Sol–gel preparation and characterization of alkaline earth metal doped nano TiO 2: Efficient photocatalytic degradation of 4-chlorophenol

Abstract

Magnesium and barium doped TiO 2 nanoparticles were synthesized by sol–gel method. The materials were characterized by XRD, BET, FT-IR, TGA, UV–vis, SEM and TEM techniques. The pure TiO 2 nanoparticles contained both anatase and rutile phases together, but Mg 2+ or Ba 2+ metal ion doped nano TiO 2 gave only anatase phase. The framework substitution of Mg 2+ in nano TiO 2 was established by XRD and FT-IR techniques. However, Ba 2+ was retained only on the surface of nano TiO 2 as BaCO 3 and the absence of framework substitution of Ba 2+ in nano TiO 2 was evident from XRD and FT-IR analysis . The band gap values of Mg 2+ and Ba 2+ doped nano TiO 2 were higher than the pure nano TiO 2. The presence of anatase type structure in nano TiO 2 with high crystallinity and high phase stability even after annealing at 800 °C substantially indicates that the dopants might inhibit densification and crystallite growth in nano TiO 2 by providing dissimilar boundaries. The photocatalytic activity in the degradation of 4-chlorophenol was found to be higher for Mg 2+ and Ba 2+ doped nano TiO 2 than both pure nano TiO 2 and commercial TiO 2 (Degussa P-25). The influence of various parameters such as initial concentration of 4-chlorophenol, catalyst loading, pH and light intensity were optimized to obtain maximum degradation.