Porous iron material for TcO4- and ReO4- sequestration from groundwater under ambient oxic conditions.

• Porous iron (pFe) had TcO 4 − removal capacity of 27.5 mg/g from groundwater. • pFe had a capacity of 23.9 mg/g for removing ReO 4 − from groundwater. • Tc species on pFe were 70–80% Tc(IV) and 20–30% TcO 4 − stabilized with Fe hydroxides. • Re species on pFe were 100% ReO 4 − stabilized with Fe hydroxides. Technetium-99 (99Tc) is a major contaminant at nuclear power plants and several US Department of Energy sites. Its most common aqueous species, pertechnetate (TcO 4 −), 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 4 − and perrhenate (ReO 4 −) sequestration from artificial groundwater. The pFe was significantly more effective than granular iron for both TcO 4 − and ReO 4 - 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), Fe 3 O 4) and 20–30% unreduced TcO 4 −. In contrast, the removed Re species was ReO 4 − only, without detectable Re(IV). In addition, the sequestered ReO 4 − was not extracted (<3%) by 0.1 M Na 2 SO 4 and 1 M KI solution, which indicated that ReO 4 − and by chemical analogy, unreduced TcO 4 −, was likely incorporated into Fe corrosion products. This inexpensive pFe material may be applied to the sequestration and stabilization of 99TcO 4 − from contaminated environments and nuclear waste streams. [ABSTRACT FROM AUTHOR]