Azo dye degradation kinetics in TiO2 film-coated photoreactor

In this study, commercial nano-size TiO2 suspension was used to coat on the inner surface of glass reactors and the immobilized TiO2 film served as photocatalyst to decompose azo dye in aqueous solutions. A full factorial design approach using three factors, namely rotation time, rotation speed, and drying temperature was adopted to prepare TiO2-coated reactors. The azo dye decomposition conversion under 8 W UV illumination for 4 h was measured as the response of the experimental design. The results showed that the three main effects were significant: increasing the rotation time from 10 to 50 min leaded to 11.4% increase in the dye conversion; increasing the rotation speed from 10 to 50 rpm leaded to 5.6% increase in the dye conversion; increasing the drying temperature from 150 to 250 °C leaded to 2.8% increase in the dye conversion. A series of dye degradation experiments with varying initial dye concentrations were conducted using the TiO2-coated reactor. The dye degradation rate was found to be −rdye = kaC/(1 + kbC) with k = 0.0326 min−1 and kb = 0.764 L mg−1. The developed kinetic model was used to fit the experimental data satisfactorily.