Unveiling the Potential of [Sn2S6]4– Functionalized Layered Double Hydroxides for the Sorption of ReO4– as a Surrogate for 99TcO4–

Technetium (99Tc) is a long-live radionuclide, and its removal from legacy nuclear waste is problematic mainly because of its persistence as highly soluble pertechnetate (99TcO4–) ions. Here, we report the application of [Sn2S6]4– anion intercalated layered double hydroxides, LDH-[Sn2S6] for the removal of perrhenate (ReO4–), a nonradioactive surrogate of 99TcO4–. In acidic and neutral media, LDH-[Sn2S6] can remove over 98 and 96% of ReO4–, respectively, from a 1000 ppb spiked solution in 48 h, and the removal of ReO4– remains beyond 87% even after 15 days of interaction with the solution. Moreover, in the presence of other metal ions, for instance, Cu2+, ReO4– removal increases to about 99.9%, leaving the residual concentration of <1 ppb with Kd ∼ 5.00 × 107 mL/g. LDH-[Sn2S6] also exhibits large sorption capacities for ReO4– at 9.3 × 104 μg/g at pH ∼ 2. Evidenced by XRD, SEM, HRTEM, EDS, and XPS, we further demonstrate the removal of ReO4– occurs by ion-exchange and precipitation. Overall, the roles of 3d transition metal ions and the pH-driven sorption mechanisms introduce remarkable insights into metal sulfides intercalated LDH to remove 99TcO4–.