Thin-film Nanofibrous Composite Membranes Research Articles

An electrochemical impedance spectroscopy study on ion-fouling of forward osmosis membranes

Forward osmosis (FO) has been rapidly developed and employed in the industrial and environmental wastewater treatment, whose performance is affected profoundly by membrane fouling. Electrochemical impedance spectroscopy (EIS), as a nondestructive and low-cost evaluation technique, has been increasingly used for the characterization of membrane structures and membrane fouling. However, monitoring ion fouling of FO membranes is difficult with EIS due to the weak signal. In this work, the ion-fouling of various FO membranes was successfully characterized by EIS and the inductance variation was firstly utilized to interpret the degree of FO membrane fouling. Multi-walled carbon nanotubes (MWCNTs) and polydopamine (PDA) were modified onto the thin film nanofibrous composite membrane (#FO-0) as anti-fouling modification (#FO-MWCNTs and #FO-PDA), respectively. The structural measurements of #FO-0, #FO-MWCNTs, and #FO-PDA were achieved by a two-electrode EIS system. Then the ion fouling of FO membranes was monitored by a four-electrode EIS system. Through the equivalent circuit fitting, the correlation between the inductance variation and the membrane fouling was established. The FO experiments further validated the effectiveness of the proposed EIS method. The results indicate that inductance as a detection index is expected to be a convenient tool for studying the ion-fouling phenomenon in the FO process.

Low temperature regulated reverse interfacial polymerization for fabricating thin film composite membranes based on nanofibrous substrates

In this study, a novel thin film nanofibrous composite (TFNC) nanofiltration (NF) membranes comprised of polyacrylonitrile (PAN) nanofibrous supporting layer and polyamide (PA) compact separating layer was constructed by low-temperature-controlled reverse interfacial polymerization (LTIP-R) at − 5 °C. The strategy for lowering the temperature of organic phase solution played a crucial role in forming a dense and thin PA layer on the PAN nanofibrous substrate with submicron pores. The results revealed that the reduced evaporation rate of organic phase at low temperature was contributed to maintaining a complete and uniform interface for the following reverse IP process, effectively overcoming shortcomings of surface incompleteness and easy infiltration of PA barrier layer. Owing to the reduced thickness and the enhanced wholeness of the PA separating layer via LTIP-R, the optimized TFNC membranes exhibited NF performance with great rejection of divalent salt ions (98.2%) and an improved permeation (13.3 L‧m−2‧h−1‧bar−1). This work would provide an efficient and facile method to fabricate high performance NF membranes for practical applications.

Composite nanofiltration membrane prepared by depositing barium alginate interlayer on electrospun polyacrylonitrile substrate

Interlayer-regulated thin-film nanofibrous composite (TFNC) membranes were fabricated extensively for seawater purification, but the mechanical and stability performance of the composite membranes continually existed a tremendous challenge. In this work, a composite nanofiltration (NF) membrane was prepared by interfacial polymerization (IP) method of piperazine (PIP) and trimesoyl chloride (TMC) combined through coating barium alginate (BaAlg) on the polyacrylonitrile substrate obtained by the electrospun technology. With the deposition of the BaAlg hydrogel interlayer, the diffusion rate of PIP depressed and a homogeneous polyamide (PA) selective layer could be realized. The TFNC membranes of BaAlg interlayer modified via cross-linking sodium alginate (SA) with barium ions had higher stability, hydrophilicity and separation performance. The impact of SA content, operating pressure and time on the NF membrane desalination performance was explored. The mechanical properties of composite NF membranes were greatly improved and the tensile strength could be as high as 8.17 MPa. The preferred TFNC membranes could display a permeation flux of 112.5 ± 1.8 L·m−2·h−1, and the Na2SO4 retention rate was up to 98.7 ± 0.5 %. The prepared NF membranes are of great importance in seawater purification, which is conducive to obtaining high performance with excellent development potential.

Coaxial electrospun nanofibrous substrates with tunable wettability for constructing cucurbit[n]uril-embedded organic solvent nanofiltration membranes

Solvent resistance and high perm-selectivity have always been the pursuit in organic solvent nanofiltration field. Insoluble polyimide nanofibrous membranes feature superior solvent resistance. However, its high hydrophobicity usually limits the uniform spread of the aqueous amine monomers during the interfacial polymerization process, resulting in the non-uniform reaction with the acyl chloride and the defective selective layer. Herein, coaxial electrospinning was employed to construct the core–shell nanofibrous substrates, in which aminated multi-walled carbon nanotubes were added to the shell layer. This strategy endowed the nanofibrous substrates with tunable wettability without sacrificing stability, which guaranteed the one-step construction of defect-free thin-film nanofibrous composite membranes via interfacial polymerization (IP). Further, cucurbit[6]uril was embedded into the polyamide network by coupling host–guest chemistry and IP, providing the wider solvent transport channels and achieving the four times enhanced methanol permeance (22.34 L·m−2·h−1·bar−1) without sacrificing the selectivity. The membrane shows application prospects for solvent recovery in chemical, pharmaceutical, and other fields. This work provides new thoughts for the design and modification of novel nanofiltration membranes.

Acid mine drainage treatment by fertilizer drawn forward osmosis for irrigation

This work utilized fertilizer driven forward osmosis (FDFO) to extract fresh water from acid mine drainage (AMD) wastewater for irrigation, and investigated the effects of draw solutes on membrane fouling behaviours. The carbon nanotubes (CNTs) and polydopamine (PDA) were coated on the thin film nanofibrous composite (TFNC) membrane #FO-0 as anti-fouling modification. When 1 M NH4H2PO4 (MAP) and 500 mg/L copper AMD wastewater (pH=3.0) used as draw and feed solutions, #FO-0 and PDA-coated TFNC membrane (#FO-PDA) exhibited rapid declines of water fluxes due to the dense fouling layer. In contrast, the CNT-coated membrane #FO-CNT exhibited the lowest flux decline of 26.0% attributed to better hydrophilicity, the lowest roughness and neutral surface charge. All the TFNC membranes exhibited insignificant membrane fouling when (NH4)2SO4 (SOA) was used as draw solute. Additionally, the osmotic backwashing could effectively recover water flux. The discharged draw solution promoted plant growth without posed potential health threat.

Highly permeable composite nanofiltration membrane via γ-cyclodextrin modulation for multiple applications

The treatment of pharmaceutical wastewater has become a worldwide problem. Highly efficient treatment for wastewater is extremely critical for ecological environment. Herein, a thin-film nanofibrous composite (TFNC) nanofiltration (NF) membrane modulated by γ-cyclodextrin (γ-CD) was prepared via interfacial polymerization. The γ-CD and piperazine (PIP) were adopted and acting as the mixed reaction monomers in aqueous phase for the fabrication of the separation layer. Not only PIP, γ-CD units would also react with organic phase trimesoyl chloride (TMC) at the interface and participate into the polymerization network. Compared with pure polyamide TFNC membranes, the γ-CD modulated TFNC membranes demonstrated thinner skin thickness. Owing to the 3D hollow structure of γ-CD, the self-contained through cavities would provide additional direct nanochannels to facilitate the water transport. Under 0.5 MPa, the optimized PIP0.5γCD0.5 and PIP0.5γCD1.5 TFNC membranes showed much higher permeate flux of 23.27 and 26.34 L m-2h−1 bar−1, respectively, than that of pure polyamide membranes (9.13 and 9.85 L m-2h−1 bar−1) and the Na2SO4 rejection remained high (>98.7%). Moreover, both TFNC membranes exhibited extremely high rejection (>99%) for several pharmaceuticals (doxycycline hydrochloride, tetracycline, and amoxicillin), and the PIP0.5γCD0.5 TFNC membrane exhibited a good separation factor (31.8) for NaCl/tetracycline solution. In addition, both optimized TFNC membranes showed good pressure resistance and long-term operating stability. This research revealed a facile modulation strategy for the fabrication of high-performance NF membrane and indicated the great promise for desalination, pharmaceuticals wastewater treatment and antibiotics concentration.

Development of high‐flux aciduric ultra‐thin nanofibrous pervaporation composite membrane for acetic acid dehydration

AbstractAcetic acid is an essential intermediate chemical in industry. Traditional inorganic membrane cannot meet the demand of high‐efficient dehydration and polymeric membrane is restricted by its low organic solution resistance. In this work, a novel aciduric pervaporation composite membrane was successfully generated by fabricating an ultrathin polysulfonamide (PSA) layer on the polyacrylonitrile (PAN) nanofibrous substrate via interfacial polymerization (IP) method. Through the optimization of fabrication process including selecting the suitable structure of diamine (taking three types aliphatic amines as candidates), optimizing the concentration of two phase solutions, the resultant thin‐film nanofibrous composite (TFNC) membrane was fabricated by using aliphatic amine triethylenetetramine (TETA: 3.0 wt%) and 1, 3‐benzenedisulfonyl chloride (BDSC: 1.0 wt%) as IP monomers and the network structure with suitable sieving size was constructed. The ultrathin aciduric PSA selective layer (thickness: 104 ± 15 nm) endowed the TFNC membrane with excellent separation efficiency. For dehydrating 70 wt% acetic acid aqueous solution at 60°C, PSA‐3.0‐1.0/PAN TFNC membrane exhibited competitive separation efficiency and great acid stability. It possessed extremely high permeate flux (15,321 g/m2 h) with stable separation factor (109). For long‐term acid dehydration evaluation, PSA/PAN membrane showed great stability during 7 days pervaporation. This work took advantage of traditional IP method for designing a novel pervaporation membrane with aciduric chemical structure, suggested an effective and facile approach to develop novel pervaporation membranes for harsh environment separation.

Coordination of Copper Ion Crosslinked Composite Beads with Enhanced Toxins Adsorption and Thin-Film Nanofibrous Composite Membrane for Realizing the Lightweight Hemodialysis

Coordination of Copper Ion Crosslinked Composite Beads with Enhanced Toxins Adsorption and Thin-Film Nanofibrous Composite Membrane for Realizing the Lightweight Hemodialysis

High-performance TFNC membrane with adsorption assisted for removal of Pb(II) and other contaminants

Rapid and thorough removal of heavy metal ions in wastewater is critical for the urgent need of clean water. Herein, we prepared a high-performance thin film nanofibrous composite (TFNC) membrane consisting of a polyacrylonitrile (PAN)-UiO-66-(COOH)2 composite nanofibrous substrate (CPAN) and a calcium alginate (CaAlg) skin layer. Owing to abundant adsorption sites of UiO-66-(COOH)2 MOF, the optimal CPAN-2 nanofibrous substrate showed excellent adsorption capacity for lead ions. The maximum Pb2+ adsorption capacity of CPAN-2 substrate calculated by Langmuir isotherm model was 254.5 mg/g. Meanwhile, due to the relatively loose structure of CaAlg skin layer, this TFNC membrane showed high water permeate flux about 50 L m−2h−1 at 0.1 MPa, and the rejection for dyes was higher than 95%. Therefore, CaAlg/CPAN TFNC membranes were appropriate for dynamic adsorption/filtration to remove Pb2+. Compared with original CaAlg/PAN membrane, the optimal CaAlg/CPAN TFNC membrane showed much better ability to treat Pb(II)-containing wastewater and had good recyclability. Most importantly, the CaAlg/CPAN TFNC membrane could treat 7659 L m−2 wastewater containing single lead ions under WHO drinking water standard, and effectively deal with more simulated lead-containing wastewater. This work could provide a substitutable solution for effective removal of heavy metal ions and other various contaminants in wastewater.

Dialysis/adsorption bifunctional thin-film nanofibrous composite membrane for creatinine clearance in portable artificial kidney

In this study, we proposed a facile strategy for the lightweight design for portable artificial kidney by using a novel dialysis/adsorption bifunctional thin-film nanofibrous composite (TFNC) membrane, which consisting of polyvinyl alcohol (PVA) hydrogel as a separation layer and polyacrylonitrile (PAN) nanofibrous membrane with UiO-66-(COOH)2 nanoparticles as a porous affinity substrate were developed to effectively remove creatinine and substantially reduce the volume of dialysate in dialysis process simultaneously. Here, as-synthesized UiO-66-(COOH)2 nanoparticles were strung through PAN nanofibers using colloid-electrospinning technique to prepare necklace-like nanofibrous affinity membrane for creatinine adsorption. The obtained PAN/UiO-66-(COOH)2 nanofibrous membrane (PAN-U) with optimum UiO-66-(COOH)2 loading (60 wt%) exhibited encouraging maximum adsorption capacities (54 mg/g) based on Langmuir isotherm models and pseudo-second-order kinetic models. In addition, the simulated dialysis results demonstrated that 62.8% of creatinine were eliminated and over 98% of bovine serum albumin (BSA) were rejected. Furthermore, the PVA/PAN-U TFNC membrane not only improved the clearance of creatinine in simulated blood, but also efficiently maintained the concentration of creatinine in simulated dialysate at a very low level compared to the pure PVA/PAN TFNC membrane. More importantly, the usage of dialysate in volume for PVA/PAN-U TFNC membranes in dialysis was only one tenth of that for PVA/PAN TFNC membranes but with very comparable dialysis performance. Therefore, the introduction of adsorption function in TFNC hemodialysis membrane may facilitate the development of the lightweight of portable artificial kidney.

High permeability composite nanofiltration membrane assisted by introducing TpPa covalent organic frameworks interlayer with nanorods for desalination and NaCl/dye separation

• A TpPa layer with nanorods was prepared as an auxiliary interlayer. • TpPa interlayer played a decisive role for the formation of PA skin layer. • The PA/TpPa-12/PAN membrane showed excellent nanofiltration performance and NaCl/dyes selectivity. Nanofiltration (NF) membrane with high permeability and selectivity is extremely crucial for water purification. Herein, we prepared a high permeability thin-film nanofibrous composite (TFNC) membrane via interfacial polymerization (IP) technique assisted by introducing TpPa covalent organic frameworks (COFs) interlayer with nanorods on the polyacrylonitrile (PAN) nanofibrous substrate for NF. TpPa COFs interlayer with nanorods played a decisive role in adjusting the structure and performance of polyamide (PA) skin layer. On the one hand, TpPa COFs interlayer could regulate the diffusion and transfer rate of piperazine in the aqueous phase solution during IP process, which would modulate the mophology and reduce the thickness of the PA skin layer. Meanwhile, the TpPa COFs nanorods could create massive voids under PA layer to enhance the flux of TFNC membrane. Additionally, the TpPa COFs with nanoporous structure themselves also provided additional nanochannels for water transport. The structure of COFs interlayer could be tuned by altering the Pa contents of aqueous phase solution, which further optimized the overall performance. The permeation water flux of optimal TFNC membrane could reach to 104.8 L m −2 h −1 with a relatively high rejection of 98.4% for Na 2 SO 4 under 0.5 MPa, which was about 2.3 times than that of the unmodified PA membrane prepared without TpPa COFs interlayer. Besides, the optimal membrane exhibited good selectivity to NaCl/dye solution (NaCl/Acid Fuchsin was 402.5 and NaCl/Congo Red was 398.0) and long-term test stability. This work showed a new avenue to prepare high-performance NF membrane for the potential applications in water desalination and dye wastewater recovery.

Highly solvent-durable thin-film molecular sieve membranes with insoluble polyimide nanofibrous substrate

Permselective thin-film composite membranes are gaining a significant role in solvent-based molecular sieving applications. Nevertheless, the lack of desirable substrate materials, which combines high flux, solvent resistance as well as a straightforward fabrication process, is still the biggest bottleneck for large-scale commercial implementation. For the first time, we propose to fabricate an insoluble polyimide nanofibrous substrate by a sequential strategy involving electrospinning polyamic acid followed by a thermal imidization. The water-absent electrospinning process leads to 1-fold enhanced mechanical strength and higher solvent-resistance of substrate compared to the conventional phase inversion process. The resultant thin-film nanofibrous composite (TFNC) membranes exhibit exceptional potential for nanofiltration by showing high permeability, rejection, and stability in water as well as polar aprotic solvents such as dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran compared to state-of-art membranes. The strategy of using electrospun insoluble polyimide as the substrate establishes a scalable approach to design high-performance TFNC membranes for a wide range of challenging molecular sieving applications.

Electrospun transition layer that enhances the structure and performance of thin-film nanofibrous composite membranes

Electrospun nanofibers with completely interconnected pore structures are increasingly considered as substrates for fabricating thin-film nanofibrous composite (TFNC) nanofiltration (NF) membranes. The poor adhesion between the large-pore substrate and dense selective layer has been considered as the bottleneck for wide application. This work presents the role of a transition layer on membrane structure as well as performance enhancement. Specifically, both polyethyleneimine (PEI)/polyacrylonitrile (PAN) transition layer and PAN substrate layer are formed by electrospinning. Interfacial polymerization (IP) is subsequently performed with trimesoyl chloride and piperazine. The introduction of the PEI modified transition layer improves the hydrophilicity, provides additional reaction sites for IP, and avoids the polymerization in the pores of nanofibers. The resultant composite NF membranes exhibit a compact and defect-free selective layer. Such an optimal structure leads to an excellent separation performance of 95.6% for orange ΙΙ dye (MW = 350.32 g/mol) rejection and 38.5 L m−2h−1 bar-1 for the pure water permeability. It exhibits stable long-term performance during low pressure (0.2 MPa) nanofiltration, which will afford significant directions for the actual application of the TFNC membranes in water purification and other fields.

Novel gelatin/polyacrylonitrile thin film nanofibrous composite membranes with high filtration performance

High performance thin film nanofibrous composite (TFNC) membrane consisting of a thin gelatin (GE) selective skin layer and a polyacrylonitrile (PAN) nanofibrous substrate was fabricated in this work. Ultrathin GE nanofibers were electrospun and deposited onto the PAN nanofibrous supporting membranes and followed by moistening treatment and hot-pressing treatment. The moistened electrospun GE nanofibers would be melted and pressed into an integrated selective skin layer on the porous PAN nanofibrous membranes. The treated GE/PAN double-layer membranes were then chemically cross-linked by glutaraldehyde (GA). The depositing time of GE nanofibers was optimized to achieve a thin and integrated GE separating layer. The optimized GE/PAN TFNC membrane exhibited high flux (182.1 L m−2 h−1) and rejection (98.3%) in BSA test at 0.3 MPa. In addition, the GE/PAN composite membrane possessed great mechanical stabilities.

Salt-tuned fabrication of novel polyamide composite nanofiltration membranes with three-dimensional turing structures for effective desalination

High performance thin-film nanofibrous composite (TFNC) membranes with Turing structures were constructed by interfacial polymerization (IP) of trimesoyl chloride (TMC) and piperazine (PIP) tuned with high content salt (NaCl) in aqueous phase onto a polyacrylonitrile (PAN) nanofibrous mat for nanofiltration (NF). The concentration of salt in aqueous phase played a key role in the structural transition of polyamide (PA) membrane surfaces with two type Turing structures from the crossed ridge networks to crowed nodular arrays. The introduction of NaCl induced the uneven distribution of the IP reaction and could fine-tune the hydrophilicity and compactness of the formed ultrathin PA layer. The skillful manipulation of IP by regulating the NaCl content in aqueous phase enabled a great improvement in NF performance. Under 0.5 MPa, the flux of the optimized TFNC membrane (20.0 wt% NaCl in aqueous phase) reached 129.0 L m-2 h-1 (Na2SO4 rejection was 99.1%) which was approximately 2.5 times greater than that of the original membrane fabricated without salt addition. Moreover, the resultant membrane exhibited excellent stability and anti-fouling properties for long-term use. This approach is easy to be connected with commercialized IP technology to prepare high-performance NF membranes.

Engineering a superwetting thin film nanofibrous composite membrane with excellent antifouling and self-cleaning properties to separate surfactant-stabilized oil-in-water emulsions

In recent years, novel superwetting membranes have gained popularity for oily wastewater treatments via synergy between surface chemistry and topography. However, the water fluxes of the superwetting membranes normally decrease rapidly due to pore clogging and surface fouling, especially when treating surfactant-stabilized oil-in-water emulsions. Herein, a facile strategy is proposed to develop a superwetting thin film nanofibrous composite (TFNC) membrane with remarkable antifouling and self-cleaning properties to effectively separate surfactant-stabilized oil-in-water emulsions. The membrane is composed of an ultrathin carbon nanotubes (CNTs)-polyvinyl alcohol (PVA) composite skin layer, and a highly porous electrospun nanofibrous substrate as well as a non-woven mechanical support. The robust three-dimensional (3D) CNTs composite skin layer were immobilized on the nanofibrous substrate surface by crosslinking the CNTs with PVA. This skin layer serves as a functional barrier to reject oil droplets, which exhibited excellent performance in treating surfactant-stabilized oil-in-water emulsions with a rejection of 95% and a competitive flux of ~60 Lm−2h−1 under an ultra-low pressure (20 kPa) in a cross-flow filtration process. Moreover, the CNTs composite layer also protects the membrane surface from fouling. The TFNC membrane possesses outstanding reusability, as the water flux could be recovered by 100% in a continuous cyclic operation without cleaning, which should be attributed to the underwater oil repellence of its superhydrophilic surface and self-cleaning property based on the capillary pumping effect occurred in the micron/nano-channels of the membrane surface.

Biomimetic sulfated silk nanofibrils for constructing rapid mid-molecule toxins removal nanochannels

Biomacromolecules and their assemblies exhibit the great potential for biomimetic construction of novel and functional nanomaterials. In this work, sulfated silk nanofibrils (SSNFs) were firstly prepared with special designed sulfated silk fibroin molecule by a facile self-assembly technique, which were incorporated into the poly (vinyl alcohol) (PVA) hydrogel. Then they were together coated on the electrospun polyacrlonitrile (PAN) nanofibrous scaffold to fabricate a novel PVA/SSNFs/PAN thin film nanofibrous composite (TFNC) membranes for hemodiafiltration. Combining the results from filtration and hemodiafiltration tests, it could be deduced that the formation of nanogaps between PVA matrix and SSNFs provided more nanochannels for water and uremic toxins to transport rapidly through the functional layer. Especially the incorporation of SSNFs into PVA hydrogel layer endowed PVA/SSNFs TFNC hemodiafiltration membranes with rapid mid-molecule toxins removal channels. PVA/SSNFs-5 could clear 65.7% of lysozyme, also maintaining 85.0% clearance of urea and 94.7% interception of BSA after 4 h of dialysis. In addition, the blood compatibility of PVA/SSNFs TFNC membranes was also enhanced after the introduction of biomimetic SSNFs due to the heparin-like structure of sulfated silk fibroin (SSF). The biomimetic assembly route demonstrated here represents a green and efficient way for designing various functional nanomaterials in bio-nanotechnologies.

High performance polyamide composite nanofiltration membranes via reverse interfacial polymerization with the synergistic interaction of gelatin interlayer and trimesoyl chloride

A novel polyamide (PA) thin film nanofibrous composite (TFNC) nanofiltration membrane consisted of electrospun polyacrylonitrile (PAN) nanofibrous substrate, gelatin interlayer and polyamide barrier layer was fabricated by reverse interfacial polymerization (IP-R). The prepared PA separating layer was ultrathin, crumpled, and defect-free, which was benefited from the synergistic interaction of the gelatin nanofibrous interlayer and trimesoyl chloride (TMC). The ultrafine gelatin nanofibrous interlayer could absorb and react with TMC in n-hexane, regulating the rising speed of the n-hexane under aqueous phase for the formation of the polyamide layer. Significantly, the nanofiltration performance of TFNC membranes was tuned by changing the deposition amount of gelatin in the nanofibrous interlayer. The flux of the optimized TFNC membrane was up to 135.6 L m−2 h−1 (about 98.1% Na2SO4 rejection) under 0.5 MPa, which was nearly triple fold of that of the membrane prepared at the same condition by interfacial polymerization (IP–F). This work may provide an efficient and facile approach to fabricate high performance nanofiltration membranes with unique structures.

Novel thin-film nanofibrous composite membranes containing directional toxin transport nanochannels for efficient and safe hemodialysis application

Polymeric hemodialysis (HD) membranes with limited porosities, tortuous pores, and broad pore size distributions suffer from a trade-off between permeability-i.e., how fast toxins pass through the membranes-and selectivity-i.e., to what extent necessary proteins are retained. Here, a novel thin-film nanofibrous composite (TFNC) membrane, composed of an electrospun polyacrylonitrile (PAN) nanofibrous support layer and a chemically cross-linked polyvinyl alcohol (PVA) separation layer filled with heparin functionalized multi-walled carbon nanotubes (Hep-g-pMWCNTs), was demonstrated for efficient and safe HD application. Combining dialysis simulation experiments and pore-flow model, we demonstrated that the formation of free nanogaps at the interface between Hep-g-pMWCNTs and PVA matrix provided additional directional nanochannels for toxins to transport. The membranes showed efficient toxins removal without sacrificing selectivity (with the urea clearance of 88.2%, lysozyme clearance of 58.6%, and bovine serum albumin retention of 98.4% in a 4 h simulating dialysis). Especially, the efficiency in removing middle molecule toxins increased obviously compared with the values reported to date. Besides, the membranes exhibited excellent hemocompatibility: high resistance to protein adsorption, suppressed platelet adhesion, favorable anticoagulant activity, limited hemolysis ratio, and low complement activation. These facts suggested that the Hep-g-pMWCNTs/PVA/PAN TFNC membranes with superior comprehensive performances presented great potential for HD application.

Constructing zwitterionic coatings on thin-film nanofibrous composite membrane substrate for multifunctionality

In this work, we construct zwitterionic multilayers on poly(vinyl alcohol) (PVA) thin-film nanofibrous composite (TFNC) substrate via a facile surface engineered layer-by-layer (LBL) assembly of poly (sulfobetaine methacrylate) (PSBMA) and tannic acid (TA, a polyphenol), which endowed the modified membranes with multifunctionality for filtration of proteins and dyes and potential biomedical application. Characterizations of surface chemical structure and morphology of the modified membranes confirmed the successful zwitterionic self-assembly modification. The LBL-assembled membranes showed superior separation performance for filtration of proteins and dyes. Especially when the number of TA/PSBMA bilayer was 6, the PVA-6BL-M possessed high permeate flux (311.7 Lm−2 h−1) and excellent rejection (99.9%) for 0.1 g/L Direct Red 80 solution at 0.6 MPa. After being covered more TA/PSBMA bilayers, the LBL-assembled membranes could not only sieve smaller molecules of proteins and dyes well, but also exhibit better anti-biofouling properties (higher water flux recovery ratio, negligible irreversible fouling and the less BSA, E. coli and S. aureus bacteria adsorption). In addition, the LBL-assembled membranes presented excellent blood compatibility (greatly reduced platelet adhesion, significantly increased clotting time and lower hemolysis ratio), which indicated great potential for biomedical application. This work provided a facile and efficient method for designing a multifunctional TFNC membrane for water treatment and biomedical engineering.