Method for economically removing copper from waste lithium iron phosphate positive and negative electrode mixed black powder pickle liquor

Abstract

The invention discloses an economic copper removal method for waste lithium iron phosphate positive and negative electrode mixed black powder pickle liquor. The copper removal effect is remarkable. In the manufacturing process of the waste lithium iron phosphate positive and negative electrode mixed black powder, part of negative electrode plates are ground into powder and mixed into the powder, and copper elements completely enter an acid leaching solution during acid leaching, so that the content of the copper elements in the acid leaching solution reaches 1.5-4g / l. Through a segmented copper removal process, the copper element content can be reduced to 5 ppm or below, and the invention relates to the technical field of waste lithium iron phosphate positive and negative electrode mixed black powder treatment. The economic copper removal method for the waste lithium iron phosphate positive and negative electrode mixed black powder pickle liquor is remarkable in copper removal effect, purified copper powder is pure, and iron powder is completely utilized. The problem is just solved by sectional copper removal. The iron-copper slag obtained through primary copper removal, insufficient iron powder adding, most copper element removal, secondary copper removal, excessive iron powder adding and filtering is returned to the front end for primary copper removal, and complete utilization of the iron powder is achieved. And the cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of waste lithium iron phosphate positive and negative electrode treatment, and specifically to a method for economically removing copper from waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching solution. Background Art

[0002] Lithium iron phosphate (LiFePO 4 ) As a new type of positive electrode material for lithium-ion batteries, it is widely used in the electric vehicle industry due to its advantages such as abundant iron resources, low price, good cycle performance and high safety performance. However, with the rapid growth of the electric vehicle industry. At present, the recycling of waste lithium iron phosphate power batteries is mainly based on wet processes. The pre-treated waste lithium iron phosphate active materials are dissolved by acid leaching, and then copper, copper and other impurity elements are purified, and finally the metal elements in the leachate are recovered. Copper ions are impurity elements in sulfuric acid leachate. When metal elements are subsequently recovered in the form of iron phosphate and lithium carbonate precursors, the introduction of copper impurity elements will affect their electrochemical properties, so the copper removal process is particularly important.

[0003] At present, the copper removal process on the market basically adopts the one-step iron method, which leads to an increase in the use of iron powder, low utilization rate, and high impurity content in copper products. In order to solve this problem, this process is specially studied. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a method for economically removing copper from a mixed black powder acid leaching solution of waste lithium iron phosphate positive and negative electrodes, which solves the problem that the current copper removal process on the market leads to increased iron powder usage, low utilization rate, and high impurity content in copper products.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented by the following technical scheme: a method for economically removing copper from a mixed black powder acid leaching solution of waste lithium iron phosphate positive and negative electrodes, specifically comprising the following steps:

[0008] S1, to contain Cu 2+ , Fe 3+ ,PO 4 3- Add a pH regulator to the acidic solution to adjust the pH of the solution to between 1.5 and 2.5;

[0009] S2, add iron powder and the copper powder and iron powder mixture obtained by secondary copper removal to the solution, and the iron powder and Cu in the solution 2+ , Fe 3+ Oxidation-reduction reaction occurs to obtain Cu powder and Fe 2+ ;

[0010] S3, after the first solid-liquid separation, copper powder and a primary copper removal liquid are obtained, a certain amount of iron powder is added to the primary copper removal liquid again, and a secondary copper removal is performed to obtain a copper powder and iron powder mixture and a secondary copper removal liquid;

[0011] S4, adding the mixture of copper powder and iron powder as a reducing iron source to the pre-copper removal solution to fully utilize the iron powder to obtain copper powder;

[0012] S5, washing the obtained copper powder with water to obtain pure copper powder, and returning the washing water to the acid leaching copper removal pre-liquid.

[0013] Preferably, the acidic solution in step S1 is allowed to contain other metal cation impurities.

[0014] Preferably, the metal cation impurity is Al 3+ and Fe 3+ .

[0015] Preferably, the acidic solution is a sulfuric acid leaching solution of mixed black powder of positive and negative electrodes of waste lithium iron phosphate batteries.

[0016] Preferably, the amount of copper-iron powder added in step S3 is 0.5-1.0 times the molar ratio of copper to iron, and the reaction is stirred for 0.5-1h.

[0017] Preferably, the temperature of the copper removal process in step S3 is room temperature.

[0018] Preferably, the amount of the secondary copper-removing iron powder added in step S3 is 0.1-0.6 times the molar ratio of copper to iron. The reaction is stirred for 0.5-1h.

[0019] Preferably, the copper removal process in step S3 is carried out under the protection of an inert atmosphere.

[0020] (III) Beneficial effects

[0021] The present invention provides a method for economically removing copper from waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching liquid. Compared with the prior art, it has the following beneficial effects:

[0022] (1) The method for economically removing copper from the waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching liquid has a significant copper removal effect. During the production process of the waste lithium iron phosphate positive and negative electrode mixed black powder, part of the negative electrode sheet will be ground into powder and mixed into it. During the acid leaching, all the copper elements enter the acid leaching liquid, so that the copper content in the acid leaching liquid reaches 1.5-4g / l. After the segmented copper removal process, the copper content can be reduced to below 5ppm.

[0023] (2) The method of economically removing copper from the waste lithium iron phosphate positive and negative electrodes mixed with black powder acid leaching liquid can purify the copper powder.

[0024] (3) The method of economically removing copper from the mixed black powder acid leaching liquid of the waste lithium iron phosphate positive and negative electrodes has a low copper removal cost. The common copper removal methods currently use a one-step method to remove copper, which either uses a large amount of copper removal agent or results in a high loss of metal. The segmented copper removal of the present invention solves this problem. The copper is removed once, and an insufficient amount of iron powder is added to remove most of the copper element, leaving a small amount of copper element. Pure copper powder and a primary copper removal liquid are obtained by filtration. The primary copper removal liquid is then subjected to a secondary copper removal, and excess iron powder is added. The pure purified liquid and iron-copper slag are filtered out. This part of the iron-copper slag is returned to the front end for a primary copper removal, so that the iron powder is fully utilized. This greatly reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1 The embodiment of the present invention provides a technical solution: a method for economically removing copper from a mixed black powder acid leaching solution of waste lithium iron phosphate positive and negative electrodes, specifically including the following embodiments:

[0028] Example:

[0029] 1. Add a pH regulator to the acid leaching solution of waste lithium iron phosphate black powder. The composition of the acid leaching solution is shown in Table 1 to make the solution pH between 1.5 and 2.5.

[0030]

[0031]

[0032] Table 1: Composition of waste lithium iron phosphate black powder acid leaching solution

[0033] 2. At the pH value described in step 1, add iron powder and the copper powder and iron powder mixture obtained by secondary copper removal in proportion, and stir the reaction under an inert atmosphere for 0.5-1h.

[0034] 3. After the reaction is completed, the first solid-liquid separation is carried out to obtain a primary copper removal liquid and copper powder, and the components of the copper powder and the primary copper removal liquid are analyzed.

[0035]

[0036] Table 2: Composition of primary copper removal solution

[0037] Copper powder composition analysis: Cu ≥ 95%; Fe ≤ 3%.

[0038] 4. Add iron powder to the primary copper removal solution according to the proportion and stir the reaction under an inert atmosphere for 0.5-1h.

[0039] 5. After the reaction in step 4 is completed, a second solid-liquid separation is performed to obtain a secondary copper removal liquid, which is the final qualified purified liquid, a mixture of copper powder and iron powder.

[0040]

[0041]

[0042] Table 3: Composition of secondary copper removal solution

[0043] Comparative Example: Add an excess of copper removal agent to the acid leaching material in Table 1 at one time, and obtain the copper removal solution and copper slag after solid-liquid separation. Analyze the elemental composition of the copper removal solution and copper slag.

[0044] The copper content of the waste lithium iron phosphate black powder acid leaching liquid can be reduced to about 40ppm after the first copper removal, and the copper content can be reduced to below 5ppm after the second copper removal. A small amount of the pricing metal elements (lithium iron phosphorus copper, etc.) enter the copper removal slag in the form of a solution, which can be recovered by subsequent water washing. The loss of pricing metal elements is small, the copper removal cost is reduced, and the copper removal effect is significant. Compared with the control example, the copper slag obtained by the patent method is purer and the copper removal effect is more thorough.

[0045] Table 4: Composition of one-step copper removal solution

[0046] g / l Li Fe P Al Cu Ni Co Mn 1# Copper removal liquid 6.74 52.06 28.6 2.13 0.01 1.23 0.66 1.08 2# copper removal liquid 7.6 56.22 29.6 1.88 0.02 0.2 0.12 0.19 3# Copper removal liquid 9.81 67.15 36.9 2.76 0.01 0.13 0.12 0.16

[0047] Copper slag composition: Cu≈80%, Fe≈16%.

[0048] In summary, the copper removal effect of the present invention is significant. In the production process of waste lithium iron phosphate positive and negative electrode mixed black powder, part of the negative electrode sheet will be ground into powder and mixed into it. During acid leaching, all the copper elements enter the acid leaching solution, so that the copper content in the acid leaching solution reaches 1.5-4g / l. After the segmented copper removal process, the copper content can be reduced to below 5ppm, and the purified copper powder is pure. At present, the common copper removal method generally adopts a one-step method to remove copper, either using a large amount of copper removal agent or the loss of the valuation metal is high. The segmented copper removal of the present invention just solves this problem. In the first copper removal, the insufficient amount of iron powder is added to remove most of the copper element, and a small amount of copper element remains. What is filtered is pure copper powder and a primary copper removal liquid. The primary copper removal liquid is then subjected to secondary copper removal, and excess iron powder is added to filter to obtain pure purification liquid and iron-copper slag. This part of the iron-copper slag returns to the front end for a copper removal, so that the iron powder is fully utilized. Greatly reduce costs.

[0049] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0050] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0051] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for economically removing copper from waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching solution, characterized in that: The specific steps include: S1, to contain Cu 2+ , Fe 3+ PO4 3- Add a pH regulator to the acidic solution to adjust the pH of the solution to between 1.5 and 2.5; S2, add iron powder and the copper powder and iron powder mixture obtained by secondary copper removal to the solution, and the iron powder and Cu in the solution 2+ , Fe 3+ Oxidation-reduction reaction occurs to obtain Cu powder and Fe 2+ ; S3, after the first solid-liquid separation, copper powder and a primary copper removal liquid are obtained, a certain amount of iron powder is added to the primary copper removal liquid again, and a secondary copper removal is performed to obtain a copper powder and iron powder mixture and a secondary copper removal liquid; S4, adding the mixture of copper powder and iron powder as a reducing iron source to the pre-copper removal solution to fully utilize the iron powder to obtain copper powder; S5, washing the obtained copper powder with water to obtain pure copper powder, and returning the washing water to the acid leaching copper removal pre-liquid.

2. The method for economically removing copper from a mixed black powder acid leaching solution of waste lithium iron phosphate positive and negative electrodes according to claim 1, characterized in that: The acidic solution in step S1 is allowed to contain other metal cation impurities.

3. The method for economically removing copper from a waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching solution according to claim 2, characterized in that: The metal cation impurity is Al 3+ and Fe 3+ .

4. The method for economically removing copper from a waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching solution according to claim 2, characterized in that: The acid solution is a sulfuric acid leaching solution of the positive and negative electrodes of waste lithium iron phosphate batteries mixed with black powder.

5. The method for economically removing copper from a waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching solution according to any one of claims 1 to 4, characterized in that: In the step S3, the amount of copper-iron powder added in one step is 0.5-1.0 times the molar ratio of copper to iron, and the reaction is stirred for 0.5-1h.

6. A method for economically removing copper from a waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching solution according to any one of claims 1 to 4, characterized in that: The temperature of the copper removal process in step S3 is room temperature.

7. A method for economically removing copper from a waste lithium iron phosphate positive and negative electrode mixed black powder acid leaching solution according to any one of claims 1 to 4, characterized in that: The amount of the iron powder for secondary copper removal in step S3 is 0.1-0.6 times the molar ratio of copper to iron. The reaction is stirred for 0.5-1h.

8. The method for economically removing copper from a mixed black powder acid leaching solution of waste lithium iron phosphate positive and negative electrodes according to claim 1, characterized in that: The copper removal process in step S3 is carried out under the protection of an inert atmosphere.

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