Electro-oxidation of Some Phenolic Compounds by Electrogenerated O₃ and by Direct Electrolysis at PbO₂ Anodes

The oxidative degradation of phenolic compounds (4-chlorophenol and 4-nitrophenol) was studied using different electrochemical systems involving ozone formation at PbO₂ anodes: (i) direct electrolysis at constant current; (ii) ex-situ use of O₃ and (iii) combined use of anodically generated stream of O₃/O₂ fed into the cathode where H₂O₂ is electrogenerated by O₂ reduction. We show that the latter advanced oxidation method gives the best results: it is a Fenton-type degradation of the target pollutants taking place in the cathodic compartment by reason of the highly oxidizing environment brought about by radicals that are formed mainly in the reactions of O₃ with OH₋ and HO_{2 −}.