Selective depression of Pb2+-activated sphalerite by potassium ferricyanide in Pb-Zn sulfides flotation separation

The depression of sphalerite in the flotation separation of galena and sphalerite is usually difficult, especially when sphalerite is activated by Pb2+ ions dissolved from lead-bearing minerals. In this study, the cheap, efficient, and environmentally friendly regent of potassium ferricyanide (K3[Fe(CN)6]) was used for the first time to efficiently separate galena from Pb2+-activated sphalerite at neutral pH. Micro-flotation experiments, adsorption tests, contact angles, zeta potential analysis, X-ray photoelectron spectroscopy (XPS) analysis, and time-of-flight secondary ion mass (ToF-SIMS) were performed to investigate the depression mechanism of K3[Fe(CN)6]. The micro-flotation test results showed that K3[Fe(CN)6] had a considerable depression effect on Pb2+-activated sphalerite. Adsorption tests showed that competitive adsorption between K3[Fe(CN)6] and sodium butyl xanthate (SBX) on the sphalerite surface reduced the amount of SBX adsorbed on the surface of Pb2+-activated sphalerite, thereby depressing sphalerite. Contact angles analysis indicated that K3[Fe(CN)6] treatment reduced the contact angle of Pb2+-activated sphalerite surface and weakened its hydrophobicity, providing a favorable condition for the separation of galena and Pb2+-activated sphalerite. Zeta potential measurements suggested that the K3[Fe(CN)6] effectively prevented the adsorption and interaction of sodium butyl xanthate (SBX) on the surface of Pb2+-activated sphalerite. Time-of-flight secondary ion mass (ToF-SIMS) and XPS analysis indicated that K3[Fe(CN)6] could chemisorb onto the Zn sites on the surface of Pb2+-activated sphalerite and form hydrophilic precipitates containing Zn3[Fe(CN)6]2, Zn3K2[Fe(CN)6]2, and Pb(OH)2, which further generate a hydrophilic passivation layer, and reduced the floatability of Pb2+-activated sphalerite.