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

Abstract

Kinetic studies on the oxidative degradation of phenol, o-chlorophenol and catechol present in dilute aqueous solutions in the concentration range between 50 ppm and 1000 ppm by hydrogen peroxide were conducted in a batch reactor. The temperature was varied between 298 K and 333 K. Initial rates of conversion for phenolic compounds were extremely high compared with the later part of the reaction. The pH of the reaction medium also decreased substantially 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 substrates were found to increase with an increase in initial substrate concentration and hydrogen peroxide/substrate ratio. For a fixed initial concentration and hydrogen peroxide/substrate ratio, the conversion was found to be in the order catechol>chlorophenol>phenol. The temperature of the reaction medium was found to have a minimal effect on the degradation kinetics, probably due to simultaneous thermal decomposition of hydrogen peroxide at elevated temperature. A probable mechanistic explanation of the experimental data based on reactivity of the phenolic compounds and their stable oxygenated intermediates is discussed. © 1999 Society of Chemical Industry.