Preparation of porous TiO2/silica composites without any surfactants

TiO2-SiO2 composites, with high specific surface area (up to 308 m2/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 TiO2/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 N2 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: TiO2-SiO2 composites have been synthesized from wollastonite and titanium sulfate in the absence of any surfactants. In acid Ti(SO4)2 solution, Ca and Si ions in chain-like wollastonite could dissolve into the bulk solution and slightly soluble CaSO4 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 TiO2, silicate and CaSO4 particle deposited together and formed composites. Some cavities formed during the washing step through the dissolution of CaSO4 crystal phase. The bulk of the material is then transformed from wollastonite into TiO2/silica composites