The Behavior of Zeta Potential of Silica Suspensions

Zeta potential is one of the most relevant parameters controlling the rheological behavior of ceramic suspensions. In this work, it was observed that for pH values below the isoelectric point (IEP), the positive value of zeta potential of water suspensions of alpha -quartz and alpha -cristobalite, experiences a sudden steep increase with the increase in specific surface area of the powders. For pH values above the IEP, the zeta potential values of crystalline forms of silica ( alpha -quartz and alpha -cristobalite), get gradually more negative with the increase in pH. Conversely in the case of vitreous silica, for pH values above 6, there occurs a steep change towards more negative values of zeta potential than those presented by quartz and cristobalite. These findings have not yet been accounted for in the DLVO theory but may provide subsidies for better understanding of how to stabilize and destabilize crystalline and vitreous silica water suspensions.