Performance investigation of electrochemical assisted HClO/Fe2+ process for the treatment of landfill leachate.

Zhihong Ye,Fei Miao,Hui Zhang

doi:10.1007/s11356-022-19174-2

Abstract

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.

Highlights

Sanitary landfill disposal is the most widely used method for municipal solid waste treatment in the world due to its economic advantages (Wu et al 2018)
To clarify the ability of Ti/IrO2-RuO2-TiO2 anode for the production of active chlorine, the variation of active chlorine content as function of electrolysis time in EO-HClO process was monitored at various levels of chloride ions concentration and different current densities
The effect of current density on active chlorine generation was further investigated at 4.0 g L 1 of Cl ion

Summary

Introduction

Sanitary landfill disposal is the most widely used method for municipal solid waste treatment in the world due to its economic advantages (Wu et al 2018). This disposal method leads to the production of complex liquids, namely landfill leachate, containing large amounts of organic pollutants, NH4+-N, inorganic salts and heavy metals (Fu et al 2021). The old landfill leachate (more than 10 years) usually has stable water quality indexes, such as high fraction of recalcitrant organics, high NH4+-N concentration (2000-5000 mg L-1) and low BOD/COD ratio (< 0.1), making it difficult to be treated using traditional biological technology (Deng et al 2021; Ghahrchi and Rezaee 2021). Many alternative physical and chemical methods have been applied for the treatment of landfill leachate, such as flocculation and sedimentation (Silva et al 2004), adsorption (Reshadi et al 2020), ozonation (Yang et al 2021), advanced oxidation processes (Kwarciak-Kozłowska and Fijałkowski 2021), membrane treatment (Keyikoglu et al 2021) and electrochemical technologies (Deng et al 2020)

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Results

Conclusion