The Effect of Skin Layer Composition and Operating Parameters on the Performance of Sulfonated Polysulfone-Poly(Vinyl Alcohol) Composite Reverse Osmosis Membrane

Abstract

A composite membrane for reverse osmosis was prepared from sulfonated polysulfone and poly(vinyl alcohol). The effects of overall polymer solution concentration, composition of casting solution, and heat-curing periods on the reverse osmosis performance of the resulting membrane have been examined. The composite membrane was formed by casting the polymer solution as an ultrathin film on a microporous polysulfone supporter, evaporating the solvent, and heat curing at 120°C for a proper period. The influence of different operating parameters on the performance of the resulting membrane was examined. The results showed that the flux of water increased and salt rejection increased with an increase in the ratio of sulfonated polysulfone to poly(vinyl alcohol) (SPSf/PVA). The flux of water is proportional to the operating pressure of the formed membrane with an SPSf/PVA ratio of 3/3–4/2. The flux of water was found to be a highly nonlinear function of the operating pressure of the formed membrane with an SPSf/PVA ratio of 2/4–0/6.     

Preparation and performance of poly(vinyl butyral) membrane for ultrafiltration

Ultrafiltration membrane was prepared from poly(vinyl butyral). The effects of membrane thickness, polymer concentration, evaporation time, and evaporation temperature, etc., on the performance of the resulting membranes have been studied. Dimethylacetamide was used as a casting solvent. The membrane formed by casting the polymer from a 15 wt % solution and evaporation at 25°C for 30 s had a flux value of 250 cm³ / cm² h (4.8 kg/cm², 26°C) at 92.9% rejection level for dextran sodium sulfate (average mol. wt. 550,000) separation. © 1993 John Wiley & Sons, Inc.     

Properties of modified poly(vinyl alcohol) membranes prepared by the grafting of new polyelectrolyte copolymers for water–ethanol mixture separation

For the preparation of a water‐selective membrane for the pervaporation separation of an azeotropic solution, a series of grafted copolymers were synthesized by the reaction of poly(vinyl alcohol) (PVA) with poly(sodium salt styrene sulfonic acid‐co‐maleic acid) (PSStSA‐co‐MA). The esterification was performed between the hydroxyl groups of PVA and the carboxylic groups of the copolymer with a heat treatment. PSStSA‐co‐MA was prepared with sodium salt styrene sulfonic acid and maleic anhydride copolymerization in dimethyl sulfoxide with azobisisobutyronitrile as an initiator. The reaction mechanism and resultant structure were confirmed with IR spectra. The effect of the heat‐treatment time on the gel content was investigated. The permeation flux decreased and the separation factor increased as the crosslinking agent content rose. A membrane containing 15 wt % PSStSA‐co‐MA was used for water–ethanol azeotropic solution pervaporation at 30°C, and a flux of 0.43 kg/m² h and a separation factor of 190 were obtained. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2854–2859, 2002     

Hydrophilic interpolymer membranes from crosslinked blends of poly(vinylalcohol), poly(styrene sodium sulfonate) and poly(vinyl methyl ether–alt–maleic anhydride)

Interpolymer ion exchange membranes were prepared from a compatible casting solution that contained poly(styrene sodium sulfonate), poly(vinyl methyl ether–alt–maleic anhydride), and poly(vinyl alcohol). Crosslinking of the films was accomplished through the formation of ester linkages that were stable in aqueous environments. Membrane properties (water content, capacity, concentration potential, equivalent conductivity) were measured over a wide range of membrane compositions. Ultrafiltration was carried out with a feed solution that was 0.01N in KCI and 15 ppm in erythrosin. Rejection and hydraulic permeability data were reported as a function of membrane composition.     

Ionically crosslinked poly(acrylic acid) membranes. II. Dry technique

The ionic crosslinking of poly(acrylic acid) for dialysis and reverse osmosis applications has been studied. A new dry technique has been developed that is faster than the wet technique reported in the previous paper to synthesize aluminum/poly(acrylic acid) membranes. It is based on casting a solution containing both the aluminum salt and the unneutralized poly(acrylic acid) (PAA) and subjecting the cast film to a heat treatment (curing step) to promote ionic crosslinking. Postcuring treatment in nonsolvents for PAA such as acetone induced structural modifications in the membrane. Membranes with optical clarity ranging from colorless and transparent to white and opaque were obtained and were characterized by their water and aluminum contents. Transport properties of these membranes were investigated and indicated a selective rejection of ionic solutes such as NaCl compared to organic solutes such as ethylene glycols. Typical results for reverse osmosis under static conditions at fluxes of 1250 g/hm² (0.75 U.S. gallons/ft²-day) gave rejections of 85% for a feed of 0.1% (by wt.) NaCl at 600 psi. Much lower rejection (28%) for ethylene glycol suggests the possible use of these membranes in the fractionation of mixtures of ionic and nonionic solutes by reverse osmosis.     

Sulfonated poly(ether ether ketone)‐induced porous poly(ether sulfone) blend membranes for the separation of proteins and metal ions

Asymmetric ultrafiltration (UF) membranes were prepared by the blending of poly(ether sulfone) (PES) and sulfonated poly(ether ether ketone) (SPEEK) polymers with N,N′‐dimethylformamide solvent by the phase‐inversion method. SPEEK was selected as the hydrophilic polymer in a blend with different composition of PES and SPEEK. The solution‐cast PES/SPEEK blend membranes were homogeneous for all of the studied compositions from 100/0 to 60/40 wt % in a total of 17.5 wt % polymer and 82.5 wt % solvent. The presence of SPEEK beyond 40 wt % in the casting solution did not form membranes. The prepared membranes were characterized for their UF performances, such as pure water flux, water content, porosity, and membrane hydraulic resistance, and morphology and melting temperature. We estimated that the pure water flux of the PES/SPEEK blend membranes increased from 17.3 to 85.6 L m^?2 h^?1 when the concentration of SPEEK increased from 0 to 40 wt % in the casting solution. The membranes were also characterized their separation performance with proteins and metal‐ion solutions. The results indicate significant improvement in the performance characteristics of the blend membranes with the addition of SPEEK. In particular, the rejection of proteins and metal ions was marginally decreased, whereas the permeate flux was radically improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Separation of benzene/cyclohexane by pervaporation through chelate poly(vinyl alcohol)/poly(allyl amine) blend membrane

Summary Chelate poly(vinyl alcohol)/poly(allyl amine) blend membrane was prepared and used for the separation of benzene/cyclohexane mixture by pervaporation processes. The coordination of benzene in the feed with cobalt in the membrane plays a major role in the separation of the mixture. Chelate poly(vinyl alcohol)/poly(allyl amine) blend membrane showed a preferential sorption toward benzene and was found to be more effective for permeating benzene in the benzene/cyclohexane mixture than an original Schiff base poly(vinyl alcohol)/poly(allyl amine) membrane.     

Investigation of the interpolymer association between poly(vinyl alcohol) and poly(sodium styrene sulfonate) in aqueous solution

A viscosimetric method has been used to study the interpolymer association between poly(vinyl alcohol) (PVA) and poly(sodium styrene sulfonate) (PSSNa) in aqueous solution. At constant molecular weight of PSSNa, it was found that, the PVA and PSSNa associations were improved with the decrease of molecular weight of PVA and the decrease of its hydrolysis degree. The measurement of intrinsic viscosity [η] and the determination of Huggins associative coefficient K_H of different PVA samples were used to select the most appropriate PVA sample, which leads to homogeneous polymer–polymer mixtures (PVA with hydrolysis degree 87–89%, molecular weight 124,000–186,000 g/mol, intrinsic viscosity [η] = 1.02 dL/g, and Huggins associative coefficient K_h.ass = 0.76). The obtained results show that the interpolymer association between PVA and PSSNa, in aqueous solution, is mainly due to intermolecular hydrogen bonds between hydroxyl groups of PVA and sulfonate groups of PSSNa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Incorporation of multiwalled carbon nanotubes into poly(vinyl alcohol) membranes for use in the pervaporation of water/ethanol mixtures

Multiwalled carbon nanotube (MWNT)/poly (vinyl alcohol) (PVA) blend membranes were prepared by the solution‐casting method to determine the effect of MWNTs with nanoscale empty inner space along the tube length on the pervaporation performance of a PVA membrane in the separation of alcohol/water mixtures. The blend membranes were then characterized with several analytical methods such as transmission electron microscopy, differential scanning calorimetry, and X‐ray diffractometry: Transmission electron microscopy showed that the MWNTs were homogeneously distributed through the PVA matrix. The glass‐transition temperature of the PVA membrane was increased from 69.21 to 78.53°C via blending with MWNTs. The crystallinity of the PVA matrix decreased with increasing MWNTs up to 5 wt % from 41 to 36%. The pervaporation properties of the blend membranes were completely different from those of the pure PVA membrane in the separation of water/ethanol mixtures. The flux of the membrane was increased with the amount of MWNTs, whereas the separation factor was maintained up to 1.0 wt % MWNTs. However, beyond that, it was reduced. These results suggested that two factors, the crystallinity of the membrane and the diameters of the MWNTs, affected the performance of the membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements Part 4. Radical polymerization of acrylic acid in the presence of poly(vinyl alcohol): characterization of resulting polymer blends

The radical polymerization of acrylic acid in the presence of poly(vinyl alcohol) as a template in aqueous solution has been studied using conductimetry, which shows template influences on the reaction rate. A comparison is made between data obtained by differential scanning calorimetry and infrared spectroscopy for poly(acrylic acid)–poly(vinyl alcohol) blends prepared either by template polymerization or by casting of the preformed polymers. Evidence for more significant interpolymer interactions in blends prepared by template polymerization than in those obtained by simple mixing is given. © 2001 Society of Chemical Industry     

Nylon 4/PVA blend membrane for dialysis

To improve the hydrophilicity and enhance the transport flux of nylon 4 membrane for dialysis, this study attempts to utilize blending nylon 4 with poly(vinyl alcohol) (PVA). The instability of PVA in water can be obtained more easily than by other methods, such as chemical, γ-ray irradiated crosslinking, or high-temperature treatment used by previous researchers. The effects of maturation time of the casting solution, nylon 4/PVA ratios, and casting solvent compositions on esterification of PVA, salt permeability, water content, partition coefficient, diffusivity, and mechanical strength of membrances are studied. The membrane, prepared by casting solution of nylon 4/PVA = 9/1 wt % formic acid with 24-h maturation time, possesses permeabilities of NaCl and urea, 33.14 and 19.67 × 10^?5 cm²/min, respectively.     

Development of stable and active PVA‐PSSA/SA‐PVA catalytic composite membrane for esterification enhancement

An active and stable catalytic composite membrane (CCM), poly(vinyl alcohol)–poly(styrene sulfonic acid)/sodium alginate–poly(vinyl alcohol) (PVA‐PSSA/SA‐PVA), was prepared to enhance the esterification of ethanol and propionic acid. The morphologies and crystal structures of the CCMs were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray diffraction. The effects of catalytic layer thickness, mass ratio of PVA to PSSA, concentration of catalytic layer solution, ratio of reaction volume to membrane area, and molar ratio of propionic acid to ethanol were discussed. The pervaporation results showed that the flux of CCM increased from 118 to 320 g m^?2 h^?1 compared with the SA‐PVA membrane because of the close affinity and low resistance of PSSA to water. After crosslinking with 3‐aminopropylmethyldiethoxysilane, the CCMs had good catalytic activities. The acid conversion reached 92.8% at 75 °C in 12 h, and the stabilization of the CCM was greatly improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46514.     

Preparation of hydroxyapatite/poly(vinyl alcohol) composite film with uniformly dispersed hydroxyapatite particles using citric acid

Biocompatible hydroxyapatite (HA)/poly(vinyl alcohol) (PVA) composites and their transparent films were prepared by the coprecipitation and solvent casting method. The formation of HA in PVA composite powder was confirmed by the characteristic phosphate bands at 1100–1032 and 565 cm^?1 at FT‐IR spectra, and the weight ratio of HA to PVA was 50/50 examined by TGA. The crystal melting temperature of HA/PVA decreased compared with that of pure PVA. HA/PVA (50/50) composite powder and pure PVA were dissolved in dimethyl sulfoxide to obtain a film with HA/PVA weight ratio of 10/90. To improve HA particles' dispersity, which is one of the major factors affecting the mechanical properties of composite materials, various contents of citric acid were used for the preparation of HA/PVA films. At a citric acid concentration of 5 wt %, HA/PVA film with good dispersity of HA particles was obtained. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Miscibility of conductive blends of poly(o-anisidine) with poly(2-alkyl-2-oxazoline)s

HCl-doped poly(o-anisidine) (PANIS–HCl) and undoped poly(o-anisidine) (PANIS-base) were blended with poly(2-methyl-2-oxazoline) (PMOx) or poly(2-ethyl-2-oxazoline) (PEOx) by solution casting from dimethyl sulfoxide. Blends containing 50 wt % or less of PANIS–HCl or PANIS-base were flexible and homogeneous. The glass transition temperature of the blend continuously shifted away from that of PMOx or PEOx with increasing PANIS–HCl or PANIS-base content, indicating miscibility. The shift in the T_g value was larger for the PMOx blend than for the corresponding PEOx blend, suggesting a stronger interpolymer interaction in the former blend. Fourier transform infrared spectroscopic studies indicated the presence of specific interactions in the blends as evidenced by the changes of C=O and NH bands. Blends containing 50 wt % of PANIS–HCl showed conductivity of about 10^-4 S/cm. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:391–397, 1997     

Phase structure in the blend of atactic poly(vinyl alcohol) with atactic poly(vinyl alcohol‐block‐vinyl acetate)

An almost fully saponified atactic poly(vinyl alcohol) and an atactic poly(vinyl alcohol‐block‐vinyl acetate) of which degree of saponification is 89 mol % were blended by a solution casting method. The phase structure of the blend film was analyzed by optical microscopy, ¹³C‐NMR, and differential scanning calorimetry. The most remarkable structure of the blend was composed of cylindrical domains penetrating the film. The swelling behavior of the blend films was also investigated in the dimethylsulfoxide and water mixed solvents to find differences in solubility and diffusion behavior between the matrix and the domain. The cylindrical domains could be selectively dissolved away in water and the film became porous. We tried to change the size of the cylindrical domain with various film preparation conditions. This aimed to turn the film into the useful filter membrane. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1807–1815, 2002     

Preparation and characterization of PSSA/PVA catalytic membrane for biodiesel production

Poly(styrene sulfonic acid) (PSSA)/Poly(vinyl alcohol) (PVA) blend membranes prepared by the solution casting were employed as heterogeneous acid catalysts for biodiesel production from acidic oil obtained from waste cooking oil (WCO). The membranes were annealed at different temperature in order to enhance their stability. The structure and properties of the membranes were investigated by means of Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), X-ray diffraction (XRD). It is found that the crosslinking structure among PVA and PSSA chains formed when the thermal treatment temperature was higher than 80 °C. The retention of PSSA in the blend membranes in the methanol/water solvent was markedly increased from 50% to 85% with the increase of the annealing temperature from room temperature (for the untreated membrane) to 150 °C due to the formation of the crosslinking structure. The results of esterification of acidic oil show that the conversion was slightly improve with the PVA content in the membrane at a fixed PSSA content. The thickness of the catalytic membrane had no significant effect on the conversion in the end. The membrane annealed at 120 °C exhibited the best catalytic performance among the membranes, with a stable conversion of 80% with the runs.     

Pervaporation of water-ethanol through poly(vinyl alcohol)/chitosan blend membrane

Summary Blend membrane consisting of poly(vinyl alcohol)(PVA) and chitosan was prepared from solvent casting technique for effective separation of ethanol-water mixture by pervaporation. Selectivity toward water and the flux through the blend membrane, crosslinked with glutaraldehyde at the concention of 4×10^-6 mol/g, were450 and 0.47 kg/m².hr, respectively.     

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.     

Blends of poly(vinyl butyral‐co‐vinyl alcohol) and poly(ethylene terephthalate‐co‐ethylene naphthalate): thermal,mechanical, and morphological properties

The miscibility behavior and morphology of a series of poly(vinyl butyral‐co‐vinyl alcohol) (PVBA) copolymers containing 29, 52, 76, and 88 mol % of vinyl alcohol units with poly(ethylene terephthalate‐co‐ethylene naphthalate) (PETN) was investigated by DSC and SEM. Blends of the PETN with PVBA were prepared by coprecipitation from a chloroform/o‐chlorophenol (20/80 wt %) mixture solvent. It was found that PVBAs with different vinyl alcohol content will form an immiscible phase with the amorphous PETN in the solution‐cast films. Also, PETN and PVBA with 29 mol % vinyl alcohol (PVBA‐29) are not miscible within the whole composition range. The glass‐transition temperatures of the blends were higher than those of the two‐component polymers. The values of the tensile properties of the blend films were also better than those of the original copolymer films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2746–2751, 2001     

Chelate membrane from poly(vinyl alcohol)/poly(N-salicylidene allyl amine) blend. III. Effect of Mn(II) and Co(II) on oxygen/nitrogen separation

Facilitated transport of oxygen through Co(II) and Mn(II) chelate membranes from poly(vinyl alcohol)/poly(N-salicylidene allyl amine) was investigated. As the membranes became chelated, oxygen diffusivity decreased and the solubility toward oxygen was enhanced. The oxygen permeability of the base poly(vinyl alcohol)/poly(N-salicylidene allyl amine) membrane was 2.6 × 10⁻³ cm³(STP)cm/cm² cm Hg sec (barrer), and the selectivity toward oxygen was 2.2. As Co(II) was introduced into this membrane, oxygen permeability and oxygen selectivity increased to 2.82 × 10⁻² barrer and 8.5, respectively. The permeability and selectivity of Mn(II) chelate membrane were 3.28 × 10⁻² and 5, respectively. A major reason for the increased selectivity was the enhanced solubility of oxygen in chelate membrane upon chelation. The transport behavior of chelate membranes followed a dual-mode transport, and the parameters were estimated and compared between Co(II) and Mn(II) membranes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 483–490, 1997