PH‐Controlled Switch over Coadsorption and Separation for Mixed Cs+ and Sr2+ by an Acid‐Resistant Potassium Thioantimonate

Abstract

AbstractSwitchable coadsorption and separation for elimination/partitioning of Cs+ and Sr2+ is achieved by pH‐controlled ion exchange using a potassium thioantimonate K2Sb4S7·2H2O (SbS‐1K) with fantastic pH durability from diluted NaOH (pH 12) to concentrated HCl (3 m). At pH 6, SbS‐1K exhibits ultrafast adsorption kinetics (R ≈ 90% in 2 min for Cs+ and 20 min for Sr2+) and high removal rates (R ≈ 98–99%) at equilibrium for both Cs+ and Sr2+. At pH 2, the Sr2+ adsorption is inhibited by H+ with a great loss in RSr to 11.18%, whereas the RCs remains at 96.99%, contributing to a top‐ranked separation factor SFCs/Sr of 256. The SbS‐1K‐filled ion exchange column can be switched between the eliminating (RCs > 99.91%; RSr > 98.19%) and separating (RCs > 98.99%; RSr ≈ 0±3%) modes for treating continuous flow with a variation from pH 6 to pH 2 or vice versa. The SbS‐1K/PTFE membrane exhibits coadsorption and separation effects for filtration of low concentrated mixed Cs+ and Sr2+ solution (1 ppm for each), even at an ultrafast vacuum filtration speed (30 mL min–1). Combined with easy synthesis and high β/γ irradiation resistance, SbS‐1K represents a new‐concept bifunctional exchanger with discriminating intelligence for equipment innovation.