Degradation of Monoazo Pigments Red 53:1 and Red 48:2 by Fenton, Photo-Fenton and UV/Peroxide Reactions

• Published in: Clean : soil, air, water air, water, 2009-10, Vol.37 (10), p.799-805
• Main Authors: Ilha, Clóvis E. G., dos Santos, Antônio J. M. G., SouzaDe, Jurandir R.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Fenton reaction; Hydrology; Hydrology. Hydrogeology; Photo-Fenton reaction; Pigment degradation; UV/H2O2 system; Water treatment
• ISSN: 1863-0650; 1863-0669
• DOI: 10.1002/clen.200900108

The degradation reactions of two monoazo pigments, namely, Red 53:1 and Red 48:2, by Fenton, photo‐Fenton and UV/H2O2 systems have been studied. The efficiencies of the Fenton reactions increased with temperature, but the formation of solid agglomerates was observed when the reactions were carried out above 50°C indicating a coagulant action of Fe+2 or Fe+3. Photo‐Fenton reactions irradiated by sunlight presented the best rate constants for cleavage of the azo bond and the naphthalene rings. The UV/H2O2 system exhibited the highest efficiency with respect to the consumption of H2O2. The presence of a carbonyl group in the ortho position of the naphthol ring hampered the oxidation of pigment Red 48:2 by hydroxyl radicals. This finding may be explained in terms of the acceptor character of the COOH group, and suggests the formation of a complex containing two six‐membered rings between Fe+3 and the pigment molecule. Research Articles: The degradation reactions of two monoazo pigments, namely, Red 53:1 and Red 48:2, by Fenton, photo‐Fenton and UV/H2O2 systems have been studied. Photo‐Fenton reactions irradiated by sunlight presented the best rate constants for cleavage of the azo bond and the naphthalene rings. The UV/H2O2 system exhibited the highest efficiency with respect to the consumption of H2O2.