Graduate Thesis Or Dissertation

 

Optimizing Photo-Initiated Oxidation by the Spectral Diversity of Novel UV Sources Public Deposited

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https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/m326m316g
Abstract
  • UV advanced oxidation processes are a well-developed, sustainable technology which utilize UV energy to degrade organic contaminants in water. Novel UV sources, which do not contain mercury, provide the opportunity for enhancement of current oxidation technologies through spectral exploitation, minimizing inefficiencies that currently limit conventional technology. Wastewater reuse is the main full-scale application of UV AOPs in practice but the background absorbance of wastewater-influenced waters and low molar absorption by conventional radical promoters (hydrogen peroxide) have historically limited their system efficiency, resulting in the underutilization of photons in a reactor. 

    This thesis compares conventional and novel UV sources on a spectral basis and examines the mechanisms by which photons promote the production of hydroxyl radicals from various radical promoters. Bench-scale research then evaluates longer wavelength UV light emitting diodes (265, 280, and 300 nm) in increasing average rates of photon absorption and optimizing the utilization of photons for advanced oxidation. Free chlorine, a common disinfectant and popular radical promoter, has a varying molar absorption profile dependent on pH, with large absorptions bands in the 280-300 nm range in basic waters which are common in carbon-based reuse. pH- and wavelength-dependent reaction rate constants were experimentally derived using Nitrobenzene and Benzoic acid as probe compounds and evaluated to determine the contribution of the hydroxyl and chlorine radical. Reclaimed water taken from various advanced treatment steps was treated with the UV LED AOP to investigate how background absorbance affects radical generation and contaminant transformation kinetics. In addition, alternative performance metrics to evaluate hydroxyl radical production at different incident fluence rates and different rates of photon absorption at a specified wavelength for varying background UV absorbance were assessed. Finally, it will increase the acceptance of alternative UV sources in advanced oxidation processes, like LEDs, which can be utilized to treat organic chemical contaminants and increase overall system efficiency.

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  • 2022-11-29
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  • 2024-01-18
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