D. Mohan

Preparation and performance of cellulose acetate–polyurethane blend membranes and their applications – II

Abstract Characterization and application of ultrafiltration membranes are of great interest today, both as a tool in choosing the proper membrane for the filtration system used and in the development of new and better membranes. Cellulose acetate was blended with polyurethane in a polar solvent in the presence of polyvinylpyrrolidone as an additive. The effects of polymer composition and additive concentration on membrane compaction, pure water flux, water content, membrane hydraulic resistance and morphological studies were discussed. Measurement of transmembrane flux and appropriate macro solute rejection during stirred ultrafiltration of aqueous solutions of proteins and metal ions chelated with polyethyleneimine were carried out individually using CA/PU blend membranes.

Ultrafiltration application of cellulose acetate–polyurethane blend membranes

Abstract Cellulose acetate membranes are widely used for reverse osmosis and ultrafiltration applications. Cellulose acetate membranes were prepared by solution blending of cellulose acetate with polyurethane in polar solvent. The effect of varied concentrations of additive, polyvinylpyrrolidone, on the performance of modified cellulose acetate/polyurethane blend membranes was studied. The cellulose acetate/polyurethane membranes were characterized based on pure water flux, compaction, water content, morphological studies and applied for proteins separations by ultrafiltration technique and are discussed in detail.

Modification of Cellulose Acetate: Its Characterization and Application as an Ultrafiltration Membrane

The development of cellulose acetate blend membranes using a commercial grade Mycell cellulose acetate and cellulose diacetate with suitable pore structure is discussed. These membranes were characterized in terms of resistance of the mem- brane, pure water flux, the molecular weight cutoff, water content, pore size, and porosity. The removal of copper metal ions by this blend membrane using polyethylene- imine as a chelating agent was studied. The effects of copper ion concentration and casting solution composition on separation are also discussed. A possible correlation between feed and permeate concentration of copper ion is evaluated. q 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 1939-1946, 1998

Preparation, characterization and effect of annealing on performance of cellulose acetate/sulfonated polysulfone and cellulose acetate/epoxy resin blend ultrafiltration membranes

Abstract Polymeric membranes based on cellulose acetate (CA)––sulfonated polysulfone blends at three different polymer compositions were prepared by solution blending and phase inversion technique, characterized and subjected to annealing at 70, 80 and 90 °C. The permeate water flux, separation of bovine serum albumin and its flux by the blend membranes before and after thermal treatment, have been compared and discussed. Similarly, CA and epoxy resin (diglycidyl ether of bisphenol-A) were blended in various compositions, in the presence and in the absence of polyethyleneglycol 600 as non-solvent additive, using N , N ′ -dimethylformamide as solvent, and used for preparing ultraflltration membranes by phase inversion technique. The polymer blend composition, additive concentration, casting and gelation conditions were optimized. Blend membranes were characterized in terms of compaction, pure water flux, water content and membrane resistance. The effects of polymer blend composition and additive concentration on the above parameters were determined and the results are discussed.

Studies on cellulose acetate–carboxylated polysulfone blend ultrafiltration membranes––Part I

Abstract Hydrophilic polysulfone ultrafiltration (UF) membranes were prepared from blends of cellulose acetate with carboxylated polysulfone of 0.14 degree of carboxylation. The effects of blend polymer composition on compaction, pure water flux, water content and membrane hydraulic resistance ( R m ), have been investigated to evaluate the performance of the membranes. The performance of the blend membranes of various blend polymer compositions were compared with that of membranes prepared from pure cellulose acetate and blends of cellulose acetate and pure polysulfone. The hydrophilic cellulose acetate–carboxylated polysulfone blend UF membranes showed better performance compared to membranes prepared from pure cellulose acetate and blends of cellulose acetate and pure polysulfone.

Structure-property interplay of poly(amide-imide) and TiO2 nanoparticles impregnated poly(ether-sulfone) asymmetric nanofiltration membranes

Poly(amide-imide) (PAI) and TiO2 nanoparticle-incorporated poly(ether-sulfone) (PES) asymmetric nanofiltration membranes with an integrally dense skin layer were prepared by diffusion induced phase separation. The prepared membranes were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), pure water flux, water content and contact angle technique to investigate the influence of PAI on the properties of the membranes. Intermolecular interactions between the components in blend membranes were established by ATR-FTIR and microcrystalline morphology was confirmed by XRD. The SEM analysis showed that blend membranes have an integrally dense skin layer adequate for nanofiltration and a spongy sub-layer along the entire membrane cross section. The contact angle measurements indicated that, hydrophilicity of the virgin PES membranes was improved by the addition of PAI and TiO2 nanoparticles due to the preferential orientation of these components towards the membrane surface during immersion precipitation. Surface free energy parameters of the membrane such as surface free energy, interfacial free energy, work of adhesion and spreading coefficient were calculated. The efficiency of these membranes in the separation of mixture solutions of divalent salt and surfactant were found to be improved significantly. Fouling stability of the membranes studied by bovine serum albumin (BSA) as the model foulant revealed improved fouling resistance. Chlorine stability of the modified membranes was also investigated. From the results, it was revealed that low interfacial free energy membranes prepared by the incorporation of PAI and TiO2 nanoparticles may be valuable in fouling stability industrial separations.

Preparation and performance of cellulose acetate-polyurethane blend membranes and their applications. Part 1

Ultra-ltration gains signi-cance when certain chemical species, such as proteins and some toxic heavy metal ions, present in low concentration, have to be selectively removed from a mixture. Separation of metal ions by complexation with macromolecular binding agents and rejection of proteins such as bovine serum albumin, egg albumin, pepsin and trypsin was studied using cellulose acetateEpolyurethane blend ultra-ltration membranes. The inNuence of the com- position of the polymers in blend membranes on the separation of metal ions and proteins is discussed. The blend membranes were also characterized by pure water Nux, water content, membrane hydraulic resistance, molecular weight cut-o† and scanning electron microscopy. The separation of proteins was found to be directly proportional to the molecular weight of the proteins, while the Nux displayed an opposite trend, and copper was found to have a higher separation capability than nickel, zinc and cadmium. Society of Chemical Industry ( 1998 Polym. Int. 47, 311E316 (1998)

Uranium transport using a PTFE flat-sheet membrane containing alamine 336 in toluene as the carrier

Abstract Transport of uranyl ion from HCl medium was investigated using 0.2 micron PTFE filters as the membranesupport and 30% alamine 336 in toluene as the carrier while distilled water was used as the strippant. In an experimentcarried out to understand the effect of the organic diluents, the observed trend was toluene > t-Bu-benzene > chloroform > 1,2-dichloroethane > hexane > 1-decanol. In view of the higher transport of uranyl ion with tolueneas the diluent, all subsequent experiments were carried out using toluene. The permeability coefficient values increased with increasing HCl concentration (1 M HCl: 6.53×10 −4 cm/s; 6 M HCl: 2.56×10 −3 cm/s) suggesting the extraction of anionic species into the membrane phase. The permeation of ion pairs is expected to be higher for more polar diluents such as CHCl 3 and 1,2-dichloroethane. However, the lower trend observed with these diluents as compared to aromatic diluents such as toluene or t-butyl benzene was ascribed to H-bonded interaction with thecarrier. In order to optimize the carrier concentration an experiment was carried out at varying concentration ofalamine 336 in toluene. Maximum transport rate was observed with 20% (v/v) alamine 336 in toluene as the carrier ( P = 3.33×10 −3 cm/s). Though an increase in transport rate (5% to 20% alamine 336) is expected with increasingcarrier concentration, the decrease beyond 20% alamine 336 is attributed to the increased viscosity of the carriersolution which retards metal diffusion. The effect of membrane pore size was studied using four different membranes with varying pore sizes. A sharp decrease in the transport rate with increasing membrane pore size was observed ( P = 2.56×10 −3 cm/s for 0.2 micron pore size; P = 6.78×10 −4 cm/s for 5.0 micron pore size).

Preparation and Characterization of Cellulose Acetate/Aminated Polysulfone Blend Ultrafiltration Membranes and their Application Studies

Abstract Ultrafiltration membranes are largely being applied for heavy metal ion separations from aqueous streams. Cellulose acetate (CA) and aminated polysulfone (APSf) based membranes are prepared in the absence and presence of the polymeric additive, polyethylene glycol, PEG 600, in various compositions. The effects of polymer blend composition and additive concentration on compaction, pure water flux, membrane hydraulic resistance, water uptake, and contact angle has been investigated to evaluate the performance of the membranes and the results are discussed. Surface and cross-sectional morphologies of membranes were also analyzed using scanning electron microscopy. Toxic heavy metal ions such as Cu2+, Ni2+, Cd2+, and Zn2+ were separated by the blend membranes using polyethyleneimine (PEI) as polymeric ligand. The rejection and permeate flux efficiencies of the blend membranes are compared with pure cellulose acetate membranes.

Preparation and performance evaluation of poly (ether-imide) incorporated polysulfone hemodialysis membranes

Biocompatible Polysulfone (PSf) hemodialysis membranes were prepared by phase inversion technique using poly (ether-imide) (PEI) as the modification agent and Polyethylene glycol (PEG-200) as the pore former. The effect of PSf/PEI blend ratio on the morphology, hydrophilicity, water content, porosity, glass transition temperature, mechanical strength, biocompatibility and permeation rate of the prepared membranes were studied and were found to be improved significantly by the incorporation of PEI in the dope solution. The scanning electron microscopy (SEM) studies revealed that, incorporation of PEI resulted in the formation of spongy sub-layer and increased the connectivity of pores between sub-layer and bottom layer. The water content and permeation rate of the membranes of PSf/PEI blend membranes were increased considerably indicating the enhancement of hydrophilicity and it was supported by lower contact angle values of the blend membranes. The existence of single well defined Tg over entire composition established the compatibility between the components in blend membranes. The biocompatibility of membranes was investigated through protein adsorption, platelet adhesion and thrombus formation on the membrane surface. Anticoagulant activity of PSf/PEI blend membranes was evaluated by measuring the activated partial thrombin time (APTT), prothrombin time (PT), thrombin time (TT) and fibrinogen time (FT). The results revealed that antithrombogenicity of PSf/PEI blend membranes was increased significantly. The efficiency of these membranes in removal of urea, creatinine and vitamin B12 were studied and found to be improved for blend membranes. Thus, it is worth mentioning to note that, the biocompatible PSf/PEI blend membranes prepared in this study would offer immense potential in hemodialysis.