Valuable metal recovery method

Abstract

The present invention provides a method for recovering a high-purity valuable metal from a liquid containing lithium and at least one valuable metal selected from the group consisting of cobalt, nickel, and manganese. This valuable metal recovery method comprises: a first extraction step for extracting the valuable metal from a liquid containing the valuable metal and lithium, by using a first organic solvent containing an extractant; a scrubbing step for performing at least one selected from the group consisting of first scrubbing in which the extract obtained through the first extraction step is mixed with a mineral acid, and second scrubbing in which the extract obtained through the first extraction step is mixed with a mineral acid salt aqueous solution of the valuable metal; and a lithium recovery step for recovering lithium in a post-scrubbing aqueous phase obtained through the scrubbing step. The valuable metal is aluminum, cobalt, nickel, or manganese.

Description

Valuable metal recovery methods

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

[0002] In recent years, with the widespread use of lithium ion batteries, methods have been investigated for recovering valuable metals such as cobalt, nickel, manganese, and lithium from discarded lithium ion batteries and reusing them as materials for the lithium ion batteries.

[0003] Conventionally, when recovering the valuable metals from the waste lithium-ion batteries, the waste lithium-ion batteries are subjected to a heat treatment (roasting), or the valuable metals are obtained by pulverizing and classifying the waste lithium-ion batteries without subjecting them to a heat treatment, and then cobalt, nickel, manganese, and lithium are each separated and refined by a wet process (see, for example, Patent Documents 1 to 4).

[0004] Japanese Patent No. 7060899 Japanese Patent Application Laid-Open No. 2023-100197 International Publication No. 2023 / 054667 International Publication No. 2023 / 054621

[0005] The cobalt, nickel, and manganese recovered in the conventional wet process each contain impurities such as lithium, magnesium, chloride ions, etc. In recent years, there has been a demand for further improvement in the purity of the cobalt, nickel, and manganese recovered from waste lithium-ion batteries.

[0006] The problem to be solved by the present invention is to provide a method for recovering high-purity valuable metals from a solution containing at least one valuable metal selected from the group consisting of cobalt, nickel, and manganese, and lithium.

[0007] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that a method for recovering valuable metals with high purity includes a first extraction step of extracting the valuable metals from a solution containing at least one valuable metal selected from the group consisting of cobalt, nickel, and manganese, and lithium, using a first organic solvent containing an extractant, a scrubbing step of scrubbing the extract obtained through the extraction step, and a lithium recovery step of recovering lithium from the scrubbing solution obtained through the scrubbing step.The present invention was completed based on these findings.

[0008] The present invention relates to a method for recovering valuable metals, the method comprising: a first extraction step in which the valuable metal is extracted from a solution containing the valuable metal and lithium using a first organic solvent containing an extractant; a first scrubbing step in which the extract obtained in the first extraction step is mixed with a mineral acid; and a second scrubbing step in which the extract obtained in the first extraction step is mixed with an aqueous solution of a mineral acid salt of the valuable metal; and a lithium recovery step in which lithium is recovered from the aqueous phase obtained after scrubbing. The lithium recovery step preferably includes a second extraction step in which the aqueous phase obtained after scrubbing is mixed with a second organic solvent containing a carboxylic acid extractant to obtain a lithium-containing extraction residue. The mineral acid in the aqueous solution of a valuable metal mineral acid salt preferably includes at least one acid selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid. The valuable metal recovery method preferably further includes a dissolving step of dissolving active material powder obtained by pretreating waste lithium-ion batteries in a mineral acid to obtain an acid solution, and a neutralizing step of neutralizing the acid solution with an alkali. The lithium recovery step preferably includes a concentration step of concentrating lithium in the extraction residue. The lithium recovery step preferably includes a second impurity removal step of removing impurities from the extraction residue.

[0009] The method for recovering valuable metals of the present invention provides a method for recovering valuable metals with high purity.

[0010] 1 is an explanatory diagram showing the configuration of one embodiment of a valuable metal recovery method of the present invention.

[0011] The present invention will be described in further detail. Unless otherwise specified, the "to" in a numerical range indicates a range from above to below, and both end values ​​are included. Furthermore, when a numerical range is indicated, the upper and lower limits can be appropriately combined, and the resulting numerical range is also considered to be disclosed.

[0012] In the present invention, "waste lithium-ion batteries" refers to used lithium-ion batteries that have reached the end of their life as battery products, lithium-ion batteries discarded as defective products during the manufacturing process, and residual positive and negative electrode materials used in the manufacturing process. Furthermore, active material powder refers to powders containing positive and negative electrodes obtained from the waste lithium-ion batteries, as well as crushed, roughly crushed, and finely fragmented positive electrode plates. Furthermore, "impurities" refers to metals contained in the active material powder that do not require recovery.

[0013] One embodiment of the valuable metal recovery method of the present invention will be described in more detail with reference to the accompanying drawings. <First Extraction Step> The valuable metal recovery method of the present invention includes a first extraction step in which valuable metals are extracted from a solution containing valuable metals and lithium using a first organic solvent containing an extractant (STEP 2 in Figure 1). The valuable metals are aluminum, cobalt, nickel, or manganese. The solution containing valuable metals and lithium is obtained, for example, by carrying out a dissolution step and a first impurity removal step, which will be described later.

[0014] The liquid containing the valuable metals and lithium and the first organic solvent are mixed in the first extraction step to obtain an extract 2 containing the valuable metals and an extraction residue 4 containing lithium. The extractant contained in the first organic solvent is not limited to a specific compound.

[0015] When the liquid containing valuable metals and lithium contains at least two selected from the group consisting of cobalt, nickel, and manganese, the first extraction step includes two or more extraction steps, and examples of the extractant used in each of the two or more extraction steps include compounds described in WO 2023 / 195533.

[0016] The first organic solvent may contain a diluent, and the concentration of the extractant may be appropriately adjusted. Examples of the diluent include hydrocarbons such as kerosene and decane, and third petroleum products. A typical example of the third petroleum product is MC531 manufactured by Tobu Chemical Co., Ltd. The concentration of the extractant in the organic solvent is preferably in the range of 10 to 40% by mass.

[0017] The valuable metal recovery method of the present invention may use active material powder 1 as a starting material. The active material powder 1 will now be described. When the used lithium-ion batteries are used lithium-ion batteries whose battery life as a battery product has expired or lithium-ion batteries discarded as defective products during the manufacturing process, they are first subjected to a discharge treatment. Various highly safe methods, such as resistance discharge, can be used for the discharge treatment. After discharging all remaining charge, openings are formed in the casings of the used lithium-ion batteries. The batteries are then heat-treated (roasted) at a temperature ranging from 100 to 800°C, or the batteries are pulverized in a pulverizer such as a hammer mill or jaw crusher without being heat-treated. The casings, current collectors, and other components of the used lithium-ion batteries are removed by sieving (classification), thereby obtaining the active material powder. Alternatively, the used lithium-ion batteries after the discharge treatment may be pulverized in the pulverizer, the casings, current collectors, and other components are removed by sieving, and the active material powder 1 is obtained by heat-treating the batteries at a temperature within the range.

[0018] When the used lithium ion batteries are residual positive electrode materials or the like used in commercialization in a manufacturing process, the active material powder may be obtained by pulverizing the used lithium ion batteries in the pulverizer after heat treatment at a temperature in the above range or without heat treatment without performing the discharge treatment and forming openings, and removing the current collectors and the like by sieving.Furthermore, the used lithium ion batteries may be pulverized in the pulverizer, and after removing the current collectors and the like by sieving, heat treatment at a temperature in the above range or without heat treatment to obtain the active material powder 1.

[0019] <Dissolving Step> The valuable metal recovery method of the present invention may include a dissolving step (STEP 1 in FIG. 1 ) of dissolving the active material powder 1 in a mineral acid to obtain an acid solution. The active material powder 1 may contain valuable metals such as aluminum, manganese, cobalt, and nickel in addition to lithium. The mineral acid preferably includes at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably includes hydrochloric acid, and even more preferably is hydrochloric acid.

[0020] <First Impurity Removal Step> The valuable metal recovery method of the present invention may include an impurity removal step of removing impurities from the acid solution.

[0021] (First Solid-Liquid Separation Step) The first impurity removal step may include a first solid-liquid separation step in which carbon powder is removed from the acid solution.

[0022] (Step of Removing Valuable Metals Other Than Lithium, Cobalt, Manganese, and Nickel) The first impurity removal step may, if necessary, include a step of extracting valuable metals other than lithium, cobalt, manganese, and nickel, in which the acid solution obtained by subjecting the first solid-liquid separation step is mixed with an organic solvent containing at least one selected from the group consisting of a compound represented by the following formula (1), a phosphonic acid ester, a phosphoric acid ester, phosphinic acid, methyl isobutyl ketone, and trioctylamine, and at least one valuable metal selected from the group consisting of (1) transition metals other than manganese, cobalt, and nickel, (2) calcium, and (3) aluminum.

[0023]

[0024] In the formula (1), R １ , R ２ each independently represents a hydrocarbon group having 6 to 20 carbon atoms.

[0025] (Neutralization Step) The first impurity removal step may optionally include a neutralization step in which the acid solution obtained by the first solid-liquid separation step and the valuable metals other than lithium, cobalt, manganese, and nickel removal step is neutralized with an alkali. Aluminum hydroxide may precipitate in the neutralization step, and fluorine may co-precipitate with the aluminum hydroxide. The alkali may be added in at least one form selected from the group consisting of an aqueous solution and a solid. The alkali preferably includes at least one selected from the group consisting of an alkali metal hydroxide and ammonia. The alkali metal constituting the alkali metal hydroxide preferably includes at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and francium, more preferably lithium, sodium, or potassium, even more preferably lithium, sodium, or potassium, and particularly preferably lithium.

[0026] (Second solid-liquid separation step) The first impurity removal step may include a second solid-liquid separation step in which aluminum hydroxide is separated from the acid-dissolved solution obtained through the hydrosulfiding step. If fluorine is adsorbed to the aluminum hydroxide separated in the second solid-liquid separation step, the fluorine is also separated together with the aluminum hydroxide.

[0027] <Scrubbing Step> The valuable metal recovery method of the present invention includes a scrubbing step (STEP 3 in FIG. 1 ) that performs at least one scrubbing step selected from the group consisting of a first scrubbing step in which the extract 2 obtained through the first extraction step is mixed with a mineral acid, and a second scrubbing step in which the extract 2 obtained through the first extraction step is mixed with an aqueous solution of a mineral acid salt of the valuable metal. The first scrubbing step and the second scrubbing step are each appropriately selected depending on the amount and form of impurities, such as lithium and magnesium, present in the liquid containing the valuable metal and lithium. The first scrubbing step can scrub a larger amount of impurities than the second scrubbing step. Note that when the liquid containing the valuable metal and lithium contains at least two elements selected from the group consisting of aluminum, cobalt, nickel, and manganese, the scrubbing step is performed on each of the extracts obtained through the two or more extraction steps.

[0028] The mineral acid used in the first scrubbing step may include at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, preferably hydrochloric acid, more preferably hydrochloric acid. In the first extraction step, depending on the extraction rate, lithium and other valuable metals may be extracted along with the valuable metals. For example, when cobalt is extracted, lithium and nickel are also extracted. The first scrubbing step can remove lithium and other valuable metals, improving the quality of the valuable metal salt crystallization product obtained in the crystallization step described below.

[0029] When the first extraction step includes two or more extraction steps, the extract and mineral acid obtained in each extraction step may be mixed to perform two or more first scrubbing steps.

[0030] The mineral acid contained in the valuable metal mineral acid salt aqueous solution 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 acid salt contained in the valuable metal mineral acid salt aqueous solution is appropriately set within a range not exceeding the saturated solubility of the valuable metal mineral acid salt. In the first scrubbing, depending on the extraction rate, valuable metals to be extracted may be removed in addition to lithium and valuable metals. For example, when scrubbing with hydrochloric acid is performed on an extract solution from which cobalt has been extracted, scrubbing lithium and nickel also removes the extracted cobalt, resulting in a decrease in the recovery rate of cobalt. On the other hand, in the second scrubbing, lithium and valuable metals not to be extracted are exchanged for the valuable metals in the valuable metal mineral acid salt. Therefore, lithium and valuable metals not to be extracted can be removed without decreasing the recovery rate of the extracted valuable metals.

[0031] Furthermore, in solvent extraction using an organic solvent to recover valuable metals, a small difference in specific gravity between the organic solvent and the aqueous phase can lead to poor oil-water separability. This poor oil-water separability is particularly problematic when the mineral acid used in the dissolution step is different from that used in the stripping step described below. Impurities derived from the mineral acid used in the dissolution step can be mixed into the stripping step, resulting in a decrease in quality. For example, when hydrochloric acid is used in the dissolution step, chloride ions are mixed into the stripping solution. This can be resolved by performing scrubbing with a mineral acid different from that used in the dissolution step. However, even in this case, if the oil-water separability during scrubbing is poor, droplets of the aqueous phase containing impurities after scrubbing will be mixed into the oil phase after scrubbing, making it impossible to sufficiently remove the impurities. However, when an aqueous solution of a mineral salt is used, as in the second scrubbing, the difference in specific gravity increases, improving oil-water separability and reducing the amount of droplets of the aqueous phase after scrubbing that are mixed into the oil phase after scrubbing. Therefore, a high-quality stripping solution with reduced impurity contamination can be obtained.

[0032] A back-extraction step may be carried out in which the oil phases obtained after the first scrubbing and the second scrubbing are mixed with a mineral acid. The mineral acid used in the back-extraction step preferably includes 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.

[0033] The post-scrubbing aqueous phase 3 obtained in each of the first scrubbing and the second scrubbing may or may not be returned to the first extraction step. If the post-scrubbing aqueous phase 3 is not returned to the first extraction step, there is no need to increase the scale of the equipment used in the first extraction step and subsequent steps. Patent Document 1 does not disclose scrubbing of the extract containing manganese, cobalt, and nickel obtained by extracting an acid solution with an organic solvent. Patent Document 2 discloses that the post-scrubbing aqueous phase 3 obtained by scrubbing the extract containing manganese, cobalt, and nickel obtained by extracting an acid solution with an organic solvent is returned to the previous step, but does not disclose that the post-scrubbing aqueous phase 3 is subjected to the lithium recovery step described below. Patent Documents 3 and 4 do not mention treatment of the post-scrubbing aqueous phase 3 obtained by scrubbing the extract containing manganese, cobalt, and nickel obtained by extracting an acid solution with an organic solvent.

[0034] (Crystallization Step) The stripped solution obtained in the stripping step may be subjected to crystallization to obtain a valuable metal salt crystallized product and a crystallization residue. The crystallization residue may be used as an aqueous solution of valuable metal mineral salt in the scrubbing step, or may be subjected to a lithium recovery step described below.

[0035] <Lithium Recovery Step> The method for recovering valuable metals of the present invention includes a lithium recovery step of recovering lithium in the post-scrubbing aqueous phase 3 obtained through the scrubbing step. Note that when the liquid containing valuable metals and lithium contains at least two elements selected from the group consisting of aluminum, cobalt, nickel, and manganese, the lithium recovery step is performed on each of the two or more post-scrubbing aqueous phases 3.

[0036] (Second Extraction Step) The lithium recovery step may include a second extraction step (STEP 4 in FIG. 1 ) in which the post-scrubbing aqueous phase 3 obtained in the scrubbing step is mixed with a second organic solvent containing a carboxylic acid extractant, an oxime extractant, or a phosphorus extractant to obtain a lithium-containing extraction residue 5. Examples of the carboxylic acid extractant include neodecanoic acid and naphthenic acid. The carboxylic acid extractant preferably contains neodecanoic acid, and more preferably is neodecanoic acid. Neodecanoic acid as a carboxylic acid extractant is commercially available from, for example, Hexion Specialty Chemicals. Examples of phosphorus extractants include Cyanex 301, commercially available from Solvay.

[0037] The second organic solvent may contain a diluent, and the concentration of the carboxylic acid extractant may be appropriately adjusted. Examples of the diluent include hydrocarbons such as kerosene and decane, and third petroleum products. A typical example of the third petroleum product is MC531 manufactured by Tobu Chemical Co., Ltd. The concentration of the carboxylic acid extractant in the organic solvent is preferably in the range of 10 to 40% by mass. The extract obtained in the second extraction step may be subjected to back-extraction, and the oil phase after back-extraction may be returned to the second extraction step.

[0038] (Second Impurity Removal Step) When magnesium is contained in the lithium-containing extraction residue 5 obtained in the second extraction step, the lithium recovery step may include a second impurity removal step in which impurities such as magnesium are removed. The second impurity removal step may include a magnesium removal step in which magnesium is adsorbed and removed by an ion exchange resin, thereby obtaining a lithium-containing solution 6. The ion exchange resin includes an iminodiacetic acid-type chelating resin. Examples of the iminodiacetic acid-type chelating resin include Diaion CR-11 manufactured by Mitsubishi Chemical Corporation and MTS9300 manufactured by Purolite Co., Ltd.

[0039] (Concentration Step) The lithium recovery step may include a concentration step (STEP 5 in FIG. 1) of concentrating lithium in the first solution. The concentration step is not limited to a specific method. The concentration step may be performed by the method disclosed in Japanese Patent No. 7377569, or by at least one method selected from the group consisting of a reverse osmosis membrane (RO membrane) method, an evaporation concentration method, and a solvent extraction method.

[0040] <Membrane Electrolysis Step> The valuable metal recovery method of the present invention may include a membrane electrolysis step in which the lithium-containing solution obtained in at least one step selected from the group consisting of the first extraction step and the concentration step is mixed with the extraction residue 4 obtained through the first extraction step, and the mixture is subjected to membrane electrolysis. The membrane electrolysis step may be performed by, for example, the method described in WO 2023 / 195533.

[0041] <Step of Producing a High-Purity Aqueous Lithium Salt Solution> The method for recovering valuable metals of the present invention may include a step of producing a high-purity aqueous lithium salt solution, in which an aqueous lithium salt solution having a lithium content in the range of 10 to 70 g / L is obtained from the lithium-containing solution obtained in the concentration step. The step of producing a high-purity aqueous lithium salt solution may be performed by the method described in Japanese Patent No. 7,166,653.

[0042] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0043] In the examples and comparative examples, the contents of valuable metals and chlorine in each solution were measured by an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0044] Example 1 10 kg of positive electrode powder obtained from waste lithium ion batteries was dissolved in hydrochloric acid to obtain 50 L of acid solution A (dissolution step).

[0045] Next, 50 L of bis(2,4,4-trimethylpentyl)phosphinic acid (CYANEX 272, manufactured by Solvay, decane content 70% by mass) diluted with decane was added to 50 L of the acid solution A, and the pH was adjusted to a range of 4.5 to 5.5 using an 8% by mass aqueous solution of lithium hydroxide to extract nickel, yielding 50 L of extract B (first extraction step). Extract B obtained in the first extraction step was scrubbed with 5 L of aqueous nickel sulfate solution (nickel concentration 40 g / L), and the resulting 50 L of scrubbed oil phase C was strip-extracted with 5 L of 16% by mass sulfuric acid to yield 5 L of strip D and 50 L of extraction residue E. The nickel and lithium contents of solutions A to E are shown in Table 1. Because acid solution A and extraction residue E were hydrochloric acid-based, the chlorine concentrations in these solutions were not measured.

[0046]

[0047] Example 2 10 kg of positive electrode powder obtained from a waste lithium ion battery different from the waste lithium ion battery used in Example 1 was dissolved in hydrochloric acid to obtain 50 L of an acid solution a (dissolution step).

[0048] Next, 50 L of bis(2,4,4-trimethylpentyl)phosphinic acid (CYANEX 272, manufactured by Solvay, decane content 70% by mass) diluted with decane was added to 50 L of the acid solution a, and the pH was adjusted to a range of 4.5 to 5.5 using an 8% by mass aqueous solution of lithium hydroxide to extract nickel, yielding 50 L of extract b (first extraction step). Extract b obtained in the first extraction step was scrubbed with 5 L of sulfuric acid (5% by mass), and the resulting 50 L of scrubbed oil phase c was strip-extracted with 5 L of 16% by mass sulfuric acid to yield 5 L of strip-extract d and 50 L of extract residue e. The nickel and lithium contents in solutions a to e are shown in Table 2. Because the acid solution a and extract residue e were hydrochloric acid-based, the chlorine concentrations in these solutions were not measured.

[0049]

[0050] The lithium and chloride ion concentrations were reduced in the stripped solution D obtained in Example 1, in which nickel sulfate was used in scrubbing, and in the stripped solution d obtained in Example 2, in which sulfuric acid was used, and high-purity nickel was recovered. In particular, the nickel concentration in the oil phase C after scrubbing obtained in Example 1 was not reduced, and it was of higher purity than the oil phase c after scrubbing obtained in Example 2. Furthermore, the lithium contained in 50 L of extract B obtained in Example 1 and 50 L of extract b obtained in Example 2 is recovered in the lithium recovery step. When subjected to the lithium recovery step, 54 g and 40 g of lithium can be recovered, respectively, without increasing the scale of the equipment after the first extraction step. The mass of recovered lithium was calculated using the following formula (1): Mass of recovered lithium (g) = Mass of lithium in extract (g) - Mass of lithium in scrubbing solution (g) ... (1)

[0051] 1...active material powder, 2...extract, 3...aqueous phase after scrubbing, 4...extraction residue, 5...extract, 6...liquid containing lithium (liquid after magnesium removal).

Claims

1. A method for recovering valuable metals, comprising: a first extraction step of extracting the valuable metals from a liquid containing the valuable metals and lithium using a first organic solvent containing an extractant; a scrubbing step of carrying out at least one step selected from the group consisting of a first scrubbing step of mixing the extract obtained from the first extraction step with a mineral acid, and a second scrubbing step of mixing the extract obtained from the first extraction step with an aqueous solution of a mineral acid salt of the valuable metal; and a lithium recovery step of recovering lithium from the aqueous phase after scrubbing obtained from the scrubbing step, wherein the valuable metals include at least one selected from the group consisting of aluminum, cobalt, nickel, and manganese.

2. A valuable metal recovery method according to claim 1, wherein the lithium recovery step includes a second extraction step in which the aqueous phase obtained after scrubbing in the scrubbing step is mixed with a second organic solvent containing a carboxylic acid extractant to obtain an extraction residue containing lithium.

3. A method for recovering valuable metals as described in claim 1, wherein the mineral acid in the aqueous solution of a valuable metal mineral salt contains at least one acid selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid.

4. A valuable metal recovery method according to claim 1, further comprising a dissolution step of dissolving the active material powder obtained by pretreating waste lithium-ion batteries in a mineral acid to obtain an acid solution, and a neutralization step of neutralizing the acid solution with an alkali.

5. A valuable metal recovery method according to claim 2, wherein the lithium recovery step includes a concentration step of concentrating lithium in the extraction residue.

6. A valuable metal recovery method according to claim 2, wherein the lithium recovery step includes a second impurity removal step for removing impurities from the extraction residue.

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