Abstract
Reaction rate constants of di-n-butyl phthalate (DBP) and 17β-estradiol (E2) with ozone and hydroxyl redical (HO·) were measured in water. The rate constants of DBP with ozone and HO· were <0.2 and 5.3X109 M-1·s-1, respectively (DBP-d4 was used for the measurement of the rate constant of DBP with HO·), thus, it was found that DBP was decomposed only by HO· during ozonation. Reaction rate constants of undissociated and dissociated forms of E2 with ozone were 7.1(±2.5)X104 and 1.3(±0.2)X109 M-1·s-1, respectively, and the reaction rate constant of the undissociated form of E2 with HO· was 5.3(±0.4)X109 M-1·s-1. The order of the apparent rate constants of E2 with ozone was from 105 to 107 M-1·s-1 in the case that the pH of the solution was in the range of 6-8. Therefore, it was shown that E2 reacted mainly with ozone molecules and was rapidly decomposed during practical ozonation. The relationship among the residuals of the compounds decomposed mainly by HO· during ozonation in the absence of co-existing substances was not affected by the dissolved organic matter (DOM) when the dissolved organic carbon (DOC) was less than several mg·l-1.
