• PVAc selectively flocculates ultrafine talc from chalcopyrite, enabling efficient reverse flotation separation at a dosage of 40 mg/L.
• Hydrogen bonding between PVAc ester groups and talc surface hydroxyls drives selective flocculation, while chalcopyrite lacks binding sites.
• PVAc adsorption enhances talc hydrophobicity and promotes bubble-particle attachment by shifting interaction energy from repulsive to attractive.
• The study provides mechanistic insights into floc-flotation coupling, expanding the use of ester-based polymers for ultrafine mineral recovery.