Permeable Layered Tin Sulfide Ion Exchanger for Rapid Elimination of Cs+ and Sr2+

A porous layered tin sulfide material, [(CH₃)₂NH₂]₂Sn₃S₇·0.4H₂O (SnS-1), is developed for rapid Cs⁺ and Sr²⁺ removal from aqueous solutions. The alignment of hexagonal windows (8.3 × 8.3 Ų in cross-section) across the stacked layers forms straight pseudochannels that enables effective ion diffusion and accommodation. SnS-1 exhibits outstanding ion exchange kinetics (k₂^Cs = 0.256 g mg^-1 min^-1; k₂^Sr = 0.272 g mg^-1 min^-1) and capacities (q_m^Cs = 417.24 mg g^-1; q_m^Sr = 116.18 mg g^-1), exceeding most chalcogenide-based exchangers. It exhibits acid-base resistance across a broad pH range (0-11) and remarkable selectivity for Cs⁺ and Sr²⁺ over various competing ions. Dynamic column filtration confirms the separation applicability of SnS-1, featuring sustained Sr²⁺ removal (R^Sr = 94.45-99.51%) against Cs⁺ (R^Cs = -20 ± 5%). The SnS-1/PTFE composite membrane can efficiently remove Cs⁺ and Sr²⁺ from continuous flow (2.0 mL min^-1 cm^-2), with removal efficiencies exceeding 91.71 and 98.91%, respectively. Moreover, the adsorbed Cs⁺ and Sr²⁺ ions can be readily eluted from the spent column and membrane using a 2 M NaCl solution. Combined with simple synthesis, radiolytic stability, and superior performance, microporous SnS-1 emerges as a promising candidate for nuclear wastewater remediation.