Uranium is important in the nuclear fuel cycle both as an energy source and as radioactive waste. It is of vital importance to recover uranium from nuclear waste solutions for further treatment and disposal. Herein we present the first chalcogenide example, (Me2NH2)1.33(Me3NH)0.67Sn3S7·1.25H2O (FJSM-SnS), in which organic amine cations can be used for selective UO2(2+) ion-exchange. The UO2(2+)-exchange kinetics perfectly conforms to pseudo-second-order reaction, which is observed for the first time in a chalcogenide ion-exchanger. This reveals the chemical adsorption process and its ion-exchange mechanism. FJSM-SnS has excellent pH stability in both strongly acidic and basic environments (pH = 2.1-11), with a maximum uranium-exchange capacity of 338.43 mg/g. It can efficiently capture UO2(2+) ions in the presence of high concentrations of Na(+), Ca(2+), or HCO3(-) (the highest distribution coefficient Kd value reached 4.28 × 10(4) mL/g). The material is also very effective in removing of trace levels of U in the presence of excess Na(+) (the relative amounts of U removed are close to 100%). The UO2(2+)···S(2-) interactions are the basis for the high selectivity. Importantly, the uranyl ion in the exchanged products could be easily eluted with an environmentally friendly method, by treating the UO2(2+)-laden materials with a concentrated KCl solution. These advantages coupled with the very high loading capacity, low cost, environmentally friendly nature, and facile synthesis make FJSM-SnS a new promising remediation material for removal of radioactive U from nuclear waste solutions.
The removal of highly radioactive and long-lived 137 Cs + and 90 Sr 2+ from solution is of significance for radionuclide remediation. Herein we prepared a two-dimensionally microporous thiostannate, namely (Me 2 NH 2 ) 4/3 (Me 3 NH) 2/3 Sn 3 S 7 $1.25H 2 O (FJSM-SnS), and systematically investigated its Cs + and Sr 2+ ionexchange 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 Sr 2+ ion-exchange capacities of FJSM-SnS were 408.91 mg g À1 and 65.19 mg g À1 , 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 Sr 2+ 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. † Electronic supplementary information (ESI) available: Crystallographic data for FJSM-SnS and FJSM-SnS-Cs in CIF format, TG-MS spectra, mass spectra of solution and solvent, PXRD, EDS, the kinetics studies at room temperature, IR and table of data in the simulated groundwater, competitive ion-exchange experiments and the ion-exchange chromatographic column experiment. CCDC 1025383 and 1025384. For ESI and crystallographic data in CIF or other electronic format see
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