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

Li, Dien, Seaman, John C., Hunyadi Murph, Simona E., Kaplan, Daniel I., Taylor-Pashow, Kathryn, Feng, Renfei, Chang, Hyunshik, Tandukar, Madan
Journal of hazardous materials 2019 v.374 pp. 177-185
X-ray absorption spectroscopy, aerobic conditions, corrosion, groundwater, iron, iron oxides, nuclear power, pH, power plants, radioactive waste, sodium sulfate, United States
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 (<3%) by 0.1 M Na2SO4 and 1 M KI solution, which indicated that ReO4− and by chemical analogy, unreduced TcO4−, was likely incorporated into Fe corrosion products. This inexpensive pFe material may be applied to the sequestration and stabilization of 99TcO4− from contaminated environments and nuclear waste streams.