Photo-assisted electroperoxone of 2,4-dichlorophenoxy acetic acid herbicide: Kinetic, synergistic and optimization by response surface methodology

Abstract

In this study, the potential of UV-assisted electroperoxone process (UV-EPP) was assessed into oxidative degradation of 2,4-Dichlorophenoxy acetic (2,4-D) herbicide in a batch system. The influence of several experimental factors like pH of aqueous media, applied current, ozone concentration, reaction time and initial 2,4-D concentration on the UV-EPP performance was evaluated using response surface methodology (RSM). Coupling of UV with ozonation and electrolysis showed the better performance into 2,4-D removal compared to their implementation in individual and binary systems. The process possesses a good efficiency in a wide range of solution pH. Under optimal conditions (pH 5.6, 1.8 mg/L. min ozone, 0.9 A applied current and 112 min reaction), over 91% removal of 58 mg/L 2,4-D was achieved. In addition, the complete removal of 2,4-D and 85% COD and 76% TOC were obtained by UV-EPP over 160 min reaction. Trapping tests verified the presence of both O2− and HO species in the degradation of 2,4-D during UV-EPP, while superoxide radicals have contributed as dominant species. The obtained results were fitted to pseudo-first-order kinetic model with a high correlation coefficient. In conclusion, UV-EPP integrated system can be utilized as an effective advanced oxidation process into excellent degradation/mineralization of herbicides and refractory or toxic organic compounds.