2.5. Evaluation of photocatalytic activity of the samples
Photocatalytic activities of the all samples were evaluated by
decomposition of MO (6 mg/L, pH 2) aqueous solution under visible
and sun light irradiation. MO was used as a model compound,
because it was possible to use UV–Vis spectroscopy to monitor the
degradation under various conditions such as MO concentration,
pH, TiO2 concentration and solar intensity [34]. The OH free radical
attacked the azo bond in the MO molecule first and then broke the
N N bond down. MO degraded to smaller molecules and finally,
these molecules are oxidized to nontoxic CO2 and H2O [35].