A green organic depressant for chalcopyrite and galena flotation separation: application and mechanism of levodopa

L-dopa was used as a green depressant for chalcopyrite/galena separation. • Galena was selectively depressed while chalcopyrite maintained high floatability. • L-dopa preferentially increased galena hydrophilicity and blocked collector adsorption. • L-dopa selectively interacted with the galena surface via strong chemisorption. • L-dopa anchored to active surface Pb sites by forming stable Pb–O bonds. Flotation separation of chalcopyrite and galena is challenging due to their similar surface physicochemical properties. This study investigated levodopa (L-dopa) as an eco-friendly and selective depressant for this Cu–Pb sulfide system. The depression mechanism was evaluated using micro-flotation, contact angle, Zeta potential, XPS, AFM, ToF-SIMS, and DFT calculations. Flotation results showed that under low-alkaline conditions with 5 × 10 −4 mol/L L-dopa, galena recovery decreased to 2.99% while chalcopyrite recovery remained above 90%. Artificially mixed-mineral flotation successfully separated galena and chalcopyrite, yielding a copper concentrate with over 30% Cu grade and 85% recovery. Surface analysis revealed that L-dopa preferentially adsorbed onto galena, enhancing its hydrophilicity and blocking xanthate collector adsorption, whereas its impact on chalcopyrite was minimal. DFT calculations confirmed that L-dopa bound to Pb sites via its carboxyl oxygen atoms to form stable Pb–O bonds. The interaction energy on galena reached –196.83 kJ/mol, indicating a strong chemisorption process. These findings demonstrate that L-dopa functions as a highly effective, selective depressant for galena, elucidating its potential for the clean separation of Cu–Pb sulfide minerals. Download: Download high-res image (160KB) Download: Download full-size image