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

Abstract

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.

Magnetite precipitation approach for zinc hydrometallurgy: a microfluidic strategy

“…The adsorption of the metal ions and the promotion of the doping behavior of these intermediates have been extensively studied, especially for ferrihydrite. 34–36 Compared to MF-35, S35-I exhibits a more complex presence of intermediates in the composition. As the reaction time is extended to 600 s, the unstable intermediates persistently transform into magnetite, reaching a comparable level with the microfluidic method.…”

Natural Attenuation of Groundwater Uranium in Post-Neutral-Mining Sites Evidenced from Multiple Isotopes and Dissolved Organic Matter

“…Although neutral in situ leaching (ISL) is an economically advantageous mining method for extracting low-grade sandstone uranium (U), , restoration of affected groundwaters to premining (baseline) water quality is subject to considerable uncertainty. U­(VI) can be removed from groundwater by sorption, precipitation, and reduction, which are expected to play an important role in U natural attenuation. − Reduction of U­(VI) is preferred due to its long-term stability, which converts U­(VI) to U­(IV) and precipitates from solution. , Sandstone-hosted U deposits are commonly associated with reductants (e.g., pyrite and OM). − Multiple electron donors (e.g., OM and pyrite) and biogeochemical processes (e.g., sulfate bioreduction) can promote U­(VI) reduction. , …”

Mesoporous Layered Double Hydroxides: Synthesis for High Effective Uranium Ions Sorption from Seawater and Salt Solutions on Nanocomposite Functional Materials

“…This is due to the existence of many uranyl carbonate forms (such as UO 2 CO 3 (aq), UO 2 (CO 3 ) 2 2− , and UO 2 (CO 3 ) 3 4− ). At high concentrations, they cause a process of electrostatic repulsion between the surface of the adsorbent and UO 2 2+ [22][23][24][25]. Due to its ability to adsorb radionuclide ions through surface deposition, ion exchange, and isomorphic substitution mechanisms, LDH is considered an effective material for radioactive wastewater treatment [26].…”