Aqueous solution recovery method

Abstract

Provided is an aqueous solution recovery method with which it is possible to recover lithium contained in a composite oxide as a lithium-containing aqueous solution.　This aqueous solution recovery method for recovering lithium contained in a composite oxide as a lithium-containing aqueous solution includes: a contact step for bringing chlorine or a chlorine compound adjusted so that the substance amount ratio of chlorine to lithium contained in the composite oxide is 1.0-5.5 into contact with the composite oxide at a temperature of 500-1350°C; and an aqueous solution recovery step for bringing the aqueous solution into contact with the composite oxide and the chlorine or chlorine compound that underwent the contact step, thereby recovering the aqueous solution permeated with the lithium.

Description

Technical Field

[0001] The present invention relates to an aqueous solution recovery method for recovering lithium contained in a composite oxide obtained by dissolving a lithium-ion battery as an aqueous solution containing lithium.

Background Art

[0002] Batteries using lithium (hereinafter referred to as "lithium-ion batteries") are used in relatively small devices such as personal computers and smartphones, as well as in large devices such as electric vehicles and solar power storage facilities.

[0003] ] A lithium-ion battery is formed using an exterior material made of a metal such as iron or aluminum. Inside the exterior material, there are a positive electrode material in which a positive electrode active material such as lithium nickelate or lithium cobaltate is fixed to an aluminum foil, and a negative electrode material in which a negative electrode active material such as graphite is fixed to the surface of a copper foil. And, a separator made of a porous resin film of polypropylene or the like is provided between the positive electrode material and the negative electrode material, and the inside of the exterior material has a structure filled and sealed with an electrolytic solution such as lithium hexafluorophosphate.

[0004] Lithium-ion batteries are disposed of as waste lithium-ion batteries due to performance degradation caused by repeated charging and discharging, or disposal of equipment. Also, when defective products occur in the manufacturing process, they are disposed of as waste lithium-ion batteries. Therefore, with the increase in the number of electric vehicles manufactured in recent years, it is expected that the number of disposed lithium-ion batteries (the number of waste lithium-ion batteries) manufactured for electric vehicles will increase.

[0005] Waste lithium-ion batteries contain valuable metals such as copper, nickel, cobalt, and lithium. Therefore, regarding the disposal of waste lithium-ion batteries, development of recovery and recycling technologies for valuable metals has been carried out as a measure for resource protection and environmental pollution.

[0006] As a method for recovering valuable metals from waste lithium-ion batteries, a dry smelting method has been proposed in which waste lithium-ion batteries are melted at high temperatures, and metals including copper, nickel, and cobalt are recovered from the molten metal obtained by the melting process. An advantage of the dry smelting method is that metals with low resource value, such as aluminum, oxidize and become slag, making it easy to separate them from valuable metals such as copper, nickel, and cobalt.

[0007] In the dry smelting process, lithium contained in waste lithium-ion batteries oxidizes to lithium oxide, which, along with aluminum oxide, silicon oxide, calcium oxide, magnesium oxide, etc., forms slag. Because the lithium content in the formed slag is low, recovering and reusing the lithium is not easy.

[0008] Therefore, research and development are being conducted on methods for recovering lithium from slag with a low lithium content. For example, Patent Document 1 discloses a method for producing slag with a high lithium content by specifying the range of Al / Li and Si / Li values ​​and the Al and Si content for Li-containing slag obtained by melting raw materials such as waste lithium-ion batteries. Patent Document 2 also discloses a method for recovering lithium chloride generated in molten metal as a metal fume by adding a chloride source to the molten metal obtained in a dry smelting method for waste lithium-ion batteries. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2023-173717 [Patent Document 2] Special Publication No. 2022-507413 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] However, the method disclosed in Patent Document 1 requires careful selection of the flux components added to the molten metal during the dry smelting process. Applying this flux as an industrial by-product for recycling (reuse) is difficult, making it impractical for actual operation. Furthermore, the method disclosed in Patent Document 2, when recovering the generated lithium chloride as metal fumes, can cause damage to surrounding equipment such as furnace walls due to the adhesion of metal fumes. As a result, an increase in the costs required for equipment maintenance and repair is expected, making it difficult to apply to actual operation.

[0011] The present invention has been made in view of the above circumstances, and its object is to provide an aqueous solution recovery method that can recover lithium contained in a composite oxide as an aqueous solution containing lithium. [Means for solving the problem]

[0012] [1] A method for recovering lithium contained in a composite oxide as an aqueous solution containing lithium, comprising: a contact step of contacting the composite oxide with chlorine or a chlorine compound, which has been adjusted so that the molar ratio of chlorine to lithium contained in the composite oxide is 1.0 or more and 5.5 or less, at a temperature of 500°C or more and 1350°C or less; and an aqueous solution recovery step of recovering the aqueous solution in which the lithium has permeated by contacting the chlorine or chlorine compound and the composite oxide that have undergone the contact step with an aqueous solution. [2] The aqueous solution recovery method according to [1], wherein the chlorine compound comprises at least one of alkali metal chlorides and alkaline earth metal chlorides. [3] The aqueous solution recovery method according to [1] or [2], wherein the composite oxide is the slag remaining after the metal is recovered by a process of recovering a metal containing one or two elements of cobalt and nickel from the molten metal obtained by dissolving a lithium-ion battery. [4] The aqueous solution recovery method according to any one of [1] to [3], wherein the aqueous solution that is brought into contact with the chlorine or chlorine compound and the composite oxide after the contact step has a pH value of 5.0 or more and 10.0 or less. [Effects of the Invention]

[0013] According to the present invention, lithium contained in a complex oxide can be recovered as a lithium-containing aqueous solution. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below. The aqueous solution recovery method of the present invention is a method for recovering lithium contained in a complex oxide as an aqueous solution containing lithium.

[0015] As a composite oxide, the slag remaining after the recovery of a metal containing one or two elements from cobalt and nickel from the molten metal obtained by dissolving lithium-ion batteries using a dry smelting method may be used.

[0016] The aqueous solution recovery method of the present invention comprises a contact step of bringing chlorine or a chlorine compound, which has been adjusted so that the molar ratio of chlorine to lithium contained in the composite oxide is 1.0 or more and 5.5 or less, into contact with the composite oxide at a temperature of 500°C or more and 1350°C or less.

[0017] By setting the molar ratio of chlorine to lithium in the composite oxide to 1.0 or higher, the chlorination reaction between lithium and chlorine or chlorine compounds is promoted.

[0018] Furthermore, if the molar ratio of chlorine to lithium contained in the composite oxide is less than 1.0, the chlorination reaction between lithium and chlorine or chlorine compounds will not be promoted, and lithium cannot be sufficiently recovered. Also, if the molar ratio of chlorine to lithium contained in the composite oxide is too high, the amount of chlorine added to the lithium will be excessive, and even if the supply of chlorine or chlorine compounds is further increased, there will be no change in the effect of lithium recovery, and processing costs will increase. Therefore, the molar ratio of chlorine to lithium contained in the composite oxide is preferably 5.5 or less, and more preferably 5.0 or less.

[0019] Here, the adjustment of chlorine or chlorine compounds may be performed by calculating the mass of lithium contained in the complex oxide before contact with the complex oxide, and adjusting the amount of chlorine to lithium based on the calculated mass of lithium so that the molar ratio of chlorine to lithium is between 1.0 and 5.5. More specifically, the amount of chlorine or chlorine compound to be contacted with the complex oxide may be adjusted so that the molar ratio of chlorine to lithium is between 1.0 and 5.5. The method for calculating the mass of lithium is not limited as long as it is a method that can calculate the mass of lithium contained in the complex oxide. For example, a portion of the complex oxide may be dissolved in acid, and the measurement and calculation may be performed using inductively coupled plasma atomic emission spectrometry (ICP-AES). Alternatively, in the process of producing the complex oxide, the calculation may be based on the mass concentration of lithium contained in each raw material and the weight ratio of each raw material to the total raw materials.

[0020] The contact between chlorine or a chlorine compound and a composite oxide is carried out at a temperature of 500°C or higher and 1350°C or lower. This is because when the contact is carried out at a temperature lower than 500°C, the chlorination reaction between lithium contained in the composite oxide and chlorine or the chlorine compound is not promoted. Since the chlorination reaction between lithium and chlorine or the chlorine compound is promoted as the temperature is higher during the contact between chlorine or the chlorine compound and the composite oxide, it is preferably carried out at a temperature of 600°C or higher, and more preferably at a temperature of 800°C or higher. Further, when the temperature exceeds 1350°C, although the chlorination reaction between lithium and chlorine or the chlorine compound is promoted to generate lithium chloride, the volatilization of lithium chloride occurs, and the subsequent penetration into the aqueous solution is not promoted, resulting in a decrease in the lithium recovery rate.

[0021] Here, chlorine gas may be applied as chlorine. A metal chloride may be applied as the chlorine compound. Specifically, the chlorine compound may include at least one of chlorides of alkali metals and chlorides of alkaline earth metals. Note that beryllium and magnesium are also included in the alkaline earth metals. These chlorine compounds and chlorine have a higher boiling point compared to compounds of heavy metals and chlorine. Therefore, by setting the temperature during the contact between chlorine or the chlorine compound and the composite oxide to 500°C or higher and 1350°C or lower, the volatilization of the chlorine compound and chlorine can be suppressed, and the formation of lithium chloride from the lithium contained in the composite oxide can be promoted.

[0022] Further, more specifically, the temperature during the contact between chlorine or the chlorine compound and the composite oxide may be controlled as the temperature of the composite oxide. Alternatively, it may be controlled as the temperature of the atmosphere in the reaction vessel into which chlorine or the chlorine compound and the composite oxide are charged.

[0023] The method for recovering an aqueous solution of the present invention has an aqueous solution recovery step of recovering an aqueous solution in which lithium has penetrated by bringing an aqueous solution into contact with chlorine or a chlorine compound and a composite oxide that have undergone a contact step.

[0024] By contacting chlorine or a chlorine compound with a composite oxide, the chlorination reaction between lithium contained in the composite oxide and chlorine or the chlorine compound is promoted, and lithium chloride is produced. Therefore, by bringing an aqueous solution into contact with the chlorine or chlorine compound and the composite oxide that have undergone the contact step, the produced lithium chloride is incorporated into the aqueous solution, and the state is such that lithium penetrates into the aqueous solution. As a result, the lithium contained in the composite oxide is recovered as an aqueous solution into which lithium has penetrated.

[0025] The time for contacting chlorine or a chlorine compound with the composite oxide is preferably 20 minutes or more and 180 minutes or less. By setting the time of the contact step within this range, the chlorination reaction between lithium and chlorine or the chlorine compound is more promoted, and the lithium contained in the composite oxide can be more reliably recovered as lithium that penetrates into the aqueous solution. In addition, regarding the contact time, if it exceeds 180 minutes, even if the time is extended, no improvement in lithium recovery efficiency can be seen.

[0026] The aqueous solution to be brought into contact with chlorine or a chlorine compound and the composite oxide preferably has a pH value of 5.0 or more and 10.0 or less. By setting the pH value of the aqueous solution to a value within this range, the dissolution of heavy metals (nickel, cobalt, manganese, etc.) into the aqueous solution is suppressed, and the penetration of lithium into the aqueous solution with few coexisting elements is promoted. The aqueous solution may be pure water or the like.

[0027] From the viewpoint of recovering the aqueous solution into which lithium has penetrated by the method for recovering an aqueous solution of the present invention, the composite oxide containing lithium preferably has a lithium content of 0.5% by mass or more in terms of lithium element, and more preferably 1.0% by mass or more.

Examples

[0028] Next, the results of implementing the aqueous solution recovery method of the present invention will be described. In each example, one of four types of oxides (A to D) with different molar ratios of calcium oxide and silicon dioxide (CaO / SiO2) and mass percentage of lithium contained was used as the lithium-containing composite oxide. Table 1 shows the component information of the oxides (A to D) used in the examples.

[0029] [Table 1]

[0030] Then, chlorine compounds were brought into contact with the oxides (A-D) shown in Table 1, such that the molar ratio of chlorine to lithium contained in each oxide was a predetermined value, and the mixture was held at a predetermined temperature for 60 minutes. Next, an aqueous solution was prepared at a weight ratio of 30 times the amount of the chlorine compound and oxide. The chlorine compound and oxide were immersed in the aqueous solution, stirred for 120 minutes, and filtered to obtain an aqueous solution containing lithium. Calcium chloride (CaCl2) was used as the chlorine compound. Pure water with a pH value of 5.0 to 10.0 was used as the aqueous solution.

[0031] Next, the lithium content (mass%) in the obtained aqueous solution was measured, and the lithium recovery rate was calculated as the percentage (%) of the lithium content (mass%) in the aqueous solution relative to the total mass (mass%) of lithium contained in the oxides (A-D). The results are shown in Tables 2 and 3.

[0032] [Table 2]

[0033] [Table 3]

[0034] Comparative Examples 1-19, shown in Table 3, were conducted with oxides A-D as composite oxides, using a molar ratio of chlorine to lithium (Cl / Li) of 0.5, or with a contact temperature of 1400°C between each oxide and the chlorine compound, or with a contact temperature of 400°C between each oxide and the chlorine compound. As a result, the recovery rate of lithium was limited to a maximum of 40% of the total lithium contained in each oxide.

[0035] Examples 1 to 31 of the present invention, shown in Table 2, were carried out with a molar ratio of chlorine to lithium (Cl / Li) contained in oxide A of 1.0 to 5.5, and a contact temperature of 500°C to 1350°C between oxide A and the chlorine compound. As a result, more than 50% of the total lithium contained in oxide A was recovered as an aqueous solution.

[0036] Examples 32 to 46 of the present invention used oxides B, C, and D as composite oxides. The molar ratio of chlorine to lithium contained in oxides B, C, and D (Cl / Li) was set to 1.8 or more and 5.5 or less, and the contact temperature between oxides B, C, and D and the chlorine compound was set to 800°C or more and 1000°C or less. As a result, more than 70% of the total lithium contained in oxides B, C, and D could be recovered as an aqueous solution.

[0037] From the above, it has been confirmed that the aqueous solution recovery method of the present invention can recover lithium contained in a composite oxide as a lithium-containing aqueous solution. Furthermore, it has been confirmed that the aqueous solution recovery method of the present invention can be applied to composite oxides having various compositions while containing lithium, and that a lithium-containing aqueous solution can be recovered without the volatilization of chlorine or chlorine compounds.

Claims

1. A method for recovering lithium contained in a complex oxide as an aqueous solution containing lithium, A contact step in which the chlorine or chlorine compound, which has been adjusted so that the molar ratio of chlorine to lithium contained in the composite oxide is 2.7 or more and 5.5 or less, is brought into contact with the composite oxide at a temperature of 500°C or more and 1350°C or less, A water solution recovery step involves contacting the chlorine or chlorine compound and the composite oxide that have undergone the contact step with an aqueous solution to recover the aqueous solution in which the lithium has permeated; A method for recovering an aqueous solution, comprising the following characteristics.

2. The aqueous solution recovery method according to claim 1, wherein the chlorine compound comprises at least one of alkali metal chlorides and alkaline earth metal chlorides.

3. The aqueous solution recovery method according to claim 1, wherein the composite oxide is slag remaining after the metal is recovered by a process of recovering a metal containing one or two elements of cobalt and nickel from the molten metal obtained by dissolving a lithium-ion battery.

4. The aqueous solution recovery method according to claim 2, wherein the composite oxide is slag remaining after the metal is recovered by a process of recovering a metal containing one or two elements of cobalt and nickel from the molten metal obtained by dissolving a lithium-ion battery.

5. The aqueous solution recovery method according to any one of claims 1 to 4, wherein the aqueous solution that is brought into contact with the chlorine or chlorine compound and the composite oxide after the contact step has a pH value of 5.0 or more and 10.0 or less.

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