Comparative studies on the degradation of aqueous 2-chloroaniline by O3 as well as by UV-light and γ-rays in the presence of ozone

Chlorinated anifines are frequently used in the industry as starting materials for chemical synthesis. Hence, such compounds can occur as pollutants in waste waters. In the present study 2-chloroaniline (2-ClA) was selected as the representative model for this class of compounds. The objectives of the work concerned 2-ClA degradation in water by ozonation as well as by photolysis (UV-light of 254 nm) and radiolysis (gamma-rays) in the presence of ozone. In all three series of experiments, the same amount ozone was passed through the 2-ClA solution at pH = 6.9 during the treatment. The degradation process was followed as a function of the action time and by chemical analysis of the major products. Based on the actinometry of the monochromatic UV-light (lambda = 254 nm, E = 4.88 eV/hv) and dosimetry data, the obtained degradation yields and products by the three series of experiments are compared. It was established that the synergic effect of gamma-rays and ozone leads to the most efficient degradation of 2-ClA, followed by UV/O-3-combination and pure ozonation. The same sequence is also observed by cleavage of the Cl-atom. The formation of the other major products: ammonia, formaldehyde, oxalic acid and the total yield of carboxylic acids depend on the media. Probable reaction mechanisms are suggested for explanation of the experimental results. (C) 2002 Published by Elsevier Science Ltd.