Kinetics of chloroform formation from humic and fulvic acid chlorination

Chloroform formation from chlorination of aquatic humic and fulvic acid solutions was studied. Second order overall kinetic model was assumed, first order with respect to chlorine and precursor content. Rate constants have been measured, resulting in values that varied significantly with reaction conditions, in the range of 0.177 - 7.206 [L/mmol h], mainly for fulvic acid. The activation energy deduced from experiments carried out at different temperatures also increased notably when decreasing pH from 8 to 7. Increases of up to 60% were computed, where highest values were measured for humic acid. It is noteworthy the dependence observed on reaction time: higher activation energy resulted for longest reaction periods. Differences in the range of 40% have been reported. This effect is attributed to the existence of simultaneous reactions, each with different activation energy, competing for trihalomethanes formation.