Model Based on the Rate Equation and Experimental Data

1 Model Based on the Rate Equation and Experimental Data 

An experimentally determined reaction rate coefficient k can be used to calculate the OH° concentration from equation 5-3  

The reaction rate coefficient k can be determined from the experimental observation of the elimination of a model compound over time (Chapter B 4). It can be combined with literature values for kD and kR, and the experimentally determined ozone concentration to calculate the amount of OH-radicals which were present during the oxidation process. If indirect oxidation dominates, the term for the direct oxidation (kD c(03)ss) can be neglected. 

It is possible to use this OH° concentration to predict k for the oxidation of other compounds under the same conditions. Von Gunten et al. (1995) calculated the actual concentration of OH° using this general and easy way for the ozonation of surface water at neutral pH in a two-stage pilot plant. Atrazine was used as the model compound, ozone decay was assumed to be of first order and the reactors completely mixed. Based on this model they were able to precisely predict the formation of bromate (Br03 ) by oxidation of bromide (Br ) for a full-scale water treatment plant. Bromate is a disinfection byproduct (DBP) of the ozonation of bromide-containing waters, and of concern because of its carcinogenic effects in animal experiments (see also Chapter A 3). 

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