The effect of carboxylic, phenolic, and carbonyl functional groups on uranium (U) reactivity was investigated using XPS, and water chemistry techniques. Batch reactors with equimolar (0.1mM) concentrations of U and one organic compound were conducted over 24 h to assess the U reactivity as a function of pH and the presence of specific functional groups. Citric acid and sodium citrate were used as a proxy for carboxylic functional group at pH 2, pH 7 and pH 13. Likewise, salicylic acid and sodium salicylate were used to represent a combination of carboxylic and phenolic functional groups. High-resolution C1s spectra in liquid samples showed a shift on the carboxylic bond from citric acid, salicylic acid and sodium salicylate at pH 7 and 2. This peak is likely the result of an electrostatic interaction between a carboxylic functional group and U after the reaction. Total U in solution did not change due to the reaction at the different pH values evaluated in the batch experiments. These findings suggest that uranium is possibly complexing with carboxylic functional groups and no precipitation is occurring at the settings investigated. This study identified the relevance of U and organic functional groups interacting in organic-rich environments and influencing the U mobilization. Our research complements previous efforts from our research group at understanding the role of organic matter in U mine wastes.

Effects of carboxylic, phenolic, and carbonyl functional groups on uranium reactivity under laboratory conditions

2019 Spring National Meeting

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