Uranium retention on iron oxyhydroxides in post-mining environmental conditions

Investigating uranium migration mechanisms related to the weathering of waste rocks is essential for developing strategies that can address the potential environmental issues caused by uranium mining. This work is based on environmental samples containing 2 L ferrihydrite, lepidocrocite and goethite collected in the technosols from granitic waste rock piles, mine drainage conduits and mine waters. The results show the important role of iron oxyhydroxide in U immobilization and re-concentration. EXAFS spectroscopy combined with mineralogical and geochemical studies (Scanning electronic microscopy, Wavelength-dispersive X-ray spectroscopy microprobe, inductively coupled plasma - optical emission spectrometry/mass spectrometry and X-ray diffraction) allowed for the identification of uranyl ternary surface complexes at the ferrihydrite surface that were either composed of phosphate groups or organic matter. Moreover, goethite and lepidocrocite were also identified as a secondary trap for U immobilization. U(VI) is known to be mobile in oxidizing conditions. This study highlights the control of the uranyl mobility by various iron oxyhydroxides in supergene conditions. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Investigating uranium migration mechanisms related to the weathering of waste rocks is crucial for addressing potential environmental issues caused by uranium mining. This study showed the important role of iron oxyhydroxides in immobilizing and concentrating uranium, with uranyl ternary surface complexes identified at the ferrihydrite surface. Additionally, goethite and lepidocrocite were found to be secondary traps for U immobilization.