Add time:07/21/2019         Source:sciencedirect.com

Uptake behaviour of uranium from aqueous, acidic sulfate and chloride media on iminodiacetic acid chelating resin Purolite S930+ has been studied. Experiments have followed UO22+, Cu2+ and Fe3+ uptake behaviour with respect to acidic and ionic media type and concentration. Uptake suppression of all metals was observed at [H+] > 0.1 M sourced from H2SO4 and HCl. In contrast, significant uptake of Fe3+ was observed from solutions with [HCl] > 2 M. Suppression of UO22+ uptake (up to 15%) was observed upon increasing [SO42−] to 4 M, whilst negligible UO22+ uptake suppression was observed with [Cl−] up to 6 M. The impact of Fe3+ concentration on UO22+ extraction under hypersaline conditions ([Cl−] = 22.6 g L−1, 0.64 M) has been studied and behaviour fit to Langmuir and Dubinin-Radushkevich isotherms. Extended X-ray absorption fine structure (EXAFS) studies have been performed to assess the effect of salinity on the uranium coordination environment on the resin and therefore the mechanism of uptake. No change in surface species was observed, with the fit species being uranyl bound by the iminodiacetic acid functional group in a tridentate motif, with an associated bidentate sulfate group. An isotherm model based on this surface species has also been derived. It has been shown that at pH 2 there is little impact of increasing chloride and sulfate concentrations on the extraction behaviour of metals onto Purolite S930+ under the conditions tested. Rather, uranium uptake is more affected by the presence of Fe3+ in solution. As [Fe3+]/[UO22+] is increased from 0 to 2, UO22+ uptake is reduced by up to 66% at aqueous equilibrium.

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