Recovery of chalcopyrite from galena using ellagic acid as a lead-selective and environmentally friendly inhibitor: experimental and mechanistic insights

This study explores the selective application of an environmentally friendly organic inhibitor, ellagic acid (EA), in the flotation separation of galena from chalcopyrite. Single-mineral flotation experiments revealed that the galena flotation recovery significantly decreased from approximately 95% to 6.16% following the addition of EA, whereas chalcopyrite maintained a high recovery of approximately 95%. In artificial mixed-ore flotation, effective separation was achieved under optimized conditions. This yielded a Cu concentrate with a Cu grade of 29.73% and recovery of 95.67%, and a Pb grade of 8.39% with a recovery of 8.62%, resulting in a separation index of 15.30. Comprehensive analyses were conducted using various techniques including X-ray photoelectron spectroscopy, density functional theory calculations, zeta potential measurements, time-of-flight secondary ion mass spectrometry, xanthate adsorption capacity measurements, and contact angle measurements. These analyses suggested that selective EA adsorption on the galena surface is the key mechanism underlying the separation. Under alkaline conditions, the deprotonated phenolic hydroxyl groups in EA preferentially interact with Pb sites on galena, increasing the surface hydrophilicity via the formation of –OH groups, oxides, and sulfur oxides. These interactions effectively occupied the active sites on the galena surface, inhibiting xanthate adsorption. However, EA exhibited minimal influence on the surface chemistry of chalcopyrite and its interaction with collectors, thereby enhancing the wettability difference between the two minerals. These results demonstrated the feasibility of effectively separating these minerals using the proposed approach.