lithium and graphite from positive and negative electrode black powder

Abstract

The present invention relates to a method for jointly recovering lithium and graphite from positive and negative black powder. The positive and negative black powder is slurried with water; then flotation is carried out to obtain flotation foam and flotation slurry, which are dehydrated respectively to obtain crude graphite and crude lithium iron phosphate products; the crude graphite product is pickled with concentrated acid to remove impurities, obtaining graphite product and pickling residual liquid; if the hydrogen ion concentration in the pickling residual liquid is not less than 3 mol / L, it can be used as concentrated acid residual liquid; if the hydrogen ion concentration in the pickling residual liquid is less than 3 mol / L, then its hydrogen ion concentration is adjusted to 1.5 - 3 mol / L and used as dilute acid residual liquid; the crude lithium iron phosphate product is selectively leached with the dilute acid residual liquid and an oxidant to obtain a lithium-containing leaching solution and phosphoferrite slag; sodium hydroxide is added to adjust the pH value of the lithium-containing leaching solution for impurity removal, and then sodium carbonate is added for lithium precipitation reaction to obtain lithium carbonate product. The beneficial effects of the present invention are: short-process high-value recovery of positive and negative black powder can be realized, and it has the advantages of high purity of graphite product, simple process flow, obvious economic benefits, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of waste lithium battery recycling, and particularly relates to a method for jointly recycling lithium and graphite from the positive and negative black powders. Background Art

[0002] With the increasing prominence of energy and environmental issues and the emergence of the concepts of "carbon peak" and "carbon neutrality", the new energy vehicle and energy storage markets in China have shown an explosive growth trend. Lithium iron phosphate is widely used due to its excellent safety performance, long cycle life and low cost. Its demand is expected to exceed that of ternary batteries and become the focus of current waste power battery recycling. With the increase in the amount of waste, if waste batteries are not properly treated, it will cause serious environmental pollution and energy waste. Recycling and reuse can not only avoid environmental pollution but also have certain economic benefits. Therefore, it is an urgent problem to reasonably and efficiently recycle waste lithium iron phosphate batteries, and relevant research is particularly important.

[0003] CN112670614A discloses a physical separation method for the positive and negative electrode materials of waste lithium iron phosphate batteries. First, the organic matter is removed by pyrolyzing the mixed materials, then the adhesion between the positive electrode material and graphite is eliminated by rod milling, and finally graphite is recovered step by step by flotation and high-gradient magnetic separation. Although this method can better separate the positive electrode material and graphite, and has little environmental pollution, it has the disadvantages of low purity of graphite products and difficulty in large-scale industrialization.

[0004] CN113285135A discloses a method for recycling multiple components of waste lithium iron phosphate batteries. By adding lithium iron phosphate coarse powder to an acid solution for reaction, an acid leaching solution and carbon slag are obtained after filtration. The carbon slag is washed and dried to obtain high-carbon graphite; the acid leaching solution can be processed through a series of steps to obtain iron phosphate and lithium carbonate products. Although this method can obtain products such as high-carbon graphite, iron phosphate and lithium carbonate at the same time, it has the problems of complex process and large consumption of acids and alkalis, resulting in poor economic benefits, and the impurity content in the obtained acid leaching solution is high, making subsequent treatment difficult.

[0005] CN114566729A discloses a method for comprehensive recycling of waste lithium iron phosphate batteries. By leaching the positive and negative powders with sulfuric acid at a concentration of 100 - 200 g / L, graphite and a leaching solution are obtained, then the iron in the leaching solution is removed, and finally battery-grade lithium carbonate is refined in an alcohol-water system. Although this method can obtain graphite and lithium carbonate products at the same time, the concentration of sulfuric acid used is too low, which will result in low purity of graphite products.

[0006] The solutions reported in the above patent documents have problems such as low purity of graphite products, complex processes, difficulty in large-scale industrialization, and poor economic benefits, and cannot achieve short-process high-value recovery of positive and negative black powders. In actual use, it is easy to cause problems such as complex process flows and poor economic benefits. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for jointly recovering lithium and graphite from positive and negative black powders to overcome the deficiencies in the above-mentioned prior art.

[0008] The technical solution of the present invention to solve the above technical problem is as follows: A method for jointly recovering lithium and graphite from positive and negative black powders includes the following steps:

[0009] S1. Add water to the positive and negative black powders to make a slurry.

[0010] S2. Float the slurry obtained in S1 to obtain flotation foam and flotation slurry, dehydrate the flotation foam to obtain a crude graphite product, and dehydrate the flotation slurry to obtain a crude lithium iron phosphate product.

[0011] S3. Pickle and remove impurities from the crude graphite product obtained in S2 with concentrated acid, filter to obtain a graphite product and pickling waste liquid.

[0012] If the hydrogen ion concentration in the obtained pickling waste liquid is not less than 3 mol / L, the pickling waste liquid can be regarded as concentrated acid waste liquid and can be returned for pickling the crude graphite product.

[0013] If the hydrogen ion concentration in the obtained pickling waste liquid is less than 3 mol / L, add the concentrated acid or water described in S3 to adjust its hydrogen ion concentration to be between 1.5 mol / L and 3 mol / L. The adjusted pickling waste liquid can be regarded as dilute acid waste liquid.

[0014] S4. Selectively leach the crude lithium iron phosphate product obtained in S2 with dilute acid waste liquid and an oxidant, filter to obtain a lithium-containing leaching solution and phosphorus iron slag.

[0015] S5. Add sodium hydroxide to the lithium-containing leaching solution obtained in S4, adjust its pH value to 10.0 - 12.0 for impurity removal, and then add sodium carbonate for lithium precipitation reaction to finally obtain a lithium carbonate product.

[0016] Based on the above technical solution, the present invention can also be improved as follows.

[0017] Further, the positive and negative black powders are powders obtained by crushing, copper removal, and aluminum removal of lithium iron phosphate positive and negative electrode materials.

[0018] Further, the proportion of particles with a particle size less than 0.074 mm in the positive and negative black powders is 60 wt% - 90 wt%.

[0019] Further, the concentration of the slurry in S1 is 8wt% - 15wt%.

[0020] Further, during the flotation in S2, a foaming agent 2# oil and a regulator are added to the slurry.

[0021] Furthermore, the regulator is one or two of phosphoric acid, sodium hexametaphosphate, and sodium phosphate.

[0022] Further, the concentrated acid for acid washing and impurity removal of the crude graphite product in S3 is one of hydrochloric acid and sulfuric acid.

[0023] Furthermore, the concentrated acid is hydrochloric acid with a concentration not less than 4mol / L.

[0024] Furthermore, the concentrated acid is sulfuric acid with a concentration not less than 3mol / L.

[0025] Further, the oxidant in S4 is one or more of hydrogen peroxide, ozone, oxygen, and sodium hypochlorite.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1) By performing flotation pretreatment before selective leaching and adopting a combination of concentrated acid washing for impurity removal and dilute acid selective leaching according to the characteristics of the flotation product, short-process high-value recovery of positive and negative black powders is achieved, with the advantages of high purity of graphite products, simple process flow, and obvious economic benefits;

[0028] 2) Using concentrated acid washing for impurity removal, the obtained graphite product has higher purity and better economic benefits;

[0029] 3) Adopting the dilute acid selective leaching method, the consumption of acid and alkali is small, and the economic benefits are obvious;

[0030] 4) The process flow is simple and easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flowchart of the method for jointly recovering lithium and graphite from positive and negative black powders according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0033] Example 1

[0034] As Figure 1 shown, a method for jointly recovering lithium and graphite from positive and negative black powders includes the following steps:

[0035] The positive and negative black powders are mixed with water to form a slurry with a concentration of 8wt%;

[0036] Then, frother 2# oil and phosphoric acid are added for flotation to obtain flotation foam and flotation slurry, which are dehydrated to obtain crude graphite product and crude iron-lithium product respectively;

[0037] The obtained crude graphite product is then pickled with 4 mol / L hydrochloric acid to remove impurities, and then filtered to obtain a graphite product and a pickling residue;

[0038] If the hydrogen ion concentration in the obtained pickling residual solution is not less than 3 mol / L, the pickling residual solution can be regarded as concentrated acid residual solution and can be used to continue pickling and removing impurities from the crude graphite product;

[0039] If the hydrogen ion concentration in the obtained pickling residual solution is less than 3 mol / L, water is added to adjust the hydrogen ion concentration in the pickling residual solution to 1.5 mol / L. The adjusted pickling residual solution is the dilute acid residual solution.

[0040] The obtained dilute acid residue and hydrogen peroxide are selectively leached to obtain a crude iron-lithium product, which is then filtered to obtain a lithium-containing leachate and ferrophosphorus slag;

[0041] Finally, sodium hydroxide is added to the obtained lithium-containing leachate to adjust the pH to 11.0 for impurity removal, and then sodium carbonate is added to carry out lithium precipitation reaction to finally obtain a lithium carbonate product.

[0042] The positive and negative electrode black powder in the above embodiment is a powder obtained by crushing, removing copper and aluminum from the positive and negative electrode materials of lithium iron phosphate, and the particle size is less than 0.074 mm, accounting for 60wt%, of which the lithium content is 2.83%, the C content is 26.73%, the purity of the obtained graphite product is 99.1%, the recovery rate is 76.4%, and the purity of the obtained lithium carbonate product is 99.0%.

[0043] Example 2

[0044] like Figure 1 As shown, a method for jointly recovering lithium and graphite from positive and negative electrode black powder comprises the following steps:

[0045] Add water to the positive and negative electrode black powder to make a slurry to a concentration of 10wt%;

[0046] Then, frother 2# oil and sodium hexametaphosphate are added for flotation to obtain flotation foam and flotation slurry, which are dehydrated to obtain crude graphite product and crude iron-lithium product respectively;

[0047] The obtained crude graphite product is then pickled with 3 mol / L sulfuric acid to remove impurities, and then filtered to obtain a graphite product and a pickling residue;

[0048] If the hydrogen ion concentration in the obtained pickling residual solution is not less than 3 mol / L, the pickling residual solution can be regarded as concentrated acid residual solution and can be used to continue pickling and removing impurities from the crude graphite product;

[0049] If the hydrogen ion concentration in the pickling waste liquid obtained is less than 3 mol / L, water is added to adjust the hydrogen ion concentration in the pickling waste liquid to 2 mol / L, and the adjusted pickling waste liquid is the dilute acid waste liquid;

[0050] The obtained dilute acid waste liquid and the iron-lithium crude product obtained by selective leaching with oxygen are filtered to obtain a lithium-containing leaching solution and phosphorus iron slag;

[0051] Finally, sodium hydroxide is added to the obtained lithium-containing leaching solution, the pH is adjusted to 10.0 for impurity removal, and then sodium carbonate is added for lithium precipitation reaction to finally obtain lithium carbonate product.

[0052] In the above embodiment, the positive and negative black powders are powders obtained by crushing, copper removal, and aluminum removal of the lithium iron phosphate positive and negative electrode materials. Those with a particle size less than 0.074 mm account for 90 wt%. Among them, the lithium content is 2.83%, the C content is 26.73%, the purity of the obtained graphite product is 98.7%, and the recovery rate is 85.3%. The purity of the obtained lithium carbonate product is 98.6%.

[0053] Example 3

[0054] As Figure 1 shown, a method for jointly recovering lithium and graphite from positive and negative black powders includes the following steps:

[0055] The positive and negative black powders are slurried with water to a concentration of 15 wt%;

[0056] Then, foaming agent No. 2 oil and sodium phosphate are added for flotation to obtain flotation foam and flotation slurry, which are dehydrated respectively to obtain graphite crude product and iron-lithium crude product;

[0057] The obtained graphite crude product is pickled and purified with 6 mol / L sulfuric acid, and then filtered to obtain graphite product and pickling waste liquid;

[0058] If the hydrogen ion concentration in the obtained pickling waste liquid is not less than 3 mol / L, the pickling waste liquid can be regarded as concentrated acid waste liquid and can be used to continue pickling and purifying the graphite crude product;

[0059] If the hydrogen ion concentration in the obtained pickling waste liquid is less than 3 mol / L, water is added to adjust the hydrogen ion concentration in the pickling waste liquid to 2 mol / L, and the adjusted pickling waste liquid is the dilute acid waste liquid;

[0060] The obtained dilute acid waste liquid and the iron-lithium crude product obtained by selective leaching with ozone are filtered to obtain a lithium-containing leaching solution and phosphorus iron slag;

[0061] Finally, sodium hydroxide is added to the obtained lithium-containing leaching solution, the pH is adjusted to 12.0 for impurity removal, and then sodium carbonate is added for lithium precipitation reaction to finally obtain lithium carbonate product.

[0062] In the above embodiments, the positive and negative black powders are powders obtained by crushing, removing copper, and removing aluminum from the lithium iron phosphate positive and negative electrode materials. 70 wt% of them have a particle size less than 0.074 mm. Among them, the lithium content is 2.83%, the C content is 26.73%, the purity of the obtained graphite product is 99.3%, the recovery rate is 83.7%, and the purity of the obtained lithium carbonate product is 98.5%.

[0063] Example 4

[0064] As Figure 1 shown, a method for jointly recovering lithium and graphite from positive and negative black powders includes the following steps:

[0065] Adjust the slurry concentration of the positive and negative black powders to 12 wt% by adding water;

[0066] Then add foaming agent No. 2 oil, phosphoric acid, and sodium phosphate for flotation to obtain flotation foam and flotation slurry, dehydrate them respectively, and obtain crude graphite product and crude iron-lithium product respectively;

[0067] Then pickling and impurity removal of the obtained crude graphite product with 6 mol / L hydrochloric acid, and then filtering to obtain graphite product and pickling residual liquid;

[0068] If the hydrogen ion concentration in the obtained pickling residual liquid is not less than 3 mol / L, the pickling residual liquid can be regarded as concentrated acid residual liquid and can be used to continue pickling and impurity removal of the crude graphite product;

[0069] If the hydrogen ion concentration in the obtained pickling residual liquid is less than 3 mol / L, then add concentrated hydrochloric acid to adjust the hydrogen ion concentration in the pickling residual liquid to 2.5 mol / L. The adjusted pickling residual liquid is dilute acid residual liquid;

[0070] Selectively leach the obtained crude iron-lithium product with the obtained dilute acid residual liquid and sodium hypochlorite, and then filter to obtain lithium-containing leaching solution and phosphorus-iron slag;

[0071] Finally, add sodium hydroxide to the obtained lithium-containing leaching solution, adjust the pH to 11.5 for impurity removal, and then add sodium carbonate for lithium precipitation reaction to finally obtain lithium carbonate product.

[0072] In the above embodiments, the positive and negative black powders are powders obtained by crushing, removing copper, and removing aluminum from the lithium iron phosphate positive and negative electrode materials. 80 wt% of them have a particle size less than 0.074 mm. Among them, the lithium content is 2.83%, the C content is 26.73%, the purity of the obtained graphite product is 99.8%, the recovery rate is 79.6%, and the purity of the obtained lithium carbonate product is 98.8%.

[0073] Example 5

[0074] As Figure 1 shown, a method for jointly recovering lithium and graphite from positive and negative black powders includes the following steps:

[0075] The positive and negative black powders are mixed with water to form a slurry with a concentration of 9 wt%.

[0076] Then, a foaming agent (No. 2 oil), phosphoric acid, and sodium hexametaphosphate are added for flotation to obtain flotation foam and flotation slurry, which are dehydrated separately to obtain crude graphite products and crude lithium iron phosphate products respectively.

[0077] The obtained crude graphite products are pickled with 10 mol / L sulfuric acid to remove impurities, and then filtered to obtain graphite products and pickling waste liquid.

[0078] If the hydrogen ion concentration in the obtained pickling waste liquid is not less than 3 mol / L, the pickling waste liquid can be regarded as concentrated acid waste liquid and can be used to continue pickling and impurity removal of the crude graphite products.

[0079] If the hydrogen ion concentration in the obtained pickling waste liquid is less than 3 mol / L, concentrated sulfuric acid is added to adjust the hydrogen ion concentration in the pickling waste liquid to 3 mol / L, and the adjusted pickling waste liquid is the dilute acid waste liquid.

[0080] The obtained dilute acid waste liquid, hydrogen peroxide, and a mixed gas of ozone and oxygen are used to selectively leach the obtained crude lithium iron phosphate products, and then filtered to obtain a lithium-containing leaching solution and phosphoferrite slag.

[0081] Sodium hydroxide is added to the obtained lithium-containing leaching solution to adjust the pH to 10.5 for impurity removal, and then sodium carbonate is added for lithium precipitation reaction to finally obtain lithium carbonate products.

[0082] In the above examples, the positive and negative black powders are powders obtained after the lithium iron phosphate positive and negative electrode materials are crushed, copper-removed, and aluminum-removed. The proportion of particles with a particle size less than 0.074 mm is 75 wt%. Among them, the lithium content is 2.83%, the C content is 26.73%. The purity of the obtained graphite products is 99.7%, and the recovery rate is 78.8%. The purity of the obtained lithium carbonate products is 99.1%.

[0083] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for jointly recovering lithium and graphite from positive and negative electrode black powder, characterized in that: The steps include: S1. Add water to the positive and negative electrode black powders to prepare a slurry with a concentration of 8 wt% to 15 wt%. The positive and negative electrode black powders are obtained by crushing, removing copper and aluminum from the positive and negative electrode materials of lithium iron phosphate. The particles of the positive and negative electrode black powders have a diameter of less than 0.074 mm, accounting for 60 wt% to 90 wt% of the particles. S2. flotation of the slurry obtained in S1, adding a foaming agent 2# oil and a conditioning agent to the slurry during flotation, wherein the conditioning agent is one or two of phosphoric acid, sodium hexametaphosphate, and sodium phosphate to obtain flotation foam and flotation slurry, and dehydrating the flotation foam to obtain a crude graphite product, and dehydrating the flotation slurry to obtain a crude iron-lithium product; S3, pickling the crude graphite product obtained in S2 with concentrated acid to remove impurities, filtering, and obtaining a graphite product and a pickling residue, wherein if the concentrated acid is hydrochloric acid, the concentration thereof is not less than 4 mol / L; if the concentrated acid is sulfuric acid, the concentration thereof is not less than 3 mol / L; If the hydrogen ion concentration in the obtained pickling residual liquid is not less than 3 mol / L, the pickling residual liquid can be regarded as concentrated acid residual liquid and can be returned for pickling crude graphite product; If the hydrogen ion concentration in the obtained pickling residual solution is less than 3 mol / L, the concentrated acid or water described in S3 is added to adjust the hydrogen ion concentration to 1.5 mol / L to 3 mol / L, and the adjusted pickling residual solution can be regarded as a dilute acid residual solution; S4, selectively leaching the crude iron-lithium product obtained in S2 with the dilute acid residue and an oxidant, filtering to obtain a lithium-containing leachate and ferrophosphorus slag; S5. Sodium hydroxide is added to the lithium-containing leachate obtained in S4, and its pH value is adjusted to 10.0-12.0 to remove impurities, and then sodium carbonate is added to carry out lithium precipitation reaction, and finally a lithium carbonate product can be obtained.

2. The method for jointly recovering lithium and graphite from positive and negative electrode black powder according to claim 1, characterized in that: The oxidant in S4 is one or more of hydrogen peroxide, ozone, oxygen and sodium hypochlorite.

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