Effect of 1-1-charged ions on aggregative stability and electrical surface properties of aqueous suspensions of titanium dioxide

Abstract

Dependencies of zeta potential of titanium dioxide particles and aggregative stability of its aqueous suspensions from pH in the solutions of alkaline metals halogenides: KF, KCl, KBr, LiF, LiCl and CsCl have been investigated. It has been shown that the dependence of zeta potential of titanium dioxide particles on the pH medium has a typical character, which is natural for the suspensions of amphoteric oxides of metals with isoelectric point of the medium at pH 3.60 for LiF, 6.00—LiCl, 6.10—KF, 6.21—CsCl, 6.35—KBr, 6.70—KCl. It has been established that displacement of isoelectric point depends on the relation of the hydrated ions charge to their radii. It has been found that aggregative stability of aqueous suspensions of titanium dioxide at isoelectric point is not the lowest, as it is to expect from the classical DLVO theory. Aggregative stability for KF and LiCl is even the highest at isoelectric point and commensurate with aggregative stability in the alkali region, where it is the best for all the salts in question. Aggregative stability at isoelectric point in solutions KCl, KBr and CsCl is somewhat lower compared to KF and LiCl, and the region of better stability is located left of isoelectric point, while for LiF it is located right of isoelectric point. These deviations of aggregative stability at isoelectric point from the classical DLVO theory are discussed taking into account the ability of background electrolyte ions to put into order or disorder the water structure.