EFFECT OF pH AND PARTICLE CONCENTRATION ON THE RHEOLOGICAL BEHAVIOUR OF BENTONITE SUSPENSIONS

Abstract

The effect of the bentonite concentration and the pH on the rheological behaviour of bentonite suspension was studied in this research. Rheological measurement was done using the parallel plate rheometer. The rheological properties were measured at bentonite concentration of 1, 3 and 5 wt. % and it was found that shear stress and viscosity increase with increase in concentration of bentonite. The effect of pH of the suspension on the rheology was also significant. With increase in pH the viscosity and yield stress decrease until a minimum value at pH close to natural pH and then start to increase with increase in pH. Stability of the suspension was determined by dividing the suspension into 3 layers and conducting rheological measurements on each layer. Suspension was found to be unstable since all the 3 layers showed different behaviour. Herschel-Bulkley model was used to fit the experimental data and it fitted the data very well with high value of correlation coefficient. Influence of pH on zeta potential was also determined. Zeta potential was measured using Zeta Analyser which uses dynamic light scattering method to calculate the zeta potential. The absolute value of zeta potential decreased when the amount of HCl is increased. FE-SEM was also done along with determination of particle size distribution to get more details about the size and characteristic shape of the bentonite clay particles and it was found to have a layered structure.