Electronic Theses, Dissertations, and Records of Study (2002– )

Permanent URI for this collection

http://hdl.handle.net/1969.1/2

Description

This collection contains Texas A&M University theses and dissertations written after 2002.

History

In 2002, the Texas A&M University’s Office of Graduate and Professional Studies (OGAPS) began accepting electronic submission of theses and dissertations. In 2004, electronic submission became a requirement, and OGAPS now also accepts electronically submitted records of study.

Access

Most theses and dissertations in this collection are open access. However, Texas A&M University students have a right to place their work under embargo in certain circumstances. The full-text of theses and dissertations under embargo is restricted until the embargo period has expired.

Website: Thesis and Dissertation Services

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Browsing Electronic Theses, Dissertations, and Records of Study (2002– ) by Author "Abada, Bilal Saad Azeez"

Now showing 1 - 2 of 2
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    Degradation of Poly- and Per-fluoroalkyl Substances (PFASs) Using Photocatalyst Zinc Oxide
    (2016-11-30) Abada, Bilal Saad Azeez; Chu, Kung-Hui; Banerjee, Sarbajit; Batchelor, Bill; Jayaraman, Arul
    Poly- and per-fluoroalkyl substances (PFASs) in the environment have raised a great public health concern because these compounds are persistent, bioaccumulative and toxic. Degradation of polyfluoroalkyl substances like fluorotelomer alcohols (FTOHs) can produce perfluoroalkyl acids (PFAAs). Previous studies have reported biodegradation of 6:2 FTOH by several FTOH-degrading bacteria to various shorter-chain PFASs. Some transition metals, like zinc oxide (ZnO), have some interesting semiconducting, adsorbing and optical properties in addition to their ability to photocatalyticly degrade contaminants. Accordingly, we hypothesized that an approach that combines biological and chemical treatment will be an effective way to degrade PFASs. This study focused on photodegradation of PFASs using ZnO under environmentally friendly conditions, particularly near neutral pH and room temperature. Two types of ZnO were used: the commercial microscale ZnO and the tetrapod nanoscale ZnO. Results showed that photo-defluorination efficiency for 5:3 polyfluorinated acid was about 14.9% and 13.8% using commercial and tetrapod ZnO, respectively. Either type of ZnO could not successfully degrade any of the three PFAAs used in this study, i.e. PFOA, perfluorohexanoic acid (PFHxA) and perfluorobutyric acid (PFBA). Adding persulfate with tetrapod ZnO improved the defluorination efficiency for PFOA, but it reduced the defluorination of 5:3 acid and 6:2 FTOH. High doses of persulfate (27 mM) without ZnO led to a significant improvement in defluorination of PFOA, PFHxA and PFBA, with PFBA defluorination as high as about 40%. Defluorination of 5:3 acid by ZnO was eliminated when the experiments took place in a growth medium. The competition of these ions with PFASs for adsorption and the high ionic strength were proposed as possible reasons for this elimination. 5:3 Acid defluorination was not much affected by the presence of PFOA in the solution, which indicates that PFOA does not adsorb strongly enough on ZnO to inhibit adsorption of the 5:3 acid. Finally, solutions of the 5:3 acid that had undergone photodegradation with tetrapod ZnO were further examined for their treatability by biological processes. Biodegradation trials using P. flurescens DSM 8341 did not show a significant defluorination improvement, which in part due to the presence of growth medium. This is the first report studying the photodegradation of PFASs using ZnO.
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    Municipal and Industrial Wastewater Treatment via Reverse Osmosis, Electrocoagulation, and Dissolved Air Flotation
    (2022-06-28) Abada, Bilal Saad Azeez; Chellam, Shankararaman; Elabd, Yossef; Kaihatu, James; Sukhishvili, Svetlana
    This dissertation reports mechanistic investigations of selected technologies employed for physicochemical treatment and reuse of industrial and municipal wastewater. The first part investigates simultaneous biological, colloidal, organic, and inorganic fouling of reverse osmosis (RO) membranes harvested from the world’s largest potable water reuse facility (Orange County Water District, California). This research was based on the hypothesis that combined fouling worsens RO performance and shortens membranes’ lifespan at full-scale. Detailed surface characterization of several end-of-life RO elements from each of the three stages of the full-scale plant revealed copious amounts of biocolloidal, organic, siliceous, and non-siliceous foulants on all membranes but to different extents. Bioorganic foulants dominated the first and second stages whereas inorganic (mainly silicon-related) foulants were more abundant in the third stage resisting chemical cleaning. Presence of organic silica (siloxanes) on membranes was reported for the first time. Difficulties in chemically removing bioorganic foulants were attributed to their adhesion to membrane surfaces via bridging through multivalent calcium, magnesium, and aluminum ions. This work provided the first detailed look into differences in the accumulation of various foulant classes on each element, combined fouling impacts on lead and lag elements of all three stages, as well as fouling impacts on physicochemical characteristics of membrane surfaces and its (ir)reversibility during chemical cleaning. Outcomes revealed that siliceous foulants were the main contributors to membranes’ end-of-life. Hence, silicon control is recommended to extend membrane lifetime during municipal wastewater reclamation and potable reuse. The second part of the research evaluated three processes for treatment of saline wastewaters: namely electrocoagulation, dissolved air flotation, and sedimentation. Temperature and natural organic matter effects on pitting corrosion and coagulant speciation during aluminum electrocoagulation were evaluated. Results suggested the need for pH adjustment at low temperatures to limit aluminum solubility under enhanced coagulation conditions. Finally, sedimentation and dissolved air flotation were compared to purify turbid and hypersaline produced water generated during unconventional oil and gas exploration and production. A combination of pre-hydrolyzed (aluminum chlorohydrate) and polyacrylamide coagulants were used to develop ultrahigh rate gravity liquid-solid separation processes to generate “clean brine” with total residence times of only 5-6 minutes.