The effect and mechanism of the MW/CuS/H2O2 process in removing refractory organic matter from the effluent of biological treatment of landfill leachate

Although copper-based Fenton-like processes can remove refractory organics from the membrane bioreactor effluent of landfill leachate (referred to as MBR effluent), the kinetic limitations of the Cu 2+ /Cu + cycling lead to oxidant consumption, which further restricts the degradation efficiency. To address this issue, the microwave (MW)/CuS/H 2 O 2 Fenton-like process (pH = 3.0, MW = 160 W, CuS = 96 mg/L, [H 2 O 2 ] = 75 mM, t  = 15 min) was used to treat the MBR effluent. The results showed that this process efficiently removed UV 254 (69.26 %) and color number (CN, 94.45 %) and significantly reduced the degree of polymerization, aromaticity, and molecular weight of organics in the MBR effluent. Further reactive species experiments confirmed the presence of hydroxyl radicals ( • OH), singlet oxygen ( 1 O 2 ), and superoxide radicals (O 2 •− ) in the process, with O 2 •− acting as the primary reactive species. On the basis of the changes in the CuS morphology and valence state, it was indicated that the main mechanism of the MW/CuS/H 2 O 2 Fenton-like reaction is a synergy between homogeneous and heterogeneous Fenton-like processes, and the thermal effect of MW accelerated the cycling of the Cu 2+ /Cu + and the generation of reactive species. Finally, after 6 cycles of the CuS catalyst, the removal efficiency of benzoic acid (BA) remained above 70 %. This confirms the structural and chemical stability of CuS. This study provides a reference for overcoming the kinetic limitations of copper-based Fenton-like processes and improving the removal efficiency of refractory organics from the MBR effluent.