Pyrite activation in seawater flotation by copper and lead ions: XPS and in-situ electrochemical investigation

[Display omitted] •Flotation recovery of pyrite in seawater flotation system was improved by Cu2+/Pb2+.•Copper species reacted with pyrite surface to form Fe-S-Cu(I) and Fe-O-Cu(II).•Lead species reacted with pyrite surface to form Fe-SO-Pb(II) and Fe-O-Pb(II).•Adsorption of xanthate decreased the conductivity of pyrite surface in seawater.•Reaction between pyrite and xanthate was enhanced in seawater after Cu2+/Pb2+ activation. Pyrite, as the main carrier of gold, can be collected via flotation which consumes high volumes of fresh water. Seawater is the promising alternative to fresh water, especially in the fresh water deficient regions. However, pyrite flotation is usually ineffective in seawater, which requires activation prior to recovery. This study mainly focuses on the roles of Cu2+ and Pb2+ on pyrite flotation in seawater. The flotation and contact angle results indicated that Cu2+ and Pb2+ obviously increased pyrite recovery in seawater by enhancing its surface hydrophobicity. Further XPS studies revealed that the formation of Fe-S-Cu(I) and Fe-O-Cu(II) on pyrite surface due to Cu2+ activation while the presence of Fe-O-Pb(II) and Fe-SO-Pb(II) due to Pb2+ activation, thereby improving the active sites and adsorption of xanthate. In addition, the in-situ scanning electrochemical microscopy (SECM) results showed that the formation of Cu2+ and Pb2+ activated products increased the electrochemical reactivity of pyrite surface, which was the main reason for the improved pyrite floatability. Moreover, the current consequence evolution indicated that pyrite activation by Cu2+ was stronger than that by Pb2+. The SECM imaging also showed that the adsorption of xanthate decreased the electrochemical reactivity on pyrite surface, with more significant role observing on the activated surface than that of the un-activated pyrite. It should be noted that the Cu2+/Pb2+ activation and xanthate adsorption were distributed unevenly on pyrite surface. This study therefore provides an in-situ approach to understand the role of inorganic ions and reagents on pyrite flotation in seawater, providing a promising strategy to use seawater for the flotation recovery of gold.