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Modeling reactions of ozone with natural organic matter
This study was directed at developing a predictive kinetic model for ozone consumption by natural organic matter (NOM). The objectives of this research were: (1) to test an existing model, the Staehelin and Hoigne model, for aqueous ozone decomposition in a batch reactor, (2) to develop and test a model for determining the rate of change of aqueous ozone concentration during the ozonation of a simple organic model compound in a batch reactor, and (3) to develop and calibrate a kinetic model for determining the rate of loss of aqueous ozone and a hydroxyl radical probe compound during the ozonation of NOM in batch reactors.^ In the first stage of laboratory work, experiments were conducted to test the Staehelin and Hoigne model for aqueous ozone decomposition. Two of the rate constants of the Staehelin and Hoigne model were re-estimated in order to improve the agreement between the model predictions and the observed data at neutral pH and under several hydroxyl radical scavenger concentrations.^ In the second stage of laboratory work, batch ozonation experiments were conducted with the model compound, formic acid. The Staehelin and Hoigne model for ozone decomposition was incorporated in the model development.^ Natural organic matter, extracted from Forge Pond (Granby, MA) and separated into eight fractions, was ozonated in a batch reactor in the final stage of laboratory experiments. The Staehelin and Hoigne model was included in the model for ozone consumption by NOM. The concentrations of two types of ozone-consuming sites and associated rate constants were estimated for each fraction. The rate constants for all fractions were utilized in estimating average rate constants, which were then used to re-estimate the site concentrations of each fraction. These new estimates of site concentrations were employed in computing composite ozone-consuming-site concentrations for Forge Pond water.^ It was found that a two-parameter model was quite successful at describing both the residual ozone concentration profiles and the hydroxyl radical profiles (via the probe compound). This firmly established the framework for a central chemical kinetic model that can be used to predict the impact of ozone on micropollutants in waters containing NOM. ^
Chemistry, Analytical|Engineering, Environmental
Boijayanta Kumar Bezbarua,
"Modeling reactions of ozone with natural organic matter"
(January 1, 1997).
Electronic Doctoral Dissertations for UMass Amherst.