The kinetics of bromate decomposition during UV irradiation of aqueous solutions.
Item
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Title
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The kinetics of bromate decomposition during UV irradiation of aqueous solutions.
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Identifier
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AAI9908348
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identifier
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9908348
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Creator
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Phillip, Neal Hudson.
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Contributor
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Adviser: Vasil Diyamandoglu
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Date
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1998
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Environmental
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Abstract
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The kinetics of bromate decomposition during UV irradiation at 254 nm was studied in pure aqueous solutions, as well as in the presence of nitrite and acetate.;UV irradiation of bromate solution produced bromide as a final product and free bromine as reaction intermediate. A bromine balance during the experiments eliminated the possibility of formation of other bromine species in significant quantities. Experiments conducted at initial pH {dollar}<{dollar} 9.0, had pH decreases by as much as 1.5 pH units.;Bromate decay kinetics has been shown to be first order with respect to initial bromate molar concentration. Kinetic analysis of the data showed the observed bromate decay rate constant, {dollar}\rm k\sb{lcub}obs{rcub},{dollar} to be independent of initial bromate, initial pH, and bicarbonate alkalinity.;During UV irradiation of bromate/nitrite solution, bromate decomposition to bromide and free bromine proceeded faster than in bromate alone solutions. Nitrite was oxidized stoichiometrically to nitrate. The increased free bromine formation during UV irradiation of bromate/nitrite solution suggested that bromine intermediate species other than free bromine was principally responsible for nitrite oxidation. A marked decrease in the bromate decay was observed when nitrite became limiting, though the reduced rate was still about 50% higher than in corresponding bromate alone experiments. Bromate decay was shown to be pseudo-first order for bromate/nitrite ratios {dollar}{dollar}1 and to be independent of initial bromate, initial nitrite and initial pH.;In the presence of acetate, bromate was reduced to bromide while acetate was converted to unidentified product(s). Free bromine remained at trace levels throughout the experiments. A bromine balance for the experiments suggested the formation of organic by-products from the reaction of free bromine and acetate. Kinetic analysis showed bromate decay to be pseudo-first order and to be markedly increased by acetate.;A kinetic model to describe UV catalyzed bromate decomposition in bromate solution and bromate/nitrite solution was developed. For bromate alone, the model was in good qualitative agreement with the experimental data, except for bromate levels below 0.5 mg/L, while the predictions for bromate/nitrite system were in good agreement until nitrite became limiting. The bromate/acetate system was not modeled.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
