Development of Flow Type Cesium Removing Device Using Fluorinated Solvent

Motoshi Suzuki,Aoi Kikuchi,Shou-Ichi Nanba,Hideo Tajima,Youji Taguchi,M Shimada

doi:10.1051/matecconf/202133304011

Abstract

In order to simultaneously achieve separation and volume reduction of radioactive cesium in the aqueous solution, we proposed a solvent extraction using a fluorinated solvent which is a nonflammable liquid having a low boiling point and is easy to distill for regeneration. Firstly optimum conditions for single extraction were determined in a batch operation. The extraction experiment was carried out by changing the pH of 5 mg/L non-radioactive cesium aqueous solution using bis(2-ethylhexyl)phosphoric acid (D2EHPA) as an extractant. The higher the pH of the aqueous phase and the D2EHPA concentration, the better the removal rate. The highest removal rate was about 60% under the pH=13. From the experimental results, the optimum extraction condition was determined as pH=13 and [D2EHPA]=0.15 mol/L. Next multiple extraction test was carried out under this condition, and 90% cesium removal could be achieved in 3 times extraction. Finally, the flow type device using a static mixer for mixing and extracting parts was proposed and then the cesium removal test was performed. The cesium removal performance of this device was equivalent to the batch system.

Highlights

Fukushima accident caused a large amount of cesiumcontaminated water and contaminated soil to which cesium was adsorbed
To solve the problem we proposed solvent extraction using fluorinated solvents to simultaneously achieve separation and volume reduction of radioactive cesium in aqueous solution
The extraction of cesium ion was performed by D2EHPA with fluorinated solvents

Summary

Introduction

Fukushima accident caused a large amount of cesiumcontaminated water and contaminated soil to which cesium was adsorbed. It is necessary to dispose of them and to separate and recover radioactive cesium from them. A general of separating cesium from an aqueous solution is adsorption and solvent extraction. The adsorption method utilizes the fact that an adsorbent having pores close to the ion radius of cesium captures cesium ions. Zeolites are highly selective to cesium and adsorb with high efficiency, but they are not suitable for reuse after adsorption. There is a method of adsorption using Prussian blue that is selective to cesium, but there is a risk of producing toxic cyanide

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