Particle characteristics and their influence on dewatering of kaolin, calcite and quartz suspensions

Abstract

The effect of particle properties and dispersion on the filtration and dewatering behaviour of three different minerals namely kaolin, calcite and quartz in aqueous media have been examined. The primary particle properties such as particle size, size distribution, specific surface area, density, surface structure, dry bed porosities and sphericities of particles as well as their dispersion properties like solid concentration, pH and zeta potential have been considered. Quartz suspension shows higher settling rate and filterability (lower capillary suction time, CST) compared to calcite and kaolin at almost all solid concentrations and pH. The filterabilities of calcite and quartz are close to each other in the whole pH range and solid concentration. The settling and filterability of all three mineral suspensions showed dependence on slurry pH. The kaolin–water system showed strongest pH dependence in comparison to calcite and quartz–water system. Invariably, they all exhibited best settling and filterability characteristics at their respective point of zero charges (pzc). The vacuum filtration and dewatering characteristics of kaolin, calcite and quartz in aqueous suspensions in terms of cake permeability, specific resistance to filtration and cake saturation have been discussed on the basis of their particle size and its distribution, sphericity of the particles, bed porosity, water retaining capacities and the particle dispersion properties. Improved dewatering is observed near the pzc of each mineral.