1990 Government Agencies Directory

ABSTRACT

The kinetics of pentachlorophenol (PCP) ozonation in terms of the gaseous O₃ and dissolved PCP concentrations has been investigated. When the O₃ concentration in the gas phase was in the range of 10 to 40 g O₃/m³, the O₃ dissolved for a short time period was proportional to the gaseous O₃ concentration. In this range, the ozonation reaction was first order for each reactant and the overall reaction was second order. At 25 °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 O₃ and PCP was an interface reaction on the surface of gaseous O₃ 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 O₃ and PCP molecules under the conditions investigated in this study, since O₃ has a high selectivity toward PCP. The reaction rate increased with the reaction temperature up to 35 °C but decreased at temperatures greater than 35 °C due to the decreased solubility of O₃. The addition of H₂O₂ did not increase the reaction rate significantly.