Decolorization of Orange II in Water Induced by Ferrous/Sulfite System at near Neutral pH Values

Abstract

In this study, Orange II, a typical and stable azo dye, was chosen as the target pollutant. The works on the decolorization of Orange II become more practical, due to its high chroma, potential carcinogenic effects and the difficulty of degradation. Orange II (10 mg·L-1) was efficiently decolorized at initial pH about 6 with an efficiency of 84% by Fe(II)-sulfite complexes after 60 min. As the initial concentration of sulfite ranged from 0.6 mmol·L-1 to 1.5 mmol·L-1 and the initial concentration of ferrous ranged from 0.1 mmol·L-1 to 0.5 mmol·L-1, the decolorization rate of Orange II increased gradually. Without UV-Vis irradiation, the initial decolorization rates of Orange II by Fe(II)-sulfite complexes increased as the initial concentration of Orange II increased from 2 mg·L-1 to 20 mg·L-1, thus following pseudo-first-order reaction kinetics. Consequently, Orange II could be effectively decolorized at near-neutral pH (5-7) by Fe(II)-sulfite system, thus having more advantages for water treatment. But further study is needed for reaction mechanism and improving mineralization rate of organic pollutants and pratical applicability.