Preparation and Performance of Polysulfone‐Cellulose Acetate Blend Ultrafiltration Membrane

In the development of high performance polymeric membranes, it is essential to design the molecular and morphological characteristics for specific applications. Polysulfone and cellulose acetate of blend membranes with various concentration of polymer pore former, PEG600 were prepared by phase inversion technique and used for ultrafiltration. Polymer blend composition, additive concentration, and casting conditions were optimized. The blend membranes were characterized in terms of compaction, pure water flux, water content, hydraulic resistance and separation of dextran studies. Surface morphology of the embranes was analyzed using scanning electron microscopy at different magnifications. Further, the characterized membranes were attempted for treatment of distillery effluents after secondary treatment and the results are discussed in detail.     

Studies on cellulose acetate and sulfonated poly(ether ether ketone) blend ultrafiltration membranes

New ultrafiltration membranes based on chemically and thermally stable arylene main-chain polymers have been prepared by blending the sulfonated poly(ether ether ketone) with cellulose acetate in various compositions in N,N^′-dimethylformamide as solvent by phase inversion technique. Prepared membranes have been subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and membrane hydraulic resistance. The pore statistics and molecular weight cut-off (MWCO) of the membranes have been estimated using proteins such as trypsin, pepsin, egg albumin and bovine serum albumin. The pore size increased with increasing concentrations of sulfonated poly(ether ether ketone) in the casting solution. Similarly, the MWCOs of the membranes ranged from 20 to 69 kDa, depending on the various polymer compositions. Surface and cross-sectional morphologies of membranes were analyzed using scanning electron microscopy. The effects of polymer compositions on the above parameters were analyzed and the results are compared and discussed with those of pure cellulose acetate membranes.     

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

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.     

Cellulose acetate and polyethersulfone blend ultrafiltration membranes. Part I: Preparation and characterizations

The overall objective of this investigation is to achieve high‐performance membranes with respect to flux and rejection characteristics, with an interplay of blending polymers having desired qualities. Thus, cellulose diacetate and polyethersulfone as candidate materials, in the presence of polyethylene glycol 600 as a pore forming agent, were blended in 100/0, 95/5, 90/10, 85/15, 80,20 and 75/25% compositions using N,N′‐dimethylformamide as solvent and membranes were prepared by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were standardized for the preparation of asymmetric membranes with various 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 hr. The pure water flux was measured at 345 kPa pressure and is determined largely by the composition of polyethersulfone and additive concentration. The flux was found to reach the highest values of 66.5 and 275 1/(cm² hr) at 0 and 10 wt% additive concentrations respectively, at 25% SPS content of the blend. Membrane hydraulic resistance derived by measuring water flux at various transmembrane pressure and by using an algorithm was 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 20–69 kDa (globular proteins) depending on the PEG and SPS content in the casting dope. Skin surface porosity of the membranes were analyzed by scanning the frozen membrane samples using scanning electron microscopy (SEM) at different magnifications. The surface porosity is in direct correlation to the MWCO derived from solute retention experiments. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of preparation variables on morphology and pure water permeation flux through asymmetric cellulose acetate membranes

In this study, cellulose acetate (CA) ultrafiltration (UF) membranes were prepared using the phase inversion method. Effects of CA and polyethylene glycol (PEG) concentrations in the casting solution and coagulation bath temperature (CBT) on morphology of the synthesized membranes were investigated. Based on L₉ orthogonal array of Taguchi experimental design 18 membranes were synthesized (with two replications) and pure water permeation flux through them were measured. It was found out that increasing PEG concentration in the casting solution and CBT, accelerate diffusional exchange rate of solvent 1-methyl-2-pyrrolidone (NMP) and nonsolvent (water) and consequently facilitate formation of macrovoids in the membrane structure. Increasing CA concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. Rate of water flux through the synthesized membranes is directly dependent on the size and number of macrovoids in the membrane structure. Thus, maximum value of flux is obtained at the highest levels of PEG concentration and CBT (10 wt.% and 23 °C, respectively) and the lowest level of CA concentration (13.5 wt.%). Analysis of variance (ANOVA) showed that all parameters have significant effects on the response. However, CBT is the less influential factor than CA and PEG concentrations on the response (flux).     

Polyurethane and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization studies

Polyurethane (ether type) and sulfonated polysulfone (sodium salt form) in the presence of polyethylene glycol 600 were blended in various compositions using N,N'-dimethylformamide as solvent and used for preparing ultrafiltration membranes by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were optimized. Blend membranes were subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and membrane resistance. The membranes were also subjected to the determination of pore statistics and molecular weight cutoff determination studies using dextran of different molecular weights. Surface morphology of the membranes was analyzed using scanning electron microscopy at different magnifications. The effects of polymer composition and additive concentration on the above parameters were analyzed and the results are compared and discussed with those of pure sulfonated polysulfone membranes. The derived pore size, porosity, and number of pores have a remarkable interrelationship and also have a definite role and relationship with the molecular weight cutoff, morphology, and flux performance of the membranes.     

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone were prepared by phase inversion technique. ATRP grafting of tert-butylacrylate from chloromethylated polysulfone was used for the grafted polymer synthesis. The copolymer was characterized with FTIR, NMR, DSC and TGA. The prepared membranes were characterized in terms of pure water flux, water contact angle, cut off molecular weight, salt rejection and scanning electron microscopy.     

Studies on cellulose acetate-polysulfone ultrafiltration membranes: II. Effect of additive concentration

Polymeric blend ultrafiltration membranes based on cellulose acetate and polysulfone were prepared by phase inversion technique in presence of different additive concentrations, polyvinylpyrrolidone, and characterized in terms of compaction time, pure water flux (PWF), water content, membrane resistance and scanning electron microscopy (SEM). The blend membranes were subjected to separation of proteins and heavy metal ions using polyethylenimine as a complexing agent and the results were discussed. The molecular weight cut off of blend membranes was also reported.     

Two‐stage phase separation of cellulose acetate membranes modified with plasma‐treated natural zeolite: Response surface modeling

Cellulose acetate (CA) microfiltration membranes were prepared by two‐stage vapor‐induced phase separation (VIPS) and immersion precipitation. To improve the hydrophilicity and permeability of the membranes at low operating pressures, plasma‐treated natural zeolite was incorporated into the membranes. A response surface methodology based on the three‐level central composite design (CCD) was used to model and optimize the casting solution composition of the membranes with the aim of maximizing membranes permeability. Three independent variables for CCD optimization were concentration of CA, polyvinylpyrrolidone (PVP) pore former, and plasma‐treated zeolite additive. The results showed that a second‐order polynomial model could properly predict the response (pure water flux) at any input variable values with a satisfying determination coefficient (R²) of 0.954. Also, analysis of variance (ANOVA) confirmed the adequacy of the obtained model. The permeability of the prepared membranes increased by increasing zeolite loading from 0.10 to 0.50 wt%, which was related to the membranes morphology and porosity and confirmed by scanning electron microscopy (SEM) images. Pure water flux of the membranes decreased by increasing CA concentration while an optimum PVP amount was required to reach the maximum flux. The result of the bubble point analysis well matched with surface SEM images of the membranes and permeability trend predicted by CCD model. Also, the prepared CA membranes with different compositions showed no toxicity for mouse L929 fibroblast, which indicated their nontoxic and biocompatible nature.     

Cellulose acetate blends with acrylonitrile/N-phenyl maleimide copolymers morphological and thermal properties

Cellulose acetate (CA) was blended in different compositions with various acrylonitrile-N-halo phenyl maleimide (AN-XPhM) copolymers to improve the thermal and mechanical properties of cellulose acetate. The structure, morphology, thermal stability, and crystallinity of the blend films were characterized by infrared spectroscopy, scanning electron micrographs, thermogravimetry/differential thermal analysis, differential scanning calorimetry, and X-ray diffraction. The results revealed that the thermal stability was improved by the increase in AN-XPhM content, irrespective of the type of the N-halo phenyl maleimide. The CA/AN-4BrPhM blend films possessed the highest thermal stability compared to the other CA/AN-XPhM blend films. Blending CA with AN-4BrPhM yielded the most homogeneous blend films, irrespective of the composition ratio. The mechanical properties of various compositions of the CA/AN-4BrPhM blend films were also discussed.     

Novel nanocomposite membranes from cellulose acetate and clay‐silica nanowires

In this study, a new class of heterogeneous membranes based on cellulose acetate (CA) polymer and a complex filler clay‐silica nanowires (SiO₂NWs) was investigated for potential biomedical applications. SiO₂NWs were synthesized using natural clay through a facile sol–gel method and were dispersed in the polymer solution by sonication in the 1.25, 2.5, and 5% weight ratio to the CA acetate polymer. Membranes were subsequently prepared via phase inversion by precipitation of the CA polymer in water. The pristine CA membrane and SiO₂NWs based nanocomposites membranes were characterized using different characterization techniques. The presence of the SiO₂NWs in the CA membrane was found to significantly enhance the protein retention, water wettability and thermal as well as mechanical properties in comparison to the pristine CA membrane. Water flows studies at different temperatures and the retention of bovine serum albumin have been studied and the nanocomposite membranes were found to exhibit superior performances compared with the pristine CA membranes. SiO₂NWs‐CA membranes showed a much higher stability to the water temperature change during separation than CA membranes. Morphological changes clearly revealed that the composite membrane were much more compact than the pristine CA membranes. The rabbit dermal fibroblasts cell viability in cultures after 72 hr of incubation was found to be greater than 80%. These newly synthesized composite membranes exhibit a high potential to be used for various medical applications because of their non‐cytotoxic characteristics. Copyright © 2016 John Wiley & Sons, Ltd.     

Study on preparation and performances of cellulose acetate forward osmosis membrane

Cellulose acetate (CA) forward osmosis (FO) membranes were prepared via a phase inversion process. CA was used as membrane material for FO. Acetone and 1,4-dioxane were employed as solvent. Polyvinylpyrrolidone (PVP), maleic acid, and methanol were applied as additives. An orthogonal experiment was performed to optimize the ratio of every component in the casting solution. The membrane with best performance was selected to concentrate an anthocyanin solution. Saturated sucrose solution (about 60°Brix) was fit for using as draw solution in the concentration experiment. Water flux, porosity, and rejection rate were measured to evaluate the membrane properties. Reverse water rinsing was used in cleaning membrane that was fouled by anthocyanin solution. Results showed that under membrane thickness of 100 μm, coagulation temperature at room temperature, and evaporation time of 30 s, the optimum components in casting solution were 13% CA, 45% 1,4-dioxane, 31% acetone, 2% maleic acid, 3% PVP, and 6% methanol. In the concentration experiment, the prepared FO membrane showed water flux of 2.04 L m^?2 h^?1 and rejection rate of 98.61%. In the membrane cleaning experiment, the water flux of the FO membrane recovered 87.51% after rinsing for 1 h. The prepared membranes and previously published membranes were compared which showed the prepared membrane could significantly improve the rejection rate for anthocyanin solution.     

Polymeric membranes based on cellulose acetate loaded with candle soot nanoparticles for water desalination

This study is concerned with modifying cellulose acetate (CA)/polyethylene glycol (PEG) membranes prepared via phase inversion technique in the presence of carbon nanoparticles; candle soot (CS) resulting from combusted candle. CS nanoparticles were analyzed via Fourier transform infrared spectroscopy and transmission electron microscopy. The developed membranes were characterized for their surface morphology, mechanical properties as well as thermal stability. CS nanoparticles contributed in improving the salt rejection % with a slight reduction in the water flux behavior. Employing the annealed cellulose acetate/polyethylene glycol membranes loaded with candle soot nanoparticles provides an adequate approach towards water desalination implementations.     

Development of an enantioselective membrane from cellulose acetate propionate/cellulose acetate,for the separation of trans-stilbene oxide

This paper reports the characterization of new synthesized chiral polymeric membranes, based on a cellulose acetate propionate polymer. The flux and permselective properties of the membrane were studied using 50 % ethanol solution of (R,S)-trans-stilbene oxide as feed solution. Scanning electron microscopy revealed the asymmetric structure of these membranes. The roughness of the surface was measured by atomic force microscopy. The resolution of over 97 % enantiomeric excess was achieved when the enantioselective membrane was prepared with 18 wt% cellulose acetate and 8 wt% cellulose acetate propionate in the casting solution of dimethyl formamide/N-methyl-2-pyrrolidone/acetone, at 20 °C and 55 % humidity, and a water bath at 10 °C for the gelation of the membrane. The operating pressure and the feed concentration of the trans-stilbene oxide were 275.57, 345.19, and 413.84 kPa and 2.6 mM, respectively.     

Synthesis, characterization and thermal studies on cellulose acetate membranes with additive

Cellulose acetate (CA) membranes are used in ultrafiltration applications, although they show low chemical, mechanical and thermal resistance. In order to prepare membranes with improved properties, modification of cellulose acetate with polyethelene glycol (PEG 600) has been attempted. In this study, CA has been mixed with PEG 600 as an additive in a polar solvent. The effects of CA composition and additive concentration given by a mixture design of experiments on membrane compaction, pure water flux, water content and membrane hydraulic resistance have been studied and discussed. The efficiency of protein separation by the developed CA membranes have been quantified using model proteins such as pepsin, egg albumin (EA) and bovine serum albumin (BSA). The thermal stability of the developed membranes prepared with PEG 600 additive has also been investigated using thermogravimetric analysis and differential scanning calorimetry.     

Cellulose acetate and polyetherimide blend ultrafiltration membranes: II. Effect of additive

Ultrafiltration membranes are largely applied in the separation of heavy metal ion and macromolecular solutes from aqueous streams. Studies are presented on ultrafiltration blend membranes, based on cellulose acetate (CA) and polyetherimide (PEI) in various blend compositions. Polyethylene glycol (PEG 600) was employed as a non‐solvent additive in various concentrations to the casting solution to improve the ultrafiltration performance of the resulting membranes. The blend membranes prepared were characterized in terms of compaction time, pure water flux (PWF), water content, membrane resistance, and scanning electron microscopy (SEM). The molecular weight cut‐off (MWCO) obtained from the protein separation studies is also reported. Applications of these membranes for separating toxic metal ions from aqueous streams are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

PEU/PES共混膜的制备工艺条件研究

利用L-S相转化法将聚醚型聚氨酯（PEU）和聚醚砜（PES）共混,以聚乙二醇（PEG）为添加剂,制备PEU/PES共混膜,并通过测定比较共混膜的结构与性能.结果表明：聚合物浓度、共混组成比、添加剂种类与浓度是影响PEU/PES共混膜性能的主要因素.     

Effect of polyethyleneglycol (PEG) on gas permeabilities and permselectivities in its cellulose acetate (CA) blend membranes

The effect of polyethyleneglycol (PEG) on gas permeabilities and selectivities was investigated in a series of miscible cellulose acetate (CA) blend membranes. The permeabilities of CO₂, H₂, O₂, CH₄, N₂ were measured at temperatures from 30 to 80°C and pressures from 20 to 76 cmHg using a manometric permeation apparatus. It was determined that the blend membrane having 10 wt% PEG20000 exhibited higher permeability for CO₂ and higher permselectivity for CO₂ over N₂ and CH₄ than those of the membranes which contained 10% PEG of the molecular weight in the range 200–6000. The CA blend containing 60 wt% PEG20000 showed that its permeability coefficients of CO₂ and ideal separation factors for CO₂ over N₂ reached above 2 × 10⁻⁸ [cm³ (STP) cm/cm² s cmHg] and 22, respectively, at 70°C and 20 cmHg. Based on the data of gas permeability coefficients, time lags and characterization of the membranes, it is proposed that the apparent solubility coefficients of all CA and PEG blend membranes for CO₂ were lower than those of the CA membrane. However, almost all the blend membranes containing PEG20000 showed higher apparent diffusivity coefficients for CO₂, resulting in higher permeability coefficients of CO₂ with relation to those of the CA membrane. It is attributed to the high diffusivity selectivities of CA and PEG20000 blend membranes that their ideal separation factors for CO₂ over N₂ were higher than those of the CA membrane in the range 50–80°C, even though the ideal separation factors of almost all PEG blend membranes for CO₂ over CH₄ became lower than those of the CA membrane over nearly the full range from 30° to 80°C.     

Effect of PEG additive on membrane formation by phase inversion

This study investigates the effect of PEG additive as a pore-former on the structure formation of membranes and their permeation properties connected with the changes of thermodynamic and kinetic properties in phase inversion process. The membranes were prepared by using polysulfone (PSf)/N-methyl-2-pyrrolidone (NMP)/poly(ethylene glycol) (PEG) casting solution and water coagulant. The resulting membranes prepared by changing the molecular weight of PEG additive and the ratio of PEG to NMP were characterized by scanning electron microscope observations, measurements of water flux and PEG rejection. The thermodynamic and kinetic properties of membrane-forming system were studied through coagulation value, light transmittance and viscosity. The correlations between the final membrane structure/permeation properties and thermodynamic/kinetic properties of membrane forming system are discussed extensively.