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- Genre: Doctoral Dissertation
Description
An urgent need for developing new chemical separations that address the capture of dilute impurities from fluid streams are needed. These separations include the capture of carbon dioxide from the atmosphere, impurities from drinking water, and toxins from blood streams. A challenge is presented when capturing these impurities because the energy cost for processing the bulk fluid stream to capture trace contaminants is too great using traditional thermal separations. The development of sorbents that may capture these contaminants passively has been emphasized in academic research for some time, producing many designer materials including metal-organic frameworks (MOFs) and polymeric resins. Scaffolds must be developed to effectively anchor these materials in a passing fluid stream. In this work, two design techniques are presented for anchoring these sorbents in electrospun fiber scaffolds.
The first technique involves imbedding sorbent particles inside the fibers: forming particle-embedded fibers. It is demonstrated that particles will spontaneously coat themselves in the fibers at dilute loadings, but at higher loadings some get trapped on the fiber surface. A mathematical model is used to show that when these particles are embedded, the polymeric coating provided by the fibers may be designed to increase the kinetic selectivity and/or stability of the embedded sorbents. Two proof-of-concept studies are performed to validate this model including the increased selectivity of carbon dioxide over nitrogen when the MOF ZIF-8 is embedded in a poly(ethylene oxide) and Matrimid polymer blend; and that increased hydrothermal stability is realized when the water-sensitive MOF HKUST-1 is embedded in polystyrene fibers relative to pure HKUST-1 powder.
The second technique involves the creation of a pore network throughout the fiber to increase accessibility of embedded sorbent particles. It is demonstrated that the removal of a blended highly soluble polymer additive from the spun particle-containing fibers leaves a pore network behind without removing the embedded sorbent. The increased accessibility of embedded sorbents is validated by embedding a known direct air capture sorbent in porous electrospun fibers, and demonstrating that they have the fastest kinetic uptake of any direct air capture sorbent reported in literature to date, along with over 90% sorbent accessibility.
The first technique involves imbedding sorbent particles inside the fibers: forming particle-embedded fibers. It is demonstrated that particles will spontaneously coat themselves in the fibers at dilute loadings, but at higher loadings some get trapped on the fiber surface. A mathematical model is used to show that when these particles are embedded, the polymeric coating provided by the fibers may be designed to increase the kinetic selectivity and/or stability of the embedded sorbents. Two proof-of-concept studies are performed to validate this model including the increased selectivity of carbon dioxide over nitrogen when the MOF ZIF-8 is embedded in a poly(ethylene oxide) and Matrimid polymer blend; and that increased hydrothermal stability is realized when the water-sensitive MOF HKUST-1 is embedded in polystyrene fibers relative to pure HKUST-1 powder.
The second technique involves the creation of a pore network throughout the fiber to increase accessibility of embedded sorbent particles. It is demonstrated that the removal of a blended highly soluble polymer additive from the spun particle-containing fibers leaves a pore network behind without removing the embedded sorbent. The increased accessibility of embedded sorbents is validated by embedding a known direct air capture sorbent in porous electrospun fibers, and demonstrating that they have the fastest kinetic uptake of any direct air capture sorbent reported in literature to date, along with over 90% sorbent accessibility.
ContributorsArmstrong, Mitchell (Author) / Mu, Bin (Thesis advisor) / Green, Matthew (Committee member) / Seo, Dong (Committee member) / Lackner, Klaus (Committee member) / Holloway, Julianne (Committee member) / Arizona State University (Publisher)
Created2018
Description
The excessive use of fossil fuels over the last few centuries has led to unprecedented changes in climate and a steady increase in the average surface global temperatures. Direct Air Capture(DAC) aims to capture CO2 directly from the atmosphere and alleviate some of the adverse effects of climate change. This dissertation focuses on methodologies to make advanced functional materials that show good potential to be used as DAC sorbents. Details on sorbent material synthesis and post-synthesis methods to obtain high surface area morphologies are described in detail. First, by incorporating K2CO3 into activated carbon (AC) fiber felts, the sorption kinetics was significantly improved by increasing the surface area of K2CO3 in contact with air. The AC-K2CO3 fiber composite felts are flexible, cheap, easy to manufacture, chemically stable, and show excellent DAC capacity and (de)sorption rates, with stable performance up to ten cycles. The best composite felts collected an average of 478 µmol of CO2 per gram of composite during 4 h of exposure to ambient (24% RH) air that had a CO2 concentration of 400-450 ppm over 10 cycles. Secondly, incorporating the amino acid L-arginine (L-Arg) into a poly(vinyl alcohol) (PVA) nanofiber support structure, created porous substrates with very high surface areas of L-Arg available for CO2 sorption. The bio-inspired PVA-Arg nanofiber composites are flexible and show excellent DAC performance compared to bulk L-Arg. The nanofiber composites are fabricated from an electrospinning process using an aqueous polymer solution. High ambient humidity levels improve sorption performance significantly. The best performing nanofiber composite collected 542 µmol of CO2 per gram of composite during 2 h of exposure to ambient, high humidity (100% RH) air that had a CO2 concentration of 400-450 ppm. Finally, poly(vinyl guanidine) (PVG) polymer was synthesized and tested for sorption performance. The fabrication of PVG nanofibers, divinyl benzene crosslinked PVG beads and glutaraldehyde crosslinked PVG were demonstrated. The sorption performance of the fabricated sorbents were tested with the glutaraldehyde crosslinked PVG having a dynamic sorption capacity of over 1 mmol of CO2 per gram of polymer in 3 h. The sorption capability of liquid PVG was also explored.
ContributorsModayil Korah, Mani (Author) / Green, Matthew D (Thesis advisor) / Lackner, Klaus (Committee member) / Long, Timothy E (Committee member) / Thomas, Marylaura L (Committee member) / Jin, Kailong (Committee member) / Arizona State University (Publisher)
Created2024
Description
Climate change poses a serious challenge humankind. Society’s reliance on fossil fuels raises atmospheric CO2 concentrations causing global warming. Already, the planet has warmed by 1.1 °C making it nearly impossible to heed the advice of the IPCC (2022) and prevent warming in excess of 1.5 °C by 2050. Even the current excess of CO2 in the atmosphere poses significant risks. Direct air capture (DAC) of CO2 offers one of the most scalable options to the drawdown of carbon. DAC can collect CO2 that is already diluted into the atmosphere for disposal or utilization. Central to most DAC are sorbents, i.e., materials that bind and release CO2 in a capture and release cycle. There are sorbents that cycle through a temperature swing. Others use a moisture swing, or a pressure swing or combinations of all of them. Since DAC is still a nascent technology, advancement of sorbents is an important part of DAC development. There is a nearly infinite combination of possible sorbents and form factors of sorbents that can be deployed in many different variations of DAC. Our goal is to develop a methodology for characterizing sorbents to facilitate rational choices among different options. Good sorbent characteristics include high capacity, fast sorption and desorption kinetics, low energy need for unloading, and longevity. This work presents the development of a systematic approach to evaluate sorbents from the milligram to tonne scale focusing on the important characteristics mentioned above. The work identified a good temperature swing sorbent whose characterization moved from the mg to kg scale without loss in performance. This work represents a first step in systematizing sorbent characterization for rational sorbent development programs.
ContributorsStangherlin Barbosa, Thiago (Author) / Lackner, Klaus (Thesis advisor) / Cirucci, John (Committee member) / Dirks, Gary (Committee member) / Arizona State University (Publisher)
Created2022
Description
Building-integrated carbon-capture (BICC) is an envisioned mechanism capable of absorbing carbon dioxide (CO2) from the air to be stored and then converted into useful carbon-based materials without negatively impacting the environment. This dissertation builds on the authors' previous work, in which building façades were treated as artificial leaves capable of providing shade to lower solar heat gain, while simultaneously capturing CO2 through the air filters attached to the building façades by attempting a different approach capable of capturing CO2 within buildings. This dissertation presents the author’s work on BICC, where buildings are envisioned as CO2 reservoirs or vacuums, into which mechanical systems introduce fresh air, and through human activities, the air within the building becomes enriched with CO2 before being pushed out back to the outer environment. The design of a carbon-capture mechanism will take advantage of the ventilation side of existing HVAC systems, through which BICC captures CO2 from the exhaust-enriched CO2 air. BICC will utilize existing opportunities and components within buildings represented in the high CO2 concentration in buildings, ventilation guidelines, mechanical equipment represented in air handling unit and air duct network, in addition to natural gas grid connectivity. BICC will capture CO2 through buildings' mechanical system, and the captured CO2 would then be converted into renewable methane to be injected into the existing natural gas pipeline network. This dissertation will investigate the potential of BICC to offset carbon emissions from multiple commercial building types and will present a utilization strategy for the captured carbon.
ContributorsBen Salamah, Fahad (Author) / Bryan, Harvey (Thesis advisor) / Lackner, Klaus (Committee member) / Reddy, T Agami (Committee member) / Arizona State University (Publisher)
Created2021
Description
Halogens in drinking water sources, such as bromine (Br) and iodine (I) pose no direct health risk, but are critical precursors in formation of cyto- and genotoxic brominated and iodinated (Br-/I-) DBPs. However, few spatial or historic datasets exist for bromine and iodine species in drinking water sources. This dissertation aims to quantify and understand the occurrence and speciation of Br and I in groundwater and surface water serving as source waters for drinking water treatment plants (DWTPs). Aggregation of data from >9000 non-drinking water sampling locations in USA collected from 1930-2017 on halides (bromide (Br-) and iodide (I-)) determined that Br- concentrations were 50 μg/L and 100 μg/L; and I- concentrations were 12 μg/L and 13 μg/L in surface and groundwater respectively. Although, these locations were not drinking water sources, this first of its kind analysis provides potential bounds for Br- and I-. To focus specifically on DWTP sources, a nationwide survey of >250 drinking water sources was conducted between 2018-2020. Br- ion is the only bromine specie, whereas both inorganic (iodide and iodate ions) and organic iodine occur. I- concentrations ranged from 1-250 μg/L and are 4 to 100 times lower than Br- concentrations (10-7800 μg/L, median=80 μg/L). No strong correlation exists between bromide and iodide occurrence (R<0.5, p<0.005). I- was detected in 50% of the samples (75th percentile=5 μg/L) and IO3- was detected in 40% (75th percentile=3 μg/L) of all the samples. To quantify iodine species, tandem ion chromatography and inductively coupled plasma mass spectrometry was applied for the first time in drinking water sources. I- and IO3- peaks were well resolved and have minimum detection limit of 0.4 μg/L and 0.7 μg/L respectively. Organic iodine (Org-I) peaks in select drinking water samples from the nationwide survey were partically resolved ranging from <5 to 40 μg/L. This dissertation provides updated nationwide Br- survey and first ever national I species survey. The data generated through this dissertation will be useful to further Br-/I-DBP formation and toxicity research by providing relevant drinking water sources information. Future research targeting Br- and I- removal is advocated for managing Br-/I-DBPs in watersheds.
ContributorsSharma, Naushita (Author) / Westerhoff, Paul (Thesis advisor) / Karanfil, Tanju (Committee member) / Herckes, Pierre (Committee member) / Lackner, Klaus (Committee member) / Arizona State University (Publisher)
Created2021