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.     

Cellulose acetate and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization

Modification of polymeric membrane materials by incorporation of hydrophilicity results in membranes with low fouling behavior and high flux. Hence, Polysulfone was functionalized by sulfonation and ultrafiltration membranes were prepared based on sulfonated polysulfone and cellulose acetate in various blend compositions. Polyethyleneglycol 600 was employed as a nonsolvent additive in various concentrations to the casting solution to improve the ultrafiltration performance of the resulting membranes. The total polymer concentration, cellulose acetate, and sulfonated polysulfone polymer blend composition, additive concentration, and its compatibility with polymer blends were optimized. The membranes prepared were characterized in terms of compaction, pure water flux, membrane resistance, and water content. The compaction takes place within 3–4 h for all the membranes. The pure water flux is determined largely by the composition of sulfonated polysulfone and concentration of additive. Membrane resistance is inversely proportional to pure water flux, and water content is proportional to pure water flux for all the membranes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1749–1761, 2002     

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 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.     

Performance characterization of cellulose acetate and poly(vinylpyrrolidone) blend membranes

Hydrophilic ultrafiltration membranes have been prepared by blending cellulose acetate (CA) as a matrix polymer with increasing concentrations of poly(vinylpyrrolidone) (PVP) using N,N′‐dimethylformamide as the solvent. It is observed that the presence of PVP beyond 50 wt % in the casting solution did not form membranes. Prepared membranes have been subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and membrane hydraulic resistance. The results indicate significant changes in the characteristics upon the addition of PVP, which may lead to improved performance. The porosity, pore size, and molecular weight cut‐off of the membranes also increase as the concentration of PVP increases. It is estimated that the pore radius of the CA/PVP membranes increases from 30 to 63 Å, when the concentration of PVP increased from 0 to 50 wt %. This is in agreement with the results obtained from scanning electron microscopic studies. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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.     

Effects of PEG on Morphology and Permeation Properties of Polyethersulfone Membranes

Abstract

Flat sheet asymmetric polyethersulfone (PES) ultrafiltration (UF) membranes were prepared from a homogenous solution of PES via immersion precipitation in a water coagulation bath. The effect of the solvents (N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF)) in preparation of the casting solution was studied. The effects of the molecular weight of polyethylene glycol (PEG) (400, 1500, and 6000 Da) on the morphology and the permeation properties of PES membranes were also investigated. Surface and cross-sectional morphology of the prepared membranes were studied by Scanning electron microscopy (SEM). The permeation performance of the prepared membranes was evaluated in terms of pure water flux (J_w), water content, porosity, hydraulic permeability, protein solution flux, and protein rejection. A solution of human serum albumin (HSA, Mw = 66,000 Da) was used as feed to study the permeation properties of the prepared membranes. Increasing molecular weight of PEG additives from 400 to 6000 Da enhances pure water permeation flux and HSA solution permeation flux while it reduces the protein rejection.     

Studies on cellulose acetate‐carboxylated polysulfone blend ultrafiltration membranes. III

Enhancement of the hydrophilicity in polymeric membrane materials results in membranes with higher flux and better membrane characteristics. Hence, polysulfone was carboxylated and ultrafiltration membranes were prepared from blends of cellulose acetate and carboxylated polysulfones having various degrees of carboxylation with a total polymer concentration of 20 wt % in casting solution and at different blend polymer compositions. The effects of degree of carboxylation on membrane characteristics such as compaction, pure water flux, and membrane hydraulic resistance (R_m) have been investigated. The influence of the polymer concentration in the blend solution on the performance of blend membranes at various blend polymer compositions has also been investigated and compared with that of blend membranes prepared from blends of cellulose acetate and polysulfone or carboxylated polysulfone with a total polymer concentration of 17.5 wt %. Further, the solute rejection performance of the membranes has also been investigated by subjecting the membranes to metal ion permeation studies using polyelectrolyte‐enhanced ultrafiltration. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 976–988, 2005     

Preparation of high‐flux ultrafiltration membranes by blending strongly charged polymer

Three kinds of high‐flux ultrafiltration membranes were fabricated by blending strongly charged polymer [sulfonated poly(phenylene oxide) (SPPO)] with neutral polymer [cellulose acetate (CA), polyethersulfone (PES), or polyvinylidene fluoride (PVDF)]. After blending with SPPO, the pure water flux of CA‐SPPO, PES‐SPPO, and PVDF‐SPPO membrane increase by 3, 76, and 30 times at a transmembrane pressure of 100 kPa. Compared with the unblended membranes, the pore radius of CA‐SPPO, PES‐SPPO, and PVDF‐SPPO membrane increased from 31.9 to 33.2 nm, 26.1 to 28.6 nm, and 19.8 to 25.7 nm, respectively. The addition of strongly charged polymer decreased the thermodynamic stability of casting solutions, promoting the phase inversion process and resulting in highly porous structure. The charged groups and hydrophilicity of the polymer facilitate the formation of an additive concentration gradient (more additive in the active layer), endowing the blend membrane with better hydrophilicity and greater wettability gradient. The high porosity, good hydrophilicity, and larger wettability gradient enable the high permeation of blend membranes. This work shows how the strongly charged polymer affects the formation and performance of blend membrane, which will be useful for designing high‐performance membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44570.     

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 characterization of PVDF-PFSA flat sheet ultrafiltration membranes

High performance polyvinylidene fluoride (PVDF) flat sheet ultrafiltration (UF) membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid (PFSA) as a pore former and as a hydrophilic component of the membranes and polyethylene glycol (M_w = 400) (PEG400) as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin (BSA) protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane (5 wt-% PEG400+ 5 wt-% PFSA) had a pure water flux of 141.7 L/m²·h, a BSA rejection of 90.1% and a relative pure water flux reduction (RFR) of 15.28%. These properties were greatly superior to those of the native PVDF membrane (pure water flux of 5.6 L/m²·h, BSA rejection of 96.3% and RFR of 42.86%).     

Performances of poly(vinylidene fluoride‐co‐hexafluoropropylene) ultrafiltration membranes modified with poly(vinyl pyrrolidone)

The structure and performance of modified poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐co‐HFP) ultra‐filtration membranes prepared from casting solutions with different concentrations of poly(vinyl pyrrolidone) (PVP) were investigated in this study. Membrane properties were studied in terms of membrane compaction, pure water flux (PWF), water content (WC), membrane hydraulic resistance ( R _m), protein rejection, molecular weight cut‐off (MWCO), average pore size, and porosity. PWF, WC, and thermal stability of the blend membranes increased whereas the crystalline nature and mechanical strength of the blend membranes decreased when PVP additive concentration was increased. The contact angle (CA) decreased as the PVP concentration increased in the casting solution, which indicates that the hydro‐philicity of the surface increased upon addition of PVP. The average pore size and porosity of the PVdF‐co‐HFP membrane increased to 42.82 Å and 25.12%, respectively, when 7.5 wt% PVP was blended in the casting solution. The MWCO increased from 20 to 45 kDa with an increase in PVP concentration from 0 to 7.5 wt%. The protein separation study revealed that the rejection increased as the protein molecular weight increased. The PVdF‐co‐HFP/PVP blended membrane prepared from a 7.5 wt% PVP solution had a maximum flux recovery ratio of 74.3%, which explains its better antifouling properties as compared to the neat PVdF‐co‐HFP membrane. POLYM. ENG. SCI., 55:2482–2492, 2015. © 2015 Society of Plastics Engineers     

Preparation,characterization and performance of cellulose acetate ultrafiltration membranes modified by charged surface modifying macromolecule

A charged surface modifying macromolecule (cSMM) was synthesized, characterized by FT-IR spectroscopy and blended into the casting solution of cellulose acetate (CA) to prepare surface modified UF membranes by phase inversion technique. With an increasing cSMM additive content from 1 to 4 wt%, pure water flux (PWF) and water content (WC) were increases whereas the hydraulic resistance decreases. Surface characteristic study reveals that the surface hydrophilicity increased in cSMM modified CA membranes. The pore size and surface porosity of the 4 wt% cSMM blend CA membranes increases to 41.26 Å and 0.015%, respectively. Similarly, the molecular weight cut-off (MWCO) of the membranes ranged from 20 to 45 kDa, depending on the various compositions of the prepared membranes. Lower flux decline rate (47.2%) and higher flux recovery ratio (FRR) (89.0%), exhibited by 4 wt% cSMM blend membranes demonstrated its fouling resistant characteristic compared to pristine CA membrane.     

Effect of Isomeric Propanols on the Performances of Polyethersulfone Nanofiltration Membranes

Abstract

In this work, polyethersulfone (PES) asymmetric nanofiltration (NF) membranes were prepared by immersion precipitation phase inversion process. The casting solution contained N-methyl-2-pyrrolidone (NMP) as solvent, 1-propanol and 2-propanol as nonsolvent additives, and polyvinylpyrrolidone (PVP) as pore former additive. Water was used as a coagulant. The effects of the PVP content in the casting solution and the exposed time on the performances of the NF membranes were investigated. It was found that with the increase of PVP content, the pure water flux (PWF) increased to the largest value and then decreased. The rejection to PEG 1000 always decreased. The largest value (1281.40 kg · m^?2 · h^?1 · MPa^?1) of PWF appeared when the content of 1-propanol was 9 wt.%. However, when 2-propanol was added in the casting solution, the largest value of PWF was only 678.37 kg · m^?2 · h^?1 · MPa^?1 (the content of 2-propanol was 7 wt.% and other preparing conditions were unchanged). The results meant that both PWF and rejection of the membranes with 1-propanol as additive were higher than that of 2-propanol as additive. The possible reason was discussed from the viewpoint of the difference of solubility of propanols to PES and PVP.     

Preparation and characterization of composite membranes of polysulfone and microcrystalline cellulose

Physical and chemical modifications of polymeric ultrafiltration membranes are necessary to improve their hydrophilic properties, strength, and other characteristics. Microcrystalline cellulose (MCC) was prepared from cellulose pulp by acid‐catalyzed hydrolysis in the presence of ultrasonic radiation, and the properties of MCC were evaluated. Through the addition of MCC to a polysulfone (PS) membrane solution, a casting solution of a PS/MCC blend was obtained. Subsequently, the ultrafiltration membrane from the blend was further developed in a phase‐inversion process comprising immersion and deposition. The capacity for ultrafiltration was better with increasing MCC content. When the ratio of MCC to PS was 0.3, the pure water flux of the composite membrane reached 234.2 L/m²/h, and the retention of a bovine serum albumin solution (1 g/L) was as high as 93.4%. The membranes were also observed with scanning electron microscopy and atomic force microscopy to study their microstructures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and performance of sulfonated polysulfone flat ultrafiltration membranes

Sulfonated polysulfone (SPSF) flat ultrafiltration membranes were successfully prepared by immersion precipitation phase inversion method. N‐Methyl pyrrolidone was used as a solvent, and polyvinylpyrrolidone (PVP) was used as a polymeric additive in the casting solution. The effects of casting solution formulation and preparation conditions on membrane structure and properties were investigated in present study, and the morphology of the membranes was analyzed by scanning electron microscopy. The results indicated that the performances of SPSF membranes made by chemical modification were better than polysulfone membrane. The SPSF concentration played a vital role in restricting the pure water flux (PWF), promoting the rejection coefficient, and improving the hydrophilicity. A maximum PWF and minimum egg albumin rejection coefficient were obtained when the PVP content was 10%. When the coagulation bath temperature was set to 25°C, the PWF reached 480 L·m^?2·h^?1 and the ovalbumin rejection coefficient reached 92%. Longer evaporation times improved the PWF. Specifically, when the evaporation time was 70 s, the comprehensive performance was good. POLYM. ENG. SCI., 55:1003–1011, 2015. © 2014 Society of Plastics Engineers     

Cellulose acetate ultrafiltration membranes reinforced by cellulose nanocrystals: Preparation and characterization

Cellulose nanocrystals (CNCs) were used as a sustainable additive to improve the hydrophilicity, permeability, antifouling, and mechanical properties of blend membranes. Different CNC loadings (0–1.2 wt %) in cellulose acetate (CA) membranes were studied. The blend membranes were prepared by a phase‐inversion process, and their chemical structure and morphological properties were characterized by attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy, porosity, and mean pore size and contact angle measurement. The blend membranes became more porous and more interconnected after the addition of CNCs. The thickness of the top layer decreased and a few large holes in the porous substrate appeared with increasing CNC loading. In comparison with the pure CA membranes, the pure water flux of the blend membranes increased with increasing CNC loading. It reaches a maximum value of 76 L m^?2 h^?1 when the CNC loading was 0.5 wt %. The antifouling properties of the CA membrane were significantly improved after the addition of CNCs, and the flux recovery ratio value increased to 68% with the addition of 0.5 wt % CNCs. In comparison with that of the pure CA membranes, the tensile strength of the composite membranes increased by 47%. This study demonstrated the importance of using sustainable CNCs to achieve great improvements in the physical and chemical performance of CA ultrafiltration membranes and provided an efficient method for preparing high‐performance membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43946.     

Preparation of hydrophilic polysulfone membrane using polyacrylic acid with polyvinyl pyrrolidone

This study examined the consequences of the addition of polyvinyl pyrrolidone (PVP) of different molecular weights with constant molecular weight of polyacrylic acid (PAA) on the morphology and permeation properties of polysulfone (PSF) membranes. The asymmetric polymeric membranes were prepared by phase inversion process using PSF in N‐methyl‐2‐pyrrolidone (NMP) as a solvent. The surface structure and morphology of the prepared membranes were analyzed by field‐emission scanning electron microscope (FESEM) and atomic force microscopy (AFM). The pore number, average pore size and area of pores for all the membranes were determined by permeability method. These ultrafiltration membranes were subjected to characterizations such as measurement of pure water flux (PWF), compaction factor (CF), bovine serum albumin (BSA) rejection for finding the permeability performance, whereas equilibrium water content, contact angle, porosity, hydraulic resistance, and ion exchange capacity (IEC) are measured for evaluating the hydrophilicity. Results demonstrate that the flux performance of the membranes and morphological parameters own a crucial inter‐relationship with the molecular weight of PVP. The membrane pore area and pore number were found to be increased by increasing molecular weight of PVP with constant molecular weight of PAA. A detailed comparative study was done with Chakrabarty et al. (J. Membr. Sci. 2008, 309, 209) and found better in almost all the aspects. All the resulting parameters were compared and concluded with the fact that addition of small amount of PAA in PSF/PVP/NMP casting solution can be better than addition of PVP alone. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41964.     

Cellulose acetate–poly(ether sulfone) blend ultrafiltration membranes. II. Application studies

Ultrafiltration membranes are largely applied as macromolecular solutes and heavy‐metal‐ion separation from aqueous streams. Cellulose acetate and poly(ether sulfone) blend ultrafiltration membranes were prepared by the precipitation phase‐inversion technique in 100/0, 95/5, 85/15, and 75/25% polymer blend compositions in the absence and presence of a polymeric additive, poly(ethylene glycol) 600, at different additive concentrations and were used for the rejection of proteins trypsin, pepsin, egg albumin, and bovine serum albumin; a maximum of 94% rejection was achieved. The toxic heavy metal ions copper, nickel, and cadmium from dilute aqueous solutions were subjected to rejection by the blend membranes by complexation of the ions with the water‐soluble polymeric ligand, polyethyleneimine (PEI). Permeate flux studies of proteins and metal ions were performed simultaneously with the rejection experiments. The atomic absorption spectra results reveal maximum rejection for copper complex and a minimum rejection of about 60% for the cadmium complex. The rejection and permeate flux of the blend membranes were compared with those of pure cellulose acetate membranes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3659–3665, 2004