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Hosseini S.S.,Tarbiat Modares University | Najari S.,Tarbiat Modares University | Kundu P.K.,University of Waterloo | Tan N.R.,HOSSTECH Group | Roodashti S.M.,Tarbiat Modares University
RSC Advances | Year: 2015

Development of high performance membranes requires deep insights about the various design, fabrication and operational parameters involved in the process. In the present study, the influence of input parameters such as active fiber length, feed temperature, feed composition and feed pressure is investigated to analyze the efficiency of the mathematical models developed for the separation of O2/N2 mixtures in an asymmetric hollow fiber membrane permeator. In addition, the effect of various non-idealities on the membrane performance are studied, individually. Results reveal that in contrast to pressure, temperature changes have no influential effects on the concentrations of O2 and N2 at permeate and retentate streams. The influence of feed composition on the product purities is more significant compared to active fiber length. Moreover, analysis of non-ideal effects indicates that pressure changes and concentration polarization are the most significant non-idealities among the effects. Results of this investigation can effectively be used for having a comprehensive overview about the impact of influential parameters and non-ideal effects on the membrane performance for O2/N2 separation application. © The Royal Society of Chemistry. Source

Dehkordi J.A.,Tarbiat Modares University | Hosseini S.S.,Tarbiat Modares University | Kundu P.K.,University of Waterloo | Tan N.R.,HOSSTECH Group
Chemical Product and Process Modeling | Year: 2016

Hollow fiber membrane permeators used in the separation industry are proven as preferred modules representing various benefits and advantages to gas separation processes. In the present study, a mathematical model is proposed to predict the separation performance of natural gas using hollow fiber membrane modules. The model is used to perform sensitivity analysis to distinguish which process parameters influence the most and are necessary to be assessed appropriately. In this model, SRK equation was used to justify the nonideal behavior of gas mixtures and Joule-Thomson equation was employed to take into account the changes in the temperature due to permeation. Also, the changes in temperature along shell side was calculated via thermodynamic principles. In the proposed mathematical model, the temperature dependence of membrane permeance is justified by the Arrhenius-type equation. Furthermore, a surface mole fraction parameter is introduced to consider the effect of accumulation of less permeable component adjacent to the membrane surface in the feed side. The model is validated using experimental data. Central Composite Designs are used to gain response surface model. For this, fiber inner diameter, active fiber length, module diameter and number of fibers in the module are taken as the input variables related to the physical geometries. Results show that the number as well as the length of the fibers have the most influence on the membrane performance. The maximum mole fraction of CO2 in the permeate stream is observed for low number of fibers and fibers having smaller active lengths. Also results indicate that at constant active fiber length, increasing the number of fibers decreases the permeate mole fraction of CO2. The findings demonstrate the importance of considering appropriate physical geometries for designing hollow fiber membrane permeators for practical gas separation applications. © 2016 by De Gruyter. Source

Alaei Shahmirzadi M.A.,Tarbiat Modares University | Hosseini S.S.,Tarbiat Modares University | Ruan G.,Institute of Seawater Desalination And Multipurpose Utilization | Tan N.R.,HOSSTECH Group
RSC Advances | Year: 2015

Design and fabrication of nanofiltration (NF) membranes with the desired characteristics and separation performance is of paramount importance. In this study various asymmetric nanofiltration membranes were designed and fabricated using poly(ethersulfone) (PES) via phase inversion technique. The effects of variation in polymer concentration, solvent type, additives in the dope solution and composition of coagulating agent were studied as the selected design parameters. The effects of variation in solvent evaporation time, coagulation bath temperature, casting speed (shear rate) and membrane thickness were also investigated as the selected fabrication parameters. The results obtained reveal that increasing the polymer concentration, promoting a delay in demixing through a change of solvent and composition of coagulating agent as well as decreasing the coagulation bath temperature, increasing the solvent evaporation time and membrane thickness all result in NF membranes with less overall porosity and mean pore size, lower water flux and higher salt rejections. Furthermore, addition of hydrophilic organic acids, (e.g., ascorbic and citric acids) in the dope solution and incrementally increasing the casting shear rate promote overall porosity of the membrane, water flux and salt rejection. Membranes derived from PES/N-methyl-2-pyrrolidone (30/70 wt%) could offer maximum salt rejections of 47.35% and 99.84% for sodium chloride and magnesium sulfate, respectively. The pure water flux in the membranes could be enhanced up to 54.88 l m-2 h-1 by addition of 1 wt% citric acid into the dope solution. In terms of operational parameters, increase in both feed pressure and pH could enhance the membrane flux and salt rejections. The findings in this study provide useful guidelines and methods for the design and fabrication of high performance asymmetric NF membranes with the desired microstructure, productivity and separation performance. © The Royal Society of Chemistry 2015. Source

Hosseini S.S.,Tarbiat Modares University | Omidkhah M.R.,Tarbiat Modares University | Zarringhalam Moghaddam A.,Tarbiat Modares University | Pirouzfar V.,Tarbiat Modares University | And 2 more authors.
Separation and Purification Technology | Year: 2014

The evolution of desirable physico-chemical structure and properties in high performance gas separation membranes involve steps that must carefully be designed, controlled and optimized. This study investigates the role of key parameters in the fabrication and performance analysis of carbon molecular sieve (CMS) membranes prepared through blending of poly (benzimidazole) (PBI) and three polyimides containing different dianhydride moieties in their chemical structure. Results indicate that the chemical structure of the blend components, microstructure of the precursor, blend composition and the pyrolysis conditions play important roles in the transport properties of the resulting membranes. The influence of the type of polyimide used in the blend on the permeability of the carbon membranes followed a trend. Using a higher pyrolysis temperature resulted in membranes with a lower permeability but higher selectivity. In addition, a higher degree of vacuum in the pyrolysis chamber increased the selectivity of the membranes by as much as 40% at the expense of permeability. The highest gas pair selectivity for O2/N2, CO 2/CH4 and CO2/N2 could be obtained from PBI-Kapton carbonized at 10-7 Torr and 800 C. These results also suggest that CMS membranes derived from PBI-Kapton blend precursors are exceptional candidates for the CO2/CH4 separation, offering enhanced selectivity in the range of up to 204.5 depending on the pyrolysis protocol. The results of this study suggest that high performance gas separation membranes can be obtained by adopting a judicious combination of blending technique and optimized pyrolysis conditions. © 2013 Elsevier B.V. All rights reserved. Source

Hosseini S.S.,Tarbiat Modares University | Bringas E.,University of Cantabria | Tan N.R.,HOSSTECH Group | Ortiz I.,University of Cantabria | And 2 more authors.
Journal of Water Process Engineering | Year: 2016

Development of advanced technologies for metal plating wastewater treatment constitutes one of the major fields of research, primarily driven by the progressive environmental regulations issued to address the concerns. The emergence of various membrane-based processes and the satisfactory trial and field tests have created new avenues for minimization of the negative impacts caused by the uncontrolled discharge of metal plating waste streams. On the other hand, the progress in the polymer science and engineering provides opportunities for development of membrane materials with advanced functionalities and superior characteristics that can effectively be employed for design and fabrication of high performance membranes. The present review provides an overview on the specifications of metal plating wastewater streams and the significance of the treatment by presenting possible strategies that can be employed for heavy metal removal. Special attention is paid to nickel, chromium and zinc due to their high impacts and detrimental effects. In addition, a comprehensive review is provided on the recent advances in development of high performance polymeric materials for diverse membrane-based processes including reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), complexation-ultrafiltration (CUF), microfiltration (MF), polymer inclusion membranes (PIMs), electro-membranes (EMs), hybrid processes, liquid membranes, emulsion liquid membranes (ELMs) and membrane-based solvent extraction by highlighting the role of molecular design and architecture and other featured characteristics in the process performance and efficiency. © 2015 Elsevier Ltd. Source

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