Porous TiO2 with a controllable bimodal pore size distribution from natural ilmenite

Abstract

Ilmenite (FeTiO3) is an inexpensive abundant natural mineral and it would be a perfect precursor for the production of porous TiO2 if a suitable synthesis method was developed. A new method combining a series of processing steps of ball milling, high-temperature annealing, selective chemical leaching and final calcining in air is proposed in this paper. The resulting TiO2 is a porous material with a bimodal pore structure. The pore size distribution has two clear maxima corresponding to small mesopores (2?30 nm) and large meso- and macropores (centered at around 50?80 nm). It was found that the duration of the annealing step could alter the contribution of each type of pores. A short annealing time (0.5 h) lead to the preferential formation of pores within 2?30 nm while pores centered at 50?80 nm dominated the pore size distribution after a relatively long annealing (1.5 h). The obtained porous rutile TiO2 shows a better photocatalytic activity than that of a commercial rutile TiO2 powder.