Competitive degradation behavior between aniline and nitrobenzene in fenton process

Abstract

This research was focused on investigation of competitive degradation of aniline and nitrobenzene which have been frequently found as the mixture solution of industrial wastewater. Due to the difference of functional groups in benzene ring of both substances, aniline has the function group as M .2 while nitrobenzene has the functional group as NO2, the behavior of Fenton reaction would be accordingly different. It was revealed that degradation reactions of nitrobenzene and aniline were influenced by initial concentrations of hydrogen peroxide and ferrous ion. Initial pH exerted small effect on oxidation of both substances. With the excess of hydrogen peroxide or ferrous ion, the oxidation reactions were found to follow the pseudo-first order reaction rate, which in all cases nitrobenzene provided higher value of apparent rate constant, k, than that of aniline. In addition, nitrobenzene was also degraded with the initial rate, r, faster than aniline. At the optimum condition for 1 mM of aniline and nitrobenzene degradation at 20 mM of hydrogen peroxide and 0.5 mM of ferrous ion, the k values of aniline and nitrobenzene were 0.3621 and 0.4805 min-1 respectively, r values for aniline and nitrobenzene were 0.362 and 0.481 mM•min-1 respectively. The explanation of this behavior might come from the fact that the electrophilic addition of hydroxyl radical with the double bond in nitrobenzene is more preferable than the hydrogen abstraction of the single bond of aniline. The aniline degradation was improved in the presence of nitrobenzene even at small amount. High amounts of aniline (more than 50% of nitrobenzene in the mixture) inhibited the degradation of nitrobenzene.