Albumin Rejection Research Articles

Reed Rhizome Residue-Based Activated Carbon Adsorption Ultrafiltration Membranes for Enhanced MB Removal.

Novel adsorption ultrafiltration (ADUF) membrane was designed for the removal of methylene blue (MB) by introducing Chinese herbal waste-based activated carbon (AC) into the ultrafiltration membrane. We prepared AC particles from Chinese herbal medicine waste residue (reed rhizome residue) as a raw material by ZnCl2 activation and introduced them into the ultrafiltration membrane by phase inversion to prepare a reed rhizome residue-based activated carbon adsorption ultrafiltration (RAC-ADUF) membrane. The RAC-ADUF-0.1 membrane was characterized by a series of physical structures and chemical properties, which showed that the prepared membrane has a more hydrophilic surface and high porosity. The RAC-ADUF-0.1 membrane showed an excellent pure water flux of 255.77 L·m-2·h-1 and a high bovine serum albumin rejection of 99.3%. The RAC-ADUF membranes also possessed excellent antifouling performance. Notably, the RAC-ADUF-0.1 membrane provides excellent removal of MB (99% retention) compared to conventional ultrafiltration membranes. The static adsorption capacity was up to 238.48 mg/g. The significant increase in dynamic adsorption capacity on the RAC-ADUF membrane is due to the three-dimensional distribution of RAC particles on the PSF membrane cross section, which provides more active sites and increases the contact time between RAC and MB. By fitting the adsorption kinetics and isothermal adsorption curves, the results showed that the pseudo-second-order kinetic model and the Langmuir isothermal model were more accurate in explaining the adsorption process. Further kinetic analysis showed that the adsorption process of MB molecules on RAC-ADUF membranes is controlled by both external mass transfer and intraparticle diffusion, with intraparticle diffusion playing a dominant role. In addition, the RAC-ADUF membrane exhibited outstanding adsorption and regeneration abilities, and the MB removal rate stayed at about 95% after 8 adsorption regeneration experiments. In conclusion, this study provides a new idea for the preparation strategy of an adsorption ultrafiltration membrane with high rejection and high permeability and the reuse of Chinese herbal medicine waste residue.

In-situ photoreduction strategy for synthesis of silver nanoparticle-loaded PVDF ultrafiltration membrane with high antibacterial performance and stability.

Ultrafiltration (UF) technology using polyvinylidene fluoride (PVDF) membrane has been widely applied to water and wastewater treatment due to its low cost and simple operation process. However, PVDF-based UF membrane always encountered the issue of membrane biofouling that greatly impacted the filtration performance. In this study, we prepare a silver nanoparticle (AgNP)-loaded PVDF (Ag/PVDF) UF membrane by an in-situ photoreduction method to mitigate the membrane biofouling. Different from the previously reported method, AgNPs were synthesized in-situ by a UV photoreduction process, in which Ag+ ions were reduced to zero-valent Ag nanoparticles by the photo-induced reducing radicals. Antibacterial experiments showed that the inhibition efficiency of Ag/PVDF membrane to Escherichia coli reached up to ~ 99% after antibacterial treatment for 24h. In comparison with the pristine PVDF membrane, Ag/PVDF membrane possessed a lower water contact angle (83.7° vs. 38.1°), and its pure water flux increased by 23.7%, and a high bovine serum albumin (BSA) rejection efficiency was maintained. In addition, the high stability of the Ag/PVDF composite membrane was confirmed by the extremely low releasing amount of Ag. This study provides a novel strategy for the preparation of metal nanoparticle-incorporated Ag/PVDF ultrafiltration composite membrane showing favorable antibacterial performance and stability.

CrosslinkedPMIAultrafiltration membrane with enhanced permeability via incorporatingTMCmonomer

AbstractA trade‐off behavior is noteworthy between protein rejection and pure water flux (PWF) for ultrafiltration membranes; it is recommendable to increase flux without reducing selectivity. The poly (meta‐phenylene isophthalamide) (PMIA) ultrafiltration membrane was modified via incorporating 1,3,5‐benzene tricarboxylic chloride (TMC) to optimize the performance for the first time. Molecular dynamics (MD) simulation was applied to probe the mechanism of the effects of the concentrations of cosolvent LiCl and addition TMC on the dissolving process. It was turned out that a suitable concentration of TMC in the dope solution markedly enhanced the PWF (from 276.22 to 566.20 m−2 h−1 bar−1) with an increasing bovine serum albumin rejection (from 92.05% to 94.64%). Besides, the optimized membrane also possesses excellent anti‐fouling and mechanical performance. These improvements can be due to the crosslinking between PMIA and TMC and enlarged average pore diameter. This work broadens the application of PMIA and TMC in ultrafiltration and provides a novel methodology for PMIA modification.

Highly Robust Laser-Induced Graphene (LIG) Ultrafiltration Membrane with a Stable Microporous Structure.

Laser-induced graphene (LIG) materials have great potential in water treatment applications. Herein, we report the fabrication of a mechanically robust electroconductive LIG membrane with tailored separation properties for ultrafiltration (UF) applications. These LIG membranes are facilely fabricated by directly lasing poly(ether sulfone) (PES) membrane support. Control PES membranes were fabricated through a nonsolvent-induced phase separation (NIPS) technique. A major finding was that when PES UF membranes were treated with glycerol, the membrane porous structure remained almost unchanged upon drying, which also assisted with protecting the membrane's nanoscale features after lasing. Compared to the control PES membrane, the membrane fabricated with 8% laser power on the bottom layer of PES (PES (B)-LIG-HP) demonstrated 4 times higher flux (865 LMH) and 90.9% bovine serum albumin (BSA) rejection. Moreover, LIG membranes were found to be highly hydrophilic and exhibited excellent mechanical and chemical stability. Owing to their excellent permeance and separation efficiency, these highly robust electroconductive LIG membranes have a great potential to be used for designing functional membranes.

PES mixed-matrix membranes incorporating ZIF-8@MXene nanocomposite for the efficient dye/salt separation

To improve the flux, anti-fouling and dye separation performance of PES-based membranes, PES mixed-matrix membranes (MMMs) blended with ZIF-8@Ti3C2Tx composites were fabricated via a facile one-pot microemulsion strategy. The introduction of hydrophilic components in the microemulsion into the PES matrix enhanced the pore structures and surface polarity of the resulting MMMs, causing them to exhibit high permeation and anti-fouling performance compared to both neat PES and MMMs with ZIF-8. The optimal membrane flux and anti-fouling performance were found to be 280 L·m−2·h−1 and 91 % (bovine serum albumin rejection), respectively, at 3 % microemulsion content. The well-distributed ZIF-8@Ti3C2Tx composites in the MMMs interact with dye molecules, which strengthens the dye retention from high-salinity wastewater. Further, the pore size of the MMMs was positively correlated with the flux but negatively correlated with dye retention. In particular, the M-3 membrane exhibited high flux (140 L·m−2·h−1) and up to 98 % dye rejection in high-salinity wastewater, but its rejection of salt ions was <5 %. In addition, the dye rejection recovery rate of M-3 after each washing exceeded 93 % over 5 fouling/backwashing cycles. These results strongly suggest that MMMs incorporated with ZIF-8@Ti3C2Tx composites have promising application prospects for removing trace dye pollutants from high-salinity wastewater.

Environmental Friendly Fabrication of Porous Cement Membranes via Reusable Camphene-Based Freeze-Casting Method.

Inorganic membranes have been developed rapidly in recent years because of excellent anti-fouling performance, high mechanical strength and outstanding resistances to acid and alkali. However, the high production cost still restricts its large-scale industrial application. In this work, an environmental friendly unidirectional freezing method via introducing camphene as a reusable template was adapted to prepare porous cement membranes (PCMs). The naturally formed and highly aligned porous structures of PCMs could be divided into three parts: a dense layer, a transition layer and a supporting layer. With the solid content rising from 40 wt.% to 60 wt.%, the pore size of the PCMs decreased from 3.34 nm to 3.62 nm, the bovine serum albumin (BSA) rejection increased from 81.3% to 93.5% and water flux decreased from 346.8 L·m−2·h−1 to 167.3 L·m−2·h−1 (0.2 MPa). Significantly, the performance of PCMs was maintained; even the camphene was reused 20 times. Additionally, the recovery rate of camphene could be reached up to 97.16%. Therefore, this method is cost effective and environmental friendly, which endowed the PCMs great potential in water treatment.

Investigation of antifouling and antibacterial properties of curcumin-enriched surfactant nanoparticles modified polysulfone nanocomposite membranes

Membrane fouling is the major hindrance to the extensive application of membrane-based treatment techniques. In this study, we synthesized the antibacterial membranes with varying wt.% (1–5) of curcumin-enriched sodium dodecyl benzenesulfonate (Cur-NaDBS) nanoparticles in the polysulfone polymer matrix. The membranes were characterized by scanning electron microscope (SEM), thermogravimetric analysis, Fourier transformation spectroscopy (FT-IR) and the nanoparticles were characterized by X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). 1H and 13C NMR confirmed the successful synthesis of Cur-NaDBS nanoparticles. The M-CN5 (PSF+5 wt% Cur-NaDBS) exhibited higher average surface roughness (133 nm) than the pristine polysulfone (M-P0) membrane (average surface roughness: 65 nm). The pure water permeation for the mixed matrix membrane M-CN5 was 3.2 times that of the pristine M-P0 membrane. The Cur-NaDBS incorporated membranes exhibited better bovine serum albumin (BSA) rejection performance than the pristine M-P0 (pristine PSF) membrane. The Cur-NaDBS nanoparticles incorporated membranes showed a high flux recovery rate (>90%). Moreover, incorporating Cur-NaDBS nanoparticles into the polysulfone matrix imparted antibacterial properties to the membranes. This was confirmed by disk diffusion test and molecular docking studies (binding energy = −7.06 kJ mol−1) with the gram-positive S. aureus bacteria. This study found that Cur-NaDBS nanoparticles incorporated membranes mitigate the fouling problems for ultrafiltration applications.

Microstructures and properties of PVDF membranes: effect of the solvent

The polyvinylidene fluoride (PVDF) membranes were synthesized using immersion precipitation technique. The effect of four solvents, N, N-dimethyl formamide (DMF), N, N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO) on the water flux and beef serum albumin (BSA) rejection efficiency was reported. The structure and morphology of PVDF membranes were studied using Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and water contact angle measurements. The cross-section of a membrane formed in a DMF as a solvent exhibit a spongy/fingerlike hybrid structure, while DMSO favors the formation of more porous structure. The increase in the solvent mass fraction facilitates liquid phase separation and solution casting, and changes the structure of PVDF membrane from denser, bicontinuous structure to a looser, stacked structure. Moreover, the results revealed that the properties of PVDF membranes sub-layer are controlled by the diffusion rate of the nonsolvent. The membrane with the best performance was prepared using 80% DMF (mass fraction) as a solvent, and it reached water flux of 66 L·m−2·h−1, and 91.53% BSA rejection efficiency.

Development of High Flux Nanocomposite Polyphenylsulfone/Oxidized Multiwalled Carbon Nanotubes Membranes for Ultrafiltration Using the Systems with Critical Solution Temperatures.

The study deals with the investigation of the effect of the modification of polyphenylsulfone (PPSU) flat sheet membranes for ultrafiltration using oxidized multiwalled carbon nanotubes (O-MWCNT) in order to enhance membrane permeability and antifouling performance. The effect of O-MWCNT loading to the PPSU-polyethylene glycol (PEG-20,000, Mn = 20,000 g·mol−1)-polyvinylpyrrolidone (PVP K-30, Mn = 40,000 g·mol−1)-N-methy-2-pyrrolidinone (NMP) colloid systems on the phase state and viscosity was studied. It was found that PPSU-PEG-20,000-PVP K-30-O-MWCNT-NMP colloid systems feature a gel point (T = 35–37 °C) and demixing temperature (T = 127–129 °C) at which two bulk phases are formed and a polymer system delaminates. According to the study of the phase state and viscosity of these colloid systems, a method for the preparation of high flux PPSU membranes is proposed which includes processing of the casting solution at the temperature higher than gel point (40 °C) and using a coagulation bath temperature lower than gel point (25 °C) or lower than demixing temperature (40 °C and 70 °C). Membrane structure, topology and hydrophilic-hydrophobic balance were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. The effect of coagulation bath temperature and O-MWCNT concentration on the membrane separation and antifouling performance in ultrafiltration of human serum albumin and humic acids solutions was studied. It was found that the modification of PPSU ultrafiltration membranes by O-MWCNTs yielded the formation of a thinner selective layer and hydrophilization of the membrane surface (water contact angle decreased from 53–56° for the reference PPSU membrane down to 33° for the nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT). These changes resulted in the increase in membrane flux (from 203–605 L·m−2·h−1 at transmembrane pressure of 0.1 MPa for the reference membrane up to 512–983 L·m−2·h−1 for nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT depending on coagulation bath temperature) which significantly surpasses the performance of PPSU ultrafiltration membranes reported to date while maintaining a high level of human serum albumin rejection (83–92%). It was revealed that nanocomposite membrane demonstrated better antifouling performance (the flux recovery ratio increased from 47% for the reference PPSU membrane up to 62% for the nanocomposite membrane) and higher total organic carbon removal compared to the reference PPSU membrane in humic acids solution ultrafiltration.

Tailoring nanofiltration membrane surface using modified styrene-maleic anhydride for water purification

Nanofiltration membranes were prepared using modified styrene-maleic anhydride (SMA) blending with amphiphilic polyvinyl chloride (APVC). The membranes morphology were studied by electron microscopy scanning (SEM), and characterized by different analyses. Increasing in SMA concentration in polymeric solution during preparation to 0.8 wt% improves the mechanical strength to be 40.5 MPa, the membrane performance enhanced, where the bovine serum albumin (BSA) rejection reached 99.9% with permeate flux of 47 L/m2⋅h. The fouling test was applied on membranes, The flux recovery ratio (FRR) of the prepared membrane with 0.8 wt% addition of SMA reached 98.3%, while irreversible resistance (Rir) reduced to 6.3% compared to the blank APVC membrane and reversible resistance (Rr) reduced to 13.3%. The segregation of amphiphilic polymer inside the membrane backbone enhances the antifouling properties due to improving the hydrophilicity of the surface.

PES membrane surface modification via layer-by-layer self-assembly of GO@TiO2 for improved photocatalytic performance

We herein report novel polyethersulfone/graphene oxide@titanium dioxide (PES/GO@TiO2) photocatalytic membranes developed via the layer-by-layer (LBL) self-assembly technique. The synergistic coupling of GO and TiO2 could result in improved photocatalytic activity and endow the pristine PES membrane with photocatalytic function. Various techniques were adopted to characterize the structure and morphology of PES/GO@TiO2 photocatalytic membranes, which indicated that GO@TiO2 was successfully integrated in PES. Contact angle testing proved that the hydrophilicity of PES/GO@TiO2 photocatalytic membranes was improved with the increase of self-assembled GO@TiO2 layers. FTIR results indicated that GO@TiO2 was attached to the pristine PES membrane surface through interfacial interactions in our experimental conditions. And both the thermal stability and mechanical stability of the pristine PES membrane were improved with the incorporation of GO@TiO2. Meanwhile, the optimized PES/GO@TiO2 photocatalytic membranes exhibited a water flux up to 109.8 L/(m2 h), more than 4 times that of pristine PES membrane, while kept high bovine serum albumin (BSA) rejection of 99.1%, and flux recovery ratio (FRR) of 86.1% in dark condition and the flux almost tripled after about 3 h of UV irradiation. Specially, the photocatalytic activity of PES/GO@TiO2 photocatalytic membranes increased with an increase of self-assembled GO@TiO2 layers. When the self-assembled layers of GO@TiO2 were three, the membrane showed 95.1% of degradation against methylene blue (MB) dye under UV light irradiation. Thus, the prepared PES/GO@TiO2 photocatalytic membranes can be suggested as an ideal candidate for photocatalytic templates in wastewater treatment.

Covalent organic framework‐poly(acrylic acid)‐modified poly(vinylidene fluoride) ultrafiltration membranes towards enhanced antifouling properties and low hydrophilic material leaching

AbstractThe hydrophilicity is acknowledged critically to raise anti‐fouling of membranes conferring a leaching problem over a prolonged operation. To decrease the leaching of hydrophilic material in modified membranes, poly(vinylidene fluoride) (PVDF) ultrafiltration membranes is herein presented using covalent organic framework (COF)‐poly(acrylic acid) (PAA) modifier via PAA‐catalyzed in‐situ COF synthesis method. The modified PVDF membrane with an optimized COF‐PAA content showed higher water flux (95 L/m2 h), greater bovine serum albumin rejection, and superior antifouling properties to sodium alginate (95% FRR values). The stability test conducted on COF‐PAA‐modified PVDF membrane gave a lower leaching rate of PAA than that of the PAA‐modified counterpart. The membrane containing COF‐PAA compared with the COF‐free counterpart showed a smaller water contact angle down to 55°. The morphologies of the COF‐modified membranes and the COF‐free counterpart studied with scanning electron microscope found that the COF in tight bonding to PAA was homogeneously bonded to the membrane surface. The surface modification contributes to greater stability and anti‐fouling properties of the membrane. The enhanced properties can associate with the reduced pore size of PVDF membrane via in‐situ COF synthesis using the catalyst PAA. This work provides a novel strategy towards the further development of efficient composite membranes with enhanced antifouling properties and water flux.

Metal–organic framework ZnL–PVDF supramolecular ultrafiltration membrane for enhanced separation performance

Using an in-situ chemical blending method, ZnL–polyvinylidene fluoride (PVDF) supramolecular ultrafiltration (UF) membranes were fabricated to solve the problem of agglomeration of metal–organic frameworks (MOFs) in MOF/polymer UF membranes. In this process, the MOF material, ZnL, was directly synthesised during preparation of the PVDF casting solution and ZnL–PVDF supramolecular membranes were fabricated by phase inversion. With the increase of ZnL, the pure water flux of the membrane initially increased sharply and then decreased slowly, accompanied by an almost identical trend in bovine serum albumin (BSA) rejection. In particular, the fabricated membrane (with ZnL content of 15 wt%) possessed a water flux up to 271.8 L m−2 h−1 bar−1, nearly six times that of the pristine PVDF membrane, and high BSA rejection of 96.5%. These results indicate that the facile in-situ chemical blending method is promising for fabricating uniform and highly hydrophilic MOF/polymer UF membranes.

Fabrication, characterization, and performance of poly (aryl ether nitrile) flat sheet ultrafiltration membranes with polyvinyl pyrrolidone as additives

Abstract Poly(aryl ether nitrile) (PEN) was used to fabricate ultrafiltration membrane via immersion precipitation phase inversion method. The effects of polyvinyl pyrrolidone (PVP) of different molecular weights and concentrations on the structure and performance of PEN membranes were investigated. The membranes were observed by scanning electron microscope, atomic force microscope, equilibrium water content (EWC), porosity (ε), and so on. The membranes were subjected to ultrafiltration characterizations such as pure water flux (PWF), compaction factor (CF), hydraulic permeability (P m), and bovine serum albumin (BSA) rejection rate. The hydrophilicity was characterized by infrared spectroscopy and contact angle tests. Results showed that molecular weight of PVP had significant effect on PEN membrane formation, which the membrane prepared by PVP-k30 exhibited excellent comprehensive performance. Meanwhile, the concentration of PVP-k30 could effectively control the select-permeability of PEN membrane. With PVP-k30 concentration increased from 7 to 13 wt%, the prepared PEN membranes got higher EWC, ε, CF, and P m. The PWF increased from 146.5 to 249.1 L m−2 h−1 bar−1, while the overall rejection of BSA remained above 90%. Further increasing the addition amount to 16 wt%, the membrane performance began to decline. Finally, the addition of PVP-k30 could effectively improve the hydrophilicity of prepared PEN membrane surface.

A novel temperature-responsive mixed matrix ultrafiltration membrane based on boron nitride nanomaterial

A novel mixed matrix membrane was prepared by blending polysulfone with two-dimensional boron nitride followed by its hydroxyl functionalization. Prepared nanocomposite membranes were characterized for the surface morphology, surface roughness, zeta potential and hydrophilicity. Uniform dispersion of boron nitride nanoparticles in polysulfone matrix and consequent changes in membrane properties were confirmed by scanning electron microscope images, atomic force microscope images, zeta potential, contact angle analysis, and X-Ray photoelectron spectroscopy. Differential scanning calorimetry (DSC) technique was used to determine the glass transition temperature (Tg) of the modified membrane and the results revealed the presence of BN in the membrane matrix. The highest water flux of 329.52 Liters per sqm per hour (LMH) was obtained in case of PS/BN (1%) as compared to 151.87 LMH of virgin membrane and Albumin rejection also increased by nanocomposites membranes up to certain concentration of Boron nitride. A unique behavior of temperature responsiveness of nanocomposite membrane was observed, where a steep increment in permeate flux by 205% at higher temperature was noted as compared to the virgin Polysulfone membrane where only 103% increase was recorded for the same temperature range. Moreover, the water uptake capacity of nanocomposite membranes were measured to understand the changes with nanomaterial incorporation. The membrane showed a good promise for high-temperature separation applications.

Graphene Oxide Modified Polyamide 66 Ultrafiltration Membranes with Enhanced Anti-Fouling Performance.

Improving the contamination resistance of membranes is one of the most effective ways to address the short service life of membranes. While preparing the membrane system structure, doping nanoparticles into the polymer matrix is beneficial to the preparation of high-performance membranes. To develop a new structure for membrane contamination protection, in this study, a novel asymmetric polyamide 66 composite ultrafiltration (UF) membrane was fabricated by incorporating different masses (ranging from zero to 0.5 wt.%) of graphene oxide (GO) into the polyamide 66 microporous substrate, using formic acid and propylene carbonate as solvents. The effects of GO doping on the morphology, microporous structure and surface of ultrafiltration membranes were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), integrated thermal analysis (DSC) and contact angle (CA). In addition, pure water flux, bovine serum albumin (BSA) rejection and contamination resistance were measured to evaluate the filtration performance of different membranes. The overall performance of all the modified membranes was improved compared to pure membranes. The results of contact angle and permeation experiments showed that the addition of GO improved the hydrophilicity of the membrane, but reduced the permeability of the membrane. The minimum flux was only 3.5 L/m2·h, but the rejection rate was 92.5%. Most noteworthy was the fact that GO further enhanced the anti-pollution performance of the membranes and achieved a remarkable performance of 91.32% when the GO content was 0.5 wt.%, which was 1.36 times higher than that of the pure membrane. Therefore, optimal performance was achieved. Furthermore, the UF membrane made of composite substrate offers a promising solution for the development of long-life ultrafiltration membranes with better stability, high-cost efficiency and adequate chemical durability.

Antifouling polysulfone membranes with an amphiphilic triblock additive

Triblock amphiphilic oligomers polydiol terephthalate polyvinylpyrrolidone (PDT-(PVP)2) were synthesized as the additive for the preparation of antifouling polysulfone (PSf) membranes. The influences of oligomer contents on membrane properties such as wettability, morphology, porosity, antifouling, etc were investigated. Among the synthesized oligomers, the one with the medium hydrophobic chain length at a blending percentage of 1.5% exhibited better filtration/antifouling performances. The contact angle of the blend membrane can reach as low as 60.3°. The water permeation of the blend membrane was increased from 85.1 L/(m2h) for the pristine PSf membrane to a maximum of 210.0 L/(m2h) for the blend membrane. All three oligomer blended membranes can achieve a bovine serum albumin rejection ratio of over 95.0%. The minimum amount of protein adsorbed on the blend membrane is ∼9.73 μg/cm2. Moreover, the flux recovery ratio of the blend membranes is remarkably higher than that of the pristine membrane. Surface atomic content and water contact angle measurements suggested that the amphiphilic oligomers migrated to the surface of the membrane during membrane formation process, and microstructure photographs of the membranes indicated that the amphiphilic oligomer accelerated the pore formation speed, all of which correlated well with the filtration and antifouling results. Moreover, there is no obvious deviation of water contact angles on the membrane surfaces before and after treatment in boiling water, which means that the amphiphilic oligomers were hardly washed off from the membrane, thus, the as-prepared amphiphilic PDT-(PVP)2 oligomers are able to exhibit sustainable antifouling ability.

Dual-layer hollow fibre haemodialysis membrane for effective uremic toxins removal with minimal blood-bacteria contamination

Bacterial endotoxin contamination in dialysate may pass through haemodialysis membrane and cause a silent chronic microinflammation to kidney patients. Dual-layer hollow fibre (DLHF) membranes with dual function, biocompatible adsorptive and antibacterial effects were developed to solve the problem of incompatible membrane and endotoxin contamination. All membranes were fabricated via the co-extrusion dry-wet phase inversion technique. In this study, silica/α-mangostin nanoparticle was incorporated into the inner layer of membrane to enhance the biocompatibility of the membrane while maintaining its adsorption capacity. Activated carbon (AC) was incorporated in the outer layer of membrane for improved antibacterial property. The DLHF membranes were characterised based on its morphology and surface hydrophilicity. The performance of the DLHF membranes was evaluated in terms of permeability, urea, and creatinine removal capabilities, bovine serum albumin (BSA) rejection and antibacterial properties. The dense and small pore size on the outer layer of AC created a smoother surface for the DLHF membrane. The BSA rejection of the DLHF membranes was enhanced by 6–8% compared to that of unmodified single layer hollow fibre membrane. Silica/α-mangostin nanoparticle in the inner layer of membrane enhanced the removal of urea and creatinine by chemisorption. Result also showed that the incorporation of AC in the outer layer of DLHF membrane successfully filtered bacteria by bacteria entrapment. DLHF membrane with the combination of silica/α-mangostin nanoparticle in the inner layer and AC in the outer layer possessed the higher bacteria inhibition into blood compartment against Escherichia coli and Staphylococcus aureus, with removal rate of 68% and 75%, respectively, and better urea and creatinine removal by 60.57% and 75.18%, respectively, compared to single-layer PSf based membrane. The development of co-adsorptive biocompatible DLHF membrane can play an important role in improvement of kidney patient life.

Nitrogenated Graphene Oxide-Decorated Metal Sulfides for Better Antifouling and Dye Removal.

Nitrogenated graphene oxide-decorated copper sulfide nanocomposites (CuxS-NrGO, where x = 1 and 2) are designed to be incorporated in polysulfone (PSF) membranes for effective fouling resistance of PSF membranes and their dye removal capacity. The developed membranes possess more hydrophilicity and an enhancement in pure water flux (PWF). Also, the highest bovine serum albumin (BSA) rejection of 89% was observed when compared to membranes with pristine PSF (5 L/m2 h PWF and 88% BSA rejection) and CuS-incorporated PSF membranes (14 L/m2 h PWF and 83% BSA rejection) because of N doping and enhanced permeability. It is also found that the CuxS-NrGO-incorporated PSF membranes exhibited a significantly higher fouling resistance, a larger permeate flux recovery ratio (FRR) of nearly 82%, and a congo red dye rejection of 93%. CuxS-NrGO nanoparticles thus demonstrate the potential efficacy of enhancing the hydrophilicity, leading to a better flux, dye removal capacity, and antifouling capacity with a very high FRR value of 82% because of a strong interaction between the N-active sites of the NrGO, CuxS, and polysulfone matrix, and negligible leaching of nanoparticles is observed.

Study on two‐stage stretching strategy for microstructure improvement of polytetrafluoroethylene hollow fiber membrane

AbstractPolytetrafluoroethylene (PTFE) has excellent chemical resistance, thermal stability as well as hydrophobicity, and is regarded as a good material for membrane fabrication. PTFE hollow fiber membrane is commonly prepared by the paste extrusion–stretching–sintering process, where the stretching temperature is usually fixed in existing reports. In this paper, a new two‐stage stretching method (first at 50°C and then at 200°C) was proposed to optimize the microstructure of PTFE hollow fiber membranes. Meanwhile, the stretching experiments at low‐temperature (50°C) and high‐temperature (200°C) were also conducted for comparison. The chemical composition, surface morphology, surface porosity, overall porosity, maximum pore size, water contact angle, and mechanical property were discussed. Moreover, the ethanol permeation flux and bovine serum albumin (BSA) rejection of PTFE hollow fiber membranes prepared from different stretching manners were tested. The results showed that with the increase of stretching ratio, the porosity, and pore size gradually increased for all three membranes. However, for a specific stretching ratio, the membrane fabricated by two‐stage stretching process exhibited better comprehensive properties in terms of porosity and pore size, that is, higher porosity than the 50°C method and smaller pore size than the 200°C method. As stretching ratio was 2.0, the ethanol permeation flux and BSA rejection was 2467 L/m2 h and 95%, respectively. Overall, the PTFE hollow fiber prepared from “two‐stage” stretching exhibited comparable BSA rejection (both around 95%) and much higher permeation flux (increased by 43.1%) compared to the sample prepared by low‐temperature stretching at 50°C, and meanwhile, comparable permeation flux (decreased by 10.8%) and higher BSA rejection (95% against 81%) compared to the sample prepared by high‐temperature stretching at 200°C. The proposed method provided a good reference for the microstructure improvement of PTFE hollow fiber membrane fabricated by paste extrusion–stretching–sintering technology.