Comparison among some advanced oxidation processes in the degradation kinetics of the crude tannery effluent

In this work it was investigated the degradation kinetics of the crude tannery wastewater, collected in the homogenized reservoir with a chemical oxygen demand of 3340 mg L-1 at pH 8.1, through the advanced oxidation processes as photocatalysis mediated by semiconductor, photolysis in presence of hydrogen peroxide and photo-Fenton process at 30 oC. The experiments were performed using a 1:50 proportion in distilled water inside the double wall cylindrical reactor opened to the atmospheric air by varying the oxidant concentration. The degradation rate constants, kobs, determined under pseudo-first order conditions in pH ca. 7.3 and 30 oC, were higher for the photocatalytic process mediated by ZnO (kobs= 1.23x10-1 to 2.74x10-1 min-1) followed by TiO2 (0.90x10-2 min-1 to 3.35x10-2 min-1). As to for the rate constants under photolysis in presence of H2O2 (9.36x10-3 to 7.44x10-3 min-1) at pH ca. 6.8 as well as in photo-Fenton (7.30x10-3 to 12.0x10-3 min-1) at pH 5.8 was significantly lower than photocatalysis at 30°C. The chemical oxygen demand of the wastewater was completely removed after 2 h on photocatalytic process at 30 °C.