Investigation of Photocatalytic Activity of Nano-Sized TiO2 with the Presence of Various Inorganic Anions

The effect of various anions on the photocatalytic activity of nano-sized TiO2 was investigated in a methyl orange solution. The photocatalytic activity of the TiO2 nanoparticles was significantly affected in the presence of SO42-, CO32-, NO3- and Cl-. Among the tested ions, Cl- was most effective anion in changing the photocatalytic activity. Addition of Cl- (0.05 M) decreased the methyl orange photodegradation rate to only one quarter of that when TiO2 was used alone. It was also demonstrated that the effects of these inions, on the rate of photocatalytic activity of the nanoparticles, were concentration dependent. There was a negative correlation between the concentrations of NO3- and Cl- and the methyl orange degradation rate by TiO2 However, at low concentrations, CO32- and SO42- enhanced the photocatalytic activity; while at the higher concentrations, these two anions inhibited the photocatalytic activity of TiO2