Fate of organic nitrogen during electrooxidation over conductive metal oxide anodes

The electrooxidation of nitrogen-containing molecules (urea, reactive dye blue 4, acetonitrile, formamide, guanidine, and pyridazine) over Pt-Ti and Ti/RuO₂ anodes is investigated. The product distribution of the electrochemical mineralization of nitrogen is monitored. Nitrogen mineralization generally leads to inorganic pollutants (NH₃/NH₄ ⁺ and/or nitrite and nitrate ions). Amidic and aminic compounds were found to react according to both homogeneous (acid hydrolysis) and heterogeneous (direct electrooxidation) pathways, with a rate depending on the original state of oxidation of nitrogen. Heterocyclic and multiple-bond carbonnitrogen molecules were converted but with negligible mineralization of nitrogen due to the stability of their first oxidation intermediates. The obtained results can be useful for the design of further treatment routes after electrooxidation or the definition of simultaneous strategies for inorganic pollutants elimination.