Investigation of UV/H2O2 process for removal of ortho-toluidine from industrial wastewater by response surface methodology based on the central composite design

In this project, degradation and mineralization of ortho-toluidine (OT) were investigated by UV/H2O2 process in a batch recirculating photo reactor. The full factorial design and response surface methodology were applied for evaluating the effects of experimental variables such as amount of H2O2, initial concentration of pollutant and pH on the removal of the OT and chemical oxygen demand (COD). Analysis of variance (ANOVA) showed a high determination coefficient value (R-2 = 0.9291, R-adj(2) = 0.9122 for removal of OT and R-2 = 0.9751, R-adj(2) = 0.9677 for removal of COD) and satisfactory prediction second- order regression model. The results showed a good agreement with the experimental values. The graphical counter plots and response surface were employed to determine the optimum conditions. Based on the optimum results, maximum efficiency for removal of the OT was achieved in initial pH of 10, dosage of H2O2 at 30 mM and initial concentration of the OT at 40 mg l(-1). According to the kinetic study, the pseudo-first-order rate constant (k = 4.95 x 10(-2) min(-1)) was obtained for the removal of the OT. The degradation and mineralization of the OT were estimated by HPLC and COD tests, respectively.