Matching Items (10)
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- All Subjects: water treatment
- All Subjects: Transition Metals
- Genre: Academic theses
- Creators: Green, Matthew
- Creators: Perreault, Francois
- Status: Published
Description
Electrospinning is a means of fabricating micron-scale diameter fiber networks with enmeshed nanomaterials. Polymeric nanocomposites for water treatment require the manipulation of fiber morphology to expose nanomaterial surface area while anchoring the nanomaterials and maintaining fiber integrity; that is the overarching goal of this dissertation. The first investigation studied the effect of metal oxide nanomaterial loadings on electrospinning process parameters such as critical voltage, viscosity, fiber diameter, and nanomaterial distribution. Increases in nanomaterial loading below 5% (w/v) were not found to affect critical voltage or fiber diameter. Nanomaterial dispersion was conserved throughout the process. Arsenic adsorption tests determined that the fibers were non-porous. Next, the morphologies of fibers made with carbonaceous materials and the effect of final fiber assembly on adsorption kinetics of a model organic contaminant (phenanthrene, PNT) was investigated. Superfine powdered activated carbon (SPAC), C60 fullerenes, multi-walled carbon nanotubes, and graphene platelets were added to PS and electrospun. SPAC maintained its internal pore structure and created porous fibers which had 30% greater PNT sorption than PS alone and a sevenfold increase in surface area. Carbon-based nanomaterial-PS fibers were thicker but less capacious than neat polystyrene electrospun fibers. The surface areas of the carbonaceous nanomaterial-polystyrene composites decreased compared to neat PS, and PNT adsorption experiments yielded decreased capacity for two out of three carbonaceous nanomaterials. Finally, the morphology and arsenic adsorption capacity of a porous TiO2-PS porous fiber was investigated. Porous fiber was made using polyvinylpyrrolidone (PVP) as a porogen. PVP, PS, and TiO2 were co-spun and the PVP was subsequently eliminated, leaving behind a porous fiber morphology which increased the surface area of the fiber sevenfold and exposed the nanoscale TiO2 enmeshed inside the PS. TiO2-PS fibers had comparable arsenic adsorption performance to non-embedded TiO2 despite containing less TiO2 mass. The use of a sacrificial polymer as a porogen facilitates the creation of a fiber morphology which provides access points between the target pollutant in an aqueous matrix and the sorptive nanomaterials enmeshed inside the fiber while anchoring the nanomaterials, thus preventing release.
ContributorsHoogesteijn von Reitzenstein, Natalia Virginia (Author) / Westerhoff, Paul (Thesis advisor) / Hristovski, Kiril (Committee member) / Perreault, Francois (Committee member) / Herckes, Pierre (Committee member) / Arizona State University (Publisher)
Created2018
Description
The large-scale anthropogenic emission of carbon dioxide into the atmosphere leads to many unintended consequences, from rising sea levels to ocean acidification. While a clean energy infrastructure is growing, mid-term strategies that are compatible with the current infrastructure should be developed. Carbon capture and storage in fossil-fuel power plants is one way to avoid our current gigaton-scale emission of carbon dioxide into the atmosphere. However, for this to be possible, separation techniques are necessary to remove the nitrogen from air before combustion or from the flue gas after combustion. Metal-organic frameworks (MOFs) are a relatively new class of porous material that show great promise for adsorptive separation processes. Here, potential mechanisms of O2/N2 separation and CO2/N2 separation are explored.
First, a logical categorization of potential adsorptive separation mechanisms in MOFs is outlined by comparing existing data with previously studied materials. Size-selective adsorptive separation is investigated for both gas systems using molecular simulations. A correlation between size-selective equilibrium adsorptive separation capabilities and pore diameter is established in materials with complex pore distributions. A method of generating mobile extra-framework cations which drastically increase adsorptive selectivity toward nitrogen over oxygen via electrostatic interactions is explored through experiments and simulations. Finally, deposition of redox-active ferrocene molecules into systematically generated defects is shown to be an effective method of increasing selectivity towards oxygen.
First, a logical categorization of potential adsorptive separation mechanisms in MOFs is outlined by comparing existing data with previously studied materials. Size-selective adsorptive separation is investigated for both gas systems using molecular simulations. A correlation between size-selective equilibrium adsorptive separation capabilities and pore diameter is established in materials with complex pore distributions. A method of generating mobile extra-framework cations which drastically increase adsorptive selectivity toward nitrogen over oxygen via electrostatic interactions is explored through experiments and simulations. Finally, deposition of redox-active ferrocene molecules into systematically generated defects is shown to be an effective method of increasing selectivity towards oxygen.
ContributorsMcIntyre, Sean (Author) / Mu, Bin (Thesis advisor) / Green, Matthew (Committee member) / Lind, Marylaura (Committee member) / Arizona State University (Publisher)
Created2019
Description
Water recovery from impaired sources, such as reclaimed wastewater, brackish groundwater, and ocean water, is imperative as freshwater resources are under great pressure. Complete reuse of urine wastewater is also necessary to sustain life on space exploration missions of greater than one year’s duration. Currently, the Water Recovery System (WRS) used on the National Aeronautics and Space Administration (NASA) shuttles recovers only 70% of generated wastewater.1 Current osmotic processes show high capability to increase water recovery from wastewater. However, commercial reverse osmosis (RO) membranes rapidly degrade when exposed to pretreated urine-containing wastewater. Also, non-ionic small molecules substances (i.e., urea) are very poorly rejected by commercial RO membranes.
In this study, an innovative composite membrane that integrates water-selective molecular sieve particles into a liquid-barrier chemically resistant polymer film is synthetized. This plan manipulates distinctive aspects of the two materials used to create the membranes: (1) the innate permeation and selectivity of the molecular sieves, and (2) the decay-resistant, versatile, and mechanical strength of the liquid-barrier polymer support matrix.
To synthesize the membrane, Linde Type A (LTA) zeolite particles are anchored to the porous substrate, producing a single layer of zeolite particles capable of transporting water through the membrane. Thereafter, coating the chemically resistant latex polymer filled the space between zeolites. Finally, excess polymer was etched from the surface to expose the zeolites to the feed solution. The completed membranes were tested in reverse osmosis mode with deionized water, sodium chloride, and rhodamine solutions to determine the suitability for water recovery.
The main distinguishing characteristics of the new membrane design compared with current composite membrane include: (1) the use of an impermeable polymer broadens the range of chemical resistant polymers that can be used as the polymer matrix; (2) the use of zeolite particles with specific pore size insures the high rejection of the neutral molecules since water is transported through the zeolite rather than the polymer; (3) the use of latex dispersions, environmentally friendly water based-solutions, as the polymer matrix shares the qualities of low volatile organic compound, low cost, and non- toxicity.
In this study, an innovative composite membrane that integrates water-selective molecular sieve particles into a liquid-barrier chemically resistant polymer film is synthetized. This plan manipulates distinctive aspects of the two materials used to create the membranes: (1) the innate permeation and selectivity of the molecular sieves, and (2) the decay-resistant, versatile, and mechanical strength of the liquid-barrier polymer support matrix.
To synthesize the membrane, Linde Type A (LTA) zeolite particles are anchored to the porous substrate, producing a single layer of zeolite particles capable of transporting water through the membrane. Thereafter, coating the chemically resistant latex polymer filled the space between zeolites. Finally, excess polymer was etched from the surface to expose the zeolites to the feed solution. The completed membranes were tested in reverse osmosis mode with deionized water, sodium chloride, and rhodamine solutions to determine the suitability for water recovery.
The main distinguishing characteristics of the new membrane design compared with current composite membrane include: (1) the use of an impermeable polymer broadens the range of chemical resistant polymers that can be used as the polymer matrix; (2) the use of zeolite particles with specific pore size insures the high rejection of the neutral molecules since water is transported through the zeolite rather than the polymer; (3) the use of latex dispersions, environmentally friendly water based-solutions, as the polymer matrix shares the qualities of low volatile organic compound, low cost, and non- toxicity.
ContributorsKhosravi, Afsaneh Khosravi (Author) / Lind, Mary Laura (Thesis advisor) / Dai, Lenore (Committee member) / Green, Matthew (Committee member) / Lin, Jerry (Committee member) / Seo, Don (Committee member) / Arizona State University (Publisher)
Created2016
Description
As selenium is toxic at low levels, treatment methods to remove selenium from industrial waste waters are needed. In this work, three groups of sorbent materials were investigated in detail for their effectiveness for selenium and arsenic removal from water: 1) nanostructured carbon-based materials, 2) layered double hydroxide (LDH)-based materials, and 3) biopolymer-based sorbents. The materials were investigated in spiked de-ionized water and waters collected from different locations at Salt River Project’s (SRP) Santan Generating Station in Gilbert, AZ. The results show that nanostructured carbon-based materials removed ~80% and up to 100% selenium and arsenic, respectively in spiked DI water. Heat treated layered double hydroxides removed close to 100% removal in selenium and arsenic spiked DI water. Isotherms conducted in spiked DI water fit the Langmuir model and showed a maximum selenate adsorption capacity of 67 mg/g for the calcined LDH powder. Results from SRP waters showed that certain LDH sorbents were effective for removing the selenium, but that higher pH and existence of competing ions affected the removal efficiencies. The functionalized biopolymer sorbent from Crystal Clear Technologies: CCT-149/OCI-B showed good removal efficiencies for both selenate and selenite in DI water. Isotherms conducted in spiked DI water for CCT-149 fit the Langmuir model and showed a maximum selenate adsorption capacity of 90.9 mg/g. Column tests using spiked DI water and waters obtained from SRP wells were investigated using both LDH and CCT-149/OCI-B. Removal of sulfate using chemical pre-treatment of the water with barium chloride resulted in about three times higher selenate loading onto the granular LDH and doubled the water volume that can be treated using CCT-149/OCI-B. The results from the column tests are being used to guide the pilot testing investigating the implementation of LDH sorbents at pilot scale at the Santan plant. The good results in the cooling tower #5 blowdown water and combined discharge waste water of SRP provide valuable information about the efficacy and efficiency of adsorptive media for the removal of selenium. Composites comprising LDH nanosheets with different substrates were successfully synthesized that were able to retain the performance in removing selenate of nanosheet LDH.
ContributorsLi, Man (Author) / Chan, Candace (Thesis advisor) / Lind, Mary Laura (Committee member) / Perreault, Francois (Committee member) / Arizona State University (Publisher)
Created2017
Description
A new class of layered materials called the transition metal trichalcogenides (TMTCs) exhibit strong anisotropic properties due to their quasi-1D nature. These 2D materials are composed of chain-like structures which are weakly bound to form planar sheets with highly directional properties. The vibrational properties of three materials from the TMTC family, specifically TiS3, ZrS3, and HfS3, are relatively unknown and studies performed in this work elucidates the origin of their Raman characteristics. The crystals were synthesized through chemical vapor transport prior to mechanical exfoliation onto Si/SiO¬2 substrates. XRD, AFM, and Raman spectroscopy were used to determine the crystallinity, thickness, and chemical signature of the exfoliated crystals. Vibrational modes and anisotropic polarization are investigated through density functional theory calculations and angle-resolved Raman spectroscopy. Particular Raman modes are explored in order to correlate select peaks to the b-axis crystalline direction. Mode III vibrations for TiS3, ZrS3, and HfS3 are shared between each material and serves as a unique identifier of the crystalline orientation in MX3 materials. Similar angle-resolved Raman studies were conducted on the novel Nb0.5Ti0.5S3 alloy material grown through chemical vapor transport. Results show that the anisotropy direction is more difficult to determine due to the randomization of quasi-1D chains caused by defects that are common in 2D alloys. This work provides a fundamental understanding of the vibrational properties of various TMTC materials which is needed to realize applications in direction dependent polarization and linear dichroism.
ContributorsKong, Wilson (Author) / Tongay, Sefaattin (Thesis advisor) / Wang, Liping (Committee member) / Green, Matthew (Committee member) / Arizona State University (Publisher)
Created2017
Description
Electrochemical technologies emerge as a feasible solution to monitor and treat pollutants. Although electrochemical technologies have garnered widespread attention, their commercial applications are still constrained by the use of expensive electrocatalysts, and the bulky and rigid plate design of electrodes that restricts electrochemical reactor design to systems with poor electrode surface/ volume treated ratios. By making electrodes flexible, more compact designs that maximize electrode surface per volume treated might become a reality. This dissertation encompasses the successful fabrication of flexible nanocomposite electrodes for electrocatalysis and electroanalysis applications.First, nano boron-doped diamond electrodes (BDD) were prepared as an inexpensive alternative to commercial boron-doped diamond electrodes. Comparative detailed surface and electrochemical characterization was conducted. Empirical study showed that replacing commercial BDD electrodes with nano-BDD electrodes can result in a cost reduction of roughly 1000x while maintaining the same electrochemical performance.
Next, self-standing electrodes were fabricated through the electropolymerization of conducing polymer, polypyrrole. Surface characterizations, such as SEM, FTIR and XPS proved the successful fabrication of these self-standing electrodes. High mechanical stability and bending flexibility demonstrated the ability to use these electrodes in different designs, such as roll-to-roll membranes. Electrochemical nitrite reduction was employed to demonstrate the viability of using self-standing nanocomposite electrodes for electrocatalytic applications reducing hazardous nitrogen oxyanions (i.e., nitrite) towards innocuous species such as nitrogen gas. A high faradaic efficiency of 78% was achieved, with high selectivity of 91% towards nitrogen gas.
To further enhance the conductivity and charge transfer properties of self-standing polypyrrole electrodes, three different nanoparticles, including copper (Cu), gold (Au), and platinum (Pt), were incorporated in the polypyrrole matrix. Effect of nanoparticle wt% and interaction between metal nanoparticles and polypyrrole matrix was investigated for electroanalytical applications, specifically dopamine sensing. Flexible nanocomposite electrodes showed outstanding performance as electrochemical sensors with PPy-Cu 120s exhibiting a low limit of detection (LOD) of 1.19 µM and PPy-Au 120s exhibiting a high linear range of 5 µM - 300 µM.
This dissertation outlines a method of fabricating self-standing electrodes and provides a pathway of using self-standing electrodes based on polypyrrole and polypyrrole-metal nanocomposites for various applications in wastewater treatment and electroanalytical sensing.
ContributorsBansal, Rishabh (Author) / Garcia-Segura, Sergio (Thesis advisor) / Westerhoff, Paul (Committee member) / Perreault, Francois (Committee member) / Chan, Candace (Committee member) / Arizona State University (Publisher)
Created2023
Description
More recently there have been a tremendous advancement in theoretical studies showing remarkable properties that could be exploited from transition metal dichalcogenide (TMDC) Janus crystals through various applications. These Janus crystals are having a proven intrinsic electrical field due to breaking of out-of-plane inversion symmetry in a conventional TMDC when one of the chalcogenides atomic layer is being completely replaced by a layer of different chalcogen element. However, due to lack of accurate processing control at nanometer scales, key for creating a highly crystalline Janus structure has not yet been familiarized. Thus, experimental characterization and implication of these Janus crystals are still in a state of stagnation. This work presents a new advanced methodology that could prove to be highly efficient and effective for selective replacement of top layer atomic sites at room temperature conditions.
This is specifically more focused on proving an easy repeatability for replacement of top atomic layer chalcogenide from a parent structure of already grown TMDC monolayer (via CVD) by a post plasma processing technique. Though this developed technique is not limited to only chalcogen atom replacement but can be extended to any type of surface functionalization requirements.
Basic characterization has been performed on the Janus crystal of SeMoS and SeWS where, creation and characterization of SeWS has been done for the very first time, evidencing a repeatable nature of the developed methodology.
This is specifically more focused on proving an easy repeatability for replacement of top atomic layer chalcogenide from a parent structure of already grown TMDC monolayer (via CVD) by a post plasma processing technique. Though this developed technique is not limited to only chalcogen atom replacement but can be extended to any type of surface functionalization requirements.
Basic characterization has been performed on the Janus crystal of SeMoS and SeWS where, creation and characterization of SeWS has been done for the very first time, evidencing a repeatable nature of the developed methodology.
ContributorsTrivedi, Dipesh (Author) / Tongay, Sefaattin (Thesis advisor) / Green, Matthew (Committee member) / Zhuang, Houlong (Committee member) / Arizona State University (Publisher)
Created2019
Description
Two-dimensional quantum materials have garnered increasing interest in a wide
variety of applications due to their promising optical and electronic properties. These
quantum materials are highly anticipated to make transformative quantum sensors and
biosensors. Biosensors are currently considered among one of the most promising
solutions to a wide variety of biomedical and environmental problems including highly
sensitive and selective detection of difficult pathogens, toxins, and biomolecules.
However, scientists face enormous challenges in achieving these goals with current
technologies. Quantum biosensors can have detection with extraordinary sensitivity and
selectivity through manipulation of their quantum states, offering extraordinary properties
that cannot be attained with traditional materials. These quantum materials are anticipated
to make significant impact in the detection, diagnosis, and treatment of many diseases.
Despite the exciting promise of these cutting-edge technologies, it is largely
unknown what the inherent toxicity and biocompatibility of two-dimensional (2D)
materials are. Studies are greatly needed to lay the foundation for understanding the
interactions between quantum materials and biosystems. This work introduces a new
method to continuously monitor the cell proliferation and toxicity behavior of 2D
materials. The cell viability and toxicity measurements coupled with Live/Dead
fluorescence imaging suggest the biocompatibility of crystalline MoS2 and MoSSe
monolayers and the significantly-reduced cellular growth of defected MoTe2 thin films
and exfoliated MoS2 nanosheets. Results show the exciting potential of incorporating
kinetic cell viability data of 2D materials with other assay tools to further fundamental
understanding of 2D material biocompatibility.
variety of applications due to their promising optical and electronic properties. These
quantum materials are highly anticipated to make transformative quantum sensors and
biosensors. Biosensors are currently considered among one of the most promising
solutions to a wide variety of biomedical and environmental problems including highly
sensitive and selective detection of difficult pathogens, toxins, and biomolecules.
However, scientists face enormous challenges in achieving these goals with current
technologies. Quantum biosensors can have detection with extraordinary sensitivity and
selectivity through manipulation of their quantum states, offering extraordinary properties
that cannot be attained with traditional materials. These quantum materials are anticipated
to make significant impact in the detection, diagnosis, and treatment of many diseases.
Despite the exciting promise of these cutting-edge technologies, it is largely
unknown what the inherent toxicity and biocompatibility of two-dimensional (2D)
materials are. Studies are greatly needed to lay the foundation for understanding the
interactions between quantum materials and biosystems. This work introduces a new
method to continuously monitor the cell proliferation and toxicity behavior of 2D
materials. The cell viability and toxicity measurements coupled with Live/Dead
fluorescence imaging suggest the biocompatibility of crystalline MoS2 and MoSSe
monolayers and the significantly-reduced cellular growth of defected MoTe2 thin films
and exfoliated MoS2 nanosheets. Results show the exciting potential of incorporating
kinetic cell viability data of 2D materials with other assay tools to further fundamental
understanding of 2D material biocompatibility.
ContributorsTran, Michael, Ph.D (Author) / Tongay, Sefaattin (Thesis advisor) / Green, Matthew (Thesis advisor) / Muhich, Christopher (Committee member) / Arizona State University (Publisher)
Created2019
Description
Engineered nanomaterials (ENMs) are added to numerous consumer products to enhance their effectiveness, whether it be for environmental remediation, mechanical properties, or as dietary supplements. Uses of ENMs include adding to enhance products, carbon for strength or dielectric properties, silver for antimicrobial properties, zinc oxide for UV sun-blocking properties, titanium dioxide for photocatalysis, or silica for desiccant properties. However, concerns arise from ENM functional properties that can impact the environment and a lack of regulation regarding ENMs leads to potential public exposure to ENMs and results in ill-informed public or manufacturer perceptions of ENMs. My dissertation evaluates the environmental, human health, and societal impacts of using ENMs, with a focus on ionic silver and nanosilver, in consumer and industrial products. Reproducible experiments served as functional assays to assess ENM distributions among various environmental matrices. Functional assay results were visualized using radar plots and aid in a framework to estimate likely ENM disposition in the environment. To assess beneficial uses of ENMs, bromide ion removal from drinking waters to limit disinfection by-product formation was studied. Silver-enabled graphene oxide materials were capable of removing bromide from water, and exhibited less competition from background solutes (e.g. natural organic matter) when compared against solely ionic silver addition to water for bromide removal. To assess complex interactions of ENMs with the microbiome, batch experiments were performed using fecal samples spiked with ionic silver or commercial dietary silver nanoparticles. Dietary nanosilver and ionic silver exposures to the fecal microbiome for 24 hours reduce short chain fatty acid (SCFA) production and changes the relative abundance of the microbiota. To understand the social perceptions of ENMS, statistically rigorous surveys were conducted to assess related perceptions related to the use of ENMs in drinking water treatment devices the general public and, separately, industrial manufacturers. These stakeholders are influenced by costs and efficiency of the technologies, consumer concerns of the safety of technologies, and environmental health and safety of the technologies. This dissertation represents novel research that took an interdisciplinary approach, spanning from wet-lab engineering bench scale testing to social science survey assessments to better understand the environmental, human health, and societal impacts of using ENMs such as nanosilver and ionic silver in industrial processes and consumer products.
ContributorsKidd, Justin (Author) / Westerhoff, Paul (Thesis advisor) / Krajmalnik-Brown, Rosa (Committee member) / Perreault, Francois (Committee member) / Maynard, Andrew (Committee member) / Arizona State University (Publisher)
Created2020
Description
Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals used for a wide variety of products and industrial processes, including being an essential class of chemicals in the fabrication of semiconductors. Proven concerns related to bioaccumulation and toxicity across multiple species have resulted in health advisory and regulatory initiatives for PFAS in drinking and wastewaters. Among impacted users of PFAS, the semiconductor industry is in urgent need of technologies to remove PFAS from water. Specifically, they prefer technologies capable of mineralizing PFAS into inorganic fluoride (F-). The goal of this thesis is to compare the effectiveness of photo- versus electrocatalytic treatment in benchtop reactor systems PFAS in industrial wastewater before selecting one technology to investigate comprehensively. First, a model wastewater was developed based upon semiconductor samples to represent water matrices near where PFAS are used and the aggregate Fab effluent, which were then used in batch catalytic experiments. Second, batch experiments with homogenous photocatalysis (UV/SO32-) were found to be more energy-intensive than heterogeneous catalysis using boron-doped diamond (BDD) electrodes, and the latter approach was then studied in-depth.
During electrocatalysis, longer chain PFAS (C8; PFOA & PFOS) were observed to degrade faster than C6 and C4 PFAS. This study is the first to report near-complete defluorination of not only C8- and C6- PFAS, but also C4-PFAS, in model wastewaters using BDD electrocatalysis, and the first to report such degradation in real Fab wastewater effluents. Based upon differences in PFAS degradation rates observed in single-solute systems containing only C4 PFAS versus multi-solute systems including C4, C6, and C8 PFAS, it was concluded that the surfactant properties of the longer-chain PFAS created surface films on the BDD electrode surface which synergistically enhanced removal of shorter-chain PFAS. The results from batch experiments that serve as the basis of this thesis will be used to assess the chemical byproducts and their associated bioaccumulation and toxicity. This thesis was aimed at developing an efficient method for the degradation of perfluoroalkyl substances from industrial process waters at realistic concentrations.
ContributorsNienhauser, Alec Brockway (Author) / Westerhoff, Paul (Thesis advisor) / Garcia-Segura, Sergi (Committee member) / Thomas, Marylaura (Committee member) / Green, Matthew (Committee member) / Arizona State University (Publisher)
Created2021