Performance investigation of electrochemical assisted HClO/Fe2+ process for the treatment of landfill leachate
2022
Ye, Zhihong | Miao, Fei | Zhang, Hui
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.
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