Methods for recovering valuable metals

Abstract

This invention provides a method for neutralizing aqueous solutions containing metal salts at low cost and recovering valuable metals. [Solution] A method for recovering valuable metals includes a second neutralization step in which an aqueous solution containing a metal salt is neutralized using an ion exchange resin.

Description

Technical Field

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

Background Art

[0002] The burden on the environment caused by metal mining and refining is large. By recovering valuable metals in used products and reusing them as raw materials, the need for new mining and refining can be reduced, and the burden on the environment can be alleviated.

[0003] In particular, with the recent spread of lithium-ion batteries, methods for recovering valuable metals from used lithium-ion batteries and reusing them as materials for the lithium-ion batteries have been studied.

[0004] For example, 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 for each element of the valuable metals by a wet process (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the conventional method for recovering valuable metals, each element of the valuable metals was recovered individually. The aqueous solution containing each element of the valuable metals recovered using an organic solvent as an extractant was neutralized with an alkali and then filtered.

[0007] Neutralizing the aqueous solutions containing each element of the valuable metals while heating them takes a long time. Furthermore, in addition to insoluble components, unreacted additives are generated as sludge during neutralization, and this sludge easily clogs the filter media, making the filtration process burdensome. Moreover, the alkali used as a neutralizing agent is consumed during operation, so the cost of this alkali is incurred along with the operation. In addition, impurities originating from the neutralizing agent are introduced, reducing the quality of the recovered valuable metals. Consequently, the costs of neutralization and filtration were high, and the quality of the recovered valuable metals was not high.

[0008] The problem that this invention aims to solve is to provide a method for neutralizing an aqueous solution containing valuable metals as metal salts, which is prepared when recovering valuable metals from various metal-containing wastes, at low cost, and recovering the valuable metals. [Means for solving the problem]

[0009] In view of the above problems, the inventors conducted extensive research and found that aqueous solutions containing metal salts can be neutralized using ion exchange resins. The present invention was completed based on these findings.

[0010] The present invention relates to a method for recovering valuable metals, comprising a second neutralization step of neutralizing an aqueous solution containing a metal salt using an ion exchange resin.

[0011] The aforementioned valuable metal is preferably at least one selected from the group consisting of aluminum, manganese, cobalt, and nickel.

[0012] The method for recovering the valuable metal preferably further includes a crystallization step of crystallizing the aqueous solution obtained after the second neutralization step.

[0013] The ion exchange resin preferably includes an anion exchange resin.

[0014] The aqueous solution containing the metal salt is preferably an aqueous solution obtained by an extraction step of extracting the valuable metal from a liquid containing the valuable metal using an organic solvent, and a back-extraction step of back-extracting the extract obtained through the extraction step to obtain a back-extract containing the valuable metal.

[0015] 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 first neutralization step of neutralizing the acid solution with an alkali, and a membrane electrolysis step of performing membrane electrolysis on a 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 first 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]

[0016] The present invention provides a method for recovering valuable metals by neutralizing an aqueous solution containing valuable metals as metal salts at low cost. [Brief explanation of the drawing]

[0017] [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]

[0018] The present invention will be described in more detail.

[0019] 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.

[0020] In this invention, "metal-containing products" refers to all products containing metal elements, such as home appliances, automobiles, fasteners, electronic components, and batteries. "Metal-containing waste" refers to used metal-containing products whose product lifespan has been exhausted, metal-containing products discarded as defective products during the manufacturing process, and residual metal materials used in product manufacturing. Furthermore, crushed material, coarse material, fine fragments, and powder obtained from the aforementioned metal-containing waste are referred to as metal-containing powder. In addition, "impurities" refers to metals contained in the metal-containing powder that do not require recovery.

[0021] In this invention, waste lithium-ion batteries refer to used lithium-ion batteries whose lifespan as a battery product has been exhausted, lithium-ion batteries discarded as defective products during the manufacturing process, and metal-containing waste such as residual positive electrode material and negative electrode material used in the manufacturing process. Furthermore, the active material powder is made from powder containing positive and negative electrodes obtained from the waste lithium-ion batteries, as well as metal-containing powder such as crushed positive electrode plates, coarsely crushed materials, and fine fragments.

[0022] In the method for recovering valuable metals of the present invention, the valuable metal to be recovered may be any metal element, for example, lithium, beryllium, sodium, magnesium, aluminum, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, cesium, barium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, polonium, francium, radium, actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, lawrencium, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, darmstadtium, roentgenium, copernicium, nihonium, flerovium, moscovium, and livermorium. The valuable metal to be recovered is preferably at least one selected from the group consisting of aluminum, manganese, cobalt, and nickel.

[0023] One embodiment of the method for recovering valuable metals of the present invention will be described in more detail with reference to the accompanying drawings.

[0024] <Extraction step> The method for recovering valuable metals according to the present invention may include an extraction step of extracting the valuable metals from a liquid containing the valuable metals using an organic solvent (STEP 3 in FIG. 1). When the method for recovering valuable metals according to the present invention uses the metal-containing powder 1 as a starting material, a dissolution step and an impurity removal step described below may be performed on the metal-containing powder 1 to obtain the liquid containing the valuable metals. When the method for recovering valuable metals according to the present invention uses an acid waste liquid containing one or more metal elements discharged from various industrial processes as a starting material, an impurity removal step described below may be performed on the acid waste liquid containing the one or more metal elements to obtain the liquid containing the valuable metals.

[0025] The liquid containing the valuable metals 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 manganese, cobalt, and nickel is extracted by each of three 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 the compounds described in International Publication No. 2023 / 195533.

[0026] The organic solvent contains 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.

[0027] The present invention's method for recovering valuable metals may use metal-containing powder 1 as a starting material. As a representative example, the case in which the metal-containing powder 1 is active material powder will 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. constituting 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 may be obtained by heat treatment at the temperature in the range mentioned above.

[0028] If the waste lithium-ion battery is the residual positive electrode material, etc., used in the manufacturing process, the discharge treatment and opening formation may be omitted, and the material may be heated at the temperature within the range, or without heating, and then crushed in the crusher to remove the current collector, etc., by sieving, in order to obtain the active material powder. Furthermore, the waste lithium-ion battery may be crushed in the crusher, the current collector, etc., may be removed by sieving, and then heated at the temperature within the range, or without heating, in order to obtain the active material powder.

[0029] <Dissolution Step> The method for recovering valuable metals according to the present invention may include a dissolution step (STEP 1 in Figure 1) of dissolving the metal-containing powder 1 in a mineral acid to obtain an acid solution. The metal-containing powder 1 contains one or more metal elements. The mineral acid preferably contains at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably hydrochloric acid, and even more preferably hydrochloric acid.

[0030] <Impurity Removal Step> The method for recovering valuable metals according to the present invention may include an impurity removal step (STEP 2 in Figure 1) in which impurities are removed from the acid solution. A preferred example will be described when the starting material is an active material powder.

[0031] (Copper removal step) The impurity removal step may include 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.

[0032] [Hydroxysulfidation step] The copper removal step may optionally include a hydrosulfidation step in which an acid solution obtained by subjecting the copper to at least one of the group consisting of a first solid-liquid separation step, a valuable metal removal step, and a first neutralization step, as described later, is mixed with a hydrosulfide salt to precipitate copper sulfide. The hydrosulfide salt preferably comprises at least one selected from the group consisting of sodium hydrosulfide and lithium hydrosulfide, more preferably lithium hydrosulfide, and even more preferably lithium hydrosulfide.

[0033] [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, 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. Aldooximes are commercially available. An example of a commercially available aldoxime is acorga manufactured by CYTEC.

[0034] (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.

[0035] (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 such as iron, excluding manganese, cobalt, and nickel, (2) alkaline earth metals, and (3) aluminum.

[0036] [ka]

[0037] In formula (1) above, R1 and R2 each independently represent a hydrocarbon group having 6 to 20 carbon atoms.

[0038] (First neutralization step) The impurity removal step may optionally include a first neutralization step in which the acid solution obtained by subjecting the first solid-liquid separation step and the valuable metal removal step to at least one of the group 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.

[0039] (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.

[0040] <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. A preferred example will be described in which the starting material is an active material powder.

[0041] For example, the acid solution obtained through 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 through 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 the calcium salt.

[0042] At least one of the steps selected from the group consisting of the first solid-liquid separation step, the valuable metal removal 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. If two or more of these steps are performed, the order in which the steps are performed may be set as appropriate.

[0043] <Reverse extraction step> The method for recovering valuable metals according to the present invention may include 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 (for example, an extract containing aluminum, an extract containing manganese, an extract containing cobalt, and an extract containing nickel).

[0044] <Second Neutralization Step> The present invention provides a method for recovering valuable metals, which includes a second neutralization step (STEP 5 in Figure 1) in which an aqueous solution containing a metal salt is neutralized using an ion exchange resin.

[0045] If the method for recovering valuable metals of the present invention uses the metal-containing powder 1 as a starting material, the dissolution step, the extraction step, and the back-extraction step may be performed on the metal-containing powder 1, and the resulting back-extract may be an aqueous solution containing the metal salt. If the method for recovering valuable metals of the present invention uses acid waste liquid containing multiple types of metal elements discharged from various industrial processes as a starting material, the extraction step and the back-extraction step may be performed on the acid waste liquid containing multiple types of metal elements to obtain multiple aqueous solutions containing the metal salt. If the method for recovering valuable metals of the present invention uses acid waste liquid containing one type of metal element discharged from various industrial processes as a starting material, the acid waste liquid containing one type of metal element may be an aqueous solution containing the metal salt.

[0046] The ion exchange resin preferably includes an anion exchange resin, more preferably a weakly basic anion exchange resin, and even more preferably a weakly basic anion exchange resin. The weakly basic anion exchange resin is commercially available. Examples of commercially available weakly basic anion exchange resins include Diaion® WA-20 manufactured by Mitsubishi Chemical Corporation, Amberlite® IRA96SB manufactured by Organo Corporation, and Muromachi Chemical Co., Ltd.'s Muromac WMT-7411. The ion exchange resin may also include a strongly basic anion exchange resin. Examples of commercially available strongly basic anion exchange resins include Diaion® PA 316 manufactured by Mitsubishi Chemical Corporation, Amberlite® IRA402BL Cl manufactured by Organo Corporation, and Muromachi Chemical Co., Ltd.'s Muromac XMB-4613.

[0047] The aqueous solution containing the metal salt neutralized in the second neutralization step is of high quality and has reduced cost because it was produced without the use of a neutralizing agent.

[0048] <Filtration Step> The method for recovering valuable metals according to the present invention may include a filtration step (STEP 6 in Figure 1) in which an aqueous solution containing the metal salt neutralized in the second neutralization step is filtered. In the filtration step, insoluble components are generated as sludge in the second neutralization step, but since no alkali is added, no sludge originating from unreacted additives is generated. Therefore, the filtration burden in the filtration step is small.

[0049] <Crystalling Step> The method for recovering valuable metals according to the present invention may include a crystallization step (STEP 7 in Figure 1) in which the aqueous solution obtained after the second neutralization step and the filtration step, which may be performed as needed, is crystallized to obtain a salt 2 of the valuable metal. The purity of the salt 2 of the valuable metal is high and the cost is reduced.

[0050] <Membrane electrolysis step> The method for recovering valuable metals according to the present invention may include a membrane electrolysis step (STEP 8 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]

[0051] 1. Metal-containing powder, 2. Salt of valuable metals.

Claims

1. A method for recovering valuable metals, A method for recovering valuable metals, comprising a second neutralization step of neutralizing an aqueous solution containing a metal salt using an ion exchange resin.

2. A method for recovering a valuable metal according to claim 1, wherein the valuable metal is at least one selected from the group consisting of aluminum, manganese, cobalt, and nickel.

3. A method for recovering valuable metals according to claim 1, further comprising a crystallization step of crystallizing the aqueous solution obtained after the second neutralization step.

4. A method for recovering valuable metals according to claim 1, wherein the ion exchange resin includes an anion exchange resin.

5. A method for recovering valuable metals according to claim 1, wherein the aqueous solution containing the metal salt is An extraction step of extracting the valuable metal from the liquid containing the valuable metal using an organic solvent, and A method for recovering valuable metals, comprising a back-extraction step in which the extract obtained through the extraction step is back-extracted to obtain a back-extract containing the valuable metal, and an aqueous solution obtained through this back-extraction step.

6. In the method for recovering valuable metals described in claim 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 first neutralization step in which the acid solution is neutralized with an 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 selected from the group consisting of the first 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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