Unveiling the degradation of membrane concentrated landfill leachate during enhanced photocatalysis using spectroscopic approaches

Abstract

Membrane concentrated landfill leachate (MCLL) is a complex wastewater with high amounts of recalcitrant organic pollutants. TiO2-based photocatalysis is a promising technique to treat recalcitrant organic pollutants, but the low quantum efficiency limits its application. In this work, an enhanced photocatalysis approach was proposed to treat MCLL based on the synergistic effects of TiO2, CuWO4 and H2O2, through which 90.56 ± 1.1% COD and 71.83 ± 1.3% TOC can be removed, and the degradation process followed pseudo first-order kinetics. The structural changes of MCLL were examined by spectroscopic techniques. UV–Vis spectral results indicate the effective removal of chromophores in MCLL with decreases in molecular weight, aromaticity and CC/CO content. Fluorescence excitation-emission matrix coupled with parallel factor analysis was used to characterize the changes of fluorescent substances during the enhanced photocatalysis process. Two fluorescent components, i.e., humic-like and fulvic-like components, were identified, both of which were effectively removed. Two-dimensional correlation spectroscopy suggested the degradation of substances in MCLL in the order: humic-like > fulvic-like components & unsaturated conjugate structure > the aromatic structure containing benzene ring. This work provides a deep understanding of structural changes of MCLL and offers a guidance for the treatment of MCLL through enhanced photocatalysis by H2O2 + TiO2 + CuWO4 synergism.