PVA Composite Membranes Research Articles

Preparation and Characterization of PVA Composite Membranes with TiO2 and TiO2/ZrO2 Nanoparticles: A Comparative Study

Preparation and Characterization of PVA Composite Membranes with TiO2 and TiO2/ZrO2 Nanoparticles: A Comparative Study

The influence of polyvinyl alcohol concentration toward conductivity and permeability of chitosan - montmorillonite composite membrane

The composite membrane is synthesized using chitosan as a matrix membrane with montmorillonite (MMT) as a filler and modified using polyvinyl alcohol (PVA). The main aim of this study is to find out the influence of PVA concentration and the working temperature toward the permeability of chitosan?MMT/PVA composite membrane. Fourier transform infrared spectroscopy (FTIR) characterization is performed in order to identify the interaction between the chitosan matrix and the modified MMT with PVA. The presence of new absorption at 1116.82 and 619.17 cm-1 indicated the interaction between MMT and PVA. Further, the widening of OH absorption indicated the hydrogen bond which is formed between chitosan matrix and PVA. This interaction is also demonstrated by the evenly distributed surface on scanning electron microscope (SEM) topography analysis. The thermal stability of composite membrane is determined by thermal gravimetry analysis (TGA). In addition, the composite membrane containing PVA has four patterns decomposed. When the TVA is absent from the composite membrane, it has three decomposition patterns, which are shown by TGA analysis. Based on its tensile strength, the composite membrane has good mechanical properties. The proton conductivity of the composite membranes are directly proportional to the PVA concentration. On the other hand, the methanol permeability of composite membranes is inversely proportional with the PVA concentration. The highest proton conductivity was obtained with the addition of 2 % PVA of 2.94?10-4 S cm-1. Further, it also has the lowest methanol permeability with the value of 5.05?10-6 cm2 s-1. As a result, the crosslinked composite membrane chitosan? ?MMT prepared by PVA-crosslinking technique has the potential to be exploited for the direct methanol fuel cell application.

Cellulose Nanofiber-Assisted Dispersion of Halloysite Nanotubes via Silane Coupling Agent-Reinforced Starch-PVA Biodegradable Composite Membrane.

HNTs (halloysite nanotubes) are widely used in reinforcing material, often used in material reinforcement and particle loading. However, their easy agglomeration causes them to have great limitations in application. In this work, two kinds of silane coupling agents (KH560 and KH570) were introduced to graft the CNF/HNT (cellulose nanofiber) nanoparticles used to reinforce the starch-polyvinyl alcohol (PVA) composite membranes. The mechanical properties, water resistance properties and thermal performance of the composite membrane were tested. The results showed that the CNF/HNTs nanoparticle system modified by two silane coupling agents enhanced the tensile strength (TS) of the starch–PVA composite membranes by increments of 60.11% and 68.35%, and, in addition, the water resistance of starch–PVA composite membrane improved. The introduction of chemical bonds formed associations and a compact network structure, which increased the thermal stability and the crystallinity of the starch–PVA composite membrane. In the study, we creatively used CNF to disperse HNTs. CNF and HNTs were combined under the action of the silane coupling agent, and then mixed into the starch–PVA membranes matrix to prepare high-performance degradable biological composite membranes.

A New Type of Composite Membrane PVA-NaY/PA-6 for Separation of Industrially Valuable Mixture Ethanol/Ethyl Tert-Butyl Ether by Pervaporation.

Pervaporation is a membrane technique used to separate azeotropic and close boiling solvents. Heterogenous PVA composite membranes with NaY zeolite supported on polyamide-6 were fabricated and utilized in organic–organic pervaporation. The efficiency of prepared membranes was evaluated in the separation of ethanol/ethyl tert-butyl ether (EtOH/ETBE) using separation factor (β) and the thickness normalized pervaporation separation index (PSIN). Implementation of the fringe projection phase-shifting method allowed to the determined contact angle corrected by roughness. The influence of the presence of water traces in the feed on the overall separation efficiency was also discussed using the enrichment factor for water (EFwater). The incorporation of NaY into PVA matrix increases surface roughness and hydrophilicity of the composite membrane. It was found that membranes selectively transport ethanol from the binary EtOH/ETBE mixture. The values of β (2.3) and PSIN (288 μm g m−2 h−1) for PVA-NaY/PA6 membrane were improved by 143% and 160% in comparison to the values for the pristine PVA/PA6 membrane. It was found that membranes showed EFwater > 1, thus revealing the preferential transport of water molecules across membranes. These results are also significant for the design of membranes for the removal of water excess from the mixtures of organic solvents.

Imidazolium functionalized poly(vinyl alcohol) membranes for direct methanol alkaline fuel cell applications

AbstractIn this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. 1H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm−1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 107 Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry

PVA/nanocellulose nanocomposite membranes for CO2 separation from flue gas

In this paper, we explore the use of nanocelluloses as an additive to poly (vinyl alcohol) (PVA) nanocomposite membranes for CO2/N2 mixed-gas separation. Our findings are that several types of nanocellulose can be used to improve membrane performance. PVA/cellulose nanocrystals (CNC) nanocomposite membranes have the most promising performance, with increased CO2 permeance (127.8 ± 5.5 GPU) and increased CO2/N2 separation factor (39 ± 0.4) compared to PVA composite membranes, with permeance 105.5 ± 1.9 GPU and separation factor 36 ± 0.5. The performance of PVA/CNC membranes is similar compared to PVA/carbon nanotubes (CNTs) membranes shown earlier. Thus, CNTs can be replaced by CNC that is biodegradable and non-toxic. Investigating several different nanocellulose types reveal that a high nanocellulose charge and small nanocellulose particles are important nanocellulose traits that improve membrane performance.

Facile modification of thin-film composite nanofiltration membrane with silver nanoparticles for anti-biofouling

This study focuses on the modification of a commercial nanofiltration (NF) membrane by an in-situ reaction to load silver nanoparticles (AgNPs) for anti-biofouling. Poly (vinyl alcohol) (PVA) was coated onto the NF membrane firstly, and silver salt was then deposited on the surface of PVA layer. Through thermal reduction, AgNPs with 10–20 nm in diameter were formed and immobilized onto the membrane surface by the interaction between AgNPs and PVA, as confirmed by UV–vis absorption spectrum, SEM and XPS analysis. Compared to the pristine NF90 membrane, the PVA composite membranes (NF90-PVA) and AgNPs (NF90-PVA-AgNPs) modified membranes exhibit lower water flux and slightly higher salt rejection. Release of silver ion experiments were assessed via batch method, and the results indicate silver ion can be released from the AgNPs modified membrane continuously and steadily, which may be responsible for the improved and long-time antibacterial ability of the membrane. Due to the simplicity of the method, the ability to immobilize the AgNPs to avoid leaching out, and the strong antibacterial activity, this NF90-PVA-AgNPs composite membrane displays potential applications in industrial water-treatment.

Desalination of dye solution utilizing PVA/PVDF hollow fiber composite membrane modified with TiO2 nanoparticles

Novel poly(vinyl alcohol) (PVA)/poly(vinylidene fluoride) (PVDF) hollow fiber composite membranes modified with nano-TiO2 were prepared by a dip-coating method and they are suitable to be utilized in dye desalination and wastewater treatment. Glutaraldehyde (GA) was used as a cross-linker for the composite polymer membrane in order to enhance the chemical, thermal as well as mechanical stabilities. The surface morphologies and chemical structures of modified membranes were observed by scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS) and FTIR spectroscopy. Zeta potential of the membrane surface was used to analyze the membrane separation performance. Separation efficiency of dye and salts through novel PVA/PVDF composite membrane was dramatically influenced by dye concentration, salts concentration, pH and temperature of feed solution. Fouling and thermal stability of the membrane were also evaluated with CR, NaCl, and Na2SO4 as model compounds. The separation datas showed that the 1g/L nano-TiO2 modified membrane presented highest performance in terms of the rejections to CR, MO, and MB being 94±2.57%, 52.1±2.45%, and 92±2.20%, respectively. And all the PVA composite membranes had no rejection to salts (NaCl, Na2SO4). Compared with PVA composite membrane, the PVA composite membrane modified with nano-TiO2 has higher separation efficiency, antifouling and thermal stability.

Polymer/Ceramic Composite Membranes and Their Application in Pervaporation Process

Pervaporation (PV), as an environmental friendly and energy-saving separation technology, has been received increasing attention in recent years. This article reviews the preparation and application of macroporous ceramic-supported polymer composite pervaporation membranes. The separation materials of polymer/ceramic composite membranes presented here include hydrophobic polydimethylsiloxane (PDMS) and hydrophilic poly(vinyl alcohol) (PVA), chitosan (CS) and polyelectrolytes. The effects of ceramic support treatment, polymer solution properties, interfacial adhesion and incorporating or blending modification on the membrane structure and PV performance are discussed. Two in-situ characterization methods developed for polymer/ceramic composite membranes are also covered in the discussion. The applications of these composite membranes in pervaporation process are summarized as well, which contain the bio-fuels recovery, gasoline desulfuration and PV coupled process using PDMS/ceramic composite membrane, and dehydration of alcohols and esters using ceramic-supported PVA or PVA-CS composite membrane. Finally, a brief conclusion remark on polymer/ceramic composite membranes is given and possible future research is outlined.

Separation of Dimethylformamide/H<sub>2</sub>O Mixtures Using Pervaporation-Distillation Hybrid Process

Three kinds of commercial PVA composite membranes with different crosslinking degrees (PVA-1, PVA-2 and PVA-3) were used to separate DMF/H2O mixtures. Their pervaporation performance was investigated at different operation temperatures. The results showed that PVA-1 was the most suitable one for separating DMF/H2O mixtures. When operation temperature was 60°C and downstream pressure was lower than 6kPa, flux reached to 0.59 kg·m-2·h-1 and separation factor was 33 for PVA-1 membranes. Aspen Plus® was applied to simulate the normal distillation for retentate from pervaporation unit. Comparing with the two-effect distillation, the cost of concentrating DMF could be reduced 16.2% to 19.2% for DMF aqueous solution with different composition by hybrid processes. The cost would be the lowest for a hybrid process that concentrated the feed into 50wt% by pervaporation firstly, then concentrated retentate to 99.6wt% by two-effect distillation

Treatment of stable oil/water emulsion by novel felt-metal supported PVA composite hydrophilic membrane using cross flow ultrafiltration

The novel felt-metal supported PVA composite hydrophilic ultrafiltration membrane was used for the treatment of oil/water(O/W) emulsion. The effects of transmembrane pressure(TMP), cross flow velocity, feed concentration on membrane performance were investigated, and ultrasonic cleaning of the fouled membrane was also investigated. The results show the flux increases with the increase of cross-flow velocity and TMP within the given TMP range from 0.20 MPa to 0.40 MPa. With increase of initial oil concentration increases, the oil rejection increases while the permeate flux decreases. The composite membrane shows more than 90% oil rejection within the initial oil concentration range from 0.05% to 0.50% (mass fraction) at TMP of 0.30 MPa. The fouling of the composite membrane increases rapidly during the initial 20 min at given TMP range from 0.20 MPa to 0.40 MPa, and it increases slowly after 30 min. The results also show that ultrasound is very effective in removing oil fouling of the fouled membrane, and the properties of the composite ultrafiltration membrane can be completely recovered by 10 min of sonication.

UF membrane of PVA modified with TDI

Poly (vinyl alcohol) (PVA) is an excellent membrane material for preparation of hydrophilic ultrafiltration (UF) and nanofiltration membranes. But its chemical constitution and water solubility infer the disadvantage of easier degradation and elimination after use. This study focuses on the modification of interfacial polymerization PVA composite UF membrane with toluene diisocyanate (TDI). The effects of the reaction time and PVA, TDI, sodium dodecyl sulfate and sodium hydroxide with different concentrations were investigated on the performances of composite membranes. Anti-fouling to protein and oil was obtained when it was compared with no modified membrane. Also, the recovery ratio of pure water flux of PVA modified UF membrane is higher than that of support membrane.

Dehydration of caprolactam–water mixtures through cross-linked PVA composite pervaporation membranes

ɛ-Caprolactam (CPL) is the monomer of nylon-6 used extensively in the manufacture of high quality nylon-6 fibers and resins. Since CPL is a very heat-sensitive substance and water is the most important impurity in the final CPL purification, reduced pressure distillation through triple-effect evaporation sets is widely adopted by chemical industry. But high energy consumption, high wastage and condensate pollution have restricted the wide-scale production of CPL and the commercial profit of the manufactures. To improve or develop a new CPL dehydration process, pervaporation separation of CPL–water mixtures was investigated using composite membranes consisting of a selective poly(vinyl alcohol) (PVA) membrane as top layer and a porous polyacrylonitrile (PAN) substrate. The selective layer was formed by PVA matrix followed by the cross-linking reaction of PVA with glutaraldehyde. The membranes were characterized by SEM, FTIR and TGA. Due to the formation of more compact cross-linked structure, cross-linked PVA composite membranes exhibited enhanced thermal stability. Through evaluating the pervaporation performance, we introduced a pervaporation transport equation to normalized permeation fluxes in terms of water permeance, CPL permeance and selectivity. The evaluated results have revealed that the separation performances of PVA composite membranes are strongly related to its hydrophilic/hydrophobic nature as well as the operating parameters, such as feed concentration and operating temperature. Experimental data showed that the PVA composite membranes had superior pervaporation separation performances for dehydration of caprolactam–water mixtures, which provided a new way for CPL dehydration.

Poly(vinyl alcohol)–zeolite T mixed matrix composite membranes for pervaporation separation of water + 1,4-dioxane mixtures

Poly(vinyl alcohol) and zeolite T mixed matrix composite membranes prepared by solution casting method followed by crosslinking with glutaraldehyde were tested for pervaporation (PV) separation of water + 1,4-dioxane mixtures. PV separation characteristics of the crosslinked composite membranes were studied at varying feed water compositions and temperatures. It was found that the composite membrane containing 15 wt.% of zeolite T (PVA-3) gave the higher separation factor of 1689 for 10 wt.% water containing feed mixture as compared to higher water composition of the feed mixtures. Comparatively, a low selectivity of 59 was observed for plain crosslinked PVA membrane at 10 wt.% water in the feed mixture; this value further decreased with increasing water concentration of the feed mixture. Flux for plain PVA membrane increased from 0.128 to 0.247 kg/m 2 h over the studied water composition range of 10–30 wt.% in the feed, while for the same feed water compositions, flux values for PVA-3 membrane were higher, which increased from 0.213 to 0.309 kg/m 2 h. Observed flux was higher for composite membranes, but lower for plain crosslinked PVA membrane; at the same time, selectivity was also higher for PVA composite membranes. Similar trends were observed at 40 and 50 °C when PV experiments were performed for 10 wt.% water containing feed mixture. With increasing temperature, flux increased considerably, but selectivity decreased. The PV performance was also studied by calculating permeation flux ( J), selectivity ( α), pervaporation separation index (PSI) and enrichment factor ( β). Permeation flux followed the Arrhenius trends over the investigated range of temperature.

Preparation and characterization of N-methylene phosphonic and quaternized chitosan composite membranes for electrolyte separations

Chitosan was functionalized either by introducing a phosphonic acid group or by quaternization of existing primary ammonium groups in order to make it a water-soluble material. Functionalized chitosans and poly(vinyl alcohol) (PVA)-based nanoporous charged membranes were prepared in aqueous media and gelated in methanol at 10 °C to tailor their pore structure. These membranes were extensively characterized for their physicochemical, electrochemical, and permeation characteristics using FTIR, TGA, DSC, water content, ion-exchange capacity, ionic transport properties, and membrane permeability studies. N-Methylene phosphonic chitosan (NMPC)/PVA-based membranes exhibited mild cation selectivity and quaternized chitosan (QC)/PVA composite membranes had mild anion selectivity, while a blend of NMPC-QC/PVA membranes exhibited weak cation selectivity because of formation of zwitterionic structure. Viscosity measurements and interaction studies for individual and mixed solutions of NMPC and QC were carried out for the prediction of charge interactions between PO 3H 2 and N +(CH 3) 3 groups and effect on molecular weight due to functionalization. Elaborate electrochemical and permeation experiments were conducted in order to predict suitability of these membranes for the separation of mono- and bivalent electrolytes based on their hydrated ionic radius, and it was found that among all the synthesized membranes, PC/QC-30 had the highest relative permeability, which may extend its suitability for electrolyte separations. Observations were correlated with equivalent pore radius of the different membranes as estimated by membrane permeability measurements.

Ionic cluster mimic membranes using ionized cyclodextrin

Ionic cluster mimic, polymer electrolyte membranes were prepared using polymer composites of crosslinked poly(vinyl alcohol) (PVA) with sulfated-β-cyclodextrins (β-CDSO3H) or phosphated-β-cyclodextrins (β-CDPO(OH)2). When Nafion, developed for a fuel cell using low temperature, polymer electrolyte membranes, is used in a direct methanol fuel cell, it has a methanol crossover problem. The ionic inverted micellar structure formed by micro-segregation in Nafion, known as ionic cluster, is distorted in methanol aqueous solution, resulting in the significant transport of methanol through the membrane. While the ionic structure formed by the ionic sites in either β-CDSO3H or β-CDPO(OH)2 in this composite membrane is maintained in methanol solution, it is expected to reduce methanol transport. Proton conductivity was found to increase in PVA membranes upon addition of ionized cyclodextrins. Methanol permeability through the PVA composite membrane containing cyclodextrins was lower than that of Nafion. It is thus concluded that the structure and fixation of ionic clusters are significant barriers to methanol crossover in direct methanol fuel cells.

Pervaporation of fluoroethanol/water and methacrylic acid/water mixtures through PVA composite membranes

2,2,2-Trifluoroethyl methacrylate (TFEMA) is used in the preparation of functional water-repellent paints and optical fiber coating agents, and is manufactured by esterification of 2,2,2-trifluoroethanol (TFEA) and methacrylic acid (MA) via a dehydration process using azeotropic distillation. To substitute for the hazardous dehydration process, composite-type PVA pervaporation membranes were prepared using glutaraldehyde on a porous polyethersulfone support and their basic pervaporation properties were determined for TFEA/water and MA/water mixtures. The effect of the degree of crosslinking agent, feed concentration, and operating temperature on the pervaporation properties was determined. The PVA composite membranes showed excellent dehydration performances that are suitable for application to the esterification of TFEMA.

Simulation of pervaporation process for ethanol dehydration by using pilot test results

This paper focuses on providing a pervaporation simulation method for ethanol dehydration from a practical point of view. The simulation procedure is performed by setting up simulation equations which describe the pervaporation process, obtaining the necessary data from pervaporation batch mode pilot tests, verifying the simulation tool through simulations of continuous mode pilot tests, and comparing the simulation results with the real pilot test results. We considered the mass and energy balances that describe separating an ethanol/water mixture by a pervaporation membrane. The simulation equations were mathematically expressed into simultaneous non-linear differential equations based on these balances. The necessary data for simulation consist of the thermophysical properties for the ethanol-water mixture and the characteristic data of a PVA composite membrane. The membrane characteristic data are permeation flux and membrane selectivity, which are functions of feed composition and operating conditions. These data were experimentally determined by a batch mode pilot test. The continuous mode pilot tests were simulated and the simulation results were compared to the real test results. The resulte were fairly good.

Integration of pervaporation for the removal of water in the production process of methylisobutylketone

Results of pervaporation experiments are reported for the dehydration of two different mixtures: a ternary synthetic mixture containing acetone, methylisobutylketone (MIBK) and water and a so-called product mixture consisting of 50–60 wt% acetone 40-30 wt% MIBK 7–8 wt% water and 3-2 wt% by-products as directly obtained from a MIBK production plant. The pervaporation experiments have been carried out with PVA composite membranes of different degrees of crosslinking and two different types of TexSep composite membranes. The influence of feed composition, permeate pressure and temperature on the separation characteristics has been investigated. Especially the highly crosslinked PVA-1001 membrane yields high water concentrations in the permeate and fluxes good enough for practical application. The pervaporation results for the PVA-1001 membrane obtained with a laboratory test cell are compared with results obtained in a pilot unit. Two possibilities for integrating a pervaporation unit in a process of the synthesis of MIBK are discussed in detail.

Study of a new pervaporation membrane Part I. Preparation and characteristics of the new membrane

A new alcohol dehydration membrane, poly(vinyl alcohol)—chitosan blended composite membrane (PVA-CS) has been prepared. This membrane has high selectivity and promising permeability, especially in separating ethanol—water near the azeotropic region ( J t > 200 g/m 2 h, α w e > 500, 70°C). The separating characteristics, which vary with feed composition, operating temperature and the surface structure of the membrane, are determined and the results agree well with the theoretical predictions. The characteristics of mechanical strength, stability and resistance to water were also determined. The results show that they are considerably enhanced by blending and crosslinking, in comparison with PVA composite membranes.