Co-reporter:Hongwei Fan, Ren Wang, Linglong Shan, Hao Yan, Jie Li, Shulan Ji, Haiqing LinGuojun Zhang
ACS Applied Materials & Interfaces February 1, 2017 Volume 9(Issue 4) pp:
Publication Date(Web):January 4, 2017
DOI:10.1021/acsami.6b16334
Polymeric membranes are important materials for efficient sieving of targeted components at the molecular level and have made significant advancement in many industrial applications such as biofuel production, water purification, fuel combustion, and carbon dioxide capture. Although their separation efficiencies have been widely investigated, lack of more efficient, greener, and lower-cost membrane fabrication mechanisms is still a major hurdle for mass production, because the conventional membrane-making process is always time-consuming, highly inefficient, and consumes a large amount of organic solvents. Herein we report a one-step assembly concept capable of directly processing low-viscosity oligomers into polymer-based molecular separation membranes in an ultrafast and green manner. This process was implemented by alternate atomizing–depositing of low-viscosity oligomers and reaction auxiliary agents onto a rotating support and followed by an ultrafast interfacial reaction under solvent-free conditions. Without the need for dissolution processing of polymer, solvent evaporation, and any post-treatments, the whole technological process could be accomplished within a few seconds/minutes, which is 2–3 orders of magnitude faster than conventional solution-coating technologies. The universality of this facile approach has also been demonstrated by successfully producing various defect-free polymeric membranes and homodispersed nanohybrid membranes with excellent and stable performance for bioalcohol production and recovery of different trace organics from dilute solutions.Keywords: bioalcohol; molecular separation membrane; oligomer; one-step assembly; pervaporation;
Co-reporter:Linglong Shan, Lili Gong, Hongwei Fan, Shulan Ji, Guojun Zhang
Journal of Membrane Science 2017 Volume 522() pp:183-191
Publication Date(Web):15 January 2017
DOI:10.1016/j.memsci.2016.09.023
•Spray-assisted biomineralization of a superhydrophilic water uptake layer.•The flux with biomineralizing CaCO3 is five times of a polyelectrolyte membrane.•A new uptake-solution-diffusion pervaporation mechanism was proposed.The membrane surface wettability is one of the most important factors influencing the solution-diffusion-controlled pervaporation process. In this work, a novel conceptual methodology for the construction of a superhydrophilic water uptake layer is proposed to overcome the limitation of trade-off effects. Rapid implementation of this strategy is possible by spray-assisted biomineralization of calcium carbonate (CaCO3) onto a (poly(acrylic acid)/poly(ethyleneimine))n/polyacrylonitrile ((PAA/PEI)n/PAN) membrane. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a hierarchical lotus CaCO3 layer with calcite crystals on the outermost layer. The water contact angle dramatically decreased from 74° to 4.2° after biomineralizing CaCO3 micro-nano-particles. In the pervaporation separation of ethanol/water mixtures, the water content could be enriched from 5 wt% to 98.8 wt% while the permeate flux reached 1317 g/(m2 h), which is almost five times that of a pure polyelectrolyte membrane without biomineralizing CaCO3. This suggests that the CaCO3 water uptake layer plays a very important role in achieving high flux. These results indicate that biomineralization of micro-nano-particles is a facile strategy to fabricate a superhydrophilic surface and, in turn, improve the membrane performance.Download high-res image (406KB)Download full-size image
Co-reporter:Hongxia Guo, Yiwen Ma, Zhenping Qin, Zhaoxiang Gu, Suping Cui, and Guojun Zhang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 35) pp:23379
Publication Date(Web):August 18, 2016
DOI:10.1021/acsami.6b07106
The hierarchical-structured superhydrophilic poly(ethylenimine)/poly(acrylic acid) (PEI/PAA)calcium silicate hydrate (CSH) multilayered membranes (PEI/PAA-CSH)n were prepared as aqueous nanofiltration (NF) membrane, and then they were transformed into superhydrophobic organic solvent nanofiltration (OSN) membranes by one-step modification of trimethylperfluorinatedsilane (PFTS). Investigation on surface structures and properties of these multilayered membranes (PEI/PAA-CSH)n indicated that the hierarchical-structured (PEI/PAA-CSH)n multilayered membrane produced by in situ incorporation of CSH aggregates into PEI/PAA multilayers facilitated its one-step transformation from superhydrophilicity into superhydrophobicity. Both of the superwetting membranes showed better nanofiltration performances for retention of dyes of water and ethanol solution, respectively. Moreover, the long-term performance and antifouling behaviors, investigated by retention of methyl blue (MB), bovine serum albumin (BSA), and humic acid (HA) aqueous water solution and nonaqueous ethanol solution indicated that both of the superhydrophilic and superhydrophobic membrane showed higher stability and excellent antifouling property.Keywords: antifouling effect; nanocomposite membranes; nanofiltration; organic solvent nanofiltration; superhydrophilic membrane; superhydrophobic membrane
Co-reporter:Hao Yan, Jie Li, Hongwei Fan, Shulan Ji, Guojun Zhang, Zhongguo Zhang
Journal of Membrane Science 2015 Volume 481() pp:94-105
Publication Date(Web):1 May 2015
DOI:10.1016/j.memsci.2015.01.047
•Sonication-enhanced in situ assembly of organic/inorganic hybrid membranes.•Ιmprovement of the dispersion of inorganic filler in polymeric matrix in the nanoscale range.•An increase in pervaporation performance by in situ sonication-enhanced strategy.Organic/inorganic hybrid membranes for separation applications have been widely studied. However, achieving a uniform dispersion of inorganic fillers in the polymer matrix is a primary challenge in the advancement of mixed-matrix membranes (MMMs). In the present study, a method for in situ assembly enhanced by sonication was developed to prepare hydrophobic polydimethylsiloxane (PDMS)/nanoparticle hybrid membranes. Results from scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectrometry, and atomic force microscopy (AFM) suggest that through ultrasonic cavitation during assembly of the hybrid membrane, this method could effectively avoid nanoscale agglomeration and in turn uniformly disperse inorganic particles within the polymer matrix. This method thus enabled the preparation of an organophilic membrane with higher hydrophobicity and higher performance. For example, the contact angle (CA) of SiO2/PDMS hybrid membrane increased from 135.5° to 146.3°, and the separation factor for the pervaporation of 5% ethanol/water mixture increased from 7.3 to 12.5. Furthermore, the method was used to prepare a zeolite imidazolate framework-8 (ZIF-8)-filled PDMS membrane. The ZIF-8/PDMS hybrid membrane showed high performance in the pervaporation of alcohol/water mixtures. These results further suggest that in situ assembly via sonication is a promising approach to improve the dispersion of inorganic fillers and thus the membrane performance.
Co-reporter:Linglong Shan, Hongxia Guo, Zhenping Qin, Naixin Wang, Shulan Ji, Guojun Zhang and Zhongguo Zhang
RSC Advances 2015 vol. 5(Issue 15) pp:11515-11523
Publication Date(Web):09 Dec 2014
DOI:10.1039/C4RA11602J
Removal of natural organic matter (NOM) from drinking water by membrane technology is attracting increasing attention. However, the fouling of the membrane by NOM is one of the biggest obstacles restricting its widespread application. Therefore an anti-NOM fouling polyelectrolyte complex (PEC) membrane was obtained by creating a negatively charged multilayer on a polyacrylonitrile (PAN) supporting membrane using a layer-by-layer assembly method. To improve the stability of the PEC membrane, the electrostatically assembled (poly(ethyleneimine)/poly(sodium 4-styrenesulfonate))n/PAN membranes were crosslinked by glutaraldehyde. It was found that the zeta potential of the membrane surface decreased after chemical crosslinking, which further improved the electrostatic repulsion to NOM and thus improved the anti-NOM fouling property. Results of a 30 day nanofiltration operation showed the crosslinked membrane had good stability and gave a higher rejection of NOM; the permeance of the crosslinked membrane was double that of the uncrosslinked membrane.
Co-reporter:Hongwei Fan, Naixin Wang, Shulan Ji, Hao Yan and Guojun Zhang
Journal of Materials Chemistry A 2014 vol. 2(Issue 48) pp:20947-20957
Publication Date(Web):29 Oct 2014
DOI:10.1039/C4TA04114C
Alcohol-permselective membranes may play an increasingly important role in bioalcohol production. Developments for this membrane mostly involve hybrid membranes. Obtaining high compatibility and nanodispersion of inorganic nanoparticles in the polymer matrix is the key to fabricating hybrid membranes with high pervaporation performance. In this study, a homogeneous, nanodisperse ZIF-8/PDMS membrane was prepared by repeated immersion of a polysulfone supporting membrane in a dilute ZIF-8/PDMS suspension and subsequent removal of defects using a concentrated PDMS solution. To improve the nanoscale dispersion of ZIF-8, the nascent ZIF-8 suspension was directly dispersed in a PDMS solution without drying. This procedure avoids aggregation and redispersion of ZIF-8 nanoparticles after forming a powder. Analyses confirmed that the ZIF-8/PDMS dispersion effectively diminished aggregation between nanoparticles and led to the formation of a well-dispersed ZIF-8/PDMS membrane. A homogeneous and thin ZIF-8/PDMS permselective layer was obtained by adjusting the preparation conditions. The prepared ZIF-8/PDMS membrane exhibited a high separation factor (52.81) and high flux (2800.5 g m−2 h−1) in the separation of 5.0 wt% n-butanol–water solution at 80 °C. By comparing the powder-dispersed ZIF-8/PDMS hybrid membrane with the suspension-dispersed ZIF-8/PDMS membrane, we found that the latter showed much higher performance in butanol separation. Therefore, the nanodisperse ZIF-8/PDMS membrane has great potential applications for in situ recovery of biobutanol.
Co-reporter:Lili Gong, Lei Zhang, Naixin Wang, Jie Li, Shulan Ji, Hongxia Guo, Guojun Zhang, Zhongguo Zhang
Separation and Purification Technology 2014 Volume 122() pp:32-40
Publication Date(Web):10 February 2014
DOI:10.1016/j.seppur.2013.10.032
•In situ ultraviolet-light-induced TiO2 nanohybrid superhydrophilic membrane.•The surface contact angle decreased from 62° to 3° after UV irradiation.•A facile way to simultaneously obtain both higher flux and selectivity.The membrane surface property is one of the most important factors that influence the solution–diffusion-controlled pervaporation process. In the present study, a superhydrophilic nanohybrid membrane was successfully prepared by in situ ultraviolet irradiation of titanium dioxide (TiO2) nanoparticles imbedded in polyelectrolyte complexes. The TiO2 precursor solution was dynamically filtered through a layer-by-layer-assembled poly(ethyleneimine)/poly(acrylic acid) multilayer under a specific pressure. Subsequently, ultraviolet radiation was used to improve the hydrophilicity of the nanohybrid membranes via photoinduction of the superhydrophilic property of the TiO2 nanoparticles. When the membranes were irradiated, the surface contact angle decreased from 62° to 3°, which is characteristic of a superhydrophilic membrane surface. The pervaporation performance of the membrane for separating alcohol/water mixtures was investigated. The water content could be enriched from 5 wt% (in the feed) to 99.89 wt% (in the permeate) and the permeate flux was 865 g/(m2 h) in the pervaporation of the ethanol/water mixture. These results indicated that the superhydrophilic surface was beneficial for improving the pervaporation dehydration performance.
Co-reporter:Jie Li, Naixin Wang, Hao Yan, Shulan Ji and Guojun Zhang
RSC Advances 2014 vol. 4(Issue 104) pp:59750-59753
Publication Date(Web):04 Nov 2014
DOI:10.1039/C4RA10655E
Inspired by the complementary roles of surface energy and roughness on natural nonwetting surfaces, a superhydrophobic surface has been successfully designed and prepared by self-assembled monolayer modification on a hierarchical ZIF-8/polymer hybrid membrane. The as-prepared membrane exhibited the best overall performance for n-butanol pervaporation.
Co-reporter:Hongwei Fan;Dr. Qi Shi;Hao Yan; Shulan Ji; Jinxiang Dong; Guojun Zhang
Angewandte Chemie 2014 Volume 126( Issue 22) pp:5684-5688
Publication Date(Web):
DOI:10.1002/ange.201309534
Abstract
The ability to obtain a maximum loading of inorganic nanoparticles while maintaining uniform dispersion in the polymer is the key to the fabrication of mixed-matrix membranes with high pervaporation performance in bioalcohol recovery from aqueous solution. Herein, we report the simultaneous spray self-assembly of a zeolitic imidazolate framework (ZIF)–polymer suspension and a cross-linker/catalyst solution as a method for the fabrication of a well-dispersed ZIF-8–PDMS nanohybrid membrane with an extremely high loading. The ZIF-8–PDMS membrane showed excellent biobutanol-permselective pervaporation performance. When the ZIF-8 loading was increased to 40 wt %, the total flux and separation factor could reach 4846.2 g m−2 h−1 and 81.6, respectively, in the recovery of n-butanol from 1.0 wt % aqueous solution (80 °C). This new method is expected to have serious implications for the preparation of defect-free mixed-matrix membranes for many applications.
Co-reporter:Hongwei Fan;Dr. Qi Shi;Hao Yan; Shulan Ji; Jinxiang Dong; Guojun Zhang
Angewandte Chemie International Edition 2014 Volume 53( Issue 22) pp:5578-5582
Publication Date(Web):
DOI:10.1002/anie.201309534
Abstract
The ability to obtain a maximum loading of inorganic nanoparticles while maintaining uniform dispersion in the polymer is the key to the fabrication of mixed-matrix membranes with high pervaporation performance in bioalcohol recovery from aqueous solution. Herein, we report the simultaneous spray self-assembly of a zeolitic imidazolate framework (ZIF)–polymer suspension and a cross-linker/catalyst solution as a method for the fabrication of a well-dispersed ZIF-8–PDMS nanohybrid membrane with an extremely high loading. The ZIF-8–PDMS membrane showed excellent biobutanol-permselective pervaporation performance. When the ZIF-8 loading was increased to 40 wt %, the total flux and separation factor could reach 4846.2 g m−2 h−1 and 81.6, respectively, in the recovery of n-butanol from 1.0 wt % aqueous solution (80 °C). This new method is expected to have serious implications for the preparation of defect-free mixed-matrix membranes for many applications.
Co-reporter:Haiqi Tang, Shulan Ji, Lili Gong, Hongxia Guo and Guojun Zhang
Polymer Chemistry 2013 vol. 4(Issue 23) pp:5621-5628
Publication Date(Web):12 Jul 2013
DOI:10.1039/C3PY00617D
An automatically controlled spray-layer-by-layer (LbL) assembly method was used to build multilayers onto a tubular ceramic macroporous substrate. Poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAA) were alternately sprayed onto a rotating tubular ceramic substrate. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses of different locations on the substrate confirmed that a fine coating formed on both the top surface and in the pores of the macroporous ceramic substrate. The substrate pretreatment using water filling greatly influenced the self-assembly process, slowing the penetration of the polyelectrolyte into the substrate pores, resulting in different multilayer morphologies. The effects of the substrate pretreatment, number of bilayers, and the addition of salt into the polyelectrolyte solution on the dye rejection performance were investigated. We found that the substrate pretreatment and the addition of NaCl to the polyelectrolyte solution could change the multilayer structure, in turn affecting the separation performance of the composite membranes. The composite membrane consisting of 5 layers of PEI/PAA had a flux of ∼10.0 kg m−2 h−1 and a rejection of >99%. Moreover, spray-LbL assembly using different polymer pairs such as poly(diallyldimethylammonium chloride)/poly(styrenesulfonate) (PDDA/PSS) and PEI/TiBisLac/PAA on vertically held tubular Al2O3 substrates was also explored. Using these materials led to the formation of different types of polymeric multilayers and in situ nanohybrid multilayers. Our study demonstrates that a multilayer membrane can be successfully prepared on a 3D support by an automated spray system, and can easily be used to rapidly coat large areas.
Co-reporter:Ren Wang, Linglong Shan, Guojun Zhang, Shulan Ji
Journal of Membrane Science 2013 Volume 432() pp:33-41
Publication Date(Web):1 April 2013
DOI:10.1016/j.memsci.2013.01.006
Alcohol permselective pervaporation is a promising technology for bio-alcohol production. In this study, a multiple spray technique has been developed to prepare hydrophobic composite membranes for alcohol permselective pervaporation. A defect-free permselective layer was successfully obtained by repeated alternate spraying of dihydroxypolydimethylsiloxane (PDMS) and tetraethylorthosilicate with the addition of dibutyltin dilaurate on to a polysulfone ultrafiltration membrane using an automatic spray system. The effects of PDMS molecular weight and concentration, number of spraying cycles, spraying time and standing interval on the membrane performance were intensively investigated. Experiments proved that, compared with the dip-coated membrane, the membrane flux obtained in this way showed a dramatically increase while the selectivity remained at a comparable level. It was found that the multiple spray technique can ensure that there are no defects in the separation layer, by repeated adjustment of the number of spraying cycles, and can also greatly reduce the thickness of a selective layer. In addition, the automatic spray technology removes the inherent unreliability of manual techniques, so is beneficial for large-scale rapid preparation of composite membranes.Highlights► Multiple sprayed membranes for alcohol permselective pervaporation. ► The layer thickness with five spraying cycles was far less than 1 μm. ► The sprayed membrane flux showed a dramatic increase over the dip-coated one.
Co-reporter:Jie Li, Shulan Ji, Guojun Zhang, and Hongxia Guo
Langmuir 2013 Volume 29(Issue 25) pp:8093-8102
Publication Date(Web):May 23, 2013
DOI:10.1021/la400930y
The use of self-assembled monolayers (SAMs) has recently been recognized as an effective way to tailor the surface properties of films used in various applications. However, application of SAMs in the preparation of separation membranes remains unexplored. In the present study, surface-modified poly(dimethylsiloxane) (PDMS) membranes were prepared using SAMs to fabricate a membrane for use in pervaporation separation of ethanol/water mixtures. A cross-linked PDMS/polysulfone (PSf) composite membrane was transformed by introducing hydroxyl functionalities on the PDMS surface through a UV/ozone conversion process. (Tridecafluoroctyl)triethoxysilane was allowed to be adsorbed on the resulting Si–OH substrate to increase the hydrophobicity of the membrane. Results from Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, atomic force microscopy, and contact angle analyses suggest that the fluoroalkylsilane monolayer was successfully formed on the modified PDMS/PSf membrane treated by 60 min UV/ozone exposure. The newly SAM-modified membrane exhibited a separation factor of 13.1 and a permeate flux of 412.9 g/(m2 h), which are higher than those obtained from PDMS membranes.
Co-reporter:Jie Li, Guojun Zhang, Shulan Ji, Naixin Wang, Wei An
Journal of Membrane Science 2012 Volumes 415–416() pp:745-757
Publication Date(Web):1 October 2012
DOI:10.1016/j.memsci.2012.05.066
In this article, an organic–inorganic nanohybrid multilayer membranes have been developed by incorporating zirconium dioxide (ZrO2) and alumina oxide (Al2O3) nanoparticles into polyelectrolyte complexes such as poly(diallyldimethyl ammonium chloride)/poly(sodium styrene sulfonate) and poly(ethyleneimine)/polyacrylic acid. These nanohybrid multilayers were successfully formed on to both flat sheets and hollow fiber polyacrylonitrile ultrafiltration support membranes by layer-by-layer (LbL) assembly of polycation- and polyanion-coated nanoparticles and used for pervaporation dehydration of an acetone–water mixture. We show that the matching between the size of the NPs and the supporting membrane pore size strongly influences the morphologies and performance of the multilayer membranes. SEM-EDX and AFM analyses suggest that the ZrO2 NPs are mostly distributed on the substrate surface while the Al2O3 NPs are able to migrate into the substrate membrane pores. This is due to the differences between the sizes of the two NPs and results in an increase of the surface roughness of the ZrO2 nanohybrid multilayer membrane while that of the Al2O3 nanohybrid multilayer membrane decreased. The ZrO2 nanohybrid multilayer membrane was able to overcome the trade-off phenomenon, which enabled both higher flux and larger separation factor. However, for the Al2O3 nanohybrid multilayer membrane, the separation factor increased while the corresponding flux values were somewhat lower than those observed for pristine polymeric membranes.Highlights▸ Organic–inorganic nanohybrid multilayer membranes. ▸ Matching between the size of the NPs and the supporting membrane pore size. ▸ Effects of building blocks on pervaporation performance.
Co-reporter:Guojun Zhang, Limin Dai, Lei Zhang, and Shulan Ji
Langmuir 2011 Volume 27(Issue 6) pp:2093-2098
Publication Date(Web):January 31, 2011
DOI:10.1021/la104120b
Electric-field-enhanced layer-by-layer (LbL) assembly of polyelectrolyte and nanohybrid multilayers onto insulating rigid substrates was successfully accomplished using two independent capacitor cells. The influence of external electric field on the multilayer formation was intensively investigated by UV−vis adsorption spectrometry, profilometry, atomic force microscopy, and small-angle X-ray diffraction. This approach was also attempted as a means of fabricating selective layer on flat sheet polymeric porous substrates to obtain the dense composite membranes with high pervaporation performance.
Co-reporter:Naixin Wang, Guojun Zhang, Shulan Ji, Zhenping Qin, Zhongzhou Liu
Journal of Membrane Science 2010 Volume 354(1–2) pp:14-22
Publication Date(Web):15 May 2010
DOI:10.1016/j.memsci.2010.03.002
The layer-by-layer (LbL) assembled polyelectrolyte multilayer has recently been recognized as a new class of promising membrane material for various separation uses. However, there is a lack of understanding about the influences of separation mixtures on the adsorbed polyelectrolytes. Therefore, clear understanding on it would be very important for the design and application of a type of new functional composite membrane. In this paper, the multilayer of weak polyelectrolytes polyethyleneimine and polyacrylic acid was constructed onto a hydrolyzed hollow fiber polyacrylonitrile support membrane under a negative pressure condition. The salt-, pH- and oxidant-responsive pervaporation behaviors of polyelectrolyte multilayer membranes were evaluated by post-treating with sodium chloride, hydrochloric acid, sodium hydroxide and sodium hypochlorite aqueous solutions, respectively. The pervaporation performances for separation of ethanol/water were compared before and after post-treatments. Scanning electron microscopy and atomic force microscopy confirmed the microtopographical changes of membrane surfaces. Optical microscopy was also used to real-time observe surface morphologies of polyelectrolyte multilayers deposited on the quartz substrates. Finally, the comparison of zeta potential values of inner surface before and after post-treatment also demonstrated the changes of surface electrical property.
Co-reporter:Guojun Zhang, Xue Song, Jie Li, Shulan Ji, Zhongzhou Liu
Journal of Membrane Science 2010 350(1–2) pp: 211-216
Publication Date(Web):
DOI:10.1016/j.memsci.2009.12.030
Co-reporter:Guojun Zhang, Zhengang Ruan, Shulan Ji and Zhongzhou Liu
Langmuir 2010 Volume 26(Issue 7) pp:4782-4789
Publication Date(Web):November 11, 2009
DOI:10.1021/la9035453
In this article, a layer-by-layer (LbL)-assembled coordination multilayer on planar and 3D substrates was explored by the alternate deposition of a transition-metal-containing polyelectrolyte and a ligand-containing polymer via the formation of complexes. The metal−ligand coordination between the building blocks of Co2+-exchanged poly(styrene sulfonate) (PSS) and poly(4-vinyl pyridine) (P4 VP) has been demonstrated using UV−vis, FTIR, and XPS. The film thickness, structure, and morphology as well as the wettability as a function of bilayer number have been systematically investigated by profilometry, SEM, AFM, and contact angle analyzers. For the purpose of separation applications, the metal−ligand-coordinated multilayer was assembled on both flat sheet and hollow fiber polymeric porous substrates using a dynamic pressure-driven LbL technique. It was demonstrated that the LbL-assembled PSS(Co)1/2/P4 VP multilayer membrane had high dehydration performance with respect to different solvent−water mixtures; it also had aromatic compound permselectivity from aromatic−aliphatic hydrocarbons and water-softening capacity. Meanwhile, the successful assembly of multilayers on hollow fibers indicates that the dynamic pressure-driven LbL technique is a unique approach to the construction of multilayers on porous 3-D substrates. Therefore, the metal−ligand-coordinated self-assembly could emerge as a powerful technique for the preparation of a range of separation membranes in different types of modules.
Co-reporter:Guojun Zhang, Naixin Wang, Xue Song, Shulan Ji, Zhongzhou Liu
Journal of Membrane Science 2009 Volume 338(1–2) pp:43-50
Publication Date(Web):10 August 2009
DOI:10.1016/j.memsci.2009.04.002
The purpose of this study is to provide some fundamental understanding for the design of industrial hollow fiber pervaporation membrane module. Inner skin hollow fiber pervaporation membrane modules were fabricated by a dynamic negative pressure layer-by-layer (LbL) technique. The influences of dynamic negative pressure and recycling velocity of polyelectrolyte solutions on the formation of non-porous selective layer were firstly investigated using mini-modules during the dynamic assembly process. Since none of reported works dealt with the effects of packing density of hollow fiber module, pilot-scale modules (diameter × length = 1 in. × 20 cm) were therefore prepared by filling different amounts of hollow fibers into a membrane shell. The experimental results show that the higher packing density of 500 m2/m3 rendered both total flux and selectivity to decrease significantly. As for a 1 m long module that has been commonly used in industry, further investigations were conducted using a 1-m long hollow fiber module. The vacuum drop along the axial direction of hollow fibers was noted, especially near to the vacuum suction opening. Despite of this, the relatively high and stable selectivity could be obtained even the fiber length increased to 1 m.
Co-reporter:Guojun Zhang, Xue Gao, Shulan Ji, Zhongzhou Liu
Materials Science and Engineering: C 2009 29(6) pp: 1877-1884
Publication Date(Web):
DOI:10.1016/j.msec.2009.02.015
Co-reporter:Guojun Zhang, Shulan Ji, Xue Gao, Zhongzhou Liu
Journal of Membrane Science 2008 Volume 309(1–2) pp:28-35
Publication Date(Web):15 February 2008
DOI:10.1016/j.memsci.2007.10.012
Extracellular polymeric substances (EPS) are currently considered as the major cause of membrane fouling in membrane bioreactors (MBR). Few works have dealt with the adsorptive interaction between EPS and different membrane types. The purpose of this study was to investigate the adsorptive fouling potential of the EPS extracted from an aerobic bioreactor. Three types of ultrafiltration membranes including polyethersulfone (PES), polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) were evaluated by directly interacting with six sludge samples. It is found that the adsorption capacities were almost saturated after 4 h interaction with EPS in each case. The adsorptive fouling degrees of the three membranes were orderly PAN < PVDF < PES by calculating FRPWF values from the pure water flux before and after adsorption. The microtopographical changes on membrane surfaces were observed by SEM and AFM images. In the case of fouled PAN membranes, most of the membrane surface pore could still be clearly observed in SEM images. This also suggested that the adsorptive fouling of PAN membranes was relatively lower. Synthetically, PES UF membranes were much more severely fouled due to its relatively high roughness and hydrophobicity.
Co-reporter:Guojun Zhang, Xue Gao, Shulan Ji, Zhongzhou Liu
Journal of Membrane Science 2008 Volume 307(Issue 2) pp:151-155
Publication Date(Web):15 January 2008
DOI:10.1016/j.memsci.2007.09.030
In this paper, a novel method was developed to enhance the assembly of polyelectrolyte composite membranes by inducing an electric field during electrostatic adsorption process. The hydrolyzed polyacrylonitrile (PAN) ultrafiltration (UF) membrane was placed in between a capacitor setup. The polyethyleneimine (PEI) was compulsorily assembled on the PAN support under the action of external electric force. Subsequently, the polyelectrolyte composite membranes were evaluated by pervaporation separation of water and alcohol mixture. The membrane obtained with only one PEI layer had a separation factor of 304 and a permeate flux of 512 g/m2 h (75 °C) for pervaporation of 95 wt% ethanol–water mixture. An atomic force microscopy was also used to observe the microtopographical changes. The regularity of the membranes assembled by the new method was also improved in comparison with the membrane assembled by a dynamic layer-by-layer adsorption.
Co-reporter:Hongxia Guo, Mengmeng Chen, Qiang Liu, Ziming Wang, Suping Cui, Guojun Zhang
Desalination (1 June 2015) Volume 365() pp:108-116
Publication Date(Web):1 June 2015
DOI:10.1016/j.desal.2015.01.021
•The low cost SCF condensation polymer was used as anionic building blocks to fabricate nanofiltration membrane.•The multilayered membrane was formed by LbL self-assembly technique.•The membrane showed good separation performance for both cationic ions and dye molecules.The use of new polymeric building block is one of the important routes to extend the layer-by-layer (LbL) assembly technique to fabricate novel nanofiltration (NF) membrane. In this work, the low cost sulfonated cyclohexanone–formaldehyde (SCF) condensation polymer is used as anionic building blocks to prepare a novel positively charged nanofiltration membrane by LbL self-assembly technique. The LbL assembly process was investigated by XRD, FTIR, SEM and AFM measurements. The separation performance of cationic ions and dyes was evaluated by pressure-driven nanofiltration tests. It is found that the multilayer surfaces exhibited periodic variations in positive charges. And the prepared membrane showed an effective rejection of both cationic ions and dyes. The multilayer membrane of 4.5 bilayers exhibited rejections of 92.8% and 90.6% to Ni2 + and Ca2 +, along with flux of 40.8 and 44.9 L/(m2·h·MPa) and pure water flux of 49.3 L/(m2·h·MPa), respectively. Simultaneously, this membrane also showed rejection of 93.7% and 90.8% to RdB and EbT, along with flux of 24.3 and 20.5 L/(m2·h·MPa), respectively. Moreover, the long-term performance stability of the membrane was improved through cross-linking the multilayer membrane.Download high-res image (134KB)Download full-size image
Co-reporter:Hongwei Fan, Naixin Wang, Shulan Ji, Hao Yan and Guojun Zhang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 48) pp:NaN20957-20957
Publication Date(Web):2014/10/29
DOI:10.1039/C4TA04114C
Alcohol-permselective membranes may play an increasingly important role in bioalcohol production. Developments for this membrane mostly involve hybrid membranes. Obtaining high compatibility and nanodispersion of inorganic nanoparticles in the polymer matrix is the key to fabricating hybrid membranes with high pervaporation performance. In this study, a homogeneous, nanodisperse ZIF-8/PDMS membrane was prepared by repeated immersion of a polysulfone supporting membrane in a dilute ZIF-8/PDMS suspension and subsequent removal of defects using a concentrated PDMS solution. To improve the nanoscale dispersion of ZIF-8, the nascent ZIF-8 suspension was directly dispersed in a PDMS solution without drying. This procedure avoids aggregation and redispersion of ZIF-8 nanoparticles after forming a powder. Analyses confirmed that the ZIF-8/PDMS dispersion effectively diminished aggregation between nanoparticles and led to the formation of a well-dispersed ZIF-8/PDMS membrane. A homogeneous and thin ZIF-8/PDMS permselective layer was obtained by adjusting the preparation conditions. The prepared ZIF-8/PDMS membrane exhibited a high separation factor (52.81) and high flux (2800.5 g m−2 h−1) in the separation of 5.0 wt% n-butanol–water solution at 80 °C. By comparing the powder-dispersed ZIF-8/PDMS hybrid membrane with the suspension-dispersed ZIF-8/PDMS membrane, we found that the latter showed much higher performance in butanol separation. Therefore, the nanodisperse ZIF-8/PDMS membrane has great potential applications for in situ recovery of biobutanol.
![Silicic acid (H4SiO4), tetraethyl ester, polymer with α-hydro-ω-hydroxypoly[oxy(dimethylsilylene)]](http://img.cochemist.com/ccimg/155900/155827-81-9.png)
![Silicic acid (H4SiO4), tetraethyl ester, polymer with α-hydro-ω-hydroxypoly[oxy(dimethylsilylene)]](http://img.cochemist.com/ccimg/155900/155827-81-9_b.png)
