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 carbo nate (Fluka; more than 99.0% pure) suspensions prepared in water or 0. 01 M NaCl at different pH were measured after exposure to a radiofrequ ency (44 MHz) electric held for 5-30 min. The measurements were perfor med using a fully automatic Zeta Plus instrument which allowed the det ermination 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 micr oelectrophoretic method. It has again been proved that the held affect s the zeta potential of the systems, it is believed by absorption of f ield energy which is then dissipated. Both the adsorption and the diss ipation of the energy seems to occur in an oscillatory manner, as is r eflected in time-dependent changes of the zeta potential. The observed zeta potential changes are probably due to a shifted adsorption-desor ption equilibrium of the potential-determining ions.