Effect of Surface Charge on the Rheology of Concentrated Aqueous Quartz Suspensions

摘要

The viscosity of a suspension is determined not only by the medium and the particle concentration but also by the degree of aggregation of the primary particles. When these are well dispersed, either by the repulsive forces owing to high zeta potentials or by high shear (velocity gradients), the rheological behavior of the suspension is newtonian. The viscosity then approximates that of a suspension of spherical particles. Aggregation, whether a result of low zeta potential or the close proximity of the particles at high concentration, leads to increased viscosity and to such non-Newtonian phenomena as yield stress, shear thinning and, at extremely low shear to a time dependent strong increase inviscosity. The relatively high viscosity of a suspension of aggregates is caused by entrapment of fluid by the aggregates which makes the effective volumetric concentration of aggregates higher than that of the primary particles. The effective concentration of the aggregates is estimated from the maximum attainable concentration which is determined in a centrifuge experiment.