Surface chemistry–microstructure–rheology of high and low crystallinity KGa-1b and KGa-2 kaolinite suspensions

Abstract

Abstract This study investigated the surface chemistry–microstructure–rheology relationship of two very well characterised, low impurity CMS source kaolinites; low defect KGa-1b and high defect KGa-2. The knowledge gained will improve the overall understanding by acting as a reference material for comparison with other studies. The trend of the yield stress–pH result was adopted to investigate kaolinite properties or factors that affect this trend. Both the KGa-1b and KGa-2 kaolinite slurries displayed similar zeta potential–pH and yield stress–pH behaviour. Crystallinity and particle size therefore did not affect the trend of the yield stress–pH and zeta potential–pH behaviour. The larger yield stress of the finer KGa-2 slurries is due to a higher particle concentration. Both kaolinite slurries exhibited a maximum yield stress at zero zeta potential. Their yield stress–solid volume fraction data were found to obey a power law model with the same exponent value of 3 accounting for a fractal dimension of 2.3 unaffected by pH. Cryo-SEM images of the vitrified microstructure of 35 wt% KGa-1b and 15 wt% KGa-2 suspensions at the maximum yield stress showed a 3-D microstructure formed by compacted clay aggregates which themselves are formed by a mixture of particle interaction configurations – face–face with stair–step feature and edge–face. Particle interaction modelling was discussed.