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

Abstract Sulfate radicals (SO 4 − ) 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 Co 2+ 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 μg/L bromoform and 100.7 μg/L dibromoacetic acid (DBAA) were found after 120 h when 2 mg/L NOM, 0.1 mM Br − , 1.0 mM PMS, and 5 μL Co 2+ 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 Co 2+ . The data indicate that both PMS and SO 4 − can transform Br − to reactive bromine species which react with NOM to form halogenated by-products. Less DBP formation in Co 2+ -PMS systems was due to the further destruction of DBPs by SO 4 − . 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 Co 2+ /PMS reaction systems, which should be taken into consideration in the application of SO 4 − based oxidation technologies.