A kinetic study of the oxidation of phenol, o-chlorophenol and catechol byhydrogen peroxide between 298 K and 333 K: the effect of pH, temperature and ratio of oxidant to substrate

Kinetic studies on the oxidative degradation of phenol, o-chlorophenol and catechol present in dilute aqueous solutions in the concentration range bet ween 50 ppm and 1000 ppm by hydrogen peroxide were conducted in a batch rea ctor. The temperature was varied between 298 K and 333 K. Initial rates of conversion for phenolic compounds were extremely high compared with the lat er part of the reaction. The pH of the reaction medium also decreased subst antially during the reaction and reached a plateau in the range of 6.4 for phenol and 4.5 for catechol and chlorophenol. Conversions of phenolic subst rates were found to increase with an increase in initial substrate concentr ation and hydrogen peroxide/substrate ratio. For a fixed initial concentrat ion and hydrogen peroxide/substrate ratio, the conversion was found to be i n the order catechol > chlorophenol > phenol. The temperature of the reacti on medium was found to have a minimal effect on the degradation kinetics, p robably due to simultaneous thermal decomposition of hydrogen peroxide at e levated temperature. A probable mechanistic explanation of the experimental data based on reactivity of the phenolic compounds and their stable oxygen ated intermediates is discussed. (C) 1999 Society of Chemical Industry.