Electrochemical oxidation for low concentration of aniline in neutral pH medium: Application to the removal of aniline based on the electrochemical polymerization on a carbon fiber

Aniline, which causes serious environmental problems, was electrochemically treated and thereby removed from aqueous solution. This method demonstrated herein is based on the formation of polyaniline at an electrode surface by electrochemical oxidation. Initially, the electrode behavior of aniline at several conditions was investigated on a platinum, glassy carbon (GC), and carbon fiber (CF) electrode using voltammetric techniques. On the platinum electrode, aniline did not polymerize at low concentrations. However, electropolymerization of aniline was observed on both the GC and CF electrodes even at low concentrations in neutral pH solutions. The removal of aniline was carried out using a CF bundle with a large surface area. High removal efficiency for aniline was obtained by applying potentials greater than 0.8 V. Although generation of p-benzoquinone as a byproduct was observed during electrochemical treatment, its generation was suppressed by applying a potential lower than 0.9 V. The cyclic voltammograms and X-ray photoelectron spectra of the CF after the treatment for aniline solution showed that polymeric aniline existed on the CF surface. The maximum surface coverage of electropolymerized aniline was estimated to be about 1.49 × 10^-8 mol/cm². Furthermore, the continuous treatment of aniline was demonstrated using a flow system.