Heterogeneous photocatalytic degradation of mordant black 11 with ZnO nanoparticles under UV-Vis light

The photocatalytic degradation of mordant black 11, an azo dye, under UV-Vis light, was investigated using a type of commercial nanosized zinc oxide (ZnO) as photocatalyst in aqueous solutions. Nanosized ZnO was characterized by different methods, including UV-Vis diffuse reflectance spectrum (UV-vis DRS), X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), etc. The effects of influential experimental parameters on decolorization rate, including catalyst dosage, initial dye concentration, initial pH value, irradiation intensity, etc., were studied in detail. It was found that after 60-min irradiation, the decolorization rate was only 58.4% at pH 2, but above 98% at natural (pH ∼ 4.27) and alkaline conditions. Mordant black 11 could be nearly 100% decolorized after 60 min irradiation by UV-Vis light at natural/alkaline pH and 0.3 g/L dosage. It was found that alkaline pH increased the decolorization rate; an increase in irradiation intensity of UV-Vis light enhanced the rate of degradation of the dye solution significantly at low dosage, while little influence as 0.3 g/L dosage.