Mechanistic insights into the facilitating transport of americium(III) by kaolinite colloid: An experimental and...

Deep understanding and accurate prediction of the transport behavior of minor actinides is crucial for ensuring the safety of the nuclear environment. Given the severe radiotoxicity and chemical toxicity of americium, its environmental mobility poses a significant long-term hazard. The environmental colloids can interact with actinides and potentially enhance the migration risk of actinides like Am(III) in environmental media. In this study, the interaction and co-transport behavior of kaolinite colloids (KCs) and americium under varying hydrochemical conditions were investigated using batch and column experiments, a site-blocking co-transport model was utilized to describe the co-transport behavior of KCs and Am(III). The results showed that the KCs significantly facilitated the transport of Am(III), and the facilitation efficiency depended primarily on the dispersion stability of the colloids, which was governed by the hydrochemistry factors. Humic acid (HA) could further increase the co-transport of colloid and Am(III) by enhancing the dispersion stability of the colloidal system, and the facilitation became more evident with increasing HA concentration. Additionally, the site-blocking co-transport model fitted well with the co-transport of KCs and Am(III), highlighting the significance of site blocking in colloids retention. This study offers the empirical data and theoretical insights necessary for the objective and precise assessment of environmental safety and the development of effective containment strategies for hazardous radionuclides like Am(III).