Co-reporter:Xiang Li;Binglun Chen;Weibin Cai;Tao Wang;Zhen Wu
RSC Advances (2011-Present) 2017 vol. 7(Issue 19) pp:11381-11388
Publication Date(Web):2017/02/13
DOI:10.1039/C6RA28866A
There is a lack of stable and hydrophobic organic solvent nanofiltration (OSN) membranes meaning that their implementation in non-polar solvent nanofiltration remains a challenge, typically in solvent (e.g. hexane) recovery during vegetable oil production (e.g. soybean oil/hexane). Considering this, novel trifluoropropylmethylsiloxane dimethylsiloxane (PDMS–PTFPMS)/polyvinylidene fluoride (PVDF) membranes, with both high hexane permeability of PDMS and excellent hexane stability of PTFPMS, were successfully developed to recover hexane via OSN. Their microstructure and surface properties were characterized by SEM, FTIR, DSC, TGA, XPS and contact angle measurements. We explored the effects of the ratio of the PTFPMS segment in polymer chain and polymer viscosity on membrane performance. With regards to the F50-M membrane, we also conducted a comprehensive study on the OSN performance of the F50-M membrane under different operational conditions. The oil rejection was above 95% with stable hexane permeability of 3.06 kg−1 μm m−2 h−1 bar−1 over a 32-day period. Experimental results confirmed its ability to recover hexane under various operational conditions, showing high oil rejection and excellent long-term operational stability. We attributed its outstanding performance to its unique microstructure and surface properties due to the fluorine-containing PTFPMS segment. This study indicates that fluoropolymer membranes are promising candidates in OSN processes, offering a wider choice of membrane materials and application fields.
Co-reporter:Tao Wang;Xinping He;Zhen Wu
RSC Advances (2011-Present) 2017 vol. 7(Issue 31) pp:19050-19059
Publication Date(Web):2017/03/28
DOI:10.1039/C6RA25880H
The air sparging method, which involves the introduction of air bubbles, is widely used in membrane separation to enhance performance. However, in flat sheet modules with distributors, the bubble behavior is complicated, which can have a critical impact on the air sparging efficiency. In this work, industrial-scale transparent modules were fabricated to visualize the two-phase flow with a distributor in different air sparging methods. Initially, the pressure drop in the channels induced by the inclusion of a distributor and spacer was evaluated, and the flow regime of the fluid was determined in visualization test. As for two-phase flows, five different solutions were investigated, categorized into two groups according to the coalescence behavior, namely the coalescence group and the non-coalescence group. Then, the bubble behaviors in a tubular flow module with different air sparging devices were studied for the two coalescence groups. In the pre-mixing method, the anti-coalescence phenomenon of bubbles clearly occurred at a high gas flow rate in the non-coalescence system. When an aerator head was used, smaller air bubbles were obtained, especially for the non-coalescence system, where the bubbles were small enough to ignore the resistance of the orifice. The flow patterns were subsequently investigated with empty flat sheet modules with different air sparging devices. Three flow regions were depicted for different solutions and air sparging devices. In the pre-mixing method, the coalescence effect led to a higher liquid flow rate being required to reach region (III) for water. The introduction of an aerator nozzle had the advantage of uniformly distributing the bubbles, while a higher gas flow rate was required to achieve a bubbly flow. With the incorporation of a spacer, the liquid flow rates needed to be higher than 0.32 m s−1 and 0.29 m s−1 to eliminate stagnant bubbles in the pre-mixing and air nozzle methods, respectively, in the coalescence system, and it was found the phenomenon was similar as for ethanol solution. According to our results, optimal operating conditions of air sparging devices for two-phase flow are proposed.
Co-reporter:Zhongguo Zhang, Dan Liu, Yu Qian, Yue Wu, ... Changqing Ye
Journal of Environmental Sciences 2017 Volume 56(Volume 56) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.jes.2016.09.011
A submerged internal circulating membrane coagulation reactor (MCR) was used to treat surface water to produce drinking water. Polyaluminum chloride (PACl) was used as coagulant, and a hydrophilic polyvinylidene fluoride (PVDF) submerged hollow fiber microfiltration membrane was employed. The influences of trans-membrane pressure (TMP), zeta potential (ZP) of the suspended particles in raw water, and KMnO4 dosing on water flux and the removal of turbidity and organic matter were systematically investigated. Continuous bench-scale experiments showed that the permeate quality of the MCR satisfied the requirement for a centralized water supply, according to the Standards for Drinking Water Quality of China (GB 5749-2006), as evaluated by turbidity (< 1 NTU) and total organic carbon (TOC) (< 5 mg/L) measurements. Besides water flux, the removal of turbidity, TOC and dissolved organic carbon (DOC) in the raw water also increased with increasing TMP in the range of 0.01–0.05 MPa. High ZP induced by PACl, such as 5–9 mV, led to an increase in the number of fine and total particles in the MCR, and consequently caused serious membrane fouling and high permeate turbidity. However, the removal of TOC and DOC increased with increasing ZP. A slightly positive ZP, such as 1–2 mV, corresponding to charge neutralization coagulation, was favorable for membrane fouling control. Moreover, dosing with KMnO4 could further improve the removal of turbidity and DOC, thereby mitigating membrane fouling. The results are helpful for the application of the MCR in producing drinking water and also beneficial to the research and application of other coagulation and membrane separation hybrid processes.Download high-res image (214KB)Download full-size image
Co-reporter:Xiang Li, Weibin Cai, Tao Wang, Zhen Wu, Jin Wang, Xinping He, Jiding Li
Separation and Purification Technology 2017 Volume 181(Volume 181) pp:
Publication Date(Web):30 June 2017
DOI:10.1016/j.seppur.2017.02.051
•AF2400/PTFE membrane utilized for hexane recovery via the OSN process.•High permeance of aliphatic solvents were obtained.•Oil rejection stayed above 98% over a 60-day testing.•Excellent durability and thermal stability were acquired.The use of OSN in the production of edible oil conserves energy making it extremely attractive, however, it should be noted that a physically and chemically stable membrane for this is required. Considering this, we selected the AF2400/PTFE composite membrane to recover hexane from the crude mixture of soybean oil and hexane via the OSN process. We carried out pure solvent permeation and rejection experiments, which verified the effectiveness of the membrane in separating and recovering hexane or other aliphatic solvents. We also conducted a comprehensive study on the effect of operational parameters, including long-term operation, transmembrane pressure, oil concentration and operational temperature. Permeate flux value varied in the range of 0.8–1.1 l m−2 h−1 bar−1 with oil rejection above 98% before or after physical aging for 1440 h in pure hexane. Experimental results confirmed the effectiveness of the AF2400/PTFE composite membrane in hexane recovery, showing high oil rejection and excellent long-term operational stability. We attributed the excellent performance of the AF2400/PTFE composite membrane to its unique surface properties, confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The study presented herein indicates that fluoropolymer based membranes are promising candidates in aliphatic solvent separation via the OSN process.
Co-reporter:Yang Xia, Zhen Wu, Bingxiong Lu, Tao Wang and Jiding Li
RSC Advances 2016 vol. 6(Issue 59) pp:53643-53650
Publication Date(Web):16 May 2016
DOI:10.1039/C6RA02037B
The UNIFAC model and its various modified models on behalf of the group contribution methods offer reliable knowledge of phase equilibrium data, which are making great contributions for separation processes. The application of the UNIFAC-ZM model for the silicone polymer system is not only restricted by the poor accuracy under a large temperature range, but also limited by the lack of SiO group related group interaction parameters. In this work, first, modification of the model was made with consideration of the temperature effect on group interactions. Then inverse gas chromatography (IGC), a simple method to determine the infinite dilution activity coefficient, was applied to determine the interaction parameters between the common groups CH3, OH, H2O, CH3CO and SiO contained in polydimethylsiloxane (PDMS) based on the equilibrium chromatography theory. The achieved model was further proved to agree with the experimental results well. The new model was also applied in the calculation of the partition equilibrium between acetone/butanol/ethanol water solutions of different concentrations and PDMS of different polymerization degrees and side chain length. All these results would not only help the improvement of UNIFAC model, but also instruct the separation processes of silicone polymer compounds.
Co-reporter:Manquan Fang, Chilung Wu, Zhengjin Yang, Tao Wang, Yang Xia, Jiding Li
Journal of Membrane Science 2015 Volume 474() pp:103-113
Publication Date(Web):15 January 2015
DOI:10.1016/j.memsci.2014.09.040
•ZIF-8/PDMS MMMs were fabricated and applied in hydrocarbon recovery.•Intimate interface interaction with enhanced selectivity for MMMs.•Modified Maxwell model taking non-ideal interface and agglomeration into account.•Extended application scope of Maxwell model with credible prediction result.In this contribution, zeolitic imidazolate framework (ZIF-8)/polydimethylsiloxane (PDMS) mixed matrix membranes (MMMs) were prepared for hydrocarbon recovery using propane/nitrogen mixture as a model feed gas pair. All MMMs obtained a homogeneous particle dispersion and intimate interface interaction, which were confirmed by high resolution scanning electric microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) mapping. Gas permeation test shows that ZIF-8/PDMS MMMs demonstrate an enhanced separation performance with improved separation selectivity (38% higher than that of pure PDMS membranes) and propane permeance over 100 GPU. However, it is worth noting that the enhanced selectivity and decreased permeance of MMMs contradict the prediction by Maxwell model, which suggests the existence of pore blockage and inhibited chain mobility at polymer-particle interface. The inhibited chain mobility is further confirmed by differential scanning calorimetry (DSC) analysis. Based on these observations, a new modified Maxwell model is proposed taking non-ideal interface morphology and particle agglomeration into consideration. Both the selectivity and gas permeance predicted by the proposed model are in good agreement with experimental data, which thereby extends the application scope of original Maxwell model.
Co-reporter:J. Liu;X. Lu;J. Li;C. Wu
Journal of Polymer Research 2014 Volume 21( Issue 10) pp:
Publication Date(Web):2014 October
DOI:10.1007/s10965-014-0568-3
Tensile strength is of paramount importance to poly (vinylidene fluoride) (PVDF) membranes in expanding their industrial application. In this paper, porous PVDF membranes with higher tensile strength were prepared by the low temperature thermally induced phase separation (LT-TIPS) method. The effects of mixed diluents (MD) composition on the morphology, polymorphism, and tensile strength of such prepared flat sheet membranes were investigated. The competition of membrane formation mechanisms between the nonsolvent induced phase separation (NIPS) and TIPS was demonstrated by observing the membrane morphology in the LT-TIPS process. It was found that the tensile strength was improved by suppressing the formation of finger-like macrovoids and spherulitic morphologies through adjusting the composition of MD. PVDF crystallized into α phase for all the investigated cases, and as the MD became poorer, the total crystallinity increased slightly. Based on these experimental results, PVDF hollow fiber membranes were fabricated via LT-TIPS. The influences of MD composition and polymer concentration on the morphology, water permeability and tensile strength of the formed hollow fiber membranes were studied. The properties of optimized hollow fiber membranes associated with the surface and cross-section morphologies were promising and the performance can be further enhanced in future work.
Co-reporter:Zheng-Jin Yang, Zhi-Qiang Wang, Jiding Li, Jin-Xun Chen
Separation and Purification Technology 2013 Volume 109() pp:48-54
Publication Date(Web):9 May 2013
DOI:10.1016/j.seppur.2013.01.056
Nowadays, pervaporation is widely investigated as a promising process in FCC (fluid catalytic cracking) gasoline deep desulfurization, in which the membrane plays a decisive role. In this work, a membrane with high desulfurization performance was initiated and its pervaporation performance was evaluated using FCC model gasoline composed of thiophene and heptane. The membrane was prepared from chlorine incompletely substituted poly [bis (phenoxy) phosphazene] (Cl-PBPP) followed by simple self-crosslinking at room temperature. Compared with previous jobs, the Cl-PBPP is 12 times increased in pervaporation separation index. Moreover, via self-crosslinking the trade-off effect is eliminated. The highest enrichment factor and flux of Cl-PBPP membrane for separating thiophene from heptane are 5.6 and 1.38 kg/(m2 h), respectively. The obtained results are promising for industrial trial.Highlights► Cl-PBPP is firstly investigated in FCC gasoline desulfurization. ► Normalized PSI is average 12 times increased compared with PTFEP. ► Trade-off effect is eliminated by self-crosslinking at room temperature. ► Cl-PBPP performance is stable to the change in feed sulfur content.
Co-reporter:Zhengjin Yang, Tao Wang, Xia Zhan, Jiding Li, and Jinxun Chen
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 38) pp:13801-13809
Publication Date(Web):2017-2-22
DOI:10.1021/ie402022a
This work investigates the application of poly[bis(p-methyl phenyl) phosphazene] (PMePP) for separating organosulfur compounds from n-heptane. PMePP was synthesized and characterized by NMR, X-ray photo spectroscopy, thermogravimetric analysis, scanning electron microscopy, and Fourier transformed infrared spectroscopy. Membranes based on PMePP were fabricated and investigated for desulfurization of FCC (fluid catalytic cracking) model gasoline by pervaporation. The effects of operating temperature, feed composition, and feed sulfur content on the performance of PMePP membranes were investigated. The experimental results showed that the PMePP-based membranes are effective for FCC gasoline pervaporative desulfurization. To provide active spots for future grafting modification, the surface functionalization of PMePP was carried out to convert the methyl units into carboxylic units. The surface-functionalized membrane was also investigated for its pervaporation performance, and results showed the increased in enrichment factor and less temperature dependence.
Co-reporter:Lei Wang;Xiaolong Han;Dongju Zheng ;Lin Qin
Journal of Applied Polymer Science 2013 Volume 127( Issue 6) pp:4662-4671
Publication Date(Web):
DOI:10.1002/app.38046
Abstract
Inorganic–organic hybrid membrane materials always exhibit high pervaporation performance for organic azeotropic mixtures. Here, MCM-41 silica spheres were modified and embedded into polydimethylsiloxane, and a new filled membrane was obtained. The membrane was used in dimethylcarbonate (DMC) removal from DMC/methanol azeotropic mixture by pervaporation. The effect of membrane preparation parameters including modified MCM-41 silica spheres loading, solvent concentration, and feed temperature on pervaporation properties was systematically studied. The results showed that separation factor and total flux of the filled membranes could be increased simultaneously. Additionally, the sorption and diffusion selectivity of the filled membranes were measured and discussed. The results demonstrated that diffusion selectivity was greatly enhanced by incorporating. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Zhengjin Yang, Weiyu Zhang, Jiding Li, Jinxun Chen
Separation and Purification Technology 2012 Volume 93() pp:15-24
Publication Date(Web):1 June 2012
DOI:10.1016/j.seppur.2012.03.015
Concerning the standstill state of pervaporation desulfurization, development of new pervaporation desulfurization membranes is vital. The polymer selection can be based on solubility parameter theory. Using group contribution method, the solubility parameter of poly[bis(trifluoroethoxy) phosphazene] (PTFEP) was calculated. The differences in solubility parameters between thiophene and polymers including PTFEP were calculated and investigated for their potential application as pervaporation desulfurization membranes. PTFEP had the most similar solubility parameter to thiophene among the polymers calculated in this work. The results indicated superior possibility for its application in pervaporation desulfurization. PTFEP was thus synthesized and characterized by DSC, GPC, XPS, 1H-NMR and 31P-NMR. The PTFEP composite membrane was fabricated and utilized in pervaporation removal of thiophene. A pretty high sulfur enrichment factor of 15.69 was obtained which confirmed the results suggested by the solubility parameter theory. Compared with literatures, we positively believe that an increase in solubility parameter differences causes a decrease in sulfur enrichment factor. Meanwhile, the swelling behavior and morphology of the membrane, the effect of feed temperature, and the effect of feed sulfur concentration were also investigated.Highlights► Solubility parameter theory was used for selection of PV desulfurization membrane. ► Solubility parameters of 25 polymers were calculated using group contribution method. ► PTFEP was selected according to solubility parameter analysis. ► Separation factor of around 16 was obtained.
Co-reporter:Lei Wang, Xiaolong Han, Jiding Li, Lin Qin, Dongju Zheng
Powder Technology 2012 Volume 231() pp:63-69
Publication Date(Web):November 2012
DOI:10.1016/j.powtec.2012.07.044
Mesoporous MCM-41 silica spheres were synthesized via modified Stöber method and modified by silylation. The MCM-41 pore structures, surface properties and morphological features before and after modification were examined by XRD, SEM, TEM, FT-IR, TGA, 29Si CP/MAS NMR and nitrogen adsorption–desorption. The results showed that the obtained MCM-41 silica had ordered mesoporous structure and spherical morphology. After silylation, the surface property of MCM-41 silica changed from hydrophilic to hydrophobic, whereas the MCM-41 framework and morphology were retained. The calcined and modified MCM-41 spheres were incorporated into a polydimethylsiloxane (PDMS) matrix, separately. It is clearly shown from the SEM image that modification of MCM-41 spheres greatly enhanced its interfacial adhesion with the polymer. The filled membrane was firstly used for pervaporation separation of dimethylcarbonate/methanol azeotropic mixture and displayed superior pervaporation performance than pure PDMS membranes.Mesoporous MCM-41 silica spheres were synthesized and modified by silylation. The modified MCM-41 spheres were incorporated into a polydimethylsiloxane (PDMS) matrix. SEM image showed that modification of MCM-41 spheres could greatly enhance its interfacial adhesion with the polymer. The filled membrane displayed superior pervaporation performance.Highlights► Mesoporous MCM-41 spheres were successfully synthesized and modified by silylation. ► Modified MCM-41/PDMS hybrid membranes were prepared as a new membrane material. ► The interfacial adhesion between MCM-41 and PDMS could be enhanced by silylation. ► Selectivity and flux of modified MCM-41/PDMS membrane can be raised simultaneously.
Co-reporter:Zhengjin Yang, Zhiqiang Wang, Jiding Li and Jinxun Chen
RSC Advances 2012 vol. 2(Issue 30) pp:11432-11437
Publication Date(Web):31 Aug 2012
DOI:10.1039/C2RA21418K
By changing pendant groups of polyphosphazene, poly[bis(phenoxy)phosphazene] (PBPP) were synthesized, characterized and investigated in model gasoline desulfurization experiments via pervaporation. Compared with poly[bis(trifluoroethoxy)phosphazene] (PTFEP), PBPP was substantially improved in pervaporation performance, thermal stability and swelling stability. The possibility of PBPP composite membrane for industrial experiments was also investigated. PBPP showed high toughness, long time durability and effective desulfurization property in laboratory scale experiments and based on the obtained results, PBPP was firmly believed to be a promising pervaporative membrane material for pervaporation desulfurization of gasoline in industrial experiments.
Co-reporter:Xiaolong Han;Lei Wang;Xia Zhan;Jian Chen ;Jichu Yang
Journal of Applied Polymer Science 2011 Volume 119( Issue 6) pp:3413-3421
Publication Date(Web):
DOI:10.1002/app.32991
Abstract
In this study, poly(dimethyl siloxane) (PDMS)/poly(vinylidene fluoride) (PVDF), poly(phenyl methyl siloxane) (PPMS)/PVDF, poly(ethoxy methyl siloxane) (PEOMS)/PVDF, and poly(trifluropropyl methyl siloxane) (PTFMS)/PVDF composite membranes were prepared. The different functional compositions of these membranes were characterized by Fourier transform infrared spectroscopy. The surfaces and sections of these membranes were investigated by scanning electron microscopy. The hydrophobicity at the membrane surface was assessed with contact angle measurement. Swelling experiments were carried out to investigate the swelling behavior of these membranes. The composite membranes prepared in this study were used in the pervaporation separation of ethanol/water mixtures, and their separation performances were compared. The results show that the separation performances of these membranes were strongly related to the silicone rubber components and composition, the total fluxes decreased in the following order: PDMS > PPMS > PEOMS > PTFMS. The separation factor followed the following order: PPMS > PEOMS > PDMS > PTFMS (5 wt % ethanol at 40°C). In addition, the effects of the feed temperature (40–70°C) and feed composition (5–20 wt %) on the separation efficiency were investigated experimentally. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Jian Chen;Jinxun Chen;Xiaolong Han;Xia Zhan ;Cuixian Chen
Journal of Applied Polymer Science 2010 Volume 117( Issue 4) pp:2472-2479
Publication Date(Web):
DOI:10.1002/app.32145
Abstract
Hydroxyl-terminated polybutadiene/acrylonitrile (HTBN) polymer material was selected for deep desulfurization of liquefied petroleum gas (LPG) according to the solubility parameter method, and then crosslinked HTBN membranes were prepared, in which asymmetric polyacrylonitrile (PAN) membranes prepared with phase inversion method acted as the microporous supporting layer in the flat-plate composite membrane. The different function compositions of composite membranes were characterized by reflection FTIR in order to investigate the crosslinking reaction. The surface and section of composite membranes were investigated by scanning electron microscope (SEM). The composite membranes prepared in this study were used in LPG for deep desulfurization. Effects of amount of HTBN and operation pressure on the desulfurization efficiency of LPG were investigated experimentally. Experiment results demonstrated that with the membrane having a HTBN layer of 11 μm, permeability parameter of methyl mercaptan came to 17,002 Barrer and that of hydrocarbon came to 504 Barrer at 30 wt % of HTBN and 0.25 MPa, which showed that the membrane used to desulfurization in LPG can achieve high-removal efficiency. These results demonstrated that the membrane separation method could be significant in practical application for deep desulfurization of LPG. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Xia Zhan;Ji-ding Li 李继定;Cheng Fan;Xiao-long Han
Chinese Journal of Polymer Science 2010 Volume 28( Issue 4) pp:625-635
Publication Date(Web):2010 July
DOI:10.1007/s10118-010-9136-4
Ultra-fine silicalite-1 particles were modified with four kinds of chlorosilanes (dodecyltrichlorosilane, octyltrichlorosilane, hexadecyltrichlorosilane and octadecyltrichlorosilane) and characterized by FI-IR, TGA, contact angle measurements and BET analysis. It was found that the surface hydrophobicity of silicalite-1 particles was improved significantly as the alkyl group was strongly bonded to the particle surface. Modified silicalite-1 particles were incorporated into PDMS (poly(dimethylsiloxanediol)) membranes, which were applied for the pervaporation separation of ethanol/water mixtures. The effect of surface properties, zeolite loading and operation conditions on pervaporation performance of the membranes was investigated. The separation factor of PDMS membranes filled with modified silicalite-1 increased considerably compared with that filled with unmodified ones, and the total flux decreased with increasing zeolite loading. The solution and diffusion selectivity of hybrid membranes were also measured to explain the pervaporation properties of silicalite-1 filled PDMS membranes. It was found that modification of silicalite-1 with dodecyltrichlorosilane effectively improved the solution and diffusion selectivity of silicalite-1 filled PDMS membranes with high zeolite loading. This may be attributed to the high surface hydrophobicity of modified silicalite-1 and its good integration with PDMS membranes. Both the high separation factor and solution selectivity indicated that modification of silicalite-1 with chlorosilanes was an effective method to improve the selectivity of silicalite-1/PDMS hybrid membranes for ethanol.
Co-reporter:Jian Chen, Jiding Li, Jinxun Chen, Yangzheng Lin, Xiaogong Wang
Separation and Purification Technology 2009 Volume 66(Issue 3) pp:606-612
Publication Date(Web):7 May 2009
DOI:10.1016/j.seppur.2009.01.007
Crosslinked polyethylene glycol/polyetherimide (PEG/PEI) composite membranes were prepared, in which asymmetric PEI membrane prepared with phase inversion method acted as the microporous supporting layer in the flat-plate composite membrane. The different function compositions of the PEG/PEI composite membranes were characterized by reflection FTIR. The surface and section of PEG/PEI composite membranes were investigated by scanning electron microscope (SEM). The composite membranes prepared in this work were employed in pervaporation separation of ethyl thioether/heptane mixtures. Swelling experiments were carried out in ethyl thioether/heptane mixtures to investigate the stable behavior of the membranes. Effects of amount of PEG, crosslinking temperature, amount of crosslinking agent and crosslinking time on the separation efficiency of ethyl thioether/heptane mixtures were studied experimentally. Experiment results demonstrated that crosslinking temperature at 80–100 °C was more preferable, the amount of crosslinking agent was up to 16 wt%, and PEG amount at 14 wt% was optimal as far as flux and sulfur enrichment factor was concerned. In addition, the stability of composite membrane during long time operation was studied, which could be expected that the membrane prepared in the work should be used to separate ethyl thioether/heptane mixtures in real application.
Co-reporter:Jian Chen;Yangzheng Lin ;Cuixian Chen
Journal of Applied Polymer Science 2009 Volume 112( Issue 4) pp:2425-2433
Publication Date(Web):
DOI:10.1002/app.29799
Abstract
Crosslinked polydimethylsiloxane/polyetherimide (PDMS/PEI) composite membranes were prepared, in which asymmetric microporous PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat-plate composite membrane. The different function composition of the PDMS/PEI composite membranes were characterized by reflection Fourier transform infrared (FTIR) spectroscopy. The surface and section of PDMS/PEI composite membranes were investigated by scanning electron microscope (SEM). The composite membranes prepared in this work were employed in pervaporation separation of benzene/cyclohexane mixtures. Effects of feed temperature, feed composition, concentration of crosslinking agent on the separation efficiency of benzene/cyclohexane mixtures were investigated experimentally. In addition, the swelling rate and stableness of composite membrane during long time operation were studied, which should be significant for practical application. The results demonstrated that the pervaporation method could be very effective for separation of the benzene/cyclohexane mixtures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Jian Chen, Jiding Li, Rongbin Qi, Hong Ye, Cuixian Chen
Journal of Membrane Science 2008 Volume 322(Issue 1) pp:113-121
Publication Date(Web):1 September 2008
DOI:10.1016/j.memsci.2008.05.032
Crosslinked PDMS/PEI composite membranes were prepared, in which asymmetric PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat-plate composite membrane. The different function composition of the PDMS/PEI composite membranes were characterized by reflection FTIR. The surface and section of PDMS/PEI composite membranes were investigated by scanning electron microscope (SEM). The infinite dilute activity and diffusion coefficients of thiophene, 2-methyl thiophene, 2,5-dimethyl thiophene, n-butyl mercaptan, n-butyl sulfide in crosslinked PDMS were measured in the temperature range of 80–100 °C by inverse gas chromatography. The solubility parameters of thiophene, 2-methyl thiophene, 2,5-dimethyl thiophene, n-butyl mercaptan, n-butyl sulfide were calculated by the group contribution method and the selectivity of PDMS composite membrane for different organic sulfur compounds was investigated. The composite membranes prepared in this work were employed in pervaporation separation of n-heptane and different sulfur forms mixtures. The theoretical results showed good agreement with the experimental results, and the order of partial permeate flux and selectivity for different organic sulfur compounds was: thiophene > 2-methylthiophene > 2,5-dimethylthiophene > n-butyl mercaptan > n-butyl sulfide, which should be significant for practical application.
Co-reporter:Junqi Huang;Xia Zhan ;Cuixian Chen
Journal of Applied Polymer Science 2008 Volume 110( Issue 5) pp:3140-3148
Publication Date(Web):
DOI:10.1002/app.28895
Abstract
A better understanding of the mass transfer in pervaporation membranes under different conditions is essential for both the design of improved membranes in various applications, and for the process design. In this article, a modified solution-diffusion model is proposed to account for the mass transport of penetrants in the polymer membrane. In the model, the group contribution method (the UNIFAC-ZM model) is first introduced to calculate the activity of penetrants in the polymer membrane, and a modified Fujita diffusion coefficient equation is developed to describe the diffusion behavior of the penetrants. The aim of this work is to establish a predictive solution-diffusion model. By refitting the group interaction parameters based on pervaperation data of penetrants-membrane systems, the model can be applied to predict the flux and separation factor of various polymer membrane systems. As an exemplary application of the model, the permeation fluxes and separation factors of alkane/thiophene and alkane/2-methyl-thiophene mixtures in polydimethylsiloxane (PDMS) membrane system have been predicted and showed to be in good agreement with experimental values. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Luying Wang, Jiding Li, Yangzheng Lin, Cuixian Chen
Journal of Membrane Science 2007 Volume 305(1–2) pp:238-246
Publication Date(Web):15 November 2007
DOI:10.1016/j.memsci.2007.08.008
A serial of poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) blend membranes with different PAA/PVA ratio were prepared for separating dimethyl carbonate (DMC)/methanol (MeOH) mixtures by pervaporation. FTIR was used to determine whether there was an esterification reaction between PAA and PVA. Swelling experiments were carried out in DMC/MeOH mixtures by using different blend membranes to investigate the swelling behavior of the membranes. The blend membranes with different PAA content were used to separate DMC/MeOH azeotrope through pervaporation experiments. The effects of operation temperatures and feed composition on pervaporation performances were also investigated. The results showed that the blend membrane containing 70 wt.% PAA had a highest separation factor of 13 and a permeate flux of 577 g/(m2 h) at 60 °C for separating DMC/MeOH azeotrope, which could be expected that the membrane prepared in this work should be used to separate DMC/MeOH mixtures in real application.
Co-reporter:Rongbin Qi, Yujun Wang, Jian Chen, Jiding Li, Shenlin Zhu
Separation and Purification Technology 2007 Volume 57(Issue 1) pp:170-175
Publication Date(Web):1 October 2007
DOI:10.1016/j.seppur.2007.04.001
Mixed matrix membranes of polydimethylsiloxane (PDMS) with silver oxide (Ag2O) as the filler were prepared and used for desulfurization of model gasoline composed of n-octane and thiophenes. The effect of the degree of Ag2O loading, feed temperature on the pervaporation properties of Ag2O-filled PDMS membranes was investigated experimentally. Ag2O-filling leads to a decrease in total flux because of the tortuosity effect of the impermeable Ag2O particles dispersed in the membranes. Due to the physio-chemical interactions between Ag2O and thiophenes, an increase in selectivity to thiophenes was gained with Ag2O-filled membranes. Feed temperature shows different impact on selectivity to thiophenes for Ag2O-filled and unfilled membranes. Analysis of the selectivity–permeability trade-off was carried out for both the filled and unfilled membranes.
Co-reporter:Changwei Zhao;Chuyi Zeng
Journal of Applied Polymer Science 2006 Volume 101(Issue 3) pp:1925-1930
Publication Date(Web):24 MAY 2006
DOI:10.1002/app.23658
Infinite dilution diffusion and activity coefficients of n-hexane, n-heptane, and n-decane in polypropylene were measured from 373.15 to 393.15 K by inverse gas chromatography. The influences of small molecule solvent and temperature on the infinite dilution diffusion and activity coefficients were investigated. The results showed that the infinite dilution diffusion coefficient decreased but the infinite dilution activity coefficient increased with an increasing number of CH2 group in the aliphatic solvents. The temperature increase resulted in the increase in the infinite dilution diffusion coefficient and the decrease in the infinite dilution activity coefficient. The graphs plotted according to the results of the infinite dilution diffusion coefficient versus temperature were in agreement with the Arrhenius equation. Diffusion constant and activation energy were obtained from the Arrhenius equation. Also, the interdependence on the infinite dilute activity coefficient and temperature accorded with Gibbs-Helmholtz equation. From the temperature dependence of the limiting activity coefficients partial molar excess enthalpy at infinite dilution HE,∞ was obtained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1925–1930, 2006
Co-reporter:Chuyi Zeng;Tianquan Chen;Jian Chen;Cuixian Chen
Journal of Applied Polymer Science 2006 Volume 102(Issue 3) pp:2189-2198
Publication Date(Web):23 AUG 2006
DOI:10.1002/app.24265
Series of polyimide membranes were synthesized using varied monomers such as pyromellitic dianhydride, 3,3′4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-diaminodiphenylether, 4,4′-diaminodiphenylmethane, and phenylenediamine, and the properties of polyimide membranes were measured by experimental techniques. The dynamic sorption and transport processes of water vapor in those dense polyimide membranes were measured using computer on-line recorded gravimetric sorption method at 298.15 and 308.15 K. Modeling of these processes involved the total change of excess Gibbs free energy, which was considered as a sum of three parts calculated by the modified Scatchard-Hildebrand model, Flory-Huggins theory, and linear viscoelastic theory, respectively. The calculated results were in agreement with the experimental data and the maximal relative deviation was no more than 8.57% and the average relative deviation is 4.62%. The calculated results had also shown that this model describe not only Fickian diffusion but also non-Fickian very well. Furthermore, the influence of chemical structure, morphological structure, etc. of polyimide membranes on the water sorption concentration and water diffusion coefficient were interpreted by considering the experimental data and calculation results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2189–2198, 2006
Co-reporter:Weibin CAI, Yanzhi SUN, Xianglan PIAO, Jiding LI, Shenlin ZHU
Chinese Journal of Chemical Engineering (August 2011) Volume 19(Issue 4) pp:575-580
Publication Date(Web):1 August 2011
DOI:10.1016/S1004-9541(11)60024-4
Traditional solvent recovery in the extraction step of edible oil processing is distillation, which consumes large amounts of energy. If the distillation is replaced by membrane process, the energy consumption can be reduced greatly. In this work, two kinds of membrane, PDMS (polydimethylsiloxane) composite membrane and Zeolite filled PDMS membrane were prepared, in which asymmetric microporous PVDF (polyvinylidenefluoride) membrane prepared with phase inversion method was functioned as the microporous supporting layer in the flat-plate composite membrane. The different function compositions of the PDMS/PVDF composite membranes were characterized by reflection Fourier transform infrared (FTIR) spectroscopy. The surface and section of PDMS/PVDF composite membranes were investigated by scanning electron microscope (SEM). The PDMS NF (nanofiltration) membranes were then applied in the recovery of hexane from soybean oil/hexane miscellas (1:3, mass ratio). The effects of pressure (0.5-1.5 MPa), cross-linking temperature and PDMS layer thickness on membrane performances were investigated. The results indicated that both two kinds of NF membranes were promising for solvent recovery, and zeolite filled in PDMS NF membrane could enhance the separation performance.
Co-reporter:Dongju Zheng, Weibin Cai, Tao Wang, Lin Qin, Zhongguo Zhang, Xiaojing Ren, Jiding Li, Zhengjin Yang
Desalination (2 February 2015) Volume 357() pp:215-224
Publication Date(Web):2 February 2015
DOI:10.1016/j.desal.2014.11.026
•Acrylonitrile wastewater with high concentration was treated by a novel integrated membrane system (IMS).•UF, NF and RO were included in IMS; pilot-scale plants of IMS were built and tested for 1600 h.•Technical and economic analyses of pilot scale-plants were studied and compared with present four-effect evaporation system.•IMS has a good application in acrylonitrile wastewater treatment instead of four-effect evaporation.The production of acrylonitrile exceeds 5 million tons every year throughout the world, which leads to the huge emission of acrylonitrile wastewater. Hence, treating the acrylonitrile wastewater remains challenging. In this study, a pilot scale integrated membrane system (IMS) consisting of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) was proposed to treat the highly concentrated acrylonitrile wastewater from petrochemical plants. A preliminary techno-economic study for a 24 m3/day wastewater treatment pilot plant was conducted. The system runs smoothly in 1600 h operation. In treating acrylonitrile wastewater with COD 22,000–30,000 mg/L, NH3-N 14–40 mg/L, CN− 20–55 mg/L, the effluent water quality of IMS was COD < 3000 mg/L, NH3-N < 10 mg/L, CN− < 5 mg/L. The results show that the developed IMS is effective for the treatment of acrylonitrile wastewater and industrialization of IMS is prospective.
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