Photocatalytic Degradation of Eriochrome Black T Dye by ZnO Nanoparticles Using Multivariate Factorial, Kinetics and Isotherm Models

In current study the photocatalyst ZnO was prepared by complexation of zinc acetate with sodium diethyl dithiocarbamate trihydrate, and calcined at 750 °C. The ZnO nanoparticles were characterized by DLS, Zeta potential, SEM, EDX and FTIR. The ZnO nanoparticles (NPs) were applied for photocatalytic degradation of Eriochrome black-T (EBT) dye by UV, visible and mercury light irradiation sources. The experimental conditions were optimized by univariate and multivariate techniques, and it was revealed that degradation of dye by ZnO NPs surface was dependent on source of light and pH of dye solution. The degradation of EBT dye at pH 11 showed highest degradation rate 99.64% with UV light. The ZnO was calcined at 450, 600, 750 and 900 °C, but the calcination temperature 750 °C showed better degradation rate for EBT. The highest degradation was found at 15 mg dose and 5 ppm concentration. The effects of Na + , Ca 2+ , K + , Mg 2+ on the degradation, were studied and these salts had no effect on degradation rate. The degradation obeyed pseudo second order kinetics model as compared to pseudo first and zero order models and Langmuir isotherm model fitted more as compare to other models. The effects of variables were examined by factorial design of 18 experiments by cantered Draper-Lin small composite model. The degradation of EBT dye in real samples collected from River Indus, tape water and domestic wastewater and spiked with 20 μg/mL, indicated that the dye degraded upto 82–86% with relative standard deviations (RSD) within 2% (n = 3).