Pervaporation Of Ethanol-water Mixture Research Articles

Preparation of N-methylol nylon-6 membranes for pervaporation of ethanol-water mixtures

N-methylol nylon 6 membranes were prepared by reacting nylon-6 with formaldehyde. Elemental analysis, used to analyze the composition of modified membranes, showed that the degree of substitution increased with formaldehyde content in the reaction solution. The modified nylon-6 membranes exhibited a high affinity to ethanol. Pervaporation results for the separation of ethanol-water mixtures showed that these membranes were water-selective, indicating that the diffusion property is the dominant factor. An N-methylol nylon-6 membrane with 33% degree of substitution showed the best membrane performance. In order to control the swelling of N-methylol nylon-6 membranes in the feed solutions of high ethanol content, thermal crosslinking was applied at 180°C for different times. It was found that heat treatment of 10 minutes gave the optimal permselectivity. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 855–863, 1997

Pervaporation of ethanol-water mixtures through polydimethylsiloxane-polystyrene interpenetrating polymer network supported membranes

The pervaporation performances of polydimethylsiloxane-polystyrene interpenetrating polymer network (PDMS-PS IPN) layers supported on polyethersulfone (PESF) ultrafiltration membranes for ethanol-water mixtures were investigated. The PDMS-PS IPN layers were prepared via the sequential IPN technique. The mechanical properties and the film-forming capability of the PDMS-PS IPN are superior to those of the crosslinked PDMS. An inversion of the selectivity of PDMS-PS IPN layers supported on PESF membranes was observed; at low ethanol concentrations in the feed, the membrane was more selective for ethanol, while at high concentrations it was more selective for water. An explanation is suggested for this inversion. For a mixture containing 10 wt% ethanol, which is of interest in biotechnology, the membrane was ethanol selective, and the permeation rate and separation factor of the PDMS-PS IPN supported membrane at 60°C, with a crosslinked PS content of 40 wt%, were 160 g/m 2 h and 5.5, respectively.

Pervaporation of ethanol-water mixtures through temperature-sensitive poly(vinyl alcohol- g- N-isopropyacrylamide) membranes

Novel temperature-sensitive membranes have been synthesized by grafting poly( N-isopropyacrylamide) (poly(NIPAAm)) onto a poly(vinyl alcohol) (PVA) backbone using hydrogen peroxide-ferrous ion as initiator. Due to the grafting of poly(NIPAAm), the hydrophilic/hydrophobic balance and the polarity of the pendent groups within the membranes are modified. Significant temperature sensitivity of the grafted membranes is observed close to the LCST of linear poly(NIPAAm) in the pervaporation processes for ethanol-water separation. Both the pervaporation and sorption selectivities for water show a maximum value in the vicinity of 30–32°C for an ethanol content of 75 and 80%. The temperature sensitivity of the grafted membranes also depends on the ethanol concentration. The maxima of pervaporation and sorption selectivities disappear when the ethanol content is lower than 75% because the much larger degree of swelling reduces the size screening effect of the membranes.

Pervaporation of ethanol-water mixtures through poly(vinyl alcohol-g-acrylic acid) membranes prepared by use of Fenton's reagent in grafting

Ionic crosslinking of the ferric ions and the carboxylic groups in the poly(vinyl alcohol-g-acrylic acid) (poly(VA-g-AA)) membranes improves the size screening effect in the pervaporation of ethanol-water separation. In the grafting polymerization of acrylic acid monomer onto poly(vinyl alcohol) (PVA), ferric ions are remained in the polymer membranes as the Fenton's reagent(Fe2+-H2O2) is used to initiate the reaction. Completely reversed trends in terms of the degree of swelling, the pervaporation selectivity, and the flux of permeates are obtained depending on that the ferric ions are present or absent in the membranes. The degree of swelling decreases, the pervaporation selectivity increases, and the flux decreases as the grafting percentage increases for the membranes containing ferric ions. The degree of swelling and the flux of permeates increase but the pervaporation selectivity is reduced as the grafting percentage increases for the membranes which were washed with acid to remove ferric ions.

Pervaporation of Ethanol and Water Through Polymeric Membranes with Incorporated N-(Halogenophenyl)maleimide Units

Styrene N-(chloro- or bromophenyl)maleimide and methyl methacrylate N-(chloro- or bromophenyl)maleimide copolymers were synthesized. Membranes casted from the copolymer solutions were used for the pervaporation of ethanol water mixtures at 35 °C. The membranes were characterized by the separation factor related to the preferentially transported water and by the permeate flux. The pervaporation characteristics were dependent on the hydrophilicity or polarity of the polymer chains, on the kind and position of the halogen and on the composition of the mixture to be separated. Membranes made from the copolymers of styrene with N-(2-chlorophenyl)maleimide or N-(2-bromophenyl)maleimide show the highest separation factors in the separation of concentrated ethanol solutions. The permeate flux through membranes made from the copolymers of methyl methacrylate with N-(halogenophenyl)maleimide was by one order of magnitude higher than through membranes made from similar styrene copolymers.

Cationic/anionic interpenetrating polymer network membranes for the pervaporation of ethanol-water mixture

The pervaporation of ethanol-water mixtures was examined on cationic/anionic interpenetrating polymer network (IPN) membranes. The cationic polyurethane prepared by quaternizing the tertiary amine from N-methyldiethanolamine and the anionic acrylic copolymer from acrylic acid were used as the cationic and anionic component. The permselectivity of the membrane was investigated with variations in the IPN composition and the ion concentration in the membrane. The separation factor increased as the content of the anionic component in the membrane increased. The ion content in the membrane was also found to be an important factor for the optimum permseparation of water. Better performance was achieved by using PEG-based polyurethane as the cationic component of the IPN membrane. Moreover, the highest selectivity was observed for the IPN membrane with 10 wt.% of PEG-based polyurethane. This result could be explained by high swelling restriction due to the increase in physical crosslinking between networks.

Pervaporation of ethanol-water mixture by plasma films prepared from hexamethyldisiloxane

The plasma polymerization process was investigated to obtain plasma films like poly(dimethylsiloxane), and the formed films were applied as membranes for pervaporation of ethanol-water solution. A reaction chamber which had the triode electrode structure for initiation of a glow discharge was provided for preparation of films like poly(dimethylsiloxane) by plasma polymerization. Films plasma-polymerized from hexamethyldisiloxane (HMDSO) resembled poly(dimethylsiloxane) in spectroscopic view and were composed of dimethylsiloxane chains with branches of trimethylsilyl groups. The surface energy for the films was 19.6 mN/m. The films deposited from HMDSO on Nuclepore membrane showed good ethanol-selectivity in pervaporation of ethanol-water solution. The separation factor depended on the film thickness as well as the feed composition. The film-thickness effect was maximized at 34 nm thick, and the separation factor reached 4.5. A model for the separation process using our composite membrane was discussed.

Hydrophilic/hydrophobic IPN membranes for the pervaporation of ethanol-water mixture

Pervaporation of ethanol-water mixture was examined on IPN membranes composed of hydrophilic polyurethane(PU) and hydrophobia polystyrene(PS). The IPN membranes showed preferential pervaporation of water over ethanol and revealed high permeation rate. As the content of hydrophobic PS was increased, the permeation rate decreased while the separation factor increased, indicating that the PS domains suppressed the swelling of the PU phase and reduced the plasticizing effect. The average diffusion coefficient, computed from the permeation rate and solubility, was highly dependent on the viscosity and concentration of the permeant in the membrane.

Pervaporation of ethanol-water mixture by plasma films prepared from hexamethyldisiloxane

Pervaporation of ethanol-water mixture by plasma films prepared from hexamethyldisiloxane

Separation of aqueous ethanol mixtures through poly(cyclohexyl methacrylate-co-styrene) membranes.

Separation of ethanol from aqueous ethanol solution was carried out by pervaporation through a membrane which consists of common synthetic polymers. A membrane from poly (cyclohexyl methacrylate-co-styrene) showed membrane performance that preferentially permeated ethanol from ethanol-water mixtures by pervaporation technique. The pervaporation of ethanol-water mixture through the present membrane was analyzed as a solution-diffusion process.