Co-reporter:Faizal Soyekwo, Qiugen Zhang, Runsheng Gao, Yan Qu, Chenxiao Lin, Xiaoling Huang, Aimei Zhu, Qinglin Liu
Journal of Membrane Science 2017 Volume 524() pp:174-185
Publication Date(Web):15 February 2017
DOI:10.1016/j.memsci.2016.11.019
•Highly-permeable nanofiltration membranes are fabricated via the facile approach.•Ultrathin cellulose nanofiber membrane is utilized as the intermediate layer.•The 77.4 nm-thick membrane has the molecular weight cut-off of 824 g mol−1.•The 77.4 nm-thick membrane has the pure water flux of up to 32.7 l m−2 h−1 bar−1.•The membranes have a great potential application in fast water purification.Highly-permeable nanofiltration membranes are highly desired in water production and dissolved solutes removal due to environmental and energy concerns. Here a facile approach is presented to prepare ultrathin polymeric nanofiltration membrane using surface modification of ultrafine cellulose nanofiber (UCN) membrane via interfacial polymerization. The hydrophilic UCN membrane endows an interconnected nanoporous microstructure containing free spaces for the growth of the crosslinked-PEI layer creating narrow permeation channels that are responsible for the transport of water moleucles. The resultant membranes comprising an ultrathin selective layer intertwined with cellulose nanofiber matrix are smooth and allow fast permeation of water. Typically, the 77.4 nm-thick membrane with a mean pore size of about 0.45 nm and molecular weight cut-off of 824 g mol−1 has a high pure water flux of 32.7 L m−2 h−1 bar−1 that is an order of magnitude higher than those of previously reported similar nanofiltration membranes. The membranes are also positively charged and display high permeation flux and sufficient rejections for inorganic salts and organic dyes in the water purification. Further performance evaluation using model synthetic wastewater demonstrates the membranes have a great potential in the wastewater treatment. This approach presents a promising strategy for the development of highly-permeable nanofiltration membranes for fast water purification and high-efficient separation of small molecules.
Co-reporter:Xiu Qin Wang, Chen Xiao Lin, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
International Journal of Hydrogen Energy 2017 Volume 42, Issue 30(Volume 42, Issue 30) pp:
Publication Date(Web):27 July 2017
DOI:10.1016/j.ijhydene.2017.06.186
•A straightforward scheme to prepare poly (ether sulfone)-based AEMs.•Cationic groups was linked to backbone via long alkyl flexible spacers.•Obvious phase separation morphology was well formed.•Robust mechanical properties and good thermal stability was achieved.Facile synthesis of poly (ether sulfone)-based anion exchange membranes (AEMs) bearing flexible pendent quaternary ammonium (QA) groups for fuel cells is reported. (2,3-Epoxypropyl) trimethyl ammonium chloride (EPTMAC) is directly grafted onto the hydroxyl-bearing poly (ether sulfone) (PES) backbone via one-step ring-opening reaction to introduce ion conductive moieties. This scheme is more straightforward than the conventional two-step functionalization approach via chloromethylation or radical-initiated bromination and Menshutkin reactions. This method can be used to control the degree of functionalization of QA-containing PES easily. 2D nuclear overhauser effect spectroscopy (NOESY) shows that QA groups aggregate and self-assemble in the functionalized-PES solutions which are in favor of fabricating a membrane with phase separation morphology, as well as confirmed by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). These resulting AEMs exhibit reasonable hydroxide conductivity, low water uptake, high power density, and desirable durability in a single fuel cell. This suggests that they are good candidates for fuel cells.Download high-res image (351KB)Download full-size image
Co-reporter:Chen Xiao Lin, Xiu Qin Wang, Ling Li, Fang Hua Liu, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Power Sources 2017 Volume 365(Volume 365) pp:
Publication Date(Web):15 October 2017
DOI:10.1016/j.jpowsour.2017.08.100
•Triblock copolymer AEMs bearing alkyl-tethered head-groups were prepared.•Well-connected ionic domains were formed in the membranes.•The AEMs exhibited a highest conductivity of 105.1 mS cm−1 at 80 °C.•The AEMs have good thermal stability and robust alkaline stability.To explore highly conductive and alkaline stable anion exchange membrane (AEM) materials, triblock copolymers bearing alkyl-tethered cycloaliphatic quaternary ammonium-head-groups are prepared via nucleophilic substitution, Friedel-Crafts acylation, ketone reduction and Menshutkin reaction. The designed triblock copolymers composed of quaternized poly(phenylene oxide) segments and poly(ether sulfone) segments are responsible for the microphase separated morphology and well-connected ion domains, as confirmed by transmission electron microscopy. The highest conductivity, up to 105.1 mS cm−1 at 80 °C is achieved for the AEM with ionic exchange capacity (IEC) of 1.81 meq g−1. Furthermore, the AEMs show robust alkaline stability due to the alkyl-tethered cation-head-groups structure. High retention of hydroxide conductivity (88.9%) and IEC (91.2%) is observed for the AEMs via degradation test in a 1 M aqueous KOH solution at 80 °C for 480 h. Based on the AEM with high conductivity, a H2/O2 fuel cell achieves a peak power density of 176.5 mW cm−2 (80 °C) at a current density of 500 mA cm−2.Download high-res image (346KB)Download full-size image
Co-reporter:Chen Xiao Lin, Yi Zhi Zhuo, En Ning Hu, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2017 Volume 539(Volume 539) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.memsci.2017.05.063
•AEMs were prepared via thermal crosslinking between trifluorovinyl groups.•The prepared procedure avoids the use of catalyst.•The crosslinked segment is away from ionic domain.•The crosslinked AEMs demonstrated high dimensional stability.•The AEM exhibit a highest conductivity of 77.1 mS cm−1 at 80 °C.Covalent crosslinking is considered to be a promising strategy to balance the dimensional stability and conductivity of anion exchange membranes (AEMs). Nevertheless, crosslinking using diamine crosslinkers would introduce hydrophobic alkyl chains into the ionic domain resulting in a significant decline in hydroxide conductivity and crosslinking via catalyst is discouraged. Herein, we presented a strategy for preparing crosslinked AEMs without using catalyst and the crosslinked moiety is away from the ionic domain. The crosslinking was carried out by converting the trifluorovinyl groups into perfluorocyclobutane groups via thermal treatment. The designed side-chain structure is responsible for the obvious hydrophilic/hydrophobic phase separated morphology and interconnected ion conducting channels, as confirmed by atomic force microscopy, transmission electron microscopy and small angle X-ray scattering. The obtained membrane exhibited high dimensional stability and a highest conductivity of 77.1 mS cm−1 at 80 °C. Furthermore, the crosslinked AEMs also had robust mechanical properties, good thermal stability and reasonable alkaline stability.Download high-res image (314KB)Download full-size image
Co-reporter:Dong Guo, Chen Xiao Lin, En Ning Hu, Lin Shi, Faizal Soyekwo, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2017 Volume 541(Volume 541) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.memsci.2017.07.007
•Alkaline membranes with clustered multi-imidazolium side chains were prepared.•Effect of the multication structure on the morphology and properties was studied.•OH− conductivity of the clustered cationic membrane is in excess of 120 mS cm−1.•A peak power density of 134 mW cm−2 of the H2/O2 fuel cell is achieved at 60 °C.Clustered alkyl side chains bearing a string of three imidazolium cations with hexyl spacers are grafted to fluorene-based poly (arylene ether sulfone) successfully. Nanostructure is directly configured within the anion exchange membranes (AEMs) via the novel multi-cation side chains. As confirmed by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS), percolating OH– conducting channels with the size of ionic clusters nearly 20 nm endow the trimPES-0.4 membrane with an excellent ion conductivity in excess of 120 mS cm–1 at 80 °C. Because of the self-assembly of ionic groups, water molecules are compartmentalized into the hydrophilic side chain regions instead of backbones, resulting in advantageous over water management. Together with the lengthened hydrophobic segments, TrimPES-0.2 exhibits superior dimensional stability (12.0%, 30 °C) to conventional mono-cation type AEMs. Furthermore, the novel multi-cation TrimPES-0.4 displays a peak power density of 134.4 mW cm–2 at a current density of 280 mA cm–2. Therefore, these findings suggest that by tuning the distribution of cations, AEMs with well-balanced performance can be made for fuel cell applications.
Co-reporter:Xiao Ling Huang;Chen Xiao Lin;En Ning Hu;Faizal Soyekwo;Qiu Gen Zhang;Ai Mei Zhu
RSC Advances (2011-Present) 2017 vol. 7(Issue 44) pp:27342-27353
Publication Date(Web):2017/05/22
DOI:10.1039/C7RA04170E
A series of novel macrocrosslinked imidazolium-based anion exchange membranes (AEMs) with high hydroxide conductivity and dimensional stability were synthesized by crosslinking a poly(vinyl imidazole) ionic liquid with bromide-terminated poly(ether sulfone) via Menshutkin reaction. Fourier transform infrared (FT-IR) and energy dispersive spectrometry (EDS) were used to confirm the chemical structure and successful crosslinking of the AEMs. The contiguous imidazolium cations along the polyolefin backbone are found to aggregate and connect to form continuous hydroxide transport microchannels by the introduction of long hydrophobic poly(ether sulfone) chain as evidenced by atomic force microscopy (AFM). As a consequence, a high hydroxide conductivity of 78.5 mS cm−1 was achieved for the crosslinked PES/PVIIL-0.4 membrane at 80 °C. A single cell test using the PES/PVIIL-0.4 membrane exhibits an open circuit voltage of 1.039 V and peak power density of 109.5 mW cm−2 at the current density of 190 mA cm−2 at 60 °C. This newly developed strategy holds great promise to prevent fuel crossover in alkaline fuel cells.
Co-reporter:Chen Xiao Lin, Xiu Qin Wang, En Ning Hu, Qian Yang, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2017 Volume 541(Volume 541) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.memsci.2017.07.032
•The triblock polymers backbone contains no C-O linkages.•Cationic groups are attached to backbone via long alkyl spacers.•The AEMs have robust alkaline stability and good thermal stability.Alkaline stability is the critical issue for the practical application of anion exchange membranes (AEMs) in fuel cells. The benzyltrimethyl ammonium and backbone with C-O linkages of the traditional AEMs are susceptible to attack by hydroxide ions resulting in poor alkaline stability of the AEMs. Herein, we present the preparation of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) triblock copolymer via grafting, ketone reduction and quaternization for AEM fuel cell applications. The quaternary ammonium (QA) groups are attached to the SEBS backbone free of C-O linkages via long flexible alkyl spacers, which are responsible for the robust alkaline stability of the AEMs. Thus, the hydroxide conductivity of SEBS-CH2-QA-1.5 was only decreased by 7.7% and 13.7% after immersing the membranes into a 1 M aqueous KOH solution at 60 and 90 °C for 360 h, respectively. Furthermore, SEBS-CH2-QA-1.5 with IEC of 1.23 meq g−1 exhibits a maximum hydroxide conductivity of 56.4 mS cm−1 at 80 °C and a maximum power density of 94.6 mW cm−2 under a current density of 300 mA cm−2.Download high-res image (224KB)Download full-size image
Co-reporter:Faizal Soyekwo;Qiugen Zhang;Runsheng Gao;Yan Qu;Ruixue Lv;Mengmeng Chen;Aimei Zhu;Qinglin Liu
Journal of Materials Chemistry A 2017 vol. 5(Issue 2) pp:583-592
Publication Date(Web):2017/01/03
DOI:10.1039/C6TA07567C
The development of inorganic functionalized membranes with the capacity to effectively separate molecules or ions in solutions based on the size or electrostatic interactions is pivotal to purification and separation applications. Herein, we demonstrate a novel green strategy utilizing a completely aqueous process to construct an asymmetrically structured metal surface functionalized polymer–matrix nanocomposite nanofiltration membrane. Crosslinked polyethyleneimine (PEI) is grafted on a carboxylated carbon nanotube intermediate layer incorporated into the macroporous cellulose acetate substrate to form the composite membrane. The resulting membrane is subsequently inorganically modified via an in situ surface reaction of zinc nitrate with excess ammonium hydroxide to produce the hydrophilic and positively charged membrane. Crosslinking enhances the polymer interaction with the carbon nanotube interlayer which in turn endows it with mechanical strength and sustains the membrane pore structure during pressure driven filtration. The functionalized membrane displays outstanding pure water flux of 16.5 ± 1.3 L m−2 h−1 bar−1 while exhibiting good nanofiltration performance of bivalent cations, which is ascribed to the electrostatic repulsion via the Donnan exclusion effect. Meanwhile the membranes exhibit excellent separation of organic molecules and long-term filtration stability. This newly developed approach presents a promising route for the construction of highly permeable nanofiltration membranes for fast purification and separation applications.
Co-reporter:Dong Guo, Ao Nan Lai, Chen Xiao Lin, Qiu Gen Zhang, Ai Mei Zhu, and Qing Lin Liu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 38) pp:25279
Publication Date(Web):August 31, 2016
DOI:10.1021/acsami.6b07711
With the intention of optimizing the performance of anion-exchange membranes (AEMs), a set of imidazolium-functionalized poly(arylene ether sulfone)s with densely distributed long flexible aliphatic side chains were synthesized. The membranes made from the as-synthesized polymers are robust, transparent, and endowed with microphase segregation capability. The ionic exchange capacity (IEC), hydroxide conductivity, water uptake, thermal stability, and alkaline resistance of the AEMs were evaluated in detail for fuel cell applications. Morphological observation with the use of atomic force microscopy and small-angle X-ray scattering reveals that the combination of high-local-density-type and side-chain-type architectures induces distinguished nanophase separation in the AEMs. The as-prepared membranes have advantages in effective water management and ionic conductivity over traditional main-chain polymers. Typically, the conductivity and IEC were in the ranges of 57.3–112.5 mS cm–1 and 1.35–1.84 mequiv g–1 at 80 °C, respectively. Furthermore, the membranes exhibit good thermal and alkaline stability and achieve a peak power density of 114.5 mW cm–2 at a current density of 250.1 mA cm–2. Therefore, the present polymers containing clustered flexible pendent aliphatic imidazolium promise to be attractive AEM materials for fuel cells.Keywords: anion-exchange membranes; flexible side chains; fuel cell application; ion conduction; phase separation
Co-reporter:Ao Nan Lai, Dong Guo, Chen Xiao Lin, Qiu Gen Zhang, Ai Mei Zhu, Mei Ling Ye, Qing Lin Liu
Journal of Power Sources 2016 Volume 327() pp:56-66
Publication Date(Web):30 September 2016
DOI:10.1016/j.jpowsour.2016.07.043
•Crosslinked AEMs was prepared via crosslinking of ion cluster regions.•Effect of crosslinking on AEMs' morphology and properties was studied.•The AEMs showed high ionic conductivity in the range 52.2–143.4 mS cm−1.•The AEMs showed superb ratio of relative conductivity to relative swelling.•The single cell achieved a peak power density of 83.6 mW cm−2 at 80 °C.Development of anion exchange membranes (AEMs) with high hydroxide conductivity, good dimensional and alkaline stabilities is still a challenge for the practical application of AEM fuel cells. In this study, we report a new strategy to prepare high-performance AEMs with crosslinked ionic regions. A series of phenolphthalein-containing poly(arylene ether sulfone)s crosslinked AEMs was synthesized by grafting ion groups selectively and densely on the phenolphthalein units to form ion clusters that are further crosslinked to generate the hydrophilic ionic regions. The crosslinking reaction not only improved the dimensional stability of the AEMs, but also increased the aggregation of the ion clusters leading to the formation of hydrophilic/hydrophobic phase-separated morphology and ion-conducting channels. As a result, enhancements in both ion conductivity and dimensional stability can be achieved. The crosslinked AEMs showed high hydroxide conductivities in the range of 52.2–143.4 mS cm−1 from 30 to 80 °C and a superb ratio of relative conductivity to relative swelling at 80 °C. Furthermore, the crosslinked AEMs also exhibited good mechanical properties, thermal and alkaline stabilities and desirable single cell performance. This work presents a promising strategy for the synthesis of high-performance AEMs for fuel cells.
Co-reporter:Chen Xiao Lin, Yi Zhi Zhuo, Ao Nan Lai, Qiu Gen Zhang, Ai Mei Zhu and Qing Lin Liu
RSC Advances 2016 vol. 6(Issue 21) pp:17269-17279
Publication Date(Web):04 Feb 2016
DOI:10.1039/C5RA22774G
A series of novel comb-shaped phenolphthalein-based poly(ether sulfone)s was synthesized for preparing anion exchange membranes (AEMs). Hexadecyldimethylamine with a long alkyl chain was used as the quaternization reagent to form a comb-shaped architecture of the copolymers. Due to the presence of a long alkyl side chain with hydrophobicity, the as-synthesized comb-shaped AEMs possess a self-anti-swelling property resulting in a low water uptake and swelling ratio. The PES-B100-C16 membrane exhibits excellent alkaline stability due to the presence of large volumetric β-alkyl chains linking to the cationic group that resist the attack of OH−, and retain available ionic conductivity in a 2 M KOH solution at 60 °C for 360 h. An open circuit voltage of the single cell reached 0.67 V, and the maximum power density was 43 mW cm2 at a current density of 125 mA cm−2 without optimization in a single H2/O2 alkaline fuel cell at 50 °C.
Co-reporter:Faizal Soyekwo;Qiu Gen Zhang;Xiao Chen Lin;Xin Mei Wu;Ai Mei Zhu
Journal of Applied Polymer Science 2016 Volume 133( Issue 24) pp:
Publication Date(Web):
DOI:10.1002/app.43544
ABSTRACT
Ultrafiltration (UF) is a size selective pressure-driven membrane separation process increasingly required for high efficient water treatment and suspended solids removal in many industrial applications. This study examined the morphology of as-prepared cellulose nanofibers and then utilized the nanofibers dispersion to fabricate nanofibrous nanoporous membranes with potential wide applications in various fields including water treatment. The nanofibers were prepared using a simple and powerful mechanical high intensity ultrasonication following a pre-chemical treatment of α-cellulose. The cellulose nanofibers’ morphology, crystallinity, and yield were found to be influenced by pre-chemical treatment. Cellulose nanofibrous membranes were fabricated from cellulose nanofibers dispersion on a porous support. A nanoporous structure with an extensive interconnected network of fine cellulose nanofibers was formed on the support substrate. The resulting membranes exhibited typical and high-efficient UF performances with high water fluxes of up to 2.75 103 L/m2/h/bar. The membranes also displayed high rejections for ferritin and 10 nm gold nanoparticles with a reactive surface area capable of rapidly decolorizing methylene blue from its aqueous solution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43544.
Co-reporter:Yi Zhi Zhuo, Ao Lan Lai, Qiu Gen Zhang, Ai Mei Zhu, Mei Ling Ye and Qing Lin Liu
Journal of Materials Chemistry A 2015 vol. 3(Issue 35) pp:18105-18114
Publication Date(Web):29 Jul 2015
DOI:10.1039/C5TA04257G
Anion exchange membranes (AEMs) have been recognized as one of the most prospective polyelectrolytes for fuel cells due to their faster electrode reaction kinetics and the potential of adopting cheaper metal catalysts against proton exchange membranes (PEMs). Herein, a series of poly(arylene ether sulfone)s containing a flexible pendant imidazolium cation were synthesized by grafting bromine-bearing imidazolium-based ionic liquids into a hydroxyl-bearing poly(ether sulfone) matrix. 1H NMR spectroscopy was used to confirm the as-synthesized copolymers. Atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) were used to characterize the morphology of the membranes. The incorporation of the flexible side-chain imidazolium groups is beneficial to the aggregation of the ionic clusters leading to the formation of hydrophilic/hydrophobic phase-separated morphology and nano-channels. As a result, an enhancement in the ionic conductivity can be achieved. Therefore, the as-prepared AEMs possess higher ionic conductivity than traditional benzyl-type AEMs. The weight-based ion exchange capacity (IECw) of the membranes was in the range of 1.01–1.90 meq. g−1. Correspondingly, their ionic conductivity was in the range of 22.13–59.19 and 51.66–108.53 mS cm−1 at 30 and 80 °C, respectively. Moreover, the membranes also exhibit good alkaline stability and interesting single cell performance. This work presents a facile and universal route for the synthesis of AEMs with superior performance.
Co-reporter:Ao Nan Lai, Li Sha Wang, Chen Xiao Lin, Yi Zhi Zhuo, Qiu Gen Zhang, Ai Mei Zhu, and Qing Lin Liu
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 15) pp:8284
Publication Date(Web):March 31, 2015
DOI:10.1021/acsami.5b01475
A series of phenolphthalein-based poly(arylene ether sulfone nitrile)s (PESN) multiblock copolymers containing 1–methylimidazole groups (ImPESN) were synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. The ion groups were introduced selectively and densely on the unit of phenolphthalein as the hydrophilic segments, allowing for the formation of ion clusters. Strong polar nitrile groups were introduced into the hydrophobic segments with the intention of improving the dimensional stability of the AEMs. A well-controlled multiblock structure was responsible for the well-defined hydrophobic/hydrophilic phase separation and interconnected ion–transport channels, as confirmed by atomic force microscopy and small angle X-ray scattering. The ImPESN membranes with low swelling showed a relatively high water uptake, high hydroxide ion conductivity together with good mechanical, thermal and alkaline stability. The ionic conductivity of the membranes was in the range of 3.85–14.67 × 10–2 S·cm–1 from 30 to 80 °C. Moreover, a single H2/O2 fuel cell with the ImPESN membrane showed an open circuit voltage of 0.92 V and a maximum power density of 66.4 mW cm–2 at 60 °C.Keywords: alkaline fuel cells; anion exchange membrane; multiblock copolymer; phenolphthalein; poly(arylene ether sulfone nitrile);
Co-reporter:Ao Nan Lai, Li Sha Wang, Chen Xiao Lin, Yi Zhi Zhuo, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2015 Volume 481() pp:9-18
Publication Date(Web):1 May 2015
DOI:10.1016/j.memsci.2015.02.013
•The nitrile dipole interchain interactions induced a self-crosslinked structure.•Benzylmethyl-containing poly(arylene ether nitrile) was synthesized.•AEMs show high ionic conductivity above the magnitude of 10−2 S cm−1.•The AEMs show excellent alkaline stability in a 2 M NaOH solution at 60 °C.A series of novel quaternized benzylmethyl-containing poly(arylene ether nitrile)s (QPENs) were synthesized via condensation polymerization, bromination and quaternization. N,N,N′,N′-tetramethyl-1,6-diaminohexane dissolved in isopropanol was used as the quaternization reagent for the preparation of target anion exchange membranes (AEMs). 1H NMR spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC) were used to characterize the as-synthesized copolymers. The ratio of hydrophilic to hydrophobic segment on the polymer backbone was varied to study the structure–property of the AEMs. With strong nitrile dipole interchain interactions and a self-crosslinked structure, the resulting AEMs possess a self-anti-swelling property resulting in a low water uptake and swelling ratio. The AEMs show high ionic conductivity (under hydrated conditions) above the magnitude of 10−2 S cm−1. The membranes with distinct phase separation morphology have a higher ionic exchange capacity (IEC). The methanol permeability of the AEMs in the range 3.18–9.69×10−8 cm2 s−1 at 30 °C and 8.92–25.57×10−8 cm2 s−1 at 60 °C is lower than that of Nafion®117. The AEMs show an excellent alkaline stability in a 2 M NaOH solution at 60 °C for 1080 h. A single cell with the QPEN membrane shows an open circuit voltage of 0.84 V. A maximum power density of 79.1 mW cm−2 at a current density of 207 mA cm−2 can be achieved at 60 °C. In summary the AEMs are good candidates for evaluation in fuel cells.
Co-reporter:Yuming Hu, Aimei Zhu, Qiugen Zhang, Qinglin Liu
Journal of Power Sources 2015 Volume 299() pp:443-450
Publication Date(Web):20 December 2015
DOI:10.1016/j.jpowsour.2015.09.021
•Hollow Pt/Ru core–shell catalysts with nanochannels were synthesized.•Integrity of the Pt shell could be easily controlled by varying the H2PtCl6 content.•The H–PtRu catalysts showed high catalytic activity for MOR.•The H–PtRu catalyst with high Ru content showed the highest stability.This work reports the preparation of hollow PtRu core–shell catalysts with TiO2 as template, in which the Pt nanoparticles (NPs) grow on the exterior surface of Ru layer. The quantity of Pt NPs is easily tailored to control the integrity of Pt shell through varying the concentration of H2PtCl6 solution. Scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and selected-area electron diffraction (SAED) are used to characterize the structure and morphology of H–PtRu. The core–shell structure is confirmed by the high-angle annular dark-field scanning TEM (HAADF-STEM) with energy-disperse X-ray spectroscopy (EDX). The electrochemical performance of H–PtRu is investigated by cyclic voltammetry and chronoamperometry. Results show that the catalytic activity of H–PtRu toward methanol oxidation reaction (MOR) is ∼2.5 times higher than that of Pt/C (JM), and the electrocatalytic stability improves with the increase of Ru content. Furthermore, H–PtRu exhibits better stability for methanol oxidation compared to Pt/C (JM) and PtRu/C (JM).
Co-reporter:Ao Nan Lai, Yi Zhi Zhuo, Chen Xiao Lin, Qiu Gen Zhang, Ai Mei Zhu, Mei Ling Ye and Qing Lin Liu
RSC Advances 2015 vol. 5(Issue 106) pp:86980-86989
Publication Date(Web):09 Oct 2015
DOI:10.1039/C5RA16946A
Two series of novel poly(arylene ether sulfone nitrile) (PESN) multiblock copolymers are synthesized to prepare anion exchange membranes (AEMs) for alkaline fuel cells. To study the effect of phenolphthalein groups on the structure and properties of the membranes, the ion groups facilitating the formation of ion clusters are selectively and densely located on the phenolphthalein-sulfone segments of one and on the bisphenol A-sulfone segments of the other. The morphology and structure of the membranes are observed by atomic force microscopy and small angle X-ray scattering. The phenolphthalein-containing type endows the AEMs with a much clearer and more-defined microphase-separated structure leading to the formation of much larger and more developed interconnected ion-transport channels. As a result, high hydroxide conductivity (in the range of 2.04–12.98 × 10−2 S cm−1 from 30 to 80 °C) and H2/O2 fuel cell performance (an open circuit voltage of 0.92 V and a maximum power density of 66.4 mW cm−2 at 60 °C) can be achieved. Furthermore, the phenolphthalein-containing AEMs also show higher water uptake and mechanical strength, lower swelling ratio, and higher thermal and alkaline stability than the phenolphthalein-free AEMs.
Co-reporter:Ke Zhou, Qiu Gen Zhang, Hong Mei Li, Nan Nan Guo, Ai Mei Zhu and Qing Lin Liu
Nanoscale 2014 vol. 6(Issue 17) pp:10363-10369
Publication Date(Web):03 Jul 2014
DOI:10.1039/C4NR03227F
Oily wastewater is generated in diverse industrial processes, and its treatment has become crucial due to increasing environmental concerns. Herein, novel ultrathin nanoporous membranes of cellulose nanosheets have been fabricated for separation of oil-in-water nanoemulsions. The fabrication approach is facile and environmentally friendly, in which cellulose nanosheets are prepared by freeze-extraction of a very dilute cellulose solution. The as-prepared membranes have a cellulose nanosheet layer with a cut-off of 10–12 nm and a controllable thickness of 80–220 nm. They allow ultrafast water permeation and exhibit excellent size-selective separation properties. A 112 nm-thick membrane has a water flux of 1620 l m−2 h−1 bar−1 and a ferritin rejection of 92.5%. These membranes have been applied to remove oil from its aqueous nanoemulsions successfully, and they show an ultrafast and effective separation of oil-in-water nanoemulsions. The newly developed ultrathin cellulose membranes have a wide application in oily wastewater treatment, separation and purification of nanomaterials.
Co-reporter:Pei Yu Xu, Ke Zhou, Guang Lu Han, Qiu Gen Zhang, Ai Mei Zhu, and Qing Lin Liu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 9) pp:6776
Publication Date(Web):April 8, 2014
DOI:10.1021/am5017599
Two kinds of novel multiblock poly(arylene ether sulfone)s were synthesized via block copolycondensation of telechelic oligomers as a starting material for the preparation of anion-exchange membranes (AEMs). The as-synthesized copolymers have extremely similar main chains. The difference is that the benzylmethyl groups for one are located on the fluorene–sulfone segments and they are located on the isopropylidene–sulfone segments for the other. The benzylmethyl moieties served as precursors to cationic sites and were brominated using N-bromosuccinimide (NBS) and then quaternized with N,N,N′,N′-tetramethyl-1,6-diaminohexane (TMHDA). Controlled bromination and quaternization at specific positions of the benzylmethy-containing fluorene–sulfone segments and isopropylidene–sulfone segments can be achieved. 1H NMR spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography were used to characterize the as-synthesized copolymers. Distinct microphase separation in the as-prepared AEMs was observed using small-angle X-ray scattering and transmission electron microscopy. The AEM containing fluorene–sulfone segments (IEC = 1.89 meq·g–1) showed higher ionic conductivity and methanol permeability than that containing isopropylidene–sulfone segments (IEC = 2.03 meq·g–1). Moreover, the former showed better alkaline stability than the latter.Keywords: alkaline stability; anion-exchange membranes; ionic conductivity; methanol permeability; microphase separation; poly(arylene ether sulfone);
Co-reporter:Yi Gong, Ai Mei Zhu, Qiu Gen Zhang and Qing Lin Liu
RSC Advances 2014 vol. 4(Issue 19) pp:9445-9450
Publication Date(Web):27 Jan 2014
DOI:10.1039/C3RA47405D
We first report the synthesis of colloidosomes via UV crosslinking of PVP-coated microgels. The photo-crosslinkable poly(N-vinyl-2-pyrrolidone) (PVP) was coated as a layer on the surface of poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AAc)) microgels at pH = 3.5. A toluene-in-water Mickering emulsion was further fabricated based on the resulting PVP/P(NIPAM-co-AAc) microgels and then exposed to UV irradiation leading to the formation of colloidosomes. Since only the microgels on the surface of emulsion droplets could be crosslinked by UV irradiation, the yield and the mean size of the colloidosomes can be controlled by the amount of toluene used in the preparation. The proposed method presents a new platform to fabricate colloidosomes since photo-responsive comonomers or/and chemical crosslinkers are not essential in the system. The colloidosomes can be used as a vehicle for both hydrophilic and hydrophobic dyes. The release of the encapsulated dyes can be controlled by temperature.
Co-reporter:Faizal Soyekwo, Qiu Gen Zhang, Chao Deng, Yi Gong, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2014 454() pp: 339-345
Publication Date(Web):
DOI:10.1016/j.memsci.2013.12.014
Co-reporter:Guang Lu Han, Ke Zhou, Ao Nan Lai, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2014 454() pp: 36-43
Publication Date(Web):
DOI:10.1016/j.memsci.2013.11.049
Co-reporter:Pei Yu Xu, Ke Zhou, Guang Lu Han, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2014 457() pp: 29-38
Publication Date(Web):
DOI:10.1016/j.memsci.2014.01.042
Co-reporter:Guang Lu Han, Pei Yu Xu, Ke Zhou, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2014 464() pp: 72-79
Publication Date(Web):
DOI:10.1016/j.memsci.2014.03.062
Co-reporter:Chao Deng, Qiu Gen Zhang, Guang Lu Han, Yi Gong, Ai Mei Zhu and Qing Lin Liu
Nanoscale 2013 vol. 5(Issue 22) pp:11028-11034
Publication Date(Web):06 Sep 2013
DOI:10.1039/C3NR03362G
Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5–12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m−2 h−1 bar−1) that is an order of magnitude larger than commercial membranes, and can highly efficiently separate 5 and 15 nm gold nanoparticles from their mixtures. The newly developed nanoporous membranes have a wide application in separation and purification of biomacromolecules and nanoparticles.
Co-reporter:Yi Gong, Ai Mei Zhu, Qiu Gen Zhang, Mei Ling Ye, Hai Tao Wang, and Qing Lin Liu
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 21) pp:10682
Publication Date(Web):October 4, 2013
DOI:10.1021/am402787x
Cell encapsulation by locking the interfacial microgels in a water-in-oil Pickering emulsion has currently been attracting intensive attention because of the biofriendly reaction condition. Various kinds of functional microgels can only stabilize an oil-in-water Pickering emulsion, and it is thus difficult to encapsulate cells in the emulsion where the cells are usually dispersed in the continuous phase. Herein, we introduce a facile method for preparing cell-embedded colloidosomes in an oil-in-water emulsion via polyelectrolyte complexation. Escherichia coli (E. coli) was chosen as a model cell and embedded in the thin shell of chitosan/poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AAc)) microcapsules. This is beneficial for expressing cell function because of the little resistance of mass exchange between the embedded cells and the external environment. Cells can be used in biocatalysis or biomedicine and our product will hold great promises to improve the performance in those fields. The synthesis route presents a platform to prepare cell-embedded microcapsules in an oil-in-water Pickering emulsion in a facile and biocompatible way. First, an emulsion stabilized by P(NIPAM-co-AAc) microgels was prepared. Then, the interfacial microgels in the emulsion were locked by chitosan to form colloidosomes. The mechanism of cell encapsulation in this system was studied via fluorescent labeling. The viability of E. coli after encapsulation is ca. 90%. Encapsulated E. coli is able to metabolize glucose from solution, and exhibits a slower rate than free E. coli. This demonstrates a diffusion constraint through the colloidosome shell.Keywords: cell encapsulation; microgels; o/w emulsion; P(NIPAM-co-AAc); Pickering emulsion; polyelectrolyte complexation;
Co-reporter:Qiu Gen Zhang, Guang Lu Han, Wen Wei Hu, Ai Mei Zhu, and Qing Lin Liu
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 22) pp:7541-7549
Publication Date(Web):May 16, 2013
DOI:10.1021/ie400290z
New organic–inorganic hybrid membranes prepared from chitosan, polyvinylpyrrolidone (PVP), and 1,2-bis(triethoxysilyl)ethane (BTEE) were used for pervaporation separation of methanol–ethylene glycol (EG) mixtures. A semi-interpenetrating network structure at the molecular scale was formed via condensation between chitosan and BTEE in the hybrid membranes. The self-condensation reaction of BTEE took place to form silica nanoparticles. The as-prepared hybrid membranes have denser packing of polymer chains, and higher mechanical strength than their untreated blended counterparts. BTEE hybridization efficiently decreased the membrane swelling in methanol–EG mixture, and enhanced methanol sorption selectivity. Effect of BTEE loading, feed temperature, and feed content on pervaporation performance was investigated in detail. Methanol/EG selectivity increased significantly, whereas membrane permeance decreased, with increasing BTEE loading. The membrane containing 10.4 wt % BTEE has the highest separation factor of 6129 for separation of methanol (6 wt %)–EG mixture at 60 °C.
Co-reporter:Rong Huang, Aimei Zhu, Yi Gong, Qiugen Zhang, and Qinglin Liu
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 22) pp:7432-7438
Publication Date(Web):May 10, 2013
DOI:10.1021/ie400573c
Bimetallic hollow PtAu sphere (H-PtAu) was prepared with TiO2 (titanium glycolate spheres) as a template in the presence of citric acid, and the template was removed during the formation of H-PtAu. The morphology and surface structure of H-PtAu were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The results show that the structure of hollow sphere is strongly dependent on the concentration of citric acid. The H-PtAu with uniform size is well dispersed; the Pt shell thickness can be controlled by the amount of Pt precursor. Electrocatalytic activities of H-PtAu with different Pt/Au atomic ratios were investigated by cyclic voltammetry (CV) in 0.5 M NaOH + 0.5 M methanol aqueous solution. Results show that H-PtAu catalyst has higher methanol oxidation activity than the commercial Pt/C (JM) catalyst, and the optimal Pt/Au molar ratio is 1.0.
Co-reporter:Qiu Gen Zhang, Wen Wei Hu, Ai Mei Zhu and Qing Lin Liu
RSC Advances 2013 vol. 3(Issue 6) pp:1855-1861
Publication Date(Web):27 Nov 2012
DOI:10.1039/C2RA21827E
Chitosan is an important biomacromolecule and polyvinylpyrrolidone (PVP) is a biocompatible synthetic polymer. The crosslinked chitosan/PVP blended membranes were prepared via UV irradiation. The as-prepared membranes have a highly crosslinked chitosan/PVP network structure originated from self-crosslinking of PVP and branching of chitosan onto PVP chains during UV irradiation. UV-Crosslinking significantly enhanced the mechanical strength and thermal stability of the blended membranes. Their highest tensile strength is twice as much as that of the pristine chitosan membrane. Maintaining the same swelling degree of the pristine chitosan membrane, the blended membranes have high sorption selectivity towards methanol and water. The as-prepared membranes exhibit an excellent performance in pervaporation separation of methanol/ethylene glycol and water/ethanol and show great potential as new biomedical materials and in the removal of alcohol and water from organics.
Co-reporter:Guang Lu Han, Qiu Gen Zhang, Ai Mei Zhu, Qing Lin Liu
Separation and Purification Technology 2013 Volume 107() pp:211-218
Publication Date(Web):2 April 2013
DOI:10.1016/j.seppur.2013.01.039
Membranes based on polyarylethersulfone with cardo (PES-C) were prepared for pervaporation (PV) separation of methanol (MeOH)/methyl tert-butyl ether (MTBE) mixtures. The membranes were characterized using wide angle X-ray diffraction (WAXRD), scanning electron microscopy (SEM) and contact angle metering. The swelling and mechanical properties of the membranes in MeOH/MTBE mixtures were studied. The degree of swelling (DS) was less than 7% originating from the good solvent proof and excellent mechanical properties of PES-C. N-methyl pyrrolidone (NMP) is found to be the optimum solvent for PES-C membrane preparation against N,N-dimethylformamide (DMF). The effect of annealing temperature and annealing time on the structure and PV performance of the PES-C membranes was thoroughly discussed. The results showed that increasing annealing temperature or annealing time would enhance MeOH permselectivity and reduce permeation flux. By varying feed MeOH content from 5 to 40 wt.%, permeation flux increased from 1.21 to 4.52 kg μm m−2 h−1, and MeOH content in the permeate was almost constant. The permeation flux increased and MeOH permselectivity decreased with increasing feed temperature.Highlights► Polyarylethersulfone with cardo membranes were prepared for pervaporation. ► The degree of swelling of the membranes in MeOH/MTBE mixtures was less than 7%. ► The membranes have excellent solvent resistance and moderate mechanical strength. ► The product purity stayed higher than 98.5 wt.% with increasing feed MeOH content.
Co-reporter:Pei Yu Xu;Tian Yi Guo;Chun Hui Zhao;Ian Broadwell;Qiu Gen Zhang
Journal of Applied Polymer Science 2013 Volume 128( Issue 6) pp:3853-3860
Publication Date(Web):
DOI:10.1002/app.38592
Abstract
The semi-interpenetrating polymer network technique was applied in the preparation of anion exchange membranes for direct methanol fuel cells (DMFCs). Poly(vinyl alcohol) was chosen as the polymer matrix and quaternized polyethyleneimine was used as the cationic polyelectrolyte. To modify the polymer membranes for achieving desirable properties, 1,2-bis(triethoxysilyl) ethane was used as a precursor to fabricate a set of organic–inorganic hybrid membranes. The hybrid membranes were characterized using X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The ionic conductivity, methanol permeability and stability under oxidative and alkaline conditions were measured to evaluate the applicability in DMFCs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Pei Yu Xu;Chun Hui Zhao
Journal of Applied Polymer Science 2013 Volume 130( Issue 2) pp:1172-1178
Publication Date(Web):
DOI:10.1002/app.39294
ABSTRACT
PVA/Cu (II) complex anion exchange membranes (AEMs) were prepared for direct methanol fuel cells. The complex was for the first time used as membrane material of AEMs. Glutaraldehyde as a crosslinking agent was introduced to control water uptake and swelling of the membranes. The membranes with thickness of 1 μm were fabricated using chemical fibers based on the solution surface tension. The complex membranes show good ionic conductivity and low methanol permeability in the magnitude of 10−2 S · cm−1 and 10−7 cm−2 · S−1, respectively. This is a facile, efficient, green, and fast way to prepare new AEMs for direct methanol fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1172-1178, 2013
Co-reporter:Yan Xia;Guang Lu Han;Qiu Gen Zhang;Yi Gong;Ian Broadwell
Journal of Applied Polymer Science 2013 Volume 130( Issue 5) pp:3718-3725
Publication Date(Web):
DOI:10.1002/app.39647
ABSTRACT
CuO-filled aminomethylated polysulfone hybrid membranes were prepared for sulfur removal from gasoline. The as-prepared membranes were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The separation performance of the hybrid membranes was evaluated by pervaporation (PV) separation of n-heptane/thiophene binary mixture. CuO-filling leads to a decrease in permeation flux. The sulfur-enrichment factor increased first and then decreased with increasing CuO loading, and it is worth noting that there is a rebound in enrichment factor above 8 wt % CuO loading. Influencing factors such as nitrogen content, feed temperature, sulfur content, and various hydrocarbons on membrane PV performance were also evaluated. Permeation flux of 23.9 kg·μm·m−2·h−1 and sulfur-enrichment factor of 3.9 can be achieved at 4 wt % CuO loading in PV of n-heptane/thiophene binary mixture with 1500 μg·g−1 sulfur content. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3718–3725, 2013
Co-reporter:Yi Gong;Ai Mei Zhu ;Qiu Gen Zhang
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 12) pp:2702-2708
Publication Date(Web):
DOI:10.1002/pola.26665
ABSTRACT
One-pot synthesis of thermoresponsive magnetic composite microspheres with a poly(N-isopropylacrylamide) (PNIPAM) shell and a Fe3O4 core is demonstrated. Temperature sensitivity of PNIPAM was adopted to design the novel synthesis pathway. The as-prepared composite microspheres have an obvious core-shell structure with a mean size of approximately 250 nm. The Fe3O4 core is approximately 5 nm and the thickness of the PNIPAM shell is approximately 10 nm. The content of Fe3O4 in the composite microspheres can be controlled by this method. The composite microspheres experience a swelling and shrinking process in water by adjusting the temperature below and above the lower critical solution temperature (LCST) around 32 °C. These microspheres also show fine response to an external magnetic field. This work presents a platform to synthesize organic/inorganic composite microspheres in a facile and efficient approach. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2702–2708
Co-reporter:Guang Lu Han, Qiu Gen Zhang, Qing Lin Liu
Journal of Membrane Science 2013 430() pp: 180-187
Publication Date(Web):
DOI:10.1016/j.memsci.2012.12.020
Co-reporter:Guang Lu Han, Yi Gong, Qiu Gen Zhang, Ai Mei Zhu, Mei Ling Ye, Qing Lin Liu
Journal of Membrane Science 2013 447() pp: 246-252
Publication Date(Web):
DOI:10.1016/j.memsci.2013.07.038
Co-reporter:Guang Lu Han, Yi Gong, Qiu Gen Zhang, Qing Lin Liu
Journal of Membrane Science 2013 448() pp: 55-61
Publication Date(Web):
DOI:10.1016/j.memsci.2013.07.060
Co-reporter:Ke Zhou, Qiu Gen Zhang, Guang Lu Han, Ai Mei Zhu, Qing Lin Liu
Journal of Membrane Science 2013 448() pp: 93-101
Publication Date(Web):
DOI:10.1016/j.memsci.2013.08.005
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Shu Ping Huang, Wei Wen Hu and Ai Mei Zhu
Journal of Materials Chemistry A 2012 vol. 22(Issue 21) pp:10860-10866
Publication Date(Web):30 Mar 2012
DOI:10.1039/C2JM30653K
Molecular dynamics (MD) simulations were used to reveal the relationship between the microstructure and performance of PVA–silica hybrid membranes from the hybridization of silanols, R–Si(OH)3. We first studied the PVA membranes hybridized by silanols with the linear alkyl group of –CnH2n+1 to investigate the effect of their size on the microstructure and properties of the hybrid membranes, then studied hybridization of H2N(CH2)3–Si(OH)3 (APTS) from the hydrolysis of APTEOS. Silica hybridization reduced the mobility of PVA chains remarkably, raised the amorphous region in the PVA matrix, and adjusted the membrane microstructure. Group R in the silanol R–Si(OH)3 has a prodigious effect on the microstructure and performances of the hybrid membranes. Small free volume cavities decreased, and the interchain spacing of PVA chains and big cavities increased with increasing size of group R. Furthermore, MD simulations revealed a relationship between the microstructure and performances of the PVA/APTS hybrid membranes. The results could provide guidance for designing novel functional silica-based hybrid membranes.
Co-reporter:Yi Gong, Qing Lin Liu, Ai Mei Zhu, Qiu Gen Zhang
Carbohydrate Polymers 2012 Volume 90(Issue 1) pp:690-695
Publication Date(Web):1 September 2012
DOI:10.1016/j.carbpol.2012.05.098
This work presents a new approach for the synthesis of multiresponsive composite microspheres of PNIPAM/chitosan. The resulting microspheres in a sandwich structure with PNIPAM nanoparticles embedded in the crosslinked chitosan matrix were characterized. Compared to other preparation methods, this proposed technique not only is a facile route but also endows the microspheres a desirable structure. The products undergo a temperature induced volume phase transition and exhibit an appreciable pH response. They are further tested as drug carriers to investigate potential application. The encapsulation efficiency in acidic environment (pH = 4.0) is 73.5% and much higher than that in neutral (20.3%, pH = 6.9) and alkaline (15.1%, pH = 9.2) environments. The release of the drug from the microspheres can be controlled by pH and temperature.Highlights► One-pot synthesis of multiresponsive composite microspheres is reported. ► CLSM and TEM results show that the products have a sandwich structure. ► Drug release from the microspheres can be controlled by pH and temperature.
Co-reporter:Chun Hui Zhao, Yi Gong, Qing Lin Liu, Qiu Gen Zhang, Ai Mei Zhu
International Journal of Hydrogen Energy 2012 Volume 37(Issue 15) pp:11383-11393
Publication Date(Web):August 2012
DOI:10.1016/j.ijhydene.2012.04.163
A series of novel anion exchange membranes based on poly(arylene ether sulfone) were fabricated. And the synthesized 1, 1, 2, 3, 3-pentamethylguanidine was used as a hydrophilic group. Bromination reaction rather than chloromethylation was used for the preparation of target conductive polymers. Fourier transform infrared spectroscopy (FTIR), 1H NMR and mass spectrometry (MS) were used to characterize the as-synthesized polymers. The ratio of hydrophilic to hydrophobic monomers was varied to study the structure-property of the membranes. The performance of the membrane with both hydrophilic/hydrophobic segments was improved over the membrane with sole hydrophilic segments. The self-crosslinking structure of the as-prepared membranes is partly responsible for their very low methanol permeability with the minimum of 1.02 × 10−9 cm−2⋅S−1 at 30 °C and insolubility in organic solvents considered. The structural dependence of water uptake is in the range of 25–87%. The as-prepared membranes did not suffer from serious membrane swelling. The ionic exchange capacity (IEC) reached a maximum of 1.21 mmol⋅g−1. The ionic conductivity of the membrane in deionized water is 6.00 and 13.00 × 10−2 S⋅cm−1 at 30 and 80 °C respectively.Highlights► Anion exchange membranes containing pentamethylguanidine were fabricated. ► The hydrophilic/hydrophobic structure-property of the membranes was studied. ► The self-crosslinking structure is partly responsible for low methanol permeability. ► The membranes exhibit good ionic conductivity with excellent chemical stability.
Co-reporter:Wen Wei Hu;Xiu Hua Zhang;Qiu Gen Zhang;Ai Mei Zhu
Journal of Applied Polymer Science 2012 Volume 126( Issue 2) pp:778-787
Publication Date(Web):
DOI:10.1002/app.36962
Abstract
The novel organic–inorganic hybrid membranes were prepared from poly(vinyl alcohol) (PVA) and vinyltriethoxysilane (VTES). They were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and contact angle metering. The as-prepared membranes are formed at a molecular scale at a low VTES content. Aggregations in the surface of the as-prepared membranes were clearly evident above 18.43 wt % VTES loading. The introduction of VTES into the PVA matrix resulted in a decrease in the crystalline and an increase in compactness and thermal stability of the as-prepared membranes. Silica hybridization reduced the swelling of the as-prepared membranes in water/ethanol/ethyl acetate mixtures, decreased the permeation flux, and remarkably enhanced water permselectivity in pervaporation dehydration of ethanol/ethyl acetate aqueous solution. The hybrid membrane with 24.04 wt % VTES has the highest separation factor of 1079 and permeation flux of 540 g m−2 h−1. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Qiu Gen Zhang, Bing Cheng Fan, Qing Lin Liu, Ai Mei Zhu, Feng Feng Shi
Journal of Membrane Science 2011 Volume 366(1–2) pp:335-341
Publication Date(Web):1 January 2011
DOI:10.1016/j.memsci.2010.10.022
Pervaporation performance of novel poly(dimethyl siloxane) (PDMS)/poly(oligosilsesquioxanes) (POSS) composites was analyzed by measuring solubility and diffusion behavior of a series of solvents in the composites using inverse gas chromatography (IGC) fitted with a packed column. The solubility and diffusion coefficients of thiophene, benzene and toluene at infinite dilution in the composites are greater than the other four solvents (cyclohexane, n-pentane, n-hexane and n-heptane). The PDMS/POSS composite membranes were thus prepared and characterized using scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. The pervaporation separation performance of the composite membranes was evaluated and agreed with the IGC study. The composite membranes are found to have a great promising application in pervaporation separation of thiophene from n-heptane.Research highlights▶ Novel poly(dimethyl siloxane) (PDMS)/poly(oligosilsesquioxanes) membranes are prepared and evaluated. ▶ Sorption and diffusion behavior of thiophene, benzene, toluene, cyclohexane, n-pentane, n-hexane and n-heptane in the membranes are investigated by IGC. ▶ The additive of poly(oligosilsesquioxanes) into PDMS enhances the solubility coefficient and diffusion coefficient of thiophene, benzene and toluene in the PDMS. ▶ The as-prepared membranes exhibit the best pervaporation performance in separation of thiophene/n-heptane, benzene/n-heptane and toluene/n-heptane.
Co-reporter:Su Qing Wang, Qing Lin Liu, Ai Mei Zhu
European Polymer Journal 2011 Volume 47(Issue 5) pp:1168-1175
Publication Date(Web):May 2011
DOI:10.1016/j.eurpolymj.2011.01.011
Composites of poly (N-isopropylacrylamide-co-acrylic acid)/titanium dioxide (TiO2) have been prepared via UV-initiated free radical polymerization. Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), environmental scanning electron microscope (ESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are used to study the composition, structure, and morphology of the as-prepared composites. TiO2 is found to be successfully encapsulated in the copolymer in spherical shapes with size of 2.5 μm. The thermo- and pH-responsive properties of the composites are observed using dynamic light scattering (DLS). The photocatalytic property of the composites is studied using UV–vis spectrophotometer on the degradation of methyl orange (MO) solution under various pHs and temperatures. Degradation ratio is higher at low pH and increases with increasing temperature above volume phase transition temperature (VPTT).
Co-reporter:Yu Chen;Shu Ping Huang;Ian Broadwell ;Ai Mei Zhu
Journal of Applied Polymer Science 2011 Volume 120( Issue 3) pp:1859-1865
Publication Date(Web):
DOI:10.1002/app.33411
Abstract
Molecular simulations have been used to study the sorption and diffusion properties of carbon dioxide in a series of poly (amide-imide) (PAI) membranes containing oligo(tetrafluoroethene) segment with various numbers (n = 0, 1, 2, 3, and 4) of tetrafluoroethene units. The solubility and self-diffusion coefficients were computed by the Grand Canonical Monte Carlo (GCMC) method and molecular dynamics (MD) simulations respectively. It was found that increasing the fluorine content of the polymer membrane reduced the associated glass transition temperature (Tg) and led to an increase in diffusion coefficient of carbon dioxide. Results indicate that penetrant molecule's diffusion coefficient is strongly dependent on chain mobility. It is also noticed that the radial distribution functions (RDFs) are inconsistent with the d-spacings of PAIs calculated form X-ray data. This is also thought to be tied to the number of degrees of freedom of the chain. Finally, this study gives a useful insight into how PAIs with high fluorine content can be tailored with a high permeability to carbon dioxide. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Ai Mei Zhu;Jian Hua Chen;Yu Liang Jiang
Journal of Applied Polymer Science 2011 Volume 120( Issue 4) pp:2374-2380
Publication Date(Web):
DOI:10.1002/app.33433
Abstract
Berberine hydrochloride is a natural medicine with wide clinical application. In this article, berberine hydrochloride was entrapped into alginate microspheres via an emulsification/gelation method. The size distribution of the microspheres was determined by a laser particle sizer. Drug distribution within the microspheres was determined by confocal laser scanning microscopy. Those drug-loaded microspheres were further entrapped into carboxymethyl chitosan (CMC) hydrogel to form a new drug-delivery system (DDS). The surface morphology of the DDS was observed using metallographic microscopy and scanning electron microscopy (SEM). The compression strength of the DDSs with alginate microspheres was found significantly higher than that of the pure hydrogel. The drug-release performances of the DDS in phosphate buffer solution (PBS, pH 7.4), saline solution (pH 6.3), and hydrochloric acid solution (HAS, pH 1.2) were also studied. Decay of the DDS in PBS within 72–80 h results in a faster release; however, the steady release in saline solution could last for all the testing period without cleavage of the DDS. In HAS, because of the shrinkage of the DDS, release is fast in the first period and remains steady later. The DDS exhibits prospective in controlled steady release of drugs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Tian Yi Guo, Qing Hua Zeng, Chun Hui Zhao, Qing Lin Liu, Ai Mei Zhu, Ian Broadwell
Journal of Membrane Science 2011 371(1–2) pp: 268-275
Publication Date(Web):
DOI:10.1016/j.memsci.2011.01.043
Co-reporter:Yu Chen, Qing Lin Liu, Ai Mei Zhu, Qiu Gen Zhang, Jian Yang Wu
Journal of Membrane Science 2010 Volume 348(1–2) pp:204-212
Publication Date(Web):15 February 2010
DOI:10.1016/j.memsci.2009.11.002
Molecular simulation techniques have been adopted for the first time for understanding the structure–property relationships of three highly fluorinated polyamide–imide (PAI) isomers (6FDA/8p, 6FDA/8m and 6FDA/12p). The PAIs being considered in this work are based on 2,2-bis(3,4-decarboxy-phenyl) hexafluoropropane dianhydride (6FDA) and N,N-bis(amino-phenyl)-perfluoroalkane-α,ω-dicarboxamide diamines. The density, fractional free volume (FFV) and glass transition temperature (Tg) of the PAIs are calculated to investigate the microstructure of the PAIs and the structural dependence of sorption and diffusion properties of CO2/CH4 pair. The 6FDA/8p and 6FDA/12p give both higher permeability and permselectivity than the 6FDA/8m because the rigid para-isomer functions as a molecular sieve. With a longer length of oligo(tetrafluoroethene) segment, the 6FDA/12p has permeability and selectivity greater than 6FDA/8p. Hence, this study may provide a guideline for designing PAI membranes to have desirable properties of permeability and permselectivity.
Co-reporter:Qing Hua Zeng, Qing Lin Liu, Ian Broadwell, Ai Mei Zhu, Ying Xiong, Xing Peng Tu
Journal of Membrane Science 2010 Volume 349(1–2) pp:237-243
Publication Date(Web):1 March 2010
DOI:10.1016/j.memsci.2009.11.051
A novel anion exchange membrane has been prepared using polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) as a starting material. Chloromethyl groups are first introduced into the SEBS and then converted into the quaternary ammonium groups. The membrane is characterized by Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). Water uptake, oxidative resistance, ionic conductivity and methanol permeability are measured to evaluate its performance in a direct methanol alkaline fuel cell. The ionic conductivity and permeability of the membrane to methanol was found to increase with temperature. The membrane exhibits an ionic conductivity of 9.37 × 10−3 S cm−1 in deionized water at 80 °C. For aqueous methanol solutions between 2 and 10 M at 30 °C, the methanol permeability was observed to range 2.34–4.45 × 10−7 cm2 s−1. Our novel SEBS membrane also shows high oxidative resistance to Fenton's reagent and good thermal stability under an air atmosphere.
Co-reporter:Qiu Gen Zhang;Xiao Juan Meng ;Ian Broadwell
Journal of Applied Polymer Science 2010 Volume 118( Issue 2) pp:1121-1126
Publication Date(Web):
DOI:10.1002/app.32504
Abstract
Novel hybrid organic–inorganic membranes were prepared via sol–gel reactions of quaternized poly(vinyl alcohol) (q-PVA) and γ-aminopropyltriethoxysilane (APTEOS) for pervaporation dehydration of an 85 wt % ethanol solution. The physicochemical structure of the hybrid membranes was characterized by FTIR, XRD, SEM, TG, and TEM. Nanofractal objects originated from self-assembly of ammonium groups on the q-PVA chains and amino groups in APTEOS can be observed on the surface of the hybrid membranes. When APTEOS/PVA ratio is 5% (wt/wt), the hybrid membrane has specific nervate networks on its surface and exhibits the highest separation factor. The hybrid membranes have better pervaporation performance than pristine q-PVA membrane, and their permeation flux was found to increase linearly with increasing APTEOS content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Xiao Juan Meng, Qing Lin Liu, Ai Mei Zhu, Qiu Gen Zhang
Journal of Membrane Science 2010 360(1–2) pp: 276-283
Publication Date(Web):
DOI:10.1016/j.memsci.2010.05.024
Co-reporter:Xiu Hua Zhang, Qing Lin Liu, Ying Xiong, Ai Mei Zhu, Yu Chen, Qiu Gen Zhang
Journal of Membrane Science 2009 Volume 327(1–2) pp:274-280
Publication Date(Web):5 February 2009
DOI:10.1016/j.memsci.2008.11.034
In this paper, chitosan (CS)/poly (vinyl pyrrolidone) (PVP) blend membranes crosslinked by glutaraldehyde (GA) were prepared for the separation of ethyl acetate/ethanol/water azeotrope by pervaporation (PV). Their chemical and physical characteristics were studied by Fourier transform infrared (FTIR), environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and contact angle measurement. The PV properties of the membranes were investigated through dehydration of the azeotrope. Permeation flux increased with increasing feed temperature and PVP content, while separation factor decreased. However, the separation factor increased with increasing GA content, whereas the flux decreased. The results showed that the membranes with PVP content of 10 wt% exhibited excellent PV properties with a flux of 953 g m−2 h−1 and separation factor of 746 at 35 °C.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Ai Mei Zhu, Ying Xiong, Lang Ren
Journal of Membrane Science 2009 Volume 335(1–2) pp:68-75
Publication Date(Web):15 June 2009
DOI:10.1016/j.memsci.2009.02.039
Quaternized poly(vinyl alcohol) (q-PVA) was synthesized, and crosslinked by glutaraldehyde to reduce the swelling of the q-PVA in an aqueous solution. The structure of the q-PVA and its crosslinked membranes was characterized by scanning electron microscopy, X-ray powder diffraction, and water contact angle measurements. Pervaporation performance of the membranes was studied by the dehydration of 85 wt% ethanol solution at 50 °C. The introduction of quaternary ammonium groups enhanced the hydrophilicity and water permselectivity. The water permeability and permselectivity of the q-PVA membranes increased simultaneously with increasing degree of quaternization (DQ). The crosslinking caused a decrease in swelling and an increase in water permselectivity of the q-PVA membranes. The q-PVA membrane with DQ of 4.035% has a highest water permeability of 12.628 g μm m−2 h−1 kPa−1, and the crosslinked q-PVA membrane with degree of crosslinking of 3.92% has a highest water permselectivity of 75.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Jian Yang Wu, Yu Chen, Ai Mei Zhu
Journal of Membrane Science 2009 Volume 342(1–2) pp:105-112
Publication Date(Web):15 October 2009
DOI:10.1016/j.memsci.2009.06.030
Poly(methyl methacrylate) (PMMA) composites containing polyhedral oligomeric silsesquioxanes substituted with isobutyl (iBuPOSS) are studied by molecular dynamics simulation. Properties of the composites, mixing thermodynamics and diffusion behaviors of O2 and N2 were investigated. Introduction of abundant iBuPOSS remarkably enhances the mobility of PMMA chain, whose self-diffusion coefficient in the composites with 51.14 wt% iBuPOSS is five times greater than that in pristine PMMA. Below 15 wt% loading iBuPOSS molecules homogeneously disperse in the PMMA matrix, whereas above 20 wt% loading iBuPOSS molecules aggregate into crystallites, and iBuPOSS molecules have restricted motion in the composites. Cohesive energy density and solubility parameter increase with increasing the iBuPOSS loading. Through-pores that are the channels for gas diffusion are observed in the composites with higher iBuPOSS loading. The incorporation of iBuPOSS leads to an increase in the diffusivities of O2 and N2 in the composites at low iBuPOSS loading (≤15 wt%), and the composites with 15 wt% iBuPOSS have the highest diffusion coefficient of O2 and N2.
Co-reporter:Ying Xiong, Qing Lin Liu, Ai Mei Zhu, Si Meng Huang, Qing Hua Zeng
Journal of Power Sources 2009 Volume 186(Issue 2) pp:328-333
Publication Date(Web):15 January 2009
DOI:10.1016/j.jpowsour.2008.10.070
A series of organic–inorganic membranes were prepared through sol–gel reaction of quaternized poly(vinyl alcohol) (QAPVA) with different contents of tetraethoxysilanes (TEOS) for alkaline direct methanol fuel cells. These hybrid membranes are characterized by FTIR, X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDXA) and thermo gravimetric analysis (TGA). The ion exchange content (IEC), water content, methanol permeability and conductivity of the hybrid membranes were measured to evaluate their applicability in fuel cells. It was found that the addition of silica enhanced the thermal stability and reduced the methanol permeability of the hybrid membranes. The hybrid membrane M-5, for which the silica content was 5 wt%, showed the lowest methanol permeability and the highest ion conductivity among the three hybrid membranes. The ratio of conductivity to methanol permeability of the membrane M-5 indicated that it had a high potential for alkaline direct methanol fuel cell applications.
Co-reporter:Ying Xiong, Qing Lin Liu, Qing Hua Zeng
Journal of Power Sources 2009 Volume 193(Issue 2) pp:541-546
Publication Date(Web):5 September 2009
DOI:10.1016/j.jpowsour.2009.04.043
Quaternized cardo polyetherketone (QPEK-C) membranes for alkaline fuel cells were prepared via chloromethylation, quaternization and alkalization of cardo polyetherketone (PEK-C). The chemical reaction for PEK-C modification was confirmed by nuclear magnetic resonance (1H NMR) and energy-dispersive X-ray spectroscopy (EDAX). The QPEK-C membrane was characterized by X-ray photoelectron spectroscopy (XPS) and thermo gravimetric analysis (TG). The ion-exchange content (IEC), water and methanol uptakes, methanol permeability and conductivity of the QPEK-C membranes were measured to evaluate their applicability in alkaline methanol fuel cells. The ionic conductivity of the QPEK-C membrane varied from (1.6 to 5.1) × 10−3 S cm−2 over the temperature range 20–60 °C. The QPEK-C membrane showed excellent methanol resistance. When the concentration of methanol was 4 M, the methanol permeability was less than 10−9 cm2 s−1 at 30 °C.
Co-reporter:Jian Yang Wu, Qing Lin Liu, Ying Xiong, Ai Mei Zhu and Yu Chen
The Journal of Physical Chemistry B 2009 Volume 113(Issue 13) pp:4267-4274
Publication Date(Web):March 3, 2009
DOI:10.1021/jp805923k
The COMPASS (condensed-phase optimized molecular potentials for atomistic simulation studies) force field with two sets of partial atomic charges of water was used to simulate adsorption and diffusion behavior of water/methanol and water/ethanol mixtures in zeolite 4A at 298 K. The adsorption of alcohol first increased and then decreased with increasing pressure, whereas the adsorption of water increased progressively until an adsorption equilibrium was reached. Both the adsorbed molecules and the zeolite framework were treated as a fully flexible model in MD simulations. The simulation results show that the effects of the size and steric hindrance of the diffusing molecules on diffusivity are significant. The diffusivity of water, methanol, and ethanol molecules decreases by 1 order of magnitude in the order of water > methanol > ethanol. The diffusivity of water molecules depends on the mass fraction and the partial charges of water in zeolite 4A. The ethanol and methanol molecules have restricted motion through the α-cages, whereas the water molecules can easily pass through the α-cages window at low feed alcohol concentrations. And the extent of hydrogen bonding increased with increasing water concentration.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Feng Feng Shi and Ying Xiong
Journal of Materials Chemistry A 2008 vol. 18(Issue 39) pp:4646-4653
Publication Date(Web):26 Aug 2008
DOI:10.1039/B806303F
Organic–inorganic hybrid membranes with high separation performance were prepared by the incorporation of polysilisesquioxane (PSS) into a poly(vinyl alcohol) (PVA) matrix in order to solve the trade-off relationship between the selectivity and permeability of PVA membranes. The incorporation of the PSS resulted in a change in the physical and chemical structure of the hybrid membranes. The crystalline region in the hybrid membranes decreased with increasing PSS content. The hydrophilicity of the hybrid membranes increased when the PSS content is below 3 wt%, and then decreased. Silica particles formed on the surface and in the interior of the hybrid membranes due to the PSS conglomeration, and the surface roughness of the hybrid membranes increased linearly with increasing PSS content. The trade-off between permeability and selectivity was successfully solved using the hybrid membranes in pervaporation dehydration of tetrahydrofuran. The permselectivity and flux of the hybrid membranes increased simultaneously when the PSS content was below 2 wt%, whereas the permselectivity decreased when the PSS content was above 2 wt%. The hybrid membrane containing 2 wt% PSS had the highest separation factor of 1810.
Co-reporter:Jian Hua Chen, Qing Lin Liu, Ying Xiong, Qiu Gen Zhang, Ai Mei Zhu
Journal of Membrane Science 2008 Volume 325(Issue 1) pp:184-191
Publication Date(Web):15 November 2008
DOI:10.1016/j.memsci.2008.07.027
Cardo polyetherketone (PEK-C) composite membranes were prepared by casting glutaraldehyde (GA) cross-linked sulfonated cardo polyetherketone (SPEK-C) or silicotungstic acid (STA) filled SPEK-C and poly(vinyl alcohol) (PVA) blending onto a PEK-C substrate. The compatibility between the active layer and PEK-C substrate is improved by immersing the PEK-C substrate in a GA cross-linked sodium alginate (NaAlg) solution and using water–dimethyl sulfoxide (DMSO) as a co-solvent for preparing the STA-PVA-SPEK-C/GA active layer. The pervaporation (PV) dehydration of acetic acid shows that permeation flux decreased and separation factor increased with increasing GA content in the homogeneous membranes. The permeation flux achieved a minimum and the separation factor a maximum when the GA content increased to a certain amount. Thereafter the permeation flux increased and the separation factor decreased with further increasing the GA content. The PV performance of the composite membranes is superior to that of the homogeneous membranes when the feed water content is below 25 wt%. The permeation activation energy of the composite membranes is lower than that of the homogeneous membranes in the PV dehydration of 10 wt% water in acetic acid. The STA-PVA-SPEK-C-GA/PEK-C composite membrane using water–DMSO as co-solvent has an excellent separation performance with a flux of 592 g m−2 h−1 and a separation factor of 91.2 at a feed water content of 10 wt% at 50 °C.
Co-reporter:Jin Zhi Yang, Yu Chen, Ai Mei Zhu, Qing Lin Liu, Jian Yang Wu
Journal of Membrane Science 2008 Volume 318(1–2) pp:327-333
Publication Date(Web):20 June 2008
DOI:10.1016/j.memsci.2008.02.059
The diffusion of methanol/water mixture through MFI-type zeolite (HZSM-5 and silicalite-1 in this work) membranes has been studied by NVT-ensemble equilibrium molecular dynamics (MD) techniques. We studied the influence of concentration and temperature on the diffusion behaviors of methanol and water after replacing aluminium atoms with silicon atoms in MFI-type zeolite. The diffusion coefficient of water first increased and then decreased with increasing water content. However, the diffusion coefficient of methanol decreased with increasing methanol content. The effect of concentration and temperature on the diffusion behavior of species in both single component and mixtures was also investigated by analysis of radial distribution function (RDF) and mean square displacement (MSD). The distribution of water in silicalite is almost the same as that in HZSM-5. There is an inter-water hydrogen bond formed when R(OH) is 1.75 Å. But the hydrogen peak in low-water concentration range in HZSM-5 is higher than in silicalite. There is an estimated maximum self-diffusion of water in HZSM-5, which agrees with the literature experimental observation.
Co-reporter:Ying Xiong, Jun Fang, Qing Hua Zeng, Qing Lin Liu
Journal of Membrane Science 2008 Volume 311(1–2) pp:319-325
Publication Date(Web):20 March 2008
DOI:10.1016/j.memsci.2007.12.029
A series of novel cross-linked quaternized poly(vinyl alcohol) (PVA) membranes have been prepared and characterized for alkaline direct methanol fuel cell (DMFC) applications. It was found that quaternary ammonium groups were grafted onto the backbone of the PVA chain with low substitution. The ionic conductivity of these new anion exchange membranes can be as high as 7.34 × 10−3 S/cm in deionized water at 30 °C, which is higher than that of other anion exchange membranes. The methanol permeability of the membrane is found to be reduced relative to Nafion® 117 membranes, and the methanol permeability decreases with increasing methanol concentration. These new quaternized poly(vinyl alcohol) membranes may be used in alkaline direct methanol fuel cells for easy preparation and lower cost.
Co-reporter:Ying Xiong, Qing Lin Liu, Qiu Gen Zhang, Ai Mei Zhu
Journal of Power Sources 2008 Volume 183(Issue 2) pp:447-453
Publication Date(Web):1 September 2008
DOI:10.1016/j.jpowsour.2008.06.004
Novel cross-linked composite membranes were synthesized to investigate their applicability in anion exchange membrane fuel cells. These membranes consist of quaternized poly(vinyl alcohol) (QAPVA) and quaternized chitosan (2-hydroxypropyltrimethyl ammonium chloride chitosan, HACC) with glutaraldehyde as the cross-linking reagent. The membranes were characterized in term of their water content, ion exchange capacity (IEC), ion conductivity and methanol permeability. FTIR, X-ray diffraction and scanning electron microscopy (SEM) were also used to investigate the relation between the structure and performance of the composite membranes. The composite membranes have a high conductivity (10−3 to 10−2 S cm−1), and a low methanol permeability (from 5.68 × 10−7 to 4.42 × 10−6 cm2 s−1) at 30 °C. After reviewing all pertinent characteristics of the membranes, we find that the membrane structure is the principal factor affecting the conductivity and methanol permeability of these membranes.
Co-reporter:Jian Hua Chen, Qing Lin Liu, Ai Mei Zhu, Jun Fang, Qiu Gen Zhang
Journal of Membrane Science 2008 Volume 308(1–2) pp:171-179
Publication Date(Web):1 February 2008
DOI:10.1016/j.memsci.2007.09.058
Homogeneous membranes based on sulfonated cardo polyetherketone (SPEK-C) were prepared. The membranes were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), field emission high resolution transmission electron microscope (HRTEM) and contact angle meter. The results show that both the hydrophilicity and the amorphous region of the membranes increased with sulfonation degree (SD) increasing. The membranes show excellent thermal stability. Sulfonic acid groups exist as a form of ion clusters and distribute in the membranes homogeneously, which form the channel for permeants to pass through. The effects of solvent and SD on the performance of the membranes were studied. The results show that the SPEK-C membrane has excellent performance when the SD is 0.75 and dimethylsulfoxide is used as a solvent. Separation factor decreases and permeation flux increases with the feed temperature and water concentration increasing. The membrane has good separation performance with a flux of 248 g m−2 h−1 and separation factor of 103 at 50 °C in pervaporation of 90 wt% acetic acid in water.
Co-reporter:Pei Li, Ai Mei Zhu, Qing Lin Liu and Qiu Gen Zhang
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 20) pp:7700
Publication Date(Web):September 20, 2008
DOI:10.1021/ie800824q
Multiresponsive composite microspheres were fabricated via emulsion polymerization in two steps. Fe3O4 nanoparticles modified by oleic acid (about 13 nm in diameter) were first prepared, and then they were embedded in biocompatible chitosan (CS) and N-isopropylacrylamide (NIPAm). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) examined the structure and morphology of the composite microspheres. Scanning electron microscopy (SEM) and transmission electronic microscopy (TEM) indicate the diameter of the composite microspheres to be about 400 nm. The magnetic, thermo, and pH-sensitive properties of the composite microspheres were investigated. Magnetic measurements with magnet and superconducting quantum interference device (SQUID) reveal that the composite microspheres are superparamagnetic. The electromagnetically induced heating shows that the composite microspheres could be heated up to 45 °C in an alternating electromagnetic field. The dynamic light scattering (DLS) results confirm the thermoresponsive and pH-responsive properties. It was found that the lower critical solution temperature (LCST) of the composite microspheres is 29 °C in water, and the LCST changed from 28 to 32 °C in the pH range from 4.7 to 7.4. These composite microspheres with the multiresponsive properties show great promise in biomedical applications.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Ai Mei Zhu, Ying Xiong and Xiu Hua Zhang
The Journal of Physical Chemistry B 2008 Volume 112(Issue 51) pp:16559-16565
Publication Date(Web):December 2, 2008
DOI:10.1021/jp807573g
Bis(trialkylsilyl) precursor was used to modify polymer membranes for the first time. Novel organic−inorganic hybrid membranes of poly(vinyl alcohol) (PVA)/1,2-bis(triethoxysilyl)ethane (BTEE) were prepared through a sol-gel method for pervaporation dehydration of ethanol. The permeability and selectivity of the membranes were improved simultaneously. The physicochemical properties of the hybrid membranes were investigated. With increasing BTEE content, the amorphous region in the hybrid membranes increased and became more compact. Phase separation took place in the hybrid membranes containing abundant BTEE, and silica particles distributed in the PVA matrix homogeneously. Compared to PVA membranes, the hybrid membranes exhibit high thermal stability and improved separation performances. Silica-hybrids reduced significantly the swelling of PVA membranes in an aqueous solution. The Flory−Huggins interaction parameter of water with membranes χ13 increased with increasing BTEE content, whereas that of ethanol with membranes χ23 decreased. Diffusion behavior of water and ethanol through the membranes were analyzed using the Maxwell−Stefan equation. When BTEE content was below 6 wt%, diffusion coefficient of water D13 increased remarkably and that of ethanol D23 decreased slightly.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Jie Lin, Jian Hua Chen and Ai Mei Zhu
Journal of Materials Chemistry A 2007 vol. 17(Issue 46) pp:4889-4895
Publication Date(Web):11 Oct 2007
DOI:10.1039/B709592A
Novel hybrid materials were prepared through sol–gel reaction of poly(vinyl alcohol) (PVA) and γ-aminopropyltriethoxysilane (APTEOS). Solubility and diffusion behavior of a series of solvents in the PVA/APTEOS hybrid materials were studied by inverse gas chromatography (IGC) fitted with a packed column. Solubility thermodynamics parameters at infinite dilution, such as the activity coefficient Ω∞1 and the solubility coefficient S of solvents in the hybrid materials, the partial molar excess free energy of mixture ΔGm, and the Flory–Huggins interaction parameter χ∞12 were determined. The infinite dilution diffusion coefficients D∞ of the solvents in the hybrid materials were also calculated. Effects of APTEOS content in the stationary phase and the column temperature on the solubility and diffusion of solvents in the hybrid materials were investigated. The hybrid material containing 5.0 wt% APTEOS has the strongest interaction with water, the largest S and D∞ for water, and the hybrid material has a promising application in membrane separation, such as pervaporation dehydration of alcohol solution. The solubility parameter δ2 of the hybrid materials was estimated, and it decreased with increasing APTEOS content. The dependence of D∞ on temperature was in good agreement with the Arrhenius equation.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Zhong Ying Jiang, Yu Chen
Journal of Membrane Science 2007 Volume 287(Issue 2) pp:237-245
Publication Date(Web):15 January 2007
DOI:10.1016/j.memsci.2006.10.041
Novel organic–inorganic hybrid membranes were prepared through sol–gel reaction of poly(vinyl alcohol) (PVA) with γ-aminopropyl-triethoxysilane (APTEOS) for pervaporation (PV) separation of ethanol/water mixtures. The membranes were characterized by FTIR, EDX, WXRD and PALS. The amorphous region of the hybrid membranes increased with increasing APTEOS content, and both the free volume and the hydrophilicity of the hybrid membranes increased when APTEOS content was less than 5 wt%. The swelling degree of the hybrid membranes has been restrained in an aqueous solution owing to the formation of hydrogen and covalent bonds in the membrane matrix. Permeation flux increased remarkably with APTEOS content increasing, and water permselectivity increased at the same time, the trade-off between the permeation flux and water permselectivity of the hybrid membranes was broken. The sorption selectivity increased with increasing temperature, and decreased with increasing water content. In addition, the diffusion selectivity and diffusion coefficient of the permeants through the hybrid membranes were investigated. The hybrid membrane containing 5 wt% APTEOS has highest separation factor of 536.7 at 50 °C and permeation flux of 0.0355 kg m−2 h−1 in PV separation of 5 wt% water in the feed.
Co-reporter:Li Yi Ye;Qiu Gen Zhang;Ai Mei Zhu;Guo Bo Zhou
Journal of Applied Polymer Science 2007 Volume 105(Issue 6) pp:3640-3648
Publication Date(Web):9 JUN 2007
DOI:10.1002/app.26446
Poly(vinyl alcohol) (PVA) blended with poly(ethylene glycol) (PEG) was crosslinked with tetraethoxysilane (TEOS) to prepare organic–inorganic PVA/PEG/TEOS hybrid membranes. The membranes were then used for the dehydration of ethanol by pervaporation (PV). The physicochemical structure of the hybrid membranes was studied with Fourier transform infrared spectra (FT-IR), wide-angle X-ray diffraction WXRD, and scanning electron microscopy (SEM). PVA and PEG were crosslinked with TEOS, and the crosslinking density increased with increases in the TEOS content, annealing temperature, and time. The water permselectivity of the hybrid membranes increased with increasing annealing temperature or time; however, the permeation fluxes decreased at the same time. SEM pictures showed that phase separation took place in the hybrid membranes when the TEOS content was greater than 15 wt %. The water permselectivity increased with the addition of TEOS and reached the maximum at 10 wt % TEOS. The water permselectivity decreased, whereas the permeation flux increased, with an increase in the feed water content or feed temperature. The hybrid membrane that was annealed at 130°C for 12 h exhibited high permselectivity with a separation factor of 300 and a permeation flux of 0.046 kg m−2 h−1 in PV of 15 wt % water in ethanol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Qing Lin Liu;Zhen Feng Cheng
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 18) pp:2541-2547
Publication Date(Web):29 JUL 2005
DOI:10.1002/polb.20533
A new simple activity coefficient model for the prediction of solvent activities in polymer solutions is presented. The model consists of three terms, the combinatorial and the residual terms, which are taken from UNIFAC model, and a free-volume term derived from the van der Waals partition function with the mixed volume, the mixed free-volume and the mixed c-value being supposed to be given by linear mixing rules. Twenty-one polymer solution systems were used to test the applicability of the present model. Compared with the UNIFAC-FV, Entropic-FV, and Entropic-FV-1.2 models, it is found that the model proposed in this work can produce better results than those from the other three models. Furthermore, the model is valid for a broad range of polymer concentration and a wide range of temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2541–2547, 2005
Co-reporter:Qing-Lin Liu, Hao-Qi Gao
Journal of Membrane Science 2003 Volume 214(Issue 1) pp:131-142
Publication Date(Web):15 March 2003
DOI:10.1016/S0376-7388(02)00542-2
Using a simple activity coefficient model in conjunction with the Vrentas–Duda free-volume (FV) theory, the diffusion behavior of small molecular solvents between and amongst polymer chains is then predicted for several polymer/solvent systems over a wide range of concentrations. The estimations are comparable with experimental data for some systems. For diffusion over- and under-predicted systems, a pre-exponential factor D0 can be adjusted to improve the predictions. It is found that the entropic-FV model is a suitable alternative to the Flory–Huggins equation for predicting mutual-diffusion coefficients in polymeric solutions. To understand the impact of the model on the prediction thoroughly a sensitivity analysis is done for free-volume. The influence of the free-volume of solvent is the opposite of that of the polymer.
Co-reporter:Qing Lin Liu, Hong Fang Chen
Journal of Membrane Science 2002 Volume 196(Issue 2) pp:171-178
Publication Date(Web):28 February 2002
DOI:10.1016/S0376-7388(01)00543-9
Modeling of esterification of acetic acid with n-butanol in the presence of Zr(SO4)2·4H2O coupled pervaporation was studied in this paper. The influence of several process variables, such as process temperature, initial mole ratio of acetic acid over n-butanol, the ratio of the effective membrane area over the volume of reacting mixture and catalyst content, on the esterification was discussed. The calculated results for the conversion of n-butanol to water and permeation flux were consistence with the experimental data. The permselectivity and water content can be roughly estimated by the model equations.
Co-reporter:Qinglin Liu, Zhibing Zhang, Hongfang Chen
Journal of Membrane Science 2001 Volume 182(1–2) pp:173-181
Publication Date(Web):15 February 2001
DOI:10.1016/S0376-7388(00)00568-8
The separation characteristics of the crosslinked polyvinyl alcohol (PVA) membranes prepared in our laboratory were studied by pervaporation separation of the liquid mixtures of both water/acetic acid and water/acetic acid/n-butanol/butyl acetate. The permeation fluxes of water and acetic acid as a function of compositions were presented. The esterification of acetic acid with n-butanol catalyzed by Zr(SO4)·4H2O was carried out at a temperature range of 60–90°C. A kinetic model equation was developed for the esterification; then, it was taken as a model reaction to study the coupling of pervaporation with esterification. Experiments were conducted to investigate the effects of several operating parameters, such as reaction temperature, initial molar ratio of acetic acid to n-butanol, ratio of the membrane area to the reacting mixture volume and catalyst concentration, on the coupling process.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Yu Chen, Jian Yang Wu, Ai Mei Zhu
Chemical Engineering Science (January 2009) Volume 64(Issue 2) pp:334-340
Publication Date(Web):1 January 2009
DOI:10.1016/j.ces.2008.10.028
Molecular dynamics (MD) simulation was used to study the swelling properties of poly(vinyl alcohol) (PVA) in ethanol solutions containing 15, 30 and 45 wt% water. The characteristics of the swollen PVA, intrinsic relation between the microstructure of the swollen PVA and the diffusion of water and ethanol in the PVA matrix were analyzed. It was found that the free volume of the swollen PVA reduced with reductions in the degree of crystallinity was accompanied by an increase in the mobility of PVA chains. Water located mostly in the hydrophilic region of the hydroxyl groups of PVA chains; and hydrogen bonding formed between water and PVA. It was also noted water clusters form in the swollen PVA, whose size increased with increasing degree of swelling, whereas ethanol molecules disperse almost individually in the PVA matrix. The diffusion coefficients of water and ethanol in the swollen PVA are predicted to increase linearly with increasing swelling.
Co-reporter:Faizal Soyekwo, Qiugen Zhang, Runsheng Gao, Yan Qu, Ruixue Lv, Mengmeng Chen, Aimei Zhu and Qinglin Liu
Journal of Materials Chemistry A 2017 - vol. 5(Issue 2) pp:NaN592-592
Publication Date(Web):2016/11/23
DOI:10.1039/C6TA07567C
The development of inorganic functionalized membranes with the capacity to effectively separate molecules or ions in solutions based on the size or electrostatic interactions is pivotal to purification and separation applications. Herein, we demonstrate a novel green strategy utilizing a completely aqueous process to construct an asymmetrically structured metal surface functionalized polymer–matrix nanocomposite nanofiltration membrane. Crosslinked polyethyleneimine (PEI) is grafted on a carboxylated carbon nanotube intermediate layer incorporated into the macroporous cellulose acetate substrate to form the composite membrane. The resulting membrane is subsequently inorganically modified via an in situ surface reaction of zinc nitrate with excess ammonium hydroxide to produce the hydrophilic and positively charged membrane. Crosslinking enhances the polymer interaction with the carbon nanotube interlayer which in turn endows it with mechanical strength and sustains the membrane pore structure during pressure driven filtration. The functionalized membrane displays outstanding pure water flux of 16.5 ± 1.3 L m−2 h−1 bar−1 while exhibiting good nanofiltration performance of bivalent cations, which is ascribed to the electrostatic repulsion via the Donnan exclusion effect. Meanwhile the membranes exhibit excellent separation of organic molecules and long-term filtration stability. This newly developed approach presents a promising route for the construction of highly permeable nanofiltration membranes for fast purification and separation applications.
Co-reporter:Chen Xiao Lin, Xiao Ling Huang, Dong Guo, Qiu Gen Zhang, Ai Mei Zhu, Mei Ling Ye and Qing Lin Liu
Journal of Materials Chemistry A 2016 - vol. 4(Issue 36) pp:NaN13948-13948
Publication Date(Web):2016/08/12
DOI:10.1039/C6TA05090E
To realize high performance anion exchange membranes (AEMs) for alkaline fuel cells (AFCs), a series of quaternized poly(ether sulfone)s (PESs) with different lengths of flexible spacers linking cationic groups and the backbone was synthesized via nucleophilic polycondensation, demethylation and Williamson reactions. Atomic force microscopy (AFM) phase images show clear hydrophilic/hydrophobic phase separation for all the side-chain-type AEMs. The PES-n-QA membrane with hexyleneoxy spacers (n = 6) between the cationic groups and backbone (benzene ring) exhibited the maximum conductivity of 62.7 mS cm−1 (IEC = 1.48 meq. g−1) at 80 °C. The AEM materials are found to have an improved long-term alkaline stability by extending the length of the flexible spacer (n ≥ 4). The PES-12-QA membrane with a flexible dodeceneoxy spacer demonstrated the highest alkaline stability, where the conductivity and IEC only decreased by 8.1% and 6.9% after immersing in a 1 M aqueous KOH solution at 60 °C for 720 h. Furthermore, the single fuel cell performance test using PES-6-QA as an AEM showed a maximum power density of 108.3 mW cm−2 at a current density of 250 mA cm−2 at 60 °C.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Shu Ping Huang, Wei Wen Hu and Ai Mei Zhu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 21) pp:NaN10866-10866
Publication Date(Web):2012/03/30
DOI:10.1039/C2JM30653K
Molecular dynamics (MD) simulations were used to reveal the relationship between the microstructure and performance of PVA–silica hybrid membranes from the hybridization of silanols, R–Si(OH)3. We first studied the PVA membranes hybridized by silanols with the linear alkyl group of –CnH2n+1 to investigate the effect of their size on the microstructure and properties of the hybrid membranes, then studied hybridization of H2N(CH2)3–Si(OH)3 (APTS) from the hydrolysis of APTEOS. Silica hybridization reduced the mobility of PVA chains remarkably, raised the amorphous region in the PVA matrix, and adjusted the membrane microstructure. Group R in the silanol R–Si(OH)3 has a prodigious effect on the microstructure and performances of the hybrid membranes. Small free volume cavities decreased, and the interchain spacing of PVA chains and big cavities increased with increasing size of group R. Furthermore, MD simulations revealed a relationship between the microstructure and performances of the PVA/APTS hybrid membranes. The results could provide guidance for designing novel functional silica-based hybrid membranes.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Jie Lin, Jian Hua Chen and Ai Mei Zhu
Journal of Materials Chemistry A 2007 - vol. 17(Issue 46) pp:NaN4895-4895
Publication Date(Web):2007/10/11
DOI:10.1039/B709592A
Novel hybrid materials were prepared through sol–gel reaction of poly(vinyl alcohol) (PVA) and γ-aminopropyltriethoxysilane (APTEOS). Solubility and diffusion behavior of a series of solvents in the PVA/APTEOS hybrid materials were studied by inverse gas chromatography (IGC) fitted with a packed column. Solubility thermodynamics parameters at infinite dilution, such as the activity coefficient Ω∞1 and the solubility coefficient S of solvents in the hybrid materials, the partial molar excess free energy of mixture ΔGm, and the Flory–Huggins interaction parameter χ∞12 were determined. The infinite dilution diffusion coefficients D∞ of the solvents in the hybrid materials were also calculated. Effects of APTEOS content in the stationary phase and the column temperature on the solubility and diffusion of solvents in the hybrid materials were investigated. The hybrid material containing 5.0 wt% APTEOS has the strongest interaction with water, the largest S and D∞ for water, and the hybrid material has a promising application in membrane separation, such as pervaporation dehydration of alcohol solution. The solubility parameter δ2 of the hybrid materials was estimated, and it decreased with increasing APTEOS content. The dependence of D∞ on temperature was in good agreement with the Arrhenius equation.
Co-reporter:Qiu Gen Zhang, Qing Lin Liu, Feng Feng Shi and Ying Xiong
Journal of Materials Chemistry A 2008 - vol. 18(Issue 39) pp:NaN4653-4653
Publication Date(Web):2008/08/26
DOI:10.1039/B806303F
Organic–inorganic hybrid membranes with high separation performance were prepared by the incorporation of polysilisesquioxane (PSS) into a poly(vinyl alcohol) (PVA) matrix in order to solve the trade-off relationship between the selectivity and permeability of PVA membranes. The incorporation of the PSS resulted in a change in the physical and chemical structure of the hybrid membranes. The crystalline region in the hybrid membranes decreased with increasing PSS content. The hydrophilicity of the hybrid membranes increased when the PSS content is below 3 wt%, and then decreased. Silica particles formed on the surface and in the interior of the hybrid membranes due to the PSS conglomeration, and the surface roughness of the hybrid membranes increased linearly with increasing PSS content. The trade-off between permeability and selectivity was successfully solved using the hybrid membranes in pervaporation dehydration of tetrahydrofuran. The permselectivity and flux of the hybrid membranes increased simultaneously when the PSS content was below 2 wt%, whereas the permselectivity decreased when the PSS content was above 2 wt%. The hybrid membrane containing 2 wt% PSS had the highest separation factor of 1810.
Co-reporter:Yi Zhi Zhuo, Ao Lan Lai, Qiu Gen Zhang, Ai Mei Zhu, Mei Ling Ye and Qing Lin Liu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 35) pp:NaN18114-18114
Publication Date(Web):2015/07/29
DOI:10.1039/C5TA04257G
Anion exchange membranes (AEMs) have been recognized as one of the most prospective polyelectrolytes for fuel cells due to their faster electrode reaction kinetics and the potential of adopting cheaper metal catalysts against proton exchange membranes (PEMs). Herein, a series of poly(arylene ether sulfone)s containing a flexible pendant imidazolium cation were synthesized by grafting bromine-bearing imidazolium-based ionic liquids into a hydroxyl-bearing poly(ether sulfone) matrix. 1H NMR spectroscopy was used to confirm the as-synthesized copolymers. Atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) were used to characterize the morphology of the membranes. The incorporation of the flexible side-chain imidazolium groups is beneficial to the aggregation of the ionic clusters leading to the formation of hydrophilic/hydrophobic phase-separated morphology and nano-channels. As a result, an enhancement in the ionic conductivity can be achieved. Therefore, the as-prepared AEMs possess higher ionic conductivity than traditional benzyl-type AEMs. The weight-based ion exchange capacity (IECw) of the membranes was in the range of 1.01–1.90 meq. g−1. Correspondingly, their ionic conductivity was in the range of 22.13–59.19 and 51.66–108.53 mS cm−1 at 30 and 80 °C, respectively. Moreover, the membranes also exhibit good alkaline stability and interesting single cell performance. This work presents a facile and universal route for the synthesis of AEMs with superior performance.
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