The efficient removal of Sr2+ by two thiostannates via ion exchange

Abstract

90Sr is one of the most hazardous radionuclides in spent fuel, as it releases high energy β radiation accompanied by the release of a large amount of heat. Its easily environmental mobility and calcium-like bioconcentration properties pose a serious threat to the ecological environment and human health. Therefore, the efficient removal of 90Sr from complex aqueous environments is of great significance. Herein, two new isomorphic thiostannates K2Sn2S5·H2O and K1.1Rb0.9Sn2S5·H2O, namely FJSM-KSnS and FJSM-KRbSnS, respectively, were prepared by the solvothermal method. Their structures feature the two-dimensional (2D) wavy anionic layer of [Sn2S5]n2n- with big windows of ten-membered rings. Alkali metal cations (K+/Rb+) as charge balancers as well as H2O molecules are located in the interlayer spaces. They exhibit the efficient Sr2+ removal performance with high adsorption capacities (qmSr = 59.88 mg/g for FJSM-KSnS, qmSr = 62.82 mg/g for FJSM-KRbSnS). FJSM-KSnS as a representative has fast kinetics (equilibrium within 10 minutes) and good selectivity for Sr2+ removal in the presence of excessive Na+, and even in actual environmental water samples. In addition, the Sr2+ capture mechanism is revealed by characterizations of energy-dispersive X-ray spectroscopy, elemental distribution mapping, and X-ray photoelectron spectroscopy. The efficient capture of Sr2+ is attributed to the ion exchange between Sr2+ and interlayered alkali metal ions of thiostannates. This work expands the structural types of thiostannates and provides new efficient ion exchange materials for radiostrontium remediation.