Layered A₂Sn₃S₇·1.25H₂O (A = Organic Cation) as Efficient Ion-Exchanger for Rare Earth Element Recovery

Exploring new ion-exchangers for the recovery of rare earth elements (REEs) and recycling is worthwhile for the high-tech industry and an eco-friendly sustainable economy. The efficient enrichment of low concentration REE from complex aqueous solutions containing large excess of competitive ions is challenging. Here we present a chalcogenide example as a superior REE ion-exchanger efficiently removing them from very complex aqueous solutions, (Me₂NH₂)_1.33(Me₃NH)_0.67 Sn₃S₇·1.25H₂O (FJSM-SnS). The material exhibits fast and efficient ion exchange behavior with short equilibrium time (<5 min), high adsorption capacity (139 mg/g for Eu, 147 mg/g for Tb, 126 mg/g for Nd), wide pH resistance (1.9-8.5), the largest distribution coefficient (K_d) value of 6.5 × 10⁶ mL/g, good selectivity against Al³⁺, Fe³⁺, and Na⁺ ions, and high recovery rate (>99%) at low concentrations. Moreover, after ion-exchange, the REE in corresponding exchanged products could be easily recovered by elution. FJSM-SnS has superior capacity and faster absorption kinetics than other states of the artificial REE sorbents such as Al₂O₃/EG, clay minerals, zeolite, and activated carbon.