A fundamental study considering specific ion effects on the attachment of sulfide minerals to air bubbles

Bubble-particle attachment is one of the most fundamental sub-processes in froth flotation. It is of critical importance in achieving the separation of value from non-value. This sub-process is affected by many factors such as the chemistry of the pulp, action of the reagents, hydrodynamics and operational factors. Understanding the effects of these factors on bubble-particle attachment is thus crucial as they may in turn affect the mineral recoveries attained. With the current drive towards zero effluent discharge on mineral concentrators water quality is an important factor to understand as it can change the pulp chemistry and subsequently affect mineral recoveries. This study thus considers the effect of specific ions found in process water on the bubble-particle attachment of chalcopyrite and galena. Adsorption studies and zeta potential measurements were conducted to interpret the outcomes of the bubble-particle attachment tests. Pulps containing Ca²⁺ resulted in lower bubble-particle attachment probability and recovery of galena and chalcopyrite. Adsorption studies complemented the bubble-particle attachment findings well and showed that in Ca²⁺ containing waters, less xanthate was adsorbed on both the chalcopyrite and galena surfaces. The zeta potential measurements showed an increase in mineral potential with Ca²⁺ containing salts compared to the very negative mineral potential in NaNO₃. This work provides evidence of the passivation of the mineral surface with Ca²⁺; which hindered the adsorption of xanthate on the mineral surface in Ca²⁺ containing solutions and subsequently resulted in poor bubble-particle attachment.