Abstract
Raw bentonite (RB) from Saudi Arabia was grinded at different time (30, 60 and 120min) to evaluate stability changes of bentonite suspension due to induced progressive mechanical grinding. The mean particle size as well as the surface area and the zeta-potential (ζ) of the ground samples (G30, G60 and G120) were analyzed. Using the zeta-potential values, the maximum total interaction (VT/kTmax) between bentonite particles were calculated using DLVO theory to study the effect of grinding time on the stability of bentonite suspensions. The zeta potential of bentonite suspension in presence of different NaCl concentration was also investigated before and after mechanical grinding.
With increasing grinding time the bentonite retained its crystalline structure as indicated from FTIR spectroscopy experiments. A reduction in the mean particle size of bentonite leading to increasing the specific surface and the ζ-potential by grinding continued up to about 60min. After 60min of grinding (120min), the mean particles size increased, so the surface area and the zeta potential decreased as a result of particles starting a reaggregation process in which adhesion forces act. The zeta potential of ground bentonite suspension (G30, G60 and G120) in the presence of different concentrations of NaCl has higher values compared to RB. As the time of grinding increases, the (VT/kTmax) increases from 1102 for RB suspension to 2476 KT for G60 suspension; that is, the maxima of the total interaction energies increases≈2.5 times more than that of the RB suspension. In conclusion the grinding of Saudi bentonite is easier to make down as a stable suspension than raw bentonite and that it displays better physical and chemical properties for new application purposes.