In the present study, the decomposition rates of carbon tetrachloride （CC14） and 2,4-dichlorophenol （2,4- DCP） in water by the ultraviolet （UV） light irradiation alone and H2O2AYV were experimentally investigate...In the present study, the decomposition rates of carbon tetrachloride （CC14） and 2,4-dichlorophenol （2,4- DCP） in water by the ultraviolet （UV） light irradiation alone and H2O2AYV were experimentally investigated. The detailed experimental studies have been conducted for examining treatment capacities of the two different ultraviolet light sources （low and medium pressure Hg arc） in H2O2/UV processes. The low or medium UV lamp alone resulted in a 60%-90% decomposition of 2,4-DCP while a slight addition of H2O2 resulted in a drastic enhancement of the 2,4-DCP decomposition rate. The decomposition rate of 2,4-DCP with the medium pressure UV lamp alone was about 3-6 times greater than the low pressure UV lamp alone. In the direct photolysis of aqueous CC14, the medium pressure UV lamp had advantage over the low pressure UV lamp because the molar extinction coefficient of CC14 at shorter wavelength （210-220 nm） is about 20 to 50 times higher than that at 254 nm. However, adding H202 to the medium pressure UV lamp system rendered a negative oxidation rate because H202 acted as a UV absorber being competitive with CC14 due to negligible reaction between CC14 and OH radicals. The results fi：om the present study indicated significant influence of the photochemical properties of the target contaminants on the photochemical treatment characteristics for designing cost-effective UV-based degradation of toxic contaminants.展开更多
文摘In the present study, the decomposition rates of carbon tetrachloride （CC14） and 2,4-dichlorophenol （2,4- DCP） in water by the ultraviolet （UV） light irradiation alone and H2O2AYV were experimentally investigated. The detailed experimental studies have been conducted for examining treatment capacities of the two different ultraviolet light sources （low and medium pressure Hg arc） in H2O2/UV processes. The low or medium UV lamp alone resulted in a 60%-90% decomposition of 2,4-DCP while a slight addition of H2O2 resulted in a drastic enhancement of the 2,4-DCP decomposition rate. The decomposition rate of 2,4-DCP with the medium pressure UV lamp alone was about 3-6 times greater than the low pressure UV lamp alone. In the direct photolysis of aqueous CC14, the medium pressure UV lamp had advantage over the low pressure UV lamp because the molar extinction coefficient of CC14 at shorter wavelength （210-220 nm） is about 20 to 50 times higher than that at 254 nm. However, adding H202 to the medium pressure UV lamp system rendered a negative oxidation rate because H202 acted as a UV absorber being competitive with CC14 due to negligible reaction between CC14 and OH radicals. The results fi：om the present study indicated significant influence of the photochemical properties of the target contaminants on the photochemical treatment characteristics for designing cost-effective UV-based degradation of toxic contaminants.
