New insights into the reagent-removal mechanism of sodium sulfide in chalcopyrite and galena bulk flotation: a combined experimental and computational study

Abstract

To remove the adsorbed reagent of copper–lead mixed concentrate in bulk flotation, this study investigates the removal effect of sodium sulfide (SS) through micro-flotation, adsorption tests, equilibrium speciation analysis, electrochemical analysis, and first-principle density functional theory (DFT) calculations. Micro-flotation tests demonstrate that chalcopyrite and galena recovery remarkably decline by 50% and 70%, respectively, because of SS addition in a mineral–butyl xanthate (BX) flotation system. Meanwhile, adsorption tests reveal that with the addition of SS, the adsorption density of BX onto the surfaces of chalcopyrite and galena decrease to 0.0008 and 0.001 mg/g, respectively. These findings indicate that BX on the mineral surface almost completely desorbs. Electrochemical tests further show that in the BX–mineral system, combined with the oxidation peak, BX and mineral react to form CuX2/PbX2. After adding sodium sulfide, the above peak does not appear, indicating that BX does not react with minerals because of the effect of SS. The first-principle calculations based on the DFT further reveals the competitive adsorption mechanism between SS and BX on chalcopyrite (001) and galena (100) surface, thereby demonstrating the significant performance of SS as a removing reagent.