Impact of environmental changes on uranium uptake by ferrihydrite synthesized from mine tailing leachate and its stability study

Exposure to uranium poses significant environmental and health risks, with remediation being particularly challenging in acidic, aerobic environments. Uranium transformation is closely linked to iron minerals via adsorption and co-precipitation. In this study, ferrihydrite (Fh-LS) was synthesized from mine tailing leachate via bioleaching followed by precipitation, presenting a potential approach that reuse mining waste. Compared to pure ferrihydrite, Fh-LS demonstrated enhanced uranium adsorption capacity, reaching 195.6 mg/g at pH 5.5 and 30 °C, and maintained stability over extended periods. FT-IR revealed that phosphate species in Fh-LS contributed to enhanced uranium uptake. Kinetics and isotherm analysis indicated that this adsorption process involves both physical and chemical interactions, occurring on a heterogeneous surface with varying affinities—supporting the potential for multilayer adsorption. Environmental factors including pH, coexisting ions, ion strength and temperature were investigated for their influence on uranium uptake and retention. U adsorption was impaired at pH < 4 but remained high above this threshold for 1 year. Higher amount of U retained in solid during desorption than that in adsorption at the same pH, which highlights irreversibility of the U adsorption. Most anions, particularly PO 4 3− and AsO 4 3− , exhibited a positive effect on uranium uptake and stability, whereas most of cations tend to negative impact, with Fe 3+ being a notable exception. These findings help develop low-cost, site-adaptable remediation strategies in uranium-contaminated mining areas and offer insights into uranium mobility in acidic, aerobic conditions that underpins fundamental processes key to the mitigation of uranium contamination in mining sites.