Abstract

In the copper sulfide beneficiation process, recovery can be challenged by the presence of clays in the feed. Their occurrence has shown to become increasingly important, due to the nature and ageing of the deposits being currently mined, with subsequent requirement of finer grinding. This has implied problems in almost every stage of the mineral processing value chain (MPVC). It has been shown that different kind of clays have different effects on particular stages of the MPVC, suggesting that special attention must be payed to the mineralogy. As different clay minerals may have differing properties (e.g. shape and cation exchange capacity and size), their response under similar process conditions (e.g. solid concentration, milling grade, ion presence and shear rate) will not necessary be the same, and identifying how they explain the variability on the desired on key output variables of the operation, would be central for a successful control and operational philosophy. Due to its major impact on water recovery, in the present work we focus on tailings. Using synthetic copper sulfide tailings, we explain the role that some clays, exemplified herein with blends of kaolinite and bentonite, play in the modification of the rheological and physicochemical properties of the tailing’s suspension. To decouple and characterize the contributions of (1) the particle size and average shape of the solid fraction, (2) effect of adding the clay species to a pure silica tailing and (3) possible synergistic interactions between both clays studied, a number of clay content scenarios have been considered. The rheological behavior and variations of critical parameters such as apparent yield stress, viscosity and effective packing fraction, were studied in light of existing models. The effect of kaolinite and bentonite on the suspension rheology was quantitatively different, and it was also non-additive, suggesting the existence of more complex interactions between the clay species, clay and silica and/or clay and bulk fluid.