Comparative study on the treatment of refractory organics in landfill leachate by homogeneous and heterogeneous Fenton advanced oxidation processes

Abstract

With the advancement of the landfill stabilization process of municipal solid waste, landfill leachate containing a large amount of refractory organic matter is formed. In this study, homogeneous Fenton and heterogeneous Fenton-like (activation by zero valent iron (Fe⁰), pyrite (FeS₂) and magnetite (Fe₃O₄) as solid iron materials) processes have been compared for the removal of refractory organics from landfill leachate. The removal efficiency of organics in the Fenton process was slightly higher than those in the Fenton-like processes. The removal efficiencies based on total organic carbon, UV absorbance at 254 nm (UV₂₅₄) and colour number in the Fenton process were as high as 57.42%, 71.63% and 81.03%, respectively. In the Fenton-like processes, the Fe⁰/H₂O₂ process achieved 35.74%, 66.24% and 86.29% removal efficiencies, respectively. Moreover, the degradation effect on refractory organic substances proved to be better. In the Fenton-like processes, the activation mechanisms with Fe⁰ and FeS₂ involve the homogeneous activation of Fe²⁺ in solution and heterogeneous activation of iron oxides produced during the reaction, respectively. With Fe₃O₄, the activation mechanism is mainly a heterogeneous process involving its intrinsic iron oxide constituents. This study may provide a theoretical basis for the treatment of refractory organics in landfill leachate.