Porous iron material for TcO- and ReO- sequestration from groundwater under ambient oxic conditions.

Technetium-99 (Tc) is a major contaminant at nuclear power plants and several US Department of Energy sites. Its most common aqueous species, pertechnetate (TcO), is very mobile in the environment, and currently there are no effective technologies for its sequestration. In this work, a porous iron (pFe) material was investigated for TcO and perrhenate (ReO) sequestration from artificial groundwater. The pFe was significantly more effective than granular iron for both TcO and ReO- sequestration under oxic conditions. The Tc removal capacity was 27.5 mg Tc/g pFe at pH ˜6.8, while the Re removal capacity was 23.9 mg Re/g pFe at pH ˜10.6. Tc K-edge XANES and EXAFS analyses indicated that the removed Tc species was 70-80% Tc(IV) that was likely incorporated into Fe corrosion products (i.e., Fe(OOH), FeO) and 20-30% unreduced TcO. In contrast, the removed Re species was ReO only, without detectable Re(IV). In addition, the sequestered ReO was not extracted (<3%) by 0.1 M NaSO and 1 M KI solution, which indicated that ReO and by chemical analogy, unreduced TcO, was likely incorporated into Fe corrosion products. This inexpensive pFe material may be applied to the sequestration and stabilization of TcO from contaminated environments and nuclear waste streams.