Date of Award
2024
Document Type
Open Access Dissertation
Degree Name
Doctor of Philosophy in Environmental Engineering (PhD)
Administrative Home Department
Department of Materials Science and Engineering
Advisor 1
Yun Hang Hu
Committee Member 1
Ranjit Pati
Committee Member 2
Patricia A. Heiden
Committee Member 3
Daisuke Minakata
Abstract
As environmental pollution from industrial processes and human activities continues to rise, finding efficient approaches to recycle waste materials and degrade persistent contaminants becomes increasingly critical. Dead leaves, an abundant but underutilized biomass, present an opportunity for creating value-added materials if their biocomponents can be preserved and transformed. Simultaneously, antibiotics such as tetracycline are widely found in water bodies but pose serious ecological and health risks, necessitating effective degradation methods. This dissertation addresses these challenges by leveraging natural and nanostructured materials to develop multifunctional products and advanced photocatalytic processes.
Chapter 3 of this dissertation addresses the challenge of converting waste leaves into useful materials while preserving their biocomponents. By utilizing whewellite biomineral to bind lignin and cellulose, red maple dead leaves were transformed into an active multifunctional material. This material exhibits intense optical absorption and possesses a heterogeneous architecture that enhances charge separation. It excels in solar water evaporation, photocatalytic hydrogen production, and tetracycline degradation. Moreover, it serves as a bioplastic with superior mechanical strength, high-temperature tolerance, and biodegradability.
Chapters 4 and 5 explore visible-light driven photocatalytic processes using green, cost-effective, nanostructured photocatalysts. In Chapter 4, zinc oxide (ZnO), typically inactive under visible light due to its large band gap (3.2 eV), was activated through tetracycline's multiple self-promotion effects. Tetracycline adjusts ZnO's energy band, photo-sensitizes it, and enhances charge transfer, achieving a remarkable degradation efficiency of 91.1%. The study also employed realistic water matrices, identified active species and degradation products, and evaluated acute and developmental toxicities.
Chapter 5 presents an efficient visible-light driven thermo-photo catalytic process for tetracycline degradation using tungsten disulfide (WS2) nanoflakes. Despite WS2's broad light absorption with a small band gap of 1.4 eV, its practical efficiency was hampered by inadequate generation of reactive oxygen species. By harnessing in-situ generated heat under illumination, this method achieved an impressive 87.4% tetracycline degradation efficiency, outperforming individual thermal catalysis and photocatalysis. Moreover, the process promoted tetracycline mineralization and significantly mitigated toxicities in the resulting degradation products.
Overall, this dissertation demonstrates innovative strategies for valorizing waste biomass and advancing photocatalytic processes for environmental remediation, providing sustainable solutions to pressing global challenges.
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Recommended Citation
Fang, Siyuan, "Sustainable Materials for Environment − Multifunctional Material Made from Dead Leaves and Nanostructured Materials for Antibiotic Degradation", Open Access Dissertation, Michigan Technological University, 2024.
Included in
Catalysis and Reaction Engineering Commons, Environmental Engineering Commons, Polymer and Organic Materials Commons