Uranyl is an important environmental contaminant at high-level nuclear waste storage facilities, such as Hanford, WA, at former uranium milling facilities, such as Rifle, CO, and at natural uranium deposits, such as the Powder River Basin in Wyoming. Sorption of uranyl on mineral surfaces or its incorporation in mineral structures help reduce the hazard of this highly mobile ion in groundwater and surface waters. Many factors impact the sorption of uranyl to mineral surfaces including solution pH, reduction-oxidation conditions, intrinsic differences in reactivity of different mineral substrates, natural organic matter (NOM) and microbial biofilm coatings on mineral surfaces, and the presence of CO<sub>2</sub> dissolved in natural waters, among others. We will review the results of studies of sorption reactions of uranyl with minerals in subsurface sediments at the Hanford site and in surface waters and sediments at Rifle, CO. We will also discuss the results of a recent laboratory study of the effect of NOM (humic and fulvic substances) on the sorption of uranyl on 2-line ferrihydrite (Fh), a common, naturally occurring nano-Fe(III)-hydroxide. In order to determine the effect of NOM associated with Fh nanoparticles on the sorption of aqueous uranyl ions, uranyl was reacted with Fh at pH 4.6 and 7.0 in the presence and absence of Elliott Soil Humic Acid (ESHA) (0–835 ppm) or Suwanee River Fulvic Acid (SRFA) (0–955 ppm). No evidence was found for reduction of uranyl by either form of NOM after 24 hours of exposure. We used x-ray absorption spectroscopy to characterize molecular-level changes in uranyl complexation resulting from sorption to Fh-NOM aggregates. The results of this study will be discussed.        <br/>

Factors affecting the sorption of uranyl at mineral-aqueous solution interfaces

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.