Reduction of selenite and selenate on anoxically corroded iron and the synergistic effect of uranyl reduction |
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Authors: | Anders Puranen Mats Jonsson Daqing Cui |
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Affiliation: | a KTH Chemical Science and Engineering, Nuclear Chemistry, Royal Institute of Technology, Se 100 44 Stockholm, Sweden b Laboratory for Waste Management, Paul Scherrer Institut, Villigen CH-5232, Switzerland c Hot Cell Laboratory, Studsvik Nuclear AB, 71182 Nyköping, Sweden |
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Abstract: | In this work the uptake of dissolved selenium in the form of selenite and selenate on iron covered by a magnetite corrosion layer and the effect of dissolved uranyl on this process is studied. Under simulated anoxic groundwater conditions (bicarbonate and chloride solutions) no immobilization of selenate was found in the absence of uranyl whereas selenite was immobilized, albeit slowly. When uranyl was present, it was found to become reduced and greatly enhanced the rate of reductive immobilization of the dissolved selenite as well as selenate. The increased rate of immobilization is proposed to be due to the oxidative transformation of the passifying magnetite layer as the uranyl is reduced with the observed formation of a transient mixed Fe(II)/Fe(III) oxyhydroxide phase. The iron oxide, and selenium speciation on the surfaces were investigated by Raman spectroscopy. X-ray Absorption Spectroscopy was used to determine the oxidation state of the selenium and uranium on the surfaces. |
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