Electrochemical/peroxydisulfate/Fe3+ treatment of landfill leachate nanofiltration concentrate after ultrafiltration

Landfill leachate nanofiltration concentrate after ultrafiltration was treated. The experiments were carried out in an electrolytic cell which had an anode chamber and a cathode chamber and could be separated by a proton exchange membrane. Different electrochemical processes combined with peroxydisulfate/Fe3+ (PS/Fe3+) were compared and the reactions in anode chamber and cathode chamber were discussed. The Anode/PS/Fe3+-Cathode/PS/Fe3+ process shows the best effect on COD removal and color removal. The 3D-EEMFS results indicate that Anode/PS/Fe3+-Cathode/PS/Fe3+ process has the best effect on the destruction of organics. In anode chamber, the total COD removal is ascribed to (1) the oxidation by SO4 %-produced from PS activation by original metal ions in the target solution, (2) direct and indirect oxidations by anode, and (3) coagulation caused by Fe3+ after pH adjustment. In cathode chamber, the total COD removal is due to (1) the oxidation by SO4 %produced from PS activation by the regenerated Fe2+ from Fe3+ reduction on cathode, and (2) coagulation caused by Fe3+ after pH adjustment. An optimal experimental condition with current of 80 mA, Fe3+ dosage of 15mM and PS dosage of 37.5mM is obtained for Anode/PS/Fe3+-Cathode/PS/Fe3+ process. The energy consumption between Anode/PS/Fe3+-Cathode/PS/Fe3+ (4.42 kWh/kgCOD) and (Anode+ Cathode)/PS/Fe3+ (4.57 kWh/kgCOD) is similar when 55% of COD is removed. However, the toxicity increase in Anode/PS/Fe3+-Cathode/PS/Fe3+ process is obviously less than that in (Anode+ Cathode)/PS/Fe3+ process.