Kinetics of Bromacil Ozonolysis

Chemical oxidation processes have been used successfully in the degradation of organic pollutants, yet information is limited concerning the kinetic descriptions of the reaction mechanisms. In this study, the kinetics of bromacil (5-bromo-3-sec-butyl-6-methyluracil, a herbicide) ozonolysis was examined. From laboratory observations, a mechanism was proposed by which direct ozone attack occurred and the degradation pathway proceeded via two parallel reactions. The program MLAB was used to provide a numerical solution for the system of differential equations that described the mechanism. Rate parameters were determined using the slowest reaction system (H2O2/O3). The kinetic model was then tested on a system with only bromacil and on a system containing a radical scavenger. This mathematical model is reasonably consistent with the experimental observations that the addition of hydrogen peroxide significantly reduces the formation of the byproduct responsible for the residual phytotoxicity of the waste stream. Keywords: Bromacil; ozonolysis; ozonation; kinetics; wastewater treatment; modeling