Molecular-Scale Evaluation of Technetium Retention by Functionalized Organoclays

Nuclear waste repository designs require immobilizing contaminants, including pertechnetate (TcO₄^–). Clay functionalized with organic cations (organoclay) has been shown to immobilize TcO₄^–. The current work measures the physicochemical properties of organoclays, tests each organoclay’s ability to retain TcO₄^–, and provides computational data for the orientation of the alkylammonium cation within the interlayer as well as binding energies for the pertechnetate–alkylammonium–clay system. The results show consistency between experimental and computational interplanar spacings and orientations, with indications that alkylammonium cations are sorbed to both the clay edge and interlayer sites during functionalization. Pertechnetate–alkylammonium interactions are calculated, and implications for TcO₄^– sequestration by organoclay are discussed.