Rheological behavior of muscovite clay slurries: Effect of water quality and solution speciation

In a number of unit operations (e.g., leaching and dewatering) used for valuable metal (e.g., copper, gold) recovery from mineral ores, the process water quality may significantly impact on slurriesʹ rheological behavior. In this study the effect of dissolved ionsʹ type (Al(III), Fe(III), Cu(II) and K+) and concentration on muscovite slurriesʹ interfacial chemistry modification and rheological behavior was investigated in the pH range 3–10 and 25 °C. At alkaline pH, specifically adsorbed metal ions and/or their surface nucleated hydroxide products dominated the particlesʹ interfacial chemistry leading to formation of weak to moderate gelform slurry. The higher shear yield stresses displayed in the pH range 5–10, is attributed to enhanced van der Waals attraction and emergence of additional attractive forces (e.g., electrostatic-charge patch, adsorbed ion-particle bridging, surface nucleation and cementation). At pH < 4, however, the mineral surface chemistry changes were consistent with adsorbed hydrated metal ions and slurry displayed dispersed sol behavior due to repulsive hydration or structural forces. The extent of slurry shear yield stress enhancement/attenuation, induced by particlesʹ zeta potential changes, strongly depended upon pH and metal ionsʹ type and concentration. At high ionic strength (0.10–0.60 M), the metal ion mediation decreased in the order of Al(III) > Cu(II) > Fe(III) > K+ for zeta potential and Fe(III) > Cu(II) > Al(III) > K+ for pulp rheology. At low ionic strength (0.01–0.06 M), whilst the metal ion-mediated zeta potential changes followed the same order, for rheology enhancement it changed to Cu(II) > Al(III) > K+ > Fe(III).