Enhanced immobilization of U(VI) on Mucor circinelloides in presence of As(V): Batch and XAFS investigation

Highlights: • M. circinelloides presents high resistance to U(VI) and As(V). • Morphology of M. circinelloides changes obviously under U(VI) and As(V) stress. • U(VI) is mainly reduced to nano-uraninite without As(V). • As(V) hinders reduction of U(VI) due to the formation of Trögerite. The combined pollution of radionuclides and heavy metals has been given rise to widespread concern during uranium mining. The influence of As(V) on U(VI) immobilization by Mucor circinelloides (M. circinelloides) was investigated using batch experiments. The activity of antioxidative enzymes and concentrations of thiol compounds and organic acid in M. circinelloides increased to respond to different U(VI) and As(V) stress. The morphological structure of M. circinelloides changed obviously under U(VI) and As(V) stress by SEM and TEM analysis. The results of XANES and EXAFS analysis showed that U(VI) was mainly reduced to nano-uraninite (nano-UO₂, 30.1%) in U₄₀₀, while only 9.7% of nano-UO₂ was observed in the presence of As(V) in U₄₀₀-As₄₀₀ due to the formation of uranyl arsenate precipitate (Trögerite, 48.6%). These observations will provide the fundamental data for fungal remediation of uranium and heavy metals in uranium-contaminated soils.