Photocatalytic degradation of methyl orange as a model compound

Abstract

Titanium dioxide (TiO 2) was used as a photocatalyst for the detoxification of water containing methyl orange (MO), which was used as a model compound. Solar radiation was used as an irradiation source. It was found that there was no degradation for the MO in the dark and in the presence of TiO 2. Also no degradation was observed for MO when the solution placed under solar radiation but without TiO 2. Several experiments were used to optimize the experimental parameters. In the first set of experiments variable amounts of TiO 2 were used with a fixed concentration of MO. It was found that 0.4% of TiO 2 gave the highest degradation rate constant, 0.619 h −1. In the second set of experiments TiO 2 concentration was fixed at 0.4% and the MO concentration was varied, the highest rate constants was obtained when the concentration of MO was 4×10 −5 M and it was found to be 0.639 h −1. The degradation became negligible in the presence of high concentrations of MO. The highest degradation rate was obtained at pH=3 with a rate constant κ=2.6683 h −1, followed by that at pH=9 where the calculated κ=0.7585 h −1.