I have measured zeta potential for 1 weight percent dolomite (ca 50-50 weight percent of CaCO3 and MgCO3 and some small amount of Al2O3, Fe2O3 and
SiO2) powder in distilled water, and found it to be slightly negative from pH 7.5 to 10.5 (more negative at higher pH). Used the AcoustoSizer from
Colloidal Dynamics with the Smoluchowski equtaion.
My teacher find it a bit strange and expected it at least to be postive in the lower pH region.
Did the same type of experiment on calcite powder and got almost the same results as two phd students got one year ago (ZPC around pH 10.5).
Does anyone know what could make the zeta potential negative?
