Interactions of clay minerals in copper–gold flotation: Part 2 — Influence of some calcium bearing gangue minerals on the rheological behaviour

This paper describes the results of research investigating the interaction between clay minerals and calcium bearing gangue minerals using rheological measurements. This study was motivated by the high viscosity values observed in a copper–gold ore from which the flotation response of copper and gold minerals was poor and follows on from previous research investigating the effect of pH modifiers such as lime, sodium hydroxide and soda ash on the rheology of clay minerals (Cruz et al., 2013). It was found that Ca2 + ions interacted strongly with kaolinite and illite in enhancing their rheological properties. Gypsum was found to have the highest solubility in water and released the largest quantity of Ca2 + ions resulting in a significant interaction with illite and kaolinite. Calcite and dolomite were found to be less soluble and exhibited a lower interaction with these clay minerals. This study also investigated the interaction of the three calcium bearing minerals with bentonite, a swelling clay mineral. Gypsum had the greatest interaction with bentonite as well but affected the rheological characteristics of bentonite in the opposite way to that observed with illite and kaolinite. Ca2 + ions released from gypsum dispersed bentonite slurries by preventing the swelling of this clay mineral. This study suggests that when looking at ores with clay minerals, it is important to consider the potential input from other gangue minerals for the interactions in determining the rheological behaviour.