Removal of 2,4-dichlorophenol as herbicide's by-product by Fenton's reagent combined with an electrochemical system

2,4-dichlorophenol(2,4-DCP), which is known as a by-product from herbicide utilization, is a priority toxic organic pollutant listed by U.S. EPA. The application of electrochemical system combined with Fenton process has been investigated here in order to know the feasibility of continuous electro-regeneration of ferrous ion for enhancement of 2,4-DCP degradation in the Fenton's reagent solution. The operating parameters such as pH, current density, H2O2 to Fe2+ (H/F) mole ratio and H2O2 feeding mode of operation were also investigated to determine the optimum operating condition. From the experimental data, it was found that current density of 0.05 mA/cm(2) with the H2O2 to Fe2+ (H/F) mole ratio at 30 and operating pH of 3 could completely remove 1 mM 2,4-DCP up to 70%. Improvement in efficiency and stability of process could be achieved by modification of H2O2 feeding mode from one-time initial feeding mode to the step feeding mode of operation that could reduce toxicity possibility and mineralization rather than only one-time initial feeding. Additionally initial degradation rate was investigated by the first-order model for using in the process optimization indicator. HPLC and IC data were applied to identify the intermediates occurred among the reaction. For this experiment, 2-chlorophenol, phenol, hydroquinone, p-benzoquinone, maleic, acetic, oxalic, and formic acids were found as the main oxidation intermediates. Moreover, a degradation pathway for 2,4-DCP oxidation was proposed on the basis of intermediate compounds that were detected.