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