Robust adsorption of ellagic acid on galena surface for efficient flotation separation of molybdenite and galena

Abstract

The efficient flotation separation of molybdenite and galena is challenging due to their similar surface chemical properties. In this study, ellagic acid (EA), a biodegradable small molecule, was investigated as a novel depressant for selectively modifying the surface chemistry of galena in its flotation separation from molybdenite. Flotation experiments revealed that EA effectively depressed galena at pH 9, while maintaining molybdenite recoveries above 90%. In artificially mixed mineral tests, molybdenum recovery in the froth exceeded 98%, while lead recovery dropped to 6.34%. Surface chemistry analyses, including zeta potential and contact angle measurements, revealed that EA preferentially adsorbed onto the galena surface, decreasing its hydrophobicity and hindering collector adsorption. Solution chemistry calculations and UV spectroscopy identified the doubly deprotonated form of EA as the dominant species at pH 9. Further insights from FT-IR, XPS, and DFT calculations confirmed that EA chemisorbs onto galena through specific deprotonated sites, forming a Pb–cO–C chelate structure, which selectively modifies galena’s surface properties and enhances the wettability contrast between galena and molybdenite. These findings suggest that EA has strong potential as an environmentally friendly alternative to conventional galena depressants.