Reactivity of Chlorine Radicals (Cl⢠and Cl2â¢-) with Dissolved Organic Matter and the Formation of Chlorinated Byproducts.
Environ Sci Technol
; 55(1): 689-699, 2021 01 05.
Article
en En
| MEDLINE
| ID: mdl-33346661
ABSTRACT
Chlorine radicals, including Cl⢠and Cl2â¢-, can be produced in sunlight waters (rivers, oceans, and lakes) or water treatment processes (e.g., electrochemical and advanced oxidation processes). Dissolved organic matter (DOM) is a major reactant with, or a scavenger of, Cl⢠and Cl2â¢- in water, but limited quantitative information exists regarding the influence of DOM structure on its reactivity with Cl⢠and Cl2â¢-. This study aimed at quantifying the reaction rates and the formation of chlorinated organic byproducts produced from Cl⢠and Cl2â¢- reactions with DOM. Laser flash photolysis experiments were conducted to quantify the second-order reaction rate constants of 19 DOM isolates with Cl⢠(kDOM-Clâ¢) and Cl2â¢- (kDOM-Cl2â¢-), and compare those with the hydroxyl radical rate constants (kDOM-â¢OH). The values for kDOM-Cl⢠((3.71 ± 0.34) × 108 to (1.52 ± 1.56) × 109 MC-1 s-1) were orders of magnitude greater than the kDOM-Cl2â¢- values ((4.60 ± 0.90) × 106 to (3.57 ± 0.53) × 107 MC-1 s-1). kDOM-Cl⢠negatively correlated with the weight-averaged molecular weight (MW) due to the diffusion-controlled reactions. DOM with high aromaticity and total antioxidant capacity tended to react faster with Cl2â¢-. During the same experiments, we also monitored the formation of chlorinated byproducts through the evolution of total organic chlorine (TOCl) as a function of chlorine radical oxidant exposure (CT value). Maximum TOCl occurred at a CT of 4-8 × 10-12 M·s for Cl⢠and 1.1-2.2 × 10-10 M·s for Cl2â¢-. These results signify the importance of DOM in scavenging chlorine radicals and the potential risks of producing chlorinated byproducts of unknown toxicity.
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Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Contaminantes Químicos del Agua
/
Purificación del Agua
Idioma:
En
Revista:
Environ Sci Technol
Año:
2021
Tipo del documento:
Article
País de afiliación:
China