A kinetic study on oxidation of pentachlorophenol by ozone

The kinetics of pentachlorophenol (PCP) ozonation in terms of the gaseous O-3 and dissolved PCP concentrations has been investigated. When the O-3 concentration in the gas phase was in the range of 10 to 40 g O-3/m(3), the O-3 dissolved for a short time period was proportional to the gaseous O-3 concentration. In this range, the ozonation reaction was first order for each reactant and the overall reaction was second order. At 25 degrees C, in an aqueous solution, the reaction rate constant was estimated to be 10.048 L/mol.sec. The reaction rate was much greater than the mass-transfer rate, indicating that the reaction of O-3 and PCP was an interface reaction on the surface of gaseous O-3 bubbles. The final product of the PCP ozonation was oxalic acid, with the carbon yield of the reaction being 59.4%. The ozonation of PCP in the aqueous solution was not a radical reaction but a direct reaction between O-3 and PCP molecules under the conditions investigated in this study, since O-3 has a high selectivity toward PCP. The reaction rate increased with the reaction temperature up to 35 degrees C but decreased at temperatures greater than 35 degrees C due to the decreased solubility of O-3. The addition of H2O2 did not increase the reaction rate significantly.