A triple system of Fe(III)/sulfite/persulfate: Decolorization and mineralization of reactive Brilliant Red X-3B in aqueous solution at near-neutral pH values

Abstract

We report herein the use of ferric iron (Fe 3 + ) and sulfite (SO 3 2 −) to activate persulfate (S 2 O 8 2 −). Decolorization and mineralization of reactive Brilliant Red X-3B (a model azo dye) by an Fe(III)/sulfite/persulfate triple system have been investigated in aqueous solutions. Initial pH and dis- solved oxygen are important factors influencing X-3B decolorization in this system. The rapid decoloriza- tion process occurred in 30 min and about 85% of X-3B was decolorized in this triple system at initial pH 6.0. Moreover, about 66.4% of the TOC was removed through reaction for 36 h. The generation of SO 4 •−and HO •were identified through radical quenching experiments and by electron spin resonance (ESR), which contributed to 61.1% and 28.9% of the oxidation process. Degradation products of X-3B were iden- tified by LC-ESI-MS, and the degradation pathway was proposed. Furthermore, other organic pollutants, such as Orange II, metoprolol, imipramine, naproxen, estradiol, and amitriptyline, could also be efficiently degraded in this triple system. The results of the present work suggest that the Fe(III)/sulfite/persulfate triple system can be used for the rapid decolorization and partial mineralization of dyeing wastewater at near-neutral pH values.