A two-dimensionally microporous thiostannate with superior Cs⁺ and Sr²⁺ ion-exchange property

The removal of highly radioactive and long-lived ¹³⁷Cs⁺ and ⁹⁰Sr²⁺ from solution is of significance for radionuclide remediation. Herein we prepared a two-dimensionally microporous thiostannate, namely (Me₂NH₂)_4/3(Me₃NH)_2/3Sn₃S₇·1.25H₂O (FJSM-SnS), and systematically investigated its Cs⁺ and Sr²⁺ ion-exchange performance in different conditions. The structural stabilities and variation, ion-exchange kinetic and isothermal behavior, pH-dependent distribution coefficients (K_d), ion-exchange in simulated groundwater and ion-exchange applied to chromatography have been investigated. The results indicated that the maximum Cs⁺ and Sr²⁺ ion-exchange capacities of FJSM-SnS were 408.91 mg g^-1 and 65.19 mg g^-1, respectively. In particular, FJSM-SnS showed quick ion-exchange ability and wide pH resistance (0.7-12.7) which make it outstanding among the ion-exchangers. An ion-exchange chromatographic column was firstly studied for chalcogenido ion-exchange materials, that is, a column filled with 3.0 g FJSM-SnS could remove 96-99% of Cs⁺ ion and near 100% of Sr²⁺ ion at low ionic concentrations in 900 bed volumes solutions. Furthermore, the title material could be synthesized on a large scale by a facile, one-pot and economical solvothermal method. The relatively low cost but remarkable ion-exchange performance makes it promising for radionuclide remediation.