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

Switchable coadsorption and separation for elimination/partitioning of Cs + and Sr 2+ is achieved by pH-controlled ion exchange using a potassium thioantimonate K 2 Sb 4 S 7 ·2H 2 O ( 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 Sr 2+ ) and high removal rates ( R ≈ 98–99%) at equilibrium for both Cs + and Sr 2+ . At pH 2, the Sr 2+ adsorption is inhibited by H + with a great loss in R Sr to 11.18%, whereas the R Cs remains at 96.99%, contributing to a top-ranked separation factor SF Cs/Sr of 256. The SbS-1K -filled ion exchange column can be switched between the eliminating ( R Cs > 99.91%; R Sr > 98.19%) and separating ( R Cs > 98.99%; R Sr ≈ 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 Sr 2+ 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.