Browsing by Author "Javed, Hassan"

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    Bi-Polymer Electrospun Nanofibers Embedding Ag3PO4/P25 Composite for Efficient Photocatalytic Degradation and Anti-Microbial Activity
    (MDPI, 2020) Habib, Zunaira; Lee, Chang-Gu; Li, Qilin; Khan, Sher Jamal; Ahmad, Nasir Mahmood; Jamal, Yousuf; Huang, Xiaochuan; Javed, Hassan; NSF Nanosystem Engineering Research Center for Nanotechnology Enabled Water Treatment
    Using a bi-polymer system comprising of transparent poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) (PVP), a visible light active Ag3PO4/P25 composite was immobilized into the mats of polymeric electrospun nanofibers. After nanofibers synthesis, sacrificial PVP was removed, leaving behind rough surface nanofibers with easy access to Ag3PO4/P25 composite. The remarkable photocatalytic efficiency was attained using a PMMA and Ag3PO4/P25 weight ratio of 1:0.6. Methyl orange (MO) was used to visualize pollutant removal and exhibited stable removal kinetics up to five consecutive cycles under simulated daylight. Also, these polymeric nanofibers (NFs) revealed an important role in the destruction of microorganisms (E. coli), signifying their potential in water purification. A thin film fibrous mat was also used in a small bench scale plug flow reactor (PFR) for polishing of synthetic secondary effluent and the effects of inorganic salts were studied upon photocatalytic degradation in terms of total organic carbon (TOC) and turbidity removal. Lower flow rate (5 mL/h) resulted in maximum TOC and turbidity removal rates of 86% and 50%, respectively. Accordingly, effective Ag3PO4/P25 immobilization into an ideal support material and selectivity towards target pollutants could both enhance the efficiency of photocatalytic process under solar radiations without massive energy input.
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    Mechanistic insights on the merits and limitations of advanced treatment processes for removal of contaminants of emerging concern
    (2020-08-10) Javed, Hassan; Alvarez, Pedro J. J.
    Perfluoroalkyl substances (PFASs) are recalcitrant contaminants of emerging concern that have widespread distribution in water sources, and exhibit potential to persist and bioaccumulate. Non-destructive and destructive remediation strategies have been actively investigated to remove PFAS. Adsorption on activated carbon is the most widely used non-destructive treatment method to remove PFAS. However, limited innovation has occurred in the field of activated carbon materials and there is a need to develop ultra-high surface area activated materials that exhibit high adsorption capacity and selectivity for target contaminants. Furthermore, non-destructive methods only transfer the contamination from one phase to another and therefore must be used in conjunction with destructive treatment methods to effectively remove and mineralize the target contaminant. In recent years, there has been growing interest to use Advanced Oxidation Processes (AOPs) to degrade PFAS. However, progress in the field has been hampered by the ambiguity that exists regarding the role of two key reactive oxygen species (ROS) i.e. hydroxyl radical (•OH) and superoxide radical anion (O2•-) in degrading PFAS with some studies demonstrating their effectiveness while others claiming the contrary. This dissertation aims to provide mechanistic insights into the treatment of PFAS and other contaminants of emerging concern by: i) Developing fundamental understanding of how the structure of a novel ultra-high surface area activated carbon relates to its function as an adsorbent. ii) Resolving the ambiguity regarding the role of •OH and O2•- in degrading PFAS.