Abstract

Stabilization of synthetic clay-rich tailings in seawater with sodium polyacrylate (NaPA) has been studied by measurements of yield stress, viscoelastic moduli, zeta potential, and particle chord length distribution. The tailings are kaolin-quartz and sodium montmorillonite-quartz mixtures in seawater at pH 8 at which all surfaces are anionic. The yield stress of both tailings decays exponentially with the dose of NaPA. Reducing the initial value of yield stress to a preset fraction (1 - 1/e) requires 52 g/ton NaPA for kaolin-quartz and 31 g/ton NaPA for montmorillonite-quartz tailing. At these dosages, in the linear viscoelastic range, both tailings respond similarly to the presence of NaPA, increasing their liquid-like character and suspension stability. The stabilizing action of NaPA is supported by a slight increase of the negative zeta potential and a clear shift of the particle size distribution to the finer sizes. The underlying stabilizing mechanism involves steric-electrostatic repulsion of the clay particles. These results suggest an alternative to improve the management of clay-rich tailings in processes that use raw seawater at natural pH.