Formation of halogenated disinfection by-products in cobalt-catalyzed peroxymonosulfate oxidation processes in the presence of halides

Sulfate radicals (SO4 center dot-) generated by activation of peroxymonosulfate (PMS) and persulfate (PS) are highly oxidative and applied to degrade various organic pollutants. This research was designed to investigate formation of halogenated by-products in Co2+ activated PMS process in the presence of halides and natural organic matter (NOM). It was revealed that no halogenated by-products were detected in the presence of Cl- while 189 mu g/L bromoform and 100.7 mu g/L dibromoacetic acid (DBAA) were found after 120 h when 2 mg/L NOM, 0.1 mM Br-, 1.0 mM PMS, and 5 mu L Co2+ were present initially. These products are known as disinfection by-products (DBPs) since they are formed in water disinfection processes. Formation of DBPs was even more significant in the absence of Co2+. The data indicate that both PMS and SO4 center dot- can transform Br- to reactive bromine species which react with NOM to form halogenated by-products. Less DBP formation in Co2+-PMS systems was due to the further destruction of DBPs by SO4 center dot-. More DBPs species including chlorinated ones were detected in the presence of both Cl- and Br-. However, more brominated species produced than chlorinate ones generally. The total DBP yield decreased with the increase of Cl- content when total halides kept constant. This is one of the few studies that demonstrate the formation of halogenated DBPs in Co2+/PMS reaction systems, which should be taken into consideration in the application of SO4 center dot- based oxidation technologies. (C) 2016 Elsevier Ltd. All rights reserved.