Electrochemical oxidation of stabilized landfill leachate on DSA electrodes

摘要

The electrochemical oxidation of stabilized landfill leachate with 2960 mgL~(-1) chemical oxygen demand (COD) over a Ti/IrO_2-RuO_2 anode was investigated in the presence of HClO_4 as the supporting electrolyte. Emphasis was given on the effect of electrolysis time (up to 240 min) and temperature (30, 60 and 80℃), current density (8,16 and 32mAcm~(-2)), initial effluent's pH (0.25,3,5 and 6), HClO_4 concentration (0.25 and 1 M) and the addition of NaCl (20 and l00mM) or Na_2SO_4 (20 mM) 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 240 min at 32mAcm~(-2) current density, 80 ℃ and the pH adjusted from its inherent value of 0.25 (i.e. after the addition of HC1O_4) to 3 yielded 90% COD, 65% TC and complete color and TPh removal at an electricity consumption of 35 kWh kg~(-1) COD removed. Comparable performance (i.e. 75% COD reduction) could be achieved without pH adjustment but with the addition of 100 mM NaCl consuming 20 kWh kg~(-1) COD removed.