Study on Dispersion of TiO₂ Nanopowder in Aqueous Solution via Near Supercritical Fluids

In this study, we investigated the effects of near supercritical carbon dioxide (SCCO₂) parameters, including pressure, temperature, and saturation time on titanium dioxide (TiO₂) nanopowder dispersion in water-containing sodium hexametaphosphate (SHMP). The stability and morphology of TiO₂ particles dispersed in an aqueous solution were examined using a zeta potential instrument, dynamic light scattering, and transmission electron microscopy. As shown in the results, of particular interest, it was found that near SCCO₂'s pressure and saturation time had the strongest impact on TiO₂ dispersion in water-containing SHMP. This finding indicated that TiO₂'s secondary average particle size was significantly reduced with an increase in near SCCO₂'s pressure and saturation time. Additionally, in the presence of SHMP, the zeta potential of the as-prepared dispersion solution reached -53.7 mV because of production of the larger negative static charge repulsion force (resulting from SHMP dissociation) on the TiO₂ particle surface. The secondary average size was 127 ± 68 nm, indicating good stability of TiO₂ dispersed in water containing an inorganic dispersant.