Electrochemical degradation of aromatic amines on BDD electrodes

The electrochemical oxidation of four aromatic amines, with different substituent groups, 3-amino-4-hydroxy-5-nitrobenzenesulfonic acid (Al), 5-amino-2-methoxybenzenesulfonic acid (A2), 2,4-dihydroxyaniline hydrochloride (A3) and benzene-1,4-diamine (A4), was performed using as anode a boron-doped diamond electrode, commercially available at Adamant Technologies. Tests were run at room temperature with model solutions of the different amines, with concentrations of 200 ppm, using as electrolyte 0.035 M Na2SO4 aqueous solutions, in a batch cell with recirculation, at different current densities (200 and 300A m(-2)). The following analyses were performed with the samples collected during the assays: UV-Vis spectrophotometry, chemical oxygen demand (COD), total organic carbon (TOC), total Kjeldahl nitrogen, ammonia nitrogen, nitrates and HPLC. Results have shown a good electrodegradation of all the amines tested, with COD removals, after 6 h assays, higher than 90% and TOC removals between 60 and 80%. Combustion efficiency (eta(C)), which measures the tendency to convert organic carbon to CO2, was also determined for all the amines, being eta(CA1) < eta(CA2) < eta(CA3) < eta(CA4) = 0.99. (C) 2010 Elsevier B.V. All rights reserved.