Thesis
Electrospun functionalized nanofibers for the removal of anionic nitrogen species from drinking water
University of Iowa
Master of Science (MS), University of Iowa
Autumn 2021
DOI: 10.17077/etd.006342
Abstract
Point source discharges from municipal treatment plants, compounded by nonpoint source runoff from excessive land application of fertilizer and manure, has produced nitrogen-impaired surface waters and groundwater across the Midwest. This contamination poses health risks to consumers who rely on drinking water sources with elevated nitrate, which has well-established acute and emerging chronic health impacts. Here, we develop surface-functionalized polymer nanofibers for the selective and high-capacity removal of nitrate from contaminated drinking water supplies, including decentralized sources like private wells. Using the material fabrication approach of electrospinning, we harnessed the properties of surface-segregating quaternary ammonium surfactants (QAS) for the dual purpose of reducing surface tension in the precursor solution to produce more uniformly distributed polyacrylonitrile (PAN) nanofibers and to enrich the PAN scaffold with ion exchange sites resembling those commonly used in nitrate-specific strong base anion exchange resins. Through tailored nanofiber synthesis, we determined the optimal nanofiber formulation for nitrate and nitrite uptake across various material properties and solution conditions representative of water treatment. Notably, work with various QAS (chloride, bromide and iodide salts of tetrabutylammonium; TBAC, TBAB, and TBAI, respectively) led us to propose that the size of the halide counterion impacts QAS surface segregation, which in turn influences the number and density of ion exchange sites on the polymer surface, with uptake greatest using TBAC. Materials with an optimal QAS loading of ~20 wt.% relative to PAN in the precursor sol gel resulted in relatively fast uptake (equilibrium time between 0.75-1.5 hours from kinetic uptake studies) with nitrite and nitrate capacity of 6 and ~8 mg/g, respectively, from isotherm experiments. Uptake was confirmed to occur via an ion exchange mechanism, with an established exchange stoichiometry of 1.3(± 0.5) and 1.5(± 0.2) for nitrate and nitrite, respectively. Materials could also be regenerated with concentrated brine, while also exhibiting selectivity (in more complex solutions with sulfate and carbonate) consistent with commercially available nitrate-selective resins. Overall, electrospinning produces surface-functionalized nanofibers with performance that is comparable to commercial nitrate selective resins while in a versatile membrane platform that may help aid integration into existing point-of-use and point-of-entry treatment devices.
Details
- Title: Subtitle
- Electrospun functionalized nanofibers for the removal of anionic nitrogen species from drinking water
- Creators
- Humberto E. González Ribot
- Contributors
- David M Cwiertny (Advisor)Syed Mubeen (Committee Member)Craig L Just (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Civil and Environmental Engineering
- Date degree season
- Autumn 2021
- DOI
- 10.17077/etd.006342
- Publisher
- University of Iowa
- Number of pages
- xi, 57 pages
- Copyright
- Copyright 2021 Humberto E. González Ribot
- Language
- English
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 54-57).
- Public Abstract (ETD)
The high use of fertilizers used for crop production and land application of manure from animal operations results in nutrient pollution of waters across the Midwest. Two common forms of nutrient nitrogen resulting from this pollution are nitrate and nitrite. Nitrate is a health risk because it causes Blue Baby Syndrome in infants younger than six months old by interfering with the oxygen-carrying molecules in blood. Nitrate has also been linked to some types of cancer such as ovarian and colorectal cancer. In this work, we have developed a new technology to remove nitrate and nitrite from drinking water. This technology relies on polymer nanofibers, a unique-fabric like material that we have designed to efficiently filter out nitrate and nitrite from water. These nanofibers were able to remove nitrate from water and exhibit a very high removal capacity. They are also capable of removing nitrate and nitrite from water that contain a mixture of other chemicals and pollutants. Additional work shows how the process by which we make these nanofibers, called electrospinning, can be controlled to help optimize filters for water treatment. Ultimately, we show that our nanofiber filter performs similarly to current water treatment technologies commercially available for nitrate removal. The materials produced herein may be an industrially viable, future alternative for water treatment. We envision these filters may be of particular value in regions where the costs for treating nitrate with existing technologies are too expensive, for households where private wells are the primary source of drinking water, at small water treatment plants, and, in general, for consumers served by water systems that do not use nitrate removal technologies.
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984210527102771
Metrics
9 File views/ downloads
53 Record Views