Preparation and characterization of novel chitosan‐based mixed matrix membranes resistant in alkaline media

In this work, mixed matrix membranes (MMMs) based on chitosan (CS) and different fillers (room temperature ionic liquid [emim][OAc] (IL), metallic Sn powder, layered titanosilicate AM‐4 and layered stannosilicate UZAR‐S3) were prepared by solution casting. The room temperature electrical conductivity and electrochemical response in strong alkaline medium were measured by electrochemical impedance spectroscopy and cyclic voltammetry (CV). The ionic conductivity of pure CS membranes was enhanced, from 0.070 to 0.126 mS cm^?1, for the pristine CS and Sn/CS membranes, respectively, as a function of the hydrophilic nature of the membrane and the coordination state of Sn. This hydrophilic and charge nature was corroborated by water uptake measurements, where only the introduction of IL in the CS membrane led to a water uptake of 3.96 wt %, 20 or 30 times lower than the other membranes. Good thermal and chemical stability in alkaline media were observed by thermogravimetric analyses and X‐ray photoelectron spectroscopy analyses, respectively, and good interaction between CS and the fillers observed by X‐ray diffraction, scanning electron microscopy and CV. Thus, thin CS‐based MMMs (40–139 µm), resistant in high alkaline media, show higher conductivity than pure CS membranes, especially those fillers containing tin, and although the electrochemical performance is lower than commercially available anion‐exchange membranes they have potential in pervaporation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42240.     

Chitosan/polyvinylpyrrolidone‐silica hybrid membranes for pervaporation separation of methanol/ethylene glycol azeotrope

Chitosan (CS)/polyvinylpyrrolidone (PVP)‐silica hybrid membranes are prepared to separate the methanol/ethylene glycol (EG) azeotrope. These hybrid membranes are formed in semi‐interpenetrating network structure at the molecular scale via sol‐gel reactions between CS and tetraethoxysilane (TEOS). The physico‐chemical property and morphology of the as‐prepared membranes are investigated in detail. They have lower crystallinity, higher thermal stability, and denser structure than the pristine CS membrane and its blending counterpart. The as‐prepared hybrid membranes demonstrate excellent performances and a great potential in pervaporation separation of methanol/EG. Silica‐hybridization depressed the swelling degree of membranes in the azeotrope, and remarkably enhanced methanol sorption selectivity. The membrane containing 7.77 wt % PVP and 14.52 wt % TEOS has a permeation flux of 0.119 kg m^?2 h^?1 and separation factor of 1899. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modified polydimethylsiloxane/polystyrene blended IPN pervaporation membrane for ethanol/water separation

In this article a modified polydimethylsiloxane (PDMS) blended polystyrene (PS) interpenetrating polymer network (IPN) membranes supported by Teflon (polytetrafluoroethylene) ultrafiltration membrane were prepared for the separation of ethanol in water by pervaporation application. The relationship between the surface characteristics of the surface‐modified PDMS membranes and their permselectivity for aqueous ethanol solutions by pervaporation are discussed. The IPN supported membranes were prepared by sequential IPN technique. The IPN supported membrane were tested for the separation performance on 10 wt % ethanol in water and were characterized by evaluating their mechanical properties, swelling behavior, density, and degree of crosslinking. The results indicated that separation performance, mechanical properties, density, and the percentage of swelling of IPN membranes were influenced by degree of crosslink density. Depending on the feed temperature, the supported membranes had separation factors between 2.03 and 6.00 and permeation rates between 81.66 and 144.03 g m^?2 h^?1. For the azeotropic water–ethanol mixture (10 wt % ethanol), the supported membrane had at 30°C a separation factor of 6.00 and a permeation rate of 85 g m^?2 h^?1. Compared to the PDMS supported membranes, the PDMS/PS IPN supported blend membrane ones had a higher selectivity but a somewhat lower permeability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of 4A zeolite‐filled mixed matrix membranes for pervaporation dehydration of isopropyl alcohol

Sodium carboxymethylcellulose/poly (vinyl alcohol) mixed matrix membranes filled with different amounts 4A zeolite (0, 5, 10, 15, and 20 wt %) were prepared by solution casting method. Prepared membranes were crosslinked with GA and used for pervaporation dehydration of isopropyl alcohol of different feed mixtures at 35°C. On increment in zeolite content in the membrane it was found the improvement in the performance of the membrane, due to its hydrophilic nature and molecular sieving effect in addition to its favorable interaction with hydrophilic sodium carboxymethylcellulose and polyvinyl alcohol. The structure and chemical constituents of the MMM's were investigated by attenuated total reflectance Fourier transform infrared spectroscopy. Thermal stability of the membranes was assessed by DSC and TGA techniques. Crystallinity of the membranes was assessed using X‐ray diffraction, and the morphological properties were assessed by scanning electron microscopy. Mechanical properties were also carried out to determine the tensile strength and % of elongation at break using universal testing machine. It was found that the mechanical strength increases with increase in the zeolite content upto 15 wt % of zeolite with an optimum tensile strength of 113.31 N/mm². Pervaporation was carried out to asses the membrane performance, the highest flux and selectivity obtained is 0.584 kg/m²/h and 6945 for NaCMCA20 and NaCMCA15, respectively, for a feed composition containing 17.5 and 10 wt % of water in the feed and further swelling studies also supporting the pervaporation results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mixed matrix membranes of sodium alginate and poly(vinyl alcohol) for pervaporation dehydration of isopropanol at different temperatures

Mixed matrix membranes of sodium alginate (NaAlg) and poly(vinyl alcohol) (PVA) containing 5 and 10 wt.% silicalite-1 particles were fabricated by solution casting method and the cured membranes were crosslinked with glutaraldehyde. These membranes were used in pervaporation (PV) dehydration of isopropanol at 30, 40, 50 and 60 °C. Membrane morphology was studied by scanning electron microscopy and universal testing machine to assess their mechanical strengths. Swelling results of the pristine and mixed matrix membranes were correlated with their PV performances. Selectivities of the mixed matrix membranes of NaAlg were 11,241 and 17,991 with the fluxes of 0.039 and 0.027 kg/m² h, respectively, for 5 and 10 wt.% silicalite-1 loadings. Corresponding values for mixed matrix membranes of PVA were 1295 and 2241, and 0.084 and 0.069 kg/m² h, respectively, for 10 wt.% water-containing feed at 30 °C. Pristine membranes of NaAlg and PVA exhibited lower selectivities of 653 and 77 with increased fluxes of 0.067 and 0.095 kg/m² h, respectively. From the temperature dependence of flux and diffusivity data with 10 wt.% water-containing feed, Arrhenius plots were constructed to compute heat of sorption, ΔH_s values. Mixed matrix membranes of NaAlg were better than PVA mixed matrix membranes at all compositions (10-40 wt.%) of water. Molecular dynamics (MD) simulation was employed to compute the interfacial interaction energies of NaAlg and PVA polymers with silicalite-1 filler; also sorption of liquid molecules was computed. Simulated diffusivities compared well with the experimental data. Thermodynamic treatment of sorption, diffusion and permeation processes was attempted based on the Flory-Huggins theory to explain the PV performances of the membranes.     

Preparation and characterization of Silicalite‐1/PDMS surface sieving pervaporation membrane for separation of ethanol/water mixture

To improve the pervaporation performance of Silicalite‐1/PDMS composite membrane by adding a small amount of Silicalite‐1 zeolite, novel Silicalite‐1/PDMS surface sieving membranes (SSMs) were prepared by attaching Silicalite‐1 particles on the PDMS membrane surface. The obtained membranes and traditional mixed‐matrix membranes (MMMs) were characterized by SEM, XRD, TGA, FT‐IR, and pervaporation separation of ethanol–water mixture. Effects of Silicalite‐1 particles content, feed temperatures, and feed compositions on the separation performance were discussed. From the cross‐section view SEM images of SSMs, a two‐layer structure was observed. The thickness of the Silicalite‐1 layer was about 300 nm to 2 μm. The TGA analysis indicates that the zeolite concentration in 3 wt % SSM is lower than 10 wt % MMMs. In the ethanol/water pervaporation experiment, the separation factor of Silicalite‐1/PDMS SSMs increased considerably compared with pure PDMS membrane. When the suspensions concentrations of Silicalite‐1 particles reached 3 wt %, the separation factor was about 217% increase over pure PDMS membrane and 52.9% increase over 10 wt % Silicalite‐1/PDMS MMMs. As the ethanol concentration in the feed increases, the separation factor of SSMs increases, whereas permeation flux decreases. At the same time, with increasing operating temperature, the permeation flux of SSMs increased. The stability of SSMs at high temperature is better than the traditional MMMs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42460.     

Poly(ether sulfone) supported hybrid poly(vinyl alcohol)–maleic acid–silicone dioxide membranes for the pervaporation separation of ethanol–water mixtures

Microporous poly(ether sulfone) (PES) supported hybrid polymer–inorganic membranes were prepared by the crosslinking of poly(vinyl alcohol) (PVA), maleic acid (MA), and SiO₂ via an aqueous sol–gel route and a solution‐casting method. The membrane performance was tested for the pervaporation separation of ethanol–water mixtures from 20 to 60 °C with a feed ethanol concentration of 96 wt %. The membrane characterization results reveal that different SiO₂ loadings affected the crystallinity and roughness of the membranes. The PVA–MA–SiO₂ membrane containing 10 wt % SiO₂ showed that SiO₂ nanoparticles were well dispersed within the polymer matrix; this resulted in significant enhancements in both the flux and selectivity. The membrane achieved a high water permeability of 1202 g·μm·m^?2 h^?1 kPa^?1 and a selectivity of 1027 for the separation of a 96 wt % ethanol‐containing aqueous solution. This enhanced membrane performance might have been due to the dense crosslinking membrane network, increased free volume, and uniform distribution of SiO₂ nanoparticles. Both the water and ethanol fluxes increased with the feed water concentration and temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44839.     

Polyamide–imide membranes with surface immobilized cyclodextrin for butanol isomer separation via pervaporation

A novel cyclodextrin (CD) derivative, m‐xylenediamine‐β‐cyclodextrin (m‐XDA‐β‐CD), has been synthesized and used to graft β‐CD on membrane surface for the pervaporation separation of butanol isomers. The reaction mechanisms for the m‐XDA‐β‐CD synthesis and the membrane surface grafting are confirmed by FTIR and TGA. The as‐fabricated novel CD‐grafted polyamide‐imide (PAI) membranes show homogeneous morphology and significant improved separation performance as compared to the unmodified PAI membranes and PAI/CD mixed matrix membranes made of physical blends. The effects of chemical modification time and dope concentration on the asymmetric membrane have been studied. The optimal separation performance can be found with the CD‐grafted PAI membrane cast from a 22 wt % dope concentration, which exhibits a total butanol flux of 15 g/m²/h and a separation factor of 2.03. This newly developed membrane with surface‐immobilized CD may open new perspective for the development of next‐generation high‐performance pervaporation membranes for liquid separations. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Pervaporation separation of ethanol/water mixture using modified zeolite filled PDMS membranes

In this article, the composite polydimethylsiloxane (PDMS) membranes supported by cellulose acetate (CA) microfiltration membrane were successfully prepared by adding modified zeolite particles with a silane coupling agent, NH₃–C₃H₆–Si(OC₂H₅)₃. The sorption and diffusion behaviors of ethanol and water in the films were studied. The results showed that with the increase in the modified zeolite content, the solubility selectivity increased, but the diffusion selectivity first increased, then decreased. The effects of modified zeolite content and feed temperature on the pervaporation performance of the composite membranes in 10 wt % ethanol/water mixture were also investigated. When modified zeolite loading was 20 wt %, for 10 wt % ethanol/water mixture at 40°C, the permeate flux was 348.7 g·m^?2·h^?1, the separation factor was 14.1, and the permeate separate index was 4568, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41897.     

Cellulose–poly(acrylamide–acrylic acid) interpenetrating polymer network membranes for the pervaporation of water–ethanol mixtures. II. Effect of ionic group contents and cellulose matrix modification

The separation properties in the dehydration of a water–ethanol mixture and the swelling behavior of interpenetrating polymer network (IPN) pervaporation membranes based on a cellulose or cellulose–hydroxyethyl cellulose (HEC) matrix and poly(acrylamide and/or acrylic acid) were investigated depending on the ionic acrylate groups content (γ) in synthetic polymer chains (0–100 mol %), the HEC content in the matrix (0–50 wt %), and the temperature (25–60°C). The separation factor (α), permeation rate (P), and separation index (αP) significantly improved with increasing γ values only for the separation of concentrated ethanol solutions (～86 wt %). For more dilute solutions of ethanol (～46 wt %), the P and αP values also increased but no considerable increase in α was observed. All types of membranes based on the cellulose matrix were characterized by a drastic decrease in the values of P at [EtOH] ≥90 wt % and, as a result, a decrease in the separation index (kg m^?2 h^?1) from ～2000 (for 86 wt % EtOH, 50°C) to ～240 (for 95 wt % EtOH, 50°C), which correlates with a decrease in the degree of membrane swelling. The modification of the cellulose matrix by introducing HEC into it makes it possible to increase considerably the membrane swelling in concentrated EtOH solutions and, hence, the αP value to ～760 (95 wt % EtOH, 50°C). All types of IPN membranes exhibit a marked increase in both α and P when the temperature increases from 25 to 60°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1452–1460, 2001     

Pervaporation characteristics and structure of poly(vinyl alcohol)/poly(ethylene glycol)/tetraethoxysilane hybrid membranes

Poly(vinyl alcohol) (PVA) blended with poly(ethylene glycol) (PEG) was crosslinked with tetraethoxysilane (TEOS) to prepare organic–inorganic PVA/PEG/TEOS hybrid membranes. The membranes were then used for the dehydration of ethanol by pervaporation (PV). The physicochemical structure of the hybrid membranes was studied with Fourier transform infrared spectra (FT‐IR), wide‐angle X‐ray diffraction WXRD, and scanning electron microscopy (SEM). PVA and PEG were crosslinked with TEOS, and the crosslinking density increased with increases in the TEOS content, annealing temperature, and time. The water permselectivity of the hybrid membranes increased with increasing annealing temperature or time; however, the permeation fluxes decreased at the same time. SEM pictures showed that phase separation took place in the hybrid membranes when the TEOS content was greater than 15 wt %. The water permselectivity increased with the addition of TEOS and reached the maximum at 10 wt % TEOS. The water permselectivity decreased, whereas the permeation flux increased, with an increase in the feed water content or feed temperature. The hybrid membrane that was annealed at 130°C for 12 h exhibited high permselectivity with a separation factor of 300 and a permeation flux of 0.046 kg m^?2 h^?1 in PV of 15 wt % water in ethanol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Pervaporation dehydration of water/ethanol/ethyl acetate mixtures using poly(vinyl alcohol)–silica hybrid membranes

The novel organic–inorganic hybrid membranes were prepared from poly(vinyl alcohol) (PVA) and vinyltriethoxysilane (VTES). They were characterized using Fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and contact angle metering. The as‐prepared membranes are formed at a molecular scale at a low VTES content. Aggregations in the surface of the as‐prepared membranes were clearly evident above 18.43 wt % VTES loading. The introduction of VTES into the PVA matrix resulted in a decrease in the crystalline and an increase in compactness and thermal stability of the as‐prepared membranes. Silica hybridization reduced the swelling of the as‐prepared membranes in water/ethanol/ethyl acetate mixtures, decreased the permeation flux, and remarkably enhanced water permselectivity in pervaporation dehydration of ethanol/ethyl acetate aqueous solution. The hybrid membrane with 24.04 wt % VTES has the highest separation factor of 1079 and permeation flux of 540 g m^?2 h^?1. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mixed matrix membranes of Matrimid 5218 loaded with zeolite 4A for pervaporation separation of water–isopropanol mixtures

Mixed matrix membranes were prepared by incorporating zeolite 4A into polyimide of Matrimid 5218 using solution-casting technique. The fabricated membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA). It was found that the higher annealing temperature of 250 °C is more favorable to improve adhesion between zeolite and polymer phases. Effects of different parameters such as temperature (30–60 °C), water content in feed (10–40 wt.%), zeolite loading (0–15 wt.%) and polymer content (10 and 15 wt.%) on pervaporation dehydration of isopropanol were studied. Sorption studies were carried out to evaluate degree of swelling of the membranes in feed mixtures of water and isopropanol. The experimental results showed that both pervaporation flux and selectivity increase simultaneously with increasing the zeolite content in the membranes. The membrane containing Matrimid 5218 (10 wt.%)–zeolite 4A (15 wt.%) exhibits the highest separation factor (α) of 29,991 with a substantial permeation flux (J) of 0.021 kg/m² h at 30 °C for 10 wt.% of water in the feed. The PV performance was also studied in term of pervaporation separation index (PSI). Permeation flux was found to follow the Arrhenius trend over the investigated temperature range.     

Dehydration of 2‐Butanol by Pervaporation Through Blend Membranes of Chitosan and Hydroxy Ethyl Cellulose

Abstract

Blend membranes of chitosan (CS) and hydroxyethylcellulose (HEC) were synthesized and cross‐linked with glutaraldehyde for the separation of 2‐butanol/water mixtures. The blends were characterized by fourier transform infrared (FTIR) spectroscopy and wide‐angled X‐ray diffraction (WAXD) to assess the intermolecular interactions and occurrence of cross‐linking, respectively. The pervaporation performance was evaluated by varying experimental parameters such as feed composition, membrane thickness, and permeate pressure and found to be promising. Sorption studies were conducted to evaluate affinity and degree of swelling of both the unmodified and cross‐linked blend membranes in pure as well as binary mixtures of the two liquids. The blends were found to have good potential for breaking the aqueous azeotrope of 2‐butanol (77 wt.%). Upon cross‐linking, the blend membranes exhibited a substantial improvement in performance. Amongst the various blend combinations used for the dehydration studies, the membrane constituting 70 wt.% of CS and 30 wt.% HEC yielded a flux of 2.1 kg/m² · h · 10 µm and a selectivity of 554, which was optimum.     

Effects of mixed solvents and PVDF types on performances of PVDF microporous membranes

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 MPa^1/2 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     

Modified poly(vinyl alcohol)/chitosan blended membranes for isopropanol dehydration via pervaporation: Synthesis optimization and modeling by response surface methodology

Box–Behnken (BB) design of response surface methodology (RSM) was effectively applied to optimize fabrication conditions of modified poly(vinyl alcohol) (PVA) and chitosan (CS) blended pervaporation (PV) membranes. The PVA/CS membranes were crosslinked either by chemical reaction with glutaraldehyde (GA) or by heat‐treating at different temperatures. The main objectives were to determine the optimal levels of fabricating parameters and also to investigate interactions among the variables. CS content in the blended membranes, concentration of crosslinking agent and heat‐treating temperature were the fabrication parameters, the main effects and interaction effects of which on membrane structure and PV performance toward isopropanol (IPA)/water dehydration were investigated, and for which regression models were established. The modified PVA/CS blended membranes were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) as well as X‐ray diffraction (XRD). It was found that the CS content is the most significant factor influencing flux and separation factor among the three studied variables and the experimental results are in excellent accordance with predicted values from the developed RSM regression models. The RSM results indicated that under preparation conditions of 80 wt % CS in the blended membrane, 0.58 wt % GA concentration, and 77 °C heat‐treating temperature, the maximum separation factor of 5222.8 and the normalized flux of 9.407 kg µm/m²h can be acquired with feed content of 85 wt % IPA at 25 °C, showing that the prepared membrane is highly efficient for PV dehydration of IPA. The models were satisfactorily validated against experimental data. Furthermore, the optimum membrane presents excellent separation performance at different feed compositions and temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44587.     

High‐performance PDMS membranes for pervaporative removal of VOCs from water: The role of alkyl grafting

To improve the pervaporation performance of PDMS membrane, alkyl groups with different chain length were grafted into PDMS matrix. The prepared membranes were characterized by ATR‐IR, DSC, TGA, PALS, and tensile testing. The effects of alkyl grafting on pervaporation performance of PDMS membrane were investigated in separation of ethyl acetate/water mixture. Experimental results show that the separation factor of PDMS membrane is largely improved by alkyl grafting because of the enhanced preferential sorption of ethyl acetate, and this improvement depends on alkyl grafting ratio and alkyl chain length. The total flux of PDMS membrane reduces after alkyl grafting owing to the decreased free volume. When grafting ratio is above 6.9%, membrane grafted with shorter alkyl groups is preferred for pervaporation. The best pervaporation performance is achieved by 9% octyl grafted PDMS membranes with a separation factor of 592 and a total flux of 188 gm^?2 h^?1 in separation of 1% ethyl acetate/water mixture at 40 °C. Moreover, this octyl grafted PDMS membrane also exhibits excellent separation performance in removal of butyl acetate, methyl‐tert‐butyl ether, and n‐butanol from water. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43700.     

Mixed Matrix Silicone and Fluorosilicone/Zeolite 4A Membranes for Ethanol Dehydration by Pervaporation

The ability of homogeneous and mixed matrix membranes prepared using standard silicone rubber, poly(dimethylsiloxane) (PDMS), and fluorosilicone rubber, poly(trifluoropropylmethylsiloxane) (PTFPMS), to dehydrate ethanol by pervaporation was evaluated. Although PDMS is generally considered to be the benchmark hydrophobic membrane material in pervaporation, water/ethanol molar permselectivity of a pure PDMS membrane was found to be 0.89 for a feed containing 80/20 w/w ethanol/water at 50°C, indicating a slight selectivity for water. Fluorinated groups in PTFPMS improved the water-ethanol permselectivity to 1.85, but decreased the water permeability from 9.7 × 10^?12 kmol · m/m² · s · kPa in PDMS to 5.1 × 10^?12 kmol · m/m² · s · kPa (29,000 and 15,200 Barrer, respectively). These water permeabilities are attractive, particularly since the rubbery materials should not experience the steep declines in water permeability observed with most standard dehydration membranes as water concentration in the feed decreases. However, the water selectivity is lower than desired for most applications. Particles of hydrophilic zeolite 4A were loaded into both PDMS and PTFPMS matrices in an effort to boost water selectivity and further improve water permeability. Water-ethanol permselectivities as high as 11.5 and water permeabilities as high as 23.2 × 10^?12 kmol · m/m² · s · kPa were observed for the PTFPMS/zeolite 4A mixed matrix membranes?6 times higher than for the unfilled PTFPMS membrane.     

CuO‐filled aminomethylated polysulfone hybrid membranes for deep desulfurization

CuO‐filled aminomethylated polysulfone hybrid membranes were prepared for sulfur removal from gasoline. The as‐prepared membranes were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). The separation performance of the hybrid membranes was evaluated by pervaporation (PV) separation of n‐heptane/thiophene binary mixture. CuO‐filling leads to a decrease in permeation flux. The sulfur‐enrichment factor increased first and then decreased with increasing CuO loading, and it is worth noting that there is a rebound in enrichment factor above 8 wt % CuO loading. Influencing factors such as nitrogen content, feed temperature, sulfur content, and various hydrocarbons on membrane PV performance were also evaluated. Permeation flux of 23.9 kg·μm·m^?2·h^?1 and sulfur‐enrichment factor of 3.9 can be achieved at 4 wt % CuO loading in PV of n‐heptane/thiophene binary mixture with 1500 μg·g^?1 sulfur content. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3718–3725, 2013     

Tubular composite PVA ceramic supported membrane for bio-ethanol production

Thin polyvinyl alcohol (PVA) layers loaded with fumed silica were coated on porous ceramic supports. Scanning electron microscope (SEM) was used to characterize the ceramic-supported thin PVA active layers and the effects of coating gel PVA concentration on thickness and density of the active layers were investigated. Pervaporation (PV) dehydration of 90 wt.% ethanol was performed at temperatures of 30, 45 and 60 °C. The values of water flux (0.05–2.92 kg/m² h) and selectivity (3–180) exceed typical values obtained for pure PVA membranes. Besides the pervaporation separation index (PSI) varies from 5.84 to 82.81. Compared to pure PVA membrane with maximum PSI of 47.2, the pervaporation performance was significantly improved. The best separation performance was obtained using the membrane prepared from 5 wt.% PVA solution containing 6 wt.% fumed silica and at pervaporation temperature of 45 °C with permeation flux of 1.69 kg/m² h, and selectivity of 50. The highest permeation flux, selectivity and PSI was 2.92 kg/m² h, 180 and 82.81, obtained at 60, 30 and 45 °C, respectively, while using membranes loaded with 8, zero and 6 wt.% of fumed silica in PVA membrane prepared from 5, 10 and 5 wt.% PVA solutions, respectively. The novel ceramic support increased mechanical strength of the membrane and protected the ultrathin polymeric top active layer under aggressive operating conditions, especially high pressure gradient across the membrane. Incorporation of fumed silica also resulted in higher water permeation flux. Due to these results, the synthesized membranes are suitable for ethanol purification in industrial scales.