Electrochemical degradation of sulfonated amines on SI/BDD electrodes

The electrochemical oxidation of aniline (AN) and ortanilic (OA), metanilic (MA) and sulfanilic (SA) acids was performed using as anode a boron-doped diamond (BDD) electrode. Tests were performed with model solutions of the different amines, with concentrations of 200 mg L−1, using as electrolyte 0.035 M Na2SO4, in a batch cell, with re-circulation, at different current densities (200 and 300 A m−2). Samples were collected at pre-selected intervals and absorbance measurements, Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), Total Kjeldahl Nitrogen, Ammonia Nitrogen, Nitrates and Nitrites and HPLC analysis were performed. Results have shown a good elimination of the persistent pollutant, with COD and TOC removals always higher than, respectively: AN – 91% and 90%; OA – 75% and 82%; MA – 88% and 87%; and SA – 85% and 79%. The combustion efficiencies, calculated for the first hour of the runs, for the 300 A m−2 assays, were the following: AN – 0.93; OA – 0.28; MA – 0.82; and SA – 0.83. For all the amines studied, after 6 h degradation only oxalic and maleic acids were identified by HPLC.