Roasting-derived Ce7O12 interface enables selective citric acid binding for flotation separation from monazite

Selective flotation separation of bastnaesite and monazite remains challenging because their intrinsic surface-chemical contrast is weak under conventional reagent regimes. Here, an air-roasting-induced phase transformation strategy was developed to reconstruct the bastnaesite surface and create a chemically addressable Ce 7 O 12 interface for selective separation from monazite. Roasting converted bastnaesite into Ce 7 O 12 with surface reconstruction, elemental redistribution, and Ce 4+ enrichment, whereas monazite remained comparatively stable. In the citric acid (CA)-octyl hydroxamic acid (OHA) system, Ce 7 O 12 showed a much stronger depression response, while monazite retained high floatability; the recovery gap between monazite and Ce 7 O 12 increased from 9.20 to 31.39 percentage points after CA addition. Binary flotation further yielded a monazite concentrate with 60.08% grade and 83.21% recovery, while Ce 7 O 12 recovery was only 16.36%. FT-IR, XPS, AFM, and DFT analyses indicate that the Ce 4+ -enriched Ce 7 O 12 surface preferentially binds CA, leading to active-site occupation and restricted subsequent OHA adsorption. These findings highlight roasting-derived Ce 7 O 12 interface construction as an effective route for converting weak intrinsic mineral contrast into reagent-addressable flotation selectivity.