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