Electro-Fenton treatment of mature landfill leachate in a continuous flow reactor

Highlights: ► CSTR mode was used for COD removal of landfill leachate by Fered-Fenton process. ► The complete mixing condition in the CSTR was verified. ► A modified pseudo-first order kinetic model was developed. ► The effects of important parameters on COD removal were investigated. ► The organic components before and after treatment were determined by GC–MS. - Abstract: The treatment of mature landfill leachate by EF-Fere (also called Fered-Fenton) method was carried out in a continuous stirred tank reactor (CSTR) using Ti/RuO2–IrO2–SnO2–TiO2 mesh anodes and Ti mesh cathodes. The effects of important parameters, including initial pH, inter-electrode gap, H2O2 to Fe2+ molar ratio, H2O2 dosage and hydraulic retention time, on COD removal were investigated. The results showed that the complete mixing condition was fulfilled in the electrochemical reactor employed in this study and COD removal followed a modified pseudo-first order kinetic model. The COD removal efficiency increased with the decrease of H2O2 to Fe2+ molar ratio and hydraulic retention time. There existed an optimal inter-electrode gap or H2O2 dosage so that the highest COD removal was achieved. Nearly the same COD removal was obtained at initial pH 3 and 5, but the steady state was quickly achieved at initial pH 3. The organic pollutants in the leachate were analyzed through a gas chromatography coupled with mass spectrometry (GC–MS) system. About 73 organics were detected in the leachate, and 52 of which were completely removed after EF-Fere process.