Chemical and Biomolecular Engineering - Research Publications
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ItemEffects of industrial gas impurities on the performance of mixed matrix membranes(ELSEVIER SCIENCE BV, 2018-03-01)
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ItemCan the addition of carbon nanoparticles to a polyimide membrane reduce plasticization?(ELSEVIER SCIENCE BV, 2017-08-07)
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ItemEnhancing gas permeability in mixed matrix membranes through tuning the nanoparticle properties(ELSEVIER SCIENCE BV, 2015-05-15)
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ItemThe potential for use of cellulose triacetate membranes in post combustion capture(ELSEVIER SCI LTD, 2016-12)
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ItemThe impact of water vapor on CO2 separation performance of mixed matrix membranes(Elsevier, 2015-10-05)A series of mixed matrix membranes (MMMs) using nanoparticles involving carbons, porous organic polymers and metal organic frameworks (MOFs) were prepared to investigate the impact of water vapor on CO2 separation performance. The water uptake of MMMs using hydrophilic MOFs increased relative to more hydrophobic particles such as the porous organic polymers and carbons and this trend was reflected in the water vapor permeability, which varied by a factor of three between the hydrophobic and hydrophilic MMMs. These changes in water vapor permeability were strongly correlated with the water solubility, indicating that it is this solubility that is the controlling parameter. The calculated water diffusivity was consistent with previously published results. The gas permeability of MMMs in the presence of water vapor was also strongly affected by the nanoparticle hydrophobicity, with membranes composed of hydrophobic fillers out-performing hydrophilic fillers of comparable porosity. However in general, the differences in performance between MMMs and the pure polymer narrowed in the presence of water vapor.
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ItemWater vapor permeation through cellulose acetate membranes and its impact upon membrane separation performance for natural gas purification(Elsevier, 2015-08-01)Abstract Cellulose acetate is the predominant material used in membrane separation of acid gases from natural gas and biogas. However, the sensitivity of these membranes to water vapor is not well understood. In this work, flat-sheet membranes of two different degrees of acetylation, were exposed to both dry and humidified CH4 and CO2/CH4 mixtures. Positron Annihilation Lifetime Spectroscopy experiments showed that the number of free volume elements decreased as water concentration increased, indicating pore filling effects. The size of the free volume elements declined initially, followed by an increasing trend at vapor partial pressures greater than 2.5 kPa, indicating polymer swelling. Gas permeabilities of CH4 and CO2 followed a similar trend, with an initial decline due to hindered diffusion and competitive sorption, followed by an increase as the humidity exceeded 2.5 kPa. Water vapor permeabilities increased from 11,000 to 27,000 Barrer as the water activity increased but a change in the rate of increase was also noted at 2.5 kPa. At humidities in excess of 0.8, the extent of membrane swelling was such that equilibrium was not established even after 8 h of operation. Importantly, plasticization had significantly less impact on the polymer with a higher degree of acetylation.
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ItemWater permeability and competitive permeation with CO2 and CH4 in perfluorinated polymeric membranes(Elsevier, 2015)Abstract The permeability of water through polymeric membranes is of particular interest in gas separation, because of the high water vapor content found in many industrial applications. Polymeric membranes that are resistant to competitive sorption and plasticization by water are especially attractive, since they can reduce the need for gas pretreatment in many membrane applications. The perfluorinated polymers Teflon AF1600 and Hyflon AD60 are studied here for this purpose because of their strong hydrophobicity and unusual solvent properties. It was observed that water permeability through both perfluorinated polymers was of the same magnitude as CO2. Indeed, under the conditions studied, Teflon AF1600 was selective for CO2 over water. Such reverse selectivity for the CO2 – H2O gas pair has not been reported before for glassy polymeric membranes and reflects the very low solubility of water in the polymer. The water permeability through Hyflon AD60 was greater than that for CO2 with a minimum at 55 oC. The change in both CO2 and CH4 permeability through Teflon AF1600 and Hyflon AD60 was investigated as a function of water activity in the feed gas to investigate the effects of competitive permeation. It was observed that CO2 and CH4 permeability in both membranes reduced with water activity. For both Teflon AF1600 and Hyflon AD60, the decrease in permeability of both gases with water activity was interpreted as water clusters blocking the diffusion of both CO2 and CH4 through the membrane.