Electrochemical oxidation of wastewaters polluted with aromatics and heterocyclic compounds

In this work, the conductive-diamond electrochemical oxidation of several aromatics (phenol, 4-chorophenol, 2-naphtol) and heterocyclic compounds (2,6-dimethyl-pyridine, thiophene) were studied. The results obtained are compared with those obtained in the oxidation with Fenton reagent and with ozone at pH 12. Significant differences are observed among the three technologies and between the range of pollutant concentration studied [10(2)-2x10(3) mg dm(-3) of chemical oxygen demand (COD)]. For weakly loaded synthetic wastes (COD around 10(2) mg dm(-3)) the three technologies are able to diminish the COD significantly. The dose of oxidant required to obtain the maximum removal increases importantly in the series Fenton oxidation < ozonation < electrolysis. At high pollutant concentrations (COD around 2x10(3) mg dm(-3)) results obtained change abruptly. The electrolytic technology reduces the COD almost completely and the total organic carbon (TOC) of all the wastes, and ozonation becomes less effective in the COD removal. Even for some compounds, the Fenton oxidation overcomes the COD removals obtained by ozonation, although the TOC removal is still very low as compared with that obtained by ozonation and especially by electrochemical treatment. The differences between technologies in the dose of oxidant required become negligible in the COD removal percentages attained. The results have been used to guess some insights about the oxidation mechanisms in this electrolytic process. (c) 2007 The Electrochemical Society.