During drinking water treatment, chlorination leads to the degradation of bisphenol A (BPA) and the formation of chlorinated derivatives (ClxBPA) which have higher estrogenic activity than BPA. In addition, the production of bisphenol S (BPS) and bisphenol AF (BPAF) as alternatives is increasing with the pressure to limit the use of BPA. Due to their structural similarity with BPA, chlorinated BPS and chlorinated BPAF are easily formed during chlorination. In this study, we investigated the UV-LED/chlorine process which produces various reactive chlorine species (RCS) along with OH radical to remove both target bisphenols (BPs) and chlorinated BPs in water. We also examined the effects of water components, such as humic acid, bicarbonate, nitrate, on the removal kinetics BPA, BPS, and BPAF. In addition, we calculated the contribution of each radical (RCS and OH radical) by combining the radical scavenging experiments with the calculated second-order rate constants of BPs reacting with each radical by transition state theory. Three bisphenols were completely degraded within 5 min, predominantly contributed by RCS. ClxBPA, ClxBPS, and ClxBPAF were identified as major transformation products (TPs), and these TPs were effectively removed in 10 min. FInally, we proposed degradation pathways of BPA, BPS, and BPAF based on identified TPs and time-dependent acute toxicity during the UV-LED/chlorine process.

Fig. 1. The contribution of each radical during UV/chlorination of three Biphenols

Fig. 2. The time profiles of responses the byproducts by LCQTOF/MS during UV/chlorination of three BPs

Jaewon Lee

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