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Retention of U(VI) by the Formation of Fe Precipitates from Oxidation of Fe(II)

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journal contribution
posted on 07.08.2018, 00:00 by Huiyang Mei, Xiaoli Tan, Liqiang Tan, Yuedong Meng, Changlun Chen, Ming Fang, Xiangke Wang
The fate of radionuclide contaminants can be strongly affected by the Fe­(II) oxidation process at natural redox boundaries because the formative Fe precipitates may serve as scavengers for radionuclides. In this regard, we investigated the retention efficiency of U­(VI) by the formative Fe precipitates in dilute FeCl2 solutions under mild oxidative conditions. The formed precipitates were characterized using spectroscopic methods. The results identified that the presence of U­(VI) facilitated the formation of Fe precipitates as lepidocrocite. The high retention efficiency of U­(VI) through co-precipitated reaction is ascribed to the synergetic effect of incorporation and adsorption processes. The successive acid-washing experiments, energy-dispersive X-ray spectra, and excitation–emission matrix spectra revealed that adsorbed U was washed off, while incorporated U was still in the precipitates. As a redox-active trace element, U incorporated into the solids could be in the state of U­(V) or U­(VI) as analyzed from X-ray photoelectron spectroscopy. These results may be of value in evaluating the potential of permanent retention of a trace element through redox and precipitation of iron oxides.

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