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The electrochemical degradation of i00 ppm aniline and 4-chloroaniline in basic aqueous solutions of pH ranging between I0.i and 12.7 has been studied at constant current intensity using a Pb/PbQ anode and a carbon-polytetrafluoroethylene O2-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 H~O2 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 mAcm -2 or higher, as well as a decrease of their half-lifetimes when current intensity increased. A gradual decrease in total organic carbon (TOC) for 0.05 tool dm 3 NaOH solutions with electrolysis time was always found. Product analysis of these electrolyzed solutions by gas chromatographymass spectroscopy (GC-MS) and HPLC allowed the detection of nitrobenzene and l-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 HO~ at the anode reaction layer. The effect of HO~ upon decomposition pathways of anilines is discussed.

The degradation of 4-chiorophenol in acidic solution of pH -3.5 has been studied by different electrochemical methods involving 11202 electrogeneration from an 02-diffusion cathode. While the solution is slowly mineralized by anodic oxidation in the presence of 11202, the rate for organic carbon removal increases notably by electro-Fenton, photoelectro-Fenton, and peroxi-coagulation, where Fe2 acts as catalyst to produce oxidizing 0H from electrogenerated H202. A complete mineralization was only reached in the photoelectro-Fenton process. For peroxi-coagulation, the removal of organic carbon in solution is mainly due to the coagulation of dechlorinated intermediates with the Fe(OH)3 precipitate formed. The decay for substrate concentration is faster by electro-Fenton and photoelectro-Fenton than by peroxi-coagulation. In all methods, the initial hydroxylated intermediate is 4-chloro-1,2-dihydroxybenzene, which is further oxidized with loss of chloride ion to yield maleic and fumaric acids. Fe3 complexes are produced in the processes using iron ions. These complexes are slowly mineralized by electro-Fenton and rapidly photodecomposed to CO2 by photoelectro-Fenton processes. The apparent current efficiencies for the mineralization processes have been determined. A general pathway for the degradation of 4-chlorophenol by the different methods studied is proposed.