Localization of U(VI) on nickel hydroxide from aqueous solution in the presence of complexing anions at 25°C

Abstract

Sorption and coprecipitation of U(VI) from aqueous solution containing various complexing anions (CO 3 25- , SO 4 2− , H2EDTA2−) with the Ni(OH)2 solid phase at 25°C was studied. Uranium(VI) is not noticeably sorbed on the Ni(OH)2 solid phase from aqueous solutions containing CO 3 2− and SO 4 2− . The distribution coefficients K d are less than 1.0 ml g−1 throughout the examined range of [U(VI)]: [L] ratios (L = CO 3 2− , SO 4 2− ) at V/m ≥ 100 ml g−1 and contact time of the solid and liquid phases of 60 min. In the presence and in the absence of H2EDTA2−, the degree of the U(VI) sorption is essentially the same (K d ∼90–140 ml g−1 at V/m ≥ 100 ml g−1). Uranium(VI) does not coprecipitate with Ni(OH)2 from aqueous solutions containing SO 4 2− and H2EDTA2−. The distribution coefficients K d are less than 0.001 ml g−1 at V/m ≥ 200 ml g−1 and contact time of the solid and liquid phases of 60 min. In solutions containing CO 3 2− , the U(VI) capture by the Ni(OH)2 precipitate depends on the [CO 3 2− ]: [U(VI)] ratio. The higher the [CO 3 2− ]: [U(VI)] ratio, the more strongly U(VI) coprecipitates with Ni(OH)2.