ELECTROCHEMICAL DESTRUCTION OF ANILINE AND 4-CHLOROANILINE FOR WASTE-WATER TREATMENT USING A CARBON-PTFE O-2-FED CATHODE

The electrochemical degradation of 100 ppm aniline and 4-chloroaniline in basic aqueous solutions of pH ranging between 10.1 and 12.7 has been studied at constant current intensity using a Pb/PbO2 anode and a carbon-polytetrafluoroethylene O-2-fed cathode. Under these conditions, hydrogen peroxide was electrogenerated in the cell via a two-electron reduction of oxygen gas fed to the cathode. The current efficiency for H2O2 generation depended on the applied current intensity and the background electrolyte used. The concentration decay for each contaminant with electrolysis time was followed by high pressure liquid chromotography (HPLC). Kinetic analysis of these data showed a pseudo first-order decomposition reaction for both substrates at anodic current densities of 30 mA cm(-2) or higher, as well Bs a decrease of their half-lifetimes when current intensity increased. A gradual decrease in total organic carbon (TOC) for 0.05 mol dm(-3) NaOH solutions with electrolysis time was always found. Product analysis of these electrolyzed solutions by gas chromatography-mass spectroscopy (GC-MS) and HPLC allowed the detection of nitrobenzene and 1-chloro-4-nitrobenzene proceeding from the anodic decomposition of aniline and 4-chloroaniline, respectively. Maleic acid was also detected as intermediate and ammonia was found as final. product, Destruction of initial pollutants and intermediates is explained by their oxidative reactions with OH. and HO2. at the anode reaction layer. The effect of HO2. upon decomposition pathways of anilines is discussed.