Tailored oxidised starch derivatives for enhanced selectivity of pyrrhotite depression in gold-copper flotation

• Starch was systematically oxidised using H 2 O 2 and NaClO to tailor its functionality. • H 2 O 2 oxidation produced carbonyl-rich while NaClO generated carboxyl-rich starch. • Flotation showed NaClO oxidised starch as the most effective pyrrhotite depressant. • Synch-XRD and DFT showed depression depends on functional groups, not pyrrhotite type. • Carboxyl groups play the key role in achieving strong and selective pyrrhotite depression. Pyrrhotite, a problematic gangue in gold–copper ores, l