Advanced oxidation processes of problematic toxin and water contaminants: Cylindrospermopsin, iopamidol, 4-methyl cyclohexane methanol and propylene glycol phenyl ether

Cen Zhao, Florida International University

Abstract

The occurrences of cyanotoxin and organic contaminants threaten drinking water sources and are a serious human health and environmental concern. The control of these problematic contaminants and the remediation of the associated contaminants are critical for ensuring safe drinking water to significant populations. Advanced oxidation processes (AOPs) have received considerable attention as a potential water treatment for various pollutants. In this dissertation, advanced oxidative degradation of four problematic water toxic contaminants (CYN, iopamidol, 4-methylcyclohexane methanol and propylene glycol phenyl ether) were studied to develop the fundamental understanding required to assess AOPs as a potential water treatment process. ^ UV and visible light activated (VLA) TiO2 photocatalysis using nitrogen and fluorine-TiO2 (NF-TiO2), phosphorus and fluorine-TiO2 (PF-TiO2) and sulfur-TiO2 (S-TiO 2) were employed for degradation of 6-hydroxymethyl uracil (6-HOMU), a model compound for the potent cyanotoxin cylindrospermopsin (CYN). NF-TiO 2 exhibits the most photoactive, followed by marginally active PF-TiO 2 and inactive S-TiO2 under visible light irradiation. Our results indicate that O2-• plays an important role in VLA TiO2 photocatalysis.^ Fe (VI), an environmentally friendly oxidant, was employed for the degradation of CYN and 6-HOMU over a range of pH (7 ~ 9.5). The second order rate constants for the reaction of Fe (VI) with CYN decrease from 38.83 ± 0.07 M -1s-1 at pH 7 to 5.02 ± 0.04 M -1s-1 at pH 9.5. ^ Fe (VI) mediated reactions primarily occur via oxidation of the uracil ring in CYN. ELISA results demonstrate that Fe (VI) oxidation process leads to a significant decrease in the bioactivity of CYN as a function of treatment time. Fe (III)-oxalate/H2O2 process was employed for the remediation of iopamidol, a model for ICM, to determine the formation rates and steady concentrations of •OH and O2-• under UV and visible light irradiation. Reduction by CO2 -• and oxidation by •OH contribute to the degradation pathways. ^ Pulse and gamma radiolysis of 4-methylcyclohexane methanol (MCHM) and propylene glycol phenyl ether (PPh) were studied to determine the bimolecular rate constants and reaction pathways. •OH addition to ortho and para positions in PPh are the predominant reaction pathways; H-abstraction are the primary reaction mechanisms for •OH mediated oxidation of MCHM^

Subject Area

Environmental studies|Analytical chemistry|Organic chemistry

Recommended Citation

Zhao, Cen, "Advanced oxidation processes of problematic toxin and water contaminants: Cylindrospermopsin, iopamidol, 4-methyl cyclohexane methanol and propylene glycol phenyl ether" (2015). ProQuest ETD Collection for FIU. AAI10002912.
http://digitalcommons.fiu.edu/dissertations/AAI10002912

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