Efficiency and mechanism of organic matter removal from landfill leachate via a UV-synergized CuS-activated H2O2 Fenton-like system

While copper-based Fenton-like systems can effectively degrade organic matter in the effluent from membrane bioreactor (MBR), the performance is hindered by sluggish Cu 2+ /Cu + cycling and oxidant inefficiency. In this study, a UV-synergized CuS-activated H 2 O 2 system was constructed, and the removal efficiency and synergistic mechanism for organic matter in MBR effluent were investigated. Under optimized conditions (UV=14   W, CuS=0.06   g/L, [H 2 O 2 ]=50   mM, pH=3.0, t=60   min), the UV/CuS/H 2 O 2 system achieved removal efficiencies of 62.49%, 89.81%, and 38.48% for UV 254 , color number (CN), and total organic carbon (TOC) respectively. This performance is attributed to the disruption of aromatic structures and a reduction in molecular weight, condensation degree, and humification degree. Reactive oxygen species characterization confirmed the presence of hydroxyl radicals ( • OH), singlet oxygen ( 1 O 2 ) and superoxide radical anions (O 2 •− ) in the system, with O 2 •− identified as the dominant reactive species driving the process. Through analysis of the material morphology, distribution of copper compounds, and changes in oxidation states, the reaction mechanism of the UV/CuS/H 2 O 2 system can be summarized as homogeneous and heterogeneous Fenton-like reactions coupled with CuS adsorption, all of which are jointly promoted by the photochemical effects of ultraviolet radiation. Additionally, benzoic acid removal remained above 96% over six cycles with minimal Cu 2+ leaching, confirming the reusability and environmental compatibility of CuS. This study provides a theoretical basis for using the UV/CuS/H 2 O 2 system to remove organic matter from landfill leachate.