Modification of the standard neutral ozone decomposition model

The modified Staehelin, Buhler, and Hoigne model for aqueous ozone decomposition was tested over a wide range of hydroxyl radical scavenger concentrations at a pH of 7.1-7.2. Results from these experiments showed that the modified model appeared to underpredict the residual ozone concentration and overpredict the residual hydroxyl radical probe compound, tetrachloroethylene, concentration. The modified Staehelin, Buhler, and Hoigne model was recalibrated and two rate constants, the rate constant of the initiation reaction of ozone decomposition of hydroxide ion and the rate constant of the promotion reaction of ozone decomposition by hydroxyl radical, were reestimated. The new estimates of these rate constants are 1.8 X 10(2) M(-1)s(-1) (initiation reaction) and 2 x 10(8) M(-1)s(-1) (promotion reaction), while the values estimated by Staehelin, Buhler, and Hoigne for these rate constants are 70 M(-1)s(-1) (initiation reaction) and 2 x 10(9) M(-1)s(-1) (promotion reaction). The recalibrated-modified model was tested and validated by conducting experiments at different pH values and hydroxyl radical scavenger concentrations. Also, the effect of phosphate buffer as a hydroxyl radical scavenger was investigated at phosphate buffer concentrations of 10 mM and 1 mM.