Date of Degree
PhD (Doctor of Philosophy)
Civil and Environmental Engineering
David M. Cwiertny
Gene F. Parkin
First Committee Member
Sarah C Larsen
Second Committee Member
Third Committee Member
Michelle M Scherer
Small drinking water systems, often financially and resource-limited, face unprecedented challenges due to the current diversity and ubiquity of water pollutants. Well-characterized inorganic legacy pollutants, including arsenic, copper, hexavalent chromium, and lead, remain persistent in drinking water systems. In addition, emerging organic contaminants, like endocrine disrupting compounds and pharmaceuticals, are largely uncharacterized but prevalent in the environment and water supplies, calling into question what levels of these relatively new contaminants are truly safe in drinking water. Point-of-use (POU) and point-of-entry (POE) water treatment devices, installed at a specific tap or at the water entry point to a single facility, respectively, are necessary to ensure safe drinking water in contexts where centralized water treatment is not available or cannot adapt to meet new regulatory standards. While existing POU and POE technologies, including reverse osmosis and packed bed media filters, are effective for removing contaminants, installation costs, energy demands, and spatial footprints of these systems can inhibit their implementation. There is a need for new POU and POE technologies that remove a diversity of water contaminants while maintaining a small application footprint. Nanotechnology, referring to technology using material with at least one dimension or feature less than 100 nm in length, is ideal for meeting this need in drinking water treatment. With high surface area-to-volume ratios, nano-enabled treatment technologies exhibit enhanced reactivity with less material, keeping overall footprint relatively small. Specifically, electrospinning, a process in which a polymer precursor solution is electrified to produce a cohesive sheet of nanofibers, can be used to easily synthesize chemically active nanofiber filters for water treatment applications. In this study, we develop electrospun nanofiber filters that harness nano-scaled hematite (Fe2O3) for sorption of inorganic contaminants (e.g., As, Pb) and nano-scaled titanium dioxide (TiO2) for use with ultraviolet (UV) and visible light as an advanced oxidation process (AOP) for removal of emerging organic contaminants (e.g., benzotriazole, carbamazepine, DEET). Most importantly, we strive to optimize both reactivity and material strength to develop cohesive, durable filtration platforms that overcome barriers to use of nanomaterials in water treatment (e.g., concerns over leaching of nanoparticles deployed as suspensions). Herein, we first demonstrate reactivity optimization of pure (though brittle) TiO2 nanofiber photocatalysts by noble metal catalyst (Au) surface loading. Additionally, we optimize polymer-Fe2O3 composite nanofibers for reactivity while maintaining material flexibility by coating the doped polymer with additional Fe2O3 surfaces available for metal/metalloid uptake. Finally, we apply reactivity optimization and strategies to maintain material strength in the development of carbon/TiO2 nanofiber composites used for (photo)chemical filtration of water containing emerging organic contaminants. Ultimately, we find that nanofiber composites exhibit substantial reactivity and structural integrity in water treatment platforms. Outcomes of this work contribute to making nanomaterials, which have been studied for decades but have yet to be commercially employed for water treatment, practical for chemically active water filtration.
A variety of pollutants, from a metals like lead and arsenic to the herbicide atrazine, challenge water quality across the United States. Point-of-use (POU) and point-of-entry (POE) water treatment devices, installed at a specific tap or at the water entry point to a single facility, respectively, can ensure safe drinking water when water treatment facilities are not available or cannot meet new regulatory standards. Nanomaterials, referring to materials with at least one dimension or feature less than 100 nm in length, are ideal for removing many water pollutants due to their high reactivity and small footprint. Specifically, electrospinning, a process in which a solution is electrified to produce a flexible sheet of nanofibers, can be used to easily make nanofiber filters for water treatment applications. In this study, we develop electrospun nanofiber filters that use the iron oxide hematite (Fe2O3) to remove metals (e.g., Pb) and titanium dioxide (TiO2) for use with ultraviolet (UV) to remove organic pollutants (e.g., herbicides, pharmaceuticals). Most importantly, we strive to balance both reactivity (efficiency at removing pollutants) and material strength (flexibility, durability) to develop resilient water filters that overcome barriers to use of nanomaterials in water treatment (e.g., concerns over release of nanomaterials into treated water). This work brings reactive nanomaterials, which have been studied for decades but have yet to be used for commercial water treatment, closer to actual application as water filters.
Electrospinning, Hematite, Nanofibers, Point of use, Titanium dioxide, Water treatment
xxii, 189 pages
Includes bibliographical references (pages 170-189).
Copyright © 2016 Katherine E. Greenstein
Greenstein, Katherine E.. "Development of chemically active metal oxide composite nanofiber filters for water treatment." PhD (Doctor of Philosophy) thesis, University of Iowa, 2016.