Solvent extraction of cesium and rubidium from brine solutions using 4- tert -butyl-2-( α -methylbenzyl)-phenol

A comprehensive study on the separation of cesium and rubidium from potassium with 4-tert-butyl-2-(α-methylbenzyl)-phenol (t-BAMBP) from a synthetic brine solution containing 20 mg/L Cs, 200 mg/L Rb and 5 g/L K was conducted. The effects of alkalinity, t-BAMBP concentration, temperature, A/O ratio on extraction were investigated. It was found that the best conditions to extract cesium and rubidium were using 30% t-BAMBP concentration with 0.1 M NaOH feed solution alkalinity under room temperature, for example 22 °C, at an A/O ratio of 1. Under these conditions, the separation factor of cesium and rubidium over potassium were found to be 139 and 11, respectively. The kinetics of both extraction and stripping were fast with equilibrium reached within 2 min. All extracted cesium and rubidium and 93% potassium were stripped with 0.1 M HCl at an A/O ratio of 1:1 in a single contact. A batch continuous test with 5 extraction stages was conducted under these conditions. It was found that over 99% cesium and rubidium were extracted with 19.4% potassium co-extracted. The concentration ratios of potassium over cesium decreased from 216 in the feed solution to 42 in the loaded organic solution and that of potassium over rubidium from 22 to 4.3, resulting in a decrease in concentration ratios of potassium over cesium and rubidium by about 5 times. Further work should target to test feed solution containing sodium and to improve extraction efficiency and selectivity of the extraction system.