Enhanced uranium sorption on aluminum oxide pretreated with arsenate. Part I: Batch uptake behavior.

We explored mechanisms for increasing U(VI) sorption by pretreating alumina surfaces with arsenate, which has a high affinity for binding with uranyl and is an analog for phosphate. Batch experiments were conducted at pH approximately 4 by pretreating a gamma-alumina surface with arsenate, followed by the addition of uranyl. Parallel experiments were conducted with different alumina loadings as well as As and U concentrations. Results show positive correlations between U(VI) uptake and [As]ini/[U]ini (ratio between the initial As solution concentration for pretreatment and the initial U solution concentration), suggesting the formation of ternary surface complexes and/or precipitates. Desorption experiments show partial irreversibility of the adsorbed U, suggesting less likelihood of remobilization. The pretreatment process results in enhanced U uptake and enhanced stability of the sorbed U, and provides a basis for designing other treatment processes for selective remediation applications.