The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Enrico Drioli - One of the best experts on this subject based on the ideXlab platform.
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enhanced fouling and wetting resistance of composite Hyflon ad poly vinylidene fluoride membrane in vacuum membrane distillation
Separation and Purification Technology, 2019Co-Authors: Yongxing Zhang, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Zhaoliang Cui, Jingyi Cao, Shouyong Zhou, Shuaifei ZhaoAbstract:Abstract Membrane fouling and pore wetting are the key problems affecting the separation performance of membrane distillation (MD). They can become more severe with increasing the operation time, which will have a negative impact on heat and mass transfers. In this paper, solutions containing CaCO3, humid acid (HA), and/or silica sols (SiO2) were used as the feed with different Hyflon AD/polyvinylidene fluoride (PVDF) composite membranes for vacuum membrane distillation (VMD). The evolutions of flux and salt rejection during the concentration process were examined, and the membranes with different properties were compared. The results showed that the original membrane was more prone to be fouled and wetted even at low concentration factors. In the single-component systems, CaCO3 impacts the membrane performance most severely. With the hybrid component solutions, the flux declines for the composite membranes were lower than that of the original membrane. Compared with the single-component systems, the practical situation is more likely close to the hybrid-component system where fouling and wetting were easier to happen. Overall, the composite membranes showed enhanced fouling and wetting resistance and maintained stable salt rejections. Particularly, the composite membrane with smaller pore sizes (M-40L) performed best among all the membranes, suggesting its high potential for practical VMD applications.
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optimization of novel composite membranes for water and mineral recovery by vacuum membrane distillation
Desalination, 2017Co-Authors: Zhaoliang Cui, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Yongxing Zhang, Shuaifei ZhaoAbstract:Abstract In mining industries, the process combining ultrafiltration (UF) and reverse osmosis (RO) is often used for wastewater treatment, but RO brine discharge is a big issue. Membrane distillation (MD) has been proposed to solve this problem by significantly increasing the water recovery ratio, and recovering minerals. However, membranes with high hydrophobicity targeting for MD, particularly for vacuum membrane distillation (VMD) are still scarce. Hyflon AD is a novel candidate for fabricating membranes for MD. In this paper, the effects of membrane fabrication parameters, such as coating time, heat treatment and pre-filling were investigated and optimized. Membrane morphology, mechanical properties and VMD performance of the composite membranes were tested. The results showed that the hydrophobicity and elongation at break of the membrane were significantly improved after coating. The coating polymer concentration, coating time, heat treatment temperature and heat treatment time for the membrane coated by Hyflon AD40L and Hyflon AD40H, respectively were optimized. Monovalent alcohols can be excellent pre-filling agents to improve membrane performance. Separation performance of the membrane coated by Hyflon AD40H was better than that of the one coated by Hyflon AD40L.
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enhancing wetting resistance of poly vinylidene fluoride membranes for vacuum membrane distillation
Desalination, 2017Co-Authors: Yongxing Zhang, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Zhaoliang Cui, Shuaifei ZhaoAbstract:Abstract Composite membranes were fabricated by coating three types of highly hydrophobic perfluorinated copolymers (commercial name: Hyflon AD) on poly(vinylidene fluoride) hollow fibers. The membrane properties, including morphologies, pore sizes, porosities, liquid entry pressures (LEPs), mechanical strength, and separation performance (flux, rejection and wettability) in vacuum membrane distillation (VMD) were systematically characterized and investigated. The properties of the fabricated membranes, including pore sizes, pore size distributions, porosities, and LEPs were significantly affected by the viscosity of the coating polymer solution. Coating solutions with lower viscosities caused smaller pore sizes, narrower pore size distributions, lower porosities, higher LEPs and less flux decline in VMD. Particularly, LEP of the membrane coated with a lower viscosity solution (0.46 MPa) was two times higher than that of the uncoated membrane (0.23 MPa). As a result, the anti-wetting property of the composite membrane after coating was significantly enhanced compared with that of the original membrane. The coated composite hollow fiber membranes also showed improved hydrophobicity, mechanical strength and separation performance (water flux and salt rejection). The water contact angle of the membrane increased from 94 to 145° after coating with a lower viscosity solution.
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preparation of Hyflon ad60 pvdf composite hollow fiber membranes for vacuum membrane distillation
Separation and Purification Technology, 2016Co-Authors: Daqing Tong, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Mohammad Ali, Yong Wang, Zhaoliang CuiAbstract:Abstract Hydrophobic membrane is desired to avoid pore wetting phenomenon in membrane distillation (MD). In the present paper, highly hydrophobic Hyflon AD60/PVDF composite hollow fiber membranes were prepared by coating a copolymer (Hyflon AD60) of tetrafluoroethylene (TFE) and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD) on poly(vinylidene fluoride) (PVDF) membranes. The effects of Hyflon AD60 concentration, coating time, heat-treatment temperature and heat-treatment time on the structures and performances of Hyflon AD60/PVDF composite hollow fiber membranes in vacuum membrane distillation (VMD) process were investigated. The results show that the hydrophobicity of PVDF hollow fiber membrane was significantly improved by coating Hyflon AD60. The optimized Hyflon AD60 concentration, coating time, heat-treatment temperature and heat-treatment time were 0.1 wt%, 10–20 min, 40–50 °C and 9 h, respectively. Employing NaCl solution with concentration of 35 g × L−1, under a vacuum of 0.09 MPa and feed temperature of 70 °C, the water flux and salt rejection of the composite hollow fiber membrane in VMD process reached to approximately 10 kg × m−2 × h−1 and higher than 99.9 %, respectively, and kept stable, indicating that Hyflon AD60/PVDF composite membrane is an excellent candidate for operation in VMD operation.
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organic vapour transport in glassy perfluoropolymer membranes a simple semi quantitative approach to analyze clustering phenomena by time lag measurements
Journal of Membrane Science, 2011Co-Authors: J C Jansen, Karel Friess, Enrico DrioliAbstract:In this paper the gas and vapour transport through four different high fractional free volume amorphous glassy perfluoropolymers is studied, namely Teflon® AF and Hyflon® AD. The paper describes a new approach to evaluate the anomalous diffusion of alcohol vapours in these materials. Permanent gases and the vapours of aprotic solvents like acetone and dichloromethane exhibit normal behaviour. For these species the transient in the permeation curve can be described by the classical penetration theory with a single diffusion coefficient. In contrast, aliphatic alcohols exhibit an unusually long transient. Careful analysis of the curve shape by stepwise fitting with a nonlinear least squares optimization procedure demonstrates that such behaviour can be described in terms of simultaneous diffusion of species with different diffusion coefficients. This can be attributed to the co-existence of single penetrant molecules and larger clusters, the latter diffusing more than one order of magnitude slower than the single molecules. The proposed semi-quantitative method offers the possibility to estimate the average cluster size. The cluster size of methanol and ethanol in Teflon AF2400 is very close to that reported in the literature. The average cluster size is relatively independent of the polymer type and free volume but it decreases with increasing size of the alcohol. A critical analysis of the potential and limitations of the method is made. Application of the ENSIC model on independent sorption data gave excellent agreement with the experimental data and confirmed the clustering. A preliminary discussion on the possible evaluation of the transport properties in terms of concentration dependent diffusion is also provided.
Shuaifei Zhao - One of the best experts on this subject based on the ideXlab platform.
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enhanced fouling and wetting resistance of composite Hyflon ad poly vinylidene fluoride membrane in vacuum membrane distillation
Separation and Purification Technology, 2019Co-Authors: Yongxing Zhang, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Zhaoliang Cui, Jingyi Cao, Shouyong Zhou, Shuaifei ZhaoAbstract:Abstract Membrane fouling and pore wetting are the key problems affecting the separation performance of membrane distillation (MD). They can become more severe with increasing the operation time, which will have a negative impact on heat and mass transfers. In this paper, solutions containing CaCO3, humid acid (HA), and/or silica sols (SiO2) were used as the feed with different Hyflon AD/polyvinylidene fluoride (PVDF) composite membranes for vacuum membrane distillation (VMD). The evolutions of flux and salt rejection during the concentration process were examined, and the membranes with different properties were compared. The results showed that the original membrane was more prone to be fouled and wetted even at low concentration factors. In the single-component systems, CaCO3 impacts the membrane performance most severely. With the hybrid component solutions, the flux declines for the composite membranes were lower than that of the original membrane. Compared with the single-component systems, the practical situation is more likely close to the hybrid-component system where fouling and wetting were easier to happen. Overall, the composite membranes showed enhanced fouling and wetting resistance and maintained stable salt rejections. Particularly, the composite membrane with smaller pore sizes (M-40L) performed best among all the membranes, suggesting its high potential for practical VMD applications.
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optimization of novel composite membranes for water and mineral recovery by vacuum membrane distillation
Desalination, 2017Co-Authors: Zhaoliang Cui, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Yongxing Zhang, Shuaifei ZhaoAbstract:Abstract In mining industries, the process combining ultrafiltration (UF) and reverse osmosis (RO) is often used for wastewater treatment, but RO brine discharge is a big issue. Membrane distillation (MD) has been proposed to solve this problem by significantly increasing the water recovery ratio, and recovering minerals. However, membranes with high hydrophobicity targeting for MD, particularly for vacuum membrane distillation (VMD) are still scarce. Hyflon AD is a novel candidate for fabricating membranes for MD. In this paper, the effects of membrane fabrication parameters, such as coating time, heat treatment and pre-filling were investigated and optimized. Membrane morphology, mechanical properties and VMD performance of the composite membranes were tested. The results showed that the hydrophobicity and elongation at break of the membrane were significantly improved after coating. The coating polymer concentration, coating time, heat treatment temperature and heat treatment time for the membrane coated by Hyflon AD40L and Hyflon AD40H, respectively were optimized. Monovalent alcohols can be excellent pre-filling agents to improve membrane performance. Separation performance of the membrane coated by Hyflon AD40H was better than that of the one coated by Hyflon AD40L.
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enhancing wetting resistance of poly vinylidene fluoride membranes for vacuum membrane distillation
Desalination, 2017Co-Authors: Yongxing Zhang, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Zhaoliang Cui, Shuaifei ZhaoAbstract:Abstract Composite membranes were fabricated by coating three types of highly hydrophobic perfluorinated copolymers (commercial name: Hyflon AD) on poly(vinylidene fluoride) hollow fibers. The membrane properties, including morphologies, pore sizes, porosities, liquid entry pressures (LEPs), mechanical strength, and separation performance (flux, rejection and wettability) in vacuum membrane distillation (VMD) were systematically characterized and investigated. The properties of the fabricated membranes, including pore sizes, pore size distributions, porosities, and LEPs were significantly affected by the viscosity of the coating polymer solution. Coating solutions with lower viscosities caused smaller pore sizes, narrower pore size distributions, lower porosities, higher LEPs and less flux decline in VMD. Particularly, LEP of the membrane coated with a lower viscosity solution (0.46 MPa) was two times higher than that of the uncoated membrane (0.23 MPa). As a result, the anti-wetting property of the composite membrane after coating was significantly enhanced compared with that of the original membrane. The coated composite hollow fiber membranes also showed improved hydrophobicity, mechanical strength and separation performance (water flux and salt rejection). The water contact angle of the membrane increased from 94 to 145° after coating with a lower viscosity solution.
Lida Ghassemzadeh - One of the best experts on this subject based on the ideXlab platform.
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evaluating chemical degradation of proton conducting perfluorosulfonic acid ionomers in a fenton test by solid state 19f nmr spectroscopy
Journal of Power Sources, 2011Co-Authors: Lida Ghassemzadeh, Klausdieter Kreuer, Joachim Maier, Klaus MullerAbstract:Abstract Chemical degradation and stability of perfluorosulfonic acid (PFSA) ionomers against radical attack were investigated by an (ex situ) Fenton test. Solid-state and solution NMR as well as ATR-FTIR studies were performed on the samples before and after the Fenton reaction. By changing the concentration of the Fenton's solution it is found that the metallic catalyst (Fe 2+ ) is a critical factor which may affect the solid-state NMR results. After adjusting the experimental conditions, i.e., by reducing the Fe 2+ concentration, it was possible to detect by solid-state 19 F NMR spectroscopy the structural changes of the perfluorosulfonic acid ionomers during the ex situ Fenton test. A comparative study was made on the degradation of Nafion and Hyflon Ion membranes which differ in the length of the side chains. It is shown that the Hyflon Ion membrane with shorter side chains is more stable against side chain attack, most probably because of the absence of an additional tertiary carbon in the side chain. At the same time, there is evidence for enhanced main chain degradation in membranes with unprotected backbone chain ends.
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chemical degradation of proton conducting perflurosulfonic acid ionomer membranes studied by solid state nuclear magnetic resonance spectroscopy
Journal of Power Sources, 2009Co-Authors: Lida Ghassemzadeh, Klausdieter Kreuer, Joachim Maier, M Marrony, R Barrera, Klaus MullerAbstract:Abstract The degradation of two different types of perfluorinated polymer membranes, Nafion and Hyflon Ion, has been examined by solid-state 19 F and 13 C NMR spectroscopy. This spectroscopic technique is demonstrated to be a valuable tool for the study of the membrane structure and its alterations after in situ degradation in a fuel cell. The structural changes in different parts of the polymers are clearly distinguished, which provides unique insight into details of the degradation processes. The experimental NMR spectra prove that degradation mostly takes place within the polymer side chains, as reflected by the intensity losses of NMR signals associated with SO 3 H, CF 3 , OCF 2 and CF groups. The integral degree of degradation is found to decrease with increasing membrane thickness while for a given thickness, Hyflon Ion appears to degrade less than Nafion.
Haiqing Lin - One of the best experts on this subject based on the ideXlab platform.
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Dioxolane-Based Perfluoropolymers with Superior Membrane Gas Separation Properties
Macromolecules, 2018Co-Authors: Milad Yavari, Haiqing Lin, Minfeng Fang, Hien Nguyen, Timothy C Merkel, Yoshiyuki OkamotoAbstract:Glassy perfluoropolymers have become an exciting materials platform for membrane gas separation as they define the upper bounds for some gas separations, such as He/H2, He/CH4, and N2/CH4. However, due to the difficulty in synthesis, only a few glassy perfluoropolymers are commercially available, including Teflon AF and Hyflon AD derived from dioxoles and Cytop derived from dihydrofuran. In this study, two perfluoropolymers based on dioxolanes, poly(perfluoro-2-methylene-1,3-dioxolane) (poly(PFMD)) and poly(perfluoro-2-methylene-4-methyl-1,3-dioxolane) (poly(PFMMD)), were synthesized by radical polymerization and characterized thoroughly for physical properties such as glass transition temperature (Tg), d-spacing between polymer chains, and fractional free volume (FFV). The gas permeability and solubility were determined at 35 °C for a series of pure gases in these perfluorodioxolanes and compared with the commercial perfluoropolymers. Poly(PFMD) and poly(PFMMD) exhibit separation properties of He/H2, He/...
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Dioxolane-Based Perfluoropolymers with Superior Membrane Gas Separation Properties
2018Co-Authors: Milad Yavari, Haiqing Lin, Minfeng Fang, Hien Nguyen, Timothy C Merkel, Yoshiyuki OkamotoAbstract:Glassy perfluoropolymers have become an exciting materials platform for membrane gas separation as they define the upper bounds for some gas separations, such as He/H2, He/CH4, and N2/CH4. However, due to the difficulty in synthesis, only a few glassy perfluoropolymers are commercially available, including Teflon AF and Hyflon AD derived from dioxoles and Cytop derived from dihydrofuran. In this study, two perfluoropolymers based on dioxolanes, poly(perfluoro-2-methylene-1,3-dioxolane) (poly(PFMD)) and poly(perfluoro-2-methylene-4-methyl-1,3-dioxolane) (poly(PFMMD)), were synthesized by radical polymerization and characterized thoroughly for physical properties such as glass transition temperature (Tg), d-spacing between polymer chains, and fractional free volume (FFV). The gas permeability and solubility were determined at 35 °C for a series of pure gases in these perfluorodioxolanes and compared with the commercial perfluoropolymers. Poly(PFMD) and poly(PFMMD) exhibit separation properties of He/H2, He/CH4, H2/CH4, H2/CO2, and N2/CH4 near or above the upper bounds in Robeson’s plots, and superior to the commercial perfluoropolymers, despite their similar Tg and FFV. The underlying reasons for the superior gas separation properties in these dioxolane-based perfluoropolymers are discussed
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geometric restriction of gas permeance in ultrathin film composite membranes evaluated using an integrated experimental and modeling approach
Industrial & Engineering Chemistry Research, 2017Co-Authors: Lingxiang Zhu, Milad Yavari, Weiguang Jia, Edward P Furlani, Haiqing LinAbstract:Gas permeation through ultrathin film composite (uTFC) membranes can be restricted by the pore size and porosity of the porous supports, resulting in a reduction in permeance. Although this geometric restriction has been demonstrated using empirical and computational models, a systematic experimental validation of the models is still lacking. This study addresses the gap by preparing a series of uTFC membranes comprising glassy perfluoropolymers (such as Teflon AF1600 and Hyflon AD80) as selective layers on top of a commercial poly(ether sulfone) (PES) microporous support and investigating the effects of the surface morphology and selective layer thickness on the gas permeance. The geometric restriction resulting from the porous support becomes more severe as the selective layer becomes thinner. For example, the PES support decreased the gas permeance of a 100-nm-thick Hyflon AD80 film by as much as 42%. The experimental data agreed well with the modeling results, which convincingly confirms that porous s...
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gas permeation in thin films of high free volume glassy perfluoropolymers part i physical aging
Polymer, 2014Co-Authors: Rajkiran R Tiwari, Haiqing Lin, Zachary P Smith, Benny D Freeman, Donald R PaulAbstract:Abstract Physical aging of both thick and thin films of “high free-volume” glassy perfluoropolymers was studied by monitoring changes in pure gas permeability of O 2 , N 2 and CH 4 . All permeability measurements were done at a fixed temperature of 35 °C for more than 1000 h of aging. Two grades of perfluoropolymers, Teflon AF and Hyflon AD, having different comonomer structures but with similar comonomer ratios were studied to understand the effect of comonomer type and content on the aging behavior. The effect of casting process (solution vs. spin coating) and solvent type (vapor pressure and boiling point) had a significant effect on the absolute permeability of both thick and thin films; however, the aging rates were more affected by thickness and solvent type rather than the casting process for similar thicknesses. After 1000 h of aging, the relative permeability for thin films of Teflon AF 2400 was decreased by 27% compared to only 10% for thick films prepared from Novec 7500 solvent. Teflon AF, which has a higher fractional free volume (FFV) than Hyflon AD, is believed to undergo significant aging well before the initial permeability measurement could be made (after ∼ 1 h of aging) and, therefore, Teflon AF materials showed a lower decrease in relative permeability compared to Hyflon AD for the same aging time. The comonomer type and content has a significant effect on the permeability; the initial absolute oxygen permeability for AF 2400 was an order of magnitude higher compared to AD 60. The physical aging of thin films of the various glassy perfluoropolymers was also tracked by recording changes in the refractive index and thickness with time by ellipsometry. The ellipsometry data also confirmed higher aging rates in Hyflon AD compared to Teflon AF materials. The volumetric aging rate, obtained from the change in the refractive index using the Lorentz–Lorenz equation, and the permeability reduction rate from the ( P 1000 h / P 1 h ) ratio showed an excellent linear correlation. The ( P 1000 h / P 1 h ) ratio also showed a stronger correlation with ( T g −35) °C than with FFV.
Zhaoliang Cui - One of the best experts on this subject based on the ideXlab platform.
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enhanced fouling and wetting resistance of composite Hyflon ad poly vinylidene fluoride membrane in vacuum membrane distillation
Separation and Purification Technology, 2019Co-Authors: Yongxing Zhang, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Zhaoliang Cui, Jingyi Cao, Shouyong Zhou, Shuaifei ZhaoAbstract:Abstract Membrane fouling and pore wetting are the key problems affecting the separation performance of membrane distillation (MD). They can become more severe with increasing the operation time, which will have a negative impact on heat and mass transfers. In this paper, solutions containing CaCO3, humid acid (HA), and/or silica sols (SiO2) were used as the feed with different Hyflon AD/polyvinylidene fluoride (PVDF) composite membranes for vacuum membrane distillation (VMD). The evolutions of flux and salt rejection during the concentration process were examined, and the membranes with different properties were compared. The results showed that the original membrane was more prone to be fouled and wetted even at low concentration factors. In the single-component systems, CaCO3 impacts the membrane performance most severely. With the hybrid component solutions, the flux declines for the composite membranes were lower than that of the original membrane. Compared with the single-component systems, the practical situation is more likely close to the hybrid-component system where fouling and wetting were easier to happen. Overall, the composite membranes showed enhanced fouling and wetting resistance and maintained stable salt rejections. Particularly, the composite membrane with smaller pore sizes (M-40L) performed best among all the membranes, suggesting its high potential for practical VMD applications.
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optimization of novel composite membranes for water and mineral recovery by vacuum membrane distillation
Desalination, 2017Co-Authors: Zhaoliang Cui, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Yongxing Zhang, Shuaifei ZhaoAbstract:Abstract In mining industries, the process combining ultrafiltration (UF) and reverse osmosis (RO) is often used for wastewater treatment, but RO brine discharge is a big issue. Membrane distillation (MD) has been proposed to solve this problem by significantly increasing the water recovery ratio, and recovering minerals. However, membranes with high hydrophobicity targeting for MD, particularly for vacuum membrane distillation (VMD) are still scarce. Hyflon AD is a novel candidate for fabricating membranes for MD. In this paper, the effects of membrane fabrication parameters, such as coating time, heat treatment and pre-filling were investigated and optimized. Membrane morphology, mechanical properties and VMD performance of the composite membranes were tested. The results showed that the hydrophobicity and elongation at break of the membrane were significantly improved after coating. The coating polymer concentration, coating time, heat treatment temperature and heat treatment time for the membrane coated by Hyflon AD40L and Hyflon AD40H, respectively were optimized. Monovalent alcohols can be excellent pre-filling agents to improve membrane performance. Separation performance of the membrane coated by Hyflon AD40H was better than that of the one coated by Hyflon AD40L.
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enhancing wetting resistance of poly vinylidene fluoride membranes for vacuum membrane distillation
Desalination, 2017Co-Authors: Yongxing Zhang, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Zhaoliang Cui, Shuaifei ZhaoAbstract:Abstract Composite membranes were fabricated by coating three types of highly hydrophobic perfluorinated copolymers (commercial name: Hyflon AD) on poly(vinylidene fluoride) hollow fibers. The membrane properties, including morphologies, pore sizes, porosities, liquid entry pressures (LEPs), mechanical strength, and separation performance (flux, rejection and wettability) in vacuum membrane distillation (VMD) were systematically characterized and investigated. The properties of the fabricated membranes, including pore sizes, pore size distributions, porosities, and LEPs were significantly affected by the viscosity of the coating polymer solution. Coating solutions with lower viscosities caused smaller pore sizes, narrower pore size distributions, lower porosities, higher LEPs and less flux decline in VMD. Particularly, LEP of the membrane coated with a lower viscosity solution (0.46 MPa) was two times higher than that of the uncoated membrane (0.23 MPa). As a result, the anti-wetting property of the composite membrane after coating was significantly enhanced compared with that of the original membrane. The coated composite hollow fiber membranes also showed improved hydrophobicity, mechanical strength and separation performance (water flux and salt rejection). The water contact angle of the membrane increased from 94 to 145° after coating with a lower viscosity solution.
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preparation of Hyflon ad60 pvdf composite hollow fiber membranes for vacuum membrane distillation
Separation and Purification Technology, 2016Co-Authors: Daqing Tong, Enrico Drioli, Xiaozu Wang, Zhaohui Wang, Mohammad Ali, Yong Wang, Zhaoliang CuiAbstract:Abstract Hydrophobic membrane is desired to avoid pore wetting phenomenon in membrane distillation (MD). In the present paper, highly hydrophobic Hyflon AD60/PVDF composite hollow fiber membranes were prepared by coating a copolymer (Hyflon AD60) of tetrafluoroethylene (TFE) and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD) on poly(vinylidene fluoride) (PVDF) membranes. The effects of Hyflon AD60 concentration, coating time, heat-treatment temperature and heat-treatment time on the structures and performances of Hyflon AD60/PVDF composite hollow fiber membranes in vacuum membrane distillation (VMD) process were investigated. The results show that the hydrophobicity of PVDF hollow fiber membrane was significantly improved by coating Hyflon AD60. The optimized Hyflon AD60 concentration, coating time, heat-treatment temperature and heat-treatment time were 0.1 wt%, 10–20 min, 40–50 °C and 9 h, respectively. Employing NaCl solution with concentration of 35 g × L−1, under a vacuum of 0.09 MPa and feed temperature of 70 °C, the water flux and salt rejection of the composite hollow fiber membrane in VMD process reached to approximately 10 kg × m−2 × h−1 and higher than 99.9 %, respectively, and kept stable, indicating that Hyflon AD60/PVDF composite membrane is an excellent candidate for operation in VMD operation.