Solar photocatalytic decolourization of Crystal violet using supported TiO2: effect of some parameters and comparative efficiency

The present study focuses on the decolourization of crystal violet (CV) using TiO2 supported on glass slides under natural sunlight (sunny days, June 2013). The commercial Degussa P25 TiO2 was used as a photocatalyst in this study. The P25 TiO2 deposition process was achieved using acetone as precursor. The effect of some process parameters (CV concentration, number of TiO2 glass slides, pH and presence of metallic cations as interfering ions such as Cu2+, Fe2+, Fe3+, Mn2+ and Zn2+) was investigated. It was found that the decolourization process follows a pseudo-first order with respect to the substrate concentration. The pH had a net effect on the decolourization process. The apparent rate constants increased proportionally to the number of TiO2 glass slides. The results show that the presence of Fe2+, Mn2+ and Cu2+ cations with CV decreases the decolourization rate by varying degrees (22.1-35.3%) while Zn2+ has a negligible effect. However, the presence of Fe3+ led to an acceleration of the CV decolourization. The P25 TiO2-supported can be reused several times under the present working conditions. Finally, the photoactivity efficiency of P25 TiO2-supported was compared to that of P25 TiO2-dispersed under artificial UV (single lamp, 300-400 nm) and natural sunlight. Under the present experimental conditions, a complete decolourization was achieved less than 6 h of solar irradiation at natural pH and using two TiO2 glass slides.