Redox potential control during flotation of a sulphide mineral ore

Redox potential (Eh) control can play a critical role during sulphide mineral flotation by influencing the reactions on the surface of the minerals and consequently the flotation behaviour. Such control is usually a combined function of dissolved oxygen and pH control but can also be achieved by using appropriate chemical modifiers. Batch flotation tests using sodium hypochlorite (NaCIO) as an oxidant were conducted to investigate its effect as an alternative means of varying redox potential in the pulp of a typical Merensky PGM ore. A change of pH from the natural ore pH of 9-11 lowered the Eh from an average value of 140 mV to values between 0 and 100 mV and resulted in a decrease in the amount of solids recovered. On the other hand increasing the Eh at constant pH resulted in a significant increase in solids and water recovery. It was observed that for copper there was no significant change in recovery for all the conditions investigated in this study. Ultimately this study has shown that using NaCIO to vary the redox potential in the flotation of a Merensky ore did not have any effect on recoveries but did result in a significant increase in the recoveries of solids and water.