Oxidation of pharmaceuticals during water treatment with chlorine dioxide

摘要

The potential of chlorine dioxide (ClO_2) for the oxidation of pharmaceuticals during water treatment was assessed by determining second-order rate constants for the reaction with selected environmentally relevant pharmaceuticals. Out of 9 pharmaceuticals only the 4 following compounds showed an appreciable reactivity with ClO_2 (in brackets apparent second-order rate constants at pH 7 and T = 20℃): the sulfonamide antibiotic sulfamethoxazole (6.7 x 10~3 M~(-1) s~(-1)), the macrolide antibiotic roxithromycin (2.2 x 10~2 M~(-1) s~(-1)), the estrogen 17α-ethinylestradiol (～2 x 10~5 M~(-1) s~(-1)), and the antiphlogistic diclofenac (1.05 x 10~4 M~(-1) s~(-1)). Experiments performed using natural water showed that ClO_2 also reacted fast with other sulfonamides and macrolides, the natural hormones estrone and 17β-estradiol as well as 3 pyrazolone derivatives (phenazone, propylphenazone, and dimethylaminophenazone). However, many compounds in the study were ClO_2 refractive. Experiments with lake water and groundwater that were partly performed at microgram/L to nanogram/L levels proved that the rate constants determined in pure water could be applied to predict the oxidation of pharmaceuticals in natural waters. Compared to ozone, ClO_2 reacted more slowly and with fewer compounds. However, it reacted faster with the investigated compounds than chlorine. Overall, the results indicate that ClO_2 will only be effective to oxidize certain compound classes such as the investigated classes of sulfonamide and macrolide antibiotics, and estrogens.