Granular activated carbon supported iron as a heterogeneous persulfate catalyst for the pretreatment of mature landfill leachate

Abstract

In this study, Fe(II)-loaded granular activated carbon (GAC) was used as a heterogeneous persulfate catalyst for the pretreatment of mature landfill leachate. The effects of Fe²⁺ dosage, persulfate concentration and initial pH on the degradation of the organic pollutants in the landfill leachate were investigated. In single factor experiments, the maximum Chemical Oxygen Demand (COD) removal rate reached 66.8, 66.2 and 76.3% at an Fe²⁺ dosage of 127 mg L⁻¹ (Fe²⁺/S₂O₈²⁻ = 254 mg mol⁻¹), a persulfate concentration of 0.5 mol L⁻¹ (i.e. S₂O₈²⁻ : 12COD₀ = 1.08) and an initial pH of 3, respectively. Obviously, pH played a more important role in the persulfate oxidation treatment than the other two factors. The synthetic experimental results showed that the COD removal rate exceeded 87.8% when the reaction conditions had a controlled Fe²⁺ dosage of 127 mg L⁻¹, persulfate concentration of 0.5 mol L⁻¹ and initial pH of 3.0, simultaneously. The recycle experiments displayed that the catalytic ability of reused Fe(II)-GAC declined considerably and the COD removal rate dropped by approximately half after reusing three times. But the catalytic ability of the catalyst used could be well recovered after regeneration at 550 °C in a N₂ atmosphere. Finally, fluorescence excitation–emission matrix (EEM) spectroscopy preliminarily explained the degradation mechanism of the landfill leachate.