Date of Award

Fall 12-19-2018

Degree Type

Dissertation

Degree Name

PhD. Chemistry

Department

Chemistry and Biochemistry

Advisor

Sergiu M. Gorun, Ph.D.

Committee Member

Stephen P. Kelty, Ph.D.

Committee Member

Alexander Y. Fadeev, Ph.D.

Keywords

Phthalocyanine/SiO2; Phthalocyanine/TiO2; Phthalocyanine/NiO; Phthalocyanine/polymer membranes; F64PcZn; F64PcCu; Methyl orange; Rhodamine B

Abstract

Stabilized heterogeneous photocatalysts that use only solar light and air have been prepared and successfully employed to decontaminate water from organic pollutants. Organic dye pollutants present, for example in textile effluents, are one of the major sources of water pollution owing to their limited biodegradability, toxicity and potential carcinogenic risks. Before certifying water for public consumption, reuse in industries or for discharge in surface water the organic pollutants must be degraded, an effort that is energy intensive and currently requires complex methodologies. We report solid-state photocatalysts that use only visible light and air to treat wastewater. Perfluoroalkyl perfluoro-substituted zinc phthalocyanine F64PcZn, an efficient and stable photocatalyst, deposited on micrometer to nanometer size SiO2 and TiO2 particles and polymer membranes such as polytetrafluoroethylene, polyethersulfone and polypropylene has been shown to be active for the photodegradation of model organic pollutants such as methyl orange, rhodamine B and methyl red.

Our investigation suggests F64PcZn adsorbed on TiO2 through the interaction of central zinc atom and fluorine atoms of peripheral -CF3 group. Total organic carbon and total dissolved nitrogen in water decreased after photoreaction catalyzed by F64PcZn/SiO2 and F64PcZn/TiO2. The fragmentation of organic dye pollutants is confirmed by 1H-NMR, HPLC and LC-MS studies. Moreover, HPLC and LC-MS analyses suggest the adsorption of rhodamine B is different on bare TiO2 as compared to F64PcZn/TiO2 because of the difference in surface charges. Zeta potential measurements show that the surface of F64PcZn/TiO2 contains negative charges, thus positive group of dye pollutants readily interacts. Examination of the effect of F64PcZn loading amounts on SiO2 and TiO2 through fluorescence and UV-Vis-NIR spectral measurements indicate an optimum amount of F64PcZn needs to be deposited on SiO2 and TiO2 particles. Too much of F64PcZn deposition leads to either aggregation or decrease in fluorescence of hybrid photocatalyst.

The current study indicates that there is no orbital coupling between F64PcZn and the matrices SiO2 and TiO2. When F64PcZn is deposited on NiO, an orbital coupling is occured but, the photo reactivity is nullified. An electron transfer from NiO to F64PcZn deactivates the excited catalyst molecule rapidly before reacting with oxygen to produce singlet oxygen, 1O2.

F64PcZn/TiO2 is stable even under UV light irradiation as compared to commercial phthalocyanines such as H16PcZn/TiO2 and F16PcZn/TiO2. In addition, F64PcZn/TiO2 catalytic efficiency is higher than H16PcZn/TiO2 and F16PcZn/TiO2. F64PcZn/TiO2 can be used for several cycles without any loss in the catalyst efficiency. Hence, a stable as well as an efficient hybrid photo catalyst is synthesized to purify water using renewable resources.

Available for download on Saturday, December 19, 2020

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