Changes in zeta potential of TiO2 and CaCO3 suspensions treated with a radiofrequency electric field as measured with a Zeta Plus instrument

Zeta potentials for titanium dioxide (Degussa, P 25) and calcium carbonate (Fluka; more than 99.0% pure) suspensions prepared in water or 0.01 M NaCl at different pH were measured after exposure to a radiofrequency (44 MHz) electric field for 5-30 min. The measurements were performed using a fully automatic Zeta Plus instrument which allowed the determination of the zeta potential at an exact time after the removal of the field, i.e. 5 or 10 min. These studies were performed in order to verify the previous results which were obtained by the classical microelectrophoretic method. It has again been proved that the field affects the zeta potential of the systems, it is believed by absorption of field energy which is then dissipated. Both the adsorption and the dissipation of the energy seems to occur in an oscillatory manner, as is reflected in time-dependent changes of the zeta potential. The observed zeta potential changes are probably due to a shifted adsorption-desorption equilibrium of the potential-determining ions.