Browsing by Subject "Membranes (Technology)"
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Item A study of controlling resistances during initial solvent evaporation period of asymmetric membrane formation.(Texas Tech University, 1975-05) Majid, S. M ANot availableItem A study of controlling resistances during initial solvent evaporation period of asymmetric membrane formation.(Texas Tech University, 1975-05) Majid, S. M ANot availableItem A thermodynamic model for membrane transport.(Texas Tech University, 1975-12) Narayan, Raghu SubramaniNot availableItem Control of silica scaling phenomena in reverse osmosis systems(2005) Pacheco Rodriguez, Rocio Idalia; Lawler, Desmond F.Item Crosslinked hollow fiber membranes for natural gas purification and their manufacture from novel polymers(2004) Wallace, David William; Koros, William J.; Paul, Donald R.Item The effect of uni-axial stretching on microporous phase separation membrane structure and performance(2006) Morehouse, Jason Andrew; Lloyd, Douglas R., 1948-Item Experimental study of the membrane behavior of shale during interaction with water-based and oil-based muds(2005) AL-Bazali, Talal Mohammad; Chenevert, Martin E.; Sharma, Mukul M.Three integrated experimental studies were carried out in order to study the membrane behavior of shale when interacting with water-based and oil-based muds. Results confirmed the belief that shales act as leaky semi-permeable membranes. Measured membrane efficiencies were low and ranged from 0.18 % to 4.23 % when shales interacted with water-based muds. Independently, measured ion selectivities (modified diffusion potentials) indicated that shales behaved as ion-selective membranes that restrict the flow of anions. In addition, results showed that both the membrane efficiency and the ion selectivity of shales increase with decreasing shale permeability and increasing cation exchange capacity. Our results also showed a good correlation between the membrane efficiency and the ion selectivity of shales. A gravimetric test was developed that allows us to measure the flux of water and ions into or out of a shale. Results from this test show that the flux of ions depends on the ionic radii and the shale permeability and CEC. These results are consistent with the ion exclusion and membrane potential measured for the shale. The membrane efficiency of oil-based muds was high compared to that obtained for water-based muds. However, the measured membrane efficiency was not 100 %. Results obtained from immersion tests also showed that the oil-based mud was not a perfect ionic barrier since it allowed ions to exchange. A capillary threshold pressure was measured which must be overcome before oil-based mud flows through a shale. Results showed that this capillary entry pressure increases as the shale permeability decreases and the interfacial tension between non-wetting fluid and shale pore fluid increases.Item Integral-skin formation in hollow fiber membranes for gas separations(2001-12) Carruthers, Seth Blue; Koros, William J., 1947-; Willson, C.G., 1939-The morphologies of polymeric integrally-skinned asymmetric gas separation membranes are typically visualized as a thin selective skin region supported by a low resistance porous structure. Improvements in scanning electron microscopy (SEM) now allow for combinatorial analysis of this visualization with gas permeation measurements for previously reported ultra-thin defect-free hollow fiber membranes. The fibers were formed via a dry-jet, wet quench process with a spinning solution comprised of Matrimid polyimide and components of varying volatility. Depending on the formation conditions, the fibers displayed either defect-free skin layers or lower selectivity nodular skin morphologies. Under ideal conditions, defect-free skin thicknesses of 130 nm were characterized by O2, N2 and He permeation in conjunction with SEM studies. A fiber forming technique has allowed for the quick characterization of the skin layer via SEM analysis. The fiber forming technique, high-resolution SEM analysis and gas permeation measurements have allowed for a more complete understanding of defect-free skin formation. Typical solvent exchange techniques did not have a significant influence on the formation of the defect-free skin layer, although a critical point drying method was able to produce membranes with initial gas permeances twice those of conventionally dehydrated hollow fibers. Skin formation was found to primarily be influenced by the evaporation of volatile components from the nascent skin layer in the air gap. Phase separation of the polymer solution in the nascent skin layer was found to be detrimental to skin formation. The one-phase nascent skin layer is suggested to be kinetically hindered from phase separating due to the relative immobility of the polymer chains before immersion into the quench bath. The polymer chain mobility for different potential membrane forming dopes are compared using polymer physics models. Qualitative evidence suggests that lower molecular weight Matrimid samples may be formed into defect-free membranes if the initial dope is 40% wt. polymer, as suggested by the scaling of the previous defect-free membrane system by the Rouse model.Item Mass transfer in liquid membranes.(Texas Tech University, 1974-08) Steele, Raymond DouglasNot availableItem Mass transfer through planar liquid-surfactant membranes.(Texas Tech University, 1974-12) McHaney, Stephen CraigNot availableItem Microporous mixed matrix (ZeoTIPS) membranes(2008-05) Funk, Caleb Vincent, 1982-; Lloyd, Douglas R., 1948-Recent work in the areas of zeolite membranes and mixed matrix membranes have inspired the development of isotropic microporous mixed matrix (ZeoTIPS) membranes, consisting of high-selectivity zeolite particles suspended in a cellular, microporous polymer matrix formed by thermally induced phase separation (TIPS). The particles form nanoporous connections between the cellular voids in the matrix, and can carry out separations independent of the choice of polymer matrix. Existing water purification and gas separation membranes have a variety of drawbacks, including durability, chemical instabilities, cost, flux, and formation difficulty. ZeoTIPS membranes address each of these drawbacks while yielding high selectivity. Included in this work are theoretical predictions of ZeoTIPS membrane performance along with models and experiments designed to gain fundamental knowledge that can be used to develop these membranes. This dissertation discusses how zeolite particles influence the processes of droplet coarsening and pore formation in thermally induced phase separation by disrupting flow fields as well as changing local compositions and viscosities. Additionally, a mathematical model is presented, leading to understanding of the ZeoTIPS formation process. Polymers used in these membranes must have acceptable interactions with the zeolite particles and desired mechanical properties, but must also be able to undergo thermally induced phase separation with a non-hazardous diluent under reasonable processing conditions. Furthermore, processing conditions such as cooling rate are of vast importance in forming ZeoTIPS membranes, but the required conditions can be difficult to obtain. Thus, development of these membranes has required extensive experimental research to determine feasible polymer--diluent systems for forming the microporous matrix and to develop methods of formation.Item Planar liquid-membrane mass transfer.(Texas Tech University, 1975-12) Cheaney, Richard StevenNot availableItem Polymer phase inversion membranes: effect of binary interaction parameters on membrane morphology(Texas Tech University, 1993-05) Burra, Vidya MahankaliNot availableItem Post coarsening effects on membrane microstructure(2008-05) Hanks, Patrick Loring, 1983-; Lloyd, Douglas R., 1948-The goal of this research was to determine relationships between post-coarsening processing conditions and the microporous morphology of membranes. Specifically, the processes of matrix solidification in liquid -- liquid thermally induced phase separation (L−L TIPS), the drying of the microporous structure, and the uni-axial elongation of a simple microporous structure were examined. Additionally, the effect uni-axial elongation has on pore shape was included in a sieve filtration model to look at the impact on performance. A deterministic approach was taken to predict membrane morphologies resulting from the matrix solidification step that occurs in L–L TIPS. Many studies have examined the growth rate of droplets in the coarsening stage of membrane formation, but few have attempted to extend this information into the subsequent processing steps of matrix solidification, diluent extraction/exchange, and drying. The modeling of matrix solidification utilized Monte-Carlo routines to provide quantitative information on cell size and cell size distribution for a representative polymer -- diluent system. The predicted structures were in agreement with experimentally formed membranes. The information gained from matrix solidification modeling was used to make finite element (FE) simulations in ABAQUS CAE to model the drying of the microporous morphology, with capillary forces being the dominant force driving shrinkage and collapse of the structure. These FE simulations predicted no permanent deformation arising from only capillary forces, which was confirmed through experimental evidence showing no correlation to surface tension. For polar polymers an additional heuristic was proposed: use extractants that are more alkane-like, regardless of surface tension, to reduce the collapse of the structure. FE simulations were used to model the uni-axial elongation of track-etch membranes in an effort to change performance characteristics. The FE simulations accurately predicted pore shape changes comparable to experimental values. The pore shape change information was used to modify standard sieve filtration models. The modified sieve filtration models show that a relatively modest strain of 35% can double the initial flux of track-etch membranes.Item Rigorous numerical simulation of gas separation by hollow-fiber membranes(Texas Tech University, 1996-12) Clancy, Donald J.The work develops numerically-stable computer models to simulate the performance of cocurrent, and countercurrent membranes. Additionally, a previously unreported gas-flow pattern, a variance of cross flow, is discussed and simulated. These models assume solution-diffusion permeation, and account for gas non-ideality. A stable method is presented for calculating the permeate pressure drop through the hollow bore of the membrane fiber. This analysis also develops an energy balance and calculation procedures for simulating the temperature change which occurs in a hollow-fiber membrane. The cocurrent and counter-current numerical models are then validated by comparing calculated results against operating data obtained from air- and hydrogen-separation applications. The cross-flow numerical model is then correlated against data obtained from a full-scale, carbon-dioxide purification facility. It was noticed that this facility's cellulose acetate membranes exhibited a marked increase in gas permeability as the CO2 partial pressure increased. This led to an investigation and correlation of the effects of C02-induced plasticization of cellulose acetate on the increase in mixed-gas permeability. It was found that the permeability of hydrocarbons increases much more than that of CO2 as the CO2 partial pressure increases. This leads to a decrease in the amount of hydrocarbon that can be recovered from a membrane unit. This work concludes that enhanced oil recovery facilities utilizing cellulose acetate membranes operating at CO2 partial pressures in excess of approximately 150 psia could substantially benefit by avoiding CO2 plasticization effects either by operating at lower CO2 partial pressures, or lowering the degree of acetylation in the cellulose acetate membrane polymer.Item The production of USPXX water for injection(Texas Tech University, 1985-05) Duncan, James ByronNot availableItem Transient Behavior of Mass Transfer Through Liquid Membranes(Texas Tech University, 1977-08) Shen, Sidney YihNot Available.