The photocatalytic degradation kinetics of food dye in aqueous solution under UV/ZnO system

This study investigated the photocatalytic degradation of two food dyes (E127 and E132) widely used in the pharmaceutical industry upon UV-C irradiation using ZnO nano crystallite as catalyst to assist the photocatalysis process. The dye elimination is performed by the spectral method and ADMI. Results showed that for UV-ZnO process, degradation yield not exceeding 76% for E127 and E132 after 4 h of irradiation for an initial dye of concentration 52.53 mg/L for E127 and 60 mg/L for E132 was obtained. While with UV-ZnO-H2O2, a quasi-complete degradation of E132 was obtained after 10 min and for E127 maximum efficiency of 72% was obtained after 60 min of irradiation. Substantial reduction of COD, besides removal of food dye, was also achieved. Kinetic studies revealed that the UV-ZnO-H2O2 degradation process fitted well the Langmuir–Hinshelwood model with correlation coefficient R2 equal to 0.980 and 0.962 for E127 and E132, respectively, for initial dye concentration of 52.53 mg/L for E127 and 60 mg/L for E132 mg/L under experimental conditions.