Dissertation
Fabrication of electrospun fibers for exposure control to airborne and drinking water contaminants
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2022
DOI: 10.25820/etd.006791
Abstract
Many public health challenges are connected to at least one of two exposure pathways: water and air. In these instances, filter materials—such as reverse osmosis membranes for water treatment, facemasks, or HEPA filters—are relied upon for exposure control. Electrospinning, a fabrication technique for nanofiber-based materials, has the potential to rapidly develop new, high-performance filter materials for specialized applications in public health protection in response to emerging threats. Two such public health challenges have recently emerged in which electrospinning could play a key role in developing effective solutions for exposure control: shortages of N95 Filtering Facepiece Respirator (N95 FFR) during the COVID-19 pandemic and the widespread contamination of drinking water supplies by per- and poly-fluoroalkyl substances or PFAS.
Under the context of these two public health challenges, this work collectively demonstrates the versatility of electrospinning while providing simple, practical electrospun filter materials to address prominent airborne and drinking water risks. The studies reported here focus on fabrication efforts emphasizing: (i) simplicity (for ease of rapid production); (ii) tunability (to adapt to emerging societal needs); and (iii) scalability (to facilitate translation from the laboratory to industrial scale fabrication).
First in this work, an unsupported, nonwoven layer of uncharged polystyrene (PS) microfibers was produced via electrospinning that achieves N95 performance standards [e.g., high filtration efficiencies (≥97.5%) and low pressure drops (≤15 mm H2O)] based on physical parameters (e.g., filter thickness) alone. The PS microfiber filter demonstrates durability in its maintenance of high filtration efficiencies and low pressure drops over six rounds of disinfection. Additionally, the PS microfibers can be modified readily through integration of silver nanoparticles (AgNPs) during electrospinning to enhance their antimicrobial activity (≥ 3-log removal at 25wt% AgNP integration).
Electrospinning was used next to develop polystyrene (PS) nanofibers with embedded biocidal agents that exhibit performance meeting or exceeding that of meltblown filtration layers currently used in N95 FFRs. Three antimicrobial agents—tetrabutylammonium bromide (TBAB; a quaternary ammonium surfactant) and two sizes of silver (Ag) nanoparticles (35 nm and 80 nm)— were integrated both individually and as mixtures (i.e., TBAB + 35 Ag) into PS nanofibers at 0.006-5 wt% loadings, and demonstrated high biocidal activity against E. coli (8-log removal). The 0.5 wt% antimicrobial PS materials were developed into thin supported layers (tens of microns thick), which achieved high particle filtration efficiencies (≥ 98%) and low pressure drops (≤ 12 mmH2O). Because of their tunable filtration performance, both the PS microfibers and these supported PS nanofiber layers represent feasible filter alternatives for use in N95 FFRs.
Finally, this study produced via electrospinning PAN nanofiber membranes functionalized with TBAB and nonfunctionalized multiwalled carbon nanotubes (CNTs) for the removal of PFAS contaminants from drinking water. These membranes exhibited relatively fast uptake of PFAS (both long-chain PFOA and PFOS, and short-chain PFBS and HFBA). The primary mechanism for PFAS sorption was determined to be anion exchange at the embedded quaternary amine sites provided by TBAB integration, while CNTs appeared to hinder PFAS uptake via electrostatic repulsion due to their negatively charged surface across environmentally relevant pH values. However, both membranes exhibited good adsorption capacities for PFAS (32 ± 5 mg PFOS/g and 28 ± 8 mg HFBA/g for TBAB/PAN; 22 ± 4 mg PFOS/g and 19 ± 6 mg HFBA/g for CNT/TBAB/PAN). Additionally, the synthesis of these membranes was translated from a single-needle, laboratory scale system to an industrial scale, needleless electrospinning system, resulting large-scale membranes that exhibited comparable PFAS removal to the bench-scale membranes.
Ultimately, novelty in this work is derived from the high-performance of the materials to meet the needs of emerging public health challenges, as well as the simple fabrication methodologies developed for robust fabrication at both laboratory bench-top and industrial scales.
Details
- Title: Subtitle
- Fabrication of electrospun fibers for exposure control to airborne and drinking water contaminants
- Creators
- Madeline Grace Jensen
- Contributors
- David M. Cwiertny (Advisor)Keri C. Hornbuckle (Committee Member)Syed Mubeen (Committee Member)Patrick O’Shaughnessy (Committee Member)Scott Shaw (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Civil and Environmental Engineering
- Date degree season
- Autumn 2022
- DOI
- 10.25820/etd.006791
- Publisher
- University of Iowa
- Number of pages
- xxvi, 294 pages
- Copyright
- Copyright 2022 Madeline Grace Jensen
- Language
- English
- Description illustrations
- Illustrations, charts, graphs, tables
- Description bibliographic
- Includes bibliographical references (pages 236-294).
- Public Abstract (ETD)
Electrospinning is a method which creates non-woven materials made up of small (micro- or nanometer) fibers. In this work, electrospinning is used to create filter materials to help fix two public health crises: PFAS (per- and polyfluoroalkyl substances) pollution in drinking water and the shortage of medical face masks during the COVID-19 pandemic. The large need for medical face masks during the COVID-19 pandemic started a search for new filter materials that could be made quickly but still meet filtration and breathability requirements. At the same time, the use of PFAS chemicals in industry has led to their release in drinking water sources. As worry over PFAS exposure and health risks rise, it is necessary to figure out the best way to remove PFASs from drinking water.
Here, electrospinning is used to create new polymer-based filters for use in face masks. These new filter materials are improved with antimicrobial features so that they can be used for longer periods of time, and are tested to make sure they meet filtration and breathability standards. Electrospinning is also used to create filters that quickly remove large amounts of PFAS from polluted water supplies. Overall, this research shows how electrospinning can be used as a tool for different applications. Specifically, this research offers new knowledge and technology for managing PFAS pollution in drinking water sources. This research also describes new face mask filter materials and their creation so the broader research community can continue to improve medical face mask design and supply.
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984362457602771
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