Electrochemical oxidation of herbicide bifenox acid in aqueous medium using diamond thin film electrode

Abstract

The electrochemical oxidation of bifenox acid was studied at a boron-doped diamond thin film by cyclic voltammetry and galvanostatic electrolysis. The course of the electrolysis was monitored by measurement of chemical oxygen demand (COD) and by gas chromatography/mass spectrometry (GC / MS) analysis. It was found that exhaustive electrolysis leads to degradation and, ultimately, to mineralization of the starting herbicide. The degradation intermediates were identified showing that the oxidation process begins with the fragmentation of the molecule followed by reactions involving the hydroxyl radical, which is generated by the discharge of water. The study of the effect of current density and concentration showed that the degradation efficiency increases with decreasing current densities and increasing concentrations. The whole results were interpreted in a mechanistic scheme involving two oxidation pathways, the first is a direct oxidation at the electrode and the second uses hydroxyl radical as mediator of the oxidation. Finally, a kinetic study based on spectrophotometric measurements showed that the degradation process is pseudo first order.

Keywords:

• Bifenox acid
• boron-doped-diamond
• degradation
• electron transfer
• herbicide
• mineralization

Acknowledgments

This work has been achieved with the financial support of the Ministère de l’Enseignemnt Supérieur et de la Recherche Scientifique (Tunisia). The authors thank Dr. N. Ben Salah (Faculté des Sciences de Gabès, Tunisie) for technical cooperation.