Chemical synthesis of titania (TiO2) powder via mixed precursor route for membrane applications

Controlled chemical reaction between titanium tetrabutoxide and oxalic acid at room temperature in non-aqueous medium was utilized to obtain a mixed precursor with composition [(TiOC2O4·2.5H2O)0.8+(Ti(OH)4)0.2]. Various physico-chemical techniques namely micro and chemical analyzes, XRD, DTA/TGA/DTG, SEM, Mercury porosimetry were employed to characterize mixed precursor as well as TiO2 obtained by its pyrolysis. The pyrolysis was carried out under controlled conditions in air at (T=400°C/2 h shown by thermal analysis) to obtain anatase (TiO2) powder. This powder consisted of mainly two types of agglomerates having spherical shapes with sizes ≈0.1 and ≥0.3 μm. Further, green disks made from the powder were sintered at 1000°C/2 h in static air to obtain mechanically stable TiO2 membranes with 60% porosity. SEM studies on the same revealed uniform microstructure with 200–500 nm grain size. The sintered material has thermodynamically stable rutile phase, confirmed by XRD. Mercury porosimetry measurement indicated that most of the pores have pore radius between 2 and 10 nm with a few pores of radius between 100 and 400 nm. These membranes have bubble point radii between 1.0 and 7.75 μm and average pore radii from 0.4 to 1.0 μm depending on the sintering and annealing conditions.