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

•Porous iron (pFe) had TcO4− removal capacity of 27.5 mg/g from groundwater.•pFe had a capacity of 23.9 mg/g for removing ReO4− from groundwater.•Tc species on pFe were 70–80% Tc(IV) and 20–30% TcO4− stabilized with Fe hydroxides.•Re species on pFe were 100% ReO4− 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 (TcO4−), 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 TcO4− and perrhenate (ReO4−) sequestration from artificial groundwater. The pFe was significantly more effective than granular iron for both TcO4− and ReO4- 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), Fe3O4) and 20–30% unreduced TcO4−. In contrast, the removed Re species was ReO4− only, without detectable Re(IV). In addition, the sequestered ReO4− was not extracted (