Efficient Removal of [UO2]2+, Cs+, and Sr2+ Ions by Radiation-Resistant Gallium Thioantimonates

Abstract

Unconventional ion exchangers can achieve efficient removal of [UO₂]²⁺, Cs⁺, and Sr²⁺ ions from complex aqueous solutions and are of great interest for environmental remediation. We report two new gallium thioantimonates, [Me₂NH₂]₂[Ga₂Sb₂S₇]·H₂O (FJSM-GAS-1) and [Et₂NH₂]₂[Ga₂Sb₂S₇]·H₂O (FJSM-GAS-2), which present excellent ion exchange properties for [UO₂]²⁺, Cs⁺, and Sr²⁺ ions. They exhibit high ion exchange capacities for [UO₂]²⁺, Cs⁺, and Sr²⁺ ions ( q_m^U = 196 mg/g, q_m^Cs = 164 mg/g, and q_m^Sr = 80 mg/g for FJSM-GAS-1, q_m^U = 144 mg/g for FJSM-GAS-2) and short equilibrium times for [UO₂]²⁺ ion exchange (5 min for FJSM-GAS-1 and 15 min for FJSM-GAS-2, respectively). Both compounds display active ion exchange with [UO₂]²⁺ in the pH range of 2.9-10.5. Moreover, the sulfide compounds could maintain high distribution coefficients K_d^U even in the presence of excess Na⁺, Ca²⁺, and HCO₃^-. The distribution coefficient K_d^U of 6.06 × 10⁶ mL/g exhibited by FJSM-GAS-1 is the highest among the reported U adsorbents. The [UO₂]²⁺-laden products can be recycled by conveniently eluting the uranium with a low-cost method. These advantages combined with facile synthesis, as well as β and γ radiation resistance, make FJSM-GAS-1 and FJSM-GAS-2 promising for selective separations in nuclear waste remediation.