Sorption,diffusion, and swelling characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) in water–acetic acid mixtures

Sorption, diffusion, and swelling characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) were investigated for water–acetic acid mixtures by using a gravimetric method at 30, 40, and 50°C. The membranes were characterized by X‐ray diffraction and Fourier transform infrared techniques. Concentration‐independent diffusion coefficients were obtained by applying Fick's relationship before completion of equilibrium sorption. Permeation coefficients were calculated from sorption and diffusion coefficients. Concentration profiles of liquids were computed considering the sheet geometry for the membrane by solving Fick's equation under suitable boundary conditions. Arrhenius activation parameters were computed for the transport processes. Experimental results and calculated quantities were discussed to understand membrane–solvent interactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1139–1150, 2004     

Sorption,diffusion, and pervaporation separation of water–acetic acid mixtures through the blend membranes of sodium alginate and guar gum‐grafted‐polyacrylamide

Nonporous homogeneous dense membranes were prepared from the blends of sodium alginate (Na–Alg) with guar gum‐grafted polyacrylamide (GG‐g‐PAAm) in the ratios of 3 : 1 and 1 : 1 and these were tested for the pervaporation separation of water–acetic acid mixtures at 30°C. Blend compatibility was studied in solution by measuring the viscosity and the speed of sound. Membranes were crosslinked by glutaraldehyde. The GG‐g‐PAAm polymer and the crosslinked blend membranes were characterized by Fourier transform infrared spectra. High separation selectivity was exhibited by the pure Na–Alg membrane for water–acetic acid (HAc) mixtures containing 20 mass % of water. The permeation flux increased with increasing mass percent of water in the feed as well as with an increase in the amount of GG‐g‐PAAm in the blend, but separation selectivity decreased. Sorption selectivity was higher for the Na–Alg membrane than for the blend membranes, but it decreased with increasing mass percent of GG‐g‐PAAm in the blends. Diffusion selectivity values vary systematically with the blend composition, but not with the amount of water in the feed. Diffusion coefficients of the water–HAc mixtures were calculated from Fick's equation using sorption data and compared with those calculated from flux values obtained in pervaporation experiments. The Arrhenius activation parameters were calculated for the 20 mass % of water in the feed using flux and diffusion data obtained at 30, 40, and 50°C. The diffusion and pervaporation results are explained in terms of solution–diffusion concepts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 259–272, 2002     

Experimental and simulation studies on molecular transport of substituted monocyclic aromatic liquids into fluoropolymer sheet membranes: Liquid structure–diffusion, –sorption,and –permeation relationships

The present study reports an investigation on the molecular transport of 10 monocyclic aromatic liquids (benzene, chlorobenzene, 1,2‐dichlorobenzene, bromobenzene, toluene, p‐xylene, trimethylbenzene, ethylbenzene, methoxybenzene, and ethoxybenzene) at 40 and 50°C through sheet polymeric membranes (FLS‐2650) using a sorption gravimetric technique. Diffusion and permeation coefficients of these liquids were calculated from the sorption data using Fick's diffusion equation. Sorption results were analyzed typically in the case of benzene and chlorobenzene to compute the concentration profiles at different depths along the thickness direction of the sheet membranes and at different time intervals by solving the Fick's equation under appropriate boundary conditions, based on the numerical simulation method developed in “C” language using a finite‐difference method. Transport results were analyzed to establish the relationships between the penetrating liquid structures with diffusion, permeation, and sorption data. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 991–996, 2004     

Syntheses and characterization of blend membranes of sodium alginate and poly(vinyl alcohol) for the pervaporation separation of water + isopropanol mixtures

The blend membranes of sodium alginate and poly(vinyl alcohol) have been prepared by physical mixing in different ratios (75, 50, and 25%) of sodium alginate with poly(vinyl alcohol). The membranes were crosslinked with glutaraldehyde and used in the pervaporation separation of water + isopropanol mixtures at 30°C. The crosslinking reaction was confirmed by Fourier transform infrared spectra. Permeation flux increased with an increase in mass % of water in the feed mixture as well as with an increase in the amount of poly(vinyl alcohol) in the blend, but separation selectivity decreased. Diffusion coefficients of water + isopropanol mixtures have been calculated using the Fick's equation from the sorption data. Arrhenius activation parameters were calculated for 10 mass % of water in the feed mixture using the values of flux and diffusion coefficients obtained at 30, 40, and 50°C. The diffusion and pervaporation results have been explained on the basis of solution‐diffusion principles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3642–3651, 2002     

Molecular transport of n‐alkanes through diol chain‐extended polyurethane membranes

Molecular transport of n‐alkanes was investigated by calculating sorption, diffusion, and permeation of liquids through the diol chain‐extended polyurethane (PU) membranes in the temperature interval 25–60°C. Sorption experiments were performed gravimetrically. Diffusion coefficients were calculated from Fick's equation. These results showed a dependency on the nature and size of interacting n‐alkane molecules as well as morphology of the chain‐extended PUs. Transport kinetics followed an anomalous trend. Using the temperature‐dependent transport parameters, activation energies were calculated for diffusion and permeation processes using an Arrhenius equation. The van't Hoff relationship was used to obtain enthalpy and entropy of sorption. Concentration profiles of liquids through PU membranes were computed using Fick's equation, solved under appropriate initial and boundary conditions. A correlation was attempted between transport properties of liquids and physicomechanical properties of PU membranes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 874–882, 2005     

Synthesis and characterization of polyacrylamide‐grafted sodium alginate copolymeric membranes and their use in pervaporation separation of water and tetrahydrofuran mixtures

Polyacrylamide‐grafted sodium alginate (PAAm‐g‐Na‐Alg) copolymeric membranes have been prepared, characterized, and used in the pervaporation separation of 10–80 mass % water‐containing tetrahydrofuran mixtures. Totally three membranes were prepared: (1) neat Na‐Alg with 10 mass % of polyethylene glycol (PEG) and 5 mass % of polyvinyl alcohol (PVA), (2) 46 % grafted PAAm‐g‐Na‐Alg membrane containing 10 mass % of PEG and 5 mass % of PVA, and (3) 93 % grafted PAAm‐g‐Na‐Alg membrane containing 10 mass % of PEG and 5 mass % of PVA. Using the transport data, important parameters like permeation flux, selectivity, pervaporation separation index, swelling index, and diffusion coefficient have been calculated at 30°C. Diffusion coefficients were also calculated from sorption gravimetric data of water–tetrahydrofuran mixtures using Fick's equation. Arrhenius activation parameters for the transport processes were calculated for 10 mass % of water in the feed mixture using flux and diffusion data obtained at 30, 35, and 40°C. The separation selectivity of the membranes ranged between 216 and 591. The highest permeation flux of 0.677 kg/m² h was observed for 93% grafted membrane at 80 mass % of water in the feed mixture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 272–281, 2002     

Sorption and Diffusion of Organic Liquids into Fluoroelastomer Membranes

Abstract

Sorption and diffusion of organic liquids into fluoropolymer (FC-2179) membranes have been investigated from 30 to 60°C using a gravimetric method. Diffusion coefficients, percent mass uptake, and apparent activation energies for the transport processes have been estimated. Diffusion coefficients of the liquids into the membrane have been computed from Fick's relation. A Flory–Huggins-type interaction parameter was obtained from the solubility parameter concept. Furthermore, the activation parameter values and heat of sorption data have been studied in terms of heat of mixing. The values of diffusion coefficients did not show any considerable dependence on solvent concentration. However, solvent transport as analyzed from an empirical equation was found to be of the anomalous type. Molecular transport also showed a dependence on the chemical nature of the liquids. The concentration profiles of liquids have been calculated at different penetration depths of the membrane at different time intervals by solving Fick's differential equation under suitable initial and boundary conditions. A numerical method based on the finite difference technique was also used to predict the concentration profiles of liquids, and these are compared with the profiles computed from an analytical solution of Fick's equation.     

Effect of carbon black loading on fluoroelastomer–solvent interactions

An analysis of the molecular transport of organic liquids into fluoroelastomer membranes containing varying amounts of carbon black has been undertaken by the sorption–desorption gravimetric method. The variation in carbon black loading and temperature showed a significant effect on their transport characteristics. Diffusion coefficients were calculated from Fick's equation. Experimental sorption–desorption results were analyzed in terms of concentration profiles obtained from a solution of Fick's equation as well as by a numerical method based on the finite difference technique. Arrhenius activation parameters were estimated from the temperature-dependent diffusion and permeation data. The results of this study are discussed in terms of polymer–solvent interactions. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:815–825, 1998     

Sorption,diffusion, and permeation of esters,aldehydes, ketones,and aromatic liquids into tetrafluoroethylene/propylene at 30, 40, and 50°c

The coefficients of sorption, diffusion, and permeation for five organic esters, three aldehydes, one cyclic ketone, and three substituted aromatic liquids have been calculated for tetrafluoroethylene/propylene copolymer membranes at 30, 40, and 50°C with the sorption–gravimetric technique. With the sorption data, the concentration‐independent diffusion coefficients have been calculated from Fick's diffusion equation. Analytical solutions of Fick's equation under suitable boundary conditions have been obtained so that the liquid concentration profiles in the polymeric membranes at different times and different depths of liquid penetration could be computed. Because of the linearly increasing trend of the diffusion coefficients with temperature, efforts have been made to estimate Arrhenius parameters. Experimental values and the computed quantities have been used to determine the membrane–solvent interactions and to propose suitable applications for the membranes under investigation in various situations. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3201–3209, 2003     

Computer simulation and comparative study on the pervaporation separation characteristics of sodium alginate and its blend membranes with poly(vinyl alcohol) to separate aqueous mixtures of 1,4‐dioxane or tetrahydrofuran

A comparative study on the pervaporation separation has been attempted for water + 1,4‐dioxane and water + tetrahydrofuran mixtures using sodium alginate and blend membranes of sodium alginate with 5, 10, and 20 mass % of poly(vinyl alcohol). Pure sodium alginate membrane has a selectivity of 111 to water at 0.35‐mol fraction of water in the feed mixture containing 1,4‐dioxane while for water + tetrahydrofuran mixture, the membrane selectivity to water was 291 at 0.31‐mol fraction of water in the feed mixture. Pervaporation results have been discussed using the solution–diffusion principles. Arrhenius activation parameters for diffusion and permeation have been computed from the temperature‐dependent pervaporation results. Furthermore, experimental results have been analyzed using the complete mixing and plug flow models to compute membrane area as well as design parameters that are useful in scale‐up operations. The plug flow model is more appropriate than the complete mixing model to analyze the pervaporation results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1827–1840, 2004     

A study on molecular transport of organic esters and aromatics into viton fluoropolymers

Molecular transport of organic liquids into Viton fluoropolymers has been investigated by a sorption—desorption gravimetric method. Diffusion coefficients have been calculated from Fick's equation. The sorption—desorption results have been used to calculate the concentration profiles by solving Fick's diffusion equation under suitable boundary conditions. A numerical method based on the finite difference technique was also used to calculate the concentration profiles of liquids as a function of sorption time and thickness of the Viton fluoropolymers. The dependence of sorption, desorption, diffusion, and permeation properties of the liquids on temperature showed a significant effect. The Arrhenius activation parameters have been estimated for diffusion, permeation, and sorption processes. The experimental and calculated results are discussed to study the type and nature of interactions between Viton fluoropolymers and the solvent molecules. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 717–723, 1997     

Sorption,desorption, resorption,redesorption, and diffusion of haloalkanes into polymeric blend of ethylene–propylene random copolymer and isotactic polypropylene

Molecular transport of haloalkanes into sheets of a polymeric blend of an ethylene–propylene random copolymer and isotactic polypropylene has been studied by a sorption gravimetric technique in the temperature interval of 25–70°C. For all liquids, equilibrium sorption, desorption, resorption, redesorption, and degree of penetrant overshoot have been influenced by the nature of the liquid and the temperature. Diffusion coefficients were calculated from the sorption–desorption kinetic curves using Fick's mathematical relations. The values of diffusion coefficients followed the Arrhenius-type behavior. The temperature-dependent sorption data were analyzed using the van't Hoff relation. The activation parameters for diffusion and heat of sorption data were discussed in terms of the molecular interactions between liquids and the polymer chain segments. The experimental and calculated results are discussed on the basis of the chemical nature of liquids. © 1995 John Wiley & Sons, Inc.     

Molecular transport of esters,aldehydes, aromatic liquids,and a ketone into fluoroelastomer membrane at 30, 40, and 50°C

Molecular transport of esters, aldehydes, substituted aromatic liquids, and a ketone through a fluoroelastomer (FC‐2120) membrane sample was studied at 30, 40, and 50°C. Sorption results were obtained by using a gravimetric method and concentration‐independent diffusion coefficients were calculated using Fick's diffusion equation. Permeability coefficients were calculated from sorption and diffusion data. Concentration profiles of the liquid penetrants were calculated by solving the Fick's equation under appropriate initial and boundary conditions and these plots are displayed to show the variations in liquid concentrations with reference to the nature of liquids chosen, membrane thickness, as well as the time of polymer immersion in the liquids. Arrhenius activation parameters were also estimated from a temperature dependence of diffusion and sorption coefficients. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 840–847, 2003     

Sorption/desorption,diffusion, and swelling characteristics of geomembranes in the presence of halo‐organic liquids

Sorption/desorption results of halogen‐containing liquids into high‐density polyethylene, linear low‐density polyethylene, very low‐density polyethylene, and polypropylene geomembranes are presented at 25, 50, and 70°C. Sorption results are obtained by a gravimetric method, and diffusion coefficients have been calculated by using Fick's equation from the initial linear portions of the sorption/desorption curves. Swelling of the geomembranes was studied from a measurement of the increase in volume, thickness, and diameter. From a temperature dependence of sorption and diffusion coefficients, the Arrhenius parameters have been calculated. Liquid concentration profiles have been computed using Fick's equation for the appropriate initial and boundary conditions. The results of this study may have relevance in selecting the suitable geomembrane for a specific application in hazardous waste chemical ponds and other similar situations.     

Migration of substituted aromatic solvents into polyurethane/polystyrene semi‐interpenetrating polymer network

The molecular transport of substituted aromatic solvents through polyurethane/polystyrene (PU/PS, 50/50) semi interpenetrating polymer network has been investigated at 20, 40, and 60°C. Sorption–desorption–resorption–redesorption (S‐D‐RS‐RD) experiments were performed to determine the true value of transport coefficients. Sorption results are obtained by a gravimetric method and diffusion coefficients have been calculated using Fick's equation for the linear data points of time dependent sorption/resorption curves. It was observed that most of the systems follow the Fickian mode of transport. The first order kinetic equation was used to estimate the kinetic rate constant of sorption. Activation parameters for different transport processes were evaluated and the results were used to discuss the polymer–solvent interactions. The concentration profiles at different depths along the thickness of membranes and at different time intervals were computed using Fick's equation under appropriate boundary conditions. The rate of evaporation of liquids has been calculated for desorption and redesorption processes, and these results depend on the volatility of aromatic solvents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 378–390, 2007     

Evaluation of solvent resistivity of fluoropolymers for use as backup membranes in isocyanate samplers

Four types of fluoroelastomer (VITON) membranes were tested for their resistivity toward dimethyl sulfoxide, dioxane, and toluene at 25, 45, and 60°C, using a gravimetric method. Coefficients of diffusion and permeation were calculated from the sorption results. Analytical solutions of Fick's equation as well as a numerical method were used to calculate the concentration profiles of liquids in the membrane materials at different penetration depths and exposure times. Activation parameters for diffusion, permeation, and sorption were obtained from the Arrhenius equation. These membrane materials were evaluated for their ability to serve as a barrier to solvent permeation in a composite membrane sampler for the analytical determination of isocyanates generated during spray-painting operations. © 1996 John Wiley & Sons, Inc.     

Sorption kinetics and diffusion of alkanes into tetrafluoroethylene/propylene copolymer membranes

Sorption kinetics and diffusion of hexane, heptane, octane, nonane, decane, cyclohexane, and 2,2,4-trimethylpentane through tetrafluoroethylene/propylene copolymer membranes were studied using the gravimetric sorption method at 30, 45, and 60°C. Coefficients of diffusion were calculated from Fick's equation. From these data, the permeability coefficients were obtained. Analytical solutions of Fick's relations were used to estimate the liquid concentration profiles into the polymeric membranes at different times. The profiles of liquid concentrations were also simulated for the polymer–solvent systems using the numerical simulation method. Activation parameters for diffusion and sorption were evaluated and these results are discussed in terms of the molecular sizes and geometries of liquids (i.e., shape) as well as temperature. The diffusion coefficients follow a systematic decrease with increasing size of the penetrant molecules. The activation energies i.e., E_D values, increase with increasing size of n-alkanes. © 1996 John Wiley & Sons, Inc.     

Theoretical and experimental investigations of molecular migration and diffusion kinetics of organic esters into tetrafluoroethylene/propylene copolymer membranes

A theoretical analysis of the experimental results on the migration and diffusion kinetics of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate and iso-amylacetate into tetrafluoroethylene/propylene copolymer membranes has been made. Diffusion and permeability coefficients have been calculated from Fick's equation. The concentration profiles of the liquids have been calculated from a solution of Fick's equation as well as using an empirical relation for the esters into the varying penetration depths of the membranes at different time intervals. The diffusion coefficients show a systematic decrease with increasing size of esters and the results are discussed in terms of the membrane-solvent interactions.     

Sorption/desorption and diffusion kinetics of ketones and nitriles into fluoropolymer membranes

Analysis of sorption/desorption and diffusion kinetics of ketones and nitriles at 25, 44, and 60°C into three Du Pont's VITON fluoropolymer membranes loaded with different amounts of carbon black has been undertaken by use of a sorption/desorption technique. The transport results are affected by the percent loading of carbon blacks. Diffusion coefficients have been calculated from Fick's equation. These results show a decrease with increasing amount of carbon black. Experimental results have been analyzed by considering swelling of the membranes. Sorption/desorption results have been analyzed from a calculation of the concentration profiles, which are obtained from the analytical solution of Fick's equation. These results have been compared with a numerical solution based on the finite difference method. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 635–647, 1997     

Activated charcoal‐loaded composite membranes of sodium alginate in pervaporation separation of water‐organic azeotropes

Composite membranes of sodium alginate prepared by incorporating nanosized‐activated charcoal particles were prepared and characterized for the extent of cross‐linking, thermal stability, and mechanical strength properties using Fourier transform infrared, differential scanning calorimetry, and universal testing machine, respectively. The membranes were tested for pervaporation (PV) dehydration of isopropanol (IPA), ethanol (EtOH), 1,4‐dioxane (1,4‐D), and tetrahydrofuran (THF) at their azeotropic compositions. Improved PV performances of the composite membranes were observed compared with plain sodium alginate membrane for all the azeotropes. Sorption was studied to evaluate the extent of interactions between liquids and membranes as well as degree of swelling of the membranes in the chosen aqueous‐organic mixtures. Adding different amounts of activated charcoal into NaAlg offered high water selectivity values of 99.7, 99.1, 99.4, and 99.41%, respectively, for IPA, THF, 1,4‐D, and EtOH. Arrhenius activation parameters were computed from the temperature versus flux plots, which showed systematic trends for different liquids that depended upon their interactions with membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009