Chlorine dioxide (ClO2) has been widely adopted as an effective alternative disinfectant of chlorine to reduce chlorine disinfection by-products (DBPs) formation, such as trihalomethane (THMs) and haloacetic acids (HAAs). In this work, the reaction kinetics and degradation pathway of antipyrine (ANT) during ClO2 disinfection process were studied to investigate the feasibility of using ClO2 as oxidant to degrade ANT, a widely used anti-inflammatory analgesic in medical treatment. Experimental results demonstrated that ANT oxidation by ClO2 followed second-order kinetics, and the second-order rate constant (kapp) was determined to be 4.8×10-1 M-1s-1 at neutral pH. Higher pH could accelerate the reaction when pH&lt;9, while strong alkaline environment (pH &gt; 9) might significantly slow down the oxidation process. Degradation pathway of ANT with ClO2 was suggested based on the main intermediate products. C=C and C-N bond of ANT were vulnerable under electrophilic attack of ClO2. ANT was firstly transformed into ANT-Cl through single-electron-transfer (SET) and substitution reaction. Further oxidation of this intermediate product involved ring-opening reaction and de-carbonyl reaction. According to this study, ClO2 disinfection process could slowly but completely oxidize ANT, which provided a feasible way to degrade pharmaceuticals during drinking water treatment process.

Reaction kinetics and degradation pathway of antipyrine during chlorine dioxide disinfection process

253rd National Meeting (2017)

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