Halogenated bisphenol F compounds: Chlorination-mediated formation and photochemical fate in sunlit surface water

Halogenated bisphenol compounds are prevalent in urban water systems and may pose greater environmental risks than their bisphenol precursors. This study explored the formation of halogenated bisphenol F (BPF) in water chlorination and their subsequent transformation behaviors in receiving waters. The kinetics and pathways of BPF halogenation with chlorine, bromine, and iodine were firstly investigated. BPF chlorination followed second-order kinetics, with pH-dependent second-order rate constants (k_app) ranging from 1.0 M^-1s^-1 at pH 5.0 to 50.4 M^-1s^-1 at pH 9.0. The k_app of BPF with bromine and iodine were 4 - 5 orders of magnitude higher than those of chlorine. The degradation potential of halogenated BPF products in sunlit surface waters was also evaluated, focusing on both direct and indirect photolysis. Indirect photolysis, involving reactions with excited triplet state of CDOM (³CDOM*), ^•OH and ¹O₂, emerged as the primary degradation pathway for BPF, while both direct photolysis and indirect photolysis with ³CDOM* predominated for mono- and dihalogenated BPF products. Compared with BPF, the photodegradation of halogenated products was significantly enhanced. Photolysis experiments in wastewater-receiving wetland water demonstrated effective degradation of halogenated BPF products, highlighting the pivotal role of sunlight in their environmental fate. Overall, this study advances understanding of the formation and fate of halogenated BPF products and provides valuable insights for managing the environmental impacts of these emerging contaminants.