Filtration Of Bovine Serum Albumin Solution Research Articles

Fabrication of ultrafiltration membranes with improved antifouling and antibacterial capability by surface modification of quaternary ammonium

To minimize the organic/biological contamination, polymeric membranes with tertiary amine groups were synthesized and its surface was modified to obtain three types of quaternary ammonium modified ultrafilters. The antifouling and antibacterial properties of all prepared ultrafilters were studied. The performances differences of ultrafiltration membranes with different alkyl chain lengths of quaternary ammonium salts were explored. The results show that the increase of alkyl chain length of quaternary ammonium salts and the introduction of hydroxyl groups can effectively improve the permeability and anti-pollution performance of ultrafiltration membranes. After one cycle of Bovine serum albumin solution filtration test, the flux recovery ratio of the modified membrane is twice as much as that of the initial membrane, while the flux recovery ratio of the initial ultrafiltration membrane is only 36.6%. At the same time, the modified membrane has excellent antibacterial properties and water flux stability, which is conducive to the long-term use of the membrane.

Synthesis and characterization of novel zwitterionic poly(aryl ether oxadiazole) for antifouling ultrafiltration membrane

Zwitterionic polymers have attracted widespread attention and are recognized as ideal materials in various potential applications of membrane-based separation due to its superior hydrophilicity and excellent antifouling properties. Therefore, a new type of bisphenol monomer with two tertiary amine groups named 2,2'-dimethylaminemethylene-4,4'-dihydroxydiphenylmethane (DABPM) was particularly designed and prepared. Then, the novel poly(aryl ether oxadiazole) (ZPAEO) was synthesized by low-temperature polycondensation and quaternary amination reaction. The chemical structures of the synthetic monomer and polymers were characterized by MS NMR and XPS analysis, and the inherent viscosities, molecular weights and solubility behaviors of the obtained polymers were also thoroughly studied. Subsequently, the ZPAEO membrane was fabricated by through the immersion precipitation phase inversion method. Compared with the reference PAEO membrane, the pore size, porosity and hydrophilicity of the ZPAEO membrane were greatly improved because of the existence of zwitterionic groups, resulting in a significant increase in the water permeability. The results of static adsorption and dynamic cycle ultrafiltration experiments of bovine serum albumin (BSA) solution showed that the ZPAEO membrane had excellent antifouling performance, which was demonstrated by the flux decline ratio. In addition, water flux recovery ratio of the ZPAEO membrane was retained at 97.7% after a three-cycles of BSA solution filtration, which was much higher than that of the PAEO membrane (81.2%), indicating superior long-term performance stability. As a membrane material, ZPAEO is expected to be widely used in various industrial separation and purification fields, which can be demonstrated by these findings.

Fabrication of anti‐fouling thin‐film composite reverse osmosis membrane via constructing heterogeneous wettability surface

AbstractAnti‐fouling properties are tightly related to the surface properties of reverse osmosis (RO) membranes. In our study, fluorinated polyethyleneimine (FPEI) was synthesized by introducing perfluoroalkyl groups into a hydrophilic polyethyleneimine (PEI) matrix, and the heterogeneous wettability surface with hydrophilic and low‐surface‐energy properties was constructed by grafting FPEI on membrane surface via the carbodiimide‐induced method. Verified by the result analysis of SEM, AFM, and zeta potentials measurements, the fluorinated RO membrane surface presented denser, smoother, and reduced negative charge. The surface free energy of RO membrane surface after grafting FPEI decreased from 45.5 to 38.7 mJ/m2. By using bovine serum albumin (BSA), humic acid (HA), and dodecyltrimethyl ammonium bromide (DTAB) as model foulants, the fluorinated RO membrane exhibits optimal fouling resistance and fouling release properties compared to pristine membrane and membrane modified by surface grafting hydrophilic PEI. Especially, the high recovery ratio (99%) and low total flux decline ratio (17.2%) were acquired during the filtration of BSA solution. These results manifested that the construction of a heterogeneous wettability surface can further improve the anti‐fouling properties of RO membranes compared to a pure hydrophilic surface, and the corresponding anti‐fouling mechanism was put forward.

Preparation and Characterization of Polyvinylpyrrolidone/Polysulfone Ultrafiltration Membrane Modified by Graphene Oxide and Titanium Dioxide for Enhancing Hydrophilicity and Antifouling Properties

Ultrafiltration membranes are fabricated using graphene oxide/titanium dioxide (GO/TiO2, with weigh ratios of 30/70, 50/50 and 70/30), polyvinylpyrrolidone (PVP) and polysulfone (PSf) by phase inversion method and characterized using X-ray diffraction, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy; morphology and structure of prepared membranes are examined by transmission electron microscopy and SEM and energy dispersive X-ray analysis. PSf blend membranes containing 0.75 wt% of the nanocomposites are fabricated wherein PVP with the high hydrophilic property are used in casting solution as a pore former. Comparative separation performance and antifouling properties of ensuing nanocomposites are investigated in multiple analyses such as water contact angle measurement, pure water flux, bovine serum albumin solution filtration, and fouling resistance. Because of PVP and GO/TiO2 nanocomposites addition to the polymer matrix, membrane surface hydrophilicity increased which led to improvement in the membrane performances. GO/TiO2 (50/50)–PVP/PSf membrane exhibited the best result; contact angle decreased from 75°, pure water flux increased to 496.2 L/m2 h. The percentage of rejection and flux recovery ratio increased to 96.6% and 75.8%, respectively.

Assembly of self-cleaning perfluoroalkyl coating on separation membrane surface

Most membrane-based separation technologies for water treatment are severely limited by fouling-induced flux decline. Herein, a self-cleaning coating with weak chargeability was achieved by assembly of perfluorooctane sulfonate (PFOS) and polyethyleneimine (PEI) on hydrolyzed polyacrylonitrile (HPAN) membrane. The -NH3+ endowed the membrane with hydrophilicity, thus introducing fouling-resistance property. The -CFX in the coating endowed the ultrafiltration membrane with low surface energy (23.3 mJ/m2), thus introducing fouling-release property. Besides, a weakly-charged surface (8.4 mV) was obtained by the charge counteract between -SO3− on PFOS and -NH3+ on PEI, which further intensified the fouling-release property. The resultant membrane with such a self-cleaning coating exhibited superior antifouling property during oil/water emulsion and bovine serum albumin solution filtration. This facile assembly method may open up a new avenue towards engineering antifouling membrane surface for efficient water treatment.

Improved antifouling performance of ultrafiltration membrane via preparing novel zwitterionic polyimide

On the basis of the outstanding fouling resistance of zwitterionic polymers, an antifouling ultrafiltration membrane was fabricated through phase inversion induced by immersion precipitation method, directly using the novel zwitterionic polyimide (Z-PI), which was synthesized via a two-step procedure including polycondensation and quaternary amination reaction, as membrane material. The chemical structure and composition of the obtained polymer were confirmed by using FTIR, 1H NMR and XPS analysis, and its thermal stability was thoroughly characterized by TGA measurement, respectively. The introduction of zwitterionic groups into polyimide could effectively increase membrane pore size, porosity and wettability, and convert the membrane surface from hydrophobic to highly hydrophilic. As a result, Z-PI membrane displayed significantly improved water permeability compared with that of the reference polyimide (R-PI) membrane without having an obvious compromise in protein rejection. According to the static adsorption and dynamic cycle ultrafiltration experiments of bovine serum albumin (BSA) solution, Z-PI membrane exhibited better fouling resistant ability, especially irreversible fouling resistant ability, suggesting superior antifouling property and long-term performance stability. Moreover, Z-PI membrane had a water flux recovery ratio of 93.7% after three cycle of BSA solution filtration, whereas only about 68.5% was obtained for the control R-PI membrane. These findings demonstrated the advantages of Z-PI membrane material and aimed to provide a facile and scalable method for the large-scale preparation of low fouling ultrafiltration membranes for potential applications.

Ultrafiltration performance and fouling resistance of PVB/SPES blend membranes with different degree of sulfonation

Abstract

Engineering a Highly Hydrophilic PVDF Membrane via Binding TiO₂Nanoparticles and a PVA Layer onto a Membrane Surface.

A highly hydrophilic PVDF membrane was fabricated through chemically binding TiO2 nanoparticles and a poly(vinyl alcohol) (PVA) layer onto a membrane surface simultaneously. The chemical composition of the modified membrane surface was determined by X-ray photoelectron spectroscopy, and the binding performance of TiO2 nanoparticles and the PVA layer was investigated by a rinsing test. The results indicated that the TiO2 nanoparticles were uniformly and strongly tailored onto the membrane surface, while the PVA layer was firmly attached onto the surface of TiO2 nanoparticles and the membrane by adsorption-cross-linking. The possible mechanisms during the modification process and filtration performance, i.e., water permeability and bovine serum albumin (BSA) rejection, were investigated as well. Furthermore, antifouling property was discussed through multicycles of BSA solution filtration tests, where the flux recovery ratio was significantly increased from 20.0% for pristine PVDF membrane to 80.5% for PVDF/TiO2/PVA-modified membrane. This remarkable promotion is mainly ascribed to the improvement of surface hydrophilicity, where the water contact angle of the membrane surface was decreased from 84° for pristine membrane to 24° for PVDF/TiO2/PVA membrane. This study presents a novel and varied strategy for immobilization of nanoparticles and PVA layer on substrate surface, which could be easily adapted for a variety of materials for surface modification.

Preparation and properties of nanocomposite polysulfone/multi-walled carbon nanotubes membranes for desalination

Novel nanocomposite membranes for application in desalination were fabricated from polysulfone (PSf) and multi-walled carbon nanotubes (MWNTs) functionalized with dodecylamine (DDA) and anti-fouling properties of the membranes were studied during filtration of bovine serum albumin (BSA) solutions. Phase inversion process with dimethylacetamide as solvent and polyvinylpyrrolidone as a porogen was used to prepare flat sheet nanocomposite PSf/DDA-MWNTs membranes. Before embedding MWNTs in the polymer matrix, they were treated with HNO3 for the introduction of carboxylic groups on nanotube surface and then modified with DDA. The prepared DDA-MWNTs were characterized using scanning electron microscope, infrared spectroscopy and thermal gravimetric analysis. The long alkyl chains of DDA functionalized MWNTs seem to enhance the interfacial adhesion and compatibility between inorganic nanotubes and PSf matrix. The changes in surface hydrophilicity, morphology and roughness of fabricated nanocomposite membranes as a function of DDA-MWNTs loading were evaluated by using contact angle goniometry and atomic force microscopy. The prepared nanocomposite membranes possessed significantly higher permeability with improved protein fouling resistance than the pristine PSf membrane during filtration of BSA solutions. The membrane prepared with 0.5wt.% loading of DDA-MWNTs displayed the highest flux recovery (83%) and lowest total flux loss (29%) with reduced irreversible fouling resistance (17%).

Effects of Coagulation-Bath Temperature And Montmorillonite Nanoclay Content on Asymmetric Cellulose Acetate Butyrate Membranes

AbstractA major problem with polymeric membranes is low hydrophilicity and consequently a tendency to fouling. Preparing composite membranes is one way to improve the properties and performance of the neat membrane. In the present study, the effects of coagulation-bath temperature (CBT) and the hydrophilic nanoclay concentration of montmorillonite (MMT) on the morphology and performance of asymmetric cellulose acetate butyrate (CAB) membranes were investigated. The membranes were prepared via phase inversion induced by immersion precipitation in a water-coagulation bath. The morphology of the membranes prepared was studied by scanning electron microscopy (SEM). The permeation performance of the membranes prepared was studied by experiments using pure water and bovine serum albumin (BSA) solutions as feeds. The results showed that the membrane thickness and pure water flux (PWF) were increased by adding up to 2 wt.% MMT nanoclay to the casting solution. These two parameters decreased with further addition of MMT, however. In addition, the results obtained in the case of filtration of BSA solution indicated that the addition of MMT in the casting solution increased permeate flux and reduced BSA rejection slightly. Furthermore, increasing the MMT nanoclay concentration in the casting solution increased pure water flux recovery and consequently decreased the fouling. Decreasing the CBT in the presence of MMT during membrane preparation resulted in the formation of a more porous structure and consequently increased the flux and simultaneously decreased the BSA rejection.

Preparation and antibacterial property of PES/AgNO3 three-bore hollow fiber ultrafiltration membranes

In this study, a three-bore polyethersulfone (PES) hollow fiber ultrafiltration (UF) membrane with antibacterial properties was prepared by phase inversion, using PES as the membrane material, N,N-dimethylacetamide (DMAC) as solvent, polyvinylpyrrolidone (PVP) and AgNO3 as additives. The silver particles were detected by X-ray photoelectron spectroscopy. The effect of AgNO3 content on the antibacterial properties and separation performance was studied in detail. The membranes showed good antibacterial activity against Escherichia coli after adding AgNO3 and the antibacterial rate of PES/AgNO3 UF membrane with AgNO3 content of 1 wt% could reach 99.9% after running for 48 hours. Moreover, the bovine serum albumin solution filtration results indicated that the PES/AgNO3 membranes had a certain degree of antifouling performance. Therefore, three-bore PES/AgNO3 membranes have a potential application to reduce both bacterial and organic fouling in water treatment.

Performance improvement of polysulfone ultrafiltration membrane by blending with polyaniline nanofibers

Polyaniline (PANI) nanofibers were used to improve hydrophilic property and permeability of polysulfone (PS) membrane. PS membrane and PS/PANI nanofibers blended membranes with different PANI–PS mass ratios (1, 5, 10, and 15 wt.%) were prepared by phase inversion process. The blended membranes showed similar bovine serum albumin (BSA) and albumin egg (AE) rejections to PS membrane. The blended membranes had larger porosity and better hydrophilic property than PS membrane, which caused the improvement of their permeability. Pure water fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 1.6 and 2.4 times that of PS membrane, respectively. During the filtration of BSA solution, the blended membranes had slower flux decline rate than PS membrane. Moreover, stable permeate fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 2.0 and 2.5 times that of PS membrane, respectively. Compared with PS membrane, mechanical property and thermal stability of the blended membranes with less PANI–PS mass ratio, e.g. 1 wt.%, had no obvious change. For the blended membrane with PANI–PS mass ratio of 15 wt.%, breaking strength increased 28% and elongation at break decreased 30.6%.

Asymmetric membranes fabricated from poly(acrylonitrile-co-N-vinyl-2-pyrrolidone)s with excellent biocompatibility

Poly(acrylonitrile-co-N -vinyl-2-pyrrolidone)s (PANCNVPs) show excellent biocompatibility. In this work, PANCNVPs with different contents of N-vinyl-2-pyrrolidone (NVP) were fabricated into asymmetric membranes by the phase inversion method. The surface chemical composition of the resultant membranes was determined by Fourier transform infrared spectroscopy–attenuated total reflection. Field emission scanning electron microscopy was used to examine the surface and cross section morphologies of the membranes. It was found that the morphologies hardly change with the increase of NVP content in PANCNVP, while the deionized water flux increases remarkably and the bovine serum albumin (BSA) retention decreases slightly. Experiment of dynamic BSA solution filtration was carried out to evaluate the antifouling properties of the studied membranes. The relative flux reduction of PANCNVP membrane containing 30.9 wt % of NVP is 25.9%, which is far smaller than that of the polyacrylonitrile membrane (68.8%). Results deduce that this improvement comes from the excellent biocompatibility of NVP moieties instead of the hydrophilicity change, because the water contact angles of these membranes fluctuate between 60 and 70°. Results from the membranes using poly(N-vinyl-2-pyrrolidone) (PVP) as an additive confirm that, to a certain extent, the PANCNVP membranes show the advantages of antifouling compared with the polyacrylonitrile/PVP blending membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4577–4583, 2006

Microfiltration of protein-cell mixtures with crossflushing or backflushing

Crossflow microfiltration experiments were performed with and without crossflushing or backflushing using yeast suspensions, bovine serum albumin (BSA) solutions, and mixtures of yeast and BSA. Scanning electron microscope (SEM) photographs of the membrane surface were taken before and after crossflushing and backflushing. Backflushing is highly effective, while crossflushing is partially effective, in removing the external cake formed during filtration of yeast suspensions. Crossflushing is completely ineffective and backflushing is only partially effective for removal of internal foulants during filtration of BSA solutions. During backflushing or crossflushing of yeast–BSA mixtures, complete or partial removal of the yeast cake reduces the hydraulic resistance to permeate flow. However, this removal also exposes the primary membrane to internal fouling by BSA, against which neither crossflushing nor backflushing is very effective.