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Catalytic processes are important and widely studied chemical processes aimed at making chemical reactions as efficient and environmentally friendly as possible. Heterogeneous catalysis involves the use of a generally highly porous, solid catalytic material with liquid or gaseous reactant molecules. Two important factors determining the overall performance of a heterogeneous catalytic material are the interactions of any species present during the process with the catalyst surface and the mass transport of said species through the porous network of the catalytic materials. Therefore, it is desirable to tailor the surface chemistry and pore structures of catalytic materials to exploit these factors and give catalytic materials with increased performance. An overview of the impact of mass transport and reactant-catalyst surface interactions are given in Chapter 1. In this thesis, Nuclear Magnetic Resonance (NMR) methods, amongst others, are used to quantitatively characterise mass transport through the pores of catalytic materials and also probe the strength of surface interactions between guest molecules and the solid surface. Pulsed-Field Gradient (PFG)-NMR and NMR relaxation are used to study diffusion and molecular dynamics of relevant molecules in the pores of porous materials with a particular focus on catalytic materials. As such an outline of such NMR methods are given in Chapter 2 as well as an evaluation and comparison of other methods used for the same purpose.

Symmetric flow batteries use a single electrolyte formulation instead of the usual two and offer simplified manufacture and operation, the possibility to use low-cost porous separators in place of ion-exchange membranes, and elimination of certain failure modes. Furthermore, using nonaqueous solvents in lieu of water enables exploration of redox species that support cell potentials beyond the electrochemical window of aqueous electrolytes. This thesis aims to assist in minimizing the levelized cost of storage for symmetric nonaqueous flow batteries through informed electrolyte development, materials selection, and device operation. Illustrating the large design space of flow battery electrolytes permits the definition of ``symmetric'' for the present application. A zero-dimensional model for flow batteries with porous separators is developed which incorporates self-discharge behavior. Coupling this model to technoeconomic equations reveals the basic tradeoffs inherent to using porous separators along with two promising active species approaches for symmetric flow battery electrolytes: salts of coordinated transition metal-ligand complexes and synthetically simple, soluble aromatic compounds used in a mixed electrolyte configuration. The technoeconomic analysis explores membrane cost/performance tradeoffs pertinent to symmetric systems using porous separators. Successfully implementing symmetric electrolytes of any composition requires original approaches to measurement and control of transport phenomena in the membrane due to shifts in relative contribution of different driving forces for crossover and self-discharge vs. traditional flow batteries. Real-time estimation techniques and reservoir balancing methods are developed to measure and control these convoluted phenomena. Common perceived failure modes of benchtop flow batteries and methods to deconvolute capacity fade mechanisms are discussed. The established nonaqueous redox-active species vanadium acetylacetonate is used as a representative compound to demonstrate that, counter to current literature, the primary failure mode of nonaqueous flow batteries is confined to resistance growth in the separator and not electrolyte or electrode degradation. Methods to further understand and mitigate this failure mode are discussed, and solubilities of cosolvent systems are explored to improve energy density. Iron bipyridine salts are revisited and found to succeed in symmetric flow battery operation subject to separator degradation constraints, prompting the study of more affordable counteranions.

Facilitated transport membranes (FTM) are a promising new class of materials for CO2-selective gas separation, with potential for application to post-combustion carbon capture and sequestration. FTM separation takes advantage of the chemical reactions of CO2 to increase throughput and selectivity, with potential for reducing costs and improving purity in the resulting gas streams. However, the process performance of FTM separation relies on material properties, determined by a complex chain of dependencies including polymer composition, water absorption, reactivity, and temperature, with the underlying physical processes not being fully understood. The development of new FTM materials is in turn limited by a lack of quantitative models and poor understanding of the microscopic mechanisms of FTM separation. This motivates the development of new theory and molecular models for estimating process performance and thermodynamic behaviour in this important class of materials. Unlike simple fluids, FTM systems exhibit multiple complex features which have limited the application of existing model frameworks. In this work, three key aspects of facilitated transport membranes are examined in order to build a predictive model of thermodynamics and phase equilibrium processes in FTM systems: (i) Thermodynamics of polymer melts and vapour-liquid equilibrium in polymer solutions are approached by both molecular simulation and theoretical models, in order to characterise the behaviour of polyvinylamine, a prototypical FTM polymer. Simulation of oligomers based on a TraPPE-UA molecular model are found to produce good quality rho p T data for common polymers, and a hybrid simulation / equation of state approach is proposed for predicting polymer properties. By substituting experimental measurement with molecular simulation, equation of state models are obtained with PC-SAFT even where the real polymer is thermally unstable or experimentally inaccessible. (ii) The aqueous-organic electrolyte solution originating from amine-CO2 is considered based on theoretical and simulation approaches, with significant shortcomings found in current models. New molecular parameters are proposed for aliphatic ammonium chlorides and bicarbonate, optimized against experimental phase equilibrium data, allowing CO2 solubility in aqueous amine systems to be simulated at varying stages of absorption. (iii) The reactive aspects of CO2 absorption in aqueous amine solutions is examined in light of literature approaches. A new hybrid methodology is proposed, using infinite dilution experimental data in combination with molecular simulation utilizing the newly optimised molecular models. Together, advancements in the three aspects outlined above permit description of facilitated transport membranes by molecular simulation, and in turn parametrisation of equation of state models for reactive polyamine systems. The knowledge gained for polymer-solvent systems, electrolytes, and reactive gas absorption allow prediction of material properties and process performance of FTM polymers. Here, the quaternary system PVAm - H2O - CO2 - N2 is examined as a prototypical post-combustion FTM system, in order to chart the dependence of process performance on operating conditions. These advances inform future application of associating equations of state to amine-based facilitated transport membranes in particular, as well as the wider field of reactive electrolyte systems.

In recent years, anaerobic digestion of biomass and food wastes/residues to produce biogas has become one of the most attractive routes for producing renewable energy. Biogas mainly consists of methane (CH4, 40-75 vol.%) and carbon dioxide (CO2, ca. 25-60 vol.%). To enable the maximum utilisation of biogas, CO2 removal is necessary. Therefore, this project developed a novel integrated membrane-catalytic process for biogas upgrading, which consists of a membrane separation technology (to capture the CO2 from biogas) coupled with non-thermal plasma (NTP) activated catalysis (to convert the captured CO2 into CH4), enabling methane enrichment. The development of the individual processes was undertaken first. Specifically, a new method was developed to modify SAPO-34 zeolite membrane (using nanoporous organosilica) to heal of the membrane defects, and the developed membrane unit showed an improved CO2/CH4 selectivity (from ca. 60 to 160) without compromising the CO2 permeance. Then, the development of highly efficient catalysts (based on zeolites and MOFs) for the NTP-catalysis system was performed for CO2 hydrogenation. For example, under NTP at 6 kV, the Ni (15 wt.%) supported on UiO-66 MOF catalyst showed a good CO2 conversion (ca. 80%) and CH4 selectivity (ca. 99%). In addition, in situ techniques, such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterisation, and kinetic studies were carried out to investigate the mechanism of the NTP-catalysis based on the CO2 hydrogenation reaction. At the laboratory scale, the integration of membrane separation with NTP-catalysis was successfully achieved to realise the CH4 enrichment of synthetic biogas. The integrated system showed satisfactory carbon capture efficiency (CCE) and carbon utilisation efficiency (CUE) of ca. 91.8% and 71.7%, respectively, as well as the good stability (40 h).

Sustainable energy supply and environmental protection are the major global scientific challenges in the 21st century, such as greenhouse gas capture, natural gas production, desalination of seawater for clean water production. Membrane separation technology offers attractive energy-efficient and environmental-friendly solutions to these challenges. This PhD thesis is focused on design and fabrication of membranes from novel molecularly defined polymers and understanding their physical properties, particularly the transport properties of gas molecules in polymer membranes. First, we demonstrate a simple approach of fabricating novel polymer nanocomposite membranes using established colloidal science. Crystalline microporous zeolitic imidazolate frameworks (ZIFs) nanocrystals are incorporated into a polyimide polymer matrix via solution mixing. The resulting nanocomposite membranes show excellent dispersion of nanoparticles, good adhesion at the interface, and enhanced gas permeability while the selectivity remain at high level. We then fabricated membranes from novel microporous polymers, polymers of intrinsic microporosity (PIMs). Using the PIM-1 polymer as a prototype, we discovered that ultraviolet irradiation of PIM-1 membranes in the presence of oxygen induces oxidative chain scission at the surface, resulting in local densification and structural transformation of free volume elements. Consequently, the membrane become asymmetric with a more gas-selective layer formed at the surface, while the overall permeability maintains at high level. Finally, we report a simple thermal oxidative crosslinking method to tailor the architecture of channels and free volume elements in PIM-1 polymer membrane by heat treatment in the presence of trace amounts of oxygen molecules. The resulting covalently crosslinked polymer networks offer superior thermal stability, chemical stability, reasonable mechanical strength, and enhanced rigidity. Most important of all, thermally crosslinked PIM-1 polymer membranes show significantly enhanced molecular sieving functions that yield remarkably high selectivity and high gas permeability, which surpass the upper bound that has been limiting the polymer membranes for decades. We also demonstrate that the thermal crosslinking method is effective for crosslinking of nanocomposite membranes with porous or nonporous fillers. These microporous molecular sieve membranes are promising for a wide range of molecular-level separation applications.

The goal of this PhD thesis is to develop materials that incorporate functionalized ionic liquids (ILs) and deep eutectic solvents (DESs) for CO2 removal from low CO2 concentration environments such as cabin air in spacecrafts and International Space Station, ISS, (< 5000 ppm of CO2). CO2 removal from such environments, especially in microgravity, requires certain considerations in material development such as light weight, small footprint, and long-life to enable sustainability in space which is a goal of the Artemis Program of the United States National Aeronautics and Space Administration (NASA). Current carbon dioxide removal assembly (CDRA) used by NASA utilizes porous solid sorbents called zeolites. Zeolites, similar to other solid sorbents based on metal organic frameworks, adsorb CO2 upon contact with air and release it upon increase in temperature (e.g., 350 °C). This process, referred as thermal-swing, is energy intensive and the repeated adsorption-desorption cycle creates fracture in the solid sorbent, thus resulting in dusting issue that damages downstream equipment in spacecraft and ISS. Therefore, there is a need of alternative materials that are selective to CO2, benign, lightweight, durable, and that require minimal energy to regenerate. ILs and DESs are of interest since they have tunable properties, and they are regarded as stable and ‘green’ solvents. However, handling of liquids in microgravity is a challenge. Therefore, liquids require structural frameworks in order to be utilized in space applications. In this thesis, we demonstrate the design of functionalized ILs and DESs as environmentally benign energy-saving CO2 capture sorbents. These sorbents are immobilized in two different structural supports: polymeric capsules and membranes. Encapsulation of the selective ILs and DESs not only enable their handling in microgravity, it also provides large surface area for CO2 absorption. The liquid capsules can be used in the packed-bed CO2 scrubbing column of the CDRA and operate under milder thermal-swing conditions than that of zeolites. Our study also shows that the encapsulated ILs maintain their CO2 capacity under moist conditions whereas zeolites lose their selectivity to CO2 in the presence of moisture. Due to this loss of selectivity by zeolites, CDRA uses a silica gel column to first remove the water from the air. Therefore, the use of IL capsules can eliminate the need of this additional pre-column of silica. Alternative to sorbents and thermal-swing process, membranes operate continuously. Here, we developed a facilitated transport membrane (FTM) where the IL and poly(IL) act as the CO2 carriers that complex with CO2 on the feed site, diffuse according to the concentration gradient within the selective layer of the membrane, and release CO2 on the permeate side. The concentration gradient across the membrane is created by continuously removing the CO2 on the permeate side by a sweeping gas or by pulling vacuum. The sweeping gas can be hydrogen since the separated CO2 from the CDRA unit is fed to the Sabatier reactor where CO2 reacts with hydrogen to form water along with the side product of methane. Alternatively, CO2 can be disposed by pulling vacuum which is free in space. The developed materials can be adapted for CO2 removal from indoor environments such as office and submarine cabin where the CO2 level needs to be below 5,000 ppm for normal daily activities, as recommended by National Institute for Occupational Safety and Health (NIOSH) and Occupational Safety and Health Administration (OSHA)’s recommended exposure limits (RELs)1. Likewise, these materials present very high selectivity to CO2 and therefore, they are promising for direct air capture (DAC) where the CO2 is even lower (410 ppm). DAC is a process considered a Negative Emissions Technology, differently than emission mitigation technologies such as the post-combustion carbon capture. Solid sorbents and alkali solvents have been considered for DAC, however, membranes have not been studied to the same extend because most membranes are solution-diffusion type and cannot concentrate CO2 from such low partial pressures in air. This thesis work demonstrates, for the first time, FTM type membrane that is suitable for separation of CO2 from air owing to the very thin selective layer composed of the IL and poly(IL) carriers that facilitate CO2 transport.

Abstract: Treating contaminated hot streams is essential to reduce water cooling/re-heating needs and greenhouse gas emission in water reclamation processes, such as the Canadian in-situ oil-sand extraction processes that produce contaminated water at 80-90 C. Membrane separation processes have become one of the fastest growing methods for the desalination and treatment of water because they cost less, are more compact, and produce higher quality water than conventional processes. At the heart of this processes is the membrane. Thin film composite (TFC) membranes are the most common choices due to their high water recovery and contaminant rejection rates. However, commercially available TFC membranes do not perform well above 45 C. The objective of this PhD thesis is to make new classes of TFC polymeric membranes with high permeability and separation performance at high water temperatures. First, a novel reverse osmosis (RO) TFC membrane with enhanced thermal stability was made to address the limitation of available commercial TFC membranes. The goal was to make a new polymer with a rigid network, and therefore higher temperature resistance, as the selective layer. To reach this goal, triaminopyrimidine (TAP, a multifunctional amine) was added to the usual combination of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) to crosslink the polymeric structure. The TAP-modified membranes had higher permeabilities and consistent permeate fluxes for 9 hours at high temperatures. These polymers were used to develop novel highly permeable and robust forward osmosis (FO) membranes. TAP-modified FO TFC membranes mediated with polydopamine (PDA)/graphene oxide (GO) interlayers were synthesized. The presence of an interlayer and a low reactive monomer (TAP) slowed down the interfacial polymerization, leading to forming a permeable, selective, and thermally stable polyamide layer. I also added nanodiamond (ND) particles with high thermal resistance into the polyamide layer. The surface of the ND particles was modified with MPD to covalently bond them in the polymer matrix. Thin film nanocomposite (TFN) membranes prepared with ND particles overcame the trade-off between water flux and NaCl rejection, and showed less flux decline at high temperature compared with a polyamide commercial membrane. In the next phase of this development, amine-modified ND particles were added to the polyamide layer to change its surface chemistry. The ND particles reduced fouling of the TFC membranes with sodium alginate (SA) and bovine serum albumin (BSA) foulants by decreasing the electrostatic and hydrophobic interactions between foulants and the membrane surface, and by reducing the membrane roughness. Finally, we provided guidelines to test TFC membrane at high temperatures. The performance of three commercial RO membranes were evaluated with a series of high-temperature filtrations including long-term operation, cyclic tests, controlled step-wise temperature increments, and permeability tests.

A vibratory nanofiltration (NF) system was investigated for the preconcentration of coffee extracts for soluble coffee production. The simulated coffee extracts studied contained mostly suspended and colloidal organic components that, although were effectively rejected by the NF membrane (>99% turbidity rejection), affected the vibratory NF performance. The vibratory NF operation improved permeate flux, rejection efficiencies, and reduced flux decline from those observed in crossflow (CF) operation. Further, the effects of applied transmembrane pressure (TMP) and vibrational frequency (F) at corresponding displacement (d) were investigated and modeled. A semi-empirical resistance-in-series model was employed to characterize the mass transfer mechanism, osmotic pressure effects, and fouling resistances that affected the vibratory NF performance. Response surface methodology (RSM), in conjunction with a Box-Behnken experimental design, was also employed to develop statistical models and determine optimal operating conditions (TMP = 3.79 MPa, F = 54.7 Hz, d = 3.18 cm). Lastly, scale-up design, economic, and environmental assessment for a 3% feed coffee extract corresponded to a 7-module i84 VSEP filtration system recovering 379,500 L of reusable water per day, a capital cost of $2,100,000 with estimated annual savings of $481,900 per year, a payback period of 10 years, and a potential to reduce the environmental emissions of the process by approximately 40%.

The pulp and paper industry traditionally consumes high levels of water and energy and the reduction of fresh water use with emphasis on process water management and wastewater recycling are key factors for the growth of this industry. The use of fresh water has reduced significantly during the last decades. The main reasons for this include increased environmental legislations relating to effluent discharge, and hefty costs arising from either the supply of fresh water or treatment of wastewater thus effecting the marketing potentials. Although using recovered paper as raw material has an advantage of saving energy, water and landfill space, attention needs to be paid to treating the wastewater due to discharge regulations and standards. Wastewater sent to a treatment facility is regarded as waste. It is treated only with the purpose not to cause a negative impact to the environment. Although the level of impurities and toxic substances in treated wastewater satisfies the discharge standards, it often limits recycling potential because it adversely affects manufacturing processes and paper quality. Methods for removing these impurities and toxic substances include various physical and biological methods and the intended reuse of the water determines type and level of treatment required. This study aims to explore the possibility of introducing advanced technologies such as enhanced coagulation and flocculation, and membrane separation to improve wastewater recycling in a commercial paper mill. A commercial plant water circuit was first analysed and a water balance was proposed to reduce the water consumption from 10m3 to 6m3/tonne product. The quality of treated wastewaters and associated parameters from commercial individual processes were analysed to forecast the plant influent flows and predict pollutants concentrations in wastewater. Although organics in wastewater were mostly processed through biodegradation, non-biodegradable recalcitrant compounds limit its potential for reuse, thus a tertiary treatment is proposed. Enhanced coagulation and flocculation yielded very promising results, especially for colour removal. The treatment was able to achieve the target colour value. The desirable COD output values were also achieved by varying coagulation/flocculant ratio. For membrane separation, different units of operation and pollution parameters were examined. Results indicate that membrane technology produced higher colour removal efficiencies (96% for NF and 87% for UF) compared to enhanced coagulation and flocculation (61%). However, when it comes to removing COD, enhanced coagulation and flocculation was able to achieve a removal efficiency of 46% COD, compared to 43% for NF and 20% for UF. Amongst the three methods, UF, if used as a stand-alone method, failed to reduce the COD level to the target value. However, when feedwater was pre-treated with coagulant, UF was able to produce a similar COD removal rate to NF. Pre-treating feedwater also reduced fouling of membranes. Between the two membrane cleaning agents used, alkaline was shown to be more effective in reducing fouling. Backwashing was also investigated and found to be effective in prolonging membrane lifespan. However, despite the reduction in fouling, irreversible fouling still happened. Although membrane technology performed better in the removal of colour, retrofitting a membrane system into an existing plant can be difficult, requires the implementation of appropriate pre-treatment technology to control fouling resulting in higher capital and operating costs compared to enhanced coagulation and flocculation.

Membrane distillation is an emerging technology for treating hydraulic fracturing flowback and produced waters. Suppression of membrane fouling by inorganic and polar and non-polar organic compounds is a challenge. Here polyhydroxyethyl methacrylate, polyacrylic acid, polvinylallyl imidazolium bromide and polyvinylhexyl imidazolium bromide chains have been grafted from the membrane surface. Fouling is initially due to adsorption of organic compounds followed by scale formation. When challenged with produced water, membranes modified with polvinylallyl imidazolium bromide chains provided the greatest resistance to fouling. For EC pretreated produced water and synthetic produced water that contained mainly inorganic species, the flux decline was much less.

Diblock copolymers (BCPs) are very useful materials that can phase-separate to form a variety of highly ordered nanostructures. The lamellar structure and the gyroid structure get special attention due to their potential applications in the lithographic patterning and membrane separation processes, respectively. Devices made of microelectronics have become an essential part of our lives. The continuous improvement that we enjoy in microelectronics is greatly owing to progress in the photolithographic patterning technique. Photolithography has enabled shrinking the feature size in microelectronics, but it has reached a resolution limit of ~ 40 nm half-pitch. Therefore, development of higher-resolution patterning techniques is required to enable manufacturing next-generation microelectronics. Directed self-assembly (DSA) of lamella-forming BCPs offers one promising approach. Microdomains with sub-10 nm half-pitch can be readily obtained using high χ silicon-containing BCPs. The continuing demand for decreasing the feature size provided the motivation to synthesize, characterize and utilize BCPs with sub-5 nm half-pitches for making DSA patterns. Scarcity of clean water resources has become a global challenge. Membrane separation technology provides an efficient and low-cost approach to producing clean water. The increasing demand for clean water requires improvements in current membranes. Membranes made from BCPs are believed to offer a path to both high permeability and high selectivity due to their high porosity and narrow pore-size distribution. A porous gyroid structure has continuous pore channels that span the entire thickness of BCP layer without alignment. Therefore, self-assembly of gyroid-forming BCPs is a particularly attractive approach to creating water ultrafiltration membranes with improved performance. In this work, lamella-forming BCPs with sub-5 nm half-pitch microdomains were synthesized and their orientation behaviors in thin films using the bottom and top surface treatments were investigated. The perpendicular lamellar structure was obtained and the line-space DSA pattern was demonstrated. A synthetic process was established to reproducibly make gyroid-forming BCPs with different χ values. Gyroid composite membranes were made from one of the gyroid-forming BCPs by a newly developed process. The performance of these gyroid composite membranes for water ultrafiltration was tested. The membrane provides a proof of concept demonstration of high permeance and a molecular weight cut-off.

Tackling the worldwide severe water shortage, the membrane technology is considered to be the most efficient approach and hence, used widely as a cost-effective sustainable solution. “Forward osmosis (FO)” has been the major attention in recent time. FO uses osmotic pressure as the driving force to draw the water passing the membrane and achieve the desired separation performance. In general, it is considered to be a process with tremendous potential to resolve the present-day water shortage with extremely low energy consumption. However, the challenges of membrane and draw solution regeneration associated with FO processes must be conquered prior to their large-scale application. In this study, we demonstrated several approaches to enhance the antifouling and FO performance by improving the constituent material as well as developed a novel thermo-responsive process with economic regeneration of the draw solution. The surface charge and fouling adsorption mechanism have been tuned by introducing Polyethylenimine (PEI) on the membrane. Zwitterionic monomer, AEPPS was used to introduce the polyamide layer by conventional in-situ modification and second interfacial polymerization (SIP), respectively. The excellent antifouling surface was verified using a series of fouling test with charged protein adsorption, bacterial adhesion, model secondary wastewater effluents, and hydraulic fracturing produce water. Beyond the surface decoration, the ultra-thin graphene oxide (GO) FO membrane was fabricated by pressure-assisted self-assembly (PASA). The nanostructure alteration inside the GO layer and crosslinking mechanism was investigated, which could provide a significant advancement to GO material development in the future. Also, we proposed a novel thermo responsive draw solution, which is synthesized from natural and non-toxic material, chitosan. Along with the temperature control, the free volume of the draw solute showed a stable and repeatable change in confirmation. This draw solution has very good prospect to be employed in bio or food-related separation application. This work is an overall FO process research, which not only enhanced the FO performance and antifouling properties but investigated the material science in detail. Although FO processes are developing and several obstacles are yet to be resolved in terms of large-scale applications, the prospect of commercialization of FO for niche application is expected.

Ionic liquids represent an emerging attractive material in membrane technology. The central theme of this doctoral dissertation is to develope novel membranes using ionic liquids. Two different approaches were used to prepare ionic liquid membranes including the immobilization of ionic liquid within the membrane pores or the use of pressure assembly method to deposit a selective ionic liquid layer on the top membrane surface. In chapter 2, imidazolium ionic liquids with three different alkyl halides were successfully synthesized and used to prepare supported ionic liquid membranes (SILMs). SILMs preraper were tested for aqueous and nonaqueous applications. For nonaqueous applications, the trend of separation was found to be divinylbenzene>styrene>toluene, which was attributed to the extended conjugation of π electron cloud. For nonaqueous system, preferential separation of different dyes was achieved. In chapter 3, SILMs have been tested for the fractionation of organic compounds. Fractionation of a feed stream consisting of benzene, naphthalene, and phenanthrene in tetradecane and cis- and trans-stilbene in hexane were investigated. Differences in the π electron cloud density of the aromatic solutes influence their interactions with the imidazolium cation which can affect the rates of transport. In the case of the three aromatic solutes the degree of conjugation and molecular weight increase in the order of benzene, naphthalene, and phenanthrene. However, for cis-and trans-stilbene, the mass transfer coefficient was larger for all three ionic liquids. Aqueous SILM was used as the liquid membrane phase to fractionate two nucleobases: thymine and cytosine in water. The mass transfer coefficient for thymine was 5.5 times greater than cytosine indicating the possibility of exploiting multimodal interactions fractionate compounds. Chapter 4 constitutes the preparation of novel polyionic liquid augmented membranes that were fabricated using pressure assisted self-assembly and employed for π- electron cloud mediated separation of aromatics from their aliphatic homologs. The prepared membranes can be employed for the fractionation of aromatics such as benzene, toluene, p-xylene, nitrobenzene. Further, these augmented membranes were demonstrated to have preferential separation of one stereoisomer over others. Finally, chapter 5 includes conclusions drawn out of this research and future directions and recommendations.

A case study has been conducted for the recovery of water from complex wastewater at a soluble coffee manufacturing factory. The study has evaluated separation methods for process intervention based on environmental and economic assessments. Water recovery was identified in two possible wastewater streams at the factory: the overall plant effluent and an intermediate stream before it enters on-site pre-treatment. A novel vibratory field membrane separation was tested at the laboratory scale using real factory wastewater and scaled-up using appropriate design protocols. Recovery of water from the intermediate stream proved the most effective, both environmentally and economically. The full-scale vibratory membrane process recovers 100,000 gallons of water per day that meets specifications for the factory cooling tower. The proposed design reduced the daily well water with draw by 21% and the amount of wastewater discharged from the factory by 28.5%. Annual operating costs were reduced by 22.5% and total life cycle emissions were reduced by 27.8%. These reductions are mainly the result of the reduced volume of wastewater discharged from the factory and the reduced energy requirement of the on-site pre-treatment processes. The vibratory membrane process for water recovery presents favorable economics, even after capital costs are considered. The net present value after 10 years is $485,300, while the payback time is under three years.

Graphene oxide is a single layer of carbon atoms with decorated oxygen functional groups. Stacked monolayers in the laminate form create an interlayer space of sub-nanometer scale with oxygenated functional group to attract water molecules, and graphitic domains to allow frictionless flow of water molecules and achieve maximum efficiency of water transportation. The research reported herein is aimed to understand and explore characteristics of the diffusion-dependent mass transportation across an array of cascading nanochannels confined by graphene oxide laminates at sub-nanometer level. This dissertation has 6 Chapters. Chapter 1 is the introduction and Chapter 2 reports the recent progress in graphene oxide for mass transport application. Chapter 3 discusses efforts of engineering the channel confinement, which is represented by the interlayer spacing in between graphene oxide laminates. By adjusting the fundamental factors of graphene oxide suspension, the interlayer spacing can be controlled at 0.7 to 0.8 nm. Based on the engineered interlayer spacing, separation of vaporous mixture by graphene oxide membrane is studied in Chapter 4. Numerical description of nanochannels enclosed by graphene oxide monolayers is determined by time lag analysis. The feature of ethanol vapor transportation with the support of water vapor is revealed, showing accelerated transportation of non-permeable matter, which enriches the existing knowledge. A geometrical model of graphene oxide membrane for vapor separation was established and analyzed. In Chapter 5, adsorption and intercalated of molecules and solvated ions are studied and proved as a size-dependent enlargement of graphene oxide nanochannels. Carriers such as water and ethanol are used for transporting ions and molecules into graphene oxide slits. Taking the adsorption into consideration, permeation of vaporous substances through adsorbed graphene oxide membrane is investigated in Chapter 6. The research initiates researching crystallization of adsorbed matters in graphene oxide interlayer structure. A simplified model was directed to predict the water vapor permeation behavior of intercalated graphene oxide membrane. Such efforts not only lead to a better understating of graphene oxide membrane for gas separation but also give a hint of spatially efficient matter transport in achieving excellent electrochemical devices with graphene oxide components.

Abundant, inexpensive, high purity molecular hydrogen as a medium for energy distribution is potentially enabling for adoption of alternative electricity generation schemes. Steam reforming of natural gas remains the dominant method of producing large amounts of hydrogen. However, this process also creates by-products, most notably, carbon monoxide and carbon dioxide. Separation to ultra-high purity hydrogen from these syngas reformate streams by traditional methods, such as pressure swing absorption, has its disadvantages including long cycle times, contamination and a large equipment footprint. Alternative methods of hydrogen separation, such as electrochemical pumping, are a viable alternative to this separation dilemma due to their relative simplicity and potential efficiency. The solid-state proton conductor cesium dihydrogen phosphate has shown potential in electrochemical hydrogen separation devices operating on reformed hydrocarbons. In this work, we have synthesized a suite of nanoparticles, including Pt, Pd, Ru, Ni and Cu, supported on carbon for implementation in solid acid electrodes. We evaluate these materials at an intermediate temperature of 250 degrees Celsius for the hydrogen oxidation and reduction reaction, as well the electrooxidation of carbon monoxide. Functionally graded anodes are fabricated to balance CO conversion activity with hydrogen oxidation. These re-engineered anodes are implemented in conjunction with Ni-based cathodes to demonstrate efficient hydrogen separation using ultra low loadings of Pt from syngas-like inputs.

Adsorption, separation and conversion of CO₂ from industrial processes are among the priorities of the scientific community aimed at mitigating the effects of greenhouse gases on the environment. One of the main focuses is the capture of CO₂ at stationary point sources from fossil fuel emissions using porous crystalline materials. Porous crystalline materials can reduce the energy costs associated with CO₂ capture by offering high adsorption rates, low material regeneration energy penalties and favorable kinetic pathways for CO₂ separation. MOFs consist of polymeric inorganic networks with adjustable chemical functionality and well-defined pores that make them ideal for these applications. The objective of this research was to test the potential for CO₂ capture on Zn-based MOFs by studying their sorption, transport and gas separation properties as adsorbents and continuous membranes. Three Zn-based MOFs with open Zn-metal sites were initially studied. Zn4(pdc)4(DMF)2•3DMF (1) exhibited the best properties for CO₂ capture and was investigated further under realistic CO₂ capture conditions. The MOF exhibited preferential CO₂ adsorption based on a high enthalpy of adsorption and selectivity of CO₂ over N₂ and CH₄. Sorption dynamics of CO₂ indicated fast adsorption and a low activation energy for sorption. Diffusion inside the pores is the rate-limiting step for diffusion, and changes in the process temperature can enhance CO₂ separation. Desorption kinetics indicated that CO₂ has longer residence times and lower activation energies for desorption than N₂ and CH₄. This suggests that the selective adsorption of CO₂ is favored. MOF/Polymer membranes were synthesized via a solvothermal method with structural defects sealed by a polymer coating. This method facilitates the permeation measurements of materials that cannot form uniform-defect-free layers. The membrane permeation of CO₂, CH₄, N₂ and H₂ exhibited a linear relation to the inverse square root of the molecular weight of the permanent gases, indicating that diffusion occurs in the Knudsen regime. Permselectivity was well-predicted by the Knudsen model with no temperature dependence, and transport occurs inside the pores of the membrane. MOF (1) exhibits ideal properties for future applications in CO₂ capture as an adsorbent.

Reverse osmosis (RO) promises to play an increasingly crucial role in water supply, especially via desalination. One of the major problems faced by RO technology is the decline in membrane performance due to concentration polarisation (CP) and fouling. CP increases the osmotic pressure gradient across the membrane, hence reducing the net driving pressure gradient. Moreover, CP increases the probability of fouling. An electro-osmosis technique is proposed in this thesis which has the potential to reduce CP because it induces the movement of fluid in the vicinity of membrane, thus improving mixing within the boundary layer and enhancing mass transfer. Computational Fluid Dynamics (CFD) is used to simulate steady and unsteady electro-osmotic flow (EOF) in 2D unobstructed and obstructed channels. First, a mathematical simplification of EOF is developed that reduces the required computational load while retaining the model’s accuracy and physical meaning. It is shown that EOF can be mimicked using a slip velocity. The results from CFD are found to be in good agreement both with published data and with more rigorous simulation approaches. For steady EOF in unobstructed channels, the spatial variation in slip velocity is found to be the driver for mass transfer enhancement. For uniform-unsteady EOF in unobstructed channels, a sinusoidal time-varying electro-osmotic slip velocity has negligible effect on the time-averaged hydrodynamics and mass transfer, because the effect is nullified within the time oscillation period. Nevertheless, there are still benefits for using unsteady EOF for fouling reduction/prevention, as increases in slip velocity frequency and amplitude increase the maximum wall stress which is a proxy for fouling reduction. For unsteady EOF in spacer-filled channels, the simulation results show that an oscillating slip velocity has the potential to induce vortex shedding. This occurs when a resonant slip velocity frequency is used for Reynolds numbers near the transition from steady to unsteady flow.

The advent of next generation sequencing (NGS) has fundamentally changed genetics research. Where researchers were once focused on sequencing the genome of a species, they now can sequence the genome of a particular tumor or even a single cell. NGS has also made it cost effective to sequence the RNA transcripts found within a cell, a collection of data known as the transcriptome. Unfortunately, current protocols for sequencing the genome and the transcriptome are incompatible. This leaves researchers with a choice: for a given sample you can examine either the DNA or the RNA. The work presented here makes it so that researchers no longer have to make this choice. This dissertation describes the development of a new protocol, known as Gel-Seq, that makes it possible to sequence both DNA and RNA from as few as 400 cells. This technology will allow researchers to directly examine the ways that changes in the genome impact the transcriptome. At the heart of the Gel-Seq protocol is the physical separation of DNA from RNA. This separation is achieved electrophoretically using a newly designed combination of polyacrylamide membranes that take advantage of the size differences between these molecules.Two different device options were developed as a part of the Gel-Seq protocol. One device, designed for rapid adoption, was fabricated using standard equipment found inside of a biology laboratory. The second device, designed for separating low input samples, was fabricated using newly developed micro-scale fabrication techniques. In addition to the development of these physical devices, a biological protocol was developed to generate genome and transcriptome data using these devices. In order to validate this technology, a cell line with a stable genome and transcriptome was used. Comparing the Gel-Seq protocol to standard protocols, the results showed a high correlation for both the genome (R = 0.88) and transcriptome (R = 0.96) data. This supports the conclusion that the device can be used to produce correlated genome and transcriptome libraries. This dissertation reports on the development, optimization, and validation of the Gel-Seq protocol.

Microporous zeolite membranes have been widely studied for molecular separations based on size exclusion or preferential adsorption-diffusion mechanisms. The MFI-type zeolite membranes were also demonstrated for brine water desalination by molecular sieving effect. In this research, the pure silica MFI-type zeolite (i.e. silicalite) membrane has been for the first time demonstrated for selective permeation of hydrated proton (i.e. H3O+) in acidic electrolyte solutions. The silicalite membrane allows for permeation of H3O+ ions, but is inaccessible to the large hydrated multivalent vanadium ions due to steric effect. The silicalite membrane has been further demonstrated as an effective ion separator in the all-vanadium redox flow battery (RFB).The silicalite is nonionic and its proton conductivity relies on the electric field-driven H3O+ transport through the sub nanometer-sized pores under the RFB operation conditions. The silicalite membrane displayed a significantly reduced self-discharge rate because of its high proton-to-vanadium ion transport selectivity. However, the nonionic nature of the silicalite membrane and very small diffusion channel size render low proton conductivity and is therefore inefficient as ion exchange membranes (IEMs) for practical applications. The proton transport efficiency may be improved by reducing the membrane thickness. However, the zeolite thin films are extremely fragile and must be supported on mechanically strong and rigid porous substrates. In this work, silicalite-Nafion composite membranes were synthesized to achieve a colloidal silicalite skin on the Nafion thin film base. The “colloidal zeolite-ionic polymer” layered composite membrane combines the advantages of high proton-selectivity of the zeolite layer and the mechanical flexibility and low proton transport resistance of the ionic polymer membrane. The composite membrane exhibited higher proton/vanadium ion separation selectivity and lower electrical resistance than the commercial Nafion 117 membrane. The high proton transport selectivity is a result of the molecular sieving effect between the H3O+ and multivalent vanadium ions by the zeolitic pores; thus the zeolite particles significantly reduced the effective membrane surface area for vanadium ion permeation. The low resistance of the composite membrane can be attributed to the reduced thickness of the Nafion base film and the thinness of the colloidal silicalite top layer. The composite membrane outperformed the Nafion 117 membrane in the vanadium RFB operation in terms of the overall charge-discharge energy efficiency. Efforts have been made in further investigation of ion and molecular transport diffusivity in the polycrystalline silicalite film using zeolite-coated optical fiber interferometers. A physical model has been established for analyzing the molecular diffusivity in the zeolite layer based on the temporal responses of the optical interferometric signals during the transient process of molecular sorption. Experiments were first carried out to study the diffusivity of isobutane to evaluate the effectiveness of the proposed optical method. The isobutane diffusivities in silicalite measured by this method were in good agreement with the values reported in literature. The zeolite coated fiber optic interferometer was however ineffective in monitoring ion sorption or ion exchange in the silicalite films. It is suggested that more sensitive fiber optic devices are needed for studying the ion diffusion.

The development of functionalized membranes with tunable pores and catalytic properties provides us an opportunity to manipulate the membrane pore structure, selectivity and reactivity. By introducing the functional groups into membrane pores, dissolved metal ions and reactive particles can be effectively immobilized within the polymer matrix for toxic chloro-organic and heavy metal remediation in water. A polyelectrolyte functionalized membrane platform with tunable pore size and ion exchange capacity has been developed for iron/iron oxide nano-catalyst synthesis and chlorinated organic compound (trichloroethylene, TCE and polychlorinated biphenyls, PCBs) degradation. Highly robust polyvinylidene fluoride (PVDF) microfiltration membranes are used as the support with cross-linked polyacrylic acid (PAA) filled in the pores. By varying the environmental pH, PAA hydrogels have either swelling or collapsing behavior, resulting in different effective membrane pore sizes for different separation purposes. Cation exchange groups (i.e. carboxyl groups) in PAA chains prevent the aggregation and leaching of nanoparticles (NPs) during in-situ synthesis and reaction. Depending on the catalyst loading and residence time, TCE and PCBs can be completely degraded by reduction of zero-valent iron and bimetallic iron/palladium NPs, or iron oxide catalyzed free radical oxidation at near-neutral pH. Biphenyl from PCB dechlorination can be further oxidized by hydroxyl radicals (OH•) generated from hydrogen peroxide (H2O2) decomposition. Hydroxybiphenyls and benzoic acid are identified as oxidation products. Line scan and elemental mapping in transmission electron microscopy (TEM) and X-ray photo electron spectroscopy (XPS) characterizations are conducted to understand the effect of iron surface transformation on NP reactivity, and to optimize the membrane functionalization. The same platform can also be used to remove toxic metal selenium in the scrubber water of coal-fired power plants. By reducing the salt concentration in water or increasing the residence time and temperature, the concentration of selenium oxyanions in functionalized membrane permeate can be reduced to less than 10 µg/L. Selenium is captured in membranes by both iron reduction to metallic selenium and iron oxide adsorption. The full-scale flat sheet functionalized membrane and spiral wound modules have also been developed. Iron NPs with alterable loadings are successfully synthesized inside the membrane module for real water applications.

Studies were conducted to evaluate the impact of landfill leachate discharge on the operation of waste water treatment plants (WWTPs). Two aspects of interferences were found: one is UV quenching substances, which are bio-refractory and able to penetrate the biological treatment processes, consequently interfere the UV disinfection in WWTPs. The other one is organic nitrogen, which can pass the nitrification-denitrification process and contribute to the effluent total nitrogen (TN). Also, treatability study was conducted for landfill gas (LFG) condensate. In a laboratory study, leachate samples were fractionated into humic acids (HA), fulvic acids (FA) and Hydrophilic (Hpi) fractions, the specific UV254 absorbance (SUVA254) of the three fractions follows: HA > FA > Hpi. However, the overall UV254 absorbance of the Hpi fraction was important because there was more hydrophilic organic matter than humic or fulvic acids. It was found that the size distribution of the three fractions follows: HA > FA > Hpi. This indicates that membrane separation following biological treatment is a promising technology for the removal of humic substances from landfill leachates. Leachate samples treated in this manner could usually meet the UV transmittance requirement of the POTWs. Also, nitrogen species in landfill leachates under various stabilization states were investigated. Although the effect of landfill stabilization state on the characteristics of organic matter and ammonia is well documented, there are few investigations into the landfill leachate organic nitrogen under different stabilization stages. Ammonia was found to leach out slower than organic matter and can maintain a constant level within the first a couple of years (< 10 years). The concentration and biodegradability of organic nitrogen were found to decrease with landfill age. A size distribution study showed that most of organic nitrogen in landfill leachates is < 1 kDa. The protein concentration was analyzed and showed a strong correlation with the organic nitrogen. Different slopes of regression curves of untreated and treated leachates indicate that protein is more biodegradable than the other organic nitrogen species in landfill leachates. XAD-8 resin was employed to isolate the hydrophilic fraction of leachate samples, hydrophilic organic nitrogen was found to be more biodegradable/bioavailable than the hydrophobic fractions. Furthermore, biological and physical-chemical treatment methods were applied to a landfill biogas (LFG) condensate to explore the feasible treatment alternatives for organic contaminant and arsenic removal efficiency. Sequencing batch reactor (SBR) showed effectiveness for the degradation of organic matter, even in an environment containing high levels of arsenic. This indicated a relatively low toxicity of organic arsenic as compared to inorganic arsenic. However, for arsenic removal, oxidation-coagulation, including biological oxidation, conventional oxidation and advanced oxidation followed by ferric salt coagulation, and carbon adsorption were not effective for what is believed to be tri-methyl arsenic. Among these, advanced oxidation-coagulation showed the best treatment efficiency (15.1% removal). Only reverse osmosis (RO) could reduce the arsenic concentration to an acceptable level to meet discharge limits. These results implied high stability and low toxicity of organic arsenic.

Constantly growing world population leads to ever-increasing energy demand and is stretching the available energy supplies. Consequently, new energy sources must be identified and developed. Economic, environmental and social impact must be considered when evaluating alternative energy sources. An ideal source would be locally distributed and renewable with minimal economic and environmental impact on our current lifestyle.Membrane processes have gained importance in a wide spectrum of applications due to their low energy requirements. Process technologies for alternative energy production can be intensified with the application of membranes. This dissertation is focused on the application of membrane science for advancing the efforts to develop sustainable energy alternatives. We developed two membrane processes, one for application in a bio-refinery based on ligno-cellulosic biomass and another for electricity generation from salinity gradient.The first process development attempts to solve a separation issue related to a bio-refinery that operates with a ligno-cellulosic biomass feedstock. Production of bio-ethanol from ligno-cellulosic biomass requires pretreatment of the biomass to hydrolyze hemi-cellulose, separate lignin and reduce cellulose crystallinity. During the pretreatment by dilute acid hydrolysis (or other method of hydrolysis), several grams of acetic acid per liter of hydrolysate are generated. Acetic acid needs to be removed from the hydrolysate since it can dramatically reduce the efficiency of the subsequent fermentation step by inhibiting enzyme activity. The conventional method of hydrolysate detoxification, lime treatment, consumes significant quantities of calcium hydroxide, involves solids handling and does not produce any valuable products.We propose to remove the acetic acid with an alternative process whereby acetic acid is extracted into 1-octanol in a membrane extractor and is reacted with 1-octanol in situ with a catalyst present on the surface of membrane contactor. This esterification reaction yields 1-octyl acetate and water as the reaction products. Acetic acid concentration in the hydrolysate will be reduced from 12.5 g/L to less than 1 g/L. The product ester will be removed periodically from the organic phase. The product has very good solvent properties and can be sold to improve the process economics. In our study, we identify a suitable membrane and combine it with a catalyst (strong acidic ion exchange resin) to achieve extraction and reaction in a single step. Thus, the membrane extractor/reactor removes acetic acid from the hydrolysate and produces a valuable product (ester) in an environmentally friendly process.The second membrane process development was aimed at harnessing the energy of mixing of two salt solutions differing in their salinities. Significant interest exists in using the salinity difference between fresh water and sea water to produce power from mixing the two streams. Membrane processes such as Reverse Electrodialysis (RED) and Pressure Retarded Osmosis (PRO) can be used to produce electricity using salinity gradients. The less-developed alternative of RED was chosen in this work.We demonstrate the optimization of power output using RED. The effects of several different operational parameters such as current density, solution concentrations, channel thickness, flow rates were evaluated to improve the power output. I also examined the relationship between electrons and ion transfer to determine the efficiency of RED. The Nernst equation indicates that a temperature gradient between the salt solutions will increase the driving force for ion exchange in RED and also increase the conductance (or reduce resistance) of the salt solutions. We investigated the improvement in output power density due to superimposition of temperature gradients on concentration gradients.A theoretical and experimental study was carried out to understand the effect of spacer design on the performance of RED. The computational fluid dynamics package COMSOL was used to evaluate flow distribution within the RED flow channels for a standard spacer and designs that improve flow uniformity. The simulations results were then verified by flow visualization studies. The results show that there is significant scope for improvement in flow distribution to improve the overall RED performance and is an important area requiring dedicated development efforts in future work.

This work investigates ways to fabricate composite macro-structures made of carbon nanotubes in combination with polymers and metals to enhance membrane lifespan and performance. Carbon nanotube Buckypapers were used as a template to engineer composite structures. The new materials have been thoroughly characterized for their thermal, structural and performance characteristics. The permeation and adsorption of gas and water vapor, as well as the membranes’ performance in desalination by direct contact membrane distillation, were tested and compared with polymeric benchmarks.

The goal of this research is to develop zeolite membranes that can simultaneously provide high H2 selectivity and high H2 permeance while possessing adequate hydrothermal and chemical resistances for hydrogen separation from fuel gases and WGS reaction at high temperature of 400 to 550°C. This dissertation work consists of three main parts of research including (1) the development of microwave-assisted method for synthesis of MFI zeolite membranes from template free precursors by seeded secondary growth; (2) controlled modification of MFI zeolite channels by chemical deposition and understanding the mechanism of high H2-selectivity against slightly bigger gases with high H2 permeance at elevated temperatures; and (3) the demonstration of high temperature water gas shift reaction (WGS) in the modified MFI zeolite membrane for enhanced CO conversion. Membranes have been synthesized by seeded secondary growth method from a template-free precursor solution containing NaOH, SiO2, H2O, and Al2(SO4)3 under conventional and microwave heating methods. The effects of precursor composition and synthesis conditions on the membrane formation and membrane quality have been investigated. The MFI zeolite membranes obtained by seeded secondary from the template-free precursor tend to develop oblique orientation. Gas permeation tests on small molecules, such as H2 and CO2, and large molecules, such as SF6 have shown that the membranes were free of pinholes and contain minimal amount of non-zeolitic intercrystal spaces. The zeolite membranes obtained from template-free precursors do not need a firing for template removal that avoids the risk of defect formation during the template removal process. The microwave synthesis method was found to dramatically reduce the hydrothermal synthesis duration as compared to the traditional heating method, and hence is more energy-efficient.According to the molecular dynamic diffusion theory, the MFI-type zeolite pore size is incapable of obtaining H2/CO2 selectivity much high than the Knudsen factor (i.e. 4.7) at high temperature. A new method of on-stream catalytic cracking deposition (CCD) has been developed for MFI zeolite membrane modification to reduce the effective pore opening so that a size discrimination effect can be achieved for H2 against other small gases like CO2. The methyldiethoxysilane (MDES) was used as the silane precursor for CCD modification and the MFI zeolite pore size was narrowed from 0.56 nm to ~ 0.33 nm after the modification. The modified membrane obtained a H2/CO2 permselectivity as high as 147 at 450°C and the modified structure also showed good thermal stability in the presence of steam. Theoretical analysis based on the molecular dynamic diffusion model has revealed that the dramatically enhanced H2 selectivity in the modified is due primarily to the reduction of the molecular load of large molecules in the zeolite cavity. A porous α-alumina tube supported MFI-type zeolite membrane with a small membrane area of 1.1 cm2 has been modified by the CCD method. The modified zeolite membrane tube was combined with a Cr-doped ferrite catalyst for WGS membrane reaction in a temperature range of 400-550 °C. The WGS reaction results demonstrate that the zeolite membrane reactor is effective for enhancing CO-conversion (χco) at kinetically favorable high temperatures especially when high space velocity (WHSV) and low steam-to-CO ratios (RH2O/CO) are used. At 550 °C with a high WHSV of 60,000 h-1 and a low RH2O/CO of 1.0, the modified zeolite MR achieved χco of 81.7%, which was much higher then that in the traditional packed-bed reactor (χco =62.5%) and well above the equilibrium limit (χco =65%) as well.

Direct contact membrane distillation (DCMD) was investigated for its performance abilities and capability to concentrate aqueous solutions with high solid contents at low temperatures. The process was envisaged for applications when concentration of thermally sensitive liquid foods to high final concentrations with minimal thermal damage to the products is required.

Macromolecular components, including protein and polysaccharides, are viewed as one type of major foulants in the complex feed membrane filtration systems such as membrane bioreactor (MBR). In this thesis, the mechanisms of macromolecular fouling including protein and polysaccharide in the complex feed solution are explored by using Bovine serum albumin (BSA) and alginate as model solution. During the filtration of BSA and washed yeast with 0.22 ¥ìm PVDF membrane, it was found that the critical flux of mixture solution was controlled by washed yeast concentration while the existence of BSA significantly changed the cake reversibility of much larger particles. The fouling mechanisms of alginate, as a model polysaccharide solution, were investigated both in dead end and crossflow membrane filtration. In the dead end experiments, it was found that the cake model appears to fit the entire range of the ultrafiltration data while the consecutive standard pore blocking model and cake model are more applicable to microfiltration membranes. The alginate was featured with high specific cake resistance and low compressibility despite some variations between different membranes. The specific cake resistance ( c ) is similar to c of BSA and actual extracellular polymer substance (EPS) in MBR systems reported in the literature, and higher than that of many colloidal particles. In a system contained alginate-particles mixture, it was found that the existence of alginate dramatically increased the cake specific resistance and decreased the cake compressibility. The fouling mechanism of alginate was also studied using long term cross flow filtration under subcritical flux. A two-stage TMP profile similar to that typically observed in MBR was obtained, confirming the important role of EPS during membrane fouling in MBR. In addition to adsorption, trace deposition of alginate also contributed to the initial slow TMP increase during the subcritical filtration. TMP increase during the long-term filtration was found not only due to the increase of the amount of deposition, but also the increase of specific cake resistance. A combined standard pore blocking and cake filtration model, using a critical pore size for the transition time determination, was developed and fit the experimental results well.

In this study the fouling mechanisms of various microfiltration and ultrafiltration membranes were studied when subjected to crossflow filtration using various protein solutions. Experimentation was carried out using controlled flux experiments and fouling phenomena was investigated via the monitoring of the transmembrane pressure (TMP) and rejection. Electron microscopy was employed to study fouling on microfiltration membranes when single protein solutions were filtered while a novel method involving Matrix-Assisted Laser Desorption Ionisation Mass Spectrometry (MALDI-MS) was developed to qualitatively and quantitatively analyse mixed proteins fouled on ultrafiltration membranes. An apparent critical flux was identified whereby fouling was shown to occur at fluxes where there was no increase in TMP. TMP increase is one of the common indicators of fouling in controlled flux operation. Microfiltration experiments showed that the imposition of the apparent critical flux is accompanied by rapid increases in hydraulic resistance and the membrane wall concentration. Pore blockage and narrowing occurred at somewhat higher fluxes as indicated by increases in the observed rejection. Fouling was not influenced greatly by the addition of electrolytes for microfiltration membranes but observed transmissions were found to be greater than 100% when ultrafiltration membranes were employed. For all membranes used, the actual value of the apparent critical flux was shown to be independent of the salt concentration but dependent on pH. Sub apparent-critical constant flux microfiltration showed the existence of an aggregation/deposition time lag after which the membrane experiences a rapid increase in resistance due to protein aggregates blocking a majority of pores. This phenomenon was shown to be dependent on pH and ionic strength and was concluded to be the product of a balance between electrostatic, solubility and hydrophobic interactions.

The purpose of this research was to develop the hollow fiber membrane (HFM) bioreactor system for treatment of chlorinated solvents in waste mixtures. This new technology employs a hollow fiber membrane reactor to separate chlorinated solvents from water or air with subsequent cometabolic biodegradation using a mutant methanotrophic microorganism, Methylosinus trichosporium OB3b PP358. Research objectives included demonstrating successful performance of the HFM bioreactor system for the treatment of trichloroethylene (TCE) contaminated water and air, increasing process efficiency for cost competitiveness with conventional technologies, extending HFM bioreactor studies to chlorinated solvent mixtures, and developing a system design strategy. HFM bioreactor demonstration experiments evaluated various process configurations, flow rates, and influent TCE concentrations. In TCE viii contaminated water experiments, mass transfer coefficients as large as 2.7×10-2 cm/min were estimated and the system was able to sustain an average first-order degradation rate constant of 0.57 L mg TSS-1 d-1 for 500 hours. While configuring the system with chlorinated solvents flowing through the HFM lumen and microorganisms flowing through the HFM shell was preferred for aqueous experiments, air treatment experiments required switching the flows because water vapor mass transfer resulted in water clogged fiber lumen. Following the demonstration experiments, shorter HFM hydraulic residence times between 0.16 and 0.57 minutes were investigated. A tradeoff between providing sufficient oxygenation and methanol stripping in the chemostat was observed. A new process decision variable, specific transformation was defined and values as large as 38.5 µg TCE/mg TSS were sustainable for TCE treatment. In HFM bioreactor experiments with a mixture of TCE and chloroform (CF), large TCE first-order degradation rate constants between 0.75 L mg TSS-1 d-1 and 1.08 L mg TSS-1 d-1 indicated that the addition of CF did not affect TCE degradation. CF mass transfer coefficients were approximately 10% less than TCE coefficients and the average CF degradation rate constant was 0.32 that of TCE. Computer models of mass transfer and biodegradation in the system were constructed and validated with experimental data. A modeling analysis was then conducted on the important decision variables and parameters and the results were used to develop a system design strategy.

A variety of methods exist to remove volatile organic compound (VOC) air pollutants from contaminated gas streams. As regulatory and public opinion pressures increase, companies are searching for more effective methods to control these emissions. This document is intended as a guide to help determine if existing systems are adequate and to provide additional information to improve the efficiency of the systems. It explores conventional methods of controlling VOC emissions, as well as innovative technologies including membrane separation, plasma destruction, and ozone catalytic oxidation. The conventional technologies covered include condensation, adsorption, absorption (or scrubbing), thermal incineration, flaring, catalytic incineration, and biofiltration. Each chapter includes a description of the technology, a discussion of the types of systems available, notes on the design of the system, economic estimates, an explanation of potential problems, and a list of considerations for installation and maintenance concerns. The final chapter is dedicated to the preparation and characterization of metal catalysts which were developed to improve the reaction rate of VOCs using ozone as an oxidant.

The mechanism of how pulsatile flow affects flux behaviour in crossflow micro-filtration was investigated. The effects of pulsatile flow were sub-divided into shear effects and backflushing effects. A servo-valve hydraulic piston pump was applied to generate pulsatile flows in the membrane module with particular waveforms. Four types of fluid pulsation with specific flow-rate and pressure waveforms were produced for experimental tests. Two parameters, /dVcf\dt/ maxand Pmin, were examined independently for their effect during pulsatile flow, which was estimated by comparing the cake resistance during steady flow and pulsatile flow at the same mean crossflow velocity, trans-membrane pressure and membrane resistance. Filtration tests for all the pulsatile flows with clean water confirmed that pulsatility only affects cake depositions. Without particles, no flux improvement was obtained. The results for the microfiltration of 0.5g/1 silica suspension showed that for pulsatile flows without backflushing (i.e. no negative transmembrane pressure peak), the fluid pulsation decreased cake resistance when the shear related parameter /dVcf\dt/max exceeded a critical value for each given waveform. When the instantaneous transmembrane pressure reached negative values, i.e. back-flushing occurred, the cake resistance was reduced for all pressure waves tested. Cake resistance was reduced more for more negative P min. With two of the waveforms tested, the cake resistance was almost completely eliminated. In contrast, the shear affected cake resistance reduction differently for each waveform. Comparing cake reduction results for different pulsatile waveforms, it was found that, for the square wave, the cake resistance reduction was higher for both shear and backflushing effect tests, while for the short spike waveform, the cake resistance reduction was lower. The flux waveforms were seen to follow the variations in transmembrane pressure. The flux response time was longer than the time required for the pressure changes, but was not dependent on the direction of the pressure change.

The research work described in this dissertation focuses on the investigation of the extraction of Cd(II) and Cu(II) from hydrochloric acid solutions using Aliquat 336 in Shellsol A B solvent and Aliquat 336/PVC membranes. In the solvent extraction study, factors that affect the extraction rate, such as the extractant concentration in the organic phase, the chloride ion concentration in the aqueous phase and extraction time were investigated. T w o phase titration method was used to investigate the distribution of the metal complexes, stoichiometry of the extracted complexes and the equilibrium constants of extraction reactions. In the membrane extraction study, extraction rates and capacities of the membrane were studied as functions of major variables such as the concentration of Aliquat 336 in the membrane and the thickness of the membrane. Mathematical modeling was used to calculate the extraction kinetic rate constants and the diffusion coefficients of the metal complexes in the membrane. The possibility of using the Aliquat 336/PVC membrane to concentrate Cd(II) from a feed solution into a receiver solution was explored for the first time in this work.