Exploring the applicability of a combined electrodialysis/electro-oxidation cell for the degradation of 2,4-dichlorophenoxyacetic acid

Abstract

The improvement in the treatment efficiency of diluted effluents is one of the great challenges faced by electrochemical technology nowadays. In the present work, it is aimed to develop an electrochemical cell for the simultaneous concentration and degradation of ionic organic pollutants. This combined cell (so called EDEO device) integrates the concentration of the organic by electrodialysis (ED) with its electro-oxidation (EO). For the particular case of the 2,4-dichlorophenoxyacetic acid (2,4-D), the performance of the cell has been tested with two anode materials (boron-doped diamond, BDD and mixed mineral oxides, MMO) and with two supporting electrolytes in order to explore four combinations that are expected to cover a wide range of possible actual scenarios. Results demonstrate that the combined EDEO process exhibits a degradation rate and a mineralization current efficiency markedly higher than the equivalent EO device when working with MMO anodes, either with NaCl or with Na2SO4. It was checked that the use of a BDD anode clearly increases the efficiency and the rate of the treatment due to the formation of strong oxidants. In this case, the effect of working with the combined EDEO in the rate of 2,4-D degradation is negligible because the 2,4-D transport rate becomes comparable to the degradation rate, being the combined process unable to generate a concentration greater than that accounted in the single EO device.