Cesium Recovery from High-Salinity Solutions under Low-Alkalinity Conditions for High-Purity Cesium Chloride Preparation

Abstract

The recycling of process liquors during lithium extraction from lepidolite enriches Cs, Rb, K, and Na, creating a high-salinity multicomponent liquor that complicates selective cesium recovery. Here, a simple t-BAMBP/sulfonated kerosene system was developed for Cs recovery under low alkalinity. At 0.1 mol/L OH–, 1.0 mol/L t-BAMBP, for 5 min, and at an O/A ratio of 1:2, four-stage counter-current extraction achieved 99.24% Cs extraction with a Cs/Rb separation factor of 408.55. Five-stage HCl scrubbing removed 99.66% Rb and 100% K with limited Cs loss, and the spent scrubbing solution was recycled to improve Cs recovery. Subsequent stripping and recrystallization produced CsCl with 99.5% purity, while 60 h continuous operation showed stable extraction performance and less than 1% extractant loss. Slope analysis, FT-IR, and 1H NMR indicate a cation-exchange mechanism driven by phenolic hydroxyl deprotonation. In the real liquor, increasing alkalinity increased the apparent participation of t-BAMBP and shifted the apparent solvation state toward a CsOR·3ROH-like state. This work provides a low-alkalinity route for selective Cs recovery from post-lithium-extraction liquor.