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

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Technetium ( 99 Tc) is a long-live radionuclide, and its removal from legacy nuclear waste is problematic mainly because of its persistence as highly soluble pertechnetate ( 99 TcO 4 – ) ions. Here, we report the application of [Sn 2 S 6 ] 4– anion intercalated layered double hydroxides, LDH-[Sn 2 S 6 ] for the removal of perrhenate (ReO 4 – ), a nonradioactive surrogate of 99 TcO 4 – . In acidic and neutral media, LDH-[Sn 2 S 6 ] can remove over 98 and 96% of ReO 4 –, respectively, from a 1000 ppb spiked solution in 48 h, and the removal of ReO 4 – remains beyond 87% even after 15 days of interaction with the solution. Moreover, in the presence of other metal ions, for instance, Cu 2+, ReO 4 – removal increases to about 99.9%, leaving the residual concentration of <1 ppb with K d ∼ 5.00 × 10 7 mL/g. LDH-[Sn 2 S 6 ] also exhibits large sorption capacities for ReO 4 – at 9.3 × 10 4 μg/g at pH ∼ 2. Evidenced by XRD, SEM, HRTEM, EDS, and XPS, we further demonstrate the removal of ReO 4 – 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 99 TcO 4 – .