Detrimental effect of calcium on grinding performance of a kaolin-containing ore

Abstract The presence of kaolin in ores may cause many problems in mineral processing industries. However, no study was conducted investigating the influence of kaolin on grinding efficiencies in any clay-containing ores. The primary objective of this research is to investigate the influence of kaolin on the grinding efficiency in the absence and the presence of Ca2+; the reason is that the presence of Ca2+ had already a positive effect on flotation and filtration of various clay containing ores. The experiments were performed using a rod mill to determine the grinding performance of the kaolin-containing ores by determining P80. The zeta potential measurements and the settling tests of pure kaolin were used to study the surface properties and the settling behaviour of pure kaolin particles. The rheology tests were used to analyse the changes in the slurry rheology of the products obtained after grinding the kaolin-containing ores. The results showed that the additions of Ca2+ ions reduced the repulsion forces between kaolin particles as confirmed by the zeta potential measurements as well as reduced settling rates. As a result, the agglomeration between kaolin particles increased, leading to the increase in the slurry shear stress (i.e., viscosity) and thus reducing the grinding performance significantly. The grinding performance was reduced by the addition of Ca2+ ions when there was a high clay percentage (40%) and a high solid percentage (70%). This paper demonstrated the importance of controlling Ca2+ concentrations in plant water to maximize the grinding performance of kaolin-containing ores.