Browsing by Subject "membrane"
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Item Design and Development of a Vacuum Dehumidification Test Facility(2014-08-13) Schaff, Francesco NimaA test facility was designed and constructed with the capability of isolating critical variables for controlling the novel membrane dehumidification-enabled cooling system?s operation parameters as well as for acquiring preliminary membrane and cooling system performance measurements. The completed test facility consisted of two systems: 1) the feed-air system, which simulated the inlet-air conditions and performed the feed-air dehumidification and sensible cooling and 2) the vacuum system, which enabled the feed-air dehumidification by evacuating the membrane permeate side. The feed-air system as constructed was able to supply membrane-inlet flow rates up to 10 scfm over a range of temperature and relative humidity conditions, including 90?F and 90%RH, which was specified by the project sponsor. In addition, the feed-air system components included a membrane module installation site for dehumidification as well as a sensible cooling system to cool the membrane-outlet air to the 55?F and 50%RH conditions again specified by the sponsor. Measurement stations were placed at the membrane-inlet, membrane-outlet, and the sensible cooler outlet to measure the temperature and relative humidity at these critical locations. The vacuum system as built used a Pfeiffer DUO 10 Vacuum Pump with a 7 cfm pumping capacity, which was preceded by a 60 plate heat exchanger with an effective area of 2.05m^(2) and an Oerlikon-Leybold WA 250 roots blower. The air leakage in the vacuum system was calculated to be less than 1% of the theoretical air permeation through the membrane module. Finally, the apparatus was constructed with the capability of measuring the power consumption of the equipment used for the dehumidification and sensible cooling process. The functionality of the test facility was demonstrated through preliminary testing of the membrane module and the operation of the complete cooling system. The results suggested that the membrane material exhibited an increase in water vapor permeance from temperatures of 70 to 100?F, with calculated permeance values ranging from to 3.93 ? 10^(-6) to 5.88 ? 10^(-6) kmol/kPa-m^(2)-s. In addition, the results indicated that the novel membrane dehumidification-enabled cooling system was capable of achieving the specified operating conditions at a feed-air flow rate of 0.16 scfm by using a membrane module area of 0.024m^(2).Item Development of Metal-Organic Framework Thin Films and Membranes for Low-Energy Gas Separation(2011-08-08) McCarthy, MichaelMetal-organic frameworks (MOFs) are hybrid organic-inorganic micro- or mesoporous materials that exhibit regular crystalline lattices with rigid pore structures. Chemical functionalization of the organic linkers in the structures of MOFs affords facile control over pore size and physical properties, making MOFs attractive materials for application in gas-separating membranes. A wealth of reports exist discussing the synthesis of MOF structures, however relatively few reports exist discussing MOF membranes. This disparity owes to challenges associated with fabricating films of hybrid materials, including poor substrate-film interactions, moisture sensitivity, and thermal instability. Since even nanometer scale cracks and defects can affect the performance of a membrane for gas separation, these challenges are particularly acute for MOF membranes. The focus of this work is the development of novel methods for MOF film and membrane fabrication with a view to overcoming these challenges. The MOF film production methods discussed herein include in situ synthesis using ligand-modified or metal-modified supports and rapid thermal deposition (RTD).Item Energy Recovery Ventilator Membrane Efficiency Testing(2013-05-07) Rees, Jennifer AnneA test setup was designed and built to test energy recovery ventilator membranes. The purpose of this test setup was to measure the heat transfer and water vapor transfer rates through energy recover ventilator membranes and find their effectiveness, with air conditions that resemble residential use. Two test chambers were constructed with different channel heights above the membrane; one was 1mm and the other 2mm. The 2mm setup gave measureable results, but small air leaks in the system of 7.0% and 6.2% left room for error. The 1mm setup also had air leaks but they were smaller than the 2mm setup, with leak rates of 1.0% and 5.1%. The permeance of the membrane was found to be 2.58x10^-5 g/(m2*s*Pa) for the 2mm test chamber and 9.90x10^-54 g/(m2*s*Pa) for the 1mm test chamber.Item Nanocomposite Membranes for Complex Separations(2010-10-12) Yeu, Seung UkOver the past few decades there has been great interest in exploring alternatives to conventional separation methods due to their high cost and energy requirements. Membranes offer a potentially attractive alternative as they potentially address both of these points. The overarching theme of this dissertation is to design nanocomposite membranes for processes where existing separation schemes are inadequate. This dissertation focuses on three challenges: 1) designing organic-inorganic hybrid membranes for reverse-selective removal of alkanes from light gases, 2) defect-free inorganic nanocomposite membranes that have uniform pores, and 3) nanocomposite membranes for minimizing protein fouling in microfiltration applications. Reverse-selective gas separations that preferentially permeate larger/heavier molecular species based on their greater solubility have attracted considerable recent attention due to both economic and environmental concerns. In this study, dendrimer-ceramic hybrid membranes showed exceptionally high propane/nitrogen selectivities. This result was ascribed to the presence of stable residual solvent that affects the solubility of hydrocarbon species. Mesoporous silica-ceramic nanocomposite membranes have been fabricated to provide defectless mesoporous membranes. As mesoporous silica is iteratively synthesized in the ceramic macropores, the coating method and the surfactant removal step significantly affected permeance and selectivity. It was also shown that support layers can cause a lower selectivity than Knudsen limit. Membrane fouling which results from deposition and nonspecific adsorption of proteins on the membrane surface is irreversible in nature, and results in a significant decrease in the membrane performance. To address this problem, two approaches were explored: 1) control of the surface chemistry tethering alumina membranes with organic components and 2) development of a novel photocatalytic membrane that exhibits hydrophilicity and can be easily regenerated. Both approaches can offer a viable route to the synthesis of attractive membranes, in that 1) the density of protein-resistant organic groups such as PEG is controllable by changing scaffolds or synthesis conditions and 2) the photocatalytic nanocomposite membranes can open the way for a new regeneration method that is environmentally benign.Item Perchlorate Degradation Using Partially Oxidized Titanium Ions and Ion Exchange Membrane Hybrid System(2011-08-08) Park, Sung HyukPerchlorate has entered human and environmental food chains and has received a great deal of attention because of its toxicity to humans. In this study, chemical degradation of perchlorate was investigated using partially oxidized titanium ions (Ti2+ and Ti3+) in solutions and as part of an ion exchange membrane reactor system. Aqueous titanium ions (Ti2+ and Ti3+) were applied to remove perchlorate ions and its destructive mechanism, reaction kinetics, and the effect of environmental factors were investigated. Titanium ions were able to degrade perchlorate ions very rapidly with half life less than one hour under conditions of high acid concentrations. A new reactor system with an ion exchange membrane was adapted to apply better the reactions of perchlorate destruction to water treatment practice. A novel treatment method was developed by integrating partially oxidized titanium ions with an ion exchange membrane, and it is named the Titanium and Membrane Hybrid System (TMH System). The results shown in this research demonstrate the feasibility of TMH System for perchlorate reduction. The perchlorate ions were rapidly adsorbed onto the ion exchange membrane and diffused through it, but they were reduced by titanium ions in the degradation zone relatively slowly. To enhance the overall rate of reaction, high concentrations of acid and Ti(III) are needed, but transport of hydrogen ions through the anion permeable membrane was observed and would be greater at higher acid concentrations. The proposed mathematical model predicts the performance and behavior of the TMH system for different physical and chemical conditions. It successfully described adsorption, diffusion and reduction of perchlorate in the system. This model could be used as an important tool for process design and optimization.Item Sorting of inner nuclear membrane-directed proteins at the endoplasmic reticulum membrane(Texas A&M University, 2006-04-12) Saksena, SurajThe current "diffusion-retention" model for protein trafficking to the inner nuclear membrane (INM) proposes that INM proteins diffuse laterally from the membrane of the endoplasmic reticulum into the INM and are then retained in the INM by binding to nuclear proteins or DNA. Because some data indicate that the sorting of baculovirus envelope proteins to the INM is protein-mediated, we have examined the early stages of INM protein integration and sorting using photocrosslinking. Both viral and host INM-directed proteins were integrated cotranslationally through the endoplasmic reticulum translocon, and their nonrandom photocrosslinking to two translocon proteins, Sec61? and translocating chain-associated membrane protein (TRAM), revealed that the first transmembrane sequence (TMS) of each viral and host INM-directed protein occupied a very similar location within the translocon. Because few TMSs of non-INM-directed membrane proteins photocrosslink to TRAM, it seems that the INM-directed TMSs occupy different sites within the translocon than do non-INM-directed TMSs. The distinct proximities of translocon components to INM-directed TMSs strongly suggest that such TMSs are recognized and initially sorted within the translocon. Previous work with the envelope protein ODV-E66 (E66) showed that E66 trafficking to the INM is mediated via an INM sorting signal (Sorting Motif or SM). In this study, using a site-specific crosslinking approach we demonstrate that following ER membrane integration, the SM is adjacent to two viral proteins: FP25K & BV/ODV-E26 (E26). Deletion of FP25K from the viral genome results in the accumulation of E66 at the ONM, suggesting that FP25K may facilitate protein movement at the nuclear pore. While the role of the E66-E26 interaction remains to be determined, these data suggest that E66 trafficking to the INM is a protein-facilitated process. Crosslinking experiments using E66 integration intermediates revealed that during co-translational integration at the ER, the SM is adjacent to two cellular proteins of ~10kDa and ~25kDa, referred to as SMAP 10 (SM associated protein of 10kDa) & SMAP25 respectively. Thus, contrary to the widely accepted "diffusion-retention" model for protein trafficking to the INM, our data indicate that protein sorting to the INM is a multistep process initiated upon membrane integration in which the INM sorting signal sequentially associates with various sorting factors.Item Synthesis and Characterization of Iso-Reticular Metal-Organic Frameworks and Their Applications for Gas Separations(2011-10-21) Yoo, YeonshickNanoporous metal-organic frameworks (MOFs) have attracted tremendous interest due to their potential applications in gas-storage, gas separation, gas sensing, and catalysis. MOFs consist of metal-oxygen polyhedera interconnected with a variety of organic linker molecules, resulting in tailored nanoporous materials. With a judicious choice of organic linker groups, it is possible to fine-tune size, shape, and chemical functionality of the cavities and the internal surfaces. This unique structural feature offers unprecedented opportunities in small-molecule separations as well as chiral separations and catalysis. Prototypical iso-reticular metal-organic frameworks (IRMOFs) have been extensively studied among MOFs due to the simplicity of their synthesis and the variety of their potential applications. IRMOFs are a specific series of metal-organic frameworks developed by Yaghi and his coworkers. All IRMOFs are composed of oxygen-centered Zn4O tetrahedra interconnected with dicarboxylate linkers, forming a cubic type three dimensional (3D) porous network with high surface area. Despite a great deal of research in the synthesis and characterization of MOFs, there have been relatively few reports on the development of their applications, such as the fabrication of MOF thin films and membranes for gas separations. This is mainly due to the challenges associated with relatively difficult heterogeneous nucleation (seeding) and growth of MOFs on supports, and crack formation compared to their counterparts. Thin films and membranes of MOFs have great potentials for applications in membranebased gas separations, reactors, chemical sensors, and nonlinear optical devices. In this dissertation, the fabrication of IRMOF-1 membrane using a novel seeding method and its gas diffusion properties has been demonstrated. Introduction of the new seeding method for MOFs using microwaves resulted in well inter-grown IRMOF membranes showing Knudsen type transport of small gases through its pore. The heteroepitaxial growth of one IRMOF on another produced multi-layered IRMOF membranes. In addition, postsynthetic modification (PSM) of IRMOFs created functionalized membranes with enhanced stability against water as well as reduced crack formation during membrane fabrication. Lastly, hierarchical IRMOFs with improved CO2 adsorption properties were synthesized via PSM with cyanuric chloride.