Decomposition of phenols in aqueous solution by a UV/O-3 process

The decomposition of several non-biodegradable phenols by the UV/O-3 and ozonation processes was studied and compared under various solution pH values, O-3 input mass flow rates and UV intensities to investigate the removal efficiencies of reactants and organic intermediates. The decomposition rate of phenols by the UV/O-3 process was found to increase with increasing O-3 input dosage, light intensity and solution pH value. The mineralization efficiencies of phenols in aqueous solution would be above 98% under adequate reaction conditions within three hours, but would be retarded for alkaline solutions because of the dissolution of CO2 formed by mineralization of phenols. The increment of ozone input dosage had little effect on the mineralization of organic intermediates at the latter course of the reaction. The order of the decomposition rate of the phenols used in this research was 2,4-dichlorophenol > 2-chlorophenol > 2-nitrophenol for low and neutral pH solutions, whereas they were nearly alike for alkaline solutions. The two-step consecutive kinetic model was found to fit well in modeling the behavior of species during the decomposition of phenols in aqueous solutions by the UV/O-3 process.