Title page for ETD etd-04172009-132140


Type of Document Dissertation
Author Fiss, Edward Matthew
URN etd-04172009-132140
Title The Chlorination of Pharmaceuticals and Other Phenolic Compounds in the Presence of Iodide
Degree PhD
Department Environmental Engineering
Advisory Committee
Advisor Name Title
Vikesland, Peter J. Committee Chair
Dietrich, Andrea M. Committee Member
Edwards, Marc A. Committee Member
Little, John C. Committee Member
Tanko, James M. Committee Member
Keywords
  • free chlorine
  • iodide
  • PPCPs
  • drinking water
  • halogenation
Date of Defense 2009-04-01
Availability restricted
Abstract
Pharmaceuticals and personal care products (PPCPs) include a wide range of chemicals such

as prescription and over‐the‐counter drugs, fragrances, diagnostic agents, and a litany of other

compounds commonly added to household products such as sunscreens, soaps, toothpastes,

and deodorants. If present in natural waters, PPCPs can come into contact with disinfectants

during drinking water treatment processes. PPCPs are already known to form a variety of

disinfection byproducts (DBPs) when oxidized by free chlorine, including trihalomethanes

(THMs) and haloacetic acids (HAAs), many of which are known carcinogens.

Salts, such as iodide, are also often present in natural water systems. Iodide is known to form

a much more reactive oxidant, free iodine, when it reacts with free chlorine. Free iodine can

react with organic compounds in waters to form iodinated byproducts, many of which have

been shown to form in higher yields and to be more toxic than their chlorinated analogues. For

this reason, it is necessary to more fully understand the fate of PPCPs during drinking water

processes. The overall goals of this study are to 1) elucidate reaction mechanisms and product

formation potentials for PPCP oxidation by free chlorine in the presence of iodide and 2)

develop a computer model that can act as a predictive tool to aid in the assessment of potential

risks resulting from PPCPs in source waters.

Through the course of this research, a model was developed that could fit reaction rate

parameters and accurately predict solution reactivity for a range of substituted phenols as well

as PPCPs including bisphenol‐A and triclosan. Past studies utilizing pseudo‐first‐order rate

constants to determine a reaction rate over‐simplified the analysis of halogen substitution

reactions. Free chlorine reaction rate constant values were updated from the literature since

the mechanism for electrophilic substitution was found to be different than stated in currently

published literature. The involvement of H2OCl+ was found to be negligible. The mechanism for

the electrophilic substitution of phenolic compounds by free iodide was also different from

current literature findings. We found that I2, rather than H2OI+, was an extremely important

species for free iodine reactions and must be considered when analyzing the reaction kinetics.

Finally, we found that small amounts of iodide can significantly affect product formation

pathways thereby causing preferential formation of iodinated products and a potential increase

in the total product formation.

In general, the reaction kinetics were highly dependent upon the pH, iodide to free chlorine

ratio, and the reactivity of the phenolic compound, and our model was able to successfully

address changes in each of these variables. An LFER was developed that showed a linear

relationship between reaction rates and the pKa of a phenolic compound. It is believed that the

model developed can be used as a predictive tool to estimate reactivity of natural waters for a

range of phenolic PPCPs simply by using the compounds pKa.

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