Mechanism insights into activation of hydroxylamines for generation of multiple reactive species in photochemical degradation of bromophenols

Photolysis of bromophenols and nitrogen cycle are two common processes in the natural water bodies. In the study, effect of hydroxylamine (HA), an intermediate of nitrogen cycle, on UV photolysis of bromophenols in the aqueous solution was investigated under different conditions. It was found that HA presence not only changed formation of reactive species, also varied degradation pathways of 2,4,6-tribromophenol (TBP). During photolysis of TBP, carbon-centered radicals (C ), H and e aq − were produced, while new radicals of OH, NO 2 and NH 2 were produced after addition of HA. Moreover, the added HA greatly inhibited hydrolysis of C via the reaction between them, thereby depressing formation of hydroxylated intermediates (e.g., monohydroxylated 2,6-dibromophenol), and improving debromination of TBP in UV/HA/TBP system. It is worth noting that two new nitro/amino byproducts of concern were detected in UV/HA/TBP system. They are proposed to be generated from the combination of C with NO 2 and NH 2 . Furthermore, nitro/amino byproducts were one of the major sink pathways of HA in UV/HA/TBP system. This is the first article to demonstrate the formation of nitro/amino byproducts form photodegradation of phenolic compounds in the presence of HA, and to clarify reaction mechanism for generation of OH, NO 2 and NH 2 from HA activation during photolysis of bromophenols in the aqueous solution.