JP-7854707-B2 - Method for separating metal salts

Inventors

• 高橋 博
• 鈴木 勝彦
• 渡慶次 聡
• 河合 展夫

Assignees

• 国立大学法人秋田大学

Dates

Publication Date

20260507

Application Date

20220518

Claims (6)

1. A method for separating a rare earth metal from an aqueous solution containing the rare earth metal, The process comprises adding ammonium sulfate to an aqueous solution containing the rare earth metal, adding alcohol, and crystallizing a salt of the rare earth metal. The concentration of each rare earth metal in the aqueous solution containing the rare earth metals is 100 ppm or less. Methods for separating metal salts.
2. The method for separating metal salts according to claim 1, wherein the aqueous solution containing the rare earth metal contains an acid.
3. The method for separating metal salts according to claim 1 or 2, wherein the alcohol is one or a mixture of two or more alcohols selected from methanol, ethanol, and propanol.
4. The method for separating metal salts according to claim 1 or 2 , wherein the concentration of ammonium sulfate is 2 mol/L or less .
5. The separation method according to claim 1 or 2 , wherein the rare earth metal is one or more selected from the group consisting of neodymium, samarium, terbium, dysprosium, and erbium.
6. The separation method according to claim 1 or 2 , wherein the aqueous solution containing the rare earth metal is an aqueous solution obtained by acid leaching of seabed surface sediments.

Description

This invention relates to a method for separating metal salts. For Japan, which currently does not produce rare earth ores, establishing recycling technology for rare earth metals is an urgent task. While existing technologies can be applied to recover rare earth metals present in relatively high concentrations in solutions, handling low-concentration solutions (around 100 ppm or less) is complicated, costly, and difficult with existing technologies. Therefore, the development of a simple and low-cost method for separating and concentrating low-concentration resources is desirable. The inventors have previously developed a technology to efficiently separate and recover metal ion-containing aqueous solutions into a solid phase by changing their solubility using methanol and ammonium sulfate (Patent Document 1), but faced the same problems as described above. In particular, for Japan, an island nation, there is a strong need for the development of simple and low-cost methods for separating and concentrating low-concentration resources from seafloor surface sediments (so-called seafloor mud), which are considered a promising resource. Japanese Patent Publication No. 2021-37438 This is a flowchart illustrating an example of an embodiment of the metal salt separation method of the present invention.This graph shows the results of Example 1. <Method for separating metal salts> The present invention relates to a method for separating metal salts, which is a method for separating rare earth metals from an aqueous solution containing rare earth metals, comprising the steps of adding ammonium sulfate, adding alcohol, and crystallizing the metal salt to the aqueous solution containing the rare earth metals, wherein the concentration of each rare earth metal in the aqueous solution containing the rare earth metals is 100 ppm or less. Figure 1 shows a flowchart illustrating an example of an embodiment of the metal salt separation method of the present invention. Normally, methods utilizing crystallization result in residual liquid near saturation concentration, which can leave some of the target material remaining. However, the rare earth metal separation method of the present invention achieves highly efficient separation even at low concentrations of the target material, and since almost all of it precipitates in the solid phase, the separation efficiency and the solid phase recovery rate of the component of interest are extremely high. Even in solutions containing the target substance at low concentrations, the relative concentration in the solid phase increases when the majority of the target substance is converted into a solid phase, making handling easier in subsequent separation operations. While existing technologies have shown separation effectiveness in regions where the concentration of the target to be separated is relatively high, this invention newly demonstrates that the separation effect is also effective for solutions with a target concentration of 100 ppm or less. This provides a new avenue for the effective utilization of rare earth elements, which have not been utilized despite their high resource value, and represents a significant contribution of the present invention. (Aqueous solution containing rare earth metals) The aqueous solution containing rare earth metals is not particularly limited as long as it is an aqueous solution in which the rare earth metal to be separated is dissolved. It may be a solution prepared by dissolving a metal salt of a rare earth metal in water, or it may be an acid leachate obtained by leaching a solid containing a rare earth metal and/or a metal salt of a rare earth metal with an acid such as sulfuric acid or hydrochloric acid. Furthermore, it may contain one or more rare earth metals. It may also contain metals other than rare earth metals and/or metal salts thereof. In this invention, examples of rare earth metals to be separated include scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, cadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, cadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium are preferred, and neodymium, samarium, terbium, dysprosium, and erbium are more preferred. Besides rare earth metals, other metals include common base metals such as iron, magnesium, copper, and lead, as well as rare metals such as lithium, beryllium, rubidium, strontium, indium, cesium, barium, thallium, bismuth, thorium, and uranium. The concentration of each rare earth metal in the aqueous solution is 100 ppm or less, preferably 80 ppm or less, more preferably 50 ppm or less, even more preferably 35 ppm or less, even more preferably 15 ppm or less, even more preferably 5.0 ppm or less, particularly preferably 1.0 ppm or less, and most preferably 0.10 ppm or less. The concentration of me