Ultraviolet-enhanced Fe0-activated H2O2 process for the removal of refractory organic matter from landfill leachate: Performance and mechanism

The Fenton-like process, utilizing zero-valent iron (Fe 0 ) and hydrogen peroxide (H 2 O 2 ), is employed to degrade refractory organic matter in membrane bioreactor (MBR) effluent derived from landfill leachate. However, the rate-limiting Fe 2+ /Fe 3+ redox step diminishes treatment efficacy and generates substantial iron sludge. This study elucidates the mechanism by which ultraviolet (UV) irradiation augments the Fe 0 /H 2 O 2 process for the removal of refractory organic matter in MBR effluent. The results show that the UV- enhanced H 2 O 2 process effectively disrupts the aromatic structure of organic compounds, reducing molecular weight, degree of polymerization, and humification. Compared with the Fe 0 /H 2 O 2 process, the removal efficiency of UV 254 , color number, and total organic carbon in the effluent treated by the UV/Fe 0 /H 2 O 2 process increased by 24.16%, 14.62%, and 57.46%, respectively. Concurrently, the generation of iron sludge was reduced by 21.6%. This enhancement is primarily attributed to UV's ability to intensify the Fe 2+ /Fe 3+ redox cycle and expedite the surface corrosion of Fe 0 , yielding more iron oxides. This accelerates the decomposition of H 2 O 2 , generating a higher quantity of • OH through both homogeneous and heterogeneous Fenton-like reactions. The refractory organic matter is removed through the oxidation by • OH, as well as the adsorption and precipitation facilitated by iron-based colloids. Practitioner Points UV promotes Fe 0 /H 2 O 2 process to degrade refractory organic matter in MBR effluent. UV promotes Fe 0 to dissolve more Fe 2+ and the redox cycle of Fe 2+ and Fe 3+ . The dosage of H 2 O 2 or Fe 0 influences the treatment effect of the process. Graphical UV can enhance the degradation of refractory organic matter in MBR effluent from landfill leachate by Fe 0 /H 2 O 2 process.