Co-reporter:Ming Wang, Yue Cao, Zhen-Liang Xu, Yu-Xuan Li, and Shuang-Mei Xue
ACS Sustainable Chemistry & Engineering November 6, 2017 Volume 5(Issue 11) pp:10283-10283
Publication Date(Web):September 18, 2017
DOI:10.1021/acssuschemeng.7b02300
Superhydrophilic stainless steel hollow fiber microfiltration membranes (SSHF-MFs) were developed through a facile dip-coating method, followed by sintering at a low temperature of 500 °C. A novel mediating additive was explored to mediate the coating suspensions. The additive, which could form hydrogen bonds with TiO2 agglomerations, facilitated the formation of a continuous TiO2 layer on the rough surface of stainless steel hollow fibers (SSHFs). The fabricated SSHF-MFs exhibited superhydrophilic and underwater superoleophobicity wettability, which enabled SSHF-MFs to be applied to antifouling fields. The fouling resistance of SSHF-MFs for oil/water emulsion, cake layer foulant (sodium alginate, SA), and adhesive foulant (bovine serum albumin, BSA) were investigated systematically. SSHF-MFs exhibited superior antifouling properties and high rejections of 99% and 90% for oil/water emulsion and SA foulant solution, respectively. For the adhesive BSA solution, SSHF-MFs still showed good antifouling property after washing with a dilute alkaline solution and superior separation performance (90%). Meanwhile, SSHF-MFs exhibited an excellent separation performance for polystyrene microspheres (100 nm) with a rejection of 100%. In conclusion, SSHF-MFs showed great potential, not only in traditional microfiltration fields, such as solid–liquid separation, but also in the antifouling field, such as oil/water separation. The facile fabrication conditions and superior wettability further improved the sustainability of SSHF-MFs in practical applications.Keywords: Antifouling; Hydrogen bond; Microfiltration; Oil/water separation; Superwettability;
Co-reporter:Liwei Zhuang, Hanfei Guo, Gance Dai, Zhen-liang Xu
Journal of Membrane Science 2017 Volume 526() pp:73-93
Publication Date(Web):15 March 2017
DOI:10.1016/j.memsci.2016.12.018
•The inlet manifold affects greatly the fluid flow distribution and energy consumption of the module.•A novel CFD model has been developed to simulate the fluid flow in an industrial-scale hollow fiber membrane module.•An adapted model has been proposed to account for the energy consumption distribution between the manifold and the fiber bundle.•The velocity and pressure distributions in the shell and lumen sides have been presented as well as the three-dimensional flux distribution.•Proposals have been given for better design of the module.Non-uniform flow in the hollow fiber membrane modules is believed to cause non-ideal performance of the module. To investigate the relationship between the module design and performance, a novel CFD model was developed to analyze numerically the effect of inlet manifold on the energy consumption and flow distribution for the module. The CFD results were compared with the experimental data and a good agreement between them was obtained. Eight manifolds were chosen as cases in the CFD simulation. The flow field in the shell and lumen sides and the flux distribution in the porous membrane zone were revealed by the CFD simulation. An adapted model has been proposed to account for the energy consumption distribution between the manifold and the fiber bundle. The manifold can consume a considerable portion of the overall energy with an improper structure design. When the fractional hole area of the inlet are 0.64%, 43.42%, and 100%, the proportion of the energy consumed by the manifold are 95%, 51%, and 7%, respectively. The non-uniform flow from the shell manifold to the module results in uneven velocity and pressure distributions in the shell side. However, the effect of the manifold structure on the flow distribution in the lumen side appears to be negligible. The flux distribution has a three-dimensional non-uniformity. The high velocity from the manifold opening to the module causes a high local flux at the beginning of the fiber, whereas the flow impingement on the dead end and the pressure drop in the lumen side results in a high local flux at the end of the fiber. The uniformity of the flux distribution depends on the flow distribution in the shell side with given fiber properties. For the specific hollow fiber membrane module in the present study, the inlet holes should be evenly distributed at the cross section to achieve uniform flow distribution in the module. To reduce the energy consumption, the fractional hole area should be as high as possible. The CFD model and the mechanism of how the inlet manifold affects the performance of the module will be beneficial to the structure design and optimization of the hollow fiber membrane modules.
Co-reporter:Hai-Zhen Zhang, Zhen-Liang Xu, Hao Ding, Yong-Jian Tang
Desalination 2017 Volume 420(Volume 420) pp:
Publication Date(Web):15 October 2017
DOI:10.1016/j.desal.2017.07.011
•MWCNTs-OH was modified by grafting with PIP.•Tri-pores positively charged NF membrane was fabricated with modified MWCNTs in aqueous solution.•The prepared NF membrane showed highly improved permeability and good separation for Mg2 + and Li+.High water permeability and good separation property are greatly desired in water production due to energy concerns. To explore nanofiltration (NF) membrane with high permeability for cations separation, a positively charged NF membrane was fabricated via interfacial polymerization using polyethersulfone (PES) three-channel capillary ultrafiltration (UF) membrane as substrate, polyethyleneimine (PEI) as the aqueous precursor. The NF membrane preparation conditions were optimized. To enhance the permeability of the prepared NF membrane, modified hydroxyl contained multi-walled carbon nanotubes (MWCNTs-OH), grafting with piperazine (PIP), were utilized. The resultant NF membrane showed increased water flux from 20.8 L·m− 2·h− 1 to 56.1 L·m− 2·h− 1 at 4 bar after adding 0.01 wt% modified MWCNTs-OH in aqueous solution. Interestingly, MgCl2 rejection of the membrane also increased from 94.2% to 96.9%. The positively charged NF membrane exhibited above 97% rejection for divalent cations (Mg2 + and Ca2 +) and low rejection (< 70%) for monovalent cations (Na+ and Li+), and it also showed long durability and good separation for Mg2 + and Li+ when the membrane was used to separate mixed salts solution simulated the composition of salt lake brine. The fabricated membrane would have potential for effective water softening and for reclamation of lithium from brine or seawater with high Mg2 +/Li+ ratio.Download high-res image (186KB)Download full-size image
Co-reporter:Qiong Wu, Gui-E. Chen, Wei-Guang Sun, Zhen-Liang Xu, Ya-Fang Kong, Xiao-Peng Zheng, Sun-Jie Xu
Chemical Engineering Journal 2017 Volume 313(Volume 313) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.cej.2016.12.079
•Co-polymer F127 and nanocomposite GO-Ag were employed to enhance surface property.•Fouling resistance assessment to natural organic matter (NOM) after alternatively backwash was conducted.•Modified membranes exhibited improved hydrophilicity and anti-fouling.The modified membrane GO-Ag/PVDF was fabricated using co-polymer F127 and nanocomposite GO-Ag as functional additives via non-solvent induced phase separation (NIPS) method for natural organic matter (NOM) resistance. Due to the introduction of co-polymer F127 and nanocomposite GO-Ag, resultant membranes exhibited excellent hydrophilicity and permeability. Meanwhile, the modified membrane surface showed better fouling resistance to natural organic matter (NOM) and bacteria compared with pristine membrane. In summary, the membrane MF1825 under the optional additive combination possessed the better performance with pure water flux of 82 L·m−2·h−1 and the contact angle of 62° comparing the membrane MF1800 with pure water flux of 14 L·m−2·h−1 and the contact angle of 80°. In addition, the membrane MF1825 had the improved fouling resistance order to NOM models: BSA > SA > HA, which indicated a potential application in natural organic water treatment.Download high-res image (208KB)Download full-size image
Co-reporter:Sheng-Hui Liu, Min Liu, Zhen-Liang Xu, Yong-Ming Wei, Xin Guo
Journal of Membrane Science 2017 Volume 528(Volume 528) pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.memsci.2017.01.028
•Sol-gel process assisted RTIPS method was applied.•PES-TiO2 hybrid membranes were successfully synthesized.•PES-TiO2 hybrid membranes by RTIPS showed better properties than NIPS.•Hybrid membrane exhibited unique performance than blank membrane.A new attempt to prepare polyethersulfone (PES)-Titania (TiO2) organic-inorganic hollow fiber hybrid membranes were investigated by sol-gel process assisted reverse thermally induced phase separation (RTIPS) method. The membrane formation mechanism underwent NIPS (coagulation temperature lower than cloud point) or RTIPS (coagulation temperature higher than cloud point) process. Properties of hollow fiber hybrid membranes, which varied with TiO2 sol addition and coagulation temperature, were investigated by SEM, EDX, AFM, TGA, XPS and contact angle. SEM results showed that the dense skin layer was produced in the hybrid membranes via NIPS process, while porous skin layer and sponge-like structures emerged in the hybrid membranes via RTIPS process. As a result, pure water flux, BSA rejection, mechanical properties of hybrid membranes by RTIPS were higher than that via NIPS. EDX mapping spectra proved that the dispersion uniformity of TiO2 particles through sol-gel process on the top surface of 1 wt% TiO2 embedded PES membrane, which prepared in 60 °C coagulation bath. XPS data revealed the element distribution in the hybrid membranes. AFM and TGA revealed increased surface roughness and thermal stability of the hybrid membranes by the addition of TiO2 sol, respectively. The organic-inorganic hybrid membranes prepared with 1 wt% TiO2 sol content by RTIPS method exhibited decent performance, which reached maximum pure water flux of 1046 L/(m2h) and BSA rejection of 75%.Download high-res image (250KB)Download full-size image
Co-reporter:Hai-Zhen Zhang, Zhen-Liang Xu, Yong-Jian Tang, Hao Ding
Journal of Membrane Science 2017 Volume 527(Volume 527) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.memsci.2016.12.059
•PES three-channel NF membrane with inner selective layer was fabricated.•NF membrane shows water flux of 36.1 LMH and Na2SO4 rejection of 96.8% at 4 bar.•NF membrane can tolerant 13000 ppm-h Cl at 4 bar and more than 3.84×105 ppm-h Cl at 0 bar.Good mechanical strength, high water flux and salt rejection, and highly chlorine-tolerant property are essential for nanofiltration (NF) membrane. To achieve these properties, polyethersulfone (PES) NF thin-film composite (TFC) membrane was prepared via interfacial polymerization using piperazine (PIP) and 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline (BHTTM) as aqueous monomers, trimesoyl chloride (TMC) as organic monomers, and PES three-channel capillary ultrafiltration (UF) membrane as substrate. The prepared NF membrane displays pure water flux of 36.1 L m−2 h−1 and Na2SO4 rejection of 96.8% at 4 bar. NaClO solution was used to treat NF membranes for the evaluation of NF membrane chlorine-tolerant property. The effects of NaClO concentration, contact time and operating pressure on the chlorine-tolerant property of NF membrane have been thoroughly investigated. Particularly, the durability of NF membrane versus Cl was tested though long-term test. The pure water flux and Na2SO4 rejection of NF membrane after 5000 ppm-h NaClO immersion was 43.4 L m−2 h−1 and 99.8% at 4 bar, respectively. The fabricated NF membrane could tolerant 13000 ppm-h Cl under 4 bar, and the water flux and Na2SO4 rejection are maintain at 51.6 L m−2 h−1 and 99.6% during NF running process, respectively. Moreover, NF membrane exhibits 3.84×105 ppm-h chlorine-tolerant at 0 bar. These results indicated that the fabricated PES three-channel capillary NF membrane could be applied to practical process of desalination or water softening.Download high-res image (188KB)Download full-size image
Co-reporter:Yong-Jian Tang, Zhen-Liang Xu, Shuang-Mei Xue, Yong-Ming Wei, Hu Yang
Journal of Membrane Science 2017 Volume 541(Volume 541) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.memsci.2017.07.033
•Freeman theory is implemented by mixing the flexible monomer-PIP and the rigid monomer-BPF.•Synergism effect of BPF and PIP on NF membrane performance is studied thoroughly.•Increasing the backbone stiffness is an effective way to obtain the remarkable NF membrane.According to the Freeman theory, increasing the backbone stiffness to some extent is an effective way to obtain the remarkable membrane with both high permeability and selectivity. In this work, a high performance nanofiltration (NF) membrane was prepared via tailoring the polyester/polyamide backbone stiffness. The flexible monomer-piperazine (PIP) and the rigid monomer-bisphenol F (BPF) were selected as the aqueous phase monomers, and they were interfacial reacted with trimesoyl chloride (TMC) on the polyethersulfone (PES) UF membrane to generate the polyester/polyamide layer. By mixing PIP with BPF, both of the polyester/polyamide backbone stiffness and microporosity degree enhanced. As a result, the PIP/BPF NF membrane possessed a 2.6-fold pure water flux (PWF) of the PIP NF membrane (the salt rejection remained at the same level), and 4.8-fold PWF of the BPF NF membrane. Our results revealed a novel and facile way to improve the NF membrane performance.Download high-res image (322KB)Download full-size image
Co-reporter:Yong-Jian Tang, Zhen-Liang Xu, Shuang-Mei Xue, Yong-Ming Wei, Hu Yang
Journal of Membrane Science 2017 Volume 538(Volume 538) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.memsci.2017.05.049
•A novel TFC NF membrane was fabricated by mixing the PIP and NH2-PEG-NH2.•The synergy of NH2-PEG-NH2 and PIP on the NF membrane property was studied thoroughly.•The membrane possessed very high rejection and chlorine resistance.A novel polypiperazine-amide nanofiltration (NF) membrane with very high salt rejection was successfully developed in this work. The NF membrane chlorine-tolerant ability were improved greatly after mixing a small amount of α,ω-diamino poly(ethylene glycol) (NH2-PEG-NH2) with piperazine (PIP) in the aqueous phase. The XPS result demonstrated that the polymerization degree of the NF membrane was notably enhanced with the addition of NH2-PEG-NH2. The solute rejections and chlorine tolerance were improved remarkably, while the permeate flux remained almost at the same level. When the NH2-PEG-NH2 (2 kDa) content in the total amine was 1%w/w (0.01%w/v in the aqueous solution), NF membrane performance was optimal. This membrane exhibited a pure water flux (PWF) of 34.9 L m−2 h−1 along with Na2SO4, MgSO4, MgCl2 and NaCl rejections of 99.5%, 99.2%, 90.9% and 58.3% (2000 ppm, 6 bar, 25 °C), respectively. Moreover, the NF membrane performance was maintained after being treated by 14,000 ppm NaClO for 1 h. Therefore, adding a small amount of NH2-PEG-NH2 in the aqueous phase could be considered to be an effective way to improve the polypiperazine-amide NF membrane chlorine-tolerant ability.
Co-reporter:Yue Cao, Ming Wang, Zhen-liang Xu, Xiao-hua Ma, and Shuang-mei Xue
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 38) pp:25386
Publication Date(Web):September 7, 2016
DOI:10.1021/acsami.6b08092
A novel seeding method combining interfacial polymerization (IP) technique with dip-coating operation was designed for directly coating nanosized NaA seed crystals (150 nm) onto the micrometer-sized α-Al2O3 hollow fiber support, in which the polyamide (PA) produced by IP acted as an effective medium to freeze and fix seed crystals at the proper position so that the controlled seed layer could be accomplished. While a coating suspension with only 0.5 wt % seed content was used, a very thin seed layer with high quality and good adhesion was achieved through dip coating twice without drying between, and the whole seeding process was operated at ambient conditions. The resulting zeolite NaA membranes not only exhibited high pervaporation (PV) performance with an average separation factor above 10000 and flux nearly 9.0 kg/m2·h in dehydration of 90 wt % ethanol aqueous solution at 348 K but also demonstrated great reproducibility by testing more than eight batches of zeolite membranes. In addition, this seeding strategy could be readily extended to the preparation of other supported zeolite membranes for a wide range of separation applications.Keywords: alumina; ceramic hollow fiber; dehydration; interfacial polymerization; NaA; pervaporation; zeolite membrane
Co-reporter:Chen-Hao Ji, Shuang-Mei Xue, and Zhen-Liang Xu
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 40) pp:27243
Publication Date(Web):September 28, 2016
DOI:10.1021/acsami.6b10053
A novel carbohydrate chain cross-linking method of sodium alginate (SA) is proposed in which glycogen with the branched-chain structure is utilized to cross-link with SA matrix by the bridging of glutaraldehyde (GA). The active layer of SA composite ceramic membrane modified by glycogen and GA for pervaporation (PV) demonstrates great advantages. The branched structure increases the chain density of the active layer, which compresses the free volume between the carbohydrate chains of SA. Large amounts of hydroxyl groups are consumed during the reaction with GA, which reduces the hydrogen bond formation between water molecules and the polysaccharide matrix. The two factors benefit the active layer with great improvement in swelling resistance, promoting the potential of the active layer for the dehydration of an ethanol–water solution containing high water content. Meanwhile, the modified active layer is loaded on the rigid α-Al2O3 ceramic membrane by dip-coating method with the enhancement of anti-deformation and controllable thickness of the active layer. Characterization techniques such as SEM, AFM, XRD, FTIR, XPS, and water contact angle are utilized to observe the composite structure and surface morphology of the composite membrane, to probe the free volume variation, and to determine the chemical composition and hydrophilicity difference of the active layer caused by the different glycogen additive amounts. The membrane containing 3% glycogen in the selective layer demonstrates the flux at 1250 g m–2 h–1 coupled with the separation factor of 187 in the 25 wt % water content feed solution at the operating temperature of 75 °C, reflecting superior pervaporation processing capacity compared with the general organic PV membranes in the same condition.Keywords: branched carbohydrate chain; glycogen; high-flux organic pervaporation membrane; sodium alginate; swelling resistance
Co-reporter:Shuang-Mei Xue, Zhen-Liang Xu, Yong-Jian Tang, and Chen-Hao Ji
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 29) pp:19135-19144
Publication Date(Web):July 7, 2016
DOI:10.1021/acsami.6b05545
In this work, three modified multiwalled carbon nanotubes (MWCNTs) with carboxyl (MWCNT-COOH), hydroxyl (MWCNT-OH) and amino groups (MWCNT-NH), respectively, were added into the aqueous phase containing piperazine (PIP) to fabricate the nanocomposite nanofiltration (NF) membranes via interfacial polymerization. The influences of functional groups of MWCNTs on the performance of modified NF membrane were investigated. The MWCNTs were characterized by TEM, FT-IR and TGA; meanwhile, the properties of the membranes were evaluated by XPS, TEM, AFM and contact angle. The XPS results proved the successful incorporation of MWCNT in the active layer of modified NF membrane. When the MWCNT concentration is 0.01% (w/v), all the nanocomposite membranes possessed the optimal separation properties, among which the membrane incorporated with MWCNT-OH demonstrated the highest water flux of 41.4 L·m–2·h–1 and the Na2SO4 rejection of 97.6% whereas the one with MWCNT-COOH had the relative lowest rejection of 96.6%. Furthermore, the increased hydrophilicity of functional groups in modified MWCNTs resulted in different nodular surface morphologies, thicknesses and hydrophilicities of the nanocomposite membranes. All the membranes possessed a molecular weight cutoff (MWCO) within 300 Da and good operation stability.
Co-reporter:Yong-Jian Tang, Zhen-Liang Xu, Ben-Qing Huang, Yong-Ming Wei and Hu Yang
RSC Advances 2016 vol. 6(Issue 51) pp:45585-45594
Publication Date(Web):25 Apr 2016
DOI:10.1039/C6RA05716K
Recently, poly(amidoamine) (PAMAM) has emerged as a novel material due to its high density of functional groups, hyper-branched structure and hydrophilic nature. PAMAM has been used as a monomer during an interfacial polymerization process for the fabrication of nanofiltration membranes. Previous work has focused on the low generation of PAMAM (G0, G1 and G2), however, the high generation of PAMAM (G4 and G5) still lacks investigation. This work focuses on the preparation of nanofiltration membranes, which are made of PAMAM–NH2 G4 and PAMAM–NH2 G5. By optimizing the concentration of PIP and SiO2 gel in the aqueous solution, the pure water flux improved by 106% while separation properties are kept at the same level. XPS, EDS, SEM, AFM and contact angle were used to characterize the NF membrane properties. The PAMAM/PIP/SiO2 membrane prepared under the optimum conditions exhibited a pure water flux of 38.5 L m−2 h−1 and Na2SO4 rejection of 92.0% under 0.6 MPa. The PAMAM/PIP/SiO2 membrane’s robust long-time running performance showed its good potential in practical applications.
Co-reporter:Min Liu;Shenghui Liu;Zhenliang Xu
Frontiers of Chemical Science and Engineering 2016 Volume 10( Issue 1) pp:57-75
Publication Date(Web):2016 March
DOI:10.1007/s11705-016-1561-7
A review of recent research related to microporous polymeric membranes formed via thermally induced phase separation (TIPS) and the morphologies of these membranes is presented. A summary of polymers and suitable diluents that can be used to prepare these microporous membranes via TIPS are summarized. The effects of different kinds of polymer materials, diluent types, cooling conditions, extractants and additive agents on the morphology and performance of TIPS membranes are also discussed. Finally new developments in TIPS technology are summarized.
Co-reporter:Zhe-Qin Dong, Bao-Juan Wang, Xiao-hua Ma, Yong-Ming Wei, and Zhen-Liang Xu
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 40) pp:22652
Publication Date(Web):September 27, 2015
DOI:10.1021/acsami.5b07454
This study develops a novel type of electrospun nanofiber membranes (ENMs) with high permeability and robust superhydrophobicity for membrane distillation (MD) process by mimicking the unique unitary microstructures of ramee leaves. The superhydrophobic ENMs were fabricated by the eletrospinning of poly(vinyl alcohol) (PVA), followed by chemical cross-linking with glutaraldehyde and surface modification via low surface energy fluoroalkylsilane (FAS). The resultant FAS grafted PVA (F-PVA) nanofiber membranes were endowed with self-cleaning properties with water contact angles of 158° and sliding angles of 4° via the modification process, while retaining their high porosities and interconnected open structures. For the first time, the robust superhydrophobicity of the ENMs for MD was confirmed by testing the F-PVA nanofiber membranes under violent ultrasonic treatment and harsh chemical conditions. Furthermore, vacuum membrane distillation experiments illustrated that the F-PVA membranes presented a high and stable permeate flux of 25.2 kg/m2h, 70% higher than those of the commercial PTFE membranes, with satisfied permeate conductivity (<5 μm/cm) during a continuous test of 16 h (3.5 wt % NaCl as the feed solution, and feed temperature and permeate pressure were set as 333 K and 9 kPa, respectively), suggesting their great potentials in myriad MD processes such as high salinity water desalination and volatile organiccompounds removal.Keywords: eletrospinning; membrane distillation; nanofiber membrane; poly(vinyl alcohol); superhydrophobicity
Co-reporter:Zhe-Qin Dong, Xiao-Hua Ma, Zhen-Liang Xu and Zhi-Yun Gu
RSC Advances 2015 vol. 5(Issue 83) pp:67962-67970
Publication Date(Web):04 Aug 2015
DOI:10.1039/C5RA10575G
Electrospun nanofiber membranes having a hierarchical structure with multilevel roughness were generated via electrospinning of poly(vinylidene fluoride) (PVDF)–SiO2 blend solutions. The composite PVDF–SiO2 nanofiber membranes were then endowed with superhydrophobicity by the fluorosilanization of the surface with low surface energy fluoroalkylsilane (FAS). The results showed that when the SiO2 content in the dope solutions increased from 0 wt% to 8 wt%, the water contact angles of the FAS modified nanofiber membranes increased significantly from 130.4° to 160.5°. The increment of the silica content in the dope solutions decreased the fiber diameters and pore sizes of the modified membranes, while the mechanical properties were enhanced with the silica addition. The liquid entry pressures of the membranes increased gradually from 84 kPa to 195 kPa with silica addition due to the increased contact angles and decreased pore size. Vacuum membrane distillation experiments were carried out for the modified nanofiber membranes to evaluate the anti-wetting properties. The optimal superhydrophobic nanofiber membrane maintained a stable flux of 31.5 kg m−2 h−1 with a permeate conductivity approximately 10 μs cm−1 over the entire test, while the fluxes and conductivities of the nanofiber membranes without superhydrophobicity showed a significant decrease and increase, respectively. The results indicated that the superhydrophobic modification process rendered the nanofiber membrane anti-wetting properties without compromising its excellent permeability.
Co-reporter:Long-Bao Zhao;Min Liu;Yong-Ming Wei;Min-Xian Xu;Bang-He Jiang
Polymers for Advanced Technologies 2015 Volume 26( Issue 4) pp:353-361
Publication Date(Web):
DOI:10.1002/pat.3460
A series of hyperbranched polyesters (HBPEs) using trimethylolpropane (TMP) as a core were synthesized via an esterification reaction, and the molecular weights of these HBPEs were 1600, 2260, 3370, and 5170 g/mol, respectively. Then, these HBPEs were added into dope solutions to prepare PSf hollow fiber membranes via a wet-spinning method. When the HBPE molecule weight increased from 1600 to 5170 g/mol, the initial viscosities of the PSf–HBPE–PEG400–DMAc dope solutions increased, and the shear-thinning phenomenon of these dope solutions became increasingly obvious. When these dope solutions were immersed into the deionized water, the demixing rate increased with an increase in the HBPE molecule weight at first and then decreased; this results in the increase of membrane porosity and the coexistence of finger-like and sponge-like structures. With the addition of HBPE, the start pure water contact angle and the mean effective pore size of the membranes decreased, and the Jw increased. For the mechanical properties of the membranes, the breaking strength and the elongation of the membranes also increased. Copyright © 2015 John Wiley & Sons, Ltd.
Co-reporter:Xiao-Hua Ma, Zhe-Qin Dong, Ping-Yun Zhang, Qi-Feng Zhong, Zhen-Liang Xu
Materials Letters 2015 Volume 156() pp:58-61
Publication Date(Web):1 October 2015
DOI:10.1016/j.matlet.2015.04.145
•Superhydrophilic and ultrafine PVDF nanofibers were successfully fabricated.•The obtained fibers had high porosities and roughness surfaces.•The obtained fibers also had high pure water flux.Superhydrophilic and ultrafine polyvinylidene fluoride (PVDF) electrospun nanofibrous membranes (ENMs) were successfully fabricated by electrospinning based on an in situ free radical polymerization. The properties of electrospinning solution were investigated, as well as the morphologies and hydrophilicity of ENMs. The results showed that PVDF ENMs with in situ free radical polymerization had high porosities and rough surfaces endowing their surfaces superhydrophilicities. The water contact angle reduced from 135° to 0° within 0.2 s.
Co-reporter:Gui-E Chen;Li Sun;Hu Yang
Korean Journal of Chemical Engineering 2015 Volume 32( Issue 12) pp:2492-2500
Publication Date(Web):2015 December
DOI:10.1007/s11814-015-0105-z
The surface modification of poly (vinylidene fluoride) (PVDF) membrane was performed via a two-step polymerization reactions. Poly (acrylic acid) (PAAc) was first grafted onto the membrane surface for the preparation of PVDF-g-PAAc membrane, and then poly (ethylene glycol) 200 (PEG 200) was immobilized on the membrane surface by the esterification reaction for the fabrication of PVDF-g-PEGA membrane. Attenuated total reflectance (ATR) FTIR, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and protein adsorption, water flux, water content and dynamic contact angle were conducted to characterize the structures and performance of the resultant PVDF membranes. The experimental results showed that the adsorption of bovine serum albumin (BSA) on the PVDF-g-PEGA membrane decreased about 80% when the grafting ratio reached to 15 wt%, compared with the pristine PVDF membrane. Moreover, the water contact angle of the membrane dropped to 60.5°, while the membrane pore sizes remained little changed.
Co-reporter:Xiao-Hua Ma, Hui-Xin Zhang, Si-Wen Gu, Yue Cao, Xin Wen, Zhen-Liang Xu
Separation and Purification Technology 2014 Volume 132() pp:370-377
Publication Date(Web):20 August 2014
DOI:10.1016/j.seppur.2014.04.038
•Difunctional membranes performed high catalytic and separating performances simultaneously.•The methyl laurate production process was optimized in the membrane reactor.•A kinetics model was established and agreed well with experimental results.Difunctional hollow fiber ceramic composite membranes with self-sufficient catalysis and separation properties were successfully fabricated through thermal imidization, followed by dip-coating method. The structure, separation and catalysis properties of the fabricated difunctional membrane were investigated by SEM, pervaporation dehydration of methanol aqueous solution, and esterification of methanol and lauric acid to produce methyl laurate in a membrane reactor, respectively. The results showed that the obtained difunctional membrane was characterized by a multilayer structure: a sponge-like support layer, a dense separation layer and a porous catalysis layer. The porous catalysis layer had little effect on separation property. But it provided a large specific surface area for perfluorosulfonic acid (PFSA), resulting in a good catalytic effect. The obtained difunctional membrane also showed an excellent stability and repeatability. The optimized operating conditions were methanol to lauric acid ratio of 10:1, reaction temperature of 70 °C, and catalyst dosage of 1.0 wt% in this work. A mathematical model was established to describe this experimental process and the predicted results agreed well with the experimental results.
Co-reporter:Yi-Ting Ye, Xiao-Hua Ma, Zhen-Liang Xu, and Ying Zhang
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 1) pp:346-354
Publication Date(Web):2017-2-22
DOI:10.1021/ie4024534
Theophylline (THO) molecular imprinted composite membranes (MIM) were successfully prepared by thermal-initiated free radical polymerization on the surface of α-Al2O3 ceramic microporous hollow fiber substrate membranes. Molecular imprinted polymerization layer was synthesized by taking theophylline as the template molecule, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the cross-linker, and 2,2′-azobisisobutyronitrile (AIBN) as the free-radical initiator. After polymerization and the elution of the imprinted molecule, the Rmax (the maximum pore size) upon the membrane surface decreased from 2.8 to 1.9 μm. The imprinted layer upon the ceramic membranes was investigated by scanning electron microscopy (SEM), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FTIR). SEM micrographs showed a 1 μm thick composite membrane, and AFM showed different surface roughness. Moreover, the selectivity separation factor of theophylline (THO) to theobromine (TB) was determined as 2.63 in a mixed feed solution, thus suggesting that the imprinting process allowed for preferential permeance and affinity selectivity to THO.
Co-reporter:Gui-E Chen;Wen-Zhi Wu;Ping-Yun Zhang
Journal of Applied Polymer Science 2014 Volume 131( Issue 6) pp:
Publication Date(Web):
DOI:10.1002/app.39987
ABSTRACT
Poly(vinylidene fluoride) (PVDF) membranes were prepared with various residence times using water–ethanol (50 : 50, mass ratio) and pure ethanol coagulants as first coagulant, respectively. The physical properties of PVDF solution after free radical polymerization were investigated by dynamic light scattering (DLS), scanning electron microscopy (SEM), viscosity, precipitation kinetics, and surface tension. Resultant PVDF membranes were characterized by SEM, contact angle, mechanical properties, and filtration properties. The results showed that the longer residence time in the first coagulant contributed to the filtration properties improvement. Contact angles of the top-surfaces and bottom-surfaces of membranes decreased as residence time increasing in the first coagulant, and the top-surface showed better hydrophilicity than that of the bottom-surface. The pore size distributions of PVDF membranes showed that the dominating demixing process of the casting solution in water–ethanol coagulant was 5 s, and in that of ethanol was 10–15 s. Additionally, the short-time delay demixing process in water–ethanol first coagulant resulted in a thin dense layer near the top surface, and the longer time delay demixing process in that of ethanol contributed to the shift of the inter-globules to the cellular morphology in the case of the residence time increasing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39987.
Co-reporter:Long-Bao Zhao, Zhen-Liang Xu, Min Liu, Yong-Ming Wei
Journal of Membrane Science 2014 454() pp: 184-192
Publication Date(Web):
DOI:10.1016/j.memsci.2013.11.057
Co-reporter:Xiao-Hua Ma;Yu Bai;Yue Cao
Korean Journal of Chemical Engineering 2014 Volume 31( Issue 8) pp:1438-1443
Publication Date(Web):2014 August
DOI:10.1007/s11814-014-0060-0
Porous stainless steel hollow fiber has been widely used due to its high mechanical strength, excellent thermal conductivity and good sealing properties compared with other porous supports. We successfully prepared porous stainless steel hollow fibers using polyacrylonitrile (PAN) as polymer via dry-wet spinning followed by sintering through temperature programming method. The PAN concentration had an obvious impact on the structure and property of porous stainless steel hollow fiber even if it would be burned off during sintering. The results showed that the morphology could be tuned by adjusting the concentration of PAN. With increasing PAN concentration in casting solution for spinning, the viscosity was increased dramatically, resulting in much compact structures with high pure water flux (higher than 3×105 L·m−2·h−1·Pa−1). A more dense structure could be obtained by adding additive polyvinylpyrrolidone (PVP) as viscosity enhancer.
Co-reporter:Min Liu, Yong-Ming Wei, Zhen-Liang Xu, Run-Qing Guo, Long-Bao Zhao
Journal of Membrane Science 2013 Volume 437() pp:169-178
Publication Date(Web):15 June 2013
DOI:10.1016/j.memsci.2013.03.004
► A RTIPS process for the preparation of polyethersulfone membrane was reported.► Casting solution with LCST was used for membrane fabrication.► Phase separation is induced by heat transfer in the reverse way of general TIPS.► PES symmetrical membrane with porous skin layer was prepared via the RTIPS process.► Significant improvement in performance of PES membranes was observed.Microporous polyethersulfone (PES) flat-sheet membranes were successfully prepared by reverse thermally induced phase separation (RTIPS) in which the membrane-forming system that was employed featured a low critical solution temperature (LCST) and consisted of PES, N,N-dimethylacetamide (DMAc) and polyethylene glycol (PEG200). Light transmittance was used to follow the cloud point and precipitation rate of the casting solution during the RTIPS process. The morphology of the formed membranes was investigated using scanning electron microscopy (SEM); the corresponding permeation properties of the membranes, such as pure water permeation flux, rejection rate and mechanical properties were also investigated. The results showed that the cloud point decreased with the increasing mass ratio of PEG200/DMAc. SEM images revealed that the membrane structure could be changed from exhibiting finger-like pores to exhibiting a bicontinuous structure along its cross-section using the RTIPS process; it was also observed that the dense skin layer was converted to a porous surface. It was concluded that membranes which prepared by the RTIPS process have a low ratio of maximum pore size to mean pore size. A PES flat-sheet microporous membrane with a higher pure water permeation flux of 1040 L m−2 h−1 (0.1 MPa) was obtained via the RTIPS method described in this work. Moreover, with the same mass ratio of PEG200/DMAc, the mechanical strengths of membranes prepared via RTIPS were better than those prepared by the nonsolvent induced phase separation (NIPS) method.
Co-reporter:Xiao-Hua Ma, Xin Wen, and Zhen-Liang Xu
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 17) pp:5958-5966
Publication Date(Web):April 3, 2013
DOI:10.1021/ie301016w
Difunctional hollow fiber composite membranes (DHFCMs) with catalytic and separative properties were used as structured packing in reactive distillation to separate ethanol–water and to catalyze ethanol–acetic acid esterification without other catalysts. These fibers showed more excellent properties over conventional packing in the ethanol–water distillation, which worked 10-fold higher above the flooding limit that usually occurred in conventional cases. Also they showed similar properties with a membrane contactor using hollow fibers as structured packing. A small height of transfer unit (HTU) of 3.6 cm and the overall transfer coefficient KG of 0.48 cm/s at the vapor velocity of 39.4 cm/s were obtained experimentally, which demonstrated a higher efficiency separating performance. The conversion of acetic acid reached 92% when DHFCMs with catalytic and separative properties were used as structured packing and without other catalysts in ethanol–acetic acid reactive distillation.
Co-reporter:Min Liu;Dong-Gen Chen;Yong-Ming Wei;Meng Tong
Journal of Applied Polymer Science 2013 Volume 128( Issue 1) pp:836-844
Publication Date(Web):
DOI:10.1002/app.38234
Abstract
The effects of nucleating agents on the morphology and performance of poly(vinylidene fluoride) (PVDF) microporous membranes via thermally induced phase separation were investigated. The nucleating agents studied were dicyclohexyl benzene amide (TMB-5), 2,2-methylene bis(4,6-tertiary butyl phenol) sodium phosphate (TMP-1), and 1,3 : 2,4-di-p-methylbenzylidene sorbitol (DM–LO). Light transmittance experiments and differential scanning calorimetry (DSC) were performed to obtain phase diagrams of PVDF/tributyl citrate/di(2-ethylhexyl) phthalate/nucleating agent doped solutions. The morphology and performance of the prepared PVDF microporous membranes were characterized with scanning electron microscopy and microfiltration experiments. The results show that the thermodynamics of liquid–liquid phase separation were not affected by the addition of the nucleating agents, but solid–liquid phase separation was influenced. The system with 0.3 wt % TMB-5 had the fastest crystallization rate and a better nucleation ability. The PVDF microporous membranes had a partly closed, lacy bicontinuous structure with TMP-1 and DM–LO, whereas the membrane with 0.3 wt % TMB-5 had an interconnected bicontinuous structure. The pore size distribution became narrower with the addition of nucleating agent. With 0.3 wt % TMB-5, the membrane had the minimum mean pore size (0.095 μm), a porosity of 80.3%, and a pure water flux of 270 L·m−2·h−1; these values were higher than those of the pure PVDF membrane. The performances of the membranes decreased with additions of TMB-5 of greater than 0.3 wt %. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Deng Hu, Zhen-Liang Xu, Yong-Ming Wei
Separation and Purification Technology 2013 110() pp: 31-38
Publication Date(Web):
DOI:10.1016/j.seppur.2013.03.001
Co-reporter:Xiao-Hua Ma, Xin Wen, Si-Wen Gu, Zhen-Liang Xu, Jin-Long Zhang
Journal of Membrane Science 2013 430() pp: 62-69
Publication Date(Web):
DOI:10.1016/j.memsci.2012.11.073
Co-reporter:De Sun;Bing-Bing Li
Korean Journal of Chemical Engineering 2013 Volume 30( Issue 11) pp:2059-2067
Publication Date(Web):2013 November
DOI:10.1007/s11814-013-0147-z
Hydrophobic polydimethylsiloxane — polytetrafluoroethylene (PDMS-PTFE) flat-sheet membranes for pervaporation (PV) of chloroform from aqueous solution were successfully fabricated by solution casting method. The structures and the performance of the membranes was characterized by X-ray diffraction (XRD), scanning electron microscope combined with energy dispersive X-ray spectroscopy (SEM-EDXS), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and the tests of contact angle and mechanical properties. The adding of PTFE particles (<4 μm) in the PDMS matrix enhanced the crystallinity, hydrophobicity, mechanical strength and thermal stability of the membranes. The examinations showed that the PTFE filled PDMS membranes exhibited striking advantages in flux and separation factor as compared with unfilled PDMS membranes. All the filled PDMS membranes with different PTFE content showed excellent PV properties for the separation of chloroform from water. When the content of the PTFE additive in PDMS composite membrane was 30 wt%, membrane performance was the best at feed temperature 50 °C and permeate-side vacuum 0.101MPa. For the 30% PTFE-PDMS membrane, with the increase of the feed temperature from 30 to 60 °C, the total, water and chloroform fluxes as well as the separation factor increased, the apparent activation energy (ΔEa) of total, chloroform and water were 21.08, 66.65 and 11.49 KJ/mol, respectively, with an increase of chloroform concentration in the feed from 50 to 950 ppm, total, water and chloroform fluxes increased but the separation factor decreased.
Co-reporter:Ping-Yun Zhang;Hu Yang;Yong-Ming Wei
Journal of Polymer Research 2013 Volume 20( Issue 2) pp:
Publication Date(Web):2013 February
DOI:10.1007/s10965-012-0066-4
Poly(vinylidene fluoride) (PVDF) membranes possessing interconnected bicontinuous structures with superior mechanical properties and improved hydrophilicity were obtained from PVDF/N,N-dimethylacetamide (DMAc)/Tween 80/water systems via non-solvent induced phase separation (NIPS) with 60 °C and ambient temperature casting solution. Tween 80/H2O mixtures were adopted as dopant; water/ethanol (50:50, mass ratio) and ethanol were chosen as coagulants. The effects of process parameters in terms of variations in dopant contents, casting solution temperatures, and coagulant compositions on the phase inversion process and performance of the resultant membranes were investigated. During the demixing process, water diffused from the interior of Tween 80 reverse micelles, resulting in an accelerated precipitation rate and surface segregation process of the polar head groups of Tween 80. The high temperature of the casting solution contributed to enhancing the diffusion rate of liquid–liquid demixing on crystallization. The coagulant compositions changed the liquid–liquid and solid–liquid demixing dynamics of the casting solutions. Ethanol coagulant contributed to crystallization of PVDF/DMAc/Tween 80/water systems prior to liquid–liquid demixing. This delayed demixing process favored the formation of porous foliage-type top structures with fibril or lath bicontinuous fine structure of membrane bulk, increasing flux, and significant hydrophilicity improvement. Casting solutions in water/ethanol coagulant exhibited a less delayed demixing process with both liquid–liquid demixing and crystallization, resulting in formation of fine structure in the form of strings or stripes and limited hydrophilicity improvement. The predominant typical α- and β-type crystallinity in PVDF was attributed to the existence of dopants, the high temperature of the casting solution, and water/ethanol coagulant. This was consistent with the superior mechanical properties of the corresponding PVDF membrane. The newly developed hydrophilic PVDF membranes with superior mechanical properties and low-fouling of bovine serum albumin (BSA) are anticipated to be suitable not only for wastewater treatment, but also for bioseparation.
Co-reporter:Xiao-Hua Ma;Si-Wen Gu;Xin Wen
Journal of Polymer Research 2013 Volume 20( Issue 6) pp:
Publication Date(Web):2013 June
DOI:10.1007/s10965-013-0155-z
The electrospinning of sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) and its blend with polyether sulfone (PES) were investigated and the blend nanofibers were applied as a catalyst in esterification. Attempts to electrospin pure SPPESK resulted in electrospraying rather than electrospinning. However, a blend polymer solution of SPPESK and PES resulted in smooth electrospinning when SPPESK content was lower than 9 wt%. The geometrical properties such as fiber diameter and distribution, surface chemical properties such as inter-molecular interaction and crystalline, mechanical properties were investigated by SEM, FTIR, XRD, etc. The catalytic activities of SPPESK-PES nanofibers were measured by esterification of ethanol with acetic acid. A pseudo-homogeneous model was established to describe the kinetics of esterification with nanofiber as a catalyst. The results showed that the SPPESK-PES blend nanofiber had a high specific surface area (46.7–58.9 m2/g), good mechanical properties, good catalytic properties (ethanol conversion up to 80 % when reacted 8 h), and good forward rate constants (10.0 × 10−3–14.6 × 10−3 L/(mol∙min)).
Co-reporter:Pei-Pei Lu, Zhen-Liang Xu, Hu Yang, and Yong-Ming Wei
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 3) pp:1716
Publication Date(Web):March 7, 2012
DOI:10.1021/am201843y
Polyethersulfone (PES)/perfluorosulfonic acid (PFSA) nanofiber membranes were successfully fabricated via electrospinning method from polymer solutions containing dispersed calcium carbonate (CaCO3) nanoparticles. ATR-FTIR spectra indicated that the nanoparticles mainly existed on the external surface of the nanofibers and could be removed completely by acid treatment. Surface roughness of both the nanofibers and the nanofiber membranes increased with the CaCO3 loading. Although FTIR spectra showed no special interaction between sulfonic acid (−SO3) groups and CaCO3 nanoparticles, XPS measurement demonstrated that the content of −SO3 groups on external surface of the acid-treated nanofibers was enhanced by increasing CaCO3 loading in solution. Besides, the acid-treated nanofiber membranes were performed in esterification reactions, and exhibited acceptable catalytic performance due to the activity of −SO3H groups on the nanofiber surface. More importantly, this type of membrane was very easy to separate and recover, which made it a potential substitution for traditional liquid acid catalysts.Keywords: CaCO3 nanoparticle; catalytic activity; electrospinning; nanofiber; perfluorosulfonic acid; polyethersulfone;
Co-reporter:Ping-Yun Zhang, Hu Yang, and Zhen-Liang Xu
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 11) pp:4388-4396
Publication Date(Web):February 28, 2012
DOI:10.1021/ie201806v
Polyvinylidene fluoride (PVDF) membranes were fabricated by the nonsolvent induced phase separation (NIPS) process using Tween 80 and H2O as a mixture additive from both 60 °C and room-temperature (RT) casting solution. Resultant PVDF membranes revealed improved pure water flux (PWF), enlarged mechanical properties, and well Bovine serum albumin (BSA) and Dextran rejection as a result of addition of water into the PVDF–DMAc–Tween 80 system. The improved performance was attributed to the existence of nonsolvent, which was solubilized by polar head groups of Tween 80 reverse micelle to form the water pool. Further, the interaction between polar head of surfactant and water provided a balance resistance to the interconnection between PVDF and hydrophobic chains of surfactant, which enhanced the thermodynamics stability of casting solution. During demixing process, water diffusion from the interior of casting solution, increased the precipitation rate and led to the insufficient crystallization process of polymer. Finally, the Tween 80 reverse micelle confined the movement of water in solution, making the fingerlike structure slim and confined, with the wall structure between macrovoids.
Co-reporter:Pei-Pei Lu, Zhen-Liang Xu, Hu Yang, and Yong-Ming Wei
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 35) pp:11348
Publication Date(Web):August 13, 2012
DOI:10.1021/ie300938u
Polymer nanofiber-supported perfluorosulfonic acid (PFSA)/SiO2 catalysts are successfully fabricated by electrospinning method from polymer/nanoparticle suspensions. This kind of catalyst has a large number of active acid sites and high specific surface area up to 85.6 m2/g. Scanning electron microscope images reveal that the catalysts present high porosity and inner-connected porous structure which varies much with SiO2 loading. Nitrogen adsorption–desorption measurements demonstrate a wide distribution of pore sizes inside the composites. Catalysts of different compositions are evaluated in esterification in a batch reactor under various conditions, and the results indicate that those of 20 wt % PFSA loading have the best activity of unit PFSA. Supporting PFSA by a nanofibrous matrix enhances liquid holdups inside the catalysts and offers accessibility of the acid sites, and therefore improves the activity of the catalysts. Moreover, these catalysts allow recovery at high percentages and regeneration with high activity.
Co-reporter:Pei-Pei Lu;Hu Yang;Yong-Ming Wei
Journal of Polymer Research 2012 Volume 19( Issue 4) pp:
Publication Date(Web):2012 April
DOI:10.1007/s10965-012-9854-0
Blend solutions of polyethersulfone (PES) and perfluorosulfonic acid (PFSA) resin were fabricated into nanofibers via electrospinning. Ethanol (EtOH) and isopropanol (IPA) were employed to investigate the effects of non-solvent (NS) on the structures and properties of the electrospun PES/PFSA nanofibers. Average diameters of the electrospun nanofibers increased with NS content while the water contact angles of the nanofiber membranes decreased. Although all the nanofiber membranes presented strong hydrophobicity initially, the water contact angle would drop to less than 90° within 30 min. Energy dispersive X-ray spectrums (EDS) showed that the nanofibers electrospun from solutions with more NS presented higher sodium content on the surface because more -SO3Na groups were on the external plane. N2 adsorption-desorption measurement revealed that increase of NS content in the solvent mixtures resulted in nanofibers with surface area much bigger in experiment than that in calculation, which meant rough structures occurred on the surface of electrospun nanofibers. These rough structures were beneficial to improve the frictional resistance between nanofibers and therefore enhanced the break strength and Young’s modulus of the nanofiber membranes.
Co-reporter:Xiao-Hua Ma;Fan Wu;Hai-Tao Xu
Iranian Polymer Journal 2012 Volume 21( Issue 1) pp:31-41
Publication Date(Web):2012 January
DOI:10.1007/s13726-011-0007-9
PFSA-TiO2(or Al2O3)-PVA/PVA/PAN difunctional hollow fiber composite membranes with separation performance and catalytic activity have been prepared by dip-coating method. The good separation performance was brought about by the glutaraldehyde (GA) surface cross-linked PVA/PAN composite membrane, and the good catalytic activity of the membrane was achieved by the perfluorosulphonic acid (PFSA) used. The difunctional hollow fiber membranes were characterized by XRD, TGA, EDX, SEM, and FTIR. The separation performance was measured by dehydration of azeotropic top product of ethanol-acetic acid esterification, and the catalytic activity was obtained by investigating the esterification of ethanol and acetic acid. The FTIR spectra and the morphologies of difunctional hollow fiber composite membranes were similar for samples prior to esterification and post-esterification with ethanol and acetic acid for 24 h. Difunctional hollow fiber composite membranes with 2% PFSA, 8% TiO2 (named as DM-T1), and 2% PFSA, 8% Al2O3 (named as DM-A1) (all by weights) showed the best catalytic activity. They displayed fluxes of 165 and 173 g/m2 h, separation factors of water to ethanol of 279 and 161, PFSA contents in difunctional hollow fiber composite membrane of 3.2 and 2.4%, the ratios of PFSA to feed solution (acetic acid–ethanol) of 0.031 and 0.023%, and the equilibrium conversion of ethanol at 53.5 and 57.6%, in the given order for TiO2 and Al2O3 containing samples.
Co-reporter:Xiao-Hua Ma;Chao-Qing Ji;Yong-Ming Wei;Hu Yang
Journal of Applied Polymer Science 2011 Volume 120( Issue 2) pp:1017-1026
Publication Date(Web):
DOI:10.1002/app.33216
Abstract
Polyelectrolyte complex membranes (PCMs) were prepared using sodium tripolyphosphate (STPP) solution surface-crosslinking chitosan/polyacrylonitrile (PAN) composite membranes. Fourier transform infrared (FTIR) was used to characterize the surface-crosslinking. The effects of different surface-crosslinking time on morphologies, element distribution, and crystal structures were investigated by scanning electron microscopy (SEM), energy dispersion of X-ray (EDX), and X-ray diffraction (XRD). The effect of crosslinking ratio on swelling ratio was analyzed. The separation performances of PCMs in terms of permeation flux and separation factor were measured by dehydrating ethyl acetate aqueous solutions. A kinetic model of crosslinking reaction was proposed to investigate the effect of crosslinking agent concentration and surface-crosslinking time on the crosslinking ratio of PCMs. It was found that the membrane possessed the excellent performance when surface crosslinked for 15 min. The permeation flux and separation factor were 336 g/(m2 h) and 6270 in 97 wt % ethyl acetate aqueous solution at 313 K. The crosslinking ratio of PCM exponentially increased as time increased, while linearly increased as concentration and diffusion coefficient of crosslinking agent STPP solution increased. And the effect of crosslinking agent concentration on crosslinking ratio was inversely proportional to surface-crosslinking time. The experimental results matched well with the kinetic model when STPP concentration was lower than 5 wt %. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Qian Li;Min Liu
Polymers for Advanced Technologies 2011 Volume 22( Issue 5) pp:520-531
Publication Date(Web):
DOI:10.1002/pat.1549
Abstract
Using the mixture of triethyl phosphate (TEP) and N,N-dimethylacetamide (DMAc) as solvent, PVDF microporous membranes with highly hydrophobic surface were prepared by a modified NIPS method with a dual coagulation process. The effects of the exposure time on these membranes before being immersed into the coagulation bath and the composition in the coagulation bath on precipitation rate, membrane morphology, membrane hydrophobicity, membrane mechanical property, and membrane performance were studied. The morphologies and hydrophobicities of PVDF microporous membranes were investigated by scanning electron microscopy (SEM) and contact angle (CA) measurement. The precipitation processes were observed by light transmittance measurement. The pore size distribution was determined by liquid permeation technique. PVDF microporous membrane obtained by passing evaporation period of 60 min before being immersed into the water bath showed a high water CA of 122.1°. Using ethanol (EtOH) as coagulation bath, the water CAs of the top surface and bottom surface of the membrane increased to 125.9 and 132.6°, respectively. To further improve PVDF membrane hydrophobicity, a dual coagulation process was used and the mixed solvent (TEP–DMAc) was added into the first coagulation bath for 30 sec. Increase in the TEP–DMAc content led to the change in the morphology type of the membrane, that is, from an asymmetric structure with a dense top surface to a symmetric structure with a skinless top surface, and the pore size distribution widened greatly. By increasing the mass ratio of TEP to DMAc, the denseness of the membrane surface decreased significantly. Adding 60 wt% of TEP–DMAc to the first coagulation bath and the mass ratio of TEP to DMAc was 60:40, the CA reached to a maximum as high as 136.6°, and PVDF microporous membrane showed a high porosity of 80% and an excellent mechanical property of 3.14 MPa tensile strength and 61.79% elongation ratio. Copyright © 2009 John Wiley & Sons, Ltd.
Co-reporter:Ling-Feng Han, Zhen-Liang Xu, Yue Cao, Yong-Ming Wei, Hai-Tao Xu
Journal of Membrane Science 2011 372(1–2) pp: 154-164
Publication Date(Web):
DOI:10.1016/j.memsci.2011.01.065
Co-reporter:Qian Li;Li-Yun Yu
Journal of Applied Polymer Science 2010 Volume 115( Issue 4) pp:2277-2287
Publication Date(Web):
DOI:10.1002/app.31324
Abstract
Polyvinylidene fluoride (PVDF) microporous flat membranes were cast with different kinds of PVDFs and four mixed solvents [trimethyl phosphate (TMP)–N,N-dimethylacetamide (DMAc), triethyl phosphate (TEP)–DMAc, tricresyl phosphate (TCP)–DMAc, and tri-n-butyl phosphate (TBP)–DMAc]. The effects of different commercial PVDFs (Solef® 1015, FR 904, Kynar 761, Kynar 741, Kynar 2801) on membrane morphologies and membrane performances of PVDF/TEP–DMAc/PEG200 system were investigated. The membrane morphologies were examined by scanning electron microscopy (SEM). The membrane performances in terms of pure water flux, rejection, porosity, and mean pore radius were measured. The membrane had the high flux of 143.0 ± 0.9 L m−2 h−1 when the content of TMP in the TMP–DMAc mixed solvent reached 60 wt %, which was 2.89 times that of the membrane cast with DMAc as single solvent and was 3.36 times that of the membrane cast with TMP as single solvent. Using mixed solvent with different solvent solubility parameters, different morphologies of PVDF microporous membranes were obtained. TMP–DMAc mixed solvent and TEP–DMAc mixed solvent indicated the stronger solvent power to PVDF due to the lower solubility parameter difference of 1.45 MPa1/2 and the prepared membranes showed the faster precipitation rate and the higher flux. The less macrovoids of the membrane prepared with TEP (60 wt %)–DMAc (40 wt %) as mixed solvent contributed to the higher elongation ratio of 96.61% ± 0.41%. Therefore, using TEP(60 wt %)–DMAc (40 wt %) as mixed solvent, the casting solution had the better solvent power to PVDF, and the membrane possessed the excellent mechanical property. The microporous membranes prepared from casting solutions with different commercial PVDFs exhibited similar morphology, but the water flux increased with the increment of polymer solution viscosity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Li-Yun Yu, Zhen-Liang Xu, Hong-Mei Shen, Hu Yang
Journal of Membrane Science 2009 Volume 337(1–2) pp:257-265
Publication Date(Web):15 July 2009
DOI:10.1016/j.memsci.2009.03.054
Organic–inorganic polyvinylidene fluoride (PVDF)–silica (SiO2) composite hollow fiber ultrafiltration (UF) membranes were prepared by the combination of a tetraethoxysilane (TEOS) sol–gel process with a wet-spinning method. The membrane formation mechanisms were investigated in terms of viscosity, precipitation kinetics and morphology. Results showed the dope viscosity increased with the increment of TEOS concentration in dope. The addition of TEOS accelerated the precipitation of the dope. SEM pictures showed the cross-section morphology of PVDF composite membranes changed from finger-like macrovoids to sponge-like structure with increasing SiO2 content. The mechanical, thermal stabilities and permeation property of PVDF–SiO2 composite membranes were further examined. At lower TEOS concentration, the hydrolyzed SiO2 particles, which were homogeneously dispersed in PVDF matrix, acted as the physical crosslinking points, and led to an improvement of mechanical and thermal properties. While at higher TEOS concentration, SiO2 formed network, which restricted the movement of PVDF and led to the decrease of the mechanical and thermal stabilities. Moreover, XRD and FTIR results revealed that the crystal structure of PVDF underwent a transition from α-phase to β-phase due to the addition of TEOS. The contact angle and UF experimental results of PVDF–SiO2 composite membranes showed an improvement of hydrophilicity and permeability. The PVDF–SiO2 membrane prepared from the dope with 3 wt.% TEOS concentration had the best UF performance and antifouling property.
Co-reporter:Jing-Yu Wang, Zhen-Liang Xu, Ping Wu, Shen-Jun Yin
Journal of Membrane Science 2009 Volume 331(1–2) pp:84-90
Publication Date(Web):1 April 2009
DOI:10.1016/j.memsci.2009.01.016
Molecularly imprinted composite membranes for selective binding and permeation of S-Naproxen (S-Nap) were synthesized using the copolymerization method with 4-vinyl-pyridine (4-VPy) as functional monomers and ethylene glycol dimethacrylate (EDMA) as cross-linkers. The characterization results showed that, the binding constant (K) for the formation of monomer–template adduct was 13.8 M−1 by means of infrared spectroscopy and nonlinear least-squares method. And the scanning electron microscope was used to visualize surface and cross-sections of membranes to gain better understanding in the analysis of imprinted layer deposited on PVDF support membranes. The separation property of the imprinted membrane was determined by on-line HPLC membrane separation technology. The separation mechanism of the S-Nap imprinted membrane could be defined as facilitated permeation mechanism.
Co-reporter:Guo-Lin Yuan, Zhen-Liang Xu, Yong-Ming Wei
Separation and Purification Technology 2009 Volume 69(Issue 2) pp:141-148
Publication Date(Web):30 September 2009
DOI:10.1016/j.seppur.2009.07.011
Polyvinylidene fluoride (PVDF)–perfluorosulfonic acid (PFSA) hollow fiber ultrafiltration blend membranes were prepared by wet-spinning method. The effects of PVDF–PFSA and ethanol concentrations on the structure morphology and performance of blend membranes were investigated. The coagulation kinetics was studied by light transmittance experiments. Blend membranes were characterized in terms of morphology, pore size distribution, molecular weight cut-off, water permeation flux and rejection. The wetting and fouling properties of blend membranes were also examined. Based on the experimental results, more sponge-like structures existed in the cross section of the blend membrane prepared from the dope solution with the increase in PVDF concentration, but the membrane showed a worse permeation performance. The increase of PFSA resulted in the formation and development of the finger-like voids. It was also found that the finger-like macrovoids began growing up inside the nascent membrane. Such changes were proved by scanning electron microscopy (SEM). By introducing different concentrations of ethanol from 1 to 5 wt.% in PVDF–PFSA dope solution, thinner and more uniform finger-like voids appeared through the cross section, the pure water permeation flux, the mean effective pore size, molecular weight cut-off were increased. PVDF–PFSA hollow fiber UF blend membranes with low-molecular weight cut-off around 10,000 Da were obtained and the morphology was elaborately controlled.
Co-reporter:Jing-Feng Li, Zhen-Liang Xu, Hu Yang, Li-Yun Yu, Min Liu
Applied Surface Science 2009 Volume 255(Issue 9) pp:4725-4732
Publication Date(Web):15 February 2009
DOI:10.1016/j.apsusc.2008.07.139
Abstract
PES–TiO2 composite membranes were prepared via phase inversion by dispersing TiO2 nanopaticles in PES casting solutions. The crystal structure, thermal stability, morphology, hydrophilicity, permeation performance, and mechanical properties of the composite membranes were characterized in detail. XRD, DSC and TGA results showed that the interaction existed between TiO2 nanopaticles and PES and the thermal stability of the composite membrane had been improved by the addition of TiO2 nanopaticles. As shown in the SEM images, the composite membrane had a top surface with high porosity at low loading amount of TiO2, which was caused by the mass transfer acceleration in exposure time due to the addition of TiO2 nanopaticles. At high loading amount of TiO2, the skinlayer became much looser for a significant aggregation of TiO2 nanopaticles, which could be observed in the composite membranes. EDX analysis also revealed that the nanoparticles distributed in membrane more uniformly at low loading amount. Dynamic contact angles indicated that the hydrophilicity of the composite membranes was enhanced by the addition of TiO2 nanopaticles. The permeation properties of the composite membranes were significantly superior to the pure PES membrane and the mean pore size also increased with the addition amount of TiO2 nanopaticles increased. When the TiO2 content was 4%, the flux reached the maximum at 3711 L m−2 h−1, about 29.3% higher than that of the pure PES membrane. Mechanical test also revealed that the mechanical strength of composite membranes enhanced as the addition of TiO2 nanopaticles.
Co-reporter:Li-Yun Yu;Hong-Mei Shen
Journal of Applied Polymer Science 2009 Volume 113( Issue 3) pp:1763-1772
Publication Date(Web):
DOI:10.1002/app.29886
Abstract
Organic–inorganic polyvinylidene fluoride (PVDF)–titanium dioxide (TiO2) composite hollow fiber ultrafiltration (UF) membranes were prepared by TiO2 sol–gel method and blending method, respectively. The membranes were characterized in terms of microstructure, hydrophilicity, permeation performance, thermal stability, and mechanical strength. The experimental results indicated that PVDF–TiO2 composite UF membranes exhibited significant differences in surface properties and intrinsic properties because of the addition of inorganic particles. The TiO2 particles improved the membrane strength and thermal stability of PVDF–TiO2 composite UF membranes. In particular, hydrophilicity and permeability increased dramatically with the increase of TiO2, whereas the retention property of UF membranes was nearly unchanged. However, high TiO2 concentration induced the aggregation of particles, resulting in the decline of hydrophilicity and permeability. Compared with PVDF–TiO2 composite hollow fiber UF membranes prepared by TiO2 blending method, PVDF–TiO2 composite hollow fiber UF membranes prepared by TiO2 sol–gel method formed a dispersed inorganic network, and the stronger interaction between inorganic network and polymeric chains led to TiO2 particles being uniformly dispersed in UF membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Zhen-liang Xu;Li-yun Yu;Ling-feng Han
Frontiers of Chemical Science and Engineering 2009 Volume 3( Issue 3) pp:318-329
Publication Date(Web):2009 September
DOI:10.1007/s11705-009-0199-0
Polymer-nanoinorganic particles composite membranes present an interesting approach for improving the physical and chemical, as well as separation properties of polymer membranes, because they possess characteristics of both organic and inorganic membranes such as good permeability, selectivity, mechanical strength, thermal stability and so on. The preparations and structures of polymer-nanoinorganic particles composite membranes and their unique properties are reviewed.
Co-reporter:Xue-Jun Wang, Zhen-Liang Xu, Jian-Li Feng, Nai-Ci Bing, Zuo-Guo Yang
Journal of Membrane Science 2008 Volume 313(1–2) pp:97-105
Publication Date(Web):10 April 2008
DOI:10.1016/j.memsci.2007.12.067
Molecularly imprinted composite membrane for selective binding and permeation of lovastatin acid from aqueous solutions was developed by means of target analogue imprinting strategy. To improve mechanical stability of the membrane, polyvinylidene fluoride (PVDF) ultrafiltration membrane was used as support. The thin imprinted layer was formed by copolymerization of methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linker in the presence of lovastatin as dummy template in acetonitrile solution. The attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscope (SEM) were used to visualize surface and cross-sections of membranes to gain better understanding in the analysis of imprinted layer deposited on PVDF support membranes. The modification degrees are 2.28 and 2.40 mg/cm2 for imprinted and non-imprinted membranes, respectively, and the saturated binding capacity of imprinted membrane is about 0.25 μmol/cm2, nearly 10 times of that of non-imprinted one. The permeation performances of membranes were evaluated through kinetic filtration experiments. It was found that the diffusive selectivity of imprinted membrane could be adjusted by varying the pH of the feed solutions and operation pressure of the filtration system. The transport selectivity shown at higher pH value should be attributed to not only the electrostatic interactions and/or hydrogen bonding between the permeants and membranes but also to hydrophobic effect between permeants and aqueous medium.
Co-reporter:Jing-Feng Li;Hu Yang
Polymers for Advanced Technologies 2008 Volume 19( Issue 4) pp:251-257
Publication Date(Web):
DOI:10.1002/pat.982
Abstract
Using diethylene glycol (DegOH) as non-solvent additive (NSA) and N, N-dimethylacetamide (DMAc) as solvent (S), polyethersulfone (PES) flat sheet membranes were prepared via immersion precipitation combined with the vapor induced phase separation (VIPS) process. Light transmittance was used to follow the precipitation rate during the immersion process as well as during the VIPS stage. As the addition of the NSA, the viscosity of casting solutions increased, which led to a slow precipitation rate. Though the precipitation rate decreased, the instantaneous demixing type was maintained. High flux membranes were obtained only at a high mass ratio of NSA/S; producing membranes had cellular pores on the top surface and sponge-like structure on cross section. The VIPS process prior to immersion precipitation was important for the formation of cellular pore on the surface. With the increase in exposure time, the liquid–liquid phase separation took place on the surface of casting solution; nucleation and growth induced the formation of cellular pore on the top surface. Coagulation bath temperature also had large effect on the precipitation rate; high temperature on coagulation bath mainly accelerated the transfer of solvent and non-solvent. Higher flux membrane with a porous skin layer could be obtained at a high coagulation bath temperature, but at the same time the mechanism properties were weakened. Copyright © 2007 John Wiley & Sons, Ltd.
Co-reporter:Jing-Feng Li;Hu Yang;Cui-Ping Feng ;Jiang-Huan Shi
Journal of Applied Polymer Science 2008 Volume 107( Issue 6) pp:4100-4108
Publication Date(Web):
DOI:10.1002/app.27626
Abstract
Microporous poly(ether sulfones) (PES) membranes were prepared via phase inversion using poly (ethylene glycol) (PEG) as additive and N,N-dimethylacetamide (DMAc) as solvent. Thermodynamic of the casting solutions was studied by coagulation value while precipitation rate was observed by light transmittance measurement. It was found that casting solution with PEG200 as additive was thermodynamically less stable than those with PEG400 and PEG600 as additive and easier to cause phase separation in exposure time. With the increase of PEG200 concentration, the casting solution became thermodynamically less stable and easier to cause phase separation in exposure time, but precipitation rate during immersion precipitation decreased because of the increased viscosities. ATR-FTIR spectra and TGA curves showed that the membranes prepared using PEG200 as additive had less PEG residual than those of PEG400 and PEG600, but it showed better permeation performance than that prepared using PEG400 and PEG600 as additive. With the increase of PEG200 concentration from 30 to 70 wt %, the cross section structure changed from macrovoid to sponge-like, micropores with a mean pore size around 0.1 μm began to form on the top surface. When the PEG200 concentration is 60 wt %, the pure water flux was 1845 L m−2 h−1 bar−1, which is the highest value. As the PEG200 concentration increased from 30 to 60 wt %, the contact angles decreased from 82.1° to 58.2°. As the addition amount of PEG200 increased, the residual PEG made the prepared membranes more hydrophilic. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Wan-Zhong Lang;Wei Tong
Journal of Applied Polymer Science 2008 Volume 108( Issue 1) pp:370-379
Publication Date(Web):
DOI:10.1002/app.26794
Abstract
Using Na+ form of perfluorosulfonic acid (PFSA) and poly(vinyl alcohol) (PVA) as coating materials, polysulfone (PSf) hollow fiber ultrafiltration membrane as a substrate membrane, PFSA-PVA/PSf hollow fiber composite membrane was fabricated by dip-coating method. The membranes were post-treated by two methods of heat treatment and by both heat treatment and chemical crosslinking. Maleic anhydride (MAC) aqueous solution was used as chemical crosslinking agent using 0.5 wt % H2SO4 as a catalyst. PFSA-PVA/PSf hollow fiber composite membranes were used for the pervaporation (PV) separation of isopropanol (IPA)/H2O mixture. Based on the experimental results, PFSA-PVA/PSf hollow fiber composite membrane is suitable for the PV dehydration of IPA/H2O solution. With the increment of heat treatment temperature, the separation factor increased and the total permeation flux decreased. The addition of PVA in PFSA-PVA coating solution was favorable for the improvement of the separation factor of the composite membranes post-treated by heat treatment. Compared with the membranes by heat treatment, the separation factors of the composite membranes post-treated by both heat treatment and chemical crosslinking were evidently improved and reached to be about 520 for 95/5 IPA/water. The membranes post-treated by heat had some cracks which disappeared after chemical crosslinking for a proper time. Effects of feed temperature on PV performance had some differences for the membranes with different composition of coating layer. The composite membranes with the higher mass fraction of PVA in PFSA-PVA coating solution were more sensitive to temperature. It was concluded that the proper preparation conditions for the composite membranes were as follows: firstly, heated at 160°C for 1 h, then chemical crosslinking at 40°C for 3 h in 4% MAC aqueous solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Xue-Jun Wang;Nai-Ci Bing;Zuo-Guo Yang
Journal of Applied Polymer Science 2008 Volume 109( Issue 1) pp:64-73
Publication Date(Web):
DOI:10.1002/app.26805
Abstract
Using nickel-2,2′-dipyridyl complex as a template, N-vinyl-2-pyrrolidone as the metal coordination functional monomer, and ethylene glycol dimethacrylate as the crosslinker, polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membrane as the supported membrane, metal complex imprinted polymeric membranes were prepared. The association constant of template-monomer interaction in the prepolymerization solution was estimated to be 4.38 × 104 (L/mol)2 by spectrophotometric titration analysis. The attenuated total reflection Fourier transform infrared spectroscopy and scanning electron micrograph characterization indicated that the surface of the support PVDF membrane was completely coated by the imprinted polymer layer after modification. The imprinted membranes exhibited the selective permeability for the template in certain nickel acetate solution. The molecularly imprinted membranes gave higher permeation separation factors at about pH 6, whereas increasing pressure would lower the separation ability. The effects of ion concentration, cations and counterions, ligand selectivity, pH, and trans-membrane pressure were investigated and the permeation performances of the imprinted membranes could be regarded as facilitated transport mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Hai-Kuan Yuan;Jiang-Huan Shi;Xiao-Hua Ma
Journal of Applied Polymer Science 2008 Volume 109( Issue 6) pp:4025-4035
Publication Date(Web):
DOI:10.1002/app.28500
Abstract
Preparation of organic-inorganic composite membranes and their pervaporation (PV) permeation and separation characteristics for the aqueous solution of ethyl acetate were described. Polyacrylonitrile (PAN) hollow fiber ultrafiltration membrane as support membrane, the mixtures of perfluorosulfonic acid (PFSA) and tetraethoxysilane (TEOS) by the sol-gel reaction as the coating solution, the PFSA-TEOS/PAN hollow fiber composite membranes by the different annealing conditions were prepared. The swelling of PFSA in ethyl acetate aqueous solutions was inhibited with addition of TEOS. The PFSA-TEOS/PAN composite membranes containing up to 30 wt % TEOS in coating solution exhibited high selectivity towards water, then the selectivity decreased and permeation flux increased with increasing the TEOS concentration more than 30 wt %. When the PFSA-TEOS/PAN composite membranes were annealed, the separation factor increased with increasing annealing temperature and time. Higher annealing temperature and longer annealing time promoted the crosslinking reaction between PFSA and TEOS in PFSA-TEOS/PAN composite membranes, leading to the enhanced selectivity towards water. For the PFSA/PAN and PFSA-TEOS/PAN composite membrane with 5 and 30 wt % TEOS annealed at 90°C for 12 h, their PV performance of aqueous solution 98 wt % ethyl acetate were as follows: the separation factors were 30.8, 254 and 496, while their permeation flux were 1430, 513 and 205 g/m2 h at 40°C, respectively. In addition, the PV performance of PFSA-TEOS/PAN composite membranes was investigated at different feed solution temperature and concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Kai Wu 吴凯 许振良
Journal of Shanghai University (English Edition) 2008 Volume 12( Issue 2) pp:163-170
Publication Date(Web):2008 April
DOI:10.1007/s11741-008-0215-1
Using polysulfone (PSF) hollow fiber ultrafiltration membranes as the substrate, sodium alginate (SA) and polyvinyl alcohol (PVA) blend solutions as the coating solution, and maleic anhydride (MAC) as the cross-linked agent, SAPVA/PSF hollow fiber composite membranes were prepared for the dehydration of ethanol-water. The effects of different sodium alginate concentration in the coating solutions and different operating temperatures on pervaporation performance were investigated. The experimental results showed that pervaporation performance of the SA-PVA/PSF composite membranes for ethanol-water solution exhibited a high separation factor although they had a relatively low permeation flux. As SA concentration in SA-PVA coating solution was 66.7% and the operating temperature was 40 °C, SA-PVA/PSF hollow fiber composite membrane (PS4) had a separation factor of 886 and flux of 12.6 g/(m2·h). Besides, SA-PVA/PSF hollow fiber composite membranes (PS3 and PS4) were used for the investigation of the effect of ethanol concentration in the feed solution on pervaporation performance.
Co-reporter:Wan-Zhong Lang, Zhen-Liang Xu, Hu Yang, Wei Tong
Journal of Membrane Science 2007 Volume 288(1–2) pp:123-131
Publication Date(Web):1 February 2007
DOI:10.1016/j.memsci.2006.11.009
Polyvinylidene fluoride (PVDF)–perfluorosulfonic acid (PFSA) blend hollow fiber ultrafiltration (UF) membranes were prepared by wet-spinning method using pure water as an external coagulation solution. Coagulation kinetics of PVDF–PFSA–DMAc system was measured by light transmittance experiment. Using PEG10000 (Mw = 10,000), lysozyme (Mw = 14,400), PEG20000 (Mw = 20,000) and BSA (Mw = 67,000), the separation performances of PVDF–PFSA blend hollow fiber UF membranes were obtained. Based on the experimental results, the delayed demixing process was observed for the dope solution M-1 without PFSA-H while the instantaneous demixing process was observed for the others with PFSA-H in the dope solutions M-2 to M-6. The precipitation rate increased with the increment of the PFSA-H concentration in PVDF–PFSA dope solution. The bore fluid solution with 95:5 DMAc:H2O resulted in single finger-like voids for PVDF–PFSA-H UF membrane. The pure water permeation flux of PVDF–PFSA-H UF membranes firstly increased from <0.1 × 10−5 to 119.1 × 10−5 L m−2 h−1 Pa−1 (<0.1 to 119.1 L m−2 h−1 bar−1) for M-1 to M-4(1) and 137 × 10−5 L m−2 h−1 Pa−1 (137 L m−2 h−1 bar−1) for M-4(2), and decreased from 119.1 × 10−5 to 79 × 10−5 L m−2 h−1 Pa−1 (119.1 to 79 L m−2 h−1 bar−1) for M-4(1), M-5 and M-6 as the PFSA-H concentration changed from 0% to 5% and total PVDF–PFSA-H concentration was 20 wt.%. The molecular weight cut-off (MWCO) of PVDF–PFSA blend hollow fiber UF membranes spun from 20 wt.% PVDF–PFSA-H concentration with 3–5 wt.% PFSA-H was about 20,000 while that spun from 22 wt.% PVDF–PFSA-H or PVDF–PFSA-Na concentration with 5 wt.% PFSA-H or PFSA-Na was about 10,000. As the WPFSA-H/WPVDF increases from 2/18 to 5/15 for M-3–M-6, JBSA/Jw increases from 0.53 to 0.79. The anti-fouling property of PVDF–PFSA-H blend UF membrane is superior to PVDF–PFSA-Na blend membrane. Based on FTIR spectra, PFSA-H existed in PVDF–PFSA blend hollow fiber UF membranes. There is no obvious variation of the intensity of the characteristic peak at 983 cm−1 assigned to C–O–C group of PFSA-H molecules. This also illustrated that PVDF–PFSA-H blend hollow fiber UF membranes were stable.
Co-reporter:Nai-Ci Bing;Xue-Jun Wang;Zuo-Guo Yang;Hu Yang
Journal of Applied Polymer Science 2007 Volume 106(Issue 1) pp:71-76
Publication Date(Web):14 JUN 2007
DOI:10.1002/app.26428
Through the use of thermal polymerization, poly(vinylidene fluoride) (PVDF) hollow-fiber membranes modified by a thin layer of molecularly imprinted polymers (MIPs) were developed for the selective separation of levofloxacin. To demonstrate the changes induced by thermal polymerization, PVDF hollow-fiber membranes with different modification degrees by repeated polymerization were weighed. The total weight of the imprinted membranes increased by 14 μg/cm2 after a five-cycle polymerization. An increase in the membrane weight indicated the deposition of an MIP layer on the external surface of PVDF hollow-fiber membranes during each polymerization cycle, which was also characterized by scanning electron microscopy. MIP membranes with different degrees of surface modification provided highly selective binding of levofloxacin. Both hollow-fiber MIP membranes and nonimprinted membranes showed enhanced adsorption of levofloxacin and ofloxacin gradually with an increase in the modification degrees of PVDF hollow-fiber membranes to a maximum value followed by a decrease. These results indicate that thermal polymerization indeed produces an MIP layer on the external surface of PVDF hollow-fiber membranes and that it is feasible to control the permeability by repeated polymerization cycles. Different solvent systems in the permeation experiments were used to understand the hydrophobic interaction as one of the results of the binding specificity of MIP membranes. Selective separation was obtained by multisite binding to the template via ionic, hydrogen-bond, and hydrophobic interactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Xiao-Tian Yang;Yong-Ming Wei
Journal of Applied Polymer Science 2006 Volume 100(Issue 3) pp:2067-2074
Publication Date(Web):17 FEB 2006
DOI:10.1002/app.23020
In the steady fabricating process, two-dimensional hollow fiber membrane near the spinneret was numerically simulated using the finite element method (FEM). The unknown positions of free surface and moving interface were calculated simultaneously by the velocity and pressure fields. The effects of seven relevant parameters, i.e., inertia term, gravity term, dope flow rate, bore flow rate, dope viscosity, tensile force, end velocity and non-Newtonian on the velocity and diameter profile were studied. On the basis of the simulated results, the inertia term in hollow fiber-spinning process was safely neglected in low speed, while the effect of gravity was not be neglected. Besides, the outer diameter of the fibers increased with an increase of dope flow rate and bore flow rate; Large tensile force or large end velocity could cause large deformation in the air gap; larger viscous dope solution tended to make less deformation in the air gap. It was found that an increase of the dope flow rate at small dope flow rate resulted in an increase of the inner diameter, while at large dope flow rate, it decreased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2067–2074, 2006
Co-reporter:Zhen-Liang Xu;Yong-Ming Wei;Kai Wu;F. Alsalhy Qusay
Journal of Applied Polymer Science 2005 Volume 98(Issue 1) pp:247-254
Publication Date(Web):12 JUL 2005
DOI:10.1002/app.22131
Polysulfone (PSF) hollow fiber membranes were spun by phase-inversion method from 29 wt % solids of 29 : 65 : 6 PSF/NMP/glycerol and 29 : 64 : 7 PSF/DMAc/glycol using 93.5 : 6.5 NMP/water and 94.5 : 5.5 DMAc/water as bore fluids, respectively, while the external coagulant was water. Polyvinyl alcohol/polysulfone (PVA/PSF) hollow fiber composite membranes were prepared after PSF hollow fiber membranes were coated using different PVA aqueous solutions, which were composed of PVA, fatty alcohol polyoxyethylene ether (AEO9), maleic acid (MAC), and water. Two coating methods (dip coating and vacuum coating) and different heat treatments were discussed. The effects of hollow fiber membrane treatment methods, membrane structures, ethanol solution temperatures, and MAC/PVA ratios on the pervaporation performance of 95 wt % ethanol/water solution were studied. Using the vacuum-coating method, the suitable MAC/PVA ratio was 0.3 for the preparation of PVA/PSF hollow fiber composite membrane with the sponge-like membrane structure. Its pervaporation performance was as follows: separation factor (α) was 185 while permeation flux (J) was 30g/m2·h at 50°C. Based on the experimental results, it was found that separation factor (α) of PVA/PSF composite membrane with single finger-void membrane structure was higher than that with the sponge-like membrane structure. Therefore, single finger-void membrane structure as the supported membrane was more suitable than sponge-like membrane structure for the preparation of PVA/PSF hollow fiber composite membrane. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 247–254, 2005
Co-reporter:Zhen-Liang Xu;F. Alsalhy Qusay
Journal of Applied Polymer Science 2004 Volume 91(Issue 5) pp:3398-3407
Publication Date(Web):16 JAN 2004
DOI:10.1002/app.13580
Polyethersulfone (PES) hollow-fiber membranes were fabricated using poly(ethyleneglycol) (PEG) with different molecular weights (MW = PEG200, PEG600, PEG2000, PEG6000, and PEG10000) and poly(vinyl pyrrolidone) PVP40000 as additives and N-methyl-2-pyrrolidone (NMP) as a solvent. Asymmetric hollow-fiber membranes were spun by a wet phase-inversion method from 25 wt % solids of 20 : 5 : 75 (weight ratio) PES/PEG/NMP or 18 : 7 : 75 of PES/(PEG600 + PVP40000)/NMP solutions, whereas both the bore fluid and the external coagulant were water. Effects of PEG molecular weights and PEG600 concentrations in the dope solution on separation properties, morphology, and mechanical properties of PES hollow-fiber membranes were investigated. The membrane structures of PES hollow-fiber membranes including cross section, external surface, and internal surface were characterized by scanning electron microscopy and the mechanical properties of PES hollow-fiber membranes were discussed. Bovine serum albumin (BSA, MW 67,000), chicken egg albumin (CEA, MW 45,000), and lysozyme (MW 14,400) were used for the measurement of rejection. It was found that with an increase of PEG molecular weights from 200 to 10,000 in the dope solution, membrane structures were changed from double-layer fingerlike structure to voids in the shape of spheres or ellipsoids; moreover, there were crack phenomena on the internal surfaces and external surfaces of PES hollow-fiber membranes, pure water permeation fluxes increased from 22.0 to 64.0 L m−2 h−1 bar−1, rejections of three protein for PES/PEG hollow-fiber membranes were not significant, and changes in mechanical properties were decreased. Besides, with a decrease of PEG600 concentrations in the dope solution, permeation flux and elongation at break decreased, whereas the addition of PVP40000 in the dope solution resulted in more smooth surfaces (internal or external) of PES/(PEG600 + PVP40000) hollow-fiber membranes than those of PES/PEG hollow-fiber membranes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3398–3407, 2004
Co-reporter:Deng Hu, Zhen-Liang Xu, Chang Chen
Desalination (3 September 2012) Volume 301() pp:75-81
Publication Date(Web):3 September 2012
DOI:10.1016/j.desal.2012.06.015
Silica/polypiperazine-amide nanofiltration (NF) membranes were prepared by interfacial polymerization on polyethersulfone (PES) supporting membrane. Different preparation conditions and NF membrane performances were discussed, including silica concentrations, monomer concentrations, reaction time and salt rejections. The chemical structure characterizations of polyamide composite membrane were carried out by attenuated total reflectance infrared (ATR-IR). The surface images and cross sections were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM). The results showed that polypiperazine-amide NF membrane prepared under the optimum conditions exhibited Na2SO4 rejection of 97.4% and water flux of 46.8 l.m− 2.h− 1. After addition of silica sol in the aqueous phase, the rejection of the resulting membrane changed slightly, but the water flux increased 21.1% than polypiperazine-amide NF membrane. According to the rejection of polyethylene glycols (PEGs), the molecular weight cut-off (MWCO) of the resulting membrane was under 600 Da.Highlights► Silica sol is used for preparation of silica/polypiperazine-amide NF membrane. ► Different polymerization conditions on membrane performance were investigated. ► The water flux rate was higher than that of polypiperazine-amide NF membrane.
Co-reporter:Deng Hu, Zhen-Liang Xu, Yong-Ming Wei, Yi-Fei Liu
Desalination (3 March 2014) Volume 336() pp:179-186
Publication Date(Web):3 March 2014
DOI:10.1016/j.desal.2013.11.025
•PSSS is used for preparation of PSSS/polypiperazine-amide NF membrane.•Effect of PSSS and silica concentrations on membrane performance were investigated.•The water flux rate was higher than with only polypiperazine-amide NF membrane.•The TFN membrane shows a promising capability for softening highly concentrated seawater.Poly(styrene sulfonic acid) sodium salt (PSSS)/polypiperazine-amide nanofiltration (NF) membrane and PSSS/SiO2/polypiperazine-amide NF membrane were prepared by interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) on polyethersulfone (PES) supporting membrane. Effect of PSSS and silica concentrations were discussed. The active surface of the membrane was characterized by using SEM and AFM. The results showed that PSSS/polypiperazine-amide NF membrane prepared under the optimum conditions exhibited Na2SO4 rejection of 96.1% and water flux with 55.7 L m− 2 h− 1 at operation pressure of 0.6 MPa. The rejection of Na2SO4, MgSO4, MgCl2 and NaCl follows a decreasing in order of 96.1%, 85.2% 45.4% and 21.1% respectively. After addition of 0.2% (w/v) silica in the aqueous phase, the water flux increased 42.7% compared with only polypiperazine-amide NF membrane. The PSSS/polypiperazine-amide NF membrane shows a promising capability for softening highly concentrated seawater from 8–20 wt.%.
Co-reporter:Bing-Wu Zhou, Hai-Zhen Zhang, Zhen-Liang Xu, Yong-Jian Tang
Desalination (15 September 2016) Volume 394() pp:176-184
Publication Date(Web):15 September 2016
DOI:10.1016/j.desal.2016.05.016
•Hollow fiber NF membranes were fabricated via IP, with mixed diamine monomers.•NF membrane exhibits PWP of 31.2 L·m-2·h-1 and Na2SO4 rejection of 99.7% at 6 bar.•NF membrane performance was stable during a 7-day filtration process.Thin film composite (TFC) hollow fiber nanofiltration (NF) membranes were fabricated via interfacial polymerization, with mixed diamines of piperazine (PIP) and 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline (BHTTM) as water phase and trimesoyl chloride (TMC) as organic phase. Fabricated membranes were characterized for ATR-FTIR, SEM, AFM, and water contact angle. Formation conditions of the selective polyamide layer have been optimized for a good NF membrane performance. The pure water flux of NF membrane prepared under optimized conditions was 31.2 L·m− 2·h− 1 and the rejection for Na2SO4 was 99.7% at 6 bar. The rejections of NF membranes for different salts followed the order: Na2SO4 > MgSO4 > NaCl > MgCl2. The molecular weight cut-off of NF membrane was around 300 Da. The performance of NF membranes was stable during a 7-day filtration process for rejecting different species ions including heavy metal ferric ion (FeCl3 and Fe2(SO4)3) and oxyanions (SO42 − and HPO42 −), in addition to different inorganic salts. Also, the NF membranes exhibited chlorine tolerant property. This work demonstrates the potential of PES outer-selective TFC hollow fiber membranes for desalination or water softening process, provides database to fabricate suitable NF membranes for long-term salts removal and raise a simple technique to form a thin chlorine-tolerant polyamide layer.
Co-reporter:Zhe-Qin Dong, Xiao-hua Ma, Zhen-Liang Xu, Wen-Ting You, Fang-bing Li
Desalination (15 August 2014) Volume 347() pp:175-183
Publication Date(Web):15 August 2014
DOI:10.1016/j.desal.2014.05.015
•PVDF–PTFE electrospun nanofibrous membranes (ENMs) were fabricated by electrospining.•The ENMs with different PTFE micro-powder contents were prepared and characterized.•The PVDF–PTFE electrospun nanofibrous membranes were superhydrophobic.•The ENMs were used for desalination via vacuum membrane distillation.•The ENMs presented a high permeate flux with stable performance.In this study, a superhydrophobic nanofibrous membrane was prepared on the basis of an electrospun polyvinylidene fluoride (PVDF)–polytetrafluoroethylene (PTFE) nanofibrous scaffold coupled with a microporous PTFE substrate. The PVDF–PTFE nanofibrous scaffold was fabricated by electrospining of PVDF–PTFE blend solutions, it was observed that by changing the PTFE micro-powder content in the dope solutions from 0 wt.% to 12 wt.%, the water contact angle (WCA) and the liquid entry pressure (LEPw) of the membrane vary from 130.4° and 84 kPa to 152.2° and 137 kPa, respectively. The superhydrophobic PVDF–PTFE nanofibrous membrane was then tested for desalination by vacuum membrane distillation (VMD), a stable flux of 18.5 kg/m2 h and salt rejection higher than 99.9% was presented throughout the entire testing period of 15 h, indicating the great potential of the PVDF–PTFE nanofibrous membranes in VMD. For further application of the PVDF–PTFE nanofibrous membranes in VMD, a mathematical model was presented to predict the vapor flux of the novel membrane under various operation conditions. A good agreement between the experimental and theoretical values for vapor fluxes was obtained; the results indicated that the VMD flux increased with the increase of feed temperature and flow rate and decreased with the increase of permeate pressure.
Co-reporter:Ping-Yun Zhang, Zhen-Liang Xu, Hu Yang, Yong-Ming Wei, Wen-Zhi Wu, Dong-Gen Chen
Desalination (14 June 2013) Volume 319() pp:47-59
Publication Date(Web):14 June 2013
DOI:10.1016/j.desal.2013.04.001
•Simplified blend method was beneficial to micro-stricture adjustment of PVDF casting solution.•PVDF membranes possessed narrow distribution pore size and molecular weight cut off (MWCO).•Ethanol coagulant resulted in obvious tunable morphologies and hydrophilicity improvement.P(PEGMA-r-MMA) amphiphilic copolymer with Mn of 66,500 g/mol and Mw of 34,200 g/mol was successfully synthesized via free radical polymerization. And polyvinylidene fluoride (PVDF)-P(PEGMA-r-MMA) blend membranes were fabricated from water and ethanol coagulants via simplified blend method by directly blending PVDF and P(PEGMA-r-MMA) amphiphilic copolymer solution (including the reaction mixture) to form casting solution. The formation of the supramolecular aggregates in PVDF solution containing the copolymer were confirmed by dynamic light scattering and scanning electron microscopy. This contributed to the micro-structure adjustment of PVDF solution and resulted in its decreasing surface tension, accelerating precipitation rate and increasing viscosity with trivial strain thinning behavior. Furthermore, the effects of the variations in dopant contents and coagulant compositions on the performances of those blend membranes were investigated. All PVDF-P(PEGMA-r-MMA) blend membranes possessed narrow distribution mean effective pore size (μ), molecular weight cut off (MWCO), improved recovery water flux after filtration experiments of bovine serum albumin and tuned configurations. Compared with the instantaneous demixing process in water coagulant, the delayed demixing process in ethanol favored the pore-forming and surface segregated of the polar head group of the copolymer, which induced the increasing μ, MWCO, tunable morphologies and hydrophilicity improvement.
Co-reporter:De Sun, Bing-Bing Li, Zhen-Liang Xu
Desalination (1 August 2013) Volume 322() pp:159-166
Publication Date(Web):1 August 2013
DOI:10.1016/j.desal.2013.05.008
•Organophilic nano-silica filled polydimethylsiloxane membranes are prepared.•The operation conditions of pervaporation for the ethanol–water mixture were studied.•These composite membranes exhibit striking performances.A novel organophilic nano-silica (ONS) filled polydimethylsiloxane (PDMS) composite membrane was prepared and characterized for the pervaporation (PV) of ethanol from water. The sorption and diffusion behaviors of ethanol and water in the composite membranes were investigated. The results showed that with increasing ONS concentration from 0 wt.% to 10 wt.%, the solubility selectivity and the diffusion selectivity increased from 21.87 to 38.85 and from 1.87 to 6.18, respectively. When the temperature ranged from 30 °C to 70 °C, the solubility selectivity increased but the diffusion selectivity first increased and then decreased. The effects of ONS content, feed temperature and permeate-side vacuum on the PV performance of the composite membrane for the pervaporation of 5 wt.% ethanol–water mixture were studied. The examinations showed that the composite membranes exhibited striking advantages in total flux and separation factor as compared with unfilled PDMS membrane. When ONS loading was 5 wt.%, the PDMS composite membrane showed the best PV performances with the permeate flux (J) of 114 g/(m2 · h), the separation factor (α) of 30.1 and permeate separate index (PSI), of 3420, respectively. With an increase of the feed temperature from 30 to 70 °C, the total flux of filled PDMS membrane with 5 wt.% ONS increased apparently from 11.1 to 210 g/(m2 · h), and the maximum separation factor of 30.1 was observed at 60 °C. With an increase of vacuum in permeate-side from 0.075 to 0.100 MPa, both separation factor and total flux increased for filled PDMS membrane with 5 wt.% ONS.
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