Advanced Oxidation of Direct Red (DR 28) by Fenton Treatment

Advanced oxidation of Direct Red 28 (DR 28) in aqueous solution by Fenton's reagent using FeSO₄ as source of Fe (II) was investigated. Effects of the dyestuff and the reagent concentrations (H₂O₂ and Fe (II)) on oxidation of the azo dye were investigated by using a Box-Behnken statistical experiment design and the surface response analysis. Degradation and mineralization (conversion to CO₂ and H₂O) of the azo dye by Fenton treatment was evaluated following total organic carbon (TOC) and color removal. Dyestuff removal increased with increasing H₂O₂ and Fe (II) concentrations up to a certain level. Fe (II) had a more profound effect on dyestuff removal as compared to H₂O₂. Complete color removal (100%) was achieved in 5 minutes. However, mineralization of the dyestuff took 15 minutes and required higher doses of H₂O₂. Percent color removal was always higher than TOC removal indicating formation of colorless organic intermediates. Optimal H₂O₂/Fe (II)/dyestuff ratio resulting in the maximum TOC (99.2%) and color (100%) removals was found to be 1450/78/235(mg L⁻¹).