THE EFFECT OF ELECTROLYTE CONCENTRATION AND PH ON THE FLOCCULATION AND RHEOLOGICAL BEHAVIOUR OF KAOLINITE SUSPENSIONS

The effects of the electrolyte concentration and pH on the settling behaviour, floc sizes and rheological behaviour of kaolinite suspensions were investigated. The results show that the settling behaviour of kaolinite changes with the ionic strength and pH of the suspension. In the acidic pH range, (pH 2) particles settle in flocculated form regardless of electrolyte concentration, however, in the basic pH range, the particles settle both, in dispersed form (at lower electrolyte concentrations) and in flocculated form (at higher electrolyte concentrations). The Bingham yield stress and time-dependent behaviour for these flocculated and deflocculated suspensions was investigated. In this study, the fundamental of structural kinetic model (SKM) was used to investigate the time-dependent viscosity behaviour of flocculated and deflocculated kaolinite suspensions. It was found that the kaolinite suspensions in the deflocculated form show viscosity time-independent behaviour with negligible Bingham yield stress. While, the flocculated suspensions show marked non-Newtonian time-dependent behaviour. This work has been very successful in establishing the link among particle-particle interactions, floc size, Bingham yield stress, breakdown rate constant, and extent of thixotropy.