Enhanced Surface Hydrophilicity Research Articles

Thin film nanocomposite hollow fiber membranes incorporated with surface functionalized HKUST-1 for highly-efficient reverses osmosis desalination process

A new class of thin film nanocomposite (TFN) hollow fiber (HF) membrane of polydopamine (PDA) modified HKUST-1 (mHKUST-1) incorporated in polyamide (PA) matrix supported by polyethersulfone (PES) substrate was constructed via interfacial polymerization method for brackish water desalination in low-pressure reverse osmosis (RO) process. The PDA modification facilitated the HKUST-1 even dispersion, thus resulting in better compatibility between the inorganic nanofillers and the organic matrix. The impact of HKUST-1 loadings on the overall performances of the resultant HKUST-1@PA/PES membranes was investigated. Introducing the mHKUST-1 nanofillers not only enhanced surface hydrophilicity and negative surface charges for the selective layer, which improved membrane's fouling resistance to humic acid (HA), but also led to nearly doubled water permeance when comparing with the pristine PA membrane (increasing from 3.51 to 6.94 Lm−2h-1bar−1), without obvious salt rejection deterioration (~98.2% at 2 bar and 97.4% rejections at 4 bar for 500/2000 ppm NaCl solutions, respectively). The integrity of the HKUST-1@PA/PES membrane was examined and verified after 30-days operation. Overall, the results achieved in this work demonstrate promising potential of the metal organic framework (MOF)-based TFN membranes used for desalination in low-pressure RO process. To sum up, this work has exhibited a facile method to incorporate the metal organic framework (MOF) into the PA layer, and the resultant MOF-based TFN membrane indicates its great potential for desalination in low-pressure RO process.

Effects of spinning conditions on structure and properties of aramid-based hollow fiber blend separation membranes

The rigid-rod-like poly(p-phenylene terephthalamide) (PPTA), as the raw material of aramid 1414, has the characteristics of high modulus and hydrophilicity. The flat sheet poly(vinylidene fluoride) (PVDF)/PPTA blend separation membranes with improved hydrophilicity and enhanced modulus have been successfully prepared using in situ polycondensation method in our previous study. In this study, PPTA/PVDF hollow fiber blend separation membranes with enhanced hydrophilicity and mechanical strength were fabricated through the dry–wet spinning technique. Monomers of PPTA were polymerized in the PVDF solution, and the polymerization system was directly used as the spinning solution to fabricate the hollow fiber blend membrane. The effects of spinning conditions including the air-gap distance; the composition of core fluid; and composition of coagulation bath on the structure and properties including the separation properties, surface hydrophilicity, and mechanical properties of PPTA/PVDF hollow fiber blend membranes were well investigated. Membrane surface and cross-sectional morphologies were observed through scanning electron microscope. The enhancements of these spinning conditions weakened the phase separation process as a result of the formation of a small pore structure. The pore size distribution, water flux, and solute rejection varied accordingly. Different spinning conditions have different effects on the mechanical and hydrophilic properties of the hollow fiber blend membranes. Compared with pure PVDF hollow fiber membrane, blend membranes fabricated under different spinning conditions exhibited enhanced surface hydrophilicity and tensile properties. Finally, the change rates of the pure water flux and the solute rejection with different spinning conditions were calculated to further analyze and compare the statistically significant effects.

Compostable composites of wheat stalk micro‐ and nanocrystalline cellulose and poly(butylene adipate‐co‐terephthalate): Surface properties and degradation behavior

ABSTRACTAn agricultural waste, the wheat stalk, was used for the extraction of microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC) via a series of thermochemical and mechanical treatments. The MCC and NCC were then compounded with the biodegradable polymer, poly(butylene adipate‐co‐terephthalate), PBAT, by melt mixing. The properties of the composites were evaluated by soil composting, contact angle and water absorption measurements, scanning electron microscopy (SEM) and gel permeation chromatography (GPC). The cellulosic filler was found, as per SEM results, to uniformly disperse in the polymer matrix forming a quite homogeneous composite which visibly degraded completely within a few months under soil composting and showed high water absorption, these properties being enhanced with the filler content. Compared to the neat PBAT, the composites showed enhanced surface hydrophilicity thereby increasing the ability of degradation. In spite of seemingly remarkable change in mechanical stability of the polymers under soil burial for several months, relatively low lowering of the molecular weight was observed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48149.

A highly permeable loose nanofiltration membrane prepared via layer assembled in-situ mineralization

Nanofiltration membrane with high water permeability and anti-fouling nature is particularly needed to be explored in dyeing wastewater treatment. Herein, a hydrophilic calcium carbonate/polyethyleneimine-gallic acid (CaCO3/PEI-GA) loose NF membrane was prepared via a layer assembled in-situ mineralization (LAIM) strategy. This strategy endowed the membrane with the following advantages: the formation an ultrathin CaCO3/PEI-GA selective layer with a thickness of 76 nm and the highly enhanced surface hydrophilicity due to in-situ formation of CaCO3 nanoparticles. As a result, the prepared CaCO3/PEI-GA loose NF membrane showed 154% higher water flux (48.5 L/(m2 h bar) vs. 19.1 L/(m2 h bar)) compared with the control polyethyleneimine-gallic acid (PEI-GA) loose NF membrane for 100 mg/L Congo red (CR) solution, with equivalent rejection (99.6% vs. 99.7%). Moreover, this membrane also displayed outstanding anti-fouling ability, i.e. flux recovery ratio (FRR) of 94.9% for 1000 mg/L humic acid (HA) solution, and excellent performance stability in separation of dye/salt (CR/NaCl) aqueous solution for 60 h. The aforementioned advantages of the CaCO3/PEI-GA loose NF membrane indicate its promising application in dyeing wastewater treatment.

Melamine-based covalent organic framework-incorporated thin film nanocomposite membrane for enhanced osmotic power generation

A melamine-based covalent organic framework (COF) nanomaterial, Schiff base network-1 (SNW-1), was incorporated into the polyamide layer of a novel thin film nanocomposite (TFN) pressure retarded osmosis (PRO) membrane. The deposition of SNW-1 was made on an open mesh fabric-reinforced polyamide-imide (PAI) support substrate through interfacial polymerization (IP). SNW-1 loading influence on the water permeability and osmotic power density during PRO operation was investigated. The porous and highly hydrophilic SNW-1 nanomaterial facilitated the flow of water molecules across the membranes, while maintaining satisfactory salt rejection ability of the polyamide selective layer. The membranes exhibited significantly enhanced surface hydrophilicity, water permeability, and power density. The mode of incorporation of SNW-1 during IP was also investigated and it was observed that the secondary amine groups of SNW-1 react with the carbonyl groups of 1,3,5-benzenetricarbonyl trichloride, the acyl halide precursor in polyamide formation; thus, SNW-1 was incorporated through the amine precursor, 1,3-phenylenediamine. Testing with 1.0 M NaCl as the draw solution, the TFN membrane with a loading of 0.02 wt% SNW-1 exhibited the highest water flux of 42.5 Lm−2 h−1 and power density of 12.1 Wm−2, while withstanding hydraulic pressure over 24 bar. This study suggests that COF-incorporation can be a promising method in PRO membrane fabrication to improve both osmotic performance and energy harvesting capability for the PRO process.

A loose NF membrane by grafting TiO2-HMDI nanoparticles on PES/β-CD substrate for dye/salt separation

In this study, a high flux loose nanofiltration (NF) membrane was fabricated for the desalination of dye wastewater through a facile method which combined doping and surface grafting. First, PES ultrafiltration substrate was prepared via non-solvent induced phase separation by introducing multi-hydroxyl β-cyclodextrin (β-CD) into the casting solution as hydrophilic additive. Then, titanium dioxide (TiO2) nanoparticles were grafted uniformly on membrane surface with the assistance of 1, 6-hexamethylene diisocyanate (HMDI), resulting in the enhancement of surface hydrophilicity and separation performance of the resultant membranes. Remarkably, the membrane prepared at optimized conditions achieved a high pure water flux (52.0 L·m−2·h−1 at 0.2 MPa) and high permeate flux for dyes (e.g. 30.5 L·m−2·h−1 for Congo Red at 0.2 MPa). It also exhibited high rejection for dyes (e.g. 97.4% for Congo Red) and high transmittance of salts (e.g. 94.0% for Na2SO4). Moreover, the membrane possessed good antifouling performance with a high flux recovery ratio of 93.7% after fouled by humic acid (HA). The results indicated that the novel loose NF membrane had an impressive potential application for dye wastewater treatment.

Development of Copper-Aluminum Layered Double Hydroxide in Thin Film Nanocomposite Nanofiltration Membrane for Water Purification Process.

This study aims to fabricate a thin film composite (TFC) membrane, modified with copper-aluminium layered double hydroxide (LDH) nanofillers via interfacial polymerization technique for nanofiltration (NF) processes. It was found that Cu-Al LDH nanofillers possessed layered structured materials with typical hexagonal plate-like shape and positive surface charge. The study revealed that TFN membrane exhibits a relatively smooth surface and a less nodular structure compared to pristine TFC membrane. The contact angle of TFN progressively decreased from 54.1° to 37.25°, indicating enhancement in surface hydrophilicity. Moreover, the incorporation of LDH nanofillers resulted in a less negative membrane as compared to the pristine TFC membrane. The best NF performance was achieved by TFN2 membrane with 0.1° of Cu-Al LDH loading and a water flux of 7.01 Lm-2h-1.bar. The addition of Cu-Al LDH resulted in excellent single salt rejections of Na2SO4 (96.8%), MgCl2 (95.6%), MgSO4 (95.4%), and NaCl (60.8%). The improvement in anti-fouling properties of resultant TFN membranes can be observed from the increments of pure water flux recovery and normalized water flux by 14% and 25% respectively. The findings indicated that Cu-Al LDH is a promising material in tailoring membrane surface properties and fouling resistance. The modification of the LDH-filled TFN membrane shows another alternative to fabricating a high-performance composite membrane, especially for water softening and partial desalination process.

Fabrication of Cellulose Acetate/Polyaziridine Blended Flat Sheet Membranes for Dialysis Application

Polyaziridine or polyetyleneimine (PEI) was introduced as filler in cellulose acetate (CA) to fabricate mixed matrix membrane (MMM) for hemodialysis. Diffusion-induced phase separation (DIPS) method was followed for making PEI/CA MMM membranes. Effect of variation in the amount PEI was also examined on the morphology and performance of CA membrane. The surface morphology of pure and MMM membranes was studied by SEM, AFM, contact angle, and FTIR. Results of all characterization techniques revealed homogenous and significant blending of PEI content into pure CA matrix. Moreover, performance efficiency of MMM membranes was investigated in terms of pure water flux (PWF), urea clearance, and bovine serum albumin (BSA) rejection. The concomitant decrease of contact angle from 78° to 69° in PEI/CA MMM membranes of varying composition successfully demonstrates enhancement in surface hydrophilicity of MMM membranes. For protein rejection, all PEI/CA MMM membranes rejected > 90% of BSA relative to 25% for pure CA membrane. Furthermore, urea clearance behavior for PEI/CA MMM membranes was 67.6% in comparison to 52% for pure CA membrane. The incorporation PEI appreciably enhanced the PWF, BSA rejection, and urea clearance of CA membrane for hemodialysis application.

Polysulfone/Iron Oxide Nanoparticles Ultrafltration Membrane for Adsorptive Removal of Phosphate from Aqueous Solution

Excessive nutrient contents in water bodies renders eutrophication and causes undesired structural changes to the environment. One of the most straightforward strategies to address eutrophication issue is through the removal of nutrients such as phosphate ions from the water sources. A combination of membrane filtration and adsorption process is an attractive alternative to remove phosphate from aqueous solution. In this work, polysulfone/iron oxide nanoparticles (PSf/IONPs) adsorptive nanocomposite ultrafiltration (UF) membrane was prepared via phase separation process. Flat sheet membranes were characterized using scanning electron microscopy, energy-dispersive X-ray spectrometry, contact angle, overall pore size, porosity and pure water flux (PWF). Results showed that the incorporation of IONPs greatly enhanced the membrane PWF from 10.0 L/m2/h to 55.2 L/m2/h, contributed by the enhanced surface hydrophilicity (contact angle = 63.9°), porosity (74.1%) and larger overall pore size (79.3 nm). It was revealed that the membrane possessed phosphate adsorption capacity of 73.5 mg/g. Filtration experiment demonstrated that the PSf/IONPs membrane exhibited efficient phosphate removal under a steady flux. The design of this adsorptive UF membrane could fulfil the current necessity to remove phosphate from wastewater.

Enhanced surface hydrophilicity of polylactic acid sutures treated by lipase and chitosan

Polylactic acid (PLA) surgical sutures are a new type of absorbable sutures that can be degraded and absorbed in the body. However, there is high hydrophobicity for the surface of PLA sutures, which leads to poor biocompatibility and cellular affinity. In order to increase the hydrophilicity, the PLA sutures were etched by lipase firstly, and then grafted with chitosan. The results indicate that the optimal conditions of treating PLA sutures by lipase were as follows: 45℃ reaction temperature, 4.5 g/L concentration of lipase and 8 h reaction time. The sutures were etched by lipase and then formed some grooves and a number of hydroxyl (-OH) bonds, which led to increased surface area and hydrophilicity, but a drop in mass and strength. The optimal conditions of grafting chitosan onto PLA sutures were as follows: 4 h reaction time and 3 g/L concentration of chitosan. The chitosan grafted and loaded on the surface of PLA sutures, and in some areas of the sutures the chitosan reunited, which led to a rough surface and large friction coefficient. Finally, the hydrophilicity of the PLA sutures, treated by lipase and then grafted with chitosan, was greatly improved.

Hyaluronic Acid and Chitosan Surface Grafted Polylactide Single Crystals as Hydrophilic Building Blocks for Scaffold Materials

Polylactide has a well-known biocompatibility and processability, but its surface hydrophobicity could limit their use as a proper scaffold for cell growth and proliferation. The present work aims to fabricate the polylactide scaffolds by a bottom-up approach from pre-modified building blocks as an efficient way to overcome such a challenge and to provide a surface with a spatially organized chemical structure. Pre-modified polylactide single crystals (PLLAsc) with chitosan or hyaluronic acid, which are hydrophilic and bioactive macromolecules, were assembled into three-dimensional scaffolds. PLLAsc were hydrolyzed to introduce carboxylic groups at the surface and then the grafting reactions were carried out by carbodiimide chemistry. Although chitosan was grafted directly, the hydrolyzed surface was endowed with adipic acid dihydrazide as a spacer before hyaluronic acid grafting. The analyses of the modified surfaces verified the enhancement in surface hydrophilicity without any drastic effects on single crystals properties. By fabricating the scaffolds by using a compression molding salt leaching technique in the absence of heat or gluing materials, they were found to have an open interconnected structure, a hydrophilic surface and sustainable mechanical properties. Biological activity of scaffolds was examined by using mouse fibroblasts. Scaffolds having hyaluronic acid and chitosan surface grafted PLLAsc showed better interface for cell growth than pristine ones. Obviously, prefunctionalized PLLAsc with biomacromolecules could be used as proper building blocks for designing polymer scaffolds.

A comprehensive description of the threshold flux during oil/water emulsion filtration to identify sustainable flux regimes for tannic acid (TA) dip-coated poly(vinylidene fluoride) (PVDF) membranes

In the separation of oil/water emulsions using membrane separation methods, fouling remains a problem. To improve the fouling resistance effectively, a hydrophilic tannic acid (TA) coating was constructed on the poly(vinylidene fluoride) (PVDF) membrane via dip-coating method. Both the wettability and surface free energy were dramatically enhanced after the introduction of the TA coating. TA deposition with extended dip-coating time did not result in a corresponding increase in the pure water permeate quality, suggesting that there is a trade-off between the enhanced surface hydrophilicity and diminished pore size. Furthermore, the threshold fluxes were determined using the flux-stepping method, and explored to provide guidance on membrane fouling rates for oil/water emulsion filtration. The hydrophilic TA dip-coated PVDF membrane prepared at a dip-coating time of 9 h exhibited the highest threshold flux compared to the other membranes. The experimental evidences of the threshold fluxes can be used to predict the sustainable flux regimes for the TA dip-coated membranes. Constant flux verifiable experiments for oil/water emulsion were performed at fluxes near and below the threshold fluxes. By selecting a constant flux strategy below the threshold flux, membrane over-fouling can be avoided efficiently and the operating period can be prolonged favourably. More generally, operation below the threshold flux recognizes a modest fouling level, arising from the sufficient flux, which would result in the infrequent need for cleaning and is a compromise between capital expenditure and operating costs.

Pi electron cloud mediated separation of aromatics using supported ionic liquid (SIL) membrane having antibacterial activity

Supported ionic liquid (SIL) membranes using imidazolium based ionic liquids and hydrophobic PTFE base membrane were used for the π electron mediated separation of aromatic compounds including dyes in aqueous and non-aqueous medium. The FTIR of SIL membranes showed the signature of the functionalities for both base membrane and the imidazolium moiety. A significant reduction in contact angle, especially the dynamic contact angle, was observed for SIL membranes compared to the virgin membrane indicating the enhancement in surface hydrophilicity of the membrane, while considerable changes zeta potential was seen at different pH indicating the modification in surface charge. The SEM image confirmed the pore filling of base membrane with ionic liquids. The stability of the SIL membranes were studied using hexane, water and DMF as solvents. Tuning the anionic moieties, ionic liquids were utilized for aqueous and non-aqueous application through SIL membranes. For non-aqueous applications, the trend in separation efficiency was found to be divinylbenzene > styrene > toluene, which was attributed to the more π electron cloud density on extended conjugation leading to favorable interaction with ionic liquid influencing its transfer through SIL membranes. Preferential separation of Congo red (CR) and Ramazol Brilliant Blue R (RBBR) was achieved in water based application of the SIL membranes. The anti-microbial activity of these SIL membranes were investigated using gram-positive bacteria (Staphylococcus aureus and Pseudomonas aeruginosa). More the number of carbon atom on the side chain of the imidazolium ring, more antimicrobial activity was observed.

Improving the hydrophilic and antifouling properties of poly(vinyl chloride) membranes by atom transfer radical polymerization grafting of poly(ionic liquid) brushes

In this study, poly(1‐butyl‐3‐vinylimidazolium bromide) (PBVIm‐Br) was grafted onto the poly(vinyl chloride) (PVC) membrane surface via a 2‐step atom transfer radical polymerization (ATRP) reaction. Poly(2‐hydroxyethylmethacrylate) (PHEMA) was grafted onto the membrane surface by aqueous ATRP reaction; then, BVIm‐Br was introduced onto the surface of the PHEMA‐modified PVC membrane through traditional ATRP reaction. The analysis of surface chemistry confirmed the successful grafting of PHEMA and PBVIm‐Br on PVC membrane surface, and the grafting density (GD) of PBVIm‐Br gradually increased as the grafting time was prolonged. The modified membrane exhibited a positive charge and significantly enhanced surface hydrophilicity. The static water contact angle of the membrane surface decreased from 92.3° to 51.6° as the GD of the PBVIm‐Br brushes increased. Filtration experiments indicated that the water flux of the modified membrane increased with increasing GD, and their recovered fluxes were more than twice than the original. In addition, the total fouling ratio of the membranes decreased from 89% in M0 to 67% in M5, and most of the fouling was reversible as the GD of PBVIm‐Br brushes increased. These results indicated that the positive charged poly(ionic liquid) brushes featuring hydrophilic properties would have potential applications in membrane separation.

Mixed-matrix membranes with enhanced antifouling activity: probing the surface-tailoring potential of Tiron and chromotropic acid for nano-TiO2.

Mixed-matrix membranes (MMMs) were developed by impregnating organofunctionalized nanoadditives within fouling-susceptible polysulfone matrix following the non-solvent induced phase separation (NIPS) method. The facile functionalization of nanoparticles of anatase TiO2 (nano-TiO2) by using two different organoligands, viz. Tiron and chromotropic acid, was carried out to obtain organofunctionalized nanoadditives, FT-nano-TiO2 and FC-nano-TiO2, respectively. The structural features of nanoadditives were evaluated by X-ray diffraction, X-ray photoelectron spectroscopy, Raman and Fourier transform infrared spectroscopy, which established that Tiron leads to the blending of chelating and bridging bidentate geometries for FT-nano-TiO2, whereas chromotropic acid produces bridging bidentate as well as monodentate geometries for FC-nano-TiO2. The surface chemistry of the studied membranes, polysulfone (Psf): FT-nano-TiO2 UF and Psf: FC-nano-TiO2 UF, was profoundly influenced by the benign distributions of the nanoadditives enriched with distinctly charged sites (), as evidenced by superior morphology, improved topography, enhanced surface hydrophilicity and altered electrokinetic features. The membranes exhibited enhanced solvent throughputs, viz. 3500–4000 and 3400–4300 LMD at 1 bar of transmembrane pressure, without significant compromise in their rejection attributes. The flux recovery ratios and fouling resistive behaviours of MMMs towards bovine serum albumin indicated that the nanoadditives could impart stable and appreciable antifouling activity, potentially aiding in a sustainable ultrafiltration performance.

Promising bio-composites of polypyrrole and chitosan: Surface protective and in vitro biocompatibility performance on 316L SS implants

Advanced biomedical materials can potentially be developed from combinations of natural biodegradable polymers and synthetic polymers. We synthesized bioactive composites based on polypyrrole/chitosan through in-situ electrochemical polymerization in oxalic acid medium. Surface characterization results revealed the influence of chitosan inclusion on polypyrrole (PPy) surface morphology. Contact angle results confirmed the enhancement in surface hydrophilicity due to the addition of chitosan into the PPy matrix. Electrochemical corrosion studies revealed that the composite coatings showed enhanced protective performance compared to pure PPy. Further, we investigated the effect of the composite coatings on the growth of MG-63 human osteoblast cells to assess their biocompatibility. Monte Carlo simulations were engaged to assess the interactions between the metal surface and composite coatings. The composite containing equal parts PPy and chitosan was found to be biocompatible; together with the corrosion protection results, the findings indicated that this bioactive coating material has potential for use in 316L SS implants.

Biomineralization potential and cellular response of PHB and PHBV blends with natural anionic polysaccharides

In this paper, the biomineralization potential and cellular response of novel blend films of the anionic sulfated polysaccharides kappa-carrageenan (KCG) and fucoidan (FUC) derived from seaweeds with semi-crystalline polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV), respectively, were analyzed. The incorporation of KCG and FUC into PHB and PHBV, which has been studied here for the first time, led to an overall decrease in crystallinity, enhanced surface hydrophilicity, reduced brittleness and faster degradation of the polymer blend films. All PHB/KCG, PHBV/KCG and PHBV/FUC films exhibited a two-stage mass loss profiles with pH stabilization. PHBV/KCG film showed the highest biomineralization activity due the presence of sulfate groups on the surface of the films. NIH3T3 cells attached and proliferated well on all blend films on account of enhanced surface hydrophilicity and improved flexibility. PHBV/KCG led to a promoted cellular activity compared to PHBV/FUC, presumably due to phase separation and higher amount of biopolymer on the film surface that was a consequence of the immiscibility of the polymers in the blend films.

Controllable Nanotribological Properties of Graphene Nanosheets

Graphene as one type of well-known solid lubricants possesses different nanotribological properties, due to the varied surface and structural characteristics caused by different preparation methods or post-processes. Graphene nanosheets with controllable surface wettability and structural defects were achieved by plasma treatment and thermal reduction. The nanotribological properties of graphene nanosheets were investigated using the calibrated atomic force microscopy. The friction force increases faster and faster with plasma treatment time, which results from the increase of surface wettability and the introduction of structural defects. Short-time plasma treatment increasing friction force is due to the enhancement of surface hydrophilicity. Longer-time plasma treatment increasing friction force can attribute to the combined effects of the enhanced surface hydrophilicity and the generated structural defects. The structural defects as a single factor also increase the friction force when the surface properties are unified by thermal reduction. The surface wettability and the nanotribological properties of plasma-treated graphene nanosheets can recover to its initial level over time. An improved spring model was proposed to elaborate the effects of surface wettability and structural defects on nanotribological properties at the atomic-scale.

Aramid nanofiber as an emerging nanofibrous modifier to enhance ultrafiltration and biological performances of polymeric membranes

Improving the filtration and biological performances of polymeric membranes has become a major bottle-neck to forward the membrane based separation and purification technologies. Herein, for the first time, we report the usage of aramid nanofiber (ANF) to enhance the ultrafiltration and biological performances of polysulfone (PSf) and polyethersulfone (PES) membranes. ANF is a relatively hydrophilic additive with a water contact angle around 40°; however, different from many other hydrophilic or amphiphilic additives, ANF is completely stable and non-dissolvable in water, which makes it an ideal modifier for generating hydrophilic composite membranes. After the addition of ANF, the membranes exhibit more porous structures and enhanced surface hydrophilicity. The flux recovery ratio, protein adsorption and bacterial adhesion tests validate that the ANF modified membranes own improved antifouling properties. Notably, the ANF modified membranes also show improved blood compatibility in terms of limited protein adsorption, suppressed platelet adhesion and activation, inhibited coagulant factors and complementary factors activation. Furthermore, the addition of ANF enables more efficient adsorption of small molecular creatinine toxins during dialysis applications of the composite membranes. In general, this hydrophilic, low-cost, and nanofibrous ANF modifier will be of promising potential for the modification of ultrafiltration membranes and forward their applications in water purification and hemodialysis.

Sulfonated multiwall carbon nanotubes assisted thin-film nanocomposite membrane with enhanced water flux and anti-fouling property

Sulfonated multiwall carbon nanotube (SMWCNT) with pendant alkyl sulfonic acid groups was synthesized from hydroxyl-functionalized multiwall carbon nanotube (MWCNT-OH). Small changes in microstructure, due to nucleophilic substitution reaction, were confirmed by X-ray photoelectron spectroscopy, transmission electron microscopy, and N2 adsorption-desorption measurements. Prepared SMWCNT exhibited excellent water dispersity, which facilitated interfacial polymerization to prepare novel poly(piperazine amide) thin-film nanocomposite (TFN) membranes. Water flux and salt rejections of the TFN membranes were readily adjusted by optimizing the SMWCNT content, to get most optimum separation performance. TFN-0.01% showed high water flux of 13.2Lm−2h−1bar−1, 1.6 times more than the pristine thin-film composite (TFC) membrane, maintaining reasonably high rejection of 96.8% to Na2SO4. TFN-0.01% membrane, with enhanced surface hydrophilicity exhibited better anti-fouling ability to bovine serum albumin with water flux recovery ratio as high as 91.2%, even after two “fouling-washing” cycles, compared to 82.0% for TFC membrane.