Comparison of o-toluidine degradation by Fenton, electro-Fenton and photoelectro-Fenton processes

Abstract

A Box–Behnken design (BBD) statistical experimental design was used to investigate the degradation of o-toluidine by the electro-Fenton process. This method can be used to determine the optimal conditions in multivariable systems. Fe 2+ concentration (0.2–1.0 mM), H 2O 2 concentration (1–5 mM), pH (2–4), and current (1–4 A) were selected as independent variables. The removal efficiencies for o-toluidine and chemical oxygen demand (COD) were represented by the response function. Result by 2-level factorial design show that the pH and the Fe 2+ and H 2O 2 concentrations were the principal parameters. Among the main parameters, the removal efficiencies for o-toluidine and COD were significantly affected by pH and Fe 2+ concentration. From the Box–Behnken design predictions, the optimal conditions in the electro-Fenton process for removing 90.8% of o-toluidine and 40.9% of COD were found to be 1 mM of Fe 2+ and 4.85 mM of H 2O 2 at pH 2. Under these optimal conditions, the experimental data showed that the removal efficiencies for o-toluidine and COD in the electro-Fenton process and the photoelectro-Fenton process were more than 91% and 43%, respectively, after 60 min of reaction. The removal efficiencies for o-toluidine and COD in the Fenton process are 56% and 27%, respectively.