Preparation of porous TiO2/silica composites without any surfactants

TiO{sub 2}-SiO{sub 2} composites, with high specific surface area (up to 308 m{sup 2}/g), large pore volume, and narrow distribution with average pore sizes of 3.2 nm, have been synthesized from wollastonite and titanium sulfate in the absence of any surfactants. Calcium sulfate, a microsolubility salt, plays an important role in the formation of pores in this porous TiO{sub 2}/silica composite. The microstructure and chemical composition of composite were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM) equipped with energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectrometer (XPS) and N{sub 2} adsorption and desorption analysis. The as-prepared porous titanium dioxide-silicon dioxide composites with high specific surface area and well-crystallized anatase contents were used as an efficient photocatalyst. - Graphical abstract: TiO{sub 2}-SiO{sub 2} composites have been synthesized from wollastonite and titanium sulfate in the absence of any surfactants. In acid Ti(SO{sub 4}){sub 2} solution, Ca and Si ions in chain-like wollastonite could dissolve into the bulk solution and slightly soluble CaSO{sub 4} crystal phase and silicic acid formed. The concentration of the titanium species in the reaction solution is expected to increase with the hydrolysis process, nucleation starts. After the start of the nucleation, a very small amount of TiO{submore » 2}, silicate and CaSO{sub 4} particle deposited together and formed composites. Some cavities formed during the washing step through the dissolution of CaSO{sub 4} crystal phase. The bulk of the material is then transformed from wollastonite into TiO{sub 2}/silica composites.« less