Muscovite clay mineral particle interactions in aqueous media

Abstract

Particle interactions and colloid stability of aqueous clay mineral dispersions play a pivotal role in many unit operations and plant processes (e.g. crystallization, leaching, slurry transport and dewatering). In this study, the nature of the particle interactions, colloid stability and shear rheology of dilute (< 0.1wt.% solid) and concentrated (8–57wt.% solid) muscovite clay mineral dispersions have been investigated under a variety of industrially relevant process conditions in the pH range 1–10. Particle zeta potential profile was found to be distinctly pH-history and pulp solid loading and chemistry mediated, reflecting different isoelectric points and colloid stability at different pH values. For dilute dispersions, muscovite particle zeta potential followed pH-dependent electrokinetic trends typical of siliceous minerals which indicated an isoelectric point (iep) at ~pH 2. For concentrated dispersions, on the other hand, the magnitude of negative particle zeta potentials was markedly lower and the concomitant ieps were significantly higher (in pH range 5–7) compared with the dilute dispersions. Isothermal, batch settling behavior and dispersion rheology for fresh dispersion at pH >3 reflected the predominance of interaction energy potentials of attractive van der Waals and repulsive electrical double layer forces' origin. The particle interactions may be theoretically treated and rationalized in the manner of DLVO theory. At pH <3 and aging at pH 7, completely different trends emerged due to incongruent leaching of the muscovite particles which led to the development of non-DLVO particle interactions.