Activation flotation of lime-depressed pyrite with carbon dioxide: Performances, mechanism and pilot-scale application

Abstract

Activation flotation of lime-depressed pyrite by sulfuric acid (H2SO4) is usually accompanied by safety hazards and environmental pollution. Exploring eco-friendly, economical and effective activator to replace H2SO4 holds great significance for the sustainable development of mining industry. In this study, carbon dioxide (CO2) as a potential activator was applied in activation flotation of lime-depressed pyrite. Micro-flotation experiments results showed CO2 significantly improved the floatability of pyrite, and a maximum recovery of 93.94% was achieved under optimal operating conditions. The activation mechanism was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results indicated the depression of pyrite by lime was attributed to the formation of iron oxide/hydroxide species and calcium film, and CO2 effectively eliminated these hydrophilic compounds from the surface of pyrite, thus promoted the adsorption of xanthate onto the pyrite surface. Moreover, the anodic oxidation of xanthate on pyrite and the influence of CO2 on this process were investigated by cyclic voltammetry measurements. It was found that xanthate oxidation to form dixanthogen was more likely to occur in the presence of CO2, and this reaction replaced pyrite surface oxidation as the dominant anodic process. Finally, pilot-scale experiments were successfully conducted and the recovery of pyrite reached 93.18%, surpassing the ore dressing index of using H2SO4 as activator in actual production at the same period. Moreover, the concentration of sulfate ions in mineral processing wastewater was significantly reduced, and the annual cost of activator can be saved by 0.52 million RMB. The new process of activation flotation pyrite with CO2 has prospects for large-scale application in terms of activation performance, cost-effectiveness and environmental impact.