LAUSR

The feasibility of removal of chemical oxygen demand (COD) and ammonia nitrogen (NH4+–N) from landfill leachate by an electrochemical assisted HClO/Fe2+ process is demonstrated for the first time. The performance of active chlorine generation at the anode was evaluated in Na2SO4/NaCl media, and a higher amount of active chlorine was produced at greater chloride concentration and higher current density. The probe experiments confirmed the coexistence of hydroxyl radical (•OH) and Fe(IV)-oxo complex (FeIVO2+) in the HClO/Fe2+ system. The influence of initial pH, Fe2+ concentration, and applied current density on COD and NH4+–N abatement was elaborately investigated. The optimum pH was found to be 3.0, and the proper increase in Fe2+ dosage and current density resulted in higher COD removal due to the accelerated accumulation of •OH and FeIVO2+ in the bulk liquid phase, whereas, the NH4+–N oxidation was significantly affected by the applied current density because of the effective active chlorine generation at higher current but was nearly independent of Fe2+ concentration. The reaction mechanism of electrochemical assisted HClO/Fe2+ treatment of landfill leachate was finally proposed. The powerful •OH and FeIVO2+, in concomitance with active chlorine and M(•OH), were responsible for COD abatement, and active chlorine played a key role in NH4+–N oxidation. The proposed electrochemical assisted HClO/Fe2+ process is a promising alternative for the treatment of refractory landfill leachate.