Use of an acidic Fe/O2 cell for wastewater treatment:: Degradation of aniline

Solutions containing 0.50 mol dm(-3) Na2SO4 and aniline concentrations between 129 and 1000 ppm have been decontaminated using an acidic Fe/O-2 cell with an Fe anode and a carbon-poly(tetrafluoroethylene) O-2-fed cathode. This system produces spontaneously strong oxidizing radicals, such as OH. and HO2., which react with pollutants. Decontamination is more efficient for solutions with pH > 3 where intermediates coagulate with the Fe(OH)(3) precipitate formed. A 95% degradation is reached after 1 h of treatment of 129 ppm of aniline at initial pH 4 and at 35 degrees C. For higher substrate levels, pollutants are quickly destroyed if the pH is regulated between 4 and 5. After 2 h, solutions up to 500 ppm of aniline are almost completely degraded, whereas 81% of the degradation is reached for 1000 ppm of substrate. Benzoquinone and nitrobenzene are detected as intermediates. An insignificant accumulation of these products is found in the treatment of 1000 ppm of substrate, suggesting the formation of polymers that coagulate with the Fe(OH), precipitate. Low concentrations of ammonium and nitrate ions have been determined in treated solutions. The major part of the initial carbon and nitrogen is retained in the precipitate, indicating that coagulation of intermediates predominates over their mineralization. A reaction pathway for the degradation of aniline involving all intermediates detected is proposed. (C) 1999 The Electrochemical Society. S0013-4651(99)04-012-4. All rights reserved.