Preparation of nanometer titanium dioxide powders by hydrothermal method and their isoelectric points

Through the hydrothermal process at 200°C for 6h and using the metatitanic acid as reactant, the nanometer titanium dioxide powder were synthesized under different pH values adjusted by NaOH or HCl solution. The synthesized powders were characterized by Zeta potential, XRD and TEM. The TEM photographs show that the crystal structures are all anatase. The influence of pH on the isoelectric points of the synthesized titanium dioxide powders was studied and it shows that the pH conditions could influence the quantity of surface hydroxyl absorbed by the synthesized powders, thus influence the isoelectric points. Isoelectric points of the powders prepared in hydrothermal process with pH 1, 3, 5, 11, 13 are 5.5. and those in hydrothermal process with pH 7, 9 are 4.5. When the hydrothermal reaction is processed in the acid solution then the acidness of the reactant will be increased, and when the reaction is processed in the alkaline solution, then the increase will be the alkelity of the reactant.