An assessment of the UV/nFe0 /H2 O2 system for the removal of refractory organics in the effluent produced by the biological treatment of landfill leachate.

Abstract

The removal efficiency and mechanism of the ultraviolet/nanoscale Fe0 /H2 O2 (UV/nFe0 /H2 O2 ) system for refractory organics in membrane bioreactor effluent were investigated. The most effective removal of organics was achieved at initial pH = 3.0, H2 O2 dosage = 50 mM, nFe0 dosage = 1.0 g/L, and UV power = 15 W, with a reaction time of 60 min. Under these conditions, the absorbance at 254 nm, chromaticity, and total organic carbon removal efficiencies were 65.13%, 79.67%, and 61.51%, respectively, and the aromaticity, humification, molecular weight, and polymerization of organics were all significantly reduced. The surface morphology and elemental valence analysis of nano zero-valent iron (nFe0 ) before and after the reaction revealed the formation of iron-based (hydrated) oxides, such as Fe2 O3 , Fe3 O4 , FeOOH, and Fe (OH)3 , on the surface of the nFe0 . Refractory organics were removed by Fenton-like reactions in the homogeneous and heterogeneous adsorption-precipitation of iron-based colloids. At the same time, UV radiation accelerated the formation of Fe2+ on the nFe0 surface and promoted the Fe3+ /Fe2+ redox cycle to a certain extent, enhancing the removal of refractory organics. The results provide a theoretical basis for the application of the UV/nFe0 /H2 O2 system to remove refractory organics in the effluent produced by the biological treatment of landfill leachate. PRACTITIONER POINTS: The UV/nFe0 /H2 O2 process is effective in refractory organics removal in leachate treatment. Humus in leachate was largely destroyed and mineralized by the UV/nFe0 /H2 O2 process. Active nFe0 material participated in the Fenton-like process and was promoted by UV. The effects of nFe0 material and UV introduction were investigated.