A Two-Dimensional Thiotitanate Ion Exchanger with High Cs+ Removal Performance

Cs-137 is a persistent beta/gamma-emitter (t(1/2) = 30.1 years) generated from U-235 and Pu-239 fission. It is a critical challenge to efficiently capture Cs-137(+) for nuclear waste management due to its high solubility, environmental mobility, and propensity for biological accumulation. Herein, we prepare a two-dimensional (2D) thiotitanate Rb0.32TiS2<middle dot>0.75H(2)O (denoted Rb-TiS2) using a special molten salt synthesis method, "Mg + RbCl". Rb-TiS2 can selectively capture Cs+ from aqueous solutions. Its structure features a flexible anionic thiotitanate layer with Rb+ as counter ions located at the interlayer spaces. As an ion exchanger, it possesses high adsorption capacity (q(m)(Cs) = 232.70 mg<middle dot>g(-1)), rapid kinetics (the removal rate R > 72% within 10 min), and a wide pH tolerance range (pH = 4-12) for Cs+ adsorption. Through a single-crystal X-ray structural analysis, we elucidated the mechanism of Cs+ capture, revealing the ion exchange pathways between Cs+ and Rb+ in Rb-TiS2. This work not only provides an important reference for the synthesis of transition metal sulfides with alkali metal cations but also proves the application prospect of transition metal sulfides in radionuclide remediation.