Methods for recovering valuable metals

Abstract

The present invention provides a method for recovering high-purity manganese, cobalt, or nickel from a liquid containing manganese, cobalt, or nickel without crystallization. [Solution] A method for recovering valuable metals includes an extraction step of extracting the valuable metals from a liquid containing the valuable metals using an organic solvent, a back-extraction step of back-extracting the extract obtained through the extraction step to obtain a back-extract containing the valuable metals, and a purification step of removing at least one selected from the group consisting of metals other than the valuable metals and phosphorus from the back-extract, wherein the valuable metals are at least one selected from the group consisting of manganese, cobalt, and nickel.

Description

Technical Field

[0001] The present invention relates to a method for recovering valuable metals.

Background Art

[0002] In recent years, with the spread of lithium-ion batteries, methods for recovering valuable metals such as cobalt, nickel, manganese, and lithium from waste lithium-ion batteries and reusing them as materials for lithium-ion batteries have been studied.

[0003] Conventionally, when recovering the valuable metals from the waste lithium-ion batteries, the waste lithium-ion batteries are subjected to heat treatment (roasting), or the cobalt, nickel, manganese, and lithium are separately separated and purified by a wet process from the powder containing the valuable metals obtained by pulverizing, classifying, etc. without subjecting to heat treatment (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional method for recovering valuable metals from waste lithium-ion batteries, manganese, cobalt, nickel, and lithium were each recovered individually. Each of the cobalt, nickel, and manganese recovered using an organic solvent as an extractant was crystallized, and the obtained metal salt was dissolved in water.

[0006] However, crystallization requires a large amount of energy. In recent years, from the viewpoint of energy conservation and reduction of carbon dioxide emissions, there has been a strong demand for a method to recover high-purity manganese, cobalt, or nickel from a liquid containing manganese, cobalt, or nickel without undergoing crystallization. The problem that this invention aims to solve is to provide a method for recovering high-purity manganese, cobalt, or nickel from a liquid containing manganese, cobalt, or nickel without undergoing crystallization. [Means for solving the problem]

[0007] In view of the above-mentioned problems, the inventors conducted extensive research and found that it is possible to remove at least one metal selected from the group consisting of metals other than these valuable metals and phosphorus from a liquid containing manganese, cobalt, or nickel. The present invention was completed based on these findings.

[0008] The present invention relates to a method for recovering valuable metals, comprising: an extraction step of extracting the valuable metal from a liquid containing the valuable metal using an organic solvent; a back-extraction step of back-extracting the extract obtained through the extraction step to obtain a back-extract containing the valuable metal; and a purification step of removing at least one selected from the group consisting of metals other than the valuable metal and phosphorus from the back-extract, wherein the valuable metal is at least one selected from the group consisting of manganese, cobalt, and nickel. The purification step preferably includes a phosphorus removal step in which the back extract containing the valuable metal, to which aluminum has been added, is heated and neutralized to perform solid-liquid separation and obtain an aqueous solution from which phosphorus has been removed. The purification step preferably includes an iron removal step, in which an oxidizing agent is added to the back extract to oxidize the iron, followed by neutralization and solid-liquid separation to obtain an aqueous solution from which the iron has been removed. The purification step preferably includes a sulfide removal step of mixing the back extract with the sulfide to generate a sulfide of a metal other than the valuable metal, and removing the sulfide, wherein the metal other than the valuable metal includes at least one selected from the group consisting of lead, cadmium, and zinc. The method for recovering the valuable metal preferably further includes a scrubbing step in which at least one selected from the group consisting of a first scrubbing in which the extract obtained through the extraction step is mixed with a mineral acid, and a second scrubbing in which the extract obtained through the extraction step is mixed with an aqueous solution of the mineral salt of the valuable metal.

[0009] The method for recovering the valuable metals preferably includes a dissolution step of dissolving active material powder obtained by pre-treating waste lithium-ion batteries in a mineral acid to obtain an acid solution, a neutralization step of neutralizing the acid solution with an alkali, and a membrane electrolysis step of performing membrane electrolysis on the first lithium salt aqueous solution obtained through the extraction step using an ion exchange membrane to obtain a lithium hydroxide aqueous solution, an acid, and a second lithium salt aqueous solution that is more dilute than the first lithium salt aqueous solution, wherein the lithium hydroxide aqueous solution obtained in the membrane electrolysis step is reused in at least one selected from the group consisting of the neutralization step and the extraction step, and the acid obtained in the membrane electrolysis step is reused as the mineral acid used in the dissolution step. [Effects of the Invention]

[0010] The present invention provides a method for recovering valuable metals by recovering high-purity manganese, cobalt, or nickel from a liquid containing manganese, cobalt, or nickel without crystallization. [Brief explanation of the drawing]

[0011] [Figure 1] An explanatory diagram showing the configuration of one embodiment of the method for recovering valuable metals according to the present invention. [Modes for carrying out the invention]

[0012] The present invention will be described in more detail. Unless otherwise specified, the numerical range "X~Y" represents the range from X or greater to Y or less, including both values ​​at either end. Furthermore, when a numerical range is indicated, the upper and lower limits may be combined as appropriate, and the resulting numerical range will also be disclosed. Furthermore, identical elements are denoted by the same reference numeral in the drawings, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are exaggerated for explanatory purposes and may differ from the actual ratios.

[0013] In this invention, "waste lithium-ion battery" refers to a used lithium-ion battery whose lifespan as a battery product has been exhausted, a lithium-ion battery discarded as a defective product during the manufacturing process, and residual positive electrode material, negative electrode material, etc., used in the manufacturing process. Furthermore, the powder containing positive and negative electrodes obtained from the said waste lithium-ion battery, as well as crushed, coarse, and fine fragments of positive electrode plates, etc., are referred to as the active material powder. In addition, "impurity" refers to metals contained in the active material powder that do not require recovery.

[0014] One embodiment of the valuable metal recovery method of the present invention will be described in more detail with reference to the attached drawings.

[0015] <Extraction Steps> The present invention provides a method for recovering valuable metals, which includes an extraction step (STEP 2 in Figure 1) of extracting the valuable metal from a liquid containing the valuable metal using an organic solvent. The valuable metal is manganese, cobalt, or nickel. The liquid containing the valuable metal and lithium may be obtained, for example, by performing a dissolution step and a neutralization step described later.

[0016] The liquid containing the valuable metal and the organic solvent are mixed in the extraction step to obtain at least one extract containing each of the valuable metals. For example, each of the 3 valuable metals is extracted by each of the 3 extraction operations. The order in which each of the valuable metals is extracted is set as appropriate. The extractant contained in the organic solvent used in each of the extraction operations is not limited to a specific compound. Examples of the extractant include compounds described in International Publication No. 2023 / 195533.

[0017] The organic solvent may contain a diluent, and the concentration of the extractant may be adjusted as appropriate. Examples of the diluent include hydrocarbons such as kerosene and decane. The concentration of the extractant in the organic solvent is preferably in the range of 10 to 40% by mass.

[0018] The present invention's method for recovering valuable metals may use active material powder 1 as a starting material. The active material powder 1 will now be described. If the waste lithium-ion battery is a used lithium-ion battery whose lifespan as a battery product has been exhausted, or a lithium-ion battery that has been discarded as a defective product during the manufacturing process, first, a discharge treatment is performed. Various highly safe methods, such as resistive discharge, can be used for the discharge treatment. After discharging all residual charge, an opening is formed in the housing of the waste lithium-ion battery, and then, for example, the battery is heat-treated (roasted) at a temperature in the range of 100 to 800°C, or, without heat treatment, it is crushed with a crusher such as a hammer mill or jaw crusher, and the housing, current collector, etc. that constitute the waste lithium-ion battery are removed by sieving (classification) to obtain the active material powder. Alternatively, the waste lithium-ion battery after the discharge treatment may be crushed with the crusher, the housing, current collector, etc. are removed by sieving, and then the active material powder 1 may be obtained by heat treatment at the temperature in the range mentioned above.

[0019] When the used lithium-ion battery is the remaining positive electrode material or the like used for commercialization in the manufacturing process, the discharge treatment and the formation of the opening are not performed, and after heat treatment at the temperature within the range, or without heat treatment, it may be pulverized by the pulverizer, and the current collector and the like are removed by sieving to obtain the active material powder. Further, the used lithium-ion battery may be pulverized by the pulverizer, the current collector and the like are removed by sieving, and then heat treatment is performed at the temperature within the range, or the active material powder 1 is obtained without heat treatment.

[0020] <Dissolution step> The method for recovering valuable metals of the present invention may include a dissolution step (STEP 1 in FIG. 1) of dissolving the active material powder 1 in a mineral acid to obtain an acid dissolution solution. The active material powder 1 may contain metals such as manganese, cobalt, nickel, phosphorus, iron, copper, lead, cadmium, and zinc in addition to lithium. The mineral acid preferably contains at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably contains hydrochloric acid, and still more preferably is hydrochloric acid.

[0021] <Neutralization step> The method for recovering valuable metals of the present invention may include a neutralization step (STEP 2 in FIG. 1) in which the acid dissolution solution obtained through the dissolution step is neutralized with an alkali. The alkali may be added in at least one form selected from the group consisting of an aqueous solution and a solid state. The alkali preferably contains at least one selected from the group consisting of alkali metal hydroxides and ammonia. Further, the alkali metal constituting the alkali metal hydroxide preferably contains at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and francium, more preferably contains lithium, sodium, and potassium, still more preferably is lithium, sodium, or potassium, and particularly preferably is lithium.

[0022] <Back extraction step> The present invention provides a method for recovering valuable metals, which includes a back-extraction step (STEP 4 in Figure 1) in which the extract obtained through the extraction step is back-extracted to obtain a back-extract containing the valuable metal. The extract and a mineral acid are mixed in the back-extraction step. The mineral acid is the same as the mineral acid used in the dissolution step. Back-extraction is performed on at least one of the extracts obtained through each of the extraction operations (extract containing manganese, extract containing cobalt, and extract containing nickel).

[0023] <Purification Step> The present invention's method for recovering valuable metals includes a purification step (STEP 5 in Figure 1) in which at least one selected from the group consisting of metals other than valuable metals and phosphorus is removed from the back extract. The purification step is performed on at least one of each of the extracts obtained through each of the extraction operations. Since impurities are removed by the purification step, the present invention's method for recovering valuable metals can recover high-purity manganese, cobalt, or nickel from a liquid containing manganese, cobalt, or nickel without crystallization.

[0024] (Phosphorus removal step) The purification step may include a phosphorus removal step in which aluminum is added to the back extract containing the valuable metal, and the back extract is heated and neutralized to perform solid-liquid separation and obtain an aqueous solution from which phosphorus has been removed. The heating temperature of the back extract containing the valuable metal is preferably in the range of 60 to 70°C. The neutralizing agent used for neutralizing the manganese-containing back extract in the phosphorus removal step preferably comprises at least one selected from the group consisting of metallic manganese and manganese carbonate, more preferably at least one selected from the group consisting of metallic manganese and manganese carbonate, and even more preferably metallic manganese or manganese carbonate. The neutralizing agent used for neutralizing the cobalt-containing back extract in the phosphorus removal step preferably comprises at least one selected from the group consisting of metallic cobalt and cobalt hydroxide, more preferably at least one selected from the group consisting of metallic cobalt and cobalt hydroxide, and even more preferably metallic cobalt or cobalt hydroxide. The neutralizing agent used to neutralize the nickel-containing back extract in the phosphorus removal step preferably comprises at least one selected from the group consisting of metallic nickel and nickel hydroxide, more preferably at least one selected from the group consisting of metallic nickel and nickel hydroxide, and even more preferably metallic nickel or nickel hydroxide.

[0025] (Iron removal step) The purification step may include an iron removal step, in which an oxidizing agent is added to the back extract to oxidize the iron, followed by neutralization and solid-liquid separation to obtain an aqueous solution from which the iron has been removed. The oxidizing agent is not limited to a specific compound, but is, for example, hydrogen peroxide. The neutralizing agent used for neutralization in the iron removal step is the same as the neutralizing agent used for neutralization in the phosphorus removal step.

[0026] (Sulfide removal step) The purification step may include a sulfide removal step in which the back extract is mixed with the sulfide to generate a sulfide of a metal other than the valuable metal, and the sulfide is removed. The metal other than the valuable metal includes at least one selected from the group consisting of copper, lead, cadmium, and zinc. The sulfide is not limited to a specific sulfide. The sulfide may include at least one selected from the group consisting of hydrogen sulfide, sodium hydrosulfide, and sodium sulfide, preferably hydrogen sulfide, and more preferably hydrogen sulfide.

[0027] <Scrubbing Steps> The method for recovering valuable metals according to the present invention may include a scrubbing step (STEP 6 in Figure 1) in which at least one selected from the group consisting of a first scrubbing, in which the extract obtained through the extraction step is mixed with a mineral acid, and a second scrubbing, in which the extract obtained through the extraction step is mixed with an aqueous solution of the mineral salt of the valuable metal. The first scrubbing and the second scrubbing are appropriately selected depending on the amount and form of lithium, impurities, etc., present in the acid solution. The first scrubbing can scrub off a larger amount of impurities than the second scrubbing. The scrubbing step is performed on at least one of the extracts obtained through each of the extraction operations. At least one selected from the group consisting of chloride ions, sulfate ions, and nitrate ions is removed in the scrubbing step.

[0028] The mineral acid used in the first scrubbing may include at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, preferably hydrochloric acid, and more preferably hydrochloric acid. In the extraction step, depending on the extraction rate, lithium and other valuable metals not intended for extraction may be extracted along with the valuable metal. For example, when extracting cobalt, lithium and nickel are also extracted. The first scrubbing can remove lithium and other valuable metals not intended for extraction.

[0029] The mineral acid contained in the aqueous solution of the valuable metal mineral salt used in the second scrubbing preferably contains at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably sulfuric acid, and even more preferably sulfuric acid. Furthermore, the concentration of the valuable metal mineral salt contained in the aqueous solution of the valuable metal mineral salt is appropriately set within a range below the saturation solubility of the valuable metal mineral salt. In the first scrubbing, depending on the extraction rate, valuable metals other than lithium and the valuable metal may be removed. For example, when scrubbing with hydrochloric acid is performed on an extract from which cobalt has been extracted, in order to scrub lithium and nickel, the cobalt that was extracted together is also removed, so the recovery rate of cobalt decreases. On the other hand, in the second scrubbing, lithium and valuable metals that are not the target of extraction are exchanged for valuable metals in the valuable metal mineral salt. Therefore, lithium and valuable metals that are not the target of extraction can be removed without reducing the recovery rate of the extracted valuable metal.

[0030] Furthermore, in the extraction step, if the difference in specific gravity between the organic solvent and the aqueous phase is small, there is a problem in that the oil-water separation performance deteriorates. This poor oil-water separation performance is particularly problematic when the mineral acid used in the dissolution step and the back-extraction step are different. Impurities originating from the mineral acid in the dissolution step are mixed into the back-extraction step, leading to a decrease in quality. For example, if hydrochloric acid is used in the dissolution step, chloride ions are mixed into the back-extract. This can be solved by performing scrubbing with a mineral acid different from the one used in the dissolution step, but even here, if the oil-water separation performance is poor during scrubbing, droplets of the scrubbed aqueous phase containing impurities are mixed into the organic solvent, and the impurities cannot be sufficiently removed. However, when an aqueous mineral acid solution is used, as in the second scrubbing, the difference in specific gravity becomes larger, improving the oil-water separation performance and reducing the amount of aqueous phase droplets mixed into the organic solvent. Therefore, a high-quality back-extract with reduced impurity contamination can be obtained.

[0031] A second back-extraction step may be performed in which the oil phase obtained in the first and second scrubbing steps is mixed with a mineral acid. The mineral acid used in the second back-extraction step preferably comprises at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably sulfuric acid, and even more preferably sulfuric acid.

[0032] The scrubbing solutions obtained in the first and second scrubbing steps may or may not be returned to the extraction step. If the scrubbing solutions are not returned to the extraction step, there is no need to increase the size of the apparatus after the extraction step.

[0033] <Membrane electrolysis step> The method for recovering valuable metals according to the present invention may include a membrane electrolysis step (STEP 7 in Figure 1) in which the lithium-containing solution obtained through the extraction step is subjected to membrane electrolysis. The membrane electrolysis step may be carried out, for example, by the method described in International Publication No. 2023 / 195533. The aqueous lithium hydroxide solution obtained in the membrane electrolysis step may be reused in at least one selected from the group consisting of the neutralization step and the extraction step. The acid obtained in the membrane electrolysis step may be reused as the mineral acid used in the dissolution step. [Explanation of Symbols]

[0034] 1...Active material powder.

Claims

1. A method for recovering valuable metals, An extraction step of extracting a valuable metal from a liquid containing the valuable metal using an organic solvent. A back-extraction step is performed by back-extracting the extract obtained through the extraction step to obtain a back-extract containing the valuable metal, and The process includes a purification step of removing at least one selected from the group consisting of metals other than the valuable metal and phosphorus from the back extract. A method for recovering a valuable metal, wherein the valuable metal is at least one selected from the group consisting of manganese, cobalt, and nickel.

2. A method for recovering a valuable metal according to claim 1, wherein the purification step includes a phosphorus removal step of heating and neutralizing the back extract containing the valuable metal to which aluminum has been added, thereby performing solid-liquid separation to obtain an aqueous solution from which phosphorus has been removed.

3. A method for recovering valuable metals according to claim 1, wherein the purification step includes an iron removal step, in which an oxidizing agent is added to the back extract to oxidize the iron, then neutralized and solid-liquid separated to obtain an aqueous solution from which the iron has been removed.

4. A method for recovering a valuable metal according to claim 1, wherein the purification step includes a sulfide removal step of mixing the back extract with a sulfide to generate a sulfide of a metal other than the valuable metal and removing the sulfide, wherein the metal other than the valuable metal includes at least one selected from the group consisting of lead, cadmium, and zinc.

5. A method for recovering valuable metals according to claim 1, further comprising a scrubbing step of performing at least one selected from the group consisting of a first scrubbing of mixing the extract obtained through the extraction step with a mineral acid, and a second scrubbing of mixing the extract obtained through the extraction step with an aqueous solution of the mineral salt of the valuable metal.

6. A method for recovering valuable metals according to any one of claims 1 to 5, Dissolution step: Dissolve the active material powder obtained by pre-treating waste lithium-ion batteries in mineral acid to obtain an acid solution. A neutralization step in which the acid solution is neutralized with alkali, The method further includes a membrane electrolysis step in which the first lithium salt aqueous solution obtained through the extraction step is subjected to membrane electrolysis using an ion exchange membrane to obtain a lithium hydroxide aqueous solution, an acid, and a second lithium salt aqueous solution that is more dilute than the first lithium salt aqueous solution. The aqueous lithium hydroxide solution obtained in the membrane electrolysis step is reused in at least one of the steps selected from the group consisting of the neutralization step and the extraction step. A method for recovering valuable metals, wherein the acid obtained in the film electrolysis step is reused as the mineral acid used in the dissolution step.

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