Separation Performance

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Zhongyi Jiang - One of the best experts on this subject based on the ideXlab platform.

  • enhancing the co2 Separation Performance of composite membranes by the incorporation of amino acid functionalized graphene oxide
    Journal of Materials Chemistry, 2015
    Co-Authors: Qingping Xin, Zhongyi Jiang, Shaofei Wang, Yuan Zhang, Jing Yang, Xingzhong Cao
    Abstract:

    Composite membranes are fabricated by incorporating amino acid-functionalized graphene oxide (GO-DA-Cys) nanosheets into a sulfonated poly(ether ether ketone) (SPEEK) polymer matrix. Graphene oxide (GO) nanosheets are functionalized with amino acids through a facile two-step method using dopamine (DA) and cysteine (Cys) in succession. The CO2 Separation Performance of the as-prepared membranes is evaluated for CO2/CH4 and CO2/N2 systems. GO nanosheets increase more tortuous paths for larger molecules, enhancing the diffusivity selectivity. Amino acids with carboxylic acid and primary amine groups simultaneously enhance the solubility selectivity and reactivity selectivity. Accordingly, CO2 molecules can transport quickly due to the enhanced selectivity. The optimum Separation Performance is achieved at the GO-DA-Cys content of 8 wt% with selectivities of 82 and 115 for CO2/CH4 and CO2/N2, respectively, and a CO2 permeability of 1247 Barrer, significantly surpassing the Robeson upper bound reported in 2008. Besides, the mechanical and thermal stabilities of the composite membranes are also improved compared with the pristine SPEEK membrane.

  • enhanced interfacial interaction and co2 Separation Performance of mixed matrix membrane by incorporating polyethylenimine decorated metal organic frameworks
    ACS Applied Materials & Interfaces, 2015
    Co-Authors: Jingyi Ouyang, Shaofei Wang, Zhao Li, Zhen Li, Hong Wu, Zhongyi Jiang
    Abstract:

    Polyethylenimine (PEI) was immobilized by MIL-101(Cr) (∼550 nm) via a facile vacuum-assisted method, and the obtained PEI@MIL-101(Cr) was then incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate mixed matrix membranes (MMMs). High loading and uniform dispersion of PEI in MIL-101(Cr) were achieved as demonstrated by ICP, FT-IR, XPS, and EDS-mapping. The PEI both in the pore channels and on the surface of MIL-101(Cr) improved the filler–polymer interface compatibility due to the electrostatic interaction and hydrogen bond between sulfonic acid group and PEI, and simultaneously rendered abundant amine carriers to facilitate the transport of CO2 through reversible reaction. MMMs were evaluated in terms of gas Separation Performance, thermal stability, and mechanical property. The as-prepared SPEEK/PEI@MIL-101(Cr) MMMs showed increased gas permeability and selectivity, and the highest ideal selectivities for CO2/CH4 and CO2/N2 were 71.8 and 80.0 (at a CO2 permeability of 2490 Barrer), re...

  • Separation Performance of thin film composite nanofiltration membrane through interfacial polymerization using different amine monomers
    Desalination, 2014
    Co-Authors: Yafei Li, Yanlei Su, Yanan Dong, Runnan Zhang, Xueting Zhao, Zhongyi Jiang, Jiaojiao Zhao
    Abstract:

    Abstract Four kinds of thin-film composite (TFC) membranes were prepared via interfacial polymerization using diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and piperazidine (PIP) as water-soluble monomer, and trimesoyl chloride (TMC) as organic-soluble monomer. The surface chemical features of the resultant membranes were confirmed by contact angle measurement and Fourier transform infrared spectroscopy (FTIR). The membrane morphology and surface charges were investigated through Scanning electronic microscopy (SEM) and Zeta potential, respectively. Salt rejection was used to evaluate the Separation Performance of the four kinds of TFC membranes. The results showed that all the four kinds of TFC membranes exhibited typical negatively charged nanofiltration membrane characteristics. The salt rejections followed the sequence: Na2SO4 > MgSO4 > MgCl2 and the rejection of Na2SO4 was all over 80%. It was also found that the solubility of water-soluble monomer in organic solvent played an important role in manipulating the membrane structure, charge properties and thus the Separation Performance.

  • tuning the molecular structure Separation Performance and interfacial properties of poly vinyl alcohol polysulfone interfacial composite membranes
    Journal of Membrane Science, 2011
    Co-Authors: Fubing Peng, Zhongyi Jiang, Eric M V Hoek
    Abstract:

    Abstract Interfacial composite membranes were prepared by dip-coating poly(vinyl alcohol) hydrogels on polysulfone ultrafiltration support membranes. Ultra-thin poly(vinyl alcohol) films were cast using multi-step coating procedure with dilute poly(vinyl alcohol) aqueous solutions and stabilized by a novel in situ cross-linking technique using five different cross-linking agents. A previously developed film casting technique allowed a constant film thickness of 200–300 nm to be maintained while varying cross-linking degree and cross-linking agent. The effects of crosslinking on the molecular structure, Separation Performance, and interfacial properties of poly(vinyl alcohol)–polysulfone composite membranes were probed experimentally and with molecular dynamic simulations. Higher degrees of cross-linking correlated strongly with lower PVA film crystallinity and decreased hydrophilicity. Experimentally determined solvent and solute permeability data correlated almost perfectly with molecular dynamics simulated fractional free volumes of the cross-linked poly(vinyl alcohol) membranes, demonstrating the importance of polymer free volume ( i.e. , steric exclusion and hindered diffusion) in solvent and solute transport through nanofiltration membranes and suggesting that predictive, in silico design of cross-linked PVA coating films may be practical.

  • effects of coagulation bath temperature on the Separation Performance and antifouling property of poly ether sulfone ultrafiltration membranes
    Industrial & Engineering Chemistry Research, 2010
    Co-Authors: Jinming Peng, Yanlei Su, Wenjuan Chen, Zhongyi Jiang
    Abstract:

    Poly(ether sulfone) (PES) ultrafiltration membranes are fabricated via nonsolvent-induced phase Separation by blending with hydrophilic homopolymer additive poly(ethylene glycol) (PEG) or amphiphilic block copolymer Pluronic F127. The effects of coagulation bath temperature (CBT) on membrane structure, Separation Performance, and antifouling property are investigated in detail. All the membranes display an asymmetric morphology. PES/PEG membranes possess only fingerlike pores of support layer, while there is a spongelike sublayer between skin layer and the fingerlike pores for PES/Pluronic F127 membranes. The thickness of the spongelike sublayer for PES/Pluronic F127 membranes is remarkablely decreased with the increase of CBT. For all the membranes, pure water flux increases substantially with the increase of CBT. The rejection of PES/PEG membrane for bovine serum albumin (BSA) is above 95%. However, the rejection of PES/Pluronic F127 membrane for BSA molecules is decreased sharply form 95.3% to 10.2% wi...

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  • improving co2 Separation Performance of thin film composite hollow fiber with pebax 1657 ionic liquid gel membranes
    Journal of Membrane Science, 2017
    Co-Authors: Hongyu Li, Jaleh Mansouri, Vicki Chen
    Abstract:

    Abstract Blending CO2-selective ionic liquid with block copolymers have been shown to improve the gas Separation Performance. In this work, defect-free Pebax®1657/[emim][BF4] gel membranes were fabricated in the form of thin film composite hollow-fiber membranes to meet the mechanical stability and high packing density requirement for industrial application. Environmentally benign solvent comprising ethanol/water mixture (70/30 w/w) was selected to allow up to 80 wt% IL loading with 300% improvement in CO2 permeability and CO2/N2 and CO2/CH4 selectivities of 36 and 15, respectively. Characterizations of membrane morphological change responding to the IL loading indicated that the preferential interaction between IL and PEO segments was by hydrogen bonding that resulted in decrease in polymer crystallinity, but this interaction inhibited potential interaction with CO2, which lowered the gas permeability below the estimated value. Examinations on the effects of various operating conditions on the TFC gel membranes showed excellent mechanical durability and chemical stability of the membranes and good CO2 Separation Performance with mixed-gas feed containing traces of water vapor and NOx, suggesting the potential application for CO2 capture with real gas feed. The stability of the high IL-loaded gel membranes with up to 8 bar feed pressure also opens up possibility for other industrial gas applications.

  • factors affect defect free matrimid hollow fiber gas Separation Performance in natural gas purification
    Journal of Membrane Science, 2010
    Co-Authors: Guangxi Dong, Vicki Chen
    Abstract:

    Abstract Asymmetric hollow fibers have increasingly become attractive for high volume gas Separation applications including natural gas purification. The formation of asymmetric structure with ultrathin defect-free selective layer and mechanically robust porous supporting layer without additional coatings is one of the major challenges. In this study, a commercially available polyimide material Matrimid ® was used as the benchmark polymer material in fabrication of hollow fibers for natural gas purification. Major fabrication process variables including polymer solution formulation, bore fluid composition, dope and bore flow rates, and air-gap length were systematically investigated and optimized for fabrication of hollow fibers to achieve high CO 2 /CH 4 Separation Performance. SEM images of cross-section indicated asymmetric structure of hollow fiber with a skin layer and sponge-like supporting structure. Hansen's solubility parameters were calculated for different solvent systems and coagulation medium, and the predicted trends of their effect to the formation of skin layer and gas Separation Performance were consistent with the experimental observation. High CO 2 /CH 4 Separation factors (ranging up to 67) are achieved which are among the highest reported for purely polymeric hollow fibers without post-treatments and exceeded the commonly reported bulk values of Matrimid ® .

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Taishung Chung - One of the best experts on this subject based on the ideXlab platform.

  • superior gas Separation Performance of dual layer hollow fiber membranes with an ultrathin dense selective layer
    Journal of Membrane Science, 2008
    Co-Authors: Taishung Chung, Youchang Xiao
    Abstract:

    Abstract A concept demonstration has been made to simultaneously enhance both O2 and CO2 gas permeance and O2/N2 and CO2/CH4 selectivity via intelligently decoupling the effects of elongational and shear rates on dense-selective layer and optimizing spinning conditions in dual-layer hollow fiber fabrication. The dual-layer polyethersulfone hollow fiber membranes developed in this work exhibit an O2/N2 selectivity of 6.96 and an O2 permeance of 4.79 GPU which corresponds to an ultrathin dense-selective layer of 918 A at room temperature. These hollow fibers also show an impressive CO2/CH4 selectivity of 49.8 in the mixed gas system considering the intrinsic value of only 32 for polyethersulfone dense films. To our best knowledge, this is the first time to achieve such a high CO2/CH4 selectivity without incorporating any material modification. The above gas Separation Performance demonstrates that the optimization of dual-layer spinning conditions with balanced elongational and shear rates is an effective approach to produce superior hollow fiber membranes for oxygen enrichment and natural gas Separation.

  • effect of shear rate within the spinneret on morphology Separation Performance and mechanical properties of ultrafiltration polyethersulfone hollow fiber membranes
    Chemical Engineering Science, 2000
    Co-Authors: Taishung Chung, Juan Gu
    Abstract:

    Abstract The effect of shear rate within a spinneret during hollow fiber spinning on the morphology, permeability and Separation Performance, and mechanical properties of ultrafiltration polyethersulfone hollow fiber membranes has been investigated. Hollow fiber UF membranes were prepared from a dope solution containing Polyethersulfone (PES)/N-methyl-2-pyrrolidone (NMP)/Diethylene Glycol (DG) with a weight ratio of 13/45/42. This dope formulation was very close to its cloud point (binodal line) in order to speed up the coagulation of nascent fibers as much as possible so that the relaxation effect on molecular orientation was reduced. The wet-spinning process was purposely chosen to fabricate the hollow fibers without drawing and water was used as the external coagulant. Therefore, it is in the belief that the effects of gravity and elongation stress on fiber formation could be significantly reduced and the orientation induced by shear stress within the spinneret could be frozen into the wet-spun fibers. In order to minimize the complicated coupling effects of elongation stress and uneven external solvent exchange rate on fiber formation and the effect of inner skin resistance on Separation Performance of final fibers while the shear rate within the spinneret was increased from 245 to 2568 s−1, an optimized bore fluid of 86 wt% NMP in water was employed and a constant ratio of dope fluid flow rate to bore fluid flow rate was kept. Experimental results showed that a higher shear rate in the spinneret apparently resulted in a hollow fiber UF membrane with a thicker and/or a denser skin due to a greater molecular orientation. As a consequence, when the shear rate increased, pure water flux, coefficient of thermal expansion (CTE) and elongation of the final fibers decreased, but storage modulus, tensile strength and Young's modulus increased. For the first time, it was found that there was a certain critical value of shear rate below which the Separation Performance of fibers increased obviously while the flux decreased dramatically with an increase in shear rate but above which the Separation decreased slightly while the flux did not change. The results suggested that it was possible to dramatically enhance the production efficiency of hollow fiber UF membranes for the Separation of high Mw (>40 K) solutes with the same fiber dimension and similar Separation Performance by the approach proposed in this paper.

  • effect of dope flow rate on the morphology Separation Performance thermal and mechanical properties of ultrafiltration hollow fibre membranes
    Journal of Membrane Science, 1999
    Co-Authors: Taishung Chung
    Abstract:

    Abstract We have determined the effects of dope extrusion speed (or shear rate within a spinneret) during hollow fibre spinning on ultrafiltration membrane's morphology, permeability and Separation Performance, and thermal and mechanical properties. We purposely chose wet-spinning process to fabricate the hollow fibres without drawing and used water as the external coagulant in the belief that the effects of gravity and elongation stress on fibre formation could be significantly reduced and the orientation induced by shear stress within the spinneret could be frozen into the wet-spun fibres. An 86/14 (weight ratio) NMP/H 2 O mixture was employed as the bore fluid with a constant ratio of dope fluid to bore fluid flow rate while increasing the spinning speed from 2.0 to 17.2 m/min in order to minimise the complicated coupling effects of elongation stress, uneven external solvent exchange rates, and inner skin resistance on fibre formation and Separation Performance. Hollow fibre UF membranes were made from a dope solution containing polyethersulphone (PES)/ N -methyl-2-pyrrolidone (NMP)/diethylene glycol (DG) with a weight ratio of 18/42/40. This dope formulation was very close to its cloud point (binodal line) in order to speed up the coagulation of nascent fibres as much as possible so that the relaxation effect on molecular orientation was reduced. Experimental results suggested that a higher dope flow rate (shear rate) in the spinneret resulted in a hollow fibre UF membrane with a smaller pore size and a denser skin due to a greater molecular orientation. As a result, when the dope extrusion speed increased, pore size, water permeability, CTE and elongation of the final membranes decreased, but the Separation Performance, storage modulus, tensile strength and Young's modulus increased. Most surprisingly, for the first time, we found that there was a certain critical value, when the dope extrusion rate was over this value, the final fibre Performance could not be influenced significantly. The results suggested that it was possible to dramatically enhance the production efficiency of hollow fibre UF membranes with the same fibre dimension and similar Separation Performance by the method proposed in this paper.

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