Addition of nitrite enhances the electrochemical defluorination of 2-fluoroaniline

This study introduces a novel approach that uses the interaction of pollutants with added nitrite to produce diazonium salts, which cause in situ self-assembly of the pollutants on carbon electrodes, to improve their 2-fluoroaniline (2-FA) defluorination and removal performance. The 2-FA degradation performance, electrode properties, electrochemical properties and degradation pathway were investigated. The reactor containing NO₂^- achieved a 2-FA removal efficiency of 90.1% and a defluorination efficiency of 38% within 48h, 1.4 and 2.3 times higher than the corresponding results achieved without NO₂^-, respectively. The residual NO₂^- was less than 0.5mg/L in the reactor containing added NO₂^-, which would not cause serious secondary pollution. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) results proved that the carbon anode surface was successfully modified with benzene polymer, and electrochemical tests confirmed that the electrochemical activity of the modified anode was enhanced significantly. The C-F bond was weakened by the effect of the positive charge of the benzenediazonium groups, and the high electrochemical activity of the carbon anode enhanced the electrochemical performance of the system to accelerate defluorination. Thus, the present electrical method involving nitrite nitrogen is very promising for the treatment of wastewater containing fluoroaniline compounds.