Sequential yield stress and zeta potential measurements on the same suspensions for platelet and spherical alumina

This investigation aims to answer the vexing question that has been with the colloidal science community for a long time, on whether we can use zeta potential data of dilute suspension to correlate with rheological parameters obtained at a much higher solid loading where the mismatch of surface properties is one of the main issue. In this study, sequential yield stress and zeta potential measurements were conducted on moderately concentrated alumina suspensions with different particle shape; spherical and platelet. The surface properties of the suspensions were varied by pH. The zeta potential–pH behaviour of the moderately concentrated suspension with a yield stress and of the dilute suspension was found to be identical for platelet alumina. The agreement was considered good for the spherical alumina in the pH range of 6 to 12. The correlation between the yield stress and the square of the zeta potential data was found to obey the yield stress–DLVO model for both platelet and spherical particles. This was found to be identical to the correlation evaluated from the yield stress and zeta potential data obtained from separate dilute and concentrated suspensions. The critical zeta potential characterising the flocculated–disperse state transition was found to be ∼40 mV for both spherical and platelet particles.