Synergistic insights into rare earth element affinity with unburned carbon in coal ash: A DFT mechanistic exploration

Rare earth elements (REEs) are vital but scarce, requiring alternative recovery methods. This study examines REE interaction with unburned carbon in coal fly ash (CFA). Flotation experiments isolated ∼24 wt% unburned carbon, enriched with heavy and critical REEs (HREEs and CREEs). Advanced analyses (XRF, XRD, TEM) confirmed 323 ppm REEs in the carbon matrix. Density functional theory (DFT) simulations revealed selective REE adsorption on carbon's functional groups. Findings suggest unburned carbon's strong affinity for HREEs and CREEs, presenting a sustainable REE recovery route from CFA and enhancing its role in resource recycling and environmental remediation.