Bovine Serum Albumin Filtration Research Articles

Enhanced antifouling and separation capabilities of polydopamine@Ce-MOF functionalized PES ultrafiltration membrane

The need for antifouling membranes is substantial due to fouling’s negative impact on the effectiveness and durability of ultrafiltration membranes. In recent times, Metal-Organic Frameworks (MOFs) have emerged as effective additives for crafting ultrafiltration (UF) membranes. However, to harness their benefits and mitigate their drawbacks, a well-considered approach is imperative. In this work, polyethersulfone (PES) UF membranes were tailored with polydopamine (PDA)-modified cerium (Ce)-MOF (PDA@Ce-MOF) to achieve satisfactory antifouling properties and to remove biological macromolecules such as bovine serum albumin (BSA) and humic acid (HA) from wastewater. The non-solvent induced phase separation (NIPS) method was used to simultaneously fabricate the membrane and modify it with different PDA@Ce-MOF concentrations ranging from 0.05 to 0.50 wt.%. Results showed significant improvements on the membrane’s morphology, hydrophilicity, porosity and pore size at 0.10 wt.% loading of PDA@Ce-MOF. The synergistic effect of the PDA and Ce-MOF on the membrane improved the pure water flux (337 L m−2 h−1) and filtration performance in the filtration of Bovine serum albumin (BSA) and humic acid (HA) reporting 145 L m−2 h−1 and 98% rejection, and 164 L m−2 h−1 and 88% rejection; respectively. Further, water-attracting functional moieties of PDA@Ce-MOF hindered the deposition of BSA protein on the membrane surface, resulting in an excellent flux recovery ratio (FRR) of ~87%, alongside mitigated irreversible fouling.

Enhancing filtration flux and antifouling performance of PVDF membrane constructed from semi-interpenetrating network and block copolymers

Organic fouling causes the filtration property and serve life decrease of the PVDF membrane and is the challenge for filtration applications. Therefore, it is an urgency desire to construct a PVDF membrane with good filtration and antifouling for researchers. To this end, a based PVDF and poly(N-isopropyl acrylamide)(PNIPA) semi-interpenetrating network polymer was synthesized and used as membrane matrix for preparing semi-interpenetrating network/block copolymers blend membrane. The membrane composition, structure and performance were systematically characterized and investigated by FTIR spectrum, XPS, SEM, contact angle instrument and the other experimental techniques etc. Results indicate that the prepared membrane contains PVDF, PNIPA and block copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b- poly(ethylene oxide) (F127) components, shows a porous cross section comprising a thin top surface layer with small pores, a finger-shape lower layer and a sponge-shape pore bottom layer. When the membrane are used for the filtration of bovine serum albumin(BSA) in aqueous solution at 25 ℃, the rejection can exceed 95.0% at a high flux of 307 L/(m2·h·bar). Simply raising filtration temperature to 60 °C, the flux can reach 606 L/(m2·h·bar) while the rejection barely changes, significantly improving the filtration ability of the membrane. Furthermore, the flux can recover above 93% of the original value after a BSA filtration and a subsequent water washing. Undoubtedly, the prepared membrane displays great potential for filtering BSA aqueous solution and the reason can be ascribed to the synergy between PNIPA and F127 of the membrane.

Fabrication of silver nanoparticle decorated graphene oxide membranes for water purification, antifouling and antibacterial applications

The quality of portable water is adversely affected by inadequate wastewater treatment, increase in domestic & industrial waste, and microbial contamination of surface water sources. Purification techniques such as sedimentation, precipitation, filtration, and ion exchange can be employed to recover clean water from various impurities. Among these, membrane-based purification methods have become more appealing in recent years due to its cost-effective and energy-saving features. However, fouling is a ubiquitous problem in membrane-based purification technologies, which leads to reduced water permeation and quality. Present study embodies the development of silver decorated graphene oxide coated nylon membrane with remarkable antibacterial and antifouling properties. Antibacterial analysis of bacteria Staphylococcus aureus and Escherichia coli, validates that higher concentration of silver in GO (GO A500) composites hinder the growth of bacteria. The antifouling properties of GO A500 membrane showed flux recovery ratio of 96 % with irreversible fouling ratio of 3 % during the filtration of BSA (Bovine serum albumin) protein. Further fabricated composite membrane exhibited pure water flux of 46.7 L m−2 h−1 with dye removal rate of 95 %, 88 % and 85 % for Congo red, Rhodamine-B and Methylene blue respectively. Catalytic studies conducted on GO A500 membrane demonstrated the efficacy of their antifouling properties. The investigations revealed that the composite (GO A500) membrane has excellent antibacterial and antifouling properties, making it a suitable option for wastewater treatment applications.

Surface modification of a PVDF membrane by co‐grafting hydroxyl and zwitterionic polymers to enhance wettability and antifouling property

AbstractPolyvinylidene fluoride (PVDF) membranes have been widely applied in the separation of various organic matters owing to their excellent properties. However, they possess low wettability and undergo fouling because of the hydrophobic nature of PVDF. In this study, poly (2‐hydroxyethyl methacrylate) (PHEMA) and poly (sulfobetaine methacrylate) (PSBMA) were co‐introduced to modify the highly hydrophobic PVDF membrane surface via UV photo‐irradiation. Facile UV photo‐grafting was performed by irradiating the pristine PVDF membrane immersed in a PHEMA/PSBMA mixture solution with UV light for 5 min. The performance of the as‐prepared PHEMA/PSBMA‐grafted membrane was compared with that of membranes modified with solely PHEMA or PSBMA. The hydroxyl and zwitterionic groups of the grafted membranes enhanced wettability and increased flux. A tightly bound water layer was formed because of the enhanced wettability, significantly suppressing protein adsorption. The initial flux of bovine serum albumin (BSA) solution through the PHEMA/PSBMA‐grafted membrane was 2861 LMH, which was 3.1 times higher than that obtained by the pristine PVDF membrane. Furthermore, the flux decline of the modified membrane caused by BSA fouling was 49% lower than that of the pristine PVDF membrane. Finally, the PHEMA/PSBMA‐grafted PVDF membrane showed antifouling properties after three BSA filtration cycles.

Permeable and antifouling PSf‐Cys‐CuO ultrafiltration membrane for separation of biological macromolecules proteins

AbstractMembrane technology has been extensively applied for protein separation. A membrane with reliable filtration performance and high removal efficiency is required. In this study, an ultrafiltration (UF) membrane was fabricated by dry‐wet phase inversion to incorporate copper oxide nanoparticles (CuO NPs) with a different ratio of L‐cysteine (Cys) in polysulfone (PSf). The characterization of the membrane involves using scanning electron microscopy (SEM), water contact angle, water content, pore size, and porosity analysis. The membrane performance evaluation includes flux permeation and bovine serum albumin (BSA) removal as a protein foulant. The membrane antifouling feature was examined by dynamic filtration of BSA. It was found that the Cys to CuO NPs ratio of 1.7:1 gives an optimal value on flux permeation and protein removal. The membrane exhibited high removal of BSA with 96.3%, and optimum water flux was achieved at 173.3 L/m2h, respectively. The highest permeability of aqueous BSA permeate at 500 ppm was about 111 L/m2h and 82.5 L/m2h for 1000 ppm. The enhancement of PSf‐Cys‐CuO membrane performance could be due to its lower contact angle (68.7°), high porosity (68%), and ideal pore size (46 nm) as well as showing good morphological structure. Most significantly, the inclusion of Cys improves antifouling capabilities. The membrane showed a lower chance of fouling based on the evaluation of the relative flux reduction and flux recovery ratio. Hence, the availability of Cys has a better impact on the polymer‐based membrane and seems promising for protein separation applications.

Preparation of a Low-Protein-Fouling and High-Protein-Retention Membrane via Novel Pre-Hydrolysis Treatment of Polyacrylonitrile (PAN)

The attainment of high-protein-retention and low-protein-fouling membranes is crucial for industries that necessitate protein production or separation process. The present study aimed to develop a novel method for preparing polyacrylonitrile (PAN) membranes possessing a highly hydrophilic and negatively charged surface as well as interior structure. The method involved a pre-hydrolysis treatment during the preparation of the PAN dope solution, followed by phase inversion in an alkaline solution. Chemical and material characterization of the dopes and membranes uncovered that the cyclized PAN structure served as a reaction intermediate that facilitated strong hydrolysis effect during phase inversion and homogeneously formed carboxyl groups in the membrane's interior structure. The resulting membrane showed a highly hydrophilic surface with a contact angle of 12.4° and demonstrated less than 21% flux decay and more than 95% flux recovery during multi-cycle filtration of bovine serum albumin (BSA) solution, with a high protein rejection rate of 96%. This study offers a facile and effective alternative for preparing PAN membranes with enhanced antifouling and protein-retention properties.

High performance loose nanofiltration membranes with enhanced fouling-resistance by rapid covalent co-deposition of dopamine and diamine-zwitterion

Nanofiltration (NF) membranes have been extensively employed for the treatment of textile wastewater to produce clean water, due to their capability of retaining small organic molecules. In this study, zwitterionic loose nanofiltration (Z-NF) membranes have been successfully fabricated by the rapid co-deposition of dopamine and diamine-zwitterion (Z-DNMA) via covalent bonds. The fabricated Z-NF membranes show improved hydrophilicity and enhanced fouling-resistant ability due to the incorporation of the zwitterionic functionality. Following the systematic investigation on the ratio between dopamine and Z-DNMA as well as the co-deposition time, the identified optimum membrane (Z-NF3) exhibits a high pure water permeability (PWP) of 32.0 LMH bar−1 and high organic dye rejections of 99.7 % and 98.6 % for Congo red (CR) and methyl blue (MB), respectively. In addition, the fouling experiments of Z-NF3 show that the flux recovery ratios (FRRs) for the filtration of bovine serum albumin (BSA), sodium alginate (NaAlg), and CR are 99.1 %, 92.0 %, and 82.2 %, respectively, along with lower irreversible fouling ratios (Rir) and higher reversible fouling ratios (Rr) values compared to those of the control membrane. The high PWP and high rejections to organic dyes, coupled with its superior fouling-resistant performance, indicate its great potential for practical applications in the treatment of textile wastewater.

Characterization of polyamide thin film composite membranes incorporated silver nanoparticles

AbstractIn this study, the polyamide thin film composite membrane surface has been modified by anti‐microbial silver nanoparticles (AgNPs). The membrane surfaces were interwoven with AgNPs by ultraviolet grafting polymerization method using AgNPs with or without poly(ethylene glycol) (PEG). The membrane surface characteristics were determined by scanning electron microscopy–energy dispersive x‐ray spectrometry images, attenuated total reflection–Fourier transforms infrared spectroscopy, water contact angle values, and anti‐bacterial property. The separation performance was determined based on the flux and the ability to remove calcium ions in water. The anti‐biofouling property was appraised through the maintained flux ratios and the irreversible fouling factors of unmodified and modified membranes during 10 h‐filtration of protein bovine serum albumin (BSA) in an aqueous solution, in which, before filtration of BSA, all membranes were immersed in E. coli bacteria solution for 4 days. The results of the experiments corroborated the hydrophilicity and more anti‐microbial property of the membrane surfaces after being incorporated into AgNPs. The water contact angle decreased from around 49° for the unmodified membrane to 36° and 23° for the AgNP‐modified membranes without/with PEG, while no colonies appeared in the medium containing the AgNP‐modified membranes. The separation property of modified membranes was improved, with both membrane flux and antifouling properties, along with the substantial surge of the anti‐biofouling property. After 10 h of BSA filtration, the fluxes of the modified membranes were maintained at 68% and 78% for AgNP‐modified membranes without and with PEG, respectively. Conversely, this value was only 46% for the unmodified one.

A novel method to immobilize zwitterionic copolymers onto PVDF hollow fiber membrane surface to obtain antifouling membranes

Zwitterionic materials are considered to be a promising new-generation non- or low-fouling materials. However, stable, and straightforward introduction of zwitterions into membranes for commercial production remains as a big challenge yet. Herein for the first time we propose a simple approach to immobilize zwitterionic copolymers on poly(vinylidene fluoride) (PVDF) hollow fiber membrane (HFM) surfaces with considerably high stability via surface entrapment and subsequent simple reactions. First, a commercial amphiphilic copolymer, viz. styrene–maleic anhydride (PSMA), was entrapped on the outer surface of PVDF membranes using co-extrusion by a triple orifice spinneret. PSMA exhibited excellent stability on the PVDF membrane, and its reactive anhydride (MA) group was stabilized on the outer membrane surface. Next, the commercially available zwitterionic copolymer poly(2-methacryloyloxyethyl phosphorylcholine-co-2-aminoethyl methacrylate hydrochloride) (P(MPC-AEMA)) was immobilized on the PVDF/PSMA membrane surface by a simple reaction between the MA groups of PSMA and the amine groups of P(MPC-AEMA). The P(MPC-AEMA) reacted membrane exhibited noticeable bovine serum albumin (BSA) antifouling and antibacterial properties during both static adsorption and dynamic filtration. The flux recovery ratio (FRR) of the membrane exceeded 80% after seven cycles of BSA filtration. The modified membrane showed an even higher FRR (∼95%) during bacterial filtration, and such excellent performance was attributed to its super hydrophilicity. Our novel, advanced and straightforward modification method lights on a spotlight for a new pathway to make immobilization of zwitterions on polymeric membrane without needing complicated reactions or procedures.

Removal of protein, histological dye and tetracycline from simulated bioindustrial wastewater with a dual pore size PPSU membrane

Wastewater from production of active pharmaceutical ingredients (APIs) often contains proteins, azo dyes or antibiotics, which cause severe water eutrophication and growth of drug-resistant bacteria. A series of polyphenylsulfone (PPSU) membranes was prepared to determine the relationships between pore structures and the abilities of different membranes to separate foulants, and the characteristics and performance of the ultrafiltration membranes were investigated. The structure of the skin layer and the cross-sectional texture were converted from dense and finger-like macrovoids to porous sponge shapes because of a delayed liquid–liquid (L-L) demixing time. Formation of novel PPSU membranes via noncovalent bonding interactions was evaluated, and this selectively affected the membrane surface pore structure, layer thickness, surface polarity and electronic repulsive force. All PPSU membranes demonstrated excellent rejection of organic foulants, including bovine serum albumin (BSA) (~100% rejection) and acid red 1 (AR1) (~90% rejection). Additionally, M5 provided an excellent tetracycline (TC) rejection efficiency of 89% in the 1st cycle. Due to the small size of TC, pore size effects were displayed. Moreover, the pure water flux recovery rate (FRR) increased from 85% (M1, water/ethanol: 100/0) to 99.9% (M4, water/ethanol: 30/70) after BSA filtration because the weak nonsolvent decreased the roughness of the membrane surface, and the membrane made with added EtOH yielded excellent FRR values (99.9%) after AR1 filtration. Therefore, PPSU membranes successfully achieved over 90% rejection of organic foulants and excellent FRRs, indicating that they may be suitable for purifying wastewater from API plants that generate organic foulants with a wide range of sizes.

Asymmetrical ultrafiltration membranes based on polylactic acid for the removal of organic substances from wastewater

The continued use of non-biodegradable polymeric-based membranes for water purification has led to an unsustainable accumulation of waste at disposal, resulting in various environmental problems. In this study, eco-friendly asymmetric ultrafiltration (UF) membranes were fabricated from polylactic acid (PLA) with different polymer concentrations using the phase inversion method. The fabricated membranes were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, porosity, and pore size analysis. Permeate flux and organic matter (bovine serum albumin (BSA)) rejection were evaluated using synthetic wastewater. The anti-fouling properties of PLA membranes were investigated through static adsorption and dynamic filtration of BSA. Furthermore, the performance of the best performing PLA membrane was evaluated via chemical oxygen demand (COD) rejection as well as membrane fouling using raw municipal wastewater obtained from a local wastewater treatment plant (WWTP) in Abu Dhabi (UAE). The results indicated that increasing the PLA concentration to 20 wt% improved BSA removal from synthetic and raw wastewaters by up to 92 and 89%, respectively, in addition to improving the membrane anti-fouling property. The post-filtration and after cleaning FT-IR spectra revealed high antifouling property with no detection of BSA peaks, SEM images confirmed the reduction in membrane's pore size as PLA concentration increased, resulting in enhancing the antifouling properties of the membranes. In conclusion, this study demonstrated that PLA-UF membranes could be a viable eco-friendly alternative to traditional crude oil-derived membranes.

A Self-cleaning, catalytic titanium carbide (MXene) membrane for efficient tetracycline degradation through peroxymonosulfate activation: Performance evaluation and mechanism study

• The catalytic cobalt/MXene (CM) membrane was fabricated using a simple method. • The tetracycline (TC) was effectively degraded within 5 min. • The CM membrane displayed a high flux retention ratio for BSA filtration. • •SO 4 - and •OH contributed to the TC removal and membrane anti-fouling. • Fouling modeling was applied to unveil the fouling mechanism. Innovative integration of advanced oxidation processes (AOPs) and membrane separation can achieve efficient recycling of catalysts and membrane anti-fouling. In this study, a catalytic, self-cleaning Co 2+ /MXene (CM) membrane with low Co 2+ content (0.2 wt%) was engineered and fabricated using a facile metal ion-initiated gelation approach. The CM membrane exhibited a rapid and high removal efficiency (>97% within 5 min) for tetracycline (TC) in the presence of peroxymonosulfate (PMS). Moreover, the TC removal efficiency was also investigated under different experimental conditions. The self-cleaning capacity of the CM membrane was assessed by filtration of bovine serum albumin (BSA), showing that the CM membrane had a higher flux retention ratio (FRR) with peroxymonosulfate (PMS) (52%) than without PMS (22%). Fouling modelings indicated that the cake layer fouling became the primary parameter responsible for the permeability reduction in CM/PMS/BSA filtration. Quenching experiments and electron spin resonance (ESR) spectrum analysis revealed that sulfate radicals (•SO 4 - ) and hydroxyl radicals (•OH) jointly contributed to the catalytic and anti-fouling properties of the CM membrane. This study exemplifies a novel, time-saving strategy for the preparation of a catalytic, self-cleaning membrane capable of efficient wastewater remediation with membran anti-fouling properties.

Influence of GO-Ag nano-filler on the antibacterial, antifouling and hydrophilic characteristics of polyvinyl chloride membrane

The integral hydrophobic characteristic of polymers hinders their implementations towards water treatment. In the present work, highly hydrophilic and antifouling polyvinyl chloride membranes were fabricated based on graphene oxide-silver (GO-Ag) nanolayers. The distinctive infiltration approach of polyvinyl chloride resin through the stacked GO-Ag layers results in surface availability of highly hydrophilic graphene oxide nanosheets. Incorporation of different weight percent of GO-Ag to the polyvinyl chloride resin increases the permeability, rejection and antifouling properties of polyvinyl chloride membranes. Water contact angle of pure polyvinyl chloride was found to decrease from 92.5° to 61.4° for GO-Ag based membrane. Water flux and bovine serum albumin rejection of pure polyvinyl chloride membrane were improved from 192 Lm−2 h−1 to 613 Lm−2 h−1 and 81.5% to 92.1% respectively. Besides this, graphene oxide silver based membrane depicts least irreversible fouling 14.3% and highest flux recovery ratio 85.6%. Maintenance of high flux recovery ratio of P/GO-Ag 0.5 wt% membrane after three consecutive cycles of water and bovine serum albumin filtration justify the high durability of membrane. The synthesized GO-Ag nanoadditive showed appreciable antibacterial activity against Escherichia coli. Thermo gravimetric analysis and Differential scanning calorimetry analysis of GO-Ag based membranes proves their high thermal stability as well.

A novel conductive rGO/ZnO/PSF membrane with superior water flux for electrocatalytic degradation of organic pollutants

Ultrafiltration membranes have shown remarkable potential in the purification of textile printing and dyeing wastewater. However, ultrafiltration membranes have some disadvantages in wastewater treatment, such as membrane fouling and trade-off effect. Hence, a novel polysulfone (PSF)-reduced graphene oxide (rGO)-zinc oxide (ZnO) composite conductive ultrafiltration membrane was prepared via the simple and green method. The combination of conductive ultrafiltration membrane and external electric field could treat dye wastewater. The conductive rGO/ZnO/PSF membranes have high water flux (296 L m−2 h−1 Bar−1) and favorable removal rates (>90%) for Congo Red (CR), Methyl Orange (MO), and Methylene Blue (MB). Besides, rGO/ZnO/PSF membrane also showed excellent antifouling ability, which had a flux recovery rate of 93% after filtration of bovine serum albumin (BSA) under applied electric field. Due to the electrocatalytic cleaning, rGO/ZnO/PSF membrane exhibited a 90% flux recovery after filtering the dye. The rGO/ZnO/PSF membrane has good separation efficiency, electrocatalytic stability, and fouling resistance, and can effectively solve the purification of textile printing and dyeing.

Tailored thin film nanocomposite membrane incorporated with Noria for simultaneously overcoming the permeability-selectivity trade-off and the membrane fouling in nanofiltration process

Membrane fouling as well as the “trade-off effect” between water permeability and selectivity are the grand challenges for nanofiltration (NF) membranes. In this study, a macrocyclic molecule, Noria, was embedded in the polyamide layer to fabricate a thin film nanocomposite (TFN) membrane with high performances of separation and antifouling. Noria was first synthesized and dissolved in a piperazine (PIP) aqueous solution. Then the TFN membrane (i.e., PIP-Noria-TMC membrane, TMC is the abbreviation of 1,3,5-benzenetricarbonyl trichloride) was prepared by interfacial polymerization using PIP-Noria mixture as aqueous phase. The optimal PIP-Noria-TMC membrane reached 147.6 L m-2h-1MPa-1 of water permeability, which was almost twice that of the pristine NF membrane (i.e., PIP-TMC membrane). Meanwhile, the PIP-Noria-TMC membrane exhibited comparable Na2SO4 rejection (∼98%) to the PIP-TMC membrane and outstanding mono/divalent salt selectivity. Besides, static adsorption tests using E.coli and bovine serum albumin (BSA) as the model foulants revealed that the surface of PIP-Noria-TMC membranes with high hydrophilicity and electronegative charge could effectively resist foulant attachment, which was also exhibited in the dynamic BSA filtration tests. Therefore, this work provided a practicable pathway to simultaneously overcome the permeability-selectivity trade-off and membrane fouling problems for the NF process.

Preparation of Ultrafiltration Membrane by Polyethylene Glycol Non-Covalent Functionalized Multi-Walled Carbon Nanotubes: Application for HA Removal and Fouling Control.

Polyethylene glycol (PEG) non-covalent-functionalized multi-walled carbon nanotubes (MWCNT) membrane were prepared by vacuum filtration. The dispersion and stability of MWCNT non-covalent functionalized with PEG were all improved. TEM characterization and XPS quantitative analysis proved that the use of PEG to non-covalent functionalize MWCNT was successful. SEM image analysis confirmed that the pore size of PEG–MWCNT membrane was more concentrated and distributed in a narrower range of diameter. Contact angle measurement demonstrated that PEG non-covalent functionalization greatly enhanced the hydrophilicity of MWCNT membranes. The results of pure water flux showed that the PEG–MWCNT membranes could be categorized into low pressure membrane. PEG-MWCNT membrane had a better effect on the removal of humic acid (HA) and a lower TMP growth rate compared with a commercial 0.01-μm PVDF ultrafiltration membrane. During the filtration of bovine serum albumin (BSA), the antifouling ability of PEG-MWCNT membranes were obviously better than the raw MWCNT membranes. The TMP recovery rate of PEG–MWCNT membrane after cross flushing was 79.4%, while that of raw MWCNT–COOH and MWCNT membrane were only 14.9% and 28.3%, respectively. PEG non-covalent functionalization improved the antifouling ability of the raw MWCNT membranes and reduced the irreversible fouling, which effectively prolonged the service life of MWCNT membrane.

Improvement in performance of g-C3N4 nanosheets blended PES ultrafiltration membranes including biological properties

This study aims to investigate the modification of polyethersulphone (PES) membrane with graphitic carbon nitride (g-C3N4) nanosheets for improving the antifouling and separation performance. The nanocomposite membranes were fabricated with blending of different g-C3N4 nanosheets (0.50, 1.00, and 2.00 wt%) into PES and they were synthesized by the phase inversion method. The fabricated g-C3N4 nanosheets and composite membranes were analyzed for their morphology. Scanning electron microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) mapping were used to detect the distribution of g-C3N4 nanosheets on membrane surface, whereas surface roughness of membrane was evaluated by atomic force microscopy (AFM). The composite membrane surface was found to be hydrophilic (67.54°), while the water flux of the composite membrane was found to be 254.8 L/m2/h for 2.00 wt% g-C3N4/PES membrane. The bovine serum albumin (BSA) separation tests indicated that the composite membrane supplied 98.5% BSA rejection ratio. Moreover, a significant improvement in antifouling characteristics were verified from BSA filtration experiments. g-C3N4 was also investigated for some of its biological properties such as antioxidant, antimicrobial, DNA cleavage, biofilm inhibition, and bacterial viability effect. g-C3N4 showed good free radical scavenging activity and moderate chelating activity at 500 mg/L. It was also determined that single-strand DNA cleavage activities occurred at all tested concentrations. g-C3N4 exhibited significant antibiofilm activity and inhibitory effects on E. coli vitality as 90.9%, 97.1%, and 98.9% at 250, 500, and 1000 mg/L, respectively. This study provides a simple and useful guideline to create a UF membrane resistant against organic fouling and expand its practical applications for wastewater treatment.

Hydraulic Resistance and Protein Fouling Resistance of a Zirconia Membrane with a Tethered PVP Layer

The influence of surface modification of zirconia (ZrO2) membrane with tethered poly(vinyl pyrrolidone) (PVP) chains was evaluated with respect to the impact of pH and ionic strength on hydraulic resistance and fouling resistance in the filtration of bovine serum albumin (BSA) and lysozyme (Lys) as model protein foulants. The tethered PVP surface layer led to membrane permeability and fouling propensity that were responsive to both pH and ionic strength. The PVP-modified membrane (PVP-ZrO2) hydraulic resistance increased by up to ~48% over a pH range of 6–11, but with no discernible impact at lower pH. Membrane hydraulic resistance was virtually unaffected by ionic strength over the 0.001–1 M range. However, reversible foulant cake resistance in BSA and Lys solution filtration increased with elevated ionic strength, owing in part to the weakening of protein–protein repulsion. Irreversible BSA and Lys fouling was affected by the operational pH relative to the protein isoelectric point (IEP) and reduced under conditions of chain swelling. Irreversible membrane fouling resistance for both proteins was significantly lower, by ~11–49% and 18–74%, respectively, for the PVP-ZrO2 membrane relative to the unmodified ZrO2 membrane. The present results suggest the merit of further exploration of fouling reduction and improvement of membrane cleaning effectiveness via tuning pH and ionic strength triggered conformational responsiveness of the tethered target polymer layer.

Novel polycarbonate membrane embedded with multi-walled carbon nanotube for water treatment: a comparative study between bovine serum albumin and humic acid removal

Flat sheet polycarbonate/multi-walled carbon nanotube (PC/MWCNT) nanocomposite membranes with different nanoparticle contents were prepared by applying the phase inversion method. The characteristics of the prepared membranes were analyzed by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), water contact angle, porosity, pure water flux (PWF), and mechanical properties. The performance of the membranes was evaluated in a submerged membrane system for two cycles and also for the filtration of humic acid (HA) and bovine serum albumin (BSA). The obtained results revealed that nanocomposites containing 0.1 wt% of MWCNTs showed better hydrophilicity, porosity, PWF, and mechanical properties. The FE-SEM images from surface indicated that the density and pore size of membrane increased from 0 to 0.1 wt% of MWCNTs. Moreover, according to AFM images, the PC/MWCNT-0.1 membrane showed a smoother surface than other samples. The antifouling performance of the membranes in a submerged membrane system revealed that the BSA solution flux for all membranes was lower than that of the HA solution due to the pore blocking of membranes occurring in the initial filtration of BSA. Apart from that addition of the 0.1 wt% of MWCNTs led to significant improvement in the fouling recovery ratio in the filtration of both HA and BSA because of the lower roughness and high hydrophilicity of the membrane surface. The rejection results revealed that the neat PC membrane had the highest value in the removal of HA and BSA with respect to other samples due to the formation of a thicker and denser cake layer on the membrane surface.

Preparation of Multipurpose Polyvinylidene Fluoride Membranes via a Spray-Coating Strategy Using Waterborne Polymers.

As reported herein, the waterborne polymers poly(glycidyl methacrylate-co-poly(ethylene glycol) methyl ether methacrylate) P(GMA-co-mPEGMA) and polyethyleneimine (PEI) were used to prepare multipurpose polyvinylidene fluoride (PVDF) membranes via a direct spray-coating method. P(GMA-co-mPEGMA) and PEI were alternately sprayed onto the PVDF membrane to yield stable cross-linked copolymer coatings. The successful coating of polymers onto the membrane surface was verified by scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterization. The coated membrane exhibited oil rejection rates that exceeded 99.0% for oil water mixture separation and 98.0% for oil/water emulsion separation. The flux recovery ratio reached 96.7% after bovine serum albumin filtration and washing with water. The removal efficiencies of the coated membrane M3 for Congo red, methyl orange, methylene blue, and crystal violet, Pb(II), Cu(II), and Cd(II) were 82.4, 83.9, 6.3, 26.8, 90.6, 91.3, and 86.2%, respectively. Thus, it can be used for the removal of dyes and heavy metal ions from wastewater. The antibacterial activities of the coated membranes were also confirmed by the inhibition zone tests and confocal laser scanning microscopy analysis. In addition, the cross-linking strategy provides the coated membranes with excellent durability and repeatability. More importantly, the use of water as the solvent can ensure that the application of these membrane coatings proceeds via a very safe and environmentally friendly coating process.