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Redox Behavior of Uranium at the Nanoporous Aluminum Oxide-Water Interface: Implications for Uranium Remediation

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journal contribution
posted on 03.07.2012, 00:00 by Hun Bok Jung, Maxim I. Boyanov, Hiromi Konishi, Yubing Sun, Bhoopesh Mishra, Kenneth M. Kemner, Eric E. Roden, Huifang Xu
Sorption–desorption experiments show that the majority (ca. 80–90%) of U­(VI) presorbed to mesoporous and nanoporous alumina could not be released by extended (2 week) extraction with 50 mM NaHCO3 in contrast with non-nanoporous α alumina. The extent of reduction of U­(VI) presorbed to aluminum oxides was semiquantitatively estimated by comparing the percentages of uranium desorbed by anoxic sodium bicarbonate between AH2DS-reacted and unreacted control samples. X-ray absorption spectroscopy confirmed that U­(VI) presorbed to non-nanoporous alumina was rapidly and completely reduced to nanoparticulate uraninite by AH2DS, whereas reduction of U­(VI) presorbed to nanoporous alumina was slow and incomplete (<5% reduction after 1 week). The observed nanopore size-dependent redox behavior of U has important implications in developing efficient remediation techniques for the subsurface uranium contamination because the efficiency of in situ bioremediation depends on how effectively and rapidly U­(VI) bound to sediment or soil can be converted to an immobile phase.