Recovery method of resources

Abstract

To provide a recovery method of resources in which Li element included in waste liquid can be recovered as a resource while suppressing contamination of impurities.SOLUTION: A recovery method of resources has: a first step of adding first process liquid to waste liquid containing hydrophobic compound, alcohol compound and lithium alkoxide to separate the liquid into a first oil layer and a first water layer containing lithium ion, and recovering the first water layer; a second step of adding second process liquid containing solvent and lithium ion extraction agent to the first water layer to separate the liquid into a second oil layer containing lithium ion and a second water layer, and recovering the second oil layer; a third step of adding third process liquid being hydrogen chloride aqueous solution to the second oil layer to separate the liquid into a third oil layer and a third water layer containing lithium chloride, and recovering the third water layer; and a fourth step of drying the third water layer to obtain a solid component containing the lithium chloride.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a resource recovery method. [Background technology]

[0002] Information-related devices and communication devices such as personal computers, video cameras, and mobile phones are becoming widespread. Furthermore, from the perspective of reducing the burden on the environment, electric vehicles and other motor-driven vehicles are becoming more common. Accordingly, various studies are being conducted on the batteries used as power sources for these devices.

[0003] For example, Patent Document 1 discloses Si particles having a clathrate structure to be used as an active material and a method for producing the Si particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-098419 Summary of the Invention [Problem to be solved by the invention]

[0005] When producing materials for batteries, it is expected that waste liquid will be generated. Furthermore, such waste liquid may contain metallic elements such as Li. From the viewpoint of building a recycling-oriented society, it is desirable to recover the Li element contained in such waste liquid as a resource. Furthermore, it is preferable to prevent the inclusion of impurity elements in the recovery of Li element.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide a resource recovery method that can recover Li element contained in waste liquid as a resource while suppressing the inclusion of impurities. [Means for solving the problem]

[0007] [1] A resource recovery method for recovering resources from a waste liquid containing a hydrophobic compound, an alcohol compound, and a lithium alkoxide, comprising: a first step of adding a first treating liquid to the waste liquid to separate the waste liquid into a first oil layer and a first aqueous layer containing lithium ions, and recovering the first aqueous layer; a second step of adding a second treatment liquid containing a solvent and a lithium ion extractant to the first aqueous layer to separate the first aqueous layer into a second oil layer containing the lithium ions and a second aqueous layer, and recovering the second oil layer; a third step of adding a third treating liquid, which is an aqueous hydrogen chloride solution, to the second oil layer to separate the second oil layer into a third oil layer and a third aqueous layer containing lithium chloride, and recovering the third aqueous layer; a fourth step of drying the third aqueous layer to obtain a solid component containing lithium chloride.

[0008] [2] The resource recovery method according to [1], wherein the lithium ion extractant is at least one of a phosphoric acid extractant, an oxime extractant, a carboxylic acid extractant, and a neutral ligand extractant.

[0009] [3] The resource recovery method according to [1] or [2], wherein the ratio of the lithium ion extractant in the second treatment liquid is 10% by volume or more and 30% by volume or less.

[0010] [4] the first treatment liquid is an aqueous hydrogen chloride solution having a concentration of 3% by weight or less, The resource recovery method according to any one of [1] to [3], wherein the third treatment liquid is an aqueous hydrogen chloride solution having a concentration of 10% by weight or more.

[0011] [5] The resource recovery method according to any one of [1] to [4], wherein the waste liquid contains Si element. [Effects of the Invention]

[0012] The present disclosure has the effect of enabling elemental Li contained in the waste liquid to be recovered as a resource while suppressing the inclusion of impurities. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a flow diagram illustrating a resource recovery method of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] The resource recovery method according to the present disclosure will be described in detail below. FIG. 1 is a flow diagram illustrating the resource recovery method according to the present disclosure. As shown in FIG. 1, first, a first treatment liquid is added to a waste liquid containing a hydrophobic compound, an alcohol compound, and a lithium alkoxide. This separates the waste liquid into a first oil layer and a first aqueous layer containing lithium ions, and the first aqueous layer is recovered (first step). Next, a second treatment liquid containing a solvent and a lithium ion extractant is added to the first aqueous layer, separating the first aqueous layer into a second oil layer containing lithium ions and a second aqueous layer, and recovering the second oil layer (second step). Next, a third treatment liquid, which is an aqueous hydrogen chloride solution, is added to the second oil layer, separating the second oil layer into a third oil layer and a third aqueous layer containing lithium chloride, and recovering the third aqueous layer (third step). Finally, the third aqueous layer is dried to obtain a solid component containing lithium chloride (fourth step). In this specification, the lithium ion extractant may be simply referred to as the extractant.

[0015] In the resource recovery method disclosed herein, a third aqueous layer is recovered from a waste liquid containing a hydrophobic compound, an alcohol compound, and a lithium alkoxide through steps 1, 2, and 3. Then, by adding a third treatment liquid, which is an aqueous hydrogen chloride solution, to the third aqueous layer, lithium in the lithium alkoxide can be recovered as lithium chloride. Here, for example, it is considered possible to recover lithium chloride by directly adding an aqueous hydrogen chloride solution to the waste liquid, recovering the first aqueous layer as a lithium chloride-containing layer, and drying the first aqueous layer. On the other hand, it is conceivable that the waste liquid may contain metal elements other than Li, such as Si, as impurities. This may result in a high concentration of impurities in the first aqueous layer, leading to a high proportion of impurities in the recovered solid component. In contrast, in the recovery method disclosed herein, lithium ions in the lithium alkoxide are transferred to the first aqueous layer in step 1, to the second oil layer in step 2, and to the third aqueous layer in step 3. In other words, back-extraction of lithium ions is performed in steps 2 and 3. Therefore, impurities contained in the waste liquid can be separated into the second aqueous layer, and a third aqueous layer (lithium chloride-containing layer) with few impurities can be obtained. As a result, when the third aqueous layer is dried, a solid component (lithium chloride) with reduced impurity contamination is obtained.

[0016] Lithium chloride is a useful material in the manufacture of automobile parts. For example, lithium chloride is used as a flux in aluminum soldering. Lithium chloride is also used as a dehumidifier in air conditioners. Furthermore, elemental Li metal can be recovered from lithium chloride by molten salt electrolysis.

[0017] 1. Waste liquid The waste liquid in the present disclosure contains a hydrophobic compound, an alcohol compound, and a lithium alkoxide.

[0018] Examples of hydrophobic compounds include compounds having a benzene ring and compounds not having a benzene ring. Examples of compounds having a benzene ring include aromatic hydrocarbons such as 1,3,5-trimethylbenzene (mesitylene), toluene, xylene, ethylbenzene, propylbenzene, cumene, 1,2,4-trimethylbenzene, and 1,2,3-trimethylbenzene, as well as ethers (ethers having a benzene ring) such as diphenyl ether and methyl phenyl ether. Examples of compounds not having a benzene ring include saturated hydrocarbons such as n-heptane, n-octane, n-decane, 2-ethylhexane, and cyclohexane; unsaturated hydrocarbons such as hexene and heptene; and ethers (ethers not having a benzene ring) such as n-butyl ether, n-hexyl ether, isoamyl ether, diphenyl ether, methyl phenyl ether, and cyclopentyl methyl ether.

[0019] Examples of alcohol compounds include primary alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; secondary alcohols such as 2-propanol, 2-butanol, 2-pentanol, and 2-hexanol; and tertiary alcohols such as tert-butyl alcohol.

[0020] Examples of lithium alkoxides include compounds consisting of the anion of the above-mentioned alcohol compound and a lithium ion, such as lithium methoxide, lithium ethoxide, lithium isopropoxide, lithium tert-butoxide, and lithium tert-pentoxide.

[0021] The waste liquid may also contain Si element. The Si element may be contained in the waste liquid in the form of, for example, Si metal or Si compound. Examples of Si metal include simple Si metal and Si alloys such as Li-Si alloys. Examples of Si compounds include tetraethoxysilane.

[0022] The source of the waste liquid in the present disclosure is not particularly limited. For example, the waste liquid in the present disclosure may be waste liquid generated during the production of a battery active material. In particular, if the waste liquid contains Si element, the waste liquid may be waste liquid generated during the production of a Si-based active material.

[0023] 2.First step The first step is a step of adding a first treating liquid to the waste liquid, separating the waste liquid into a first oil layer and a first aqueous layer containing lithium ions, and recovering the first aqueous layer.

[0024] The first treatment liquid is not particularly limited as long as it can transfer lithium ions to the aqueous layer. Examples of the first treatment liquid include basic solutions and acidic solutions. Examples of basic solutions include metal hydroxide aqueous solutions such as sodium hydroxide aqueous solution, calcium hydroxide aqueous solution, and potassium hydroxide aqueous solution, as well as non-metal aqueous solutions such as ammonia aqueous solution. Examples of acidic solutions include hydrochloric acid (hydrogen chloride aqueous solution). Among these, hydrogen chloride aqueous solution is preferred.

[0025] The concentration of the aqueous hydrogen chloride solution (hydrochloric acid) is not particularly limited, but is preferably low. If the concentration of hydrochloric acid is too high, it may be difficult for the extractant to sufficiently extract lithium ions in the second step described below. The concentration of hydrochloric acid is, for example, 5.0 wt% or less, may be 3.0 wt% or less, or may be 1 wt% or less. On the other hand, the concentration of hydrochloric acid is, for example, 0.5 wt% or more, may be 0.7 wt% or more.

[0026] The amount of hydrochloric acid added can be adjusted appropriately depending on the amount of waste liquid and the concentration of the hydrochloric acid, but is, for example, a volume ratio of 1.0 to 10.0 relative to the waste liquid.

[0027] In the first step, the separated first oil layer may be distilled to recover a liquid component containing the hydrophobic compound or alcohol compound. In this way, the resource recovery method of the present disclosure can also recover hydrophobic compounds and the like contained in the waste liquid as resources.

[0028] 3.Second process The second step is a step of adding a second treatment liquid containing a solvent and a lithium ion extractant to the first aqueous layer to separate the first aqueous layer into a second oil layer containing the lithium ions and a second aqueous layer, and recovering the second oil layer. In the second oil layer, the lithium ions are usually present as a complex with the extractant described below.

[0029] The solvent is preferably a hydrophobic compound contained in the waste liquid, such as mesitylene.

[0030] The lithium ion extractant is not particularly limited as long as it is a treatment liquid that can transfer lithium ions to the oil layer (second oil layer), but it is preferable that it has high selectivity for lithium ions. This is because it can reduce the proportion of impurity elements in the oil layer. Examples of the extractant include at least one of phosphoric acid extractants, oxime extractants, carboxylic acid extractants, and neutral ligand extractants. Among these, phosphoric acid extractants are preferred. Among phosphoric acid extractants, mono-2-ethylhexyl (2-ethylhexyl)phosphonate is particularly preferred. This is because it has high selectivity for lithium ions.

[0031] The ratio of the extractant in the second treatment liquid is, for example, 8% by volume or more, or may be 10% by volume or more, 15% by volume or more, or 20% by volume or more, while the ratio of the extractant is, for example, 35% by volume or less, or may be 30% by volume or less.

[0032] The amount of the second treatment liquid added can be adjusted appropriately depending on the amount of the first aqueous layer and the ratio (concentration) of the extractant, and is, for example, a volume ratio of 1.0 to 10.0 relative to the first aqueous layer.

[0033] 4.Third step The third step is a step of adding a third treating liquid, which is an aqueous hydrogen chloride solution, to the second oil layer to separate the second oil layer into a third oil layer and a third aqueous layer containing lithium chloride, and recovering the third aqueous layer.

[0034] The concentration of the aqueous hydrogen chloride solution (hydrochloric acid) is not particularly limited, but a higher concentration is preferable in consideration of the reaction equilibrium. This is because the lithium ions contained in the second oil layer can be sufficiently transferred to the third aqueous layer as lithium chloride. The concentration of hydrochloric acid is, for example, 8.0 wt% or more, or may be 10.0 wt% or more, 15.0 wt% or more, or 20.0 wt% or more. On the other hand, the concentration of hydrochloric acid is, for example, 35.0 wt% or less, or may be 30.0 wt% or less.

[0035] The amount of the third treatment liquid added can be adjusted appropriately depending on the amount of the second oil layer and the proportion (concentration) of the hydrochloric acid, but is, for example, a volume ratio of 1.0 or more to 10.0 or less relative to the second oil layer.

[0036] 5. 4th step The fourth step is a step of drying the third aqueous layer to obtain a solid component containing the lithium chloride.

[0037] The drying conditions are not particularly limited as long as the solid component can be obtained from the third aqueous layer. In other words, the drying conditions are not particularly limited as long as water can be removed from the third aqueous layer. The drying temperature is, for example, 100°C or higher, and may be 120°C or higher, or 150°C or higher. On the other hand, the drying temperature is, for example, 200°C or lower. The drying time is, for example, 5 minutes or longer, may be 10 minutes or longer, or may be 30 minutes or longer, and on the other hand, the drying time is, for example, 1 hour or shorter.

[0038] Here, as shown in Figure 1, the liquid component contained in the third aqueous layer (lithium chloride-containing layer) may be recovered by the drying. That is, the drying may be performed by distillation. The liquid component is at least one of the alcohol compound and the hydrophobic compound.

[0039] The proportion of lithium chloride in the solid component is not particularly limited, but may be, for example, 70% by weight or more, or 90% by weight or more, while the proportion of lithium chloride in the solid component is, for example, 100% by weight or less, or may be 99% by weight or less, or may be 95% by weight or less.

[0040] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0041] [Example 1] Lithium chloride was recovered from the waste liquid according to the flow chart shown in Figure 1. Specifically, 40 ml of a solution (waste liquid) containing mesitylene (a hydrophobic compound), ethanol (an alcohol compound), lithium ethoxide (a lithium alkoxide), and silicon (an impurity element) was prepared. 80 ml of a 1 wt % hydrochloric acid solution (a first treatment liquid) was added to this solution, followed by shaking and standing. This separated the waste liquid into a first aqueous layer and a first oil layer.

[0042] Next, 50 ml of a second treatment liquid (extractant concentration 10% by volume) containing a solvent (mesitylene) and an extractant (mono-2-ethylhexyl (2-ethylhexyl)phosphonate) was added to the first aqueous layer, and the mixture was shaken and allowed to stand. This separated the first aqueous layer into a second aqueous layer and a second oil layer.

[0043] Next, 60 ml of a 10 wt % hydrochloric acid solution (third treated liquid) was added to the second oil layer, and the mixture was shaken and allowed to stand, thereby separating the second oil layer into a third water layer and a third oil layer.

[0044] [Example 2] The waste liquid was separated into a third aqueous layer and a third oil layer in the same manner as in Example 1, except that the concentration of the extractant in the second treated liquid was changed to 30% by volume.

[0045] [evaluation] The proportions of Li and Si elements contained in the first, second, and third water layers in Examples 1 and 2 were determined by ICP (inductively coupled plasma) analysis. The results are shown in Table 1. Note that for the first water layer, the same waste liquid was used and the same procedure was performed, so the same value is listed.

[0046] [Table 1]

[0047] As shown in Table 1, the concentration of impurity elements (Si element) in the third aqueous layer was low in both Examples 1 and 2. Since the third aqueous layer was obtained by adding hydrochloric acid to the second oil layer, the Li element in the third aqueous layer existed as lithium chloride. This indicated that high-purity lithium chloride could be obtained by drying the third aqueous layer. In particular, by increasing the concentration of the extractant, the proportion of lithium that migrated to the second aqueous layer could be reduced. In other words, the proportion of lithium that could be recovered in the second oil layer could be increased, and as a result, the proportion of Li element in the third aqueous layer could be increased. This confirmed that the recovery rate of Li element could be improved by increasing the concentration of the extractant in the second step.

Claims

1. A resource recovery method for recovering resources from a waste liquid containing a hydrophobic compound, an alcohol compound, and a lithium alkoxide, comprising: a first step of adding a first treating liquid to the waste liquid to separate the waste liquid into a first oil layer and a first aqueous layer containing lithium ions, and recovering the first aqueous layer; a second step of adding a second treatment liquid containing a solvent and a lithium ion extractant to the first aqueous layer to separate the first aqueous layer into a second oil layer containing the lithium ions and a second aqueous layer, and recovering the second oil layer; a third step of adding a third treating liquid, which is an aqueous hydrogen chloride solution, to the second oil layer to separate the second oil layer into a third oil layer and a third aqueous layer containing lithium chloride, and recovering the third aqueous layer; a fourth step of drying the third aqueous layer to obtain a solid component containing lithium chloride.

2. 2. The resource recovery method according to claim 1, wherein the lithium ion extractant is at least one of a phosphoric acid extractant, an oxime extractant, a carboxylic acid extractant, and a neutral ligand extractant.

3. The resource recovery method according to claim 1 , wherein the ratio of the lithium ion extractant in the second treatment solution is 10% by volume or more and 30% by volume or less.

4. the first treatment liquid is a hydrogen chloride aqueous solution having a concentration of 3% by weight or less, 2. The resource recovery method according to claim 1, wherein the third treatment liquid is an aqueous hydrogen chloride solution having a concentration of 10% by weight or more.

5. The resource recovery method according to any one of claims 1 to 4, wherein the waste liquid contains Si element.

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