Ultrafiltration Support Membrane Research Articles

Synergistic preparation of organic solvent nanofiltration membranes from polydopamine/polyethyleneimine interlayers with aminated attapulgite

This study utilized polydopamine (PDA)/polyethyleneimine(PEI) as the hydrophilic interlayer and added aminated attapulgite (ATP-NH2) to the aqueous phase monomer for interfacial polymerization (IP) to synergistically create nanofiltration membranes resistant to organic solvents. The hydrophilic nature of the PDA/PEI interlayer facilitates the rapid passage of polar solvents and results in excellent adhesion, ensuring tight bonding between the ultrafiltration support membranes and the active layer. Furthermore, the incorporation of the ATP-NH2 nanoparticles played a pivotal role in regulating the IP process. The resulting nanofiltration membranes, produced through the combined efforts of these components, achieved an optimal methanol permeation flux of 14.05 L m−2h−1 bar−1, with a rejection rate of Evans blue dye maintained at 99.42 %. Despite being exposed to N, N-dimethylformamide (DMF) at 80 ℃ for a period of 5 days, the nanofiltration membranes maintained both their exceptional separation effectiveness and stability. These findings suggest promising application prospects for the developed nanofiltration membranes.

Removal of arsenic from water using a novel polyamide composite hollow fiber membrane by interfacial polymerization on lumen side

A novel mixed polyamide based composite membrane was prepared by interfacial polymerization (IP) of chitosan (CS) and m-phenylenediamine (MPD) mixture with trimesoyl chloride (TMC) for low pressure hollow fiber nanofiltration (NF). A uniform thin selective layer of polyamide was chemically coated on the lumen side of the polysulfone (PSF) based ultrafiltration support membrane. Permeability of the prepared hollow fiber NF membrane improved appreciably by incorporation of a small amount of CS into the MPD solution during IP process. The properties of prepared hollow fiber membranes were characterized using scanning electron microscope (SEM), contact angle, molecular weight cut off (MWCO), permeability, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and surface zeta potential. Pure water permeability of mixed polyamide composite membrane enhanced from 3.8 l/m2h bar to 32.5 l/m2h bar, which corroborated an increase in MWCO from 673 Da to 2553 Da and pore radius from 6.8 to 12.9 Å as CS was incorporated in polyamide layer. However, this drastic increase in permeate flux was not compromised with the arsenate rejection, which changed from 74.68% to 73.16% only. Thus, the prepared hollow fiber membrane performance was suitable and competent for low pressure driven hollow fiber membrane based arsenate rejection, which has many advantages over the conventional resin based filtration to remove arsenic from water. Performance of the developed hollow fiber membrane was also tested with arsenic contaminated natural groundwater prepared artificially with a rejection of 66–71% arsenate, 45–47% total dissolved solids (TDS), 47–48% hardness and 46–50% iron at 1 bar pressure with 25 l/m2h permeate flux.

식물성 기름/용매 분리를 위한 Polyaniline-Polyimide 박막 복합 Membrane의 합성과 특성 분석

The recovery of solvents from the extracted oils using conventional thermal separation processes i.e. distillation or evaporation is often an energy-intensive process. To provide an energy-efficient alternative, an organic solvent nanofiltration thin-film composite membrane was prepared by depositing a thin layer of polyaniline (PANI), a selective layer, via interfacial polymerization on a crosslinked polyimide (XPI), a base ultrafiltration support membrane, to provide selective transport of constituents of a miscella. The membrane was characterized by microscopic, spectroscopic, and thermal analysis. The evaluation of the separation performance was carried out by a dead-end stirred cell using three vegetable oils. For sunflower, corn, and castor oil/n-hexane mixtures, the membrane resulted in a % rejection of 50, 56, and -44, respectively. A comparison of mass flux and rejection of corn and castor oils suggests that the PANI/XPI membranes showed a strong ion-exchange behavior significantly recognizing charge macromolecules due to the presence of charged emeraldine PANI.

Development of high flux nanofiltration membranes through single bilayer polyethyleneimine/alginate deposition

The aim of this study is to prepare high flux, stable, antifouling nanofiltration membranes through single bilayer polyelectrolyte deposition. To this end, a tight ultrafiltration support membrane was prepared from a polysulfone/sulfonated polyethersulfone blend. Deposition of a polyethyleneimine and alginate pair on this support has reduced the molecular weight cut off from 6 kDa to below 1 kDa. The pure water permeability and polyethylene glycol 1000 rejection of the coated membrane were found to be 15.5 ± 0.3 L/m2·h·bar and 90 ± 0.6%, respectively, by setting the deposition pH for each layer to 8 and the ionic strengths to 0.5 M and 0 M. This membrane has exhibited significantly higher permeability than commercial membranes with the same molecular weight cut off, retaining 98% of the initial flux during 15 h filtration of bovine serum albumine. In addition, the membrane has been able to completely remove anionic dyes from aqueous solution by showing 99.9% retentions to Reactive red 141, Brilliant blue G and Congo red with a 2 bar transmembrane pressure. High flux and membrane stability in acidic and salty environments have been achieved when deposition conditions favor high adsorption levels for the first layer and strong ionic cross-linking between the carboxyl group on the alginate and the amine groups on the polyethyleneimine.

Hollow fiber nanofiltration membranes with integrated aquaporin Z

AqpZ reconstituted proteoliposomes integrated into polyamide matrix using different ultrafiltration support membranes successfully with a performance increase of 12 times.

Polyelectrolyte complexes/silica hybrid hollow fiber membrane for fusel oils pervaporation dehydration processes

Pervaporation as a tool to remove the residual water in biological resources, such as fusel oils (by-product of alcohol fermentation), is gaining increasing importance and consist with sustainable development well. In this study, polyelectrolyte complexes/silica (PEC/SiO2) hybrid hollow fiber membranes were prepared in situ via sol-gel process on polysulfone ultrafiltration support membrane. γ-glycidyloxypropyltrimethoxysilane (GPTMS) was introduced as precursor and crosslinker into poly (diallyldimethylammonium chloride)–sodium carboxymethyl cellulose complexes to form SiO2 particles in situ and enhance the interaction between inorganic and organic components. The physicochemical properties and morphology of the membranes were characterized by FT-IR, FESEM, EDS, etc. PEC/SiO2 membrane (PECM/SiO2) achieved an enhanced flux compared with the PEC pristine membrane without GPTMS. The membranes possessed a flux of 1332g/m2h and water content in permeate of 99.0wt% for the dehydration of fusel oils at 60°C. The effects of feed temperature and water content in feed on pervaporation performance were also investigated. Furthermore, the performance of PECM/SiO2 for the batch continuous dehydration application of fusel oils was more efficient than PERVAP-1001 commercial membranes. This approach provided a convenient way to prepare PEC/SiO2 hybrid hollow fiber membranes, which were potentially applied in fusel oils pervaporation dehydration processes.

Preparation and characterization of a PVA/PSf thin film composite membrane after incorporation of PSSMA into a selective layer and its application for pharmaceutical removal

Abstract A thin film composite (TFC) membrane was synthesized by coating a layer of poly (vinyl alcohol) (PVA) cross-linked with Glutaraldehyde on a polysulfone (PSf) ultrafiltration support membrane. The effect of the incorporation of polyelectrolyte poly (4-styrenesulfonic acid-co-maleic acid) (PSSMA) into the PVA matrix at concentrations of 0% to 3% was investigated. The TFC membranes were characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-IR) spectroscopy, contact angle and zeta potential measurements. The rejection rates were measured for Na2SO4, MgSO4 and NaCl salts and cephalexin, amoxicillin, ibuprofen and povidone iodine (PVP-I) pharmaceuticals. The effect of molecular weight and size, hydrophobicity, and electrical charge of the pharmaceuticals on the rejection of the TFC membranes was also investigated. It was found that incorporation of PSSMA into the PVA layer could increase membrane pure water flux (PWF). The results revealed that the addition of 1% PSSMA (TFC1) increased PWF from 6.8 to 14 l/m2 h and showed comparable rejection rates for all membranes. For this sample, rejections of 99%, 97.7%, 93.8% and 74% were obtained for cephalexin, amoxicillin, PVP-I and ibuprofen, respectively. The effects of pH, transmembrane pressure and feed concentration on pharmaceutical separation performance were also studied. The rejection of ibuprofen increased from 74.1% to 97.2% after an increase in pH from 7 to 9. Near 100% rejection for cephalexin and amoxicillin and 80% for ibuprofen at a 20 ppm feed concentration showed the ability of the membrane for efficient pharmaceutical removal at low concentrations. An increase in transmembrane pressure increased the rejection of ibuprofen and PVP-I. For cephalexin and amoxicillin, a plateau occurred in the range of 97–99%.

Preparation of acid-resistant PEI/SA composite membranes for the pervaporation dehydration of ethanol at low pH

Abstract Pervaporation is an efficient process for recovering bioethanol produced from biomass fermentation, which often contains ethanol, water, and a variety of acids compounds. However, it is still a major challenge to fabricate pervaporation membranes with good acid resistance capability and high separation performance. In order to separate ethanol/water mixtures consisted of inorganic or organic acid over a range of pH environments, we prepared polyelectrolyte multilayer membranes via ionic cross-linking between polyethyleneimine (PEI) and sodium alginate (SA). In this study, PEI and SA were alternatively deposited on ultrafiltration support membrane by using dynamic layer-by-layer (LbL) technique. The ionic cross-linking between the COO− groups of SA and –NH2 groups of PEI has been demonstrated using FTIR. It was found that the multilayer membranes showed high pervaporation performance in acid conditions. The water content could be enriched from 10 wt% to 99.42 wt% (β = 1542) and the permeate flux was 1.203 kg/(m2 h) in the dehydration of ethanol/water mixture with pH = 3 at 60 °C. Long time operations showed that water content in permeate fluctuated above 99.3 wt%, and permeation flux stayed stable around 0.88 kg/(m2 h), which indicated that (SA/PEI)1.5/PAN membrane has promising potential for dehydration of acid feed.

Modification of polyamide thin-film composite membranes with amino-cyclodextrins and diethylamino-cyclodextrins for water desalination

This paper discusses the modification of polyamide thin-film composite (TFC) membranes with amino- and diethylamino-cyclodextrins (CDs). An in situ modification procedure was carried out using different concentrations of amino and diethylamino functionalised CDs (both α- and β-CDs) dispersed in m-phenylenediamine in water. These aqueous solutions were then reacted with trimesoyl chloride on polyethersulphone (PES) ultrafiltration support membranes through the interfacial polymerisation process. Contact-angle measurements demonstrate that the TFC membranes have improved hydrophilic properties due to additional OH functional groups of the CDs. The incorporation of the amino- and diethylamino-CDs within the membrane selective layer improved water permeability which was rationalised by the increased hydrophilicity and additional water channels in the modified membranes. Modified membranes exhibited significantly improved water permeability (33.92±2.00lm−2h−1) and maintained a high NaCl rejection (99.21%±0.65%). The unmodified membranes, however, had a flux of 1.12±0.5lm−2h−1 and a NaCl rejection of 95.69%±0.87%, at 6.89bar. Membranes modified with diethylamino-CDs had a smoother surface while the unmodified membranes and membranes modified with amino-CDs had rough surfaces. The membranes modified with diethylamino-CDs had a compact and dense cross-linked polyamide thin-film structure while membranes modified with amino-CDs had a less compact cross-linked structure. This is due to the CC chain of the diethylamino functionality that allowed for a maximum exposure of the pendent group to the trimesoyl chloride during the interfacial polymerisation; as a result, the diethylamino-CDs were less subjected to steric hindrance than the amino-CDs. The pendent group of the amino-CDs was close to the molecule, making it difficult to reach during the interfacial polymerisation due to steric hindrance.

Preparation and properties of novel sulfonated copoly (phthalazinone biphenyl ether sulfone) composite nanofiltration membrane

Thin composite nanofiltration membranes with improved thermal stability were prepared by coating sulfonated copoly (phthalazinone biphenyl ether sulfone) (SPPBES) on poly (phthalazinone ether sulfone ketone) ultrafiltration support membranes. The effects of polymer concentration, degree of sulfonation of SPPBES, crosslinking agent, curing treatment temperature and curing time on the performance of composite membranes were investigated. The membrane prepared under the optimum condition exhibited a permeate flux of 73L/m2h and 84% rejection of Na2SO4 at 1.0MPa and 20°C. Moreover, these membranes showed good stability against chemical attack and high tolerance to chlorine. When the temperature of feed solution increased from 20 to 90°C, solution permeate flux increased three-fold while the rejection of the membrane decreased by 2%.

Membranes for Organic Solvent Nanofiltration Based on Preassembled Nanoparticles

A new class of organic solvent nanofiltration (OSN) membranes has been fabricated by assembling nanosized polymer particles with methacrylate moieties onto the surface of cross-linked polyimide ultrafiltration support membranes. Multiple layers of these nanoparticles create a separation film functionally similar to the top layer of an asymmetric OSN membrane. Nanoscale interstitial spaces formed between the particles serve as permeation channels. In principle, manipulating the size of the nanoparticles can be used to control the dimensions of the interstitial spaces through which permeation occurs. Two different sizes of nanoparticles, 120 nm and 300 nm, were used. As expected, membrane separation performance changed with the size of nanoparticles employed because of the changes in interstitial dimensions. Cross-linked polyimide ultrafiltration membranes prepared by phase inversion were coated with successive layers of nanoparticles by spin coating. After coating the nanoparticles were cross-linked by pho...

Layer-by-layer assembled nanohybrid multilayer membranes for pervaporation dehydration of acetone–water mixtures

Abstract In this article, an organic–inorganic nanohybrid multilayer membranes have been developed by incorporating zirconium dioxide (ZrO 2 ) and alumina oxide (Al 2 O 3 ) nanoparticles into polyelectrolyte complexes such as poly(diallyldimethyl ammonium chloride)/poly(sodium styrene sulfonate) and poly(ethyleneimine)/polyacrylic acid. These nanohybrid multilayers were successfully formed on to both flat sheets and hollow fiber polyacrylonitrile ultrafiltration support membranes by layer-by-layer (LbL) assembly of polycation- and polyanion-coated nanoparticles and used for pervaporation dehydration of an acetone–water mixture. We show that the matching between the size of the NPs and the supporting membrane pore size strongly influences the morphologies and performance of the multilayer membranes. SEM-EDX and AFM analyses suggest that the ZrO 2 NPs are mostly distributed on the substrate surface while the Al 2 O 3 NPs are able to migrate into the substrate membrane pores. This is due to the differences between the sizes of the two NPs and results in an increase of the surface roughness of the ZrO 2 nanohybrid multilayer membrane while that of the Al 2 O 3 nanohybrid multilayer membrane decreased. The ZrO 2 nanohybrid multilayer membrane was able to overcome the trade-off phenomenon, which enabled both higher flux and larger separation factor. However, for the Al 2 O 3 nanohybrid multilayer membrane, the separation factor increased while the corresponding flux values were somewhat lower than those observed for pristine polymeric membranes.

Tuning the molecular structure, separation performance and interfacial properties of poly(vinyl alcohol)–polysulfone interfacial composite membranes

Interfacial composite membranes were prepared by dip-coating poly(vinyl alcohol) hydrogels on polysulfone ultrafiltration support membranes. Ultra-thin poly(vinyl alcohol) films were cast using multi-step coating procedure with dilute poly(vinyl alcohol) aqueous solutions and stabilized by a novel in situ cross-linking technique using five different cross-linking agents. A previously developed film casting technique allowed a constant film thickness of 200–300nm to be maintained while varying cross-linking degree and cross-linking agent. The effects of crosslinking on the molecular structure, separation performance, and interfacial properties of poly(vinyl alcohol)–polysulfone composite membranes were probed experimentally and with molecular dynamic simulations. Higher degrees of cross-linking correlated strongly with lower PVA film crystallinity and decreased hydrophilicity. Experimentally determined solvent and solute permeability data correlated almost perfectly with molecular dynamics simulated fractional free volumes of the cross-linked poly(vinyl alcohol) membranes, demonstrating the importance of polymer free volume (i.e., steric exclusion and hindered diffusion) in solvent and solute transport through nanofiltration membranes and suggesting that predictive, in silico design of cross-linked PVA coating films may be practical.

Transport, structural, and interfacial properties of poly(vinyl alcohol)–polysulfone composite nanofiltration membranes

Composite nanofiltration membranes were prepared by coating poly(vinyl alcohol) hydrogels on polysulfone ultrafiltration support membranes. Ultra-thin and defect-free poly(vinyl alcohol) hydrogels were cast using multi-step coating procedure with dilute PVA aqueous solutions and novel in situ cross-linking. The combined Spiegler–Kedem–film theory model was used to extract water permeability, solute permeability, reflection coefficients, and mass transfer coefficients for the composite membranes. Transport of water and salt ions through PVA coating films was dramatically influenced by feed solution pH and counter-ion valence as well as PVA molecular weight, concentration, and extent of cross-linking. Characterization of PVA coating film thickness, extent of cross-linking, surface thermodynamic properties, and crystallinity were used to explain differences in observed transport properties of the composite membranes.

High flux composite PTMSP-silica nanohybrid membranes for the pervaporation of ethanol/water mixtures

Silica-filled poly(1-trimethylsilyl-1-propyne) (PTMSP) layers were successfully applied for the first time on top of ultrafiltration support membranes and applied in the pervaporative separation of ethanol/water mixtures. Reduction of the thickness of the separating PTMSP top layer and addition of hydrophobic silica particles resulted in a clear flux increase as compared to dense PTMSP membranes. With ethanol/water separation factors up to 12 and fluxes up to 3.5 kg m −2 h −1, the prepared supported PTMSP-silica nanohybrid membranes performed significantly better than the best commercially available organophilic pervaporation membranes. Characterization of a polyvinylidene fluoride (PVDF) and a polyacrylonitrile (PAN) support membrane revealed a more open, irregular and hydrophobic surface structure for the former membrane, thus explaining the higher fluxes of the PTMSP/PVDF composite membrane. Because of their promising flux-selectivity combination, the prepared membranes exhibit great potential in the removal of alcohols from aqueous mixtures.

Nanofiltration membranes based on poly(vinylidene fluoride‐co‐chlorotrifluoroethylene)‐graft‐poly(styrene sulfonic acid)

AbstractGraft copolymers comprising poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) backbone and poly(styrene sulfonic acid) side chains, i.e. P(VDF‐co‐CTFE)‐g‐PSSA were synthesized using atom transfer radical polymerization (ATRP) for composite nanofiltration (NF) membranes. Direct initiation of the secondary chlorinated site of CTFE units facilitates grafting of PSSA, as revealed by FT‐IR spectroscopy. The successful “grafting from” method and the microphase‐separated structure of the graft copolymer were confirmed by transmission electron microscopy (TEM). Wide angle X‐ray scattering (WAXS) also showed the decrease in the crystallinity of P(VDF‐co‐CTFE) upon graft copolymerization. Composite NF membranes were prepared from P(VDF‐co‐CTFE)‐g‐PSSA as a top layer coated onto P(VDF‐co‐CTFE) ultrafiltration support membrane. Both the rejections and the flux of composite membranes increased with increasing PSSA concentration due to the increase in SO3H groups and membrane hydrophilicity, as supported by contact angle measurement. The rejections of NF membranes containing 47 wt% of PSSA were 83% for Na2SO4 and 28% for NaCl, and the solution flux were 18 and 32 L/m2 hr, respectively, at 0.3 MPa pressure. Copyright © 2008 John Wiley & Sons, Ltd.

Preparation of polyelectrolyte multilayer membranes by dynamic layer-by-layer process for pervaporation separation of alcohol/water mixtures

In the past decades, the layer-by-layer (LBL) adsorption of oppositely charged polyelectrolytes has proven to be a promising method for the preparation of polyelectrolyte multilayer membranes. However, to obtain a good separation capability, LBL adsorption involved relatively long periods because 50–60 bilayers were normally required. The aim of this study was to develop such a new method that would allow simplification of the LBL procedure. LBL adsorption was proposed to proceed under a dynamic condition to prepare polyelectrolyte multilayer membranes. The polyacrylic acid (PAA) and polyethyleneimine (PEI) were alternatively deposited on polyethersulfone (PES) ultrafiltration support membrane under a pressure of 0.1 MPa. The polyelectrolyte multilayer membranes prepared by dynamic LBL process were compared with those prepared by the static LBL process for the pervaporation separation of water–ethanol mixture. The results suggested that a relatively high separation factor could be obtained with only four composite bilayers by using dynamic LBL process. The preparative conditions including bilayer number, filtration time of the first PAA layer, reaction time, ratio between polayanion and polycation concentrations, PAA molecular weight and salt addition were investigated. The pervaporation conditions such as feed temperature and water concentration in the feed were also evaluated. Under the temperature of 40 °C, the separation factor and the permeate flux of the polyelectrolyte multilayer membranes were about 1207 and 140 g/(m 2 h), respectively.

Characteristics and performance of new types of ultrafiltration membranes with chemically modified surfaces

A special “quo;coating”quo; technique for making new types of surface modified ultrafiltration membranes has been developed and evaluated. The preparation procedure comprises the following principle: A suitable ultrafiltration support membrane made by the traditional phase inversion process is surface coated with an aqueous solution containing a hydrophilic polymer and/or monomer having reactive groups and a catalyst (the coating step). The membrane material is selected from the class of fluorine containing polymers. By raising the temperature, the hydrophilic components are chemically bonded to the membrane material at the exposed surface by an addition reaction (the curing step). Using this method you can impart hydrophilic properties to an otherwise hydrophobic, high resistant synthetic polymeric ultrafiltration membrane. The properties of the final membrane depend on the characteristics of the support membranes, the composition of the coating solution and the amount applied and the reaction conditions. The technique seems more or less universal - e.g. it is possible to make a series of membranes with different cut-off values. Results from measurements on different test solutions and on relevant industrial products are described. Characterization is done by measuring hydraulic permeability and rejection of dextrans and proteins. Flux stability and fouling tendency have been examined using different model foulants. Membrane surface structures are characterized by SEM-studies. Analytical investigations using infrared spectroscopy (FTIR/ATR) and X-ray photoelectron spectroscopy (ESCA) have been tried to get some information about the chemistry of the coating. The main advantages of the new membranes are that higher flux values compared to a standard polyethersulfone UF membrane are generally obtained - e.g. on whey flux improvements in the order for 20 – 50% have been observed and for fermentation broths fluxes can be several times greater compared to results using the standard membrane. Some of these new membranes are now commercially available and are supplied by DDS FILTRATION, designated ETNA series.