Reactions of Dissolved Pollutants with Ozone in Aqueous Solutions

摘要

This research was undertaken to investigate kinetics of liquid phase oxidation of selected hydrocarbons by ozone. Rate constants and orders of the ozonation reactions in aqueous solutions of pH values varying from 3 to 7 at 5 to 35C were determined utilizing the stopped-flow technique. Ozonation reactions of olefinic compounds including cyclohexene, cyclopentene and 1-pentene were much faster in aqueous solutions than in the vapor phase. The rate constants of the bimolecular reactions are of the order of 1,000,000l/mole sec or larger, and are nearly independent of the pH value and temperature. Experimental results indicate that saturated hydrocarbons such as cyclohexane, cylopentane, hexane and pentane were not reactive with dissolved ozone in solutions. Benzene and toluene reacted with ozone at moderate rates in acidic solutions but the ozonation of benzene was very rapid in neutral solutions yielding a first order rate constant of 12.2/sec at 25C. Orders of the ozonation of aromatic compounds changed with acidity indicating a possible shift in mechanisms of the reactions. Preliminary tests by the methods of chromatography showed that acids and aldehydes were formed in ozonation of the olefins and that oxidation of benzene produced benzoquinone and hydroquinone. Polymerization of the hydrocarbons might be indicated by detections of high molecular species in the solutions.