Title

Concentration profiles of chlorine radicals and their significances in OH-induced dye degradation: kinetic modeling and reaction pathways

Document Type

Article

Publication details

Yuan, R, Ramjaun, SN, Wang, Z & Liu, J 2012, 'Concentration profiles of chlorine radicals and their significances in OH-induced dye degradation: kinetic modeling and reaction pathways', Chemical Engineering Journal, vol. 209, pp. 38-45.

Published version available from:

http://dx.doi.org/10.1016/j.cej.2012.07.127

Peer Reviewed

Peer-Reviewed

Abstract

In order to further understand the mechanism details during saline wastewater treatment by OH-based advanced oxidation processes (AOPs), the degradation efficiency of an azo dye Acid Orange 7 (AO7) in UV/H2O2 process was investigated as a function of a wide range of salinity and pH. Kinetic modeling results demonstrated that the inhibitory effect of Cl on AO7 degradation observed in the laboratory experiments could be attributed to both scavenging effect of Cl on OH and the much lower reactivity of chlorine radicals formed, although the chlorine radicals may be more abundant than OH. Such retardation behavior was favored under acidic conditions due to a lower yield of OH generated by the dissociation of ClOH•− to OH and Cl. Traces of Br had a greater inhibitory effect on AO7 bleaching rate than Cl. AOX (halogenated organic compounds adsorbable on activated carbon) was found to increase with the increasing content of Cl. Based on the intermediate products and especially several toxic halogenated byproducts identified by GC–MS, the possible degradation pathways of saline dyeing wastewater were proposed.