Bioremediation potential of dominant microalgal strain from uranium-contaminated sites: Biosorption behavior and...

Microalgae widely present in natural water bodies have demonstrated great potential for removing heavy metals and radionuclides. Understanding the biosorption behavior and mechanisms of uranium accumulation by microalgae is essential. In this work, Acutodesmus sp. strain (a dominant microalga group in uranium-contaminated water) was isolated from a uranium tailing and used to explore the biosorption behavior and possible mechanisms. The results showed more than 95 % of uranium could be removed efficiently by Acutodesmus sp. and the removal efficiency remained above 80 % after 18 days. The biosorption was a monolayer and chemical process, which could be well described by pseudo-second-order kinetics and Langmuir isotherm models. Moreover, the microalgae can remove 79.68 % of uranium from uranium tailing water, exhibiting great potential for practical application. Micromorphological analysis revealed that uranium was uniformly distributed extracellularly and heterogeneously accumulated intracellularly. Uranium is primarily deposit in some intracellular regions and gradually accumulated over time in the form of amorphous, needle-like deposits. Furthermore, FTIR, XPS and EXAFS analyses indicated that the adsorbed uranium was primarily complexed with phosphate groups. Overall, this study can provide new insights into uranium biosorption in the microalgae and reference for the treatment of uranium mine wastewater.