Degradation of mixtures of phenols using boron doped diamond electrodes for wastewater treatment

Abstract

A model is proposed for describing the electrochemical oxidation of multicomponent mixtures of organic compounds, when significant mineralization (i.e., combustion to CO 2) of the compounds occurs. This is known to be the case of the degradation of many organic compounds on boron doped diamond (BDD) and other new electrocatalytic materials used as anodes. The proposed model predicts the variation of concentrations of each component present in the mixture, chemical oxygen demand (COD) and current efficiency as a function of time, under different rate control regimes (diffusive, kinetic and mixed) at constant current. Mass transfer coefficients of each component of the mixture, needed for the application of the model, were obtained from single solute experiments. Tests were conducted in a conventional three-electrode cell, using a commercial BDD electrode as anode. Good agreement between predicted and experimental results was generally obtained, though some deviations had been observed when the highest concentrations of the solutes were used, with concentrations decreasing faster than predicted. These deviations were found for both single- and multi-component systems, and can be explained by the occurrence of side reactions or the accumulation of intermediate compounds of the combustion mechanism.