Oxidation of carboxylic acids in water at IrO2-Ta2O5 and Boron Doped Diamond anodes

Abstract

The electrochemical oxidation of different carboxylic acids (namely, oxalic, formic and maleic) in water at boron doped diamond (BDD) and IrO2-Ta2O5 (DSA-O2) anodes was performed to study the influence of the operative parameters and of the nature of the acid on the performances of the process. Higher abatements were obtained at BDD with respect to DSA anodes for all the selected carboxylic compounds. The rate of abatement decreased in the order oxalic > formic >> maleic at iridium anodes while an opposite trend was observed at diamond anodes (formic  maleic > oxalic), thus indicating that different oxidant agents are involved at these two electrodes. Also the effect of the temperature depends on both the nature of the acid and of the anode. Higher current efficiencies were obtained when most part of the process was under the kinetic control of the oxidation reaction, i.e., when low current densities and high flow rates were imposed. High concentrations of carboxylic acids enhanced the current efficiency at all kinetic regimes.