Method for recovering liquids containing valuable metals

Abstract

This invention provides a method for recovering valuable metal-containing liquids from waste lithium-ion batteries with a high yield of valuable metals while suppressing carbon dioxide emissions. [Solution] A method for recovering a valuable metal-containing liquid includes an electrode separation step in which the casing of a chemical battery is cut and the electrode body is removed from inside the casing; a grinding step in which the electrode body obtained through the electrode separation step is ground up to obtain a pulverized material; a dissolution step in which the pulverized material obtained through the grinding step is dissolved in a mineral acid to obtain an acid solution; and an impurity removal step in which impurities are removed from the acid solution, the impurity removal step including a copper removal step in which copper is removed.

Description

Technical Field

[0006] , ,

[0005] ,

[0001] The present invention relates to a method for recovering a valuable metal-containing solution.

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 used lithium-ion batteries and reusing them as materials for lithium-ion batteries have been studied.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since the wet process includes a heating step of the used lithium-ion battery in which carbon powder and organic substances are roasted to obtain active material powder and a large amount of energy is consumed, the amount of carbon dioxide emissions was large. Further, in the wet process, as a result of valuable metals remaining on the sieve during sieving of the pulverized product of the used lithium-ion battery, each of cobalt and nickel is lost by 5% or more.

[0006] The problem to be solved by the present invention is to provide a method for recovering a valuable metal-containing solution in which valuable metals are recovered from used lithium-ion batteries with a high yield and carbon dioxide emissions are suppressed. [Means for solving the problem]

[0007] In view of the above problems, the inventors conducted extensive research and found that a method for recovering a valuable metal-containing liquid, in which the electrode body removed from inside the casing is pulverized, the resulting pulverized material is dissolved in mineral acid without going through heating steps, classification steps, etc., and valuable metals are recovered in a wet process, allows for the recovery of valuable metals from waste lithium-ion batteries with a high yield and suppresses carbon dioxide emissions. The present invention was completed based on these findings.

[0008] The present invention relates to a method for recovering a valuable metal-containing liquid, comprising: an electrode separation step in which the casing of a chemical battery is cut and the electrode body is removed from inside the casing; a grinding step in which the electrode body obtained through the electrode separation step is ground to obtain a pulverized material; a dissolution step in which the pulverized material obtained in the grinding step is dissolved in a mineral acid to obtain an acid solution; and an impurity removal step in which impurities are removed from the acid solution, wherein the impurity removal step includes a copper removal step in which copper is removed.

[0009] The method for recovering the valuable metal-containing liquid preferably further includes a discharge step in which the chemical cell is discharged, and an electrolyte recovery step in which the electrolyte is recovered from the discharged chemical cell obtained through the discharge step. The method for recovering the valuable metal-containing liquid preferably includes an extraction step in which at least one selected from the group consisting of manganese, cobalt, and nickel is extracted from the liquid obtained in the impurity removal step using a first extractant containing a first organic solvent, and a first lithium salt aqueous solution is obtained as the residue; and a membrane electrolysis step in which the first lithium salt aqueous solution 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, 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 copper extraction step, the impurity removal 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 metal-containing liquids that recovers valuable metals from waste lithium-ion batteries with a high yield while suppressing carbon dioxide emissions. [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. [Figure 2] A cross-sectional view of chemical battery 1, which is one embodiment of a chemical battery. [Figure 3] An explanatory diagram showing a first embodiment of the electrode separation step. [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 both ends. 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.

[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, "impurity" refers to metals contained in the waste lithium-ion battery 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. <Electrode separation step> The present invention provides a method for recovering valuable metals, which includes an electrode separation step (STEP 1 in Figure 1) in which the casing of a chemical battery is cut and the electrode body is removed from inside the casing. The chemical battery is a battery that generates electricity through an internal chemical reaction and extracts that electrical energy, and is classified into three types: primary batteries, secondary batteries, and fuel cells. The preferred chemical battery is a secondary battery, and the more preferred chemical battery is a lithium-ion battery. The chemical battery may include at least one selected from the group consisting of used chemical batteries and chemical batteries discarded as defective products in the manufacturing step.

[0015] The electrode body constituting the chemical battery is covered by the casing. In the electrode body separation step, the casing is cut and the electrode body is removed from inside the casing. The electrode body separation step allows for the separation of aluminum derived from the casing. In existing methods, aluminum was crushed together with the electrode body, sieved, and then separated. In that process, the valuable metal remained on the sieve, reducing the recovery rate of the valuable metal. This inconvenience is resolved in the electrode body separation step, thus suppressing the reduction in the recovery rate of the valuable metal. Furthermore, since the separated casing is not mixed with other materials, it can be recycled as an aluminum resource as is. After the casing is cut in the electrode body separation step, the electrolyte inside the casing may be recovered as a resource (electrolyte recovery step).

[0016] FIG. 2 is a cross-sectional view of a chemical battery 1 which is an embodiment of a chemical battery. The chemical battery 1 includes a casing 2, an electrode body 3, an electrode terminal plate 4 (a positive electrode 4a and a negative electrode 4b), and current collectors 5 (a positive electrode side current collector 5a and a negative electrode side current collector 5b), and the electrode body 3 and the electrode terminal plate 4 are covered with the casing 2. Further, the electrode body 3 and the electrode terminal plate 4 are electrically connected via the current collectors 5. The method for disassembling the chemical battery of the present invention includes a cutting step in which the casing and the current collector are cut by a cutting blade provided in a cutting unit.

[0017] FIG. 3 is an explanatory view showing an embodiment of the cutting step. The casing 2 is box-shaped, and the casing 2 and the current collector 5 are cut in a direction perpendicular to the surface to which the electrode terminal plate 4 is attached. The cutting location is at least one selected from the group consisting of the positive electrode 4a side (the left broken line in FIG. 3) and the negative electrode 4b side (the right broken line in FIG. 3).

[0018] <Grinding step> The method for recovering valuable metals of the present invention includes a grinding step (STEP 2 in FIG. 1) in which the electrode body obtained through the electrode body separation step is ground to obtain a ground product. The grinding is carried out by a grinder such as a hammer mill or a jaw crusher. When the ground product obtained in the grinding step contains the electrolytic solution in the casing, the electrolytic solution may be recovered as a resource (electrolytic solution recovery step).

[0019] <Dissolution step> The method for recovering valuable metals of the present invention includes a dissolution step (STEP 3 in FIG. 1) in which the ground product obtained through the grinding step is dissolved in a mineral acid to obtain an acid dissolution solution. The ground product obtained in the grinding step is dissolved in a mineral acid without going through steps such as a heating step and a classification step that consume a large amount of energy. 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.

[0020] <Impurity removal step> The method for recovering valuable metals of the present invention includes an impurity removal step (STEP 4 in FIG. 1) in which impurities are removed from the acid dissolution solution.

[0021] (Copper removal step) The impurity removal step includes a copper removal step in which copper is removed. The method for separating copper from an aqueous solution containing copper may be a conventional copper separation method. [Hydrosulfide step] The copper removal step may optionally include a hydrosulfide step in which an acid dissolution solution obtained by subjecting to at least one selected from the group consisting of the first solid-liquid separation step, valuable metal removal step, aluminum extraction step, and first neutralization step described later is mixed with a hydrosulfide salt, and copper sulfide is precipitated. The hydrosulfide salt preferably includes at least one selected from the group consisting of sodium hydrosulfide and lithium hydrosulfide, more preferably includes lithium hydrosulfide, and still more preferably is lithium hydrosulfide.

[0022] [Copper extraction step] The copper removal step may optionally include a copper extraction step in which copper in an acid solution obtained by subjecting the solution to at least one selected from the group consisting of a first solid-liquid separation step, a valuable metal removal step, an aluminum extraction step, and a first neutralization step, as described later, is extracted from an aqueous solution containing copper using an extractant containing an aldoxime. The aldoxime preferably has at least one selected from the group consisting of a condensed polycyclic structure, a condensed polycyclic heterocyclic structure, a diaryl sulfide structure, and a benzene structure. The condensed polycyclic structure preferably has at least one selected from the group consisting of a fluorene structure, a benzofluorene structure, a dibenzofluorene structure, an indene structure, an indane structure, a benzoindene structure, and a benzoindane structure. The condensed polycyclic heterocyclic structure preferably has at least one selected from the group consisting of a carbazole structure, a dibenzofuran structure, a dibenzothiophene structure, a benzocarbazole structure, an indole structure, an indoline structure, a benzoindole structure, a benzoindoline structure, a phenothiazine structure, and a phenothiazine oxide structure. The diaryl sulfide structure preferably has at least one selected from the group consisting of a diphenyl sulfide structure, a naphthylphenyl sulfide structure, and a dinaphthyl sulfide structure.

[0023] Aldoximes are commercially available. An example of a commercially available aldoxime is Acorga, manufactured by CYTEC.

[0024] (First solid-liquid separation step) The impurity removal step may include a first solid-liquid separation step in which carbon powder is removed from the acid solution.

[0025] (Step to remove valuable metals other than lithium, copper, cobalt, manganese, and nickel) The impurity removal step may optionally include a valuable metal extraction step in which the acid solution obtained by the first solid-liquid separation step is mixed with an organic solvent containing at least one selected from the group consisting of the compound represented by the following formula (1), phosphonic acid esters, phosphate esters, phosphinic acid, methyl isobutyl ketone, and trioctylamine, and at least one valuable metal selected from the group consisting of (1) transition metals excluding manganese, cobalt, and nickel, (2) alkaline earth metals, and (3) aluminum.

[0026] [ka]

[0027] In formula (1) above, R1 and R2 each independently represent a hydrocarbon group having 6 to 20 carbon atoms.

[0028] (Aluminum extraction step) The impurity removal step may include an aluminum extraction step in which an acid solution obtained by applying the solution to at least one selected from the group consisting of the first solid-liquid separation step and the valuable metal removal step is mixed with a first extractant containing a first organic solvent, and aluminum is extracted from the acid solution under conditions of equilibrium pH less than 1.8 (see Japanese Patent Publication No. 7453727). The first organic solvent preferably contains 2-ethylhexyl 2-ethylhexyl phosphonate, and more preferably 2-ethylhexyl 2-ethylhexyl phosphonate. The first extractant may contain a diluent, and the concentration of the first organic solvent may be adjusted as appropriate. Examples of the diluent include hydrocarbons such as kerosene and decane. The concentration of the first organic solvent in the first extractant is preferably in the range of 10 to 40% by mass.

[0029] (First neutralization step) The impurity removal step may optionally include a first neutralization step in which the acid solution obtained by subjecting the solution to at least one selected from the group consisting of the first solid-liquid separation step, the valuable metal removal step, and the aluminum extraction step is neutralized with an alkali. Aluminum hydroxide may precipitate in the first neutralization step, and fluorine may coprecipitate with the aluminum hydroxide. The alkali may be added in at least one form selected from the group consisting of aqueous solution and solid form. The alkali preferably includes at least one selected from the group consisting of alkali metal hydroxide and ammonia. Furthermore, 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, and potassium, even more preferably lithium, sodium, or potassium, and particularly preferably lithium.

[0030] (Second solid-liquid separation step) The impurity removal step may include a second solid-liquid separation step in which aluminum hydroxide is separated from the acid solution obtained through the copper removal step. If fluorine coprecipitates with the aluminum hydroxide separated in the second solid-liquid separation step, fluorine is also separated together with the aluminum hydroxide.

[0031] When the method for recovering valuable metals of the present invention is applied to used lithium-ion batteries whose lifespan as a battery product has been exhausted, or lithium-ion batteries that have been discarded as defective products during the manufacturing process, a discharge process may be performed first (discharge step). Various highly safe methods, such as resistive discharge, can be used for the discharge process. All residual charge is discharged by the discharge process, and then the lithium-ion battery obtained through the discharge step may be subjected to the electrode separation step.

[0032] <Calcium Removal Steps> The method for recovering valuable metals according to the present invention may include a calcium removal step in which calcium is removed from the acid solution obtained after the impurity removal step. For example, the acid solution obtained after the impurity removal step is mixed with an organic solvent containing di(2-ethylhexyl) phosphate (D2EHPA), and calcium is extracted from the acid solution. The organic solvent may contain a diluent, and the concentration of D2EHPA may be adjusted as appropriate. Examples of the diluent include hydrocarbons such as kerosene and decane. The concentration of D2EHPA in the organic solvent is preferably in the range of 10 to 40% by mass. The pH during extraction is preferably adjusted to the range of 1.5 to 2.0 by adding lithium hydroxide. The extract obtained after the calcium removal step may be scrubbed, and the aqueous solution after scrubbing may be returned to the calcium removal step. The extract contains cobalt and manganese. Cobalt and manganese are returned to the acid solution by scrubbing. If necessary, the extract containing calcium that has been scrubbed is back-extracted to recover calcium salts.

[0033] At least one of the steps selected from the group consisting of the first solid-liquid separation step, the valuable metal removal step, the aluminum extraction step, the first neutralization step, the hydrosulfidation step, the second solid-liquid separation step, and the calcium removal step may preferably be performed between the dissolution step and the extraction step described later. If two or more of these steps are performed, the order in which the steps are performed may be set as appropriate.

[0034] <Extraction Step> The method for recovering valuable metals according to the present invention may include an extraction step of extracting cobalt, manganese, and nickel from a liquid containing lithium, cobalt, manganese, and nickel using a second extractant containing a second organic solvent (STEP 5 in Figure 1).

[0035] In the extraction step, manganese, cobalt, and nickel, excluding lithium, are each extracted separately by a second extractant, or iron is separated and removed as an aqueous metal sulfate solution. If the alkali is lithium hydroxide, a first aqueous lithium salt solution can be obtained. If the alkali is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide, the first aqueous lithium salt solution and at least one salt of sodium and potassium are separated from the aqueous alkali mixed salt solution obtained in the extraction step by the method disclosed in Japanese Patent Publication No. 7084669. The lithium salt contained in the first aqueous lithium salt solution becomes lithium chloride when hydrochloric acid is used as the mineral acid in the dissolution step. The second organic solvent is at least one selected from the group consisting of organophosphorus compounds such as phosphate esters, phosphonic acid esters, phosphinic acid, and phosphine oxide, hydrooximes, and organic amine compounds. Each of the aqueous metal sulfate solutions may be scrubbed, during which magnesium is removed.

[0036] Examples of the oxidized phosphine include Toly n-octylphosphine (TOPO). Examples of the hydrooximes include 7-hydroxy-5,8-diethyl-6-dodecanone oxime (LIX-63), 5-dodecyl-2-hydroxybenzaldehyde oxime (LIX 860), 2-hydroxy-5-nonylbenzophenone oxime (LIX 65N), 2-hydroxy-5-nonylacetophenone oxime (SME 529), and 2-hydroxy-5-nonylphenylbenzylketone oxime (Acorga P-17). Examples of the aforementioned organic amine compounds include Primene® JM-T, a primary amine manufactured by Dow Chemical; Amberlite® LA-2, a secondary amine manufactured by Sigma-Aldrich; Alamine 336 (trioctylamine), a tertiary amine manufactured by Sigma-Aldrich; and Aliquat® 336, a quaternary ammonium salt manufactured by Sigma-Aldrich.

[0037] <Membrane electrolysis step> The method for recovering valuable metals according to the present invention may include a membrane electrolysis step (STEP 6 in Figure 1) in which the first lithium salt aqueous solution is electrolyzed 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 membrane electrolysis step is carried out in the same manner as the membrane electrolysis step using an ion exchange membrane disclosed in Patent Document 1.

[0038] The lithium hydroxide aqueous solution obtained in the membrane electrolysis step, which may be included in the method for recovering valuable metals of the present invention, may be 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 may be reused as the mineral acid used in the dissolution step. [Explanation of Symbols]

[0039] 1...Chemical battery, 2...Casing, 3...Electrode body, 4a...Positive terminal plate, 4b...Negative terminal plate, 5a... Positive electrode current collector, 5b... Negative electrode current collector, 6... Tape.

Claims

1. A method for recovering a liquid containing valuable metals, An electrode separation step is performed in which the casing of the chemical battery is cut and the electrode body is removed from inside the casing. The electrode body obtained through the electrode body separation step is then pulverized to obtain a pulverized material in the pulverization step. The pulverized material obtained through the pulverization step is dissolved in mineral acid to obtain an acid solution in the dissolution step, and A method for recovering a valuable metal-containing liquid, comprising an impurity removal step in which impurities are removed from the acid solution.

2. In the method for recovering a valuable metal-containing liquid according to claim 1, The discharge step in which the chemical cell is discharged, and A method for recovering a valuable metal-containing liquid, further comprising an electrolyte recovery step in which the electrolyte is recovered from a discharged chemical battery obtained through the discharge step.

3. In the method for recovering a valuable metal-containing liquid according to claim 1 or 2, An extraction step is performed in which at least one selected from the group consisting of manganese, cobalt, and nickel is extracted from the liquid obtained in the impurity removal step using a first extractant containing a first organic solvent, and a first lithium salt aqueous solution is obtained as the residual liquid, and The first lithium salt aqueous solution 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, further comprising a membrane electrolysis step. The aqueous lithium hydroxide solution obtained in the film electrolysis step is reused in at least one selected from the group consisting of the copper extraction step, the impurity removal step, and the extraction step. A method for recovering a valuable metal-containing liquid, wherein the acid obtained in the film electrolysis step is reused as the mineral acid used in the dissolution step.

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