JPS6240327A - Separation of ion - Google Patents

Abstract

PURPOSE:To recover by separation an alkali-metal ion with higher atomic number by occlusion in a compound mentioned below, by subjecting an iron cyanide compound to electrolytic reduction in an aqueous solution containing several alkali-metal ions. CONSTITUTION:A platinum-plate electrode on which the iron cyanide compound such as Prussian blue etc., is electrodeposited is dipped in the aqueous solution containing several alkali-metal ions, to which a reduction current is sent by use of a platinum wire as a counter electrode to carry out electrolytic reduction. Subsequently, the above platinum-plate electrode is dipped in another aqueous solution free of alkali ions, to which an oxidation current is sent by use of a platinum wire as a counter electrode to carry out electrolytic oxidation. In this way, the alkali-metal ion with higher atomic number occluded in the iron cyanide compound at the electrolytic reduction is eluted in the above- mentioned different aqueous solution so as to be recovered by separation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the mutual separation of alkali ions in an aqueous solution.

(Prior art) Various methods are used to separate and recover metal ions dissolved in a solution, but it is generally difficult to separate and recover alkali ions from each other, and there is no suitable separation method. is the current situation.

(Means for solving the problem) In view of these circumstances, as a result of intensive research into methods for separating alkali ions, we found that specific ions can be isolated by electrolytically reducing iron cyanide compounds in a mixture of multiple alkali ions. The present inventors have discovered that these can be separated, leading to the present invention.

The iron cyanide compound used in the present invention is Prussian blue. When this is electrolytically reduced in an aqueous solution containing alkali ions, the ions of the alkali metal with a large atomic number easily enter the crystals of the compound, but the ions of the alkali metal with a small atomic number easily enter the crystals of the compound! ? The present invention is based on the property that it is difficult to intrude into +'11. When the compound is electrolytically reduced in a mixed solution of alkali ions, more ions of the alkali metal having a larger atomic number penetrate into the crystals of the compound.

In order to recover the alkali ions from the iron anide compound that has occluded specific ions as described above, the occluded ions are dissolved into water by electrolytically oxidizing the compound in water or air oxidizing it. At this time, the iron cyanide compound returns to its initial state containing no alkali ions, so it can be used repeatedly to separate the ions.

(Effects of the Invention) By the method of the present invention, specific alkali ions can be separated, recovered or concentrated.

Example 1 A platinum plate electrode (38α2) on which Prussian blue, which is one of the iron cyanide compounds, was electrodeposited was immersed in a 100M aqueous solution containing NNaC100I and K (10.1M), and a 1 mA ring current was applied using the platinum wire as a counter electrode. After flowing for 10 minutes, the platinum plate electrode was placed in another 10 m
The sample was transferred to an aqueous solution of , and an oxidation current of 1 mA was applied for 10 minutes using the same platinum wire as a counter electrode. As a result, there was 0.11mmL of sodium in this 10m/collected liquid, but
Potassium was 0.20mM.

This confirmed that potassium was selectively separated and recovered. Note that all aqueous solutions contain 0.1 M acetic acid for pH adjustment.

Example 2 Using similar methods and apparatus, L iC(1, N a C(1
, KCLRbCl, C5CJ? , a solution containing 91% cesium in molar ratio was recovered, making it possible to selectively separate and recover cesium.

At this time, when Prussian blue was oxidized by blowing air, cesium was selectively recovered in the same way.

Example 3 Using a similar method and apparatus, selective recovery from hot water from a first geothermal power plant was attempted. In hot water, the molar ratio is LiCff0,
007, NaCl0090, KCl0.09, RbC1
0,0003, but selective recovery with Prussian blue resulted in a) V ratio TF Na (J? 0.59, KC
A solution containing no. 40 and RbCN0001 was collected, and Na
It was confirmed that KCl and RbC1 were selectively concentrated even from a solution containing 90% C6.

Claims (1)

[Claims] An ion separation method characterized by electrolytically reducing an iron cyanide compound in an aqueous solution containing several types of alkali metal ions to occlude alkali metal ions with higher atomic numbers into the compound.