KINETICS OF THE REACTION BETWEEN OZONE AND MCPA

The kinetics of the reaction between ozone and aqueous solutions of 4-chloro-2-methylphenoxyacetic acid (MCPA) has been investigated from gas absorption experiments in a semi-continuous reactor. They were conducted modifying the gas flow rate, agitation speed, ozone partial pressure, initial pesticide concentration, temperature and pH. The liquid mass transfer coefficient, the interfacial area and the stoichiometric ratio between ozone and MCPA were evaluated. A model based on the film theory was used to analyse the experimental data and to determine the rate constant and the kinetic regime. The results obtained support a second order overall reaction, the rate constants being well correlated by the expression: k = 9377 exp(-3276/RT) [OH-]0.008.