Fe-N-C-supported LaFeO3 heterojunction electrodes for efficient copper and fluoride removal in symmetric capacitive deionization

Copper and fluoride ions were dominant pollutants requiring urgent treatment in electroplating wastewater. However, the study on the simultaneous removal of copper and fluoride ions from electroplating wastewater remained relatively limited. Taking advantage of the dual-electrode configuration in capacitive deionization (CDI) technology, this study constructed a heterojunction structure LaFeO₃/Fe-N-C-X using Fe-N-C composite modified LaFeO₃ as the electrode material for the removal of copper and fluoride contaminants. First, we investigated the performance of LaFeO₃/Fe-N-C-X as a single electrode for treating copper ions and fluoride ions separately. A symmetric CDI electrode system was subsequently developed for the simultaneous removal of both ions. The adsorption capacities of LaFeO₃/Fe-N-C-1 for copper and fluoride ions reached 599.22 mg/g and 385.13 mg/g, respectively. Combining experimental results with density functional theory (DFT) calculations, we analyzed the removal mechanisms of copper and fluoride ions by the electrode material. Comparative analysis revealed distinct mechanisms between asymmetric and symmetric CDI systems. Furthermore, this study extended to actual electroplating wastewater containing copper and fluoride ions, and conducted scale-up experiments based on the original laboratory CDI system. This research provides theoretical and practical foundation for the treatment of copper and fluoride contaminants in actual electroplating wastewater, bridging the gap between fundamental studies and engineering applications.