Modulation of selectivity between copper and zinc minerals using electrochemical potential of the pulp

Electrochemical effects occurring in the processing of the A-1 zone copper-zinc-silver-pyrite ore from Les Mines Selbaie, Joutel, Québec, were investigated and correlated with the redox potentials measured in flotation pulps using a gold sensing electrode. On-line pulp potential measurements at the head of the copper flotation circuit were performed over a period of nearly one year. Windows of selectivity between the copper and zinc minerals were observed but the leading edge, and the width of the window were affected by the state of the sensor. Procedures for the verification of the state of the on-line sensor were established to ensure long term reliability of sensor. Sensitivity analysis of the pulp potential to modifiers, such as lime and sodium cyanide, suggested that these reagents could be controlled using the measured pulp potential to maintain the oxidation-reduction state of the pulp within the window of selectivity. A shorter study at the Kidd Creek concentrator indicated the presence of a window of selectivity between copper and zinc minerals but the leading edge and width of the window were different than that observed at Les Mines Selbaie. This suggests that the windows of selectivity are affected by ore and plant specific variables.; Laboratory investigations on feed pulp samples demonstrated that collectorless flotation of the copper minerals was a significant contributor to copper recovery in the A-1 zone circuit. Unfortunately, collectorless copper recovery was limited to around 60% and only a small proportion of the silver could be recovered in this fashion. The addition of collectors such as Aerophine 3418A (sodium di-isobutyl dithiophosphinate) or sodium isopropyl xanthate (SIPX) was required to achieve high recoveries but the selectivity response of these two collectors was different. The selectivity obtained with SIPX could be manipulated by modulation of the pulp potential before or after introduction of the collector. However, Aerophine 3418A exhibited an irreversibility in that an oxidation of the pulp before its introduction usually lead to a decreased selectivity even if the pulp potential was reduced prior to flotation.