Preparation of particle electrodes for landfill leachate treatment by doping Cu2+-modified needle coke with Fe-based oxides extracted from iron tailings

Landfill leachate is a typically difficult-to-degrade organic wastewater that, if not treated properly will cause serious harm to human health and the ecological environment. Three-dimensional electro-Fenton (3DEF) technology has received widespread attention because of its high mass transfer efficiency and current utilisation, and no secondary pollution. In this study, the Fe/Cu-loaded needle coke particle electrode (Fe/Cu-NCPE) was prepared, using which a 3DEF system was constructed with DSA as the anode and Ni/ACF as the cathode to treat mature landfill leachate. The optimal preparation conditions of the Fe/Cu-NCPE were obtained as Cu2+-modified needle coke: Fe-based oxides: binder = 32:8:15, particle size of 5 ± 0.5 mm, and Cu2+ loading of 3 %. The spectral analysis shows that the Fe/Cu-NCPE prepared in this study is a kind of particle electrode with superior performance and good stability. The optimum conditions for treating landfill leachate at an applied voltage of 9 V, an initial pH of 2, and a Fe/Cu-NCPE dosage of 25 g/L resulted in the removal of COD, colour, TN, and NH3-N of 94.2 %, 99 %, 90.3 %, and 93.8 %, respectively. In the 3DEF system for landfill leachate treatment, H2O2 is generated at the cathode and polarized Fe/Cu-NCPE surface, which is activated by loaded Fe2+ and Cu+ in a Fenton(-like) reaction to produce •OH; Meanwhile active chlorine is generated by anodic electrocatalytic oxidation of Cl-. They attack humic acid and other organics in the wastewater as well as nitrogenous reductive substances to degrade them.