Ozonation kinetics for the degradation of phthalate esters in water and the reduction of toxicity in the process of O ₃/H ₂O ₂

The oxidation kinetics of four phthalate esters (PAEs) with ozone alone and hydroxyl radical (OH) were investigated. The toxicity reduction in the process of O ₃/H ₂O ₂ was evaluated. The second order rate constants for the reaction of four PAEs with ozone and OH were determined by direct oxidation method and competition kinetics method in bench-scale experiment, and found to be 0.06-0.1M ^-1s ^-1 and (3-5)×10 ⁹M ^-1s ^-1, respectively. The oxidation kinetic rate constant of the selected PAEs (diethyl phthalate, DEP) was confirmed using Song Hua-jiang river water as the background. The results indicated that DEP degradation in this river water was close to the simulated value based on the determined rate constants. The toxicity test performed with bioluminescence test, showed that the toxicity expressed as the inhibition rate changed from 36% to below detection limit in the process of O ₃/H ₂O ₂, which means that catalytic ozonation is an efficient way for DEP degradation and toxicity reduction, but an ineffective method for DEP minimization on the basis of the total organic carbon determination.