The addition of Cu2+ ions to the classical Fenton reaction (Fe2+ plus H2O2 at pH 3) is found to accelerate the degradation of organic compounds. This synergic effect causes an approximately 15 % additional reduction of the total organic carbon (TOC), representing an overall improvement of the efficiency of the mineralization of phenol. Although Fe2+ exhibits a high initial rate of degradation, the degradation is not complete due to the formation of compounds refractory to the hydroxyl radical. The interference of copper ions on the degradation of phenol by the Fenton reaction was investigated. In the presence of Cu2+, the degradation is slower, but results in a greater reduction of TOC at the end of the reaction (t = 120 min). In the final stages of the reaction, when the Fe3+ in the solution is complexed in the form of ferrioxalate, the copper ions assume the role of the main catalyst of the degradation

Um estudo da interferência de íons Zn2+ na reação de Fenton (Fe2+/Fe3+ + H2O2) na degradação de fenol é relatado. Um dos intermediários formados inicialmente na reação, catecol, pode reduzir Fe3+ a Fe2+, e na presença de H2O2 inicia um ciclo redox catalítico. Nas etapas iniciais da reação, este ciclo mediado por catecol torna-se a principal via de degradação térmica de fenol e seus produtos de oxidação. A adição de íons Zn2+ aumenta o tempo de persistência do catecol, provavelmente por estabilização do radical semiquinona via complexação.

A study of the interference of Zn2+ ions on phenol degradation by Fenton reaction (Fe2+/Fe3+ + H2O2) is reported. One of the first intermediates formed in the reaction, catechol, can reduce Fe3+ to Fe2+ and, in the presence of H2O2 initiates an efficient catalytic redox cycle. In the initial stages of the reaction, this catechol-mediated cycle becomes the principal route of thermal degradation of phenol and its oxidation products. The Zn2+ ion addition enhances the persistence time of catechol, probably by stabilization of the corresponding semiquinone radical via complexation.