Tkachenko N. The aggregative stability of aqueous suspensions of titanium dioxide

The results of complex investigation of aggregative stability and elektrokinetic properties of aqueous suspensions of the modified titanium dioxide of rutile type in the presence of 1-1-charged electrolytes (KF, LiCl, KBr, KCl, CsCl and LiF), polymethacrylic acid (Mw=35000 g/mol) and commercial surfactants TRITON X-100 or ATLAS G-3300 are discussed in the present work. Properties of aqueous suspensions of titanium dioxide with concentration of a solid phase 0,03-4,00 g/l have been studied in the wide range of changes of pH medium and concentration of the added substances. It is shown for the first time, that change of aggregative stability of aqueous suspensions of titanium dioxide around isoelectric point depends on ratio of ordering and disordering effects of water structure around ions of background electrolyte. It was demonstrated that the maximal stabilization of titanium dioxide suspensions modified by polymethacrylic acid is achieved under conditions of transition from weakly ionized compact chain conformation to strongly ionized expanded shape of a macromolecular coil. It is found, that the secondary processes which occur after interaction of surface groups with low molecular weight compounds of an aqueous medium, particularly with H+ and OH- ions, play an important role during stabilization of titanium dioxide suspensions by surface active substances such as TRITON X-100 or ATLAS G-3300. It is also shown for the first time that the shape of created aggregates is closed to spherical form under conditions of aggregative stability, and is different from spherical one upon decreasing of colloidal stability of investigated suspensions.