Indium selenide framework constructed from supertetrahedral clusters for efficient adsorption of Cs+ and Sr2+

Construction strategy for selenide exchanger by integrating T3 supertetrahedral clusters. • Synergistic effects of Se component and microporosity on the adsorption kinetics enhancement. • Efficient removal (up to 99.99%) of Cs + and Sr 2+ by column and ultrathin membrane. • High selectivity for Cs + and Sr 2+ in presence of excess coexisting cations and anions. • Great pH (3–12)/irradiation resistance, high exchange selectivity, and facile elution. Elimination of long half-lived 137 Cs + and 90 Sr 2+ hazards through adsorption technique is critical for environmental protection and human health. However, traditional adsorbents are limited in radioactive wastewater treatment by slow kinetics, weak anti-interference, and poor practical applicability. Herein, an indium selenide adsorbent Na 6 In 10 Se 18 ·11.5H 2 O ( InSe-1Na ), with an anionic framework constructed from corner-sharing T3 supertetrahedral clusters, was synthesized using a “assembly-activation” strategy. The soft basic Se component and the cluster-induced microporosity synergistically endow InSe-1Na with remarkable Cs + /Sr 2+ enrichment capacity. It exhibits ultra-fast adsorption kinetics, removing 97.84% of Cs + within 5 min and 99.84% of Sr 2+ within 20 min. The corresponding second-order rate constants ( k 2 ) are 10.241 and 0.335 g mg −1  min −1 , respectively, rendering it the fastest selenide adsorbent. InSe-1Na shows structural stability over a broad pH range of 3–12, with maximum distribution coefficients ( K d ) of 1.02 × 10 5  mL g −1 for Cs + and 8.29 × 10 5  mL g −1 for Sr 2+ . The maximum adsorption capacities ( q m ) of Cs + and Sr 2+ are 252.10 ± 3.77 and 86.49 ± 3.71 mg g −1 , respectively. It exhibits resistance to coexisting ions, maintaining a removal rate ( R ) ≥ 94.73% in the presence of 10 mmol L −1 Na + . Moreover, the rapid kinetic response facilitates its application in column ( R  = 99.65%–99.99%) and membrane ( R  = 98.95%–99.98%, 0.40 s contact time) filtrations for mixed Cs + and Sr 2+ flow. Given its straightforward synthesis, β/γ irradiation tolerance, and easy elution, InSe-1Na represents a promising adsorbent for radioactive decontamination. Deep purification of nuclear contaminated water containing radioactive 137 Cs + and 90 Sr 2+ is promisingly achieved by a supertetrahedral-cluster-constructed indium selenide ion exchanger, Na 6 In 10 Se 18 ⸱ 11.5H 2 O ( InSe-1Na ), whose soft Se component and microporosity endow this material with top-ranked adsorption kinetics (even in suction filtration conditions with 0.40 s contact time), high capacities, superior selectivity, good resistance to acid/base/coexisting ions, and remarkable column/membrane performances. Download: Download high-res image (131KB) Download: Download full-size image