Kinetics and thermodynamics of the formation of trihalomethanes

Abstract

The effect of contact time and temperature on the formation of trihalomethanes (THMs) was studied during the chlorination of Khandaq El-Sharqi canal, Egypt, under laboratory condition. Samples were collected from four positions of Khandaq El-Sharqi canal (Itay El-Baroud, Dinshal, Damanhour and El-Zawya). Increasing trihalomethanes formation has been observed with increasing contact time and temperature. In the presence of excess chlorine, trihalomethanes formation proceeds as a pseudo-first-order reaction. The rate constants of the formation of trihalomethanes at different temperatures (10, 20, 30 and 40 °C) were calculated. Values of rate constant given for chloroform (CFM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and total trihalomethanes (TTHMs) approached each other, whereas chloroform attained a higher value for each temperature. Thermodynamic parameters of activation (ΔH # , ΔS # and ΔG #) for the formation of trihalomethanes were calculated by least square procedure program at 25 °C. The data showed that there is no significant change observed in ΔG # , and this is presumably due to the compensation between ΔH # and ΔS # to each other.

Minimizing Trihalomethane Formation through Source Water Monitoring and Optimizing Treatment Practices

“…THMs formation kinetics and its activation energy were examined by Masoud et al (2019) and pseudo first-order rate constants for various THM species were on the order of 10 -5 s -1 with an activation energy ranging from 28.5 to 30.2 kJ mol -1 (Table 2-1). The data show that the rate constant for chloroform was higher than other THM under the same experimental conditions.…”