Precipitation of nanosized titanium dioxide from aqueous titanium(IV) chloride solutions by neutralization with MgO

Aqueous titanium (IV) chloride solutions were neutralized to different terminal pH (2.5 to 6.0) with magnesium oxide as base at 95 °C and were found to yield nanosized titanium dioxide. The produced materials were compared to those obtained by simple forced hydrolysis. The techniques of XRD, TGA–DTA, FT-IR, BET, SEM and TEM were applied for the characterization of the produced materials. Honeycomb-shaped uniform nanosized crystalline TiO2 powders with aggregate particle size of about 50 nm were successfully obtained by neutralization with magnesium oxide. Phase-pure rutile or mixed rutile and anatase crystalline TiO2 powders were precipitated with proper selection of conditions. It was found that forced hydrolysis at 95 °C favors the formation of rutile TiO2. Rutile TiO2 powders with different crystallite sizes between 11 and 18 nm were obtained from aqueous TiCl4 solutions with Ti concentration ranging from 0.5 mol/L to 2.0 mol/L. Neutralization with MgO at 95 °C, on the other hand, favored the formation of mixed anatase and rutile materials. The anatase fraction (ranging from 0 to 70%) increased with pH elevation (from 2.5 to 6.0). The neutralization method yielded much higher titanium precipitation efficiency (up to 100%) than simple forced hydrolysis. The magnesium content in the TiO2 products was found to increase with a rise in the final pH due to partial hydrolysis of magnesium. It was less than 0.1% when the final pH was kept at or below 3.3.