Aniline mineralization by AOP's: anodic oxidation, photocatalysis, electro-Fenton and photoelectro-Fenton processes

The aniline degradation in acidic medium of pH approximate to 3 under photocatalytic and electrochemical conditions has been investigated. The efficiency for substrate mineralization in each process has been comparatively analysed by the decrease in TOC of aniline solutions. Particular emphasis has been made on the role of Fe(II) ions and H2O2. The electrochemical experiments performed in the presence of both species (electro-Fenton conditions) leads to a fast aniline mineralization, which is notably increased by WA irradiation (photoelectro-Fenton process). Zn photocatalysis with TiO2 suspensions, the presence of H2O2 and Fe(II) ions in solution notably increases the aniline degradation rate at the initial stages of the process, whereas the opposite effect occurs at long irradiation times. Benzoquinone, hydroquinone, nitrobenzene, phenol and 1,2,4-benzenetriol were detected as intermediates by HPLC in both, electrochemical and photocatalytic experiments, Short chain aliphatic acids, such as maleic and fumaric acids, were only found in the electrochemical experiments. Ammonium ions (75-80% of initial nitrogen) were generated in all solutions tested. A general reaction pathway that accounts for aniline mineralization to CO2 involving those products is proposed. (C) 1998 Elsevier Science B.V.