Method for separating aluminum salt and method for separating metal salt

Abstract

To provide a method enabling simple and selective separation of aluminum ions from an aqueous solution containing a variety of metal ions, and also provide a method for separating aluminum ions and also simply separating transition metal ions and lithium ions from an aqueous solution containing various metal ions.MEANS: A method for separating aluminum salt from an aqueous solution containing metal salts including aluminum salt comprises a step of adding ammonium sulfate to the aqueous solution containing the metal salts, a step of adding alcohol, a step of stirring the resulting solution, and a step of crystallizing the aluminum salt.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for separating aluminum salts and a method for separating metal salts. [Background technology]

[0002] In recent years, the use of lithium-ion batteries has been increasing worldwide, while at the same time, development of methods for re-separating and recovering metals from used batteries is being promoted. In general, metals are often separated from such batteries by firing raw compounds containing metal elements, followed by acid leaching, and then separation, and it is necessary to separate metal ions from the liquid phase. Separation of metal ions from the liquid phase is mainly performed by solvent extraction, but it is relatively difficult to carry out on an industrial scale from the viewpoint of equipment and cost.

[0003] There are methods for separating metal ions in an aqueous solution, such as the ion exchange resin method and the ion exchange membrane electrodialysis method, but the separation coefficient between metals is small in the electrodialysis method, and a considerable number of multi-stage cascade operations are required when performing separation using only an ion exchange membrane. In addition, when a solution containing aluminum ions is usually handled, aluminum ions form precipitates due to changes in the liquid properties of the solution, and the precipitation of aluminum salts near the interface between different phases can cause problems in the operation of the equipment, and therefore pretreatment is required when handling a solution containing aluminum.

[0004] Furthermore, the present inventors have developed methods for separating metal salts (Patent Document 1), but have not investigated the separation of aluminum. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-37438 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, the separation of aluminum ions has not been studied as a method for separating metal ions, and a method for selectively separating aluminum ions from an aqueous solution containing various metal ions by a simple method has been desired. In addition, a method for separating aluminum ions from an aqueous solution containing various metal ions and a method for simply separating transition metal ions and lithium ions have been desired. The present invention aims to provide these methods. [Means for solving the problem]

[0007] As a result of extensive investigations, the present inventors have obtained the following findings. By adding ammonium sulfate and alcohol to an aqueous solution containing transition metal ions, it is possible to crystallize the salts of the transition metal ions. By adding ammonium sulfate and alcohol to an aqueous solution containing metal ions, including aluminum ions, and then stirring the resulting aqueous solution, the crystallization of the aluminum ion salt can be promoted. By carrying out the above-mentioned operation on an aqueous solution containing lithium ions, transition metal ions, and aluminum ions, it is possible to separate the transition metal ions and aluminum ions from each other, and as a result, to isolate the lithium ions.

[0008] Based on the above findings, the present inventors have completed the following invention. [1] A method for separating an aluminum salt from an aqueous solution containing a metal salt including an aluminum salt, comprising the steps of: adding ammonium sulfate to the aqueous solution containing the metal salt; adding alcohol; stirring the resulting solution; The method includes a step of crystallizing an aluminum salt. Methods for separating aluminum salts.

[0009] [2] The method for separating an aluminum salt according to [1], wherein the alcohol is one or a mixture of two or more selected from the group consisting of methanol, ethanol, and propanol. [3] The method for separating an aluminum salt according to [1] or [2], wherein the stirring speed in the stirring step is 200 rpm or more.

[0010] [4] A method for separating transition metal salts, aluminum salts, and lithium salts from an aqueous solution containing these metals, comprising the steps of: adding ammonium sulfate to the aqueous solution and adding an alcohol to the aqueous solution, thereby precipitating a transition metal salt; The method for separating a metal salt further comprises a step of stirring the obtained aqueous solution, thereby precipitating an aluminum salt.

[0011] [5] The method for separating a metal salt according to [4], wherein the transition metal salt is at least one selected from a nickel salt and a cobalt salt. Effect of the Invention

[0012] According to the method for separating an aluminum salt of the present invention, the initial velocity of crystallization of the aluminum salt can be improved, thereby accelerating the crystallization of the aluminum salt, and it becomes possible to separate the aluminum salt by a simple method in a short time. Furthermore, according to the method for separating a metal salt of the present invention, it becomes possible to separate a transition metal salt, an aluminum salt, and a lithium salt from an aqueous solution containing the transition metal salt, an aluminum salt, and a lithium salt, respectively, in a simple manner and in a short time. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the weight and residual rate of aluminum in an aqueous solution in Comparative Example 1. [Diagram 2] FIG. 2 is a diagram showing the weight and residual rate of cobalt in an aqueous solution in Comparative Example 2. [Diagram 3]FIG. 3 is a diagram showing the weight and residual rate of aluminum in an aqueous solution in Example 1. [Figure 4] FIG. 4 is a diagram showing the weight and residual rate of aluminum in an aqueous solution in Example 2. [Diagram 5] FIG. 5 is a diagram showing the weight and residual rate of aluminum in an aqueous solution in Example 3. [Figure 6] FIG. 6 is a graph showing the relationship between the stirring speed and the initial velocity of crystallization, as well as the concentration of the liquid phase when equilibrium is reached, for the results of Examples 1 to 3. [Figure 7] FIG. 7 shows the results of separation of lithium, cobalt / nickel group, and aluminum from an aqueous solution containing lithium, cobalt, nickel, and aluminum. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] <Method of separating aluminum salts> The method for separating an aluminum salt of the present invention is a method for separating an aluminum salt from an aqueous solution containing a metal salt including an aluminum salt, the method comprising the steps of: adding ammonium sulfate to the aqueous solution containing the metal salt; adding an alcohol; stirring the resulting solution; The process includes a step of crystallizing an aluminum salt.

[0015] (Aqueous solution containing metal salts including aluminum salts) The aqueous solution containing a metal salt including an aluminum salt is not particularly limited as long as it is an aqueous solution in which the aluminum salt to be separated is dissolved, and may be a solution prepared by dissolving an aluminum salt in water, or an acid leachate obtained by leaching a solid containing aluminum and / or an aluminum salt with an acid such as sulfuric acid or hydrochloric acid. Examples of the aluminum salt include aluminum chloride, aluminum sulfate, and aluminum oxide. Aluminum chloride and aluminum oxide may form double salts with aluminum sulfate.

[0016] The aqueous solution may contain one or more metal salts other than the aluminum salt, and may be separated from these other metal salts by utilizing the difference in the initial velocity of crystallization with the aluminum salt, or may be separated from these other metals by utilizing the difference in ease of crystallization.

[0017] Other metal species include common base metals such as iron, magnesium, and copper, as well as alkali metals such as lithium, rare metals such as nickel, cobalt, vanadium, cesium, and strontium, and rare earth metals such as praseodymium and lanthanum.

[0018] The concentration of the aluminum salt in the aqueous solution is not particularly limited, but an aqueous solution having a metal salt concentration in the range of 0.001 mol / L to 1 mol / L is usually used. If the metal salt concentration is too low, the aluminum salt may be difficult to crystallize, and conversely, if the aluminum salt concentration is too high, crystallization may occur before the stirring step described below.

[0019] (Step of adding ammonium sulfate) In the method for separating aluminum salts of the present application, ammonium sulfate is first added to an aqueous solution containing aluminum salts. In the method of the present application, the lower limit of the ammonium sulfate concentration of the resulting solution is preferably 0.01 mol / L or more, more preferably 0.05 mol / L or more, and even more preferably 0.1 mol / L or more, and the upper limit is preferably 3 mol / L or less, more preferably 2 mol / L or less, even more preferably less than 2 mol / L, even more preferably 1 mol / L or less, and even more preferably 0.5 mol / L or less.

[0020] The concentration of ammonium sulfate can be appropriately selected and combined according to the concentration of the alcohol to be added, which will be described below. In other words, when the concentration of ammonium sulfate is high, the concentration of the alcohol (e.g., methanol) may be somewhat low, and conversely, when the concentration of ammonium sulfate is low, the amount of crystallization can be controlled to some extent by increasing the concentration of the alcohol.

[0021] (Step of adding alcohol) An alcohol is added to the solution obtained in the above step. Examples of alcohol that can be used include methanol, ethanol, and propanol, which are poor solvents for water and have a dielectric constant lower than that of water, and these may be used in combination of two or more kinds. Among them, methanol is preferred because it is inexpensive and easy to recover. The amount of alcohol added is such that the alcohol concentration in the solution after the addition is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and still more preferably 40% by mass or more.

[0022] As described above, the alcohol may be added after the addition of ammonium sulfate, or the steps may be reversed, i.e., the alcohol is added first and then the ammonium sulfate is added, or ammonium sulfate and the alcohol may be added simultaneously. In the case where ammonium sulfate is added later, it is sufficient to add it so that the concentration becomes the above-mentioned concentration based on the solution excluding the alcohol.

[0023] (Step of stirring the obtained solution) In this step, as described above, the solution obtained by adding ammonium sulfate and alcohol is subjected to stirring treatment. The method for stirring the solution is not particularly limited, but it is preferable to adopt a mechanical stirring method such as a method using a stirring blade or a stirring blade or a method using a stirring bar. By stirring the obtained solution, it is possible to promote the crystallization of aluminum salt. It is difficult to crystallize aluminum salt even if vibration stirring is performed using a so-called vortex mixer or the like.

[0024] The inventors predict that the number of collisions of aluminum particles increases by stirring the solution obtained above, and the initial rate of crystallization of aluminum salt increases. Possible methods for increasing the number of collisions of aluminum particles include (1) increasing the stirring time and (2) increasing the stirring speed.

[0025] The stirring speed is preferably 100 rpm or more, more preferably 150 rpm or more, even more preferably 180 rpm or more, even more preferably 200 rpm or more, even more preferably 300 rpm or more, even more preferably 400 rpm or more, particularly preferably 500 rpm or more, and most preferably 600 rpm or more. There is no particular upper limit, and it is possible to set a high stirring speed that does not interfere with operation. However, when it is desirable to avoid absorption of oxygen or carbon dioxide into the solution due to air entrainment, it is desirable to set the stirring speed so that the influence of air entrainment from the upper surface does not occur even at a high stirring speed.

[0026] The stirring time is preferably 5 minutes or more, more preferably 10 minutes or more, further preferably 20 minutes or more, and particularly preferably 50 minutes or more.

[0027] (Aluminum crystallization process) During the stirring process, aluminum salts crystallize out in the solution.

[0028] After the aluminum salt has crystallized, solid-liquid separation can be performed by filtration to obtain the aluminum salt crystallized as a solid phase, and a solution containing the metal salt that has not crystallized as a liquid phase can be obtained. The crystallized aluminum salt may be washed with an aqueous solution having the same alcohol concentration and ammonium sulfate concentration as the original solution.

[0029] The above operations are usually carried out at room temperature and pressure, but the temperature and pressure may be changed as necessary.

[0030] <Metal salt separation method> The method for separating a metal salt of the present invention is a method for separating each of these metals from an aqueous solution containing a transition metal salt, an aluminum salt, and a lithium salt, comprising the steps of: adding ammonium sulfate to the aqueous solution and adding an alcohol to the aqueous solution, thereby precipitating a transition metal salt; The method further comprises a step of stirring the obtained aqueous solution, thereby precipitating the aluminum salt.

[0031] (Aqueous solution containing transition metal salt, aluminum salt, and lithium salt) The aqueous solution targeted by the metal salt separation method of the present invention contains a transition metal salt, an aluminum salt, and a lithium salt. Examples of the transition metal salt include nickel salt, cobalt salt, iron salt, copper salt, zinc salt, and further lanthanoid salts such as lanthanum, yttrium, and praseodymium, and examples of the salt form include nitrate, chloride, and sulfate. Specifically, examples of the salt include cobalt nitrate, nickel nitrate, iron nitrate, copper nitrate, zinc nitrate, nickel chloride, cobalt chloride, iron chloride, and copper chloride.

[0032] Examples of the aluminum salt include aluminum chloride, aluminum sulfate, and aluminum oxide, and aluminum chloride and aluminum oxide may form double salts with aluminum sulfate. Examples of the lithium salt include lithium chloride, lithium hydroxide, lithium nitrate, lithium sulfate, and lithium acetate.

[0033] (Precipitation of transition metal salts) In the method for separating metal salts of the present invention, first, ammonium sulfate and alcohol are added to the above aqueous solution to precipitate a transition metal salt. Ammonium sulfate and alcohol are added to the above aqueous solution, mixed appropriately, and allowed to stand, whereby the transition metal salt crystallizes. The mixing is preferably performed at 200 rpm or less, the mixing time is preferably 10 seconds to 1 minute, more preferably 20 seconds to 40 seconds, and after mixing, the mixture is preferably allowed to stand for 10 minutes to 1 hour, more preferably 20 minutes to 40 minutes.

[0034] Details of the step of adding ammonium sulfate and the step of adding alcohol in the method for separating metal salts of the present invention are similar to those in the above-mentioned method for separating aluminum salts.

[0035] (Precipitation of aluminum salts) In the method for separating a metal salt of the present invention, after precipitating a transition metal salt as described above, the resulting aqueous solution is stirred to precipitate an aluminum salt. Details of the stirring conditions are the same as those of the stirring step in the method for separating an aluminum salt described above.

[0036] In the method for separating a metal salt of the present invention, as described above, a transition metal salt is precipitated, and then an aluminum salt is precipitated, thereby obtaining an aqueous solution containing a lithium salt in which the contents of these salts are reduced. In other words, the present invention provides a method for separating a lithium salt simply and in a short time. EXAMPLES

[0037] (Crystallization and separation of aluminum from aqueous solutions containing aluminum) The following describes a technique for selectively crystallizing aluminum into a solid phase using ammonium sulfate and methanol. Comparative Example 1 Figure 1 shows the weight and residual rate of aluminum in an aqueous solution containing 0.05 mol / L aluminum chloride and 0.5 mol / L ammonium sulfate, which was mixed for 30 seconds using a general-purpose vortex mixer (NICHIRYO VortexMixer BV1000) until the methanol concentration reached 44.5 wt%, and then left to stand for 30 minutes. Figure 1 shows that under these experimental conditions, the crystallization of aluminum into the solid phase hardly progressed.

[0038] Comparative Example 2 For reference, Figure 2 shows the results of an attempt to crystallize cobalt (cobalt nitrate) under the same conditions. Unlike aluminum, cobalt crystallizes into a solid phase in response to an increase in the methanol concentration.

[0039] (Examples 1 to 3) 3 to 5 show the results of a crystallization operation in which methanol was added to an aqueous solution containing 0.05 mol / L of aluminum chloride and 0.5 mol / L of ammonium sulfate until the concentration became 28.4 wt %, and the resulting aqueous solution was stirred at 200 rpm (FIG. 3, Example 1), 400 rpm (FIG. 4, Example 2), and 600 rpm (FIG. 5, Example 3) using a magnetic stirrer and a commercially available magnetic stirrer (HSH-6D, ASONE).

[0040] From the figure, it can be seen that when stirring is performed continuously, aluminum salts begin to crystallize rapidly in the liquid phase, and the crystallization rate increases as the stirring speed increases. Therefore, it can be seen that aluminum salts can be crystallized by adding appropriate amounts of ammonium sulfate and methanol to an aqueous solution containing aluminum and then stirring for any period of time.

[0041] Figure 6 shows the relationship between the stirring speed and the initial rate of crystallization, as well as the concentration of the liquid phase when equilibrium is reached, for the results of Examples 1 to 3. It can be seen from the figure that the initial rate of crystallization increases with increasing stirring speed, while the concentration at equilibrium remains the same. From this result, it is presumed that the crystallization of aluminum proceeds under diffusion-controlled conditions, and considering this together with the results for cobalt in Figure 2, it is presumed that separation of aluminum from other metals such as cobalt is possible by utilizing the difference in crystallization rates.

[0042] Example 4 Figure 7 shows the results of separating lithium, cobalt / nickel, and aluminum from an aqueous solution containing lithium, cobalt, nickel, and aluminum (aqueous solution containing lithium nitrate, cobalt nitrate, nickel nitrate, and aluminum chloride). The procedure involves adding ammonium sulfate to the aqueous solution containing the above-mentioned metal ions to make it 0.5 mol / L, and then adding methanol to make it 44.5 wt%.

[0043] The initial weights of metal ions in the liquid, in the order of Li, Co, Ni, and Al, were 7.30 mg, 59.02 mg, 59.64 mg, and 28.17 mg. When this solution was mixed for 30 seconds using a general-purpose vortex mixer (NICHIRYO Vortex Mixer BV1000) and then allowed to stand for 30 minutes, cobalt and nickel crystallized into the solid phase and separated. The weights of the metal ions in the solution at this point were 7.44 mg, 4.48 mg, 5.87 mg, and 27.17 mg, respectively, for Li, Co, Ni, and Al.

[0044] After that, the mixture of crystallized cobalt and nickel was removed, and the resulting aqueous solution was stirred at 450 rpm for 150 minutes using a commercially available magnetic stirrer (HSH-6D, ASONE), and aluminum was crystallized in the solid phase, resulting in solid-liquid separation. The concentrations of Li, Co, Ni, and Al in the liquid phase at this time were 7.44 mg, 2.12 mg, 2.82 mg, and 4.53 mg, respectively, and the remaining liquid contained a large amount of Li, while the other metal species were successively separated into the solid phase. [Industrial Applicability]

[0045] The present invention can be suitably used in cases where it is desired to crystallize aluminum without using acid or alkali, including the removal of aluminum ions when separating and recovering lithium ions and transition metal ions from lithium ion batteries.

Claims

1. A method for separating an aluminum salt from an aqueous solution containing a metal salt including an aluminum salt, comprising the steps of: adding ammonium sulfate to the aqueous solution containing the metal salt; adding alcohol; stirring the resulting solution; The method includes a step of crystallizing an aluminum salt. Methods for separating aluminum salts.

2. 2. The method for separating aluminum salts according to claim 1, wherein the alcohol is one or a mixture of two or more selected from the group consisting of methanol, ethanol, and propanol.

3. 3. The method for separating aluminum salts according to claim 1 or 2, wherein the stirring speed in the stirring step is 200 rpm or more.

4. A method for separating transition metal salts, aluminum salts, and lithium salts from an aqueous solution containing these metals, comprising the steps of: adding ammonium sulfate to the aqueous solution and adding an alcohol to the aqueous solution, thereby precipitating a transition metal salt; The method for separating a metal salt further comprises a step of stirring the obtained aqueous solution, thereby precipitating an aluminum salt.

5. 5. The method for separating a metal salt according to claim 4, wherein the transition metal salt is at least one selected from the group consisting of nickel salts and cobalt salts.

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