Abstract:
TiO2 was treated with inorganic and organic surface agents under different conditions and the aim was to improve the qualities of the pigment and to determine the role of the adsorbed hydroxyl ions in these qualities. Good dispersion and durability are two important qualities in the TiO2 pigment industry that are investigated in this study. It is a difficult matter to quantify the effectiveness of the coating, but in this study the surface treatment of TiO2 was evaluated by using sedimentation and the degradation of methylene blue. Surface area measurements, zeta potential measurements and infrared spectroscopy were used to characterize the TiO2 surface. The surface area of treated TiO2 powders showed that the alumina-bearing chemical and the precipitation procedure have a tremendous effect on the morphology of the coating and therefore also on the qualities of the final pigment. The large negative zeta potential values reported for silica treated samples, are responsible for the good dispersion stability while structural viscosity, created by hydrogen bonding, is responsible for the stability in organic treated samples. This study proved that hydroxyl and water molecules, adsorbed on the surface, play a very important role in the dispersion stability and photo-activity of the TiO2 pigment. For optimum pigment qualities it is therefore important to control the terminal hydroxyl groups on the rutile surface by surface treatment
