Reactivity of Chlorine Radicals (Cl• and Cl2•–) with Dissolved Organic Matter and the Formation of Chlorinated Byproducts

• DOI: 10.1021/acs.est.0c05596
• Publication Date: 2020-12-21T14:21:50Z
• Authors: Yu Lei; Xin Lei; Paul Westerhoff; Xinran Zhang; Xin Yang
• Keywords: Reactivity; Flash photolysis; Hydroxyl radical

Chlorine radicals, including Cl• and Cl2•-, can be produced in sunlight waters (rivers, oceans, lakes) or water treatment processes (e.g., electrochemical advanced oxidation processes). Dissolved organic matter (DOM) is a major reactant with, scavenger of, Cl2•- water, but limited quantitative information exists regarding the influence of DOM structure on its reactivity with Cl2•-. This study aimed at quantifying reaction rates formation chlorinated byproducts from reactions DOM. Laser flash photolysis experiments were conducted to quantify second-order rate constants 19 isolates (kDOM-Cl•) (kDOM-Cl2•-), compare those hydroxyl radical (kDOM-•OH). The values for kDOM-Cl• ((3.71 ± 0.34) × 108 (1.52 1.56) 109 MC-1 s-1) orders magnitude greater than kDOM-Cl2•- ((4.60 0.90) 106 (3.57 0.53) 107 s-1). negatively correlated weight-averaged molecular weight (MW) due diffusion-controlled reactions. high aromaticity total antioxidant capacity tended react faster During same experiments, we also monitored through evolution chlorine (TOCl) as function oxidant exposure (CT value). Maximum TOCl occurred CT 4-8 10-12 M·s 1.1-2.2 10-10 These results signify importance scavenging radicals potential risks producing unknown toxicity.