Dispersion stability of titanium dioxide in aqueous isopropanol with polymer dispersant

Two polymer dispersants, polyester dispersant (PD) and sodium polyacrylate (NaPAA), were used to disperse titanium dioxide in 10% aqueous isopropyl alcohol (IPA). The effect of pH and zeta potential on the dispersibility of the titanium dioxide (TiO2) was studied via sedimentation. An optimum pH value of 8 for the two polymer dispersants in aqueous IPA suspension was found. The isoelectric point of the TiO2 particles was at pH 5.1 and pH 5.3 and shifted to lower pH in the presence of PD or NaPAA, with a greater decrease in zeta potential for the NaPAA suspension (- 36.5 to - 64.1 mV) due to the high degree of ionization compared with PD (- 36.5 to - 60.6 mV). The conformations of PD and NaPAA were strongly pH dependent: Their adsorption was highest at low pH and lowest at high pH, with the maximum adsorption of PD and NaPAA being 44.0 and 39.2 mg g(-1) at pH 3, respectively. It was shown that the stability of the suspensions was not only dependent on the pH but also on the zeta potential and molecular structure of the dispersant.