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Description
This dissertation presents a systematic study of the sorption mechanisms of hydrophobic silica aerogel (Cabot Nanogel®) granules for oil and volatile organic compounds (VOCs) in different phases. The performance of Nanogel for removing oil from laboratory synthetic oil-in-water emulsions and real oily wastewater, and VOCs from their aqueous solution, in both packed bed (PB) and inverse fluidized bed (IFB) modes was also investigated. The sorption mechanisms of VOCs in the vapor, pure liquid, and aqueous solution phases, free oil, emulsified oil, and oil from real wastewater on Nanogel were systematically studied via batch kinetics and equilibrium experiments. The VOC results show that the adsorption of vapor is very slow due to the extremely low thermal conductivity of Nanogel. The faster adsorption rates in the liquid and solution phases are controlled by the mass transport, either by capillary flow or by vapor diffusion/adsorption. The oil results show that Nanogel has a very high capacity for adsorption of pure oils. However, the rate for adsorption of oil from an oil-water emulsion on the Nanogel is 5-10 times slower than that for adsorption of pure oils or organics from their aqueous solutions. For an oil-water emulsion, the oil adsorption capacity decreases with an increasing proportion of the surfactant added. An even lower sorption capacity and a slower sorption rate were observed for a real oily wastewater sample due to the high stability and very small droplet size of the wastewater. The performance of Nanogel granules for removing emulsified oil, oil from real oily wastewater, and toluene at low concentrations in both PB and IFB modes was systematically investigated. The hydrodynamics characteristics of the Nanogel granules in an IFB were studied by measuring the pressure drop and bed expansion with superficial water velocity. The density of the Nanogel granules was calculated from the plateau pressure drop of the IFB. The oil/toluene removal efficiency and the capacity of the Nanogel granules in the PB or IFB were also measured experimentally and predicted by two models based on equilibrium and kinetic batch measurements of the Nanogel granules.
ContributorsWang, Ding (Author) / Lin, Jerry Y.S. (Thesis advisor) / Pfeffer, Robert (Thesis advisor) / Westerhoff, Paul (Committee member) / Nielsen, David (Committee member) / Lind, Mary Laura (Committee member) / Arizona State University (Publisher)
Created2011
Description
With the application of reverse osmosis (RO) membranes in the wastewater treatment and seawater desalination, the limitation of flux and fouling problems of RO have gained more attention from researchers. Because of the tunable structure and physicochemical properties of nanomaterials, it is a suitable material that can be used to incorporate with RO to change the membrane performances. Silver is biocidal, which has been used in a variety of consumer products. Recent studies showed that fabricating silver nanoparticles (AgNPs) on membrane surfaces can mitigate the biofouling problem on the membrane. Studies have shown that Ag released from the membrane in the form of either Ag ions or AgNP will accelerate the antimicrobial activity of the membrane. However, the silver release from the membrane will lower the silver loading on the membrane, which will eventually shorten the antimicrobial activity lifetime of the membrane. Therefore, the silver leaching amount is a crucial parameter that needs to be determined for every type of Ag composite membrane.
This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts.
The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test.
This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts.
The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test.
ContributorsHan, Bingru (Author) / Westerhoff, Paul (Thesis advisor) / Perreault, Francois (Committee member) / Sinha, Shahnawaz (Committee member) / Arizona State University (Publisher)
Created2017
Description
The volume of end-of-life photovoltaic (PV) modules is increasing as the global PV market increases, and the global PV waste streams are expected to reach 250,000 metric tons by the end of 2020. If the recycling processes are not in place, there would be 60 million tons of end-of-life PV modules lying in the landfills by 2050, that may not become a not-so-sustainable way of sourcing energy since all PV modules could contain certain amount of toxic substances. Currently in the United States, PV modules are categorized as general waste and can be disposed in landfills. However, potential leaching of toxic chemicals and materials, if any, from broken end-of-life modules may pose health or environmental risks. There is no standard procedure to remove samples from PV modules for chemical toxicity testing in the Toxicity Characteristic Leaching Procedure (TCLP) laboratories as per EPA 1311 standard. The main objective of this thesis is to develop an unbiased sampling approach for the TCLP testing of PV modules. The TCLP testing was concentrated only for the laminate part of the modules, as they are already existing recycling technologies for the frame and junction box components of PV modules. Four different sample removal methods have been applied to the laminates of five different module manufacturers: coring approach, cell-cut approach, strip-cut approach, and hybrid approach. These removed samples were sent to two different TCLP laboratories, and TCLP results were tested for repeatability within a lab and reproducibility between the labs. The pros and cons of each sample removal method have been explored and the influence of sample removal methods on the variability of TCLP results has been discussed. To reduce the variability of TCLP results to an acceptable level, additional improvements in the coring approach, the best of the four tested options, are still needed.
ContributorsLeslie, Joswin (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Srinivasan, Devarajan (Committee member) / Kuitche, Joseph (Committee member) / Arizona State University (Publisher)
Created2018
Description
Nanomaterials (NMs), implemented into a plethora of consumer products, are a potential new class of pollutants with unknown hazards to the environment. Exposure assessment is necessary for hazard assessment, life cycle analysis, and environmental monitoring. Current nanomaterial detection techniques on complex matrices are expensive and time intensive, requiring weeks of sample preparation and detection by specialized equipment, limiting the feasibility of large-scale monitoring of NMs. A need exists to develop a rapid pre-screening technique to detect, within minutes, nanomaterials in complex matrices. The goal of this dissertation is to develop a tiered process to detect and characterize nanomaterials in consumer products and environmental samples. The approach is accomplished through a two tier rapid screening process to screen likely presence/absence of elements present in common nanomaterials at environmentally relevant concentrations followed by a more intensive three tier characterization process, if nanomaterials are likely to occur. The focus is on SiO2 and TiO2 nanomaterials with additional work performed on hydroxyapatite (Ca5(PO4)3(OH)). The five step tiered process is as follows: 1) screen for elements in the sample by laser induced breakdown spectroscopy (LIBS) and X-ray fluorescence (XRF), 2) extract nanomaterials from the sample and screen for extracted elements by LIBS and XRF, 3) confirm presence and elemental composition of nanomaterials by transmission electron microscopy paired with energy dispersive X-ray spectroscopy, 4) quantify the elemental composition of the sample by inductively coupled plasma – mass spectrometry, and 5) identify mineral phase of crystalline material by X-ray diffraction. This dissertation found LIBS to be an accurate method to detect Si and Ti in food matrices (tier one approach) with strong agreement with the product label, detecting Si and Ti in 93% and 89% of the samples labeled as containing each material, respectively. In addition XRF identified Ti, Si, and Ca in 100% of food samples TEM-confirmed to contain Ti, Si, and Ca respectively. As a tier two approach, LIBS on the 0.2 micrometer filter identified nano silicon in 42% of samples confirmed by TEM to contain nano Si and 67% of TEM-confirmed samples to contain Ti. XRF identified Si, Ti, and Ca loaded on to a 0.1 µm filter and Ti in the surfactant rich phase of CPE of water and water with NOM.
ContributorsSchoepf, Jared (Author) / Westerhoff, Paul (Thesis advisor) / Dai, Lenore (Committee member) / Hristovski, Kiril (Committee member) / Herckes, Pierre (Committee member) / Lind, Mary Laura (Committee member) / Arizona State University (Publisher)
Created2018
Description
Connected health is an emerging field of science and medicine that enables the collection and integration of personal biometrics and environment, contributing to more precise and accurate assessment of the person’s state. It has been proven to help to establish wellbeing as well as prevent, diagnose, and determine the prognosis of chronic diseases. The development of sensing devices for connected health is challenging because devices used in the field of medicine need to meet not only selectivity and sensitivity of detection, but also robustness and performance under hash usage conditions, typically by non-experts in analysis. In this work, the properties and fabrication process of sensors built for sensing devices capable of detection of a biomarker as well as pollutant levels in the environment are discussed. These sensing devices have been developed and perfected with the aim of overcoming the aforementioned challenges and contributing to the evolving connected health field. In the first part of this work, a wireless, solid-state, portable, and continuous ammonia (NH3) gas sensing device is introduced. This device determines the concentration of NH3 contained in a biological sample within five seconds and can wirelessly transmit data to other Bluetooth enabled devices. In this second part of the work, the use of a thermal-based flow meter to assess exhalation rate is evaluated. For this purpose, a mobile device named here mobile indirect calorimeter (MIC) was designed and used to measure resting metabolic rate (RMR) from subjects, which relies on the measure of O2 consumption rate (VO2) and CO2 generation rate (VCO2), and compared to a practical reference method in hospital. In the third part of the work, the sensing selectivity, stability and sensitivity of an aged molecularly imprinted polymer (MIP) selective to the adsorption of hydrocarbons were studied. The optimized material was integrated in tuning fork sensors to detect environmental hydrocarbons, and demonstrated the needed stability for field testing. Finally, the hydrocarbon sensing device was used in conjunction with a MIC to explore potential connections between hydrocarbon exposure level and resting metabolic rate of individuals. Both the hydrocarbon sensing device and the metabolic rate device were under field testing. The correlation between the hydrocarbons and the resting metabolic rate were investigated.
ContributorsLiu, Naiyuan (Author) / Forzani, Erica (Thesis advisor) / Raupp, Gregory (Committee member) / Holloway, Julianne (Committee member) / Thomas, Marylaura (Committee member) / Westerhoff, Paul (Committee member) / Arizona State University (Publisher)
Created2018
Description
Anthropogenic processes have increased the concentration of toxic Se, As and N in water. Oxo-anions of these species are poisonous to aquatic and terrestrial life. Current remediation techniques have low selectivity towards their removal. Understanding the chemistry and physics which control oxo-anion adsorption on metal oxide and the catalytic nitrate reduction to inform improved remediation technologies can be done using Density functional theory (DFT) calculations. The adsorption of selenate, selenite, and arsenate was investigated on the alumina and hematite to inform sorbent design strategies. Adsorption energies were calculated as a function of surface structure, composition, binding motif, and pH within a hybrid implicit-explicit solvation strategy. Correlations between surface property descriptors including water network structure, cationic species identity, and facet and the adsorption energies of the ions show that the surface water network controls the adsorption energy more than any other, including the cationic species of the metal-oxide. Additionally, to achieve selectivity for selenate over sulphate, differences in their electronic structure must be exploited, for example by the reduction of selenate to selenite by Ti3+ cations.
Thermochemical or electrochemical reduction pathways to convert NO3- to N2 or NH3, which are benign or value-added products, respectively are examined over single-atom electrocatalysts (SAC) in Cu. The activity and selectivity for nitrate reduction are compared with the competitive hydrogen evolution reaction (HER). Cu suppresses HER but produces toxic NO2- because of a high activation barrier for cleaving the second N-O bond. SACs provide secondary sites for reaction and break traditional linear scaling relationships. Ru-SACs selectively produce NH3 because N-O bond scission is facile, and the resulting N remains isolated on SAC sites; reacting with H+ from solvating H2O to form ammonia. Conversely, Pd-SAC forms N2 because the reduced N* atoms migrate to the Cu surface, which has a low H availability, allowing N atoms to combine to N2. This relation between N* binding preference and reduction product is demonstrated across an array of SAC elements.
Hence, the solvation effects on the surface critically alter the activity of adsorption and catalysis and the removal of toxic pollutants can be improved by altering the surface water network.
ContributorsGupta, Srishti (Author) / Muhich, Christopher L (Thesis advisor) / Singh, Arunima (Committee member) / Emady, Heather (Committee member) / Westerhoff, Paul (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2023
Description
Freshwater as the resource for the survival of humans and all lives on earth is very precious but scarce. The shortage of the original freshwater resources and the interfering activities by human and other natural factors form this issue together. To reduce the water supply pressure and deterioration of freshwater systems (for example, river, wetland, and groundwater), the quantity-increase and the quality-increase strategies should be implemented at the same time. Therefore, corresponding membrane technologies have been developed to achieve water purification with high efficiency and low cost. For desalinating seawater and other types of saline water, pervaporation has been proved that has the potential to complete desalination with salt rejection rate over 99 % when dealing with high salinity water that reverse osmosis (RO) cannot handle. In this dissertation, except the discussion of commonly used materials to synthesize pervaporation membranes, two types of novel pervaporation desalination membranes (nanophotonic-enhanced membrane and free-standing sulfonated membrane) have been presented and discussed. The novel membranes were tested to see the potential of pervaporation to desalinate seawater and saline water with more complex ionic composition, and the possibility of achieving zero liquid discharge in the desalination field when having pervaporation as the assistance. For mitigating polluted water that is caused by human activities, especially agricultural activities, electrodialysis is an effective method to remove specific ions from water, and it does not require extra chemical cost or regeneration. A type of anion exchange membranes inspired by ion exchange resins was synthesized and tested, and the performance on nitrate removal has been evaluated in this dissertation.
ContributorsLi, Yusi (Author) / Lind, Mary Laura (Thesis advisor) / Perreault, Francois (Thesis advisor) / Forzani, Erica (Committee member) / Seo, S. Eileen (Committee member) / Walker, W. Shane (Committee member) / Arizona State University (Publisher)
Created2023
Description
Due to the use of fertilizers, concentrations of harmful nitrate have increased in groundwater and surface waters globally in the last century. Water treatment plants primarily use separation techniques for nitrate treatment, but these technologies create a high nitrate concentration brine that is costly to dispose of. This dissertation focuses on catalytic hydrogenation, an emerging technology capable of reducing nitrate to nitrogen gas using hydrogen gas (H2). This technology reduces nitrate at rates >95% and is an improvement over technologies used at water treatment plants, because the nitrate is chemically transformed with harmless byproducts and no nitrate brine. The goal of this dissertation is to upgrade the maturity of catalytic nitrate hydrogenation systems by overcoming several barriers hindering the scale-up of this technology. Objective 1 is to compare different methods of attaching the bimetallic catalyst to a hollow-fiber membrane surface to find a method that results in 1) minimized catalyst loss, and 2) repeatable nitrate removal over several cycles. Results showed that the In-Situ MCfR-H2 deposition was successful in reducing nitrate at a rate of 1.1 min-1gPd-1 and lost less than 0.05% of attached Pd and In cumulatively over three nitrate treatment cycles. Objective 2 is to synthesize catalyst-films with varied In3+ precursor decorated over a Pd0 surface to show the technology can 1) reliably synthesize In-Pd catalyst-films with varied bimetallic ratios, and 2) optimize nitrate removal activity by varying In-Pd ratio. Results showed that nitrate removal activity was optimized with a rate constant of 0.190 mg*min-1L-1 using a catalyst-film with a 0.045 In-Pd ratio. Objective 3 is to perform nitrate reduction in a continuous flow reactor for two months to determine if nitrate removal activity can be sustained over extended operation and identify methods to overcome catalyst deactivation. Results showed that a combination of increased hydraulic residence time and reduced pH was successful in increasing the nitrate removal and decreasing harmful nitrite byproduct selectivity to 0%. These objectives increased the technology readiness of this technology by enabling the reuse of the catalyst, maximizing nitrate reduction activity, and achieving long-term nitrate removal.
ContributorsLevi, Juliana (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Thesis advisor) / Garcia-Segura, Sergi (Committee member) / Wong, Michael (Committee member) / Lind Thomas, Mary Laura (Committee member) / Emady, Heather (Committee member) / Arizona State University (Publisher)
Created2023
Description
Zwitterionic polymers, due to their supurior capability of electrostatically induced hydration, have been considered as effective functionalities to alleviate bio-fouling of reverse osmosis (RO) membranes. Bulk modification of polysulfone-based matrices to improve hydrophilicity, on the other hand, is favored due to the high membrane performance, processibility, and intrinsic chlorine resistance. Here a novel synthetic method was demonstrated to prepare zwitterionic poly(arylene ether sulfone) (PAES) copolymers, which was blended with native polysulfone (PSf) to fabricate free-standing asymmetric membranes via non-solvent induced phase separation process. Both the porosity of the support layer and surface hydrophilicity increased drastically due to the incorporation of zwitterion functionalities in the rigid polysulfone matrix. The water permeance and antifouling ability of the blend membranes were both remarkably improved to 2.5 Lm−2 h−1 bar−1 and 94% of flux recovery ratio, respectively, while salt rejection remained at a high level (98%) even under the high exposure to chlorine (8,000 ppm•h). Besides the preliminary blended membrane design, for the future membrane property enhancement, this dissertation also focused on polymer structure optimizations via elucidating the fundamentals from two perspectives: 1). Synthetic reaction kinetics and mechanisms on polycondensation of PAES. Interestingly, in combination of experiments and the computational calculations by density functional theory (DFT) methods in this work, only the aryl chlorides (ArCl) monomer follows the classical second-order reaction kinetics of aromatic nucleophilic substitution (SNAr) mechanism, while the kinetics of the aryl fluorides (ArF) reaction fit a third-order rate law. The third order reaction behavior of the ArF monomer is attributed to the activation of the carbon-fluorine bond by two potassium cations (at least one bounded to phenolate), which associate as a strong three-body complex. This complex acts as the predominant reactant during the attack by the nucleophile. 2). Optimized copolymer structures were developed for controlled high molecular weight (Mw ~ 65 kDa) and zwitterionic charge content (0~100 mol%), via off-set stoichiometry during polycondensations, following with thiol-ene click reaction and ring-opening of sultone to introduce the sulfobetaine functional groups. The structure-property-morphology relationships were elucidated for better understanding atomic-level features in the charged polymers for future high-performance desalination applications.
ContributorsYang, Yi, Ph.D (Author) / Green, Matthew D (Thesis advisor) / Lin, Jerry Y.S. (Committee member) / Lind, Marylaura (Committee member) / Perreault, Francois (Committee member) / Deng, Shuguang (Committee member) / Arizona State University (Publisher)
Created2019
Description
Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that are detected ubiquitously in the aquatic environment, biota, and humans. Human exposure and adverse health of PFAS through consuming impacted drinking water is getting regulatory attention. Adsorption using granular activated carbon (GAC) and ion exchange resin (IX) has proved to be efficient in removing PFAS from water. There is a need to study the effectiveness of commercially available sorbents in PFAS removal at the pilot-scale with real PFAS contaminated water, which would aid in efficient full-scale plant design. Additionally, there is also a need to have validated bench-scale testing techniques to aid municipalities and researchers in selecting or comparing adsorbents to remove PFAS. Rapid Small-Scale Column Tests (RSSCTs) are bench-scale testing to assess media performance and operational life to remove trace organics but have not been validated for PFAS. Different design considerations exist for RSSCTs, which rely upon either proportional diffusivity (PD) or constant diffusivity (CD) dimensionless scaling relationships.
This thesis aims to validate the use of RSSCTs to simulate PFAS breakthrough in pilot columns. First, a pilot-scale study using two GACs and an IX was conducted for five months at a wellsite in central Arizona. PFAS adsorption capacity was greatest for a commercial IX, and then two GAC sources exhibited similar performance. Second, RSSCTs scaled using PD or CD relationships, simulated the pilot columns, were designed and performed. For IX and the two types of GAC, the CD–RSSCTs simulated the PFAS breakthrough concentration, shape, and order of C8 to C4 compounds observed pilot columns better than the PD-RSSCTs. Finally, PFAS breakthrough and adsorption capacities for PD- and CD-RSSCTs were performed on multiple groundwaters (GWs) from across Arizona to assess the treatability of PFAS chain length and functional head-group moieties. PFAS breakthrough in GAC and IX was dictated by chain length (C4>C6>C8) and functional group (PFCAs>PFSAs) of the compound. Shorter-chain PFAS broke through earlier than the longer chain, and removal trends were related to the hydrophobicity of PFAS. Overall, single-use IX performed superior to any of the evaluated GACs across a range of water chemistries in Arizona GWs.
This thesis aims to validate the use of RSSCTs to simulate PFAS breakthrough in pilot columns. First, a pilot-scale study using two GACs and an IX was conducted for five months at a wellsite in central Arizona. PFAS adsorption capacity was greatest for a commercial IX, and then two GAC sources exhibited similar performance. Second, RSSCTs scaled using PD or CD relationships, simulated the pilot columns, were designed and performed. For IX and the two types of GAC, the CD–RSSCTs simulated the PFAS breakthrough concentration, shape, and order of C8 to C4 compounds observed pilot columns better than the PD-RSSCTs. Finally, PFAS breakthrough and adsorption capacities for PD- and CD-RSSCTs were performed on multiple groundwaters (GWs) from across Arizona to assess the treatability of PFAS chain length and functional head-group moieties. PFAS breakthrough in GAC and IX was dictated by chain length (C4>C6>C8) and functional group (PFCAs>PFSAs) of the compound. Shorter-chain PFAS broke through earlier than the longer chain, and removal trends were related to the hydrophobicity of PFAS. Overall, single-use IX performed superior to any of the evaluated GACs across a range of water chemistries in Arizona GWs.
ContributorsVenkatesh, Krishishvar (Author) / Westerhoff, Paul (Thesis advisor) / Sinha, Shahnawaz (Committee member) / Lind, Marylaura (Committee member) / Arizona State University (Publisher)
Created2020