The previous study demonstrated that bentonite had a deleterious effect on copper flotation by increasing pulp viscosity, but this deleterious effect could be mitigated by sea water (Zhang et al., 2015a). In this study, the effect of different cations,, Na+, K+, Mg2+ and Ca2+ with the same anion, Cl- on the rheology of a copper-gold ore in the presence of bentonite and copper flotation was investigated. It was found that the improvement of copper flotation in the presence of bentonite was generally dependent on the reduction of pulp viscosity by these cations. Divalent cations, Mg2+ and Ca2+, had a more significant effect on pulp viscosity and therefore copper flotation than monovalent cation, Na+, K+. These cations also interacted with bentonite, with residual cations modifying the froth property. However, this modification was less significant in copper flotation in the presence of bentonite where pulp viscosity played a critical role. (C) 2016 Elsevier Ltd. All rights reserved.