Decomposition rate of volatile organochlorines by ozone and utilization efficiency of ozone with ultraviolet radiation in a bubble-column contactor

Abstract

Decomposition of volatile chlorohydrocarbons in the gas and aqueous phases is tested in a thin, rectangular-channel reactor. In the absence of u.v. irradiation, destruction of pollutants in the gas phase hardly occurs, while there is a little in the aqueous phase. Ultraviolet irradiation accelerates the destruction of pollutants in both the gas and aqueous phases, and the destruction rate is proportional to the concentration of reactants and the u.v. intensity. To evaluate the effect of reactor configuration and operational conditions on the performance of the actual water treatment process, a bubble column equipped with a diffuse lamp along the central axis is adopted as a model reactor. The conversion of volatile chlorohydrocarbons and the ozone utilization efficiency are calculated by considering the mass transfer of ozone and pollutants between the gas and aqueous phases, and the self-decomposition of ozone and destruction rate of pollutants in each phase under u.v. irradiation. A simulation on the basis of the experimental data obtained predicts that excessive u.v. radiation decomposes ozone in the gas phase before it is transferred into the aqueous phase, causing a decrease in the utilization efficiency of ozone.