Comparative Study on the Catalytic Ozonation of Biotreated Landfill Leachate Using γ-Al2O3-Based Catalysts Loaded with Different Metals

Abstract

Global municipal solid waste (~2B tons/year) affects sustainability, as landfill and incineration face persistent leachate contamination, demanding effective management to advance water recycling and circular economies. Accelerated investigation of hybrid biocatalytic ozonation systems is imperative to enhance contaminant removal efficiency for stringent discharge compliance. This study investigates the catalytic ozonation effects of γ-Al2O3-based catalysts loaded with different metals (Cu, Mn, Zn, Y, Ce, Fe, Mg) on the biochemical effluent of landfill leachate. The catalysts were synthesized via a mixed method and subsequently characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Pseudo-second-order kinetics revealed active metal loading’s impact on adsorption capacity, with Cu/γ-Al2O3 and Mg/γ-Al2O3 achieving the highest Qe (0.85). To elucidate differential degradation performance among the catalysts, the ozone/oxygen gas mixture was introduced at a controlled flow rate. Experimental results demonstrate that the Cu/γ-Al2O3 catalyst, exhibiting optimal comprehensive degradation performance, achieved COD and TOC removal efficiencies of 84.5% and 70.9%, respectively. UV–vis absorbance ratios revealed the following catalytic disparities: Mg/γ-Al2O3 achieved the highest aromatic compound removal efficiency; Ce/γ-Al2O3 excelled in macromolecular organics degradation. EEM-PARAFAC analysis revealed differential fluorophore removal: Cu/γ-Al2O3 exhibited broad efficacy across all five components, while Mg/γ-Al2O3 demonstrated optimal removal of C2 and C4, but showed limited efficacy toward C5. These findings provide important insights into selecting catalysts in practical engineering applications for landfill leachate treatment. This study aims to elucidate catalyst formulation-dependent degradation disparities, guiding water quality-specific catalyst selection to ultimately enhance catalytic ozonation efficiency.