Resource recovery methods

Abstract

To provide a method for collecting a resource from a waste liquid containing lithium (Li) as a resource.SOLUTION: The present disclosure provides a method for collecting a resource from a waste liquid containing a hydrophobic compound, an alcohol compound, and a lithium alkoxide, comprising: a first step of adding hydrogen chloride to the waste liquid to obtain a lithium chloride-containing phase; and a second step of drying the lithium chloride-containing phase to obtain a lithium chloride-containing solid component.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 perspective of building a recycling-oriented society, it is desirable to recover the Li element contained in such waste liquid as a resource.

[0006] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a resource recovery method that can recover elemental Li contained in waste liquid as a resource. [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 the steps of: a first step of adding hydrogen chloride to the waste liquid to obtain a lithium chloride-containing phase; a second step of drying the lithium chloride-containing phase to obtain a solid component containing lithium chloride.

[0008] [2] The resource recovery method according to [1], wherein in the first step, the hydrogen chloride is added to the waste liquid in the form of an aqueous solution.

[0009] [3] The resource recovery method according to [2], wherein the concentration of the hydrogen chloride in the aqueous solution is 10% by weight or more.

[0010] [4] The resource recovery method according to [1], wherein in the first step, the hydrogen chloride is added in a gaseous state to the waste liquid.

[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 the Li element contained in the waste liquid to be recovered as a resource. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a flow diagram illustrating a resource recovery method of the present disclosure. [Figure 2] FIG. 1 is a flow diagram illustrating a resource recovery method of the present disclosure. [Figure 3] 1 shows the results of XRD measurements in Examples and Comparative Examples. [Figure 4] 1 shows the results of XRD measurements in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] The resource recovery method of the present disclosure will be described in detail below.

[0015] 1 and 2 are flow diagrams illustrating a resource recovery method according to the present disclosure. As shown in FIGS. 1 and 2, in the resource recovery method according to the present disclosure, first, hydrogen chloride is added to a waste liquid containing an alcohol compound and a lithium alkoxide to obtain a lithium chloride-containing phase (first step). Then, the lithium chloride-containing phase is dried to obtain a solid component containing lithium chloride (second step).

[0016] According to the present disclosure, by adding hydrogen chloride to a waste liquid containing a hydrophobic compound, an alcohol compound, and a lithium alkoxide, it is possible to recover lithium in the lithium alkoxide as lithium chloride.

[0017] Lithium chloride is a useful material in the manufacture of automotive parts. For example, it is used as a flux in aluminum soldering. It is also used as a dehumidifier in air conditioners. Elemental Li metal can also be recovered from lithium chloride by molten salt electrolysis.

[0018] 1. Waste liquid The waste liquid in the present disclosure contains a hydrophobic compound, an alcohol compound, and a lithium alkoxide.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The waste liquid may also contain an acid, such as a carboxylic acid, such as acetic acid, formic acid, or propionic acid, or a dicarboxylic acid, such as oxalic acid.

[0024] 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, when the waste liquid contains Si element, the waste liquid may be waste liquid generated during the production of a Si-based active material.

[0025] 2.First step The first step in the present disclosure is to add hydrogen chloride to the waste liquid to obtain a lithium chloride-containing phase. The lithium alkoxide reacts with hydrogen chloride to recover lithium from the lithium alkoxide as lithium chloride.

[0026] The hydrogen chloride may be added to the waste liquid in the form of an aqueous solution. In other words, in the first step, hydrochloric acid may be added to the waste liquid.

[0027] The concentration and amount of hydrochloric acid added are not particularly limited as long as the lithium alkoxide in the waste liquid and HCl can react sufficiently. The concentration of hydrochloric acid may be, for example, 3.0 wt% or more, 5.0 wt% or more, 10.0 wt% or more, 12.5 wt% or more, or 15.0 wt% or more. On the other hand, the concentration of hydrochloric acid may be, for example, 35.0 wt% or less, 30.0 wt% or less, 25 wt% or less, or 20.0 wt% or less. In consideration of reaction equilibrium, a higher concentration of hydrochloric acid is more preferable. As shown in the examples described below, by increasing the hydrochloric acid concentration, a solid component with a higher lithium chloride purity can be recovered in the second step.

[0028] 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.

[0029] Alternatively, hydrogen chloride may be added to the waste liquid in a gaseous state, i.e., in the first step, hydrochloric acid gas may be added to the waste liquid.

[0030] Here, when the waste liquid does not contain the above-mentioned acid, adding hydrogen chloride to the waste liquid can separate the waste liquid into an oil layer containing a hydrophobic compound and an aqueous layer containing an alcohol compound and lithium chloride, as shown in FIG. 1. In this case, the aqueous layer can be recovered as a lithium chloride-containing phase. On the other hand, as shown in Example 2-1 described later, when the waste liquid contains an acid, adding hydrogen chloride to the waste liquid may make it difficult to sufficiently separate the waste liquid into the oil layer and the aqueous layer. In this case, as shown in FIG. 2, the liquid layer in the waste liquid to which hydrogen chloride has been added can be recovered as a lithium chloride-containing phase, and the process can proceed to the second step described later. On the other hand, in the second step, the lithium chloride-containing phase is dried, so it is preferable that the volume of the lithium chloride-containing phase is small. Therefore, when the waste liquid contains an acid, hydrogen chloride is preferably added as hydrogen chloride gas rather than as hydrochloric acid (aqueous hydrogen chloride solution).

[0031] The lithium chloride-containing phase usually contains at least the alcohol compound described above in addition to lithium chloride, and may also contain the hydrophobic compound and the acid described above.

[0032] 3.Second process The second step in the present disclosure is a step of drying the lithium chloride-containing phase to obtain a solid component containing lithium chloride.

[0033] The drying conditions are not particularly limited as long as a solid component can be obtained from the lithium chloride-containing phase. In other words, the drying conditions are not particularly limited as long as the liquid can be removed from the lithium chloride-containing phase. 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.

[0034] 1 and 2, in the second step, a liquid component contained in the lithium chloride-containing phase may be recovered by the drying. That is, the drying may be distillation. The liquid component is at least one of the alcohol compound, the hydrophobic compound, and the acid. In this way, the resource recovery method of the present disclosure can also recover liquid components, such as hydrophobic compounds, contained in the waste liquid as a resource.

[0035] The proportion of lithium chloride in the solid component is not particularly limited, but is preferably high. The proportion of lithium chloride in the solid component is, for example, 50% by weight or more, or may be 70% by weight or more, or may be 90% by weight or more. On the other hand, 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.

[0036] 4. Other processes In the resource recovery method of the present disclosure, if the first step is a step of separating the waste liquid into an aqueous layer and an oil layer by adding the hydrogen chloride, and the aqueous layer is the lithium-containing phase, the method may further include a third step of distilling the oil layer to recover at least one of the hydrophobic compound and the alcohol compound. The distillation conditions in the third step, such as the heating temperature, can be appropriately adjusted depending on the types of hydrophobic compound and alcohol compound contained in the waste liquid.

[0037] 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]

[0038] [Example 1-1] Lithium chloride was recovered from the waste liquid according to the flow chart shown in Figure 1. Specifically, 5 ml of a solution (waste liquid) containing mesitylene, ethanol, and lithium ethoxide was first prepared. To this solution, 10 wt% hydrochloric acid (hydrogen chloride aqueous solution) was added in a volume ratio of 1:1, followed by shaking and standing. This separated the waste liquid into an oil layer and an aqueous layer (lithium chloride-containing phase). The aqueous layer was recovered and heated to 100°C, causing the solid component (white powder) to precipitate.

[0039] [Example 1-2] A white powder was obtained in the same manner as in Example 1, except that the concentration of hydrochloric acid was changed to 20% by weight.

[0040] [Comparative Example 1-1] Without using hydrochloric acid, the prepared waste liquid was dried to obtain a white powder.

[0041] [evaluation] The white powders obtained in Examples 1-1 and 1-2 and Comparative Example 1-1 were subjected to X-ray diffraction measurement (XRD measurement), and the results are shown in FIG.

[0042] As shown in FIG. 3, no peak of lithium chloride (LiCl) was observed in Comparative Example 1-1. On the other hand, a peak of LiCl was observed in all Examples. This confirmed that lithium chloride can be recovered from waste liquid by the method of the present disclosure. Furthermore, in Example 1-2, no peaks other than LiCl were observed compared to Example 1-1, suggesting that high-purity LiCl can be recovered by sufficiently increasing the concentration of hydrochloric acid. The peaks of Si compounds observed in Example 1-1 are presumed to be peaks of, for example, lithium silicate (Li4SiO4) and lithium disilicate (Li2SiO2O5).

[0043] In Example 1-1, the proportions of elemental Li contained in the prepared waste liquid, the separated oil layer, and the separated aqueous layer were confirmed by ICP (inductively coupled plasma) analysis. As a result, the proportions of elemental Li were 3891 ppm in the waste liquid, less than 10 ppm in the oil layer, and 3538 ppm in the aqueous layer. This confirmed that, in Example 1-1, the addition of hydrochloric acid allowed most of the elemental Li in the waste liquid to be transferred to the aqueous layer and recovered. Similarly, the proportion of elemental Si was also confirmed by ICP analysis. As a result, the proportions of elemental Si were 1419 ppm in the waste liquid, less than 5 ppm in the oil layer, and 1380 ppm in the aqueous layer. From this, it is presumed that when the concentration of hydrochloric acid is low, the elemental Si in the waste liquid is also drawn into the aqueous layer and precipitates as an impurity together with LiCl when dried.

[0044] [Example 2-1] Lithium chloride was recovered from the waste liquid based on the flow shown in Figure 2. Specifically, first, acetic acid was added to the waste liquid prepared in Example 1-1 above to prepare an acid-containing waste liquid. Hydrochloric acid with a concentration of 10 wt% was added to the acid-containing waste liquid at a volume ratio of 1:1, and the mixture was shaken and allowed to stand. After standing, the waste liquid separated into a liquid lower layer (liquid layer) and a gel-like upper layer (solid layer). The lower layer was recovered as a lithium chloride-containing phase and heated at 120°C for 20 minutes. This caused a white powder to precipitate.

[0045] [Comparative Example 2-1] A white powder was precipitated in the same manner as in Example 2-1, except that water was added instead of hydrochloric acid.

[0046] [evaluation] The white powders obtained in Example 2-1 and Comparative Example 2-1 were subjected to X-ray diffraction measurement (XRD measurement). The results are shown in Figure 4. Note that Figure 4 also shows the results of XRD measurement of the waste liquid used as reference data.

[0047] As shown in Fig. 4, no lithium chloride peak was observed in Comparative Example 2-1, but a lithium chloride peak was observed in Example 2-1. This confirmed that lithium chloride can be recovered by the method of the present disclosure even when the waste liquid contains acid (acetic acid). Note that in Example 2-1, a peak presumably corresponding to lithium silicate was observed near 2θ = 33°, as in Example 1-1. However, it is presumed that by increasing the hydrochloric acid concentration as in Example 1-2, lithium chloride with higher purity can be recovered.

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 the steps of: a first step of adding hydrogen chloride to the waste liquid to obtain a lithium chloride-containing phase; a second step of drying the lithium chloride-containing phase to obtain a solid component containing lithium chloride.

2. 2. The resource recovery method according to claim 1, wherein in the first step, the hydrogen chloride is added to the waste liquid in the form of an aqueous solution.

3. 3. The resource recovery method according to claim 2, wherein the concentration of the hydrogen chloride in the aqueous solution is 10% by weight or more.

4. 2. The resource recovery method according to claim 1, wherein in the first step, the hydrogen chloride is added to the waste liquid in a gaseous state.

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

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