Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

Abstract

AbstractTechnetium‐99 is a prevalent fission product from nuclear waste. The long half‐life (211,000 yr) and environmental mobility of pertechnetate (TcO4−) render Tc particularly challenging to isolate and stabilize. Here we present two approaches for development of potential wasteforms using titanium dioxide, TiO2. Approach 1 is a low temperature chemical synthesis of TiO2 doped with Tc(IV) from TcO4− intended to mimic the Tc waste stream from the UREX family of separations and removes 98.5 % of the Tc, mainly present as edge‐shared Tc(IV) pairs. Approach 2 utilizes TiO2 to photocatalytically reduce TcO4− to Tc(IV) stabilized on the surface of or within the TiO2 lattice. The %Tc removed from solution and adsorbed to TiO2 is pH dependent, with the maximum Tc(IV) adsorbed at pH 3–4 as either TcO2 or edge‐sharing Tc(IV) octahedra. The Tc(IV)‐TiO2 composites materials formed by both approaches are suitable for consolidation into a dense wasteform by Hot Isostatic Pressing (HIPing).