Efficient Decolorization of Azo Dye Orange II in a UV-Fe 3+ -PMS-Oxalate System.

The decolorization of azo dye Orange II using a UVA-Fe³⁺-PMS-oxalate system was studied. A series of experiments was performed to investigate the effects of several variables, including the pH, PMS dosage, Fe³⁺ concentration, oxalate concentration, and coexisting anions. The results revealed that a lower pH facilitated the decolorization, and relatively high decolorization efficiency (97.5%) could be achieved within 5 min at pH 3.0. The electron paramagnetic resonance (ESR) and radical quenching experiments revealed that SO₄^•− played a crucial role in the decolorization of Orange II (85.8%), ^•OH was of secondary importance (9%), and ¹O₂ made a small contribution to the decolorization (5.2%). Furthermore, the formation of ^•OH in the experimental system strongly depended on HO₂^•/O₂^•−. These reactive oxidants were able to directly attack the azo bond of the luminescent group in Orange II and initiate the decolorization process. The efficient UVA-Fe³⁺-PMS-oxalate system showed great application potential in the treatment of wastewater contaminated by azo dyes. [ABSTRACT FROM AUTHOR]