Degradation of waste leachate during photoelectrocatalytic synergistic processes: spectroscopic techniques and mechanistic analysis

In this study, a photoelectrocatalytic treatment technology based on stabilized supported photoelectrodes (NiF/FCN/BMO) constructed from Z -scheme Fe-g-C 3 N 4 /Bi 2 MoO 6 (Fe 3 CN/BMO-3) photocatalysts and nickel foam (NiF) is proposed for the treatment of difficult-to-degrade waste leachate. Efficient degradation of waste leachate was achieved through the synergistic action of photocatalysis and electrocatalysis. The photoelectrocatalytic process significantly promoted the separation of photogenerated electron-hole pairs and accelerated the migration rate of photogenerated carriers in the presence of an applied electric field. Three-dimensional fluorescence spectroscopy (3D EEMs) was used to analyze the changes in fluorescence intensity of the difficult-to-degrade substances during the degradation process, confirming that humic acid-like substances were effectively removed. Meanwhile, the results of UV–vis spectroscopy showed that the content of UV-absorbing groups, such as conjugated unsaturated bonds and aromatic structures, was significantly reduced in the waste leachate. Further, two-dimensional correlation spectroscopy (2DCOS) was utilized to deeply explore the dynamic changes of substances during the degradation process. The economic performance evaluation showed that the final cost of this photoelectrocatalytic technology for the degradation of waste leachate was 0.40 USD/m 3 , which has significant economic benefits. This study aims to develop a biological pretreatment process that converts recalcitrant organic matter into biodegradable small molecules, providing a new approach for the graded treatment of highly stable organic wastewater