Electrokinetic potentials of Al2O3 in concentrated solutions of metal sulfates.

The zeta potentials of alumina (10% by mass dispersions) in 0.1-1 M solutions of metal sulfates were determined by means of the electroacoustic method. The background correction was used to account for the electroacoustic signal of the electrolyte. The zeta potentials in the solutions of alkali sulfates were in the range from -8 to -19 mV. They were rather insensitive to the pH (4-9.5), and to the nature and concentration of the salt. In MgSO(4) solutions (0.05-0.5 M, pH 4-8), the zeta potentials were also negative (-3 to -9 mV) showing the preference of alumina to adsorb sulfate anions rather than magnesium cations.