Effects of polyaniline nanoparticles in polyethersulfone ultrafiltration membranes: Fouling behaviours by different types of foulant

Polyethersulfone (PES) was modified by blending it with polyaniline (PANI) nanoparticles to improve the membrane performance. Three types of membranes: PES (controlled sample), PES-PANI self-synthesised, and PES-PANI (commercial), were evaluated by direct interaction with BSA, humic acid, silica nanoparticles, Escherichia coli and Bacillus bacteria. The surface hydrophilicity of the modified PES membranes was enhanced by the addition of PANI nanoparticles and showed improved fouling resistance and a high flux recovery ratio as well as improvement in BSA and humic acid rejection even with higher pore sizes. The modified membrane also showed less attack from the bacteria, demonstrating improved biofouling activity.     

Improving the hydrophilicity of polyethersulfone membrane by the combination of grafting technology and reverse thermally induced phase separation method

In this work, surface grafting modification technology was combined with reverse thermally induced phase separation (RTIPS) method in order to improve the structure and permanent hydrophilicity of polyethersulfone (PES) membranes. Acrylic solution with different concentrations was grafted on the surface of PES membranes while grafting temperature and grafting time were also varied. The modified PES membranes were characterized in all aspects. Attenuated total reflectance Fourier transform-infrared confirmed successful modification of the PES membrane by grafting acrylic acid. Scanning electron microscopy revealed that homogeneous porous top surface as well as spongy-like cross-section structure appeared in the membrane by RTIPS procedure. Moreover, porosity was affected by changes of acrylic acid concentration, grafting temperature, and grafting time. Atomic force microscopy showed that grafting acrylic acid gave a reduction in roughness of PES membrane. Combined with the decreased values of contact angle, the hydrophilicity and antifouling performance of the PES membrane were improved. The pure water flux and BSA rejection rate of the grafted PES membranes were remarkably improved for pure PES membrane and attained a maximum, which was 1,646.24 L/(m²h) and 94.5%, respectively. The long-term test demonstrated that grafting membranes exhibited outstanding elevated water flux recovery ratio (>85%).     

Structural and performance properties of UV-assisted TiO2 deposited nano-composite PVDF/SPES membranes

In this research, the surface of poly (vinylidene fluoride) (PVDF)/sulfonated polyethersulfone (SPES) blend membrane prepared via immersion precipitation was modified by depositing of TiO₂ nano-particles followed by UV irradiation to activate their photocatalytic property. The membranes were characterized by FTIR, SEM, AFM, contact angle, dead end filtration (pure water flux and BSA solution flux), antifouling analysis and antibacterial activity. The FTIR spectrum confirmed the presence of OH functional groups on the PVDF/SPES membrane structure, which was the key factor for deposition, and self-assembly of TiO₂ nanoparticles on the membrane surface. The SEM and AFM images indicated that the TiO₂ nanoparticles were deposited on the PVDF/SPES membrane. The contact angle measurements showed that the hydrophilicity of PVDF/SPES membrane was strongly improved by TiO₂ deposition and UV irradiation. The filtration results indicated that the initial flux of TiO₂ deposited PVDF/SPES membranes was lower than the initial flux of neat PVDF/SPES membrane. However, the former membranes showed lower flux decline compared to the neat PVDF/SPES membrane. The BSA rejection of modified membranes was improved. The fouling analysis demonstrated that the TiO₂ deposited PVDF/SPES membranes showed the fewer tendencies to fouling. The results of antibacterial study showed that the UV irradiated TiO₂ deposited PVDF/SPES membranes possess high antibacterial property.     

Peroxopolyoxometalate nanoparticles blended PES membrane with improved hydrophilicity,anti-fouling,permeability, and dye separation properties

Poly(ethersulfone) (PES) is one of the polymers most widely used for the fabrication of ultrafiltration or nanofiltration membranes in various applications, but its membrane suffers from fouling. In this study, preparation, characterization, and performance of PES nanocomposite membrane comprising peroxopolyoxometalate nanoparticles was studied to provide improved permeability and anti-fouling properties. The high oxygen ratio of the PW₄ nanoparticles could enhance the hydrophilicity of the membranes. The PW₄ nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction analyses. The mixed matrix membranes were fabricated using a non-solvent induced phase-separation method. The fabricated membranes were characterized using atomic force microscopy, attenuated total reflection, SEM, EDX mapping, total average porosity, thermogravimetric analyze, and water contact angle experiments. The dye flux and rejection, pure water permeability and anti-fouling properties of the membranes were investigated. All of the membranes blended by different contents of the PW₄ nanoparticles presented better performance compared to the unmodified membrane. The filtration performance of the membranes in reactive green 19 (RG19) and reactive yellow 160 (RY160) dye separation showed that all of the PW₄ blended membranes possessed dye rejection greater than 86% and 96% for RY160 and RG19, respectively. The reusability test using bovine serum albumin (BSA) protein and RG19 dye solutions in five cycle experiments presented good reproductivity of the PW₄ blended membranes. The PES membrane containing 1 wt% of PW₄ nanoparticles showed the highest flux recovery ratio (75%) as well as reduced irreversible fouling ratio (8%) through BSA protein filtration.     

Synthesis of a novel sulfonated poly(amide‐imide) and its application in preparation of ultrafiltration PES membranes as a modifier

Sulfonated poly(amide‐imide) (SPAI) copolymer was synthesized, characterized, and blended into poly(ether sulfone) (PES)/dimethylacetamide casting solutions to prepare ultrafiltration membranes. Different weight ratios of the copolymer (0–10 wt %) were mixed in the PES casting solution. The analyses of contact angle and attenuated total reflection‐Fourier transform infrared spectra were used to study hydrophilicity and physicochemical properties of the membrane surface, respectively. The membranes were further characterized by scanning electron microscopy images, ultrafiltration performance, and fouling analyses. The outcomes showed that addition of the SPAI in the PES matrix improved considerably the membranes hydrophilicity. Moreover, with increasing SPAI concentration, the porosity, flux recovery ratio, and pure water permeability of the modified membranes were improved. The pure water flux was increased from 3.6 to 12.4 kg/m² h by increasing 2 wt % SPAI. The antifouling property of the modified PES membranes against bovine serum albumin, tested by a dead‐end filtration setup revealed that bovine serum albumin rejection of the obtained membrane was also enhanced and the antifouling properties of the blending membranes were improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46477.     

Effect of silver loaded sodium zirconium phosphate (nanoAgZ) nanoparticles incorporation on PES membrane performance

Polyethersulfone (PES) based ultrafiltration membranes were fabricated via phase inversion by adding silver-loaded sodium zirconium phosphate nanoparticles (nanoAgZ) in PES casting solutions. The effect of nanoAgZ concentration on the membrane performance, i.e., morphology, hydrophilicity, thermal stability, permeation and antifouling properties was investigated. The results of thermal gravitational analysis (TGA) showed that the thermal stability of the hybrid membrane had been improved by the addition of nanoAgZ particles. Contact angle results indicated that the hydrophilicity of the modified membranes was enhanced. The contact angle of the membrane decreased from 71.5° to 52.6° with the increase of the nanoparticle content in the casting solution. Permeation experiment results showed that the modified PES membranes demonstrate better separation performance over the pure PES membrane. The pure water flux of PES membrane increased from 82.1 L/m² h to 100.6 L/m² h with the addition of the nanoparticles. Most importantly, the incorporation of the nanoAgZ particles enhanced the BSA fouling resistance and also the anti-biofouling performance of the membrane.     

Preparation and characterization of asymmetric polyethersulfone nanofiltration membranes: The effects of polyvinylpyrrolidone molecular weights and concentrations

In this study, asymmetric flat‐sheet polyethersulfone (PES) nanofiltration (NF) membranes were prepared via immersion precipitation phase inversion with the addition of polyvinylpyrrolidone (PVP). The effects of PVP with the molecular weights (MW) from 17 to 1400 kDa and the concentration from 0 to 3.0 wt % on the morphologies and performances of PES membranes were systematically studied. The prepared membranes were characterized by SEM, AFM, ATR‐FTIR, contact angle, membrane porosity, the water flux, and the rejection measurement. The results indicated that the porosity and the hydrophilicity of PES NF membrane increased with increasing PVP concentration, and the hydrophilicity of PES NF membrane also improved with increasing PVP MW. The enhancements of the porosity and hydrophilicity resulted in the higher water flux of PES NF membrane. The rejection of Bordeaux S (MW 604.48 Da) for the prepared PES membrane was increased to above 90% with the low PVP concentration, but it turned to decrease remarkably when the PVP concentration reached to a critical value which related to PVP MW. It was concluded that the addition of a small amount of PVP could significantly increase the permeability of PES NF membrane and maintain its rejection of Bordeaux S above 90%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43769.     

Surface modification of poly(ether sulfone) ultrafiltration membranes by low‐temperature plasma‐induced graft polymerization

Low‐temperature helium plasma treatment followed by grafting of N‐vinyl‐2‐pyrrolidone (NVP) onto poly(ether sulfone) (PES) ultrafiltration (UF) membranes was used to modify commercial PES membranes. Helium plasma treatment alone and post‐NVP grafting substantially increased the surface hydrophilicity compared with the unmodified virgin PES membranes. The degree of modification was adjusted by plasma treatment time and polymerization conditions (temperature, NVP concentration, and graft density). The NVP‐grafted PES surfaces were characterized by Fourier transform infrared attenuated total reflection spectroscopy and electron spectroscopy for chemical analysis. Plasma treatment roughened the membrane as measured by atomic‐force microscopy. Also, using a filtration protocol to simulate protein fouling and cleaning potential, the surface modified membranes were notably less susceptible to BSA fouling than the virgin PES membrane or a commercial low‐protein binding PES membrane. In addition, the modified membranes were easier to clean and required little caustic to recover permeation flux. The absolute and relative permeation flux values were quite similar for the plasma‐treated and NVP‐grafted membranes and notably higher than the virgin membrane. The main difference being the expected long‐term instability of the plasma treated as compared with the NVP‐grafted membranes. These results provide a foundation for using low‐temperature plasma‐induced grafting on PES with a variety of other molecules, including other hydrophilic monomers besides NVP, charged or hydrophobic molecules, binding domains, and biologically active molecules such as enzymes and ribozymes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1699–1711, 1999     

Flux,antifouling and separation characteristics enhancement of nanocomposite polyethersulfone mixed-matrix membrane by embedding synthesized hydrophilic adipate ferroxane nanoparticles

Polyethersulfone (PES) nanofiltration (NF) membranes were prepared by blending of synthesized hydrophilic adipate ferroxane nanoparticles (AFNPs) as a novel multifunctional nanofiller via the phase inversion method. The water contact angle measurement indicated the higher hydrophilicity of the NF membranes. The water flux of the membranes improved significantly after the addition of AFNPs, from 10.4 to 32.2 kg/m²h. Antifouling characteristics of AFNPs/PES membranes were improved by increased hydrophilicity and decreased membrane surface roughness. The 0.6 wt% AFNPs/PES membrane exhibited the highest FRR (96%) and the lowest irreversible fouling resistance (6%). The nanofiltration performance of the prepared membranes was evaluated by dye removal and salt retention. The results proved the high dye removal capability of modified membranes (98% rejection) compared with the unfilled PES membrane (89% rejection). The salt retention sequence for membrane with 0.2 wt% of nanoparticles was Na₂SO₄ (70%)>MgSO₄ (60%)>NaCl (18%).     

Effects of coagulation bath temperature and polyvinylpyrrolidone content on flat sheet asymmetric polyethersulfone membranes

In this study, effects of coagulation bath temperature (CBT) and polyvinylpyrrolidone (PVP K15) concentration as a pore former hydrophilic additive on morphology and performance of asymmetric polyethersulfone (PES) membranes were investigated. The membranes were prepared from a PES/ethanol/NMP system via phase inversion induced by immersion precipitation in a water coagulation bath. The morphology of prepared membranes was studied by scanning electron microscopy (SEM), contact angle measurements, and mechanical property measurements. Permeation performance of the prepared membranes was studied by separation experiments using pure water and bovine serum albumin (BSA) solution as feed. The obtained results indicate that addition of PVP in the casting solution enhances pure water permeation flux and BSA solution permeation flux while reducing protein rejection. Increasing CBT results in macrovoid formation in the membrane structure and increases the membrane permeability and decreases the protein rejection. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Synthesis,characterization and application of antioxidants nanoparticles incorporated polymeric membranes

Aim of this work is to establish industrial application of antioxidant nanoparticles incorporated polyethersulfone (PES) and polyethyleneterephthalate (PET) membranes. PES and PET blended ultrafiltration (UF) membranes were subjected to surface modification with antioxidant 2,2?-methylenebis(6-tert-butyl-4-ethylphenol) (MBEP) nanoparticles incorporation, as well as modification with antioxidant 2,2?-ethylidenebis (4,6-di-tert-butylphenol) (EBBP) nanoparticles, further, with combination of MBEP/EBBP nanoparticles. Hydrophilicity, stability and anti-fouling of modified membranes were investigated. The modified membranes exhibited much better chemical stability to acid- and alkali solutions, improved the hydrophilicity and water flux. PES/MBEP:EBBP copolymer membranes exhibited excellent fouling tolerance against oily water than normal antioxidant materials.     

Concentration of gelatin solution with polyethersulfone ultrafiltration membranes

In this work, polyethersulfone (PES) flat sheet ultrafiltration (UF) membranes were prepared by immersion precipitation phase inversion process with polyvinylpyrrolidone (PVP 30K) and acetone as additives. The best preparation condition for PES membranes with high water flux and rejection (to BSA) was decided. It was found that the optimal composition of the polymer casting solution was: 16 wt% (PES), 2 wt% (PVP 30K), and 1 wt% (acetone). Pure water flux of the membrane prepared at this condition reached to 373 L/m² h at 0.1 MPa, and the rejection to BSA was 91%. Compared with other reports, the rejection was slightly low but the flux of the PES membrane was high. When the membrane was used to concentrate gelatin solutions, the rejection value was over 75%. It was found that increasing the feed temperature and transmembrane pressure enhanced the permeation flux, but the rejection decreased slightly. However, increasing the cross-flow velocity of the feed solution simultaneously increased both the permeation flux and the rejection.     

Effects of coagulation bath temperature on performances of polyethersulfone membranes modified by nanosilver particles in situ reduction

In this work, an in situ reduction method was used to prepare nanosilver‐modified polyethersulfone (PES‐Ag) ultrafiltration membranes by mixing up the reducing agent ethylene glycol and the protective agent polyvinylpyrrolidone to reduce AgNO₃ in the casting solution. The effects of coagulation bath temperature (CBT) on the separation performances, antifouling property, tensile strength, and stability of the nanosilver particles were researched. The results indicated that when the PES‐Ag membranes were prepared in 40°C coagulation bath, the loss rate of nanosilver particles during preparation was minimum, only 18.5%. With the CBT increasing from 20 to 60°C, the water flux of the PES and PES‐Ag membranes increased, whereas the rejection rate decreased. The largest flux reached 471 L·m^?2·h^?1 for PES‐Ag membranes prepared at 60°C and the rejection was over 90%. The results of contact angle and flux recovery ratio showed that PES‐Ag membranes had better hydrophilicity and antifouling property. Furthermore, the PES‐Ag membranes could inhibit Escherichia coli from growing. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

The effect of polymer surface modification via interfacial polymerization on polymer–protein interaction

Membrane separation is an important processing technology used for separating food ingredients and fractionating value‐added components from food processing byproducts. Long‐term performance of polymeric membranes in food protein processing is impeded by the formation of fouled layers on the membrane surface as a result of protein adsorption onto the membrane surface. Surface modification of synthetic membranes, i.e., changing surface characteristics to reduce protein adsorption permanently, is one of the innovative ways of reducing the fouling of membrane surfaces. In this study, surface modification of flat‐sheet ultrafiltration membrane, polyethersulfone (PES), was investigated in improving the hydrophilicity of PES surfaces, thereby reducing adsorption of the protein caused by hydrophobic–hydrophobic interaction between the protein and the membrane. Hydrophilic polymer grafting through thin‐film composite using interfacial polymerization was employed to improve the hydrophilicity of the commercial PES membranes. Poly(vinyl alcohol), poly(ethylene glycol), and chitosan were chosen as hydrophilic polymers to graft on PES membrane because of their excellent hydrophilic property. Modified PES membranes were characterized by contact angle, FTIR, XPS, and AFM. Contact angles of modified PES membranes were reduced by 25 to 40% of that of the virgin PES membrane. XPS spectrum supported that the PES membranes were successfully modified by interfacial polymerization. Tapping‐mode AFM was used to examine the changes in surface topography of modified PES membranes. The PES membranes modified by interfacial polymerization showed lower roughness (from 1.2 to 2.0 nm) than that of virgin PES membrane (2.1 nm). The results of these instrumental analyses indicated that the PES membranes were successfully enhanced hydrophilically through interfacial polymerization. The protein adsorption on the modified membranes was reduced by 30 to 35% as a result of surface modification of the PES membranes using interfacial polymerization technique. Published 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

PAN ultrafiltration membranes grafted with natural amino acids for improving antifouling property

In this report, antifouling polyacrylonitrile (PAN) ultrafiltration membranes were prepared from blends of PAN/polyglycidyl methacrylate (PGMA) via phase inversion method followed by the grafting of natural amino acids through epoxy ring-opening reaction. The grafted PAN membranes possessed highly stable hydrophilic surfaces as a result of the grafting of amino acids, which was adequately demonstrated in attenuated total reflectance–Fourier transform infrared spectroscopy (ATR/FTIR), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of tensile strength and scanning electron microscopy (SEM) images further proved that the surface modification had little effect on their mechanical properties, surface, and cross-sectional morphologies. Meanwhile, remarkable resistance against bovine serum albumin (BSA) and lysozyme (Lyz) fouling was observed for the neutral amino acid-based PAN membranes due to the formation of zwitterionic hydration layer on the membrane surface, while PAN membranes grafted with charged amino acids were able to prohibit the approach of like charged proteins with reduced deposition and provide the driving force for oppositely charged protein adsorption. Furthermore, the ultrafiltration and antifouling performance of PAN membranes were investigated by BSA filtration experiments. Compared with the pristine PAN membrane, all the modified PAN membranes exhibited higher pure water flux, better flux recovery ratio, lower rejection, less total permeation resistance, and preferable stability, having potential applications in protein separation and purification.     

Fabrication of novel polyethersulfone based nanofiltration membrane by embedding polyaniline-co-graphene oxide nanoplates

Mixed matrix polyethersulfone (PES) based nanofiltration membrane was prepared through phase inversion method by using of polyvinylpyrrolidone (PVP) as pore former and N, N dimethylacetamide (DMAc) as solvent. Polyaniline-co-graphene oxide nanoplates (PANI/GO) were utilized as additive in membrane fabrication. The PANI/GO nanoplates were prepared by polymerization of aniline in the presence of graphene oxide nanoplates. FTIR analysis, scanning electron microscopy (SEM), scanning optical microscopy (SOM), 3D images surface analysis, water contact angle, water content tests, tensile strength tests, porosity tests, salt rejection and flux tests were used in membrane characterization. FT-IR results verified formation of PANI on graphene oxide nanoplates. SOM images showed uniform particles distribution for the mixed matrix membranes. SEM images also showed formation of wide pores for the modified membranes. Water flux showed constant trend nearly by use of PANI/GO in the casting solution. Opposite trend was found for the membrane surface hydrophilicity. Salt rejection was enhanced sharply by utilizing of PANI/GO. The membrane’s tensile strength was improved by increase of PANI/GO concentration. The water content was increased initially by use of PANI/GO nanoplates up to 0.05%wt into the casting solution and then decreased. Membrane porosity was also enhanced by using of PANI/GO nanoplates. Modified membrane containing 0.5%wt PANI/GO nanoplates showed more appropriate antifouling characteristic compared to others.     

Chemical modification of polyethersulfone nanofiltration membranes: A review

Polysulfone (PS) and poly(ether)sulfone (PES) are often used for synthesis of nanofiltration membranes, due to their chemical, thermal, and mechanical stability. The disadvantage for applying PS/PES is their high hydrophobicity, which increases membrane fouling. To optimize the performance of PS/PES nanofiltration membranes, membranes can be modified. An increase in membrane hydrophilicity is a good method to improve membrane performance. This article reviews chemical (and physicochemical) modification methods applied to increase the hydrophilicity of PS/PES nanofiltration membranes. Modification of poly(ether)sulfone membranes in view of increasing hydrophilicity can be carried out in several ways. Physical or chemical membrane modification processes after formation of the membrane create more hydrophilic surfaces. Such modification processes are (1) graft polymerization that chemically attaches hydrophilic monomers to the membrane surface; (2) plasma treatment, that introduces different functional groups to the membrane surface; and (3) physical preadsorption of hydrophilic components to the membrane surface. Surfactant modification, self‐assembly of hydrophilic nanoparticles and membrane nitrification are also such membrane modification processes. Another approach is based on modification of polymers before membrane formation. This bulk modification implies the modification of membrane materials before membrane synthesis of the incorporation of hydrophilic additives in the membrane matrix during membrane synthesis. Sulfonation, carboxylation, and nitration are such techniques. To conclude, polymer blending also results in membranes with improved surface characteristics. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Self-doped sulfonated polyaniline ultrafiltration membranes with enhanced chlorine resistance and antifouling properties

Membranes heavily rely on chlorination to diminish (bio)fouling, but chlorination can also lead to membrane degradation. We developed sulfonated polyaniline (S-PANI) ultrafiltration (UF) membranes with improved chlorine resistance and intrinsic antifouling properties. The S-PANI membranes were synthesized through Non-solvent Induced Phase Separation (NIPS). Membrane performance was evaluated under harsh chlorine conditions (250 ppm sodium hypochlorite for 3 days under different pH conditions). The S-PANI membranes showed improved chlorine resistance including a stable performance without changes in model foulant BSA rejection. In contrast, PANI membranes suffered critical structural damage with complete leakage and commercial PES membranes showed a 76% increase in pure water flux and a noticeable change in BSA rejection. Small changes in S-PANI membrane performance could be linked to membrane structural changes with pH, as confirmed by SEM, IR spectroscopy, and contact angle measurements. Additionally, the S-PANI membranes showed better antifouling properties with a high flux recovery ratio in comparison to PANI membranes using alginic acid, humic acid, and BSA model foulants. Chemical cleaning by sodium hypochlorite re-instated the transport properties to its initial condition. Overall, the developed S-PANI membranes have a high chlorine tolerance and enhanced antifouling properties making them promising for a range of UF membrane applications.     

Investigation on the effect of spinning conditions on the properties of hollow fiber membrane for hemodialysis application

Polyethersulfone (PES) hollow fiber membranes were fabricated via the dry‐wet phase inversion spinning technique, aiming to produce an asymmetric, micro porous ultrafiltration hollow‐fiber specifically for hemodialysis membrane. The objective of this study is to investigate the effect of spinning conditions on the morphological and permeation properties of the fabricated membrane. Among the parameters that were studied in this work are air gap distance, dope extrusion rate, bore fluid flow rate, and the take‐up speed. The contact angle was measured to determine the hydrophilicity of the fibers. Membrane with sufficient hydrophilicity properties is desired for hemodialysis application to avoid fouling and increase its biocompatibility. The influences of the hollow fiber's morphology (i.e., diameter and wall thickness) on the performance of the membranes were evaluated by pure water flux and BSA rejection. The experimental results showed that the dope extrusion rate to bore fluid flow rate ratio should be maintained at 1:1 ratio to produce a perfectly rounded asymmetric hollow fiber membrane. Moreover, the flux of the hollow fiber spun at higher air gap distance had better flux than the one spun at lower air gap distance. Furthermore, spinning asymmetric hollow fiber membranes at high air gap distance helps to produce a thin and porous skin layer, leading to a better flux but a relatively low percentage of rejection for BSA separation. Findings from this study would serve as primary data which will be a useful guide for fabricating a high performance hemodialysis hollow fiber membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43633.     

Surface modification and preparation of nanofiltration membrane from polyethersulfone/polyimide blend—Use of a new material (polyethyleneglycol‐triazine)

Blends of polyethersulfone/polyimide (PES/PI) were prepared by dissolving in dimethylformamide/dioxane (DMF/DO) to manufacture nanofiltration membranes by using polyvinylpirrolidone (PVP) as a pore former. The membrane modification was carried out by adding ethylenediamine (EDA) to open the imide group ring of PI and by using polyethyleneglycol (PEG)‐triazine, as a new modifier material, that was produced in the laboratory. This modification involves the formation of a covalence ‐C‐N‐ bound between PEG‐triazine and amine groups (according to addition‐elimination reactions) at different temperatures. After functionalizing the membranes, diethanolamine (DA) was utilized as a hydrophilic modifier to change the membranes properties. SEM, AFM, FTIR‐ATR, EDS (X‐ray analysis) and contact angle tests were carried out to characterize modified membranes. The hydrophilicity of PES/PI membranes was improved by modification. An increase in pure water flux (up to 195 kg/m² h) and a decline in NaCl rejection (from 25 to 16%) are largely influenced by diminishing the PES/PI ratio in L₁‐L₅ membranes (Category 1). In L₆, L₇, and L₈ membranes (Category 2), by introducing PEG‐triazine into the membrane recipe, salt rejection increased from 75 to 80%. Addition of DA further enhances the salt rejection up to 93%. Fluxes were approximately similar for membranes in Category 2. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009