Azo dye degradation using Fenton type processes assisted by UV irradiation: A kinetic study

Application of Fenton and photo-Fenton type processes, UV/Fe2+/H2O2 and UV/Fe0/H2O2, for dye wastewater treatment was investigated. In the first stage of the study, Fenton type processes were optimized regarding the iron catalyst concentration and the iron catalyst/H2O2 ratio. In the next step, Fe2+/H2O2 and Fe0/H2O2 at optimal process parameters were combined with UV radiation in order to enhance dye degradation. The destruction of model organic pollutant, azo dye C.I. Acid Orange 7 (AO7), was monitored on the basis of decolorization and mineralization extents, determined by UV–vis and TOC analyses, respectively. All studied processes have shown high efficiency in the bleaching of the studied dye model solution with complete decolorization achieved in all cases. Mineralization extents depended on the type and the dosage of added iron catalysts for Fenton type reaction. The highest mineralization extent was achieved by UV/Fe0/H2O2, 90.09% of TOC removal. A quantum yield of AO7 organic dye, Φ = 6.5 × 10−3 mol Einstein−1, was determined on the basis of decolorization of AO7 by direct photolysis.