Abstract

The need to reduce fresh water consumption has pushed a number of mining companies to consider the use of seawater in their operations. At the same time, increasing amounts of fine particles in copper tailings unveil new operational challenges, in particular the thickening and transport of tailings featuring fine fractions that are predominantly clays. In the present paper, we study the role of salt water content in the flocculation efficiency of a copper sulphide tailings to which kaolinite were added. To mimic the water recovery stage in thickeners, flocculation has been induced in jar tests and the corresponding aggregate size distributions measured using a focused beam reflectance measurement (FBRM) probe, at various mean turbulence intensities. A fixed clay concentration and a coarse fraction tailing concentration typical of those encountered in thickener feedwells have been considered. Results show that for constant flocculant dosing, a measurable influence of the salt concentration on the resulting aggregation exists. Also, resulting optimal turbulence levels are reported. Trends are interpreted in light of the tailing composition and the role of DLVO forces in the process. In particular, zeta potential measurements of suspensions have been made. The implications on settling are discussed.