Chemical Oxidation Processes in Aquatic Systems,Oxidation of Cumene,Pyridine,and p-Cresol,

摘要

A variety of observations point to the role of free-radical oxidation as an important process for transformation of selected organic chemicals in aquatic systems. This study was carried out to provide experimental evidence for the presence of free radicals such as alkylperoxy (RO2) and hydroxyl (HO) in natural waters photolyzed in sunlight and to calculate the average concentrations of these radicals. The kinetics and products of oxidation of dilute solutions (approximately 0.0001 M) of cumene (CuH) and pyridine by RO2and HO radicals in pure water were studied to establish the kinetic parameters needed to model these processes and to evaluate the concentrations of radicals formed in natural waters exposed to sunlight. Oxidation of p-cresol (PC) in pure water by RO2radical was studied in detail. The principal products are formed by coupling of RO2and MePhO radicals and by self-reaction of two MePhO radicals. The kinetic behavior of PC over a thousand-fold change in its concentration indicates that the rate constant for reaction of PC with RO2radical is very high,possibly 1,000,000/M/s and also indicates that cage recombination of R radicals from an azo-initiator is substantially higher in water than in organic solvents.