Cl and Cl2- radicals contribute to the degradation of trace organic contaminants (TrOCs) such as pharmaceutical and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs). However, little is known about their reaction rate constants and mechanisms. In this study, the reaction rate constants of Cl and Cl2- with 88 target compounds were determined using laser flash photolysis. Decay kinetics, product buildup kinetics and competition kinetics were applied to track the changes in their transient spectra. Cl exhibited quite high reactivity toward TrOCs with reaction rate constants ranging from 3.10×109 to 4.08×1010 M-1s-1. Cl2- was less reactive but more selective, with reaction rate constants varying from &lt;1×106 to 2.78×109 M-1s-1 . Three QSAR models were developed, which were capable of predicting the reaction rate constants of Cl2- with TrOCs bearing phenol, alkoxy benzene and aniline groups (Fig. 1). The reaction mechanism were proposed via observation of transient intermediates using time-resolved spectroscopy (Fig. 2). Cl could react with TrOCs through multiple pathways since more than one transient intermediates were detected simultaneously. Single electron transfer was the major reaction mechanism of Cl2- reactions with TrOCs bearing phenols, alkoxy-benzenes and anilines groups . Cl2- was found to play an important role in TrOC degradation, though it is often neglected in previous studies. The results improve understanding of the halogen radical chemistry involved in TrOCs’ degradation.

Rate constants and mechanisms of the reactions of Cl and Cl2- with trace organic contaminants

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.