Performance investigation of electrochemical assisted HClO/Fe 2+ process for the treatment of landfill leachate.

The feasibility of removal of chemical oxygen demand (COD) and ammonia nitrogen (NH 4 + -N) from landfill leachate by an electrochemical assisted HClO/Fe 2+ process is demonstrated for the first time. The performance of active chlorine generation at the anode was evaluated in Na 2 SO 4 /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 (Fe IV O 2+ ) in the HClO/Fe 2+ system. The influence of initial pH, Fe 2+ concentration, and applied current density on COD and NH 4 + -N abatement was elaborately investigated. The optimum pH was found to be 3.0, and the proper increase in Fe 2+ dosage and current density resulted in higher COD removal due to the accelerated accumulation of • OH and Fe IV O 2+ in the bulk liquid phase, whereas, the NH 4 + -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 Fe 2+ concentration. The reaction mechanism of electrochemical assisted HClO/Fe 2+ treatment of landfill leachate was finally proposed. The powerful • OH and Fe IV O 2+ , in concomitance with active chlorine and M( • OH), were responsible for COD abatement, and active chlorine played a key role in NH 4 + -N oxidation. The proposed electrochemical assisted HClO/Fe 2+ process is a promising alternative for the treatment of refractory landfill leachate.