Reprint of: Electrochemical oxidation of stabilized landfill leachate on DSA electrodes

Abstract

The electrochemical oxidation of stabilized landfill leachate with 2960mgL−1 chemical oxygen demand (COD) over a Ti/IrO2–RuO2 anode was investigated in the presence of HClO4 as the supporting electrolyte. Emphasis was given on the effect of electrolysis time (up to 240min) and temperature (30, 60 and 80°C), current density (8, 16 and 32mAcm−2), initial effluent's pH (0.25, 3, 5 and 6), HClO4 concentration (0.25 and 1M) and the addition of NaCl (20 and 100mM) or Na2SO4 (20mM) as source of extra electrogenerated oxidants on performance; the latter was evaluated regarding COD, total carbon (TC), total phenols (TPh) and color removal. Moreover, the anode was studied by scanning electron microscopy and cyclic voltammetry. The main parameters affecting the process were the effluent's pH and the addition of salts. Treatment for 240min at 32mAcm−2 current density, 80°C and the pH adjusted from its inherent value of 0.25 (i.e. after the addition of HClO4) to 3 yielded 90% COD, 65% TC and complete color and TPh removal at an electricity consumption of 35kWhkg−1 COD removed. Comparable performance (i.e. 75% COD reduction) could be achieved without pH adjustment but with the addition of 100mM NaCl consuming 20kWhkg−1 COD removed.