The process and mechanism for cesium and rubidium extraction with saponified 4-tert-butyl-2-(α-methylbenzyl) phenol

Cesium (Cs) and rubidium (Rb) separation from brine is an important and application-oriented topic. 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) has been used for Cs and Rb extraction. However, the traditional extraction technology is base and acid consumed. In the present work, an innovative process for Cs and Rb extraction with t-BAMBP is developed, which consists of saponification, extraction, scrubbing and stripping. Both infrared spectrum and electrostatic potential analysis indicate the hydrogen of phenolic hydroxyl is dissociated from t-BAMBP during saponification and the oxygen of phenolic hydroxyl is the binding site for alkali metal ions. Saponified organic phase shows an excellent extraction effect for Cs+ and Rb+. The extraction reaches equilibrium in 5 min, with 99.5% Cs+ and 46.7% Rb+ are loaded into the organic phase in the single-stage extraction. Slope method indicates the structure of the extraction complex is MOR·3ROH (M = Cs+, Rb+, K+), where the electrostatic attraction between M+ and the oxygen of phenolic hydroxyl is dominant, and the cation–π interaction has a significant effect also. The extraction complex of MOR·3ROH dissociates in the acid environment while scrubbing and stripping is completed. The Cs+ and Rb+ are separated from the mixture phase, the proton H bonds to the phenolic hydroxyl group, and the extractant is regenerated.