JPS6213289B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solvent extraction method using MIBK (methyl isobutyl ketone), for example, a method for removing iron mainly contained in a raw material aqueous solution in the separation process of zirconium and hafnium.

Taking the case of zirconium and hafnium as an example, the method for separating them is to add ammonium thiocyanate to an aqueous solution containing zirconium tetrachloride and selectively transfer hafnium in the form of a thiocyanate complex into the organic phase of MIBK. The method is used industrially. At this time, the iron chloride contained as an impurity in zirconium tetrachloride accelerates the decomposition of thiocyanate, resulting in not only a loss of thiocyanate but also a loss of MIBK and zirconium, so the iron content must be removed in advance. It is necessary to keep

A method for removing iron is to change iron to ferrous chloride, which is difficult to volatilize, in a reducing atmosphere, and sublimate and separate zirconium tetrachloride; dissolve zirconium tetrachloride in water and dissolve it in ZrOCl _2.8H under hydrochloric acid acidity. A method of crystallizing as ₂ O and separating it from iron chloride remaining in the mother liquor;
A method using a kerosene solution of octylamine has been proposed.

However, the sublimation method requires batch operation, which means that the processing capacity per facility is small, that it requires a large amount of thermal energy, and that there is a lot of loss due to the increased number of handlings; It contains a large amount of water of crystallization, making it difficult to completely separate it from the mother liquor, and the yield is poor; in the method using a kerosene solution of amine, the amine is expensive, and another type of solvent is required. However, each method has the disadvantage that it is not suitable for combination with an extraction method using MIBK.

This invention relates to a purification method that removes iron using MIBK as a pretreatment step for solvent extraction using MIBK and causes almost no loss of the main components, and its gist is as follows: An oxidizing agent is added to an aqueous solution of zirconium containing iron to convert ferrous ions to ferric ions, and the aqueous solution is mixed with the above aqueous solution.
This method consists in removing iron from a raw material aqueous solution in a solvent extraction step, which is characterized by transferring iron to the organic phase by bringing it into countercurrent contact with the organic phase of MIBK (methyl isobutyl ketone). In this case, if the iron-containing organic phase is further brought into contact with water and the iron content is extracted back from the organic phase, the organic phase can be used repeatedly.

Since iron does not migrate to the organic phase of MIBK in the form of ferrous ions, in the present invention, all iron is oxidized in advance and converted into ferric ions, which can easily migrate.
Although a wide variety of oxidizing agents can be used for this purpose, liquids such as sodium hypochlorite and hydrogen peroxide, and chlorine gas are particularly suitable. It is thought that ferric ions form a complex salt called [HFeCl ₄ ] in an acidic solution of hydrochloric acid, and this is extracted into an organic solvent as a molecular compound.

As the extraction operation in the method of the present invention, conventional contact methods, ie, countercurrent contact or a combination of mixing and liquid separation, can be used.

In this method, ferric ions are preferentially
Since the mixture is transferred to the organic phase of MIBK, the liquid volume ratio of water to organic phase may be 2:1 or less during extraction.

Furthermore, during extraction using MIBK, a portion of zirconium in the aqueous solution was transferred to the organic phase along with ferric ions, but the amount was less than 0.2% in one extraction operation.

MIBK has a solubility of about 2% in water, and MIBK has a solubility of about 2.4% in water.
is dissolved, but the zirconium aqueous solution continues to separate zirconium and hafnium.
Since it is used for countercurrent contact with MIBK, there is no loss. However, MIBK dissolved in the aqueous phase after back extraction will be lost unless a separate recovery operation is performed, so it is desirable to use as little water as possible for back extraction.

The method of the present invention will be specifically explained below using Examples.

Example 1 A 1.2 mol/ZrOCl ₂ aqueous solution in which zirconium tetrachloride was dissolved in water and the coordination degree was adjusted to 5N.
Add 1 part of sodium hypochlorite aqueous solution to 250,
Ferrous ions in the liquid were changed to ferric ions. Then, using a three-stage countercurrent extraction device, 3 volumes of this raw material liquid were brought into contact with 1 volume of MIBK. Through these operations, the iron concentration in the raw material liquid can be reduced from approximately 6200 ppm.
It decreased to 90ppm.

Example 2 The MIBK obtained in the above procedure contained about 18000 ppm iron. One volume of this MIBK was brought into contact with 3/4 volume of water to back-extract iron into the aqueous phase. By this operation, the iron concentration in MIBK was reduced to 80 ppm.

As described above, the method of the present invention makes it possible to remove iron with much higher efficiency than conventional techniques, with almost no loss of zirconium, which is the main component.

Claims (1)

[Claims] 1. Add an oxidizing agent to an aqueous solution of zirconium containing iron to convert ferrous ions to ferric ions, and bring the above aqueous solution into contact with an organic phase of MIBK (methyl isobutyl ketone) to convert iron into ferric ions. A method for removing iron from a raw material aqueous solution in a solvent extraction step, characterized by transferring iron to an organic phase. 2 Add an oxidizing agent to an aqueous solution of zirconium containing iron to convert ferrous ions to ferric ions, bring the above aqueous solution into contact with an organic phase of MIBK (methyl isobutyl ketone), and transfer iron to the organic phase. A method for removing iron from a raw material aqueous solution in a solvent extraction step, which further comprises back-extracting iron from this organic phase using water so that this organic phase can be used repeatedly.