Nitrogen and organic load removal from sanitary landfill leachates by anodic oxidation at Ti/Pt/PbO2, Ti/Pt/SnO2-Sb2O4 and Si/BDD

Ti/Pt/PbO2, Ti/Pt/SnO2-Sb2O4 and boron-doped diamond (BDD) anodes were used to study the influence of the anode material on nitrogen and organic load removal from a biologically pretreated leachate from an intermunicipal sanitary landfill: chemical oxygen demand (COD) - 6.2 g L-1 and ammonium nitrogen (AN) - 0.48 g L-1. The experimental results showed that for the three anode materials under study, the COD removals were similar despite the BDD anode more easily promoting the complete combustion of the organic matter. Regarding nitrogen removal, metal oxide anodes were effective in the removal of AN, whereas BDD was more efficient in the removal of organic nitrogen. For similar experimental conditions, Ti/Pt/PbO2 demonstrated the highest AN removal (90%), followed by Ti/Pt/SnO2-Sb2O4 (64%) and BDD (56%). Simulated samples with analogous nitrogen content but without organic matter were also electrolyzed to better understand the elimination of the different forms of nitrogen present in the samples. At BDD anodes, ammonium is oxidized to nitrate, maintaining the nitrogen content higher than in the samples treated with the metal oxides, whereas these latter materials are more effective in the complete elimination of nitrogen, due to partial oxidation to nitrogen gas, showing that BDD is more predisposed to promote complete combustion. The anodes of metallic oxides demonstrated lower energy consumption than BDD; the energetic behavior of Ti/Pt/PbO2 and Ti/Pt/SnO2-Sb2O4 was very similar. (C) 2013 Elsevier B.V. All rights reserved.