JPH06279883A - Method for separating and recovering lithium - Google Patents

Abstract

PURPOSE:To obtain high-purity lithium at a high recovery rate at the time of separating and recovering lithium with the solvent extraction process by using a mixture of specified org. compds. as the extractant. CONSTITUTION:Lithium is extracted by solvent from an aq. lithium-contg. soln. such as a residual crystallization soln. of lithium carbonate and lithium phosphate in the lithium-related industries and a lithium-contg. waste water in the glass industry. In this case, a mixture of alpha-perfluoroalkanoyl-m- dodecylacetophenone and tri-n-butyl phosphate is used as the extractant. In this case, an aq. lithium soln. is advantageously kept at pH7-12.5. Lithium is extracted at a high rate by the synergistic effect of both compds. and recovered, the water phase and org. phase are extremely easily separated after extraction, and lithium is stable in repeated use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for separating and recovering lithium from an aqueous solution containing lithium. More specifically, the present invention provides high recovery by a solvent extraction method from a lithium-containing aqueous solution, for example, a lithium carbonate crystallization residual liquid in a lithium-related industry, a lithium phosphate crystallization residual liquid, or a contained wastewater in the glass manufacturing industry. The present invention relates to an economically advantageous method for separating and recovering lithium that yields high-purity lithium at a high rate.

[0002]

2. Description of the Related Art Separating and recovering lithium from lithium carbonate crystallization residual liquid or lithium phosphate crystallization residual liquid in the lithium-related industry, or lithium-containing wastewater in the glass manufacturing industry is effective resource utilization. It's important.

Separation of lithium from an aqueous solution containing lithium,
A solvent extraction method is usually used as a method of recovery. Mixtures of various β-diketones and neutral organic phosphoric acids have been used as extraction agents for separating and recovering lithium by this solvent extraction method [Analytical Chemistry, page 1506 (1974). ), "Journal of the Japan Institute of Metals", page 82 (1975), "Chemical Engineering Papers"
857 (1989), "Chemical Engineering Papers", 504 (1989)].

However, in such a conventional extractant, it is difficult to separate it from a homologous alkali metal element, and high-purity lithium cannot be recovered.
Due to repeated use of the extractant, the extractant is lost and the extraction rate is lowered.

As described above, the conventional method for separating and recovering lithium by the solvent extraction method has not been sufficiently satisfactory in terms of technology and economically. Therefore, there is a method capable of efficiently extracting lithium by a simple operation. It was requested.

[0006]

Under the circumstances described above, the present invention provides separation and recovery of lithium from a lithium-containing aqueous solution by a solvent extraction method with high recovery rate and high-purity lithium. The purpose is to provide a method.

[0007]

The inventors of the present invention have conducted various studies on solvent extraction of lithium, and as a result, a mixture of α-perfluoroalkanoyl-m-dodecylacetophenone and tri-n-butyl phosphate was found to be It has been found that it has a high extraction rate with respect to lithium and excellent selectivity, and is stable against repeated use, and that the object can be achieved by using a mixture, and the present invention is based on this finding. It came to completion.

That is, the present invention is characterized by using a mixture of α-perfluoroalkanoyl-m-dodecylacetophenone and tri-n-butyl phosphate as an extractant in extracting lithium in an aqueous solution containing lithium. The present invention provides a method for separating and recovering lithium.

In the method for separating and recovering lithium according to the present invention, α-perfluoroalkanoyl-m is used as an extractant.
It is necessary to use a mixed extractant of -dodecylacetophenone and tri-n-butyl phosphate. The α-perfluoroalkanoyl-m-dodecylacetophenone is
It is available as a commercially available product X1-51 (trade name, manufactured by Henkel).

When lithium is extracted using only the α-perfluoroalkanoyl-m-dodecylacetophenone, an extraction rate of 85 to 95% can be obtained in the pH range of 10.5 to 12.5. A white viscous substance is formed, and it is extremely difficult to separate the aqueous phase and the organic phase. On the other hand, when the extraction treatment is performed using only tri-n-butyl phosphate, the lithium extraction rate is as low as 35% or less in the entire alkaline region.

On the other hand, the mixture of α-perfluoroalkanoyl-m-dodecylacetophenone and tri-n-butyl phosphate used in the present invention has a synergistic effect in the range of pH 10.0 to 12.5. An extraction rate of 99% or more is obtained, and it is extremely easy to separate the aqueous phase and the organic phase after the extraction treatment, and it is stable against repeated use.

Α-Perfluoroalkanoyl-m-dodecylacetophenone and tri-n phosphate in the mixture
With regard to the mixing ratio with -butyl, it was confirmed that the extraction chemical species of lithium was Li.α-perfluoroalkanoyl-m-dodecylacetophene tri-n-butyl diphosphate, so α-perfluoroalkanoyl- m
The molar ratio of -dodecyl acetophenone and tri-n-butyl phosphate may be substantially 1: 2.

In the method of the present invention, it is advantageous to adjust the pH of the lithium-containing aqueous solution used for the extraction treatment within the range of 7 to 12.5.

In the method of the present invention, an organic solvent is usually used together with the mixture. The type of the organic solvent is not particularly limited, and examples thereof include kerosene, cyclohexane and p-xylene such as α-perfluoro-m.
-Dodecylacetophenone and tri-n-butyl phosphate can be dissolved and immiscible with water, but kerosene is preferable from the viewpoint of being inexpensive and immiscible with water. Regarding the concentration of the mixture in the mixed liquid of the mixture and the organic solvent, the concentration of α-perfluoro-m-dodecylacetophenone is preferably in the range of 0.01 to 1M.

In the extraction treatment of the present invention, the mixture of the mixture and the organic solvent is used in a proportion of 10 to 1000 parts by volume, preferably 30 to 300 parts by volume, relative to 100 parts by volume of the lithium-containing aqueous solution. Is desirable.

Lithium and other alkali metal elements can be separated by appropriately adjusting the pH of the aqueous lithium solution during the extraction treatment, but the organic phase of the extraction treatment is 0.1%.
By washing with a dilute acid solution having a concentration of M or less, about 90% of coexisting sodium can be easily removed. In addition, the lithium in the organic phase after the extraction treatment as described above, and optionally after washing with a dilute acid solution having a concentration of 0.1 M or less, is back-extracted with a mineral acid solution having a concentration of 1 M or more. By doing so, it can be quantitatively recovered. In this back extraction treatment, the mineral acid solution is used usually in a ratio of 1 to 100 parts by volume, preferably 3 to 50 parts by volume, relative to 100 parts by volume of the organic layer.

By such treatment, the lithium concentration can be concentrated to about 10 times that of the stock solution.

[0018]

INDUSTRIAL APPLICABILITY The mixture used in the present invention has a stronger affinity for lithium than that for other alkali metal elements, and therefore it is possible to separate lithium from other alkali metals. In addition, the mixture shows almost no deterioration in extraction performance even after repeated use.

Therefore, according to the method of the present invention using the mixture, an aqueous solution containing lithium, for example, a lithium carbonate crystallization residual liquid, a lithium phosphate crystallization residual liquid, a lithium solution recovered from a used lithium battery, or the like is used. High-purity lithium can be efficiently and economically separated and recovered from various lithium-containing aqueous solutions in industry or lithium-containing wastewater in the glass manufacturing industry.

[0020]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 α-perfluoroalkanoyl-m-dodecylacetophenone (Henkel: X1-51, trade name) and tri-n-butyl phosphate (hereinafter abbreviated as TBP) were dissolved in kerosene, A 0.1 M solution was prepared for each. Further, 1 volume part of 0.1MX1-51 kerosene solution and 0.
1 MTBP kerosene solution mixed solution with 2 parts by volume (hereinafter,
A 0.1 M mixture solution was prepared). The extractability of lithium when these three types of extractants were used was investigated. Further, as the lithium-containing aqueous solution, one prepared by dissolving lithium chloride in water to adjust the lithium concentration to 31 mM was used.

5 ml of the lithium-containing aqueous solution and 0.2M
5 ml of the various buffer solutions described above were mixed to prepare a sample solution having a pH of 6 to 13.5. 10 ml of this sample solution and 10 ml of the above three kinds of extractant solutions were placed in a 100 ml Erlenmeyer flask, horizontal shaking was performed 100 times per minute with an amplitude of 3 cm for 15 minutes, and lithium in the aqueous phase was extracted into the organic phase. .

The lithium concentration in the aqueous phase before and after the treatment was quantified by atomic absorption spectrometry, and the extraction rate was calculated from the difference. The relationship between the pH after extraction and the extraction rate of lithium is shown in FIG.

In the case of X1-51, the extractability was exhibited at pH 9 or higher, but the extraction rate was 95% or lower. Moreover, a white viscous substance was generated after the extraction treatment, and this was mixed in the aqueous phase and the organic phase, and it was extremely difficult to separate both phases. Use a centrifuge to separate both phases at 3000 rpm for 10
It was processed for 1 minute. In the case of TBP, the extraction efficiency of lithium is 35% or less and the extraction efficiency is poor.

In the case of a mixture solution, pH 10-12.
In a wide range of 5, an extraction rate of 99% or more was obtained.
Further, the separation of both phases after the extraction treatment was possible by allowing the mixture to stand for a few seconds, which was extremely easy. Thus, the synergistic effect of the mixture of the present invention is clear and is a useful solvent extraction method for lithium.

Example 2 The extraction performance of lithium with a 0.1 M mixture solution was investigated. Lithium concentration 2-142mM aqueous solution 5ml
And pH 12 buffer solution 5 ml and 0.1 M mixture solution 1
0 ml was placed in an Erlenmeyer flask, and an extraction experiment was conducted under the same conditions as in Example 1. The relationship between the lithium concentration and the extraction rate at that time is shown in FIG.

As is clear from this result, an extraction rate of 99% or more was obtained at a lithium concentration of 16 mM or less.
Practically, it is desirable to change the mixture concentration according to the lithium concentration.

Example 3 The separability between lithium and the same kind of alkali metal element was investigated. 5 ml of 5 mM aqueous solutions of lithium, sodium, potassium, rubidium and cesium, 5 ml of 0.2 M various buffer solutions and 10 ml of 0.1 M mixture solution were placed in an Erlenmeyer flask, and an extraction experiment was performed under the same conditions as in Example 1. . The relationship between the pH and the extraction rate of each element at that time is shown in FIG.

Sodium, potassium, rubidium and cesium show extractability from pH 9.5, and their maximum extraction rates are 80% sodium, 42% potassium and 2 rubidium.
It was 3% and cesium 21%. On the other hand, lithium has a pH of 6
In the above, the extractability was exhibited, and particularly at pH 10 to 12.5, the extraction rate was 99% or more.

As described above, it is considered that the mixture solution has a high extraction rate for lithium in a wide pH range and has a higher affinity than other elements. Therefore, separation is possible by adjusting the extraction pH according to the type of coexisting alkali metal element. For example, at pH 9, extraction of other alkali metal elements is almost eliminated, only about 90% of lithium can be extracted, and high-purity lithium can be obtained.

Example 4 In Example 3, the separability of lithium and other alkali metal elements by extraction pH was examined. However, the mixture solution of the present invention has a strong affinity for sodium as well as lithium. Therefore, when a large amount of sodium coexisting aqueous solution (for example, lithium carbonate crystallization residual liquid) is subjected to extraction treatment at pH 9.5 or higher, sodium is also extracted at the same time. Therefore, the removal of sodium coexisting in the organic phase, that is, the washing condition of the solvent phase was examined.

20 ml of a 8.0 mM lithium concentration solution, 20 ml of a 193 mM sodium concentration solution (including a sodium buffer solution) and 40 ml of a 0.1 M mixture solution were placed in an Erlenmeyer flask, and an extraction experiment was conducted under the same conditions as in Example 1. . The pH after extraction was 10.0, and the extraction rate of each element was 97% lithium and 18% sodium. Therefore, in the organic phase, lithium 3.9 mM, sodium 1
It contains 7.4 mM.

10 parts by volume of this organic phase sample solution and 0.08
Example 1 was prepared by placing 1 volume part of M hydrochloric acid solution in an Erlenmeyer flask.
It was shaken for 60 minutes under the same shaking conditions as described above. After shaking, 10 parts by volume of the organic phase and 1 part by volume of a fresh 0.08 M hydrochloric acid solution were placed again in an Erlenmeyer flask and shaken under the same conditions.
This solvent phase washing operation was repeated three times. FIG. 4 shows the changes in the lithium and sodium concentrations in the organic phase and the sodium removal rate at that time.

As is clear from FIG. 4, the concentration of sodium in the organic phase was reduced from 17.4 mM to 1.6 mM by the two washing treatments, and the removal rate was about 90%. On the other hand, the lithium concentration in the organic phase hardly changed during the washing treatment up to twice. However,
It was found that three washing treatments led to back extraction into the aqueous phase. Thus, most of the coexisting sodium was able to be removed by the appropriate washing treatment of the solvent phase, and the purification effect of lithium was obtained.

Example 5 The back extraction conditions were examined for a sample solution having a lithium concentration of 5.1 mM in the organic phase. 10 volume parts of the sample solution and 1 volume part of hydrochloric acid solution having various concentrations were placed in an Erlenmeyer flask and shaken for 60 minutes under the same conditions as in Example 1. The lithium concentration in the hydrochloric acid solution at that time was quantified by an atomic absorption method to obtain the back extraction rate. The result is shown in FIG.

At a hydrochloric acid concentration of 0.5 M or less, the back extraction rate is 96.
% Or less, a back extraction rate of 99% or more was obtained at 1 M or more. Thus, the back extraction of lithium from the organic phase could be performed quantitatively. In addition, this process
The lithium concentration can be concentrated about 10 times. Practically, it is desirable to further increase the ratio of the organic phase volume to the hydrochloric acid volume. As a result of studying the back extraction time, it was found that the extraction equilibrium was reached when the shaking time was 40 minutes or more when the organic phase was 10 parts by volume and the hydrochloric acid solution was 1 part by volume.

Example 6 Changes in extraction performance due to repeated use of the mixture solution were investigated. First, in Example 5, using the organic phase (0.1 M mixture solution) after back-extracting with a 1 M hydrochloric acid solution, the extraction performance was determined for solutions with various lithium concentrations as in Example 2. As a result, there is no change from Figure 2,
No decrease in extraction performance was observed.

Next, the lithium concentration was 16 mM (extraction rate 99
%) (Maximum concentration at which%) was obtained, the same extractant solution was repeatedly used, and extraction-back extraction was performed 7 times. The results of obtaining the extraction rate and the back extraction rate in the process are shown in FIG.

Extraction from an aqueous solution gave an extraction rate of 97% or more even after repeated use 7 times. In addition, the back extraction rate was quantitative and good results were obtained.

As described above, the mixture of the present invention is considered as a lithium extractant which is extremely promising economically, because it is possible to use it repeatedly semipermanently.

Example 7 Recovery of lithium from the lithium carbonate crystallization residual liquid was examined. Lithium 0.22 was used as the crystallization residual liquid used in the experiment.
M and sodium 1.28M were contained, and sodium was about 6 times the coexisting amount of lithium.

This solution was diluted with water to about 8 times, and p
It was adjusted to H9.1. This sample solution (lithium concentration 28
mM, sodium concentration 160 mM) 10 ml and 0.1 M
20 ml of the mixture solution was placed in an Erlenmeyer flask, and Example 1 was used.
An extraction experiment was conducted under the same conditions as above. The pH after extraction is 8.
8, the extraction rate of lithium was 84% and the extraction rate of sodium was 0%.

Next, 5 ml of the aqueous solution (lithium concentration: 4.6 mM) after the extraction treatment and 5 ml of the 0.1 M mixture solution were placed in an Erlenmeyer flask, and the extraction treatment was performed again under the same conditions as in Example 1. The pH after extraction was 8.7, and the extraction rate of lithium was 80%. The extraction rate of lithium from the sample solution reached 97% by the two extraction treatments. Furthermore, this extraction treatment made it possible to completely separate sodium and lithium that coexist in large amounts.

Example 8 Recovery of lithium from lithium-containing wastewater in the glass manufacturing industry was examined. PH of sample solution is 7.2
It is a concentrated aqueous sodium solution containing 8.7 mM lithium and 4.0 M sodium.

20 ml of this solution was placed in an Erlenmeyer flask,
Add 1 ml of 1M sodium hydroxide solution to pH 12.
Adjusted to 5. Furthermore, 20 ml of a 0.1 M mixture solution was added, and an extraction experiment was conducted under the same conditions as in Example 1. The pH after extraction was 9.1, the lithium extraction rate was 82%, and the sodium extraction rate was 1% or less.

Next, 10 ml of the extracted organic phase was placed in an Erlenmeyer flask, 1 ml of a 1M hydrochloric acid solution was added thereto, and a back extraction experiment was conducted under the same conditions as in Example 5. As a result, the back extraction rate was 99%, and lithium could be quantitatively recovered from the organic phase.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the pH after extraction of a lithium-containing aqueous solution and the lithium extraction rate in various lithium extraction agents.

FIG. 2 is a graph showing the relationship between lithium concentration and lithium extraction rate.

FIG. 3 is a graph showing the relationship between pH and extraction rate for various alkali metal elements.

FIG. 4 is a graph showing the removability of sodium by washing the solvent phase.

FIG. 5 is a graph showing the relationship between hydrochloric acid concentration and lithium back extraction rate.

FIG. 6 is a graph showing the relationship between the number of times the extractant is repeatedly used and the lithium extraction rate and lithium back extraction rate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Feng Qi, 2-3-3 Hananomiya-cho, Takamatsu City, Kagawa Prefecture Shikoku Institute of Industrial Technology Laboratory

Claims (4)

[Claims] 1. Separation of lithium, characterized in that a mixture of α-perfluoroalkanoyl-m-dodecylacetophenone and tri-n-butyl phosphate is used as an extractant for extracting lithium in an aqueous solution containing lithium. , Recovery method. 2. A lithium-containing aqueous solution having a pH of 7 to 12.5.
The method for separating and recovering lithium according to claim 1, wherein the extraction treatment is carried out after adjusting to. 3. The organic phase obtained by the extraction treatment is 0.1M.
The method for separating and recovering lithium according to claim 1 or 2, which is washed with a dilute acid solution having the following concentration. 4. The method for separating and recovering lithium according to claim 1, 2 or 3, wherein lithium in the organic phase obtained by the extraction treatment is back-extracted with a mineral acid solution having a concentration of 1 M or more.