Optimization of Suspended Photocatalytic Treatment of Two Biologically Treated Textile Effluents Using TiO2 and ZnO Catalysts

In this study, the photocatalytic degradation of two biologically treated textile finishing wastewater was investigated using powdered TiO₂ and ZnO catalysts with UV-A lamp irradiation. Photodegradation and photodecolorization of the samples real textile industrial wastewater is observed directly proportional to pH and catalyst concentrations. Optimum catalyst concentration was found as 2 g l^-1 in both catalysts. COD removal in TiO₂ assisted system was obtained two fold higher than ZnO assisted system depending characteristics of the wastewater samples. Optimum pH values were determined to be 5 and 9 for TiO₂ and ZnO assisted systems respectively. A COD removal of 45% and 23% were obtained using and ZnO catalysts respectively during 3 h irradiation. The effluents of photocatalytic treated samples using both catalysts displayed no acute toxicity at the end of 3 h irradiation time at optimum experimental conditions.  Results, in conclusion, revealed that both TiO₂ and ZnO catalysts were found to be very effective in color removal and provided safe and proper effluents to meet discharge limits, even reuse guideline values.