Pervaporation separation of binary organic-aqueous liquid mixtures using crosslinked poly(vinyl alcohol) membranes. IV. Methanol–water mixtures

The pervaporation separation of methanol–water (M/W) mixtures was carried out using crosslinked poly(vinyl alcohol) (PVA) membranes with the low molecular weight of poly(acrylic acid) (PAA) as the crossinking agent. The PVA/PAA ratio in the crosslinked membrane was 90/10, 85/15, and 80/20 by weight. The operating temperatures were 50, 60, and 70°C, and the compositions of methanol–water mixtures to be separated were 70/30, 80/20, 90/10, and 95/5 (M/W) solutions. In all cases, the PVA/PAA = 80/20 membrane showed the best results. For M/W = 90/10 solution, the separation factor, α_w/m = 465, and the permeation rate, 0.109 kg/m²h, at 70°C were obtained using the PVA/PAA = 80/20 menbrane. The permeation rate and the separation factor for M/W = 95/5 solution showed 0.033 kg/m²h and α_w/m = 2650, respectively, when PVA/PAA = 80/20 membrane was used. © 1996 John Wiley & Sons, Inc.     

Properties and pervaporation performance of poly(vinyl alcohol) membranes crosslinked with various dianhydrides

In this work, three dianhydrides with similar chemical structures, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), 4,4′‐oxydiphthalic anhydride (ODPA), and pyromellitic dianhydride (PMDA), are employed for the crosslinking modification of poly(vinyl alcohol) (PVA) membranes for ethanol dehydration via pervaporation. The changes in crosslinking degree, surface hydrophilicity, and glass‐transition temperature are investigated and compared. Compared to the pure PVA membrane, all crosslinked membranes show higher fluxes but lower separation factors, because of the higher fractional free volume and the lower hydrophilicity by the crosslinking of the PVA matrix, respectively. In addition, all crosslinked PVA membranes exhibit similar flux, and the separation factor presents a decreasing order of PVA/PMDA‐2 > PVA/ODPA‐2 > PVA/BTDA‐2, which is in the reverse order of their hydrophilicity, probably because of the reduction in the swelling resistance. With the PMDA content increasing from 0.01 to 0.04 mol/(kg PVA) in the PVA/PMDA crosslinked membranes, the crosslinking degree is enhanced and the hydrogen bonding is weakened, resulting in a flux increase from 120.2 to 190.8 g m^?2 h^?1, but the separation factor declines from 306 to 58. This work is believed to provide useful insight on the chemical modification of PVA membranes for pervaporation and other membrane‐based separation applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46159.     

Flux,antifouling and separation characteristics enhancement of nanocomposite polyethersulfone mixed-matrix membrane by embedding synthesized hydrophilic adipate ferroxane nanoparticles

Polyethersulfone (PES) nanofiltration (NF) membranes were prepared by blending of synthesized hydrophilic adipate ferroxane nanoparticles (AFNPs) as a novel multifunctional nanofiller via the phase inversion method. The water contact angle measurement indicated the higher hydrophilicity of the NF membranes. The water flux of the membranes improved significantly after the addition of AFNPs, from 10.4 to 32.2 kg/m²h. Antifouling characteristics of AFNPs/PES membranes were improved by increased hydrophilicity and decreased membrane surface roughness. The 0.6 wt% AFNPs/PES membrane exhibited the highest FRR (96%) and the lowest irreversible fouling resistance (6%). The nanofiltration performance of the prepared membranes was evaluated by dye removal and salt retention. The results proved the high dye removal capability of modified membranes (98% rejection) compared with the unfilled PES membrane (89% rejection). The salt retention sequence for membrane with 0.2 wt% of nanoparticles was Na₂SO₄ (70%)>MgSO₄ (60%)>NaCl (18%).     

Poly(vinyl alcohol)/carboxyl graphene mixed matrix membranes: High-power ultrasonic treatment for enhanced pervaporation performance

High-power ultrasonic treatment was conducted during the mixing process to obtain poly(vinyl alcohol) (PVA)/carboxyl graphene (CG) mixed matrix membranes (MMMs). Results from X-ray photoelectron spectrometer and thermogravimetric analysis confirmed the enhanced esterification reaction. The increased amorphous region and free volume were investigated by wide-angle X-ray diffraction and positron annihilation lifetime spectroscopy. Scanning electron microscope and atomic force microscope measurements suggested that ultrasonic could uniformly disperse CG in PVA polymer matrix. The mechanical properties and hydrophilicity of as-prepared membrane were enhanced due to ultrasonic treatment. The permeation flux and separation factor of PVA/CG-US membrane for 90 wt % ethanol aqueous solution were 0.79 kg m⁻² h⁻¹ and 860, respectively. For methanol (15 wt %)/methyl tert-butyl ether mixture, its permeation flux and separation factor were also increased significantly compared with membranes without ultrasonic treatment. Due to the simplicity of the ultrasonic process and the versatility of the inorganic fillers, this method may contribute to the design of various MMMs and extend the application of these membranes in different uses. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48526.     

Modification of poly(vinyl alcohol) membranes using sulfur-succinic acid and its application to pervaporation separation of water–alcohol mixtures

For the purposes of the water-selective membrane material development for pervaporation separation, we crosslinked poly(vinyl alcohol) (PVA) with sulfur-succinic acid (SSA), which contains —SO₃OH, by heat treatment and investigated the effect of the crosslinking density on the separation of water–alcohol mixtures by pervaporation technique. The crosslinking reaction between PVA and SSA was characterized through Fourier transform infrared spectroscopy and differential scanning calorimetry tests by varying the amount of the crosslinking agent, the reaction temperature, and the swelling measurements of each pure component. The separation performance of the water–methanol mixture is not good due to the existence of sulfonic acid, hydrophilic group, in the crosslinking agent. However, for the water–ethanol mixture, the flux of 0.291 kg/m²h and the separation factor of 171 were obtained at 70°C when PVA-crosslinked membrane containing 7 wt % SSA was used. The same membrane also showed flux of 0.206 kg/m²h and a separation factor of 1969 at the same operating temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1717–1723, 1998     

Pervaporation separation of water–isopropyl alcohol mixture by PVA/LiBr membrane

Hydrophilic polyvinyl alcohol membranes, modified by lithium bromide, were prepared with glutaraldehyde as a crosslinking reagent. The membranes were investigated for the pervaporation dehydration of a water–isopropyl systems. The effect of the feed temperature on permeation flux and membrane selectivity was studied. The characterization of modified membranes was performed using Fourier transform infrared spectroscopy (FT‐IR), differential scanning calorimeter (DSC) and X‐ray diffraction. It was observed that the crystallinity of membranes increased as lithium bromide was added to the polymer. High performance liquid chromatography (HPLC) was used to analyze water content and isopropyl alcohol in the feed and permeate samples The pervaporation tests also confirmed an enhancement in water permeability through adding LiBr to the polymer, because of the high hydrophilic properties of this salt. According to pervaporation experiments conducted at 50°C, the water flux increased from 0.1049 kg/ m² hr to 0.1114 kg/ m² hr as 0.5 wt% of LiBr was added to the polymer matrix. Furthermore, an addition of 1 wt% of LiBr compared to homogeneous PVA membrane increased selectivity from 76 to 779. POLYM. ENG. SCI., 59:E101–E111, 2019. © 2018 Society of Plastics Engineers     

Pervaporation performance and Transport phenomenon of PVA blend membranes for the separation of THF/water azeotropic mixtures

Summary Dense polymer membranes were made by mixing aqueous solutions of hydrophilic polymers poly(vinyl alcohol) (PVA) and polyethyleneimine (PEI) in different ratios for investigating the separation of Tetrahydrofuran (THF)/water azeotropic mixtures by pervaporation (PV). In order to gain a more detailed picture of the molecular transport phenomenon, we have performed sorption gravimetric experiments at 30 °C to compute diffusion, swelling, sorption and permeability coefficients of PVA/PEI membranes in the presence of THF and water. The membranes were found to have good potential for breaking the azeotrope of THF at 6% concentration of water. An increase in PVA content in the blend caused a reduction in the flux and an increase in selectivity. Among the blends tested in the study, the 5:1 PVA/PEI blend membrane showed the highest separation factor of 181.5, exhibited a flux of 1.28 kg/m²h for THF respectively at azeotropic feed composition.     

Dehydration of tetrahydrofuran by pervaporation using crosslinked PVA/PEI blend membranes

Dense blend membranes were prepared by blending hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(ethyleneimine) (PEI), which were then crosslinked by glutaraldehyde (GA) in a mixture of solvents under the catalysis of hydrochloric acid (HCl) for the dehydration of tetrahydrofuran (THF) by pervaporation. The effect of experimental parameters such as feed water concentration, permeate pressure, and membrane thicknesses on permeate parameters, i.e., flux and selectivity were determined with feed water concentration less than 40 wt %. The membranes were found to have good potential for breaking the azeotrope of 94 wt % THF with a flux of 1.072 and 0.376 kg/m² h for plane PVA/PEI and crosslinked PVA/PEI blend membrane, which exhibited high selectivity of 156 and 579 respectively. Selectivity was found to improve with decreasing feed water concentration and increasing membrane thickness, whereas flux decreased correspondingly. High permeate pressure causes a reduction in both flux and selectivity. These effects were clearly elucidated with the aid of the known relationship among plasticization effect, degree of swelling, permeate pressure, and feed water concentration. These blend membranes were also subjected to sorption studies to evaluate the extent of interaction and degree of swelling in pure as well as binary feed mixtures. Further ion exchange capacity studies were carried out for all the crosslinked and uncrosslinked membranes to determine the total number of interacting groups present in the membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1152–1161, 2006     

Polyvinyl alcohol/polysulfone (PVA/PSF) hollow fiber composite membranes for pervaporation separation of ethanol/water solution

Polysulfone (PSF) hollow fiber membranes were spun by phase‐inversion method from 29 wt % solids of 29 : 65 : 6 PSF/NMP/glycerol and 29 : 64 : 7 PSF/DMAc/glycol using 93.5 : 6.5 NMP/water and 94.5 : 5.5 DMAc/water as bore fluids, respectively, while the external coagulant was water. Polyvinyl alcohol/polysulfone (PVA/PSF) hollow fiber composite membranes were prepared after PSF hollow fiber membranes were coated using different PVA aqueous solutions, which were composed of PVA, fatty alcohol polyoxyethylene ether (AEO₉), maleic acid (MAC), and water. Two coating methods (dip coating and vacuum coating) and different heat treatments were discussed. The effects of hollow fiber membrane treatment methods, membrane structures, ethanol solution temperatures, and MAC/PVA ratios on the pervaporation performance of 95 wt % ethanol/water solution were studied. Using the vacuum‐coating method, the suitable MAC/PVA ratio was 0.3 for the preparation of PVA/PSF hollow fiber composite membrane with the sponge‐like membrane structure. Its pervaporation performance was as follows: separation factor (α) was 185 while permeation flux (J) was 30g/m²·h at 50°C. Based on the experimental results, it was found that separation factor (α) of PVA/PSF composite membrane with single finger‐void membrane structure was higher than that with the sponge‐like membrane structure. Therefore, single finger‐void membrane structure as the supported membrane was more suitable than sponge‐like membrane structure for the preparation of PVA/PSF hollow fiber composite membrane. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 247–254, 2005     

Preparation and performance of the novel PVDF ultrafiltration membranes blending with PVA modified SiO2 hydrophilic nanoparticles

In this study, PVA‐SiO₂ was synthesized by modifying silica (SiO₂) with polyvinyl alcohol (PVA), then a novel polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane was prepared by incorporating the prepared PVA‐SiO₂ into membrane matrix using the non‐solvent induced phase separation (NIPS) method. The effects of PVA‐SiO₂ particle on the properties of the PVDF membrane were systematically studied by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT‐IR), surface pore size, porosity, and water contact angle. The results indicated that with the addition of PVA‐SiO₂ particles in the PVDF UF membranes, membrane mean pore size increased from 80.06 to 126.00 nm, porosity improved from 77.4% to 89.1%, and water contact angle decreased from 75.61° to 63.10°. Furthermore, ultrafiltration experiments were conducted in terms of pure water flux, bovine serum albumin (BSA) rejection, and anti‐fouling performance. It indicated that with the addition of PVA‐SiO₂ particles, pure water flux increased from 70 to 126 L/m² h, BSA rejection increased from 67% to 86%, flux recovery ratio increased from 60% to 96%, total fouling ratio decreased from 50% to 18.7%, and irreversible fouling ratio decreased from 40% to 4%. Membrane anti‐fouling property was improved, and it can be expected that this work may provide some references to the improvement of the anti‐fouling performance of the PVDF ultrafiltration membrane. POLYM. ENG. SCI., 59:E412–E421, 2019. © 2018 Society of Plastics Engineers     

Pervaporation separation of water/alcohol mixtures through hydroxypropylated chitosan membranes

The present study investigated the pervaporation performance of novel hydroxypropylated chitosan (HPCS) membranes to separate water from an aqueous alcohol solution. Hydroxypropylated chitosan was prepared from the reaction of chitosan and propylene oxide. The results show that the separation factor decreases and the flux increases with increasing of the substitution degree of the hydroxypropylated chitosan membrane. Crosslinking with glutaraldehyde or treatment with Cu²⁺ can improve the pervaporation performance of modified chitosan membrane grately. The performance data indicate that the crosslinking hydroxypropylated chitosan membrane treated with Cu²⁺ is an excellent pervaporation membrane for the separation of alcohol–water mixtures, and one-stage separation is attainable for some alcohol–water mixtures such as an n-propanol–water and an isopropanol–water system, which has a good separation factor of 220 for the n-PrOH/water system and 240 for the i-PrOH/water system using 85 wt % alcohol concentration at 60°C. The flux for both cases is around 0.5 kg m⁻² h⁻¹. At the same time, the structure of the chemically modified chitosan membranes and their separation characteristics for aqueous alcohol solutions are also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2035–2041, 1998     

Preparation of water‐swollen hydrogel membranes for gas separation

Water‐swollen hydrogel (WSH) membranes for gas separation were prepared by the dip‐coating of asymmetric porous polyetherimide (PEI) membrane supports with poly(vinyl alcohol) (PVA)–glutaraldehyde (GA), followed by the crosslinking of the active layer by a solution method. Crosslinked PVA/GA film of different blend compositions (PVA/GA = 1/0.04, 0.06, 0.08, 0.10, 0.12 mol %) were characterized by differential scanning calorimetry (DSC) and their water‐swelling ratio. The swelling behavior of PVA/GA films of different blend compositions was dependent on the crosslinking density and chemical functional groups created by the reaction between PVA and GA, such as the acetal group, ether linkage, and unreacted pendent aldehydes in PVA. The permeation performances of the membranes swollen by the water vapor contained in a feed gas were investigated. The behavior of gas permeation through a WSH membrane was parallel to the swelling behavior of the PVA/GA film in water. The permeation rate of carbon dioxide through the WSH membranes was 10⁵ (cm³ cm^?2 s^?1 cmHg) and a CO₂/N₂ separation factor was about 80 at room temperature. The effect of the additive (potassium bicarbonate, KHCO₃) and catalyst (sodium arsenite, NaASO₂) on the permeation of gases through these WSH membranes was also studied. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1785–1791, 2001     

Pervaporation separation of binary organic–aqueous liquid mixtures using crosslinked PVA membranes. III. Ethanol–water mixtures

The application of the pervaporation process in biotechnology is rapidly growing. A two stage pervaporation process could be applied to the downstream processing of ethanol fermentation. In this paper, the second stage process—a water-selective process—was investigated in detail using the crosslinked poly(vinyl alcohol) membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent. The ratio of poly(vinyl alcohol) and poly(acrylic acid) in the membrane was 90/10, 85/15, and 80/20 by weight. The prepared membranes were tested to separate the various compositions of the water–ethanol mixtures, specially 50/50 solution at 60°C and 30/70, 20/80, 10/90, and 4.4/95.6 solutions at 60, 70, and 75°C. For water: ethanol = 50 : 50 solution, the separation factor α_w/e = 260 at 75°C was obtained by using a PVA/PAA = 80/20 membrane. The permeation rate and the separation factor at the azeotropic point of a water–ethanol mixture showed 30 g/m²/h and 5800 at 75°C, respectively, when a PVA/PAA = 80/20 membranes was used. © 1995 John Wiley & Sons, Inc.     

Preparation of PVA membranes containing β-cyclodextrin oligomer (PVA/CD membrane) and their pervaporation characteristics for ethanol/water mixtures

Poly(vinyl alcohol) (PVA) membranes were modified by introducing β-cyclodextrin (β-CD) oligomer, which has an inclusion ability sensitive to size, structure, and hydrophilicity of the guest molecule. The modified membranes (PVA/CD membrane) were prepared by casting of the aqueous solutions of PVA and β-CD oligomer. The CD oligomer was immobilized in the membranes by cross-linking with glutaraldehyde. The cross-linking times were 1 and 8 h. The content of CD in the membranes was 33 wt %. The effects of CD on the pervaporation characteristics for water/ethanol were investigated by comparisons with those of the cross-linked PVA membranes. For the 1 h cross-linked membranes, CD increased both the water permeation rate and selectivity at lower ethanol concentrations in the feed. At higher ethanol concentrations, CD increased the water selectivity, but it decreased the water permeation rate. For the 8 h cross-linked membranes, at lower ethanol concentrations, CD increased the water permeation rate, but the water selectivity through the PVA/CD membrane was almost equal to that of the PVA membrane. At higher ethanol concentrations, CD increased the water selectivity and decreased the water permeation rate. These effects of CD can be interpreted in terms of the inclusion strength in the cavity and the reduction of the cross-linking density of the PVA phase in the membranes. © 1994 John Wiley & Sons, Inc.     

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.     

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.     

Preparation and characterization of bipolar membranes modified using photocatalyst nano‐TiO2 and nano‐ZnO

The nano‐ZnO and nano‐TiO₂ were added into chitosan (CS) anion layer to prepare polyvinyl alcohol (PVA) ‐ sodium alginate (SA)/ TiO₂‐ZnO‐CS (here, PVA:polyvinyl alcohol; SA:sodium alginate) bipolar membrane (BPM), which was characterized using scanning electron microscopy, atomic force microscopy (AFM), thermogravimetric analysis (TG), electric universal testing machine, contact angle measurer, and so on. Experimental results showed that nano‐TiO₂‐ZnO exhibited better photocatalytic property for water splitting at the interlayer of BPM than nano‐TiO₂ or nano‐ZnO. The membrane impedance and voltage drop (IR drop) of the BPM were obviously decreased under the irradiation of high‐pressure mercury lamps. At a current density of 60 mA/cm², the cell voltage of PVA‐SA/TiO₂‐ZnO‐CS BPM‐equipped cell decreased by 1.0 V. And the cell voltages of PVA‐SA/TiO₂‐CS BPM‐equipped cell and PVA‐SA/ZnO‐CS BPM‐equipped cell were only reduced by 0.7 and 0.6 V, respectively. Furthermore, the hydrophilicity, thermal stability, and mechanical properties of the modified BPM were increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhanced glycerol dehydration of pervaporation cross-linked PVA membranes modified by VUV/UV-C treatments

The high glycerol miscibility in water needs more efficient processes to decrease the cost of dehydration. Water stable poly(vinyl alcohol) based membranes cross-linked with 15% w/w of maleic acid were used for dehydrating glycerol-water mixtures using pervaporation (PV). The membranes were characterized using water contact angle, profilometry, Fourier transformed infrared spectroscopy-attenuated total reflectance, x-ray photoelectron spectroscopy, water stability, swelling tests, and PV. Membranes were treated using dry methods with vacuum ultraviolet (VUV; 162 nm) or ultraviolet (UV)-C (254 nm) radiation and exposed to O₂ or acrylic acid vapors, respectively. The VUV and UV-C treatments improve PV performances, increasing the water separation selectivity more than 4 and 8.5 times, respectively. UV-C treatments exhibit a water flux (kg m⁻² h⁻¹), selectivity and PSI (kg m⁻² h⁻¹) of 0.3, 250, and 87.4 respectively. Highly hydrophilic functional groups grafted onto the surface of the membranes after irradiation favor the selective transfer of water through the membrane. Overall, the VUV or UV-C membrane treatments show great PV prospect in glycerol dehydration.     

Preparation and characterization of nanoparticle-filled,mixed-matrix membranes for the pervaporation dehydration of isopropyl alcohol

Novel polymeric mixed-matrix membranes (MMMs) were prepared by the incorporation of different amounts of 13X zeolite into a sodium carboxymethylcellulose (NaCMC)/poly(vinyl alcohol) (PVA) blend matrix. The resulting MMMs were characterized by attenuated total reflectance–Fourier transform infrared spectroscopy to analyze the possible chemical reactions between NaCMC, PVA, zeolites, and glutaraldehyde. Scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction were used to analyze the surface morphology, thermal stability, and crystallinity, respectively, of the membranes. Swellings studies were performed at 35°C, and we found that membranes containing 20 wt % zeolite showed higher values (960 kg m⁻² h⁻¹) at 17.5 wt % water in an isopropyl alcohol (IPA)/water mixture. Pervaporation (PV) experiments were also performed to evaluate the membrane performance in different compositions of the IPA/water mixture at 35°C. The mechanical properties were also tested, and we found that the optimum mechanical strength and percentage elongation at break were 42.24 N/mm² and 3.38, respectively, for the membrane containing 15 wt % zeolite. The experimental results show that both the flux and selectivity increased with increasing zeolite content. The membrane containing 20 wt % zeolite showed the highest separation selectivity (5118) with a substantial flux of 0.121 kg m⁻² h⁻¹ at 35°C and with 10 wt % water in the feed; this suggested that the membranes could be used effectively to break the azeotropic point of the water–IPA mixture, so as to remove a small amount of water from IPA. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of graft copolymeric membranes of poly(vinyl alcohol) and polyacrylamide for the pervaporation separation of water/acetic acid mixtures

Graft copolymers of poly(vinyl alcohol) (PVA) with polyacrylamide were prepared and membranes were fabricated at 48 and 93% grafting of acrylamide onto PVA. These membranes were used in the pervaporation separation of water/acetic acid mixtures at 25, 35, and 45°C. The permeation flux, separation selectivity, diffusion coefficient, and permeate concentration were determined. The highest separation selectivity of 23 for neat PVA at 25°C and the lowest value of 2.2 for 93% acrylamide‐grafted PVA membranes were observed. A permeation flux of 1.94 kg m^?2 h^?1 was found for the 93% grafted membrane at 90 mass % of water in the feed mixture. The diffusion coefficients in a water/acetic acid mixture had an effect on the membrane permselectivity. The Arrhenius equation was used to calculate the activation parameters for permeation as well as for the diffusion of water and of acetic acid. The activation energy values for the permeation flux varied from 97 to 28 kJ/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 244–258, 2002