Electrochemical Oxidation of Landfill Leachate after Biological Treatment by Electro-Fenton System with Corroding Electrode of Iron.

Abstract

Electrochemical oxidation of landfill leachate after biological treatment by a novel electrochemical system, which was constructed by introducing a corroding electrode of iron (Fec) between a boron-doped diamond (BDD) anode and carbon felt (CF) cathode (named as BDD–Fec–CF), was investigated in the present study. Response surface methodology (RSM) with Box–Behnken (BBD) statistical experiment design was applied to optimize the experimental conditions. Effects of variables including current density, electrolytic time and pH on chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) removal efficiency were analyzed. Results showed that electrolytic time was more important than current density and pH for both COD and NH3-N degradation. Based on analysis of variance (ANOVA) under the optimum conditions (current density of 25 mA·cm−2, electrolytic time of 9 h and pH of 11), the removal efficiencies for COD and NH3-N were 81.3% and 99.8%, respectively. In the BDD–Fec–CF system, organic pollutants were oxidized by electrochemical and Fenton oxidation under acidic conditions. Under alkaline conditions, coagulation by Fe(OH)3 and oxidation by Fe(VI) have great contribution on organic compounds degradation. What is more, species of organic compounds before and after electrochemical treatment were analyzed by GC–MS, with 56 kinds components detected before treatment and only 16 kinds left after treatment. These results demonstrated that electrochemical oxidation by the BDD–Fec–CF system has great potential for the advanced treatment of landfill leachate.