Electrochemical Degradation of Anthraquinone Dye Alizarin Red: Role of the Electrode Material

Abstract

Anodic oxidation is a promising process for degrading toxic and biologically refractory organic pollutants present in wastewater. Proper selection of electrodes is the key to reach effective and economic treatment. In this study, the electrochemical oxidation of Alizarin Red has been studied in neutral media using lead dioxide (PbO2), boron-doped diamond (BDD) and platinum (Pt) anodes in bulk electrolysis experiments under same conditions. Obtained results have clearly shown that the electrode material is an important parameter for the optimization of such process. Kinetics analysis showed that Alizarin Red is readily oxidized on PbO2 and BDD anodes, Pt anode having a moderate ability to oxidize it. Different current efficiencies were obtained for PbO2 and BDD, depending on the applied current density in the range from 33 to 150 mA cm-2. The effect of the initial Alizarin Red concentration on the performance of PbO2, BDD and Pt anodes, as well as, their comparative oxidation ability was studied. Faster Alizarin Red elimination and TOC removal were obtained using BDD anode with current density of 33 mA cm-2. Bulk electrolysis showed that the complete TOC and color removal were achieved using PbO2 and BDD anodes while Pt anode performed only a partial oxidation of Alizarin Red. Keywords: Alizarin, Degradation kinetics, Anodic oxidation, BDD anode, Hydroxyl radical, TOC removal, triphenyl methyl, physico-chemical, discoloration, microbiological degradation