Hydrolysis and Chlorination of 2,6-Dichloro-1,4-benzoquinone under conditions typical of drinking water distribution systems

• Published in: Water research (Oxford) 2021-07, Vol.200, p.117219-117219, Article 117219
• Main Authors: Mohan, Aarthi, Reckhow, David A.
• Format: Article
• Language: English
• Subjects: Disinfection by- products; Distribution system; Halobenzoquinones; Kinetics; Stability; Temperature
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2021.117219

•2,6-dichlorobenzoquinone (DCBQ) transformation rates were systematically monitored.•DCBQ rate laws were proposed and rate constants were experimentally determined.•Hydrolysis was sensitive to both temperature and pH.•Chloramine impact on DCBQ degradation was not significant at pH~7.2.•DCBQ chlorination time scales did not compliment the prior reported high concentrations in free chlorine systems. Halobenzoquinones (HBQs) are emerging disinfection by-products (DBPs) that are postulated drivers of bladder carcinogenicity. Prior assessments of 2,6-dichloro-1,4-benzoquinone (DCBQ) occurrence in drinking water distribution systems have revealed a gradual decline with increasing distance from points of entry. While this signals a degradation pathway, there is limited quantitative data on rate of that degradation. A systematic evaluation of DCBQ hydrolysis was performed, resulting in a rate law that is first order in both hydroxide [OH−] and [DCBQ]. The impact of temperature on that rate was characterized according to the Arrhenius relationship. Under the conditions tested (pH~7.2, T = 20°C) chloramine did not significantly impact DCBQ concentrations. However, DCBQ was rapidly degraded in solutions containing free available chlorine (FAC). Kinetic analysis showed non-integer order with respect to FAC. Further investigation led to a model that invoked reaction with dichlorine monoxide (Cl2O) as well as FAC. [Display omitted]