Flotation Kinetics of Oxidized Lead–Zinc Ore in the Eh–pH System Using Calcium Polysulfide

The flotation of oxidized lead–zinc ores is challenging due to the low floatability of oxidized minerals and their weak interaction with conventional reagents. This study investigates the influence of pulp electrochemical parameters, namely redox potential (Eh) and pH, on the flotation kinetics of oxidized lead–zinc ore from the Koskuduk deposit. The results showed that sodium sulfide selectively activates lead-bearing minerals, increasing Pb recovery to 40.74%, while Zn recovery remains low at approximately 12%. In contrast, the polysulfide–lime system S:CaO:H2O provides more uniform and stable sulfidization of oxidized mineral surfaces, increasing recovery to 65.10% for Pb and 56.89% for Zn. The highest recoveries were achieved within an Eh range of −120 to −180 mV at pH 11–12. Kinetic studies demonstrated that the main contribution to metal recovery occurs during the first 2–6 min of flotation. These results indicate that flotation efficiency is controlled not only by reagent type but also by the electrochemical state of the pulp, confirming that calcium polysulfide is a promising alternative sulfidizing reagent for processing oxidized lead–zinc ores.