Characterization of cellulose triacetate membranes, produced from sugarcane bagasse, using PEG 600 as additive

Cellulose Acetate (CA) produced from sugarcane bagasse cellulose was used to produce membranes, using poly(ethylene glycol) (PEG 600) as additive. Results showed that PEG 600 was washed out the membranes during the preparation step. Thermal Analysis showed that the temperature of degradation of the membranes increased in 10 °C when PEG 600 was added to the composition, but did not change as more PEG 600 was added in the composition. On the other hand, the crystalline content (%C) of the membranes increased as PEG 600 was added. The addition of PEG 600 also increased the resistance of the membranes to pressure and the pure water flux rate, but membranes produced with PEG 600 content lower than 5% did not present water flux. PEG 600 also increased the coefficient of ion diffusion of the membranes.     

Effects of solubility parameter differences among PEG,PVP and CA on the preparation of ultrafiltration membranes: Impacts of solvents and additives on morphology,permeability and fouling performances

The effects of two different hydrophilic additives and two solvents on the membrane morphological structure,permeability property and anti-fouling performances of cellulose acetate (CA) ultrafiltration membranes were investigated.During the phase-inversion process,cellulose acetate was selected as a membrane forming polymer;polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) were used as additives;acetone (Ac):N,N-Dimethylacetamide (DMAc) andN,N-Dimethylformamide (DMF) were used as solvents;and deionized (DI) water was used in the coagulation bath.All the prepared membranes were characterized in terms of hydraulic permeability (Pm),membrane resistance,average pore radius,and hydrophilicity.The top surface and crosssectional view of the prepared membranes were also observed by using field emission scanning electron microscopy.Membrane fouling and rejection experimentations were done using a stirred batch-cell filtration set-up.The experimental studies of fouling/rinsing cycles,rejection,and permeate fluxes were used to investigate the effect of PEG and PVP additives and effect of the two solvents on the fabricated membranes using bovine serum albumin (BSA) as a model protein.     

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.     

Effect of additives concentration on performance of cellulose acetate and polyethersulfone blend membranes

Asymmetric micro porous membranes have been prepared successfully from blending of cellulose acetate (CA) and polyethersulfone (PES) by the phase inversion method with N, N-dimethylformamide (DMF) as solvent. Two additives were selected in this study, including polyethylene glycol 600 (PEG 600) and polyvinylpyrrolidone (PVP). The effects of concentration of additives on CA/PES blend membrane performance and cross-section morphology were investigated in detail. CA/PES membranes were compared with CA/PES/PEG and CA/PES/PVP membranes in the performance such as pure water flux, membrane resistance, porosity and cross-section morphology. The resulting blend membranes were also carried out the rejection and permeate flux of Egg Albumin (EA) proteins with molecular weight of 45 Da. The membranes thus obtained with an additive concentration of 5 wt% of both PEG and PVP exhibited superior properties than the 80/20% blend composition of CA and PES membranes. The permeate flux of protein was increased from 44 to 134 lm² h with increase in concentrations of both PVP and PEG in 80/20% blend composition of CA and PES membranes. Cross-sectional images from scanning electron microscopy showed larger macropores in the bottom layer of the membranes with increasing additives content. Observations from scanning electron microscopy provided qualitative evidence for the trends obtained for permeability and porosity results.     

Studies on Cellulose Acetate/Low Cyclic Dimmer Polysulfone Blend Ultrafiltration Membranes and their Applications

Abstract

Flat sheet ultrafiltration membranes from cellulose acetate (CA)/low cyclic dimer polysulfone (LCD PSf) were prepared by a phase inversion method. N, N′‐Dimethyl formamide and different molecular weight of polyethylene glycol (PEG 200, PEG 400, and PEG 600) were used as solvent and pore‐forming additive, respectively. The membranes were characterized in terms of pure water flux, water content, porosity, membrane hydraulic resistance, and morphology. The pure water flux was found to reach the highest value of 181.82 Lm^?2h^?1 at 5 wt.% PEG of 600 molecular weight and 10 wt.% LCD PSf content in the blended solution for membrane preparation. SEM micrographs indicated that the addition of PEG into the CA/LCD PSf solution changes the inner structure of the membrane. The influence of filtration time and applied pressure on membrane permeability was examined by copper/polyethylenimine complex rejection studies. With increase in filtration time, the rejection of the copper/polyethylenimine complex decreased and the results were discussed.     

Effect of Poly(ethylene glycol) on Separations by Cellulose Acetate/poly(ether imide) Blend Membranes

Ultrafiltration membranes are largely being applied for macromolecular and heavy metal ion separations from aqueous streams. In this study, cellulose acetate (CA) and polyetherimide (PEI) based ultrafiltration blend membranes prepared in the absence and presence of poly(ethylene glycol) 600 (PEG 600) in various compositions were subjected to the separation of macromolecular proteins such as bovine serum albumin (BSA), egg albumin (EA), pepsin and trypsin. Toxic heavy metal ions such as Cu(II), Ni(II), Zn(II) and Cd(II) were subjected to separation by the blend membranes by complexing them with the polymeric ligand polyethyleneimine. The effects of polymer blend compositions and additive concentrations on the rejection and permeate flux of both proteins and metal ions are discussed. In general, it was found that CA/PEI blend membranes displayed higher permeate flux and lower rejection compared to pure cellulose acetate membranes at all additive concentrations. The extent of separation of proteins was found to be directly proportional to the molecular weight of the protein, while the extent of removal of metal ions depends on the affinity of metal ions to polyethyleneimine and the stability of the formed complexes.     

Production and characterization of membranes of recycled waste materials: Cellulose acetate,obtained from sugarcane bagasse with polystyrene from plastics cups

Membranes of cellulose acetate from sugarcane bagasse (CA), as well as blends of this cellulose acetate and polystyrene from plastic cups (CA/PS) were produced by casting utilizing dichloromethane as solvent at the concentration 12% w/w. The membranes were characterized regarding ion diffusion by dialysis and properties of pure water permeation rate, PEG rejection (utilizing an aqueous solution 1% w/v of polyethylene glycol (PEG), 45 and 80 kDa). Thermal characterization by thermogravimetric analysis and differential scanning calorimetry were also performed. The morphology of the membranes' cross‐sections was evaluated by scanning electron microscopy. The experiment of ion diffusion by dialysis showed that the ion diffusion coefficient of CA membrane is comparable to that found in the literature for membranes of commercial cellulose triacetate, 8.47 × 10^?8 cm² s^?1, while the ion diffusion coefficient of blends decreased as PS was added to the system. Regarding transport driven by pressure, CA membrane presented low rejection of PEG 80 kDa. These results showed that CA membrane could be used in a range of application comprehending the process of ultrafiltration or microfiltration. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Protein separation by cellulose acetate/sulfonated poly(ether imide) blend ultrafiltration membranes

A process for purifying aqueous solutions containing macromolecular proteins such as bovine serum albumin (BSA), egg albumin (EA), pepsin, and trypsin has been investigated. Protein removal from food and biorelated industrial waste streams are gaining increased visibility due to environmental concern and saving precious materials. Ultrafiltration (UF) processes are largely being applied for protein separation from aqueous streams. In this work, an attempt has been made to separate the valuable proteins using cellulose acetate (CA)/sulfonated poly(ether imide) (SPEI) blend UF membranes prepared in the absence and presence of the additive, polyethyleneglycol (PEG600) in various compositions. The blend membranes were subjected to the determination of pore statistics and molecular weight cut‐off (MWCO). Porosity and pore size of the membranes increased with increasing concentrations of SPEI and PEG600 in the casting solution. Similarly, the MWCOs of the blend membranes ranged from 20 to greater than 69 kDa, depending on the various polymer blend compositions. Surface morphology of the blend membranes were analyzed using scanning electron microscopy. Studies were carried out to find the rejection and permeate flux of proteins. On increasing the concentration of SPEI and PEG600, the rejection of proteins is decreasing, whereas the permeate flux has an increasing trend. The effect of hydrophilicity of SPEI on fouling of protein for CA/SPEI blend membranes was also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Application Studies of Cellulose Acetate and Polymethylmethacrylate Blend Ultrafiltration Membranes

The preparation of novel membranes based on cellulose acetate and polymethylmethacrylate blends in the absence and presence of the pore former by solution blending and ultrafiltration set up was carried out. The effect of compaction time on pure water flux at higher transmembrane pressure for various polymer compositions of the above blends both in the presence and absence of the pore former PEG 600 at different concentrations were reported for individual polymer blends. The pure water flux at 345 kPa, Molecular weight cut-off (MWCO). The application of the characterized CA/PMMA blend membranes for the separation of proteins such as Bovine Serum albumin, Egg Albumin, Pepsin, and Trypsin, and toxic heavy metals such as Cu(II), Ni(II), and Zn(II) using polyethyleneimine as complexing agent have been attempted and the results indicate the efficiency of the ultrafiltration blend membranes.     

Studies on Permeation,Rejection, and Transport of Aqueous Poly(ethylene Glycol) Solutions using Ultrafiltration Membranes

Abstract

The permeate flux and retention of aqueous solutions of poly(ethylene glycols) (PEG) with different molecular weights ranging from 4000 to 35,000 Da have been investigated using various compositions such as 100/0, 90/10, 80/20, and 70/30 wt% of cellulose acetate (CA)/sulfonated poly(etheretherketone) (SPEEK) ultrafiltration blend membranes. The factors affecting the rejection rate and permeate flux such as molecular weight of PEGs, concentration of the solute, composition of the membranes, and transmembrane pressures have been studied. It is seen that the increase in the concentration of PEG results in the decreased permeate flux and increased rejection for increasing CA content in the membranes. A similar observation in the flux and rejection was made for increasing the molecular weight of PEGs. Further, the mass transfer, diffusion, and true retention coefficients of the solute have been studied with different operating variables like molecular weight and concentration of PEGs. An increase in the molecular weight of PEGs results in the decrease of mass transfer and diffusion coefficients and increase of the true retention coefficient. A reverse trend is observed with increasing concentrations of PEG.     

The effect of short air exposure periods on the performance of cellulose acetate membranes from casting solutions with high cellulose acetate content

Highly productive cellulose acetate membranes were cast under conditions of very short air exposure periods from cellulose acetate–acetone–formamide casting solutions having a high cellulose acetate (CA) content and lying close to the phase boundary. Air exposure periods as short as 0.05 sec were used with CA content up to 32 wt-%. Membranes from a casting solution containing 30 wt-% cellulose acetate (E-398-3), 45 wt-% acetone, and 25 wt-% formamide perform as well as membranes from other compositions at all salt rejection levels for a 0.5 wt-% NaCl feed at 600 psig. Partial replacement of acetone by dioxane in the casting solution substantially increases the water flux from membranes cast with short air exposure periods at any given salt rejection level below 96% salt rejection. Addition of small amounts of ZnCl₂ to nondioxane casting solutions with 32 wt-% CA improves membrane performances remarkably for lower salt rejection levels, while the improvement in performance of membranes from 30 wt-% CA casting solutions with dioxane due to ZnCl₂ addition is marginal. Variation in air exposure from 0.05 to 2 sec results in minor performance variations in the membranes having any of these compositions. With air exposure periods beyond 2–3 sec, membrane fluxes drop drastically. The concept of a thinner skin satisfactorily explains the improvement in mixed solvent systems, whereas ZnCl₂ acts as a swelling salt. A Kimura-Sourirajan-type membrane performance plot indicates that for a 0.5 wt-% NaCl feed at 600 psig, membranes of the present work perform as well as the best performing membranes reported in the literature for conversion of brackish water.     

NMMO工艺纤维素膜结晶度与强度性能初探

以纤维素为原料,N-甲基吗啉-N-氧化物(NMMO)为溶剂,采用相转化法制备非对称纤维素膜。利用X-射线衍射仪对NMMO工艺纤维素膜的结晶状况进行检测,并利用拉力机检测出薄膜的拉伸强度。结果表明:随着铸膜液中纤维素含量的增加,薄膜结晶度与拉伸强度均提高;随着溶解纤维素的温度提高,薄膜结晶度与拉伸强度降低;随着刮膜剪切力增大,薄膜结晶度和拉伸强度提高;并且薄膜结晶度的增加有利于薄膜拉伸强度的提高。     

Structural characteristics and state of water in an acetate cellulose membrane

Experimental data have been obtained and an analysis has been performed of the degree of crystallinity and amorphism and the state of water for cellulose acetate membranes using the methods of X-ray diffraction (XRD), infrared spectroscopy and thermogravimetry. The degree of crystallinity, as well as the crystallite size, have been determined in the membrane samples before and after water absorption. It has been found that OH groups of cellulose acetate form a nonequilibrium network of hydrogen bonds between molecules and fragments in the amorphous phase of an air-dry semipermeable membrane. It has been shown that water that acts as a plasticizer causes the ordering of the macromolecular amorphous phase, which leads to a transition into the liquid crystal phase with the formation of additional capillary spaces.     

Studies on Performance of Cellulose Acetate and Poly(Ethelene Glycol) Blend Ultrafiltration Membranes Using Mixture Design Concept of Design of Experiments

Cellulose acetate (CA) membranes have several advantages over other membranes due to their moderate flux, high salt rejection properties, renewable source of raw material, etc. Membrane compositions containing different concentrations of CA, polyethylene glycol (PEG 600) as additive and N,N–dimethyl formamide (DMF) as solvent have been prepared using phase inversion technique based on the mixture design concept of design of experiments. The prepared membranes have been characterized for permeate flux, membrane hydraulic resistance, and separation of proteins such as pepsin, egg albumin (EA), and bovine serum albumin (BSA). Using statistical techniques, the experimental data have been analyzed and a suitable model was suggested for predicting the optimal level of response as a function of the input variable. The influence of variation of the CA, DMF, and PEG 600 on the asymmetric membrane properties has also been reported.     

Water flux through blends from waste materials: Cellulose acetate (from sugar cane bagasse) with polystyrene (from plastic cups)

In the present work we blended cellulose acetate (taken from sugar cane bagasse) (CA) with polystyrene (taken from postconsumer plastic cups) (PS). The blends were produced in the following ratios (w/w) of the polymers: CA 50%/PS 50%, CA 90%/PS 10%, and CA 10%/PS 90%, using dichloromethane as solvent. The blends were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. The results show that the presence of polystyrene hinders the organization of regions responsible for the crystallinity originally existing in pure cellulose acetate. We also made measurements of water flux through blends, using the Payne cup technique. The flux properties were compared with those obtained for commercial membranes by Osmonix: nanofiltration (SG) and reverse osmosis (CG). The results show that the blend CA 90%/PS 10% presents water vapor flux comparable with that of commercial membranes for nanofiltration (SG). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 516–522, 2005     

Effect of additives on the properties and performance of cellulose acetate derivative membranes in the separation of isopropanol/water mixtures

In this work, various cellulose acetate (CA) membranes for pervaporation were prepared by the incorporation of different additives, i.e. polyethylene glycol-600 (PEG-600), propylene glycol (PG), and ethylene glycol (EG) to enhance the separation of isopropanol (IPA)/water mixtures. These membranes were characterized by FTIR, DSC, TGA, SEM and UTM. Each additive was responsible for its characteristic effect on the membrane morphology, mechanical strength, permeation flux and separation factor. The SEM micrograph showed that the additives were evenly dispersed in the membrane matrix with the formation of dense membranes. The UTM tests for the membrane reveled that both the Young's Modulus and tensile strength increased with the increase in additive contents. TGA studies for the CA/PEG blend membrane exhibited the highest thermal stability as compared to the CA/PG and CA/EG blends. For each of these synthesized membranes, the separation factor decreased while the permeation flux increased with the increase in additive contents, while the CA/PG membrane with 20 wt.% additive content showed highest permeation flux of 452.27 g/m²h.     

Preparation of ultrathin reverse osmosis membranes and the attainment of theoretical salt rejection

Cellulose acetate reverse osmosis membranes, 600–2800 A. thick, have been prepared on glass surfaces by dipping a clean glass plate into a dilute solution of cellulose acetate. After drying, the membranes are floated of onto a water surface and placed on molecular filter supports. Theoretical salt rejections, as calculated from the solution-diffusion model of membrane transport for cellulose acetate, were obtained with imperfection-free membranes.     

Effect of Additive Concentration on Cellulose Acetate Blend Membranes-Preparation,Characterization and Application Studies

Abstract

Ultrafiltration techniques have particular advantages for simultaneous purification, concentration, and fractionation of macromolecules. A comparative study is presented on novel ultrafiltration polymeric blend membranes based on cellulose acetate (CA) prepared in the absence and presence of polymeric additives such as polyethylene Glycol 200 (PEG) and polyvinylpyrrolidone (PVP) by phase inversion technique using N,N′-dimethylformamide (DMF) as solvent. Polymer blend composition, additive concentration and casting, and gelation conditions were standardized for the preparation of asymmetric membranes by pore statistics and morphology. These blend membranes were characterized for compaction in ultrafiltration experiments at 414 kPa pressure in order to attain steady state flux and is reached within 4–5 h. The pure water flux was measured at 345 kPa pressure. Membrane hydraulic resistance derived by measuring water flux at various transmembrane pressures and found to be inversely proportional to pure water flux. Water content is estimated by simple drying and weighing procedures and found proportional to pure water flux for all the membranes. The molecular weight cut-offs (MWCOs) of different membranes were determined with proteins of different molecular weights and found to vary from 20 to 69 kDa depending on the PEG 200 and PVP content in the blend in the casting solution. Skin surface porosity of the membranes was analyzed by scanning the samples at various magnifications. The characterized CA, CA/PEG200 and CA/PVP membranes were used for cadmium ion rejection studies at 345 kPa.     

Development and performance of some porous cellulose acetate membranes for reverse osmosis desalination

The effects of casting solution composition and evaporation period on the performance of resulting porous cellulose acetate membranes have been studied, and the results are discussed in terms of casting solution structure, solvent evaporation rate during film formation, and the film shrinkage temperature profile. The development of Batch 316-type porous cellulose acetate membranes is reported. At 90% level of solute separation and feed flow conditions corresponding to a mass transfer coefficient of 45 × 10^?4 cm/sec, the productivities of the above membranes are 21.5 gallons/day/ft² at 250 psig using 3500 ppm of NaCl in the feed, and 53.9 gallons/day/ft² at 600 psig using 5000 ppm of NaCl in the feed.     

Reverse osmosis separations of polyethylene glycols in dilute aqueous solutions using porous cellulose acetate membranes

Reverse osmosis separations of eight polyethylene glycol (PEG) solutes in the average molecular weight range of 200 to 6750 in single-solute dilute aqueous solutions have been studied using porous cellulose acetate membranes at the operating pressures of 50, 75, and 100 psig. Diffusivity data for the above PEG solutes have also been obtained from experimental data on intrinsic viscosities. From an analysis of all experimental data, numerical values for the parameters representing the polar (?ΔΔG/RT), steric (δ^*ΣE_s), and nonpolar (ω^*Σs^*) forces governing reverse osmosis separations of PEG solutes have been generated. These numerical values are useful for precise characterization of cellulose acetate membranes for whose specifications sodium chloride is not the appropriate reference solute because of its low or practically negligible separation under reverse osmosis operating conditions. This work also illustrates that solute separation in reverse osmosis can predictably increase or decrease with increase in operating pressure depending on experimental conditions.