High Bovine Serum Albumin Rejection Research Articles

Zeolite-Based Poly(vinylidene fluoride) Ultrafiltration Membrane: Characterization and Molecular Weight Cut-Off Estimation with Support Vector Regression Modelling.

Zeolite serves as a promising additive for enhancing the hydrophilicity of polymeric membranes, yet its utilization for bolstering the mechanical strength of the membrane remains limited. In this study, poly(vinylidene fluoride) (PVDF) membranes were modified by incorporating various concentrations of zeolite (0.5-2 wt%) to improve not only their mechanical properties, but also other features for water filtration. Membranes with and without zeolite incorporation were fabricated via a dry-wet phase inversion technique, followed by the application of a series of characterization techniques in order to study their morphological structure, mechanical strength, and hydrophilicity. The membrane filtration performance for each membrane was evaluated based on pure water flux and Bovine Serum Albumin (BSA) rejection. Field-Emission Scanning Electron Microscopy (FESEM) images revealed a dense, microvoid-free structure across all of the PVDF membranes, contributing to a high pristine PVDF membrane tensile strength of 14 MPa. The addition of 0.5 wt% zeolite significantly improved the tensile strength up to 19.4 MPa. Additionally, the incorporation of 1 wt% zeolite into PVDF membrane yielded improvements in membrane hydrophilicity (contact angle of 67.84°), pure water flux (63.49% increase), and high BSA rejection (95.76%) compared to pristine PVDF membranes. To further improve the characterization of the zeolite-modified PVDF membranes, the Support Vector Regression (SVR) model was adopted to estimate the molecular weight cut off (MWCO) of the membranes. A coefficient of determination (R2) value of 0.855 was obtained, suggesting that the SVR model predicted the MWCO accurately. The findings of this study showed that the utilization of zeolite is promising in enhancing both the mechanical properties and separation performance of PVDF membranes for application in ultrafiltration processes.

Porous organic polymer nanosheets doped multistage water channel ultrafiltration membrane: Accelerated phase inversion process and in-situ covalent crosslinking strategy

Mixed matrix membranes (MMMs) have attracted significant interest in the field of water treatment owing to their capability to integrate the scalability and processability of polymers with the selectivity of fillers. Despite the numerous advantages demonstrated by emerging nanofillers, currently developed MMMs are still limited by such as insufficient hydrophilicity, susceptibility to additive loss, and poor filler compatibility.To address these challenges, we developed a series of polyethersulfone (PES)-based MMMs featuring a hydrophilic surface and multistage water transport channels, thereby minimizing additive loss, and enhancing efficiency in water treatment processes. Through interfacial azo-coupling polymerization, we synthesized a series of hydrophilic and porous two-dimensional sulfonic acid-functionalized porous organic polymer nanosheets (NS-sPOPs) to be used as additives in the MMMs. Owing to the exceptional hydrophilicity and favorable dispersibility of NS-sPOPs in water, the nanosheets influenced phase inversion through an accelerated phase separation process, resulting in the formation of multistage channels. Polyphosphoric acid (PPA) was used for the post-crosslinking treatment of the PES/NS-sPOP membrane. Consequently, the NS-sPOPs were immobilized within the polymer matrix to ensure stable performance in subsequent use. The prepared PES/NS-sPOP membrane exhibited outstanding water permeability (pure water flux) of 493 L·m−2·h−1·bar−1, and a high bovine serum albumin rejection rate of 99.3 %. Furthermore, it exhibits consistent performance throughout a 48 h long-term stability test. Overall, the blending and crosslinking strategy of hydrophilic nanofillers enables the realization of superhydrophilic 2D nanosheet-doped multistage-water-channel MMMs with exceptional permeability and high selectivity for water purification and organic pollutant removal.

Effect of silver nanoparticles on the morphological, antibacterial activity and performance of graphene oxide-embedded polyvinylidene fluoride membrane

In this work, a different ratio of silver nanoparticles (Ag NPs) was used as a nanofiller on graphene oxide (GO)-embedded polyvinylidene fluoride (PVDF) membranes fabrication through a non-solvent induced phase separation method. The morphology of fabricated membranes was investigated using FTIR, XRD, and SEM-EDX techniques. The fabricated membranes were tested for Bovine Serum Albumin (BSA) rejection and Molecular Weight Cut Off (MWCO) with various initial concentrations of 100 – 400 ppm and 6 – 145 kDa, respectively using a crossflow method, as well as antibacterial activity against four strains bacteria via total plate counting and Kirby-Bauer method. The incorporation of hydrophilic GO and Ag NPs obviously alters membrane morphology, enhances membrane’s porosity and hydrophilicity. Moreover, it improves membrane crystallinity (> 70%) as indicated by the higher XRD peaks intensity. Based on the crossflow measurements, the membrane fabricated with GO and Ag ratio of 1: 3 (PVDF/GO/AgNPs – 3) demonstrated the highest BSA flux of 83.81 L/m2 h, which was third-fold higher than that of PVDF membrane as well as high BSA rejection (> 94%) and MWCO of ∼3 kDa. According to the observation, PVDF/GO/AgNPs – 3 also possessed a high bacteria killing ratio of > 94% and a large inhibition zone of ≥ 1.5 mm toward all bacteria strains. These results inferred that PVDF/GO/Ag membrane has great potential as antibiofouling membranes.

Characterization of a chlorine resistant and hydrophilic TiO2/calcium alginate hydrogel filtration membrane used for protein purification maintaining protein structure

The development of membranes for protein purification has stringent requirement of disinfection resistance, low protein adsorption and anti-fouling, without changing protein structure. In this study, hydrophilic titanium dioxide (TiO2)/calcium alginate (TiO2/CaAlg) hydrogel membranes were prepared by a simple ionic cross-linking method. The effects of the porogenic agent polyethylene glycol (PEG) concentration, the molecular weight of PEG, and the concentration of TiO2 on the filtration properties were systematically investigated. The TiO2/CaAlg membrane exhibited excellent bovine serum albumin (BSA) rejection and anti-fouling properties. The mechanical properties and surface energy of the TiO2/CaAlg membrane were significantly improved. The chemical bonding mechanism of TiO2 and NaAlg was investigated by molecular dynamic simulation. The TiO2/CaAlg membrane had good chlorine resistance and could be disinfected or cleaned with sodium hypochlorite. The TiO2/CaAlg hydrogel membrane loaded with polyhydroxybutyrate (PHB) nanofibers maintained high flux (136.7 L/m2h) and high BSA rejection (98.0 %) at 0.1 MPa. The results of circular dichroism and synchronous fluorescence indicated that the secondary structure of BSA was maintained after membrane separation. This study provides one method for the preparation of green and environmentally friendly membrane for protein purification.

Magnetic‐field‐inducedFe3O4@CNTsdispersion in the separation layer to improve the performance of composite ultrafiltration membrane

AbstractIt is of great significance to regulate carbon nanotubes (CNTs) dispersed in the separation layer of membranes to improve the properties of membranes. In this work, ferric oxides coated carbon nanotubes (Fe3O4@CNTs) are prepared by solvothermal method, and then are added to the casting solution to prepare Fe3O4@CNTs/poly(ethersulfone)/sulfonated polysulfone composite ultrafiltration membranes. The result shows that Fe3O4@CNTs migrate to the separation layer of membranes under the induction of a low‐intensity magnetic field. The surface and overall porosity of the membranes increase and the surface roughness of the membranes decreases. The contact angle of composite ultrafiltration membranes decreases from 78.0° to 60.1°, indicating an improvement of hydrophilicity. The pure water permeance of the composite ultrafiltration membranes increases from 240.1 to 524.7 L m−2 h−1while retaining a high bovine serum albumin rejection (>96.8%). Moreover, the antifouling property of the composite ultrafiltration membranes is significantly improved, and the flux recovery ratio increased from 56.2% to 80.9%.

Fabrication of Polyarylate-Based Porous Membranes from Nonsolvent-Induced Phase Separation Process and Related Permeability and Filterability Characterizations

The stability demand of polymeric membrane separation systems used in harsh environments, including high temperature, high pressure, extreme acid, and high salinity, makes the role of polyarylate (PAR) porous membranes more and more crucial. Herein, the PAR ultrafiltration membrane is fabricated from the nonsolvent-induced phase separation (NIPS) method in a simple, high-efficiency way. In order to study the evolution mechanism of cross-sectional pore morphologies during the NIPS process, different coagulation conditions, including the PAR concentration in casting solution, the coagulation temperature, and the addition of different hydrophilic additives (PEG400, PEG4000, PEG20000, and PVP), are applied. Next, the morphologies and membrane performances of various PAR membranes are analyzed by scanning electron microscopy, porosity measurement, N2 isotherm adsorption–desorption measurement, water flux measurement, bovine serum albumin (BSA) separation measurement, and mechanical test. Based on these measurements, the formation rule of different pore morphologies in the cross section of PAR membrane was clarified, and the effects of different cross-sectional morphologies on the permeability, filterability, and mechanical properties of the resultant membranes are pointed out. The viscosity effect from a higher PAR concentration and a higher hydrophilic additive concentration in a casting solution can delay the formation of the outer layer and limit the nucleation growth process of the nonsolvent, then allowing the formation of near-surface sponge-like pores and fewer inner macropores. Moreover, not only the increase of the bath temperature but also the strengthening hydrophilicity of the casting solution can accelerate the double-diffusion rate and the growth process of nuclei, thereby promoting the formation of near-surface finger-like pores and more inner macropores. Combined with the enhancement of membrane hydrophilicity, these pores as channels can accelerate the passage of water through the PAR membrane. For the PAR16–PVP10-30 membrane, not only a 120 L·m–2·h–1·bar–1 of water flux but also a close to 100% of BSA rejection ratio is obtained. Although the formation of near-surface sponge-like pores and fewer inner macropores deteriorate the membrane’s permeability, the high BSA rejection ratio and the improved mechanical property can be maintained. Finally, the optimization component of the casting solution for fabricating a PAR ultrafiltration membrane with enough permeability, high selectivity, and suitable mechanical property adds 10 wt % PVP in the solution of 16 wt % PAR, ensuring the solid hydrophilic effect and moderate viscosity effect.

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.

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.

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.

Preparation of Small-Pore Ultrafiltration Membranes with High Surface Porosity by In Situ CO2 Nanobubble-Assisted NIPS.

The fabrication of ultrafiltration (UF) membranes with a small pore size (<20 nm) and high surface porosity is still a great challenge. In this work, a nanobubble-assisted nonsolvent-induced phase separation (BNIPS) technique was developed to prepare high-performance UF membranes by adding a tiny amount of CaCO3 nanoparticles into the casting solution. The phase inversion occurred in a dilute-acid coagulation bath to simultaneously generate CO2 nanobubbles, which regulated the membrane structure. The effects of the nano-CaCO3 content in the casting solution on the structure and performance of poly(ethersulfone)/sulfonated polysulfone (PES/SPSf) UF membranes were studied. The UF membrane prepared from a casting solution with 0.3% nano-CaCO3 achieved a surface porosity of 12%, a pore diameter of 10.2 nm, and a skin-layer thickness of 80.3 nm. The superior structure of the UF membrane was mainly attributed to the in situ generation of CO2 nanobubbles because the CO2 nanobubbles were amphiphobic to water and solvents to delay the phase inversion time and acted as nanosize porogens. The produced membrane showed an unprecedented separation performance, achieving a pure water permeance of up to 1128 L·m-2·h-1·bar-1, 2.5 fold that of the control membrane. Similarly, a high bovine serum albumin rejection of above 99.0% was obtained. The overall permeability and selectivity were better than those of commercial and other previously reported UF membranes. This work provides insight toward a simple and cost-effective technique to address the trade-off between pure water permeance and solute rejection of UF membranes.

Enhancing the permeation and antifouling performance of PVDF hybrid membranes by incorporating Co–Fe hydroxide nanoparticles in reverse microemulsion

This study attempted to enhance the permeation and antifouling performance of polyvinylidene fluoride (PVDF) ultrafiltration membranes. Reverse microemulsion containing cobalt and iron (Co–Fe) bimetallic hydroxide nanoparticles was blended with the PVDF membranes to construct a novel PVDF hybrid membrane. The permeation performance, antifouling property, and long-term operational stability of the hybrid membranes were evaluated via ultrafiltration process of water flux and bovine serum albumin (BSA) rejection. Structural characterization showed that the protection endowed by reverse microemulsion made the hydroxide nanoparticles to distribute uniformly in the PVDF polymeric matrix. The introduction of well-distributed bimetallic hydroxide nanoparticles substantially improved the pore structures and hydrophilicity of the PVDF hybrid membranes, thereby enhancing their permeation performance and antifouling property. The optimal water flux of the PVDF hybrid membranes (MD-10) reached 328 L·m−2·h−1 and was 5.4-fold higher than that of neat PVDF. Moreover, the MD-10 membrane had a high a high BSA rejection rate (91.04%). After four cycles of successive fouling-cleaning processes, the water flux of the MD-10 membrane still exceeded 160 L·m−2·h−1 and was fourfold higher than that of neat PVDF. However, excessive amounts of the microemulsion could not be uniformly mixed with the PVDF membranes, thereby decreasing the permeation and antifouling performance of the PVDF hybrid membranes.

Prediction of the phenol removal capacity from water by adsorption on activated carbon.

High-performance sulfonated polysulfone (SPSf) mixed-matrix membranes (MMMs) were fabricated via a nonsolvent-induced phase separation (NIPS) method using zeolitic imidazolate frameworks-67 (ZIF-67) as a crosslinker. Acid-base crosslinking occurred between the sulfonic acid groups of SPSf and the tertiary amine groups of the embedded ZIF-67, which improved the dispersion of ZIF-67 and simultaneously improved the membrane strzcture and permselectivity. The dispersion of ZIF-67 in the MMMs and the acid-base crosslinking reaction were verified by energy-dispersive X-ray spectroscopy (EDX), X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The pore structure analysis of MMMs indicated that filling ZIF-67 into SPSf enhanced the average surface pore sizes, surface porosities and more micropore in cross-sections. The crossflow filtrations showed the MMMs have higher pure water fluxes (57 to 111 L m-2 h-1) than the SPSf membrane (55 L m-2 h-1) but also higher bovine serum albumin (BSA) rejection rate of 93.9-95.8%, a model protein foulant. The MMMs showed a higher water contact angle than the SPSf membrane due to the addition of hydrophobic ZIF-67 and acid-base crosslinking, and also maintained high thermal stability evidenced by the thermogravimetric analysis (TGA) results. At the optimal ZIF-67 concentration of 0.3 wt%, the water flux of the SPSf-Z67-0.3 membrane was 82 L m-2 h-1 with a high BSA rejection rate of 95.3% at 0.1 MPa and better antifouling performance (FRR = 70%).

Uncovering the effects of PEG porogen molecular weight and concentration on ultrafiltration membrane properties and protein purification performance

Developing ultrafiltration (UF) membranes for protein purification requires a critical understanding of the pore engineering and active-layer morphological control. In this study, we systematically explored the use of polyethylene glycol (PEG) with molecular weights (MW, 600–6000 g⋅mol−1) and concentration (3–7.5 wt%) as a pore modifier to prepare polyvinyl difluoride (PVDF) membranes via the non-solvent phase-inversion process. The membranes demonstrated a high degree of control of the structure-property-performance relationship for improving the water flux, bovine serum albumin (BSA) rejection and antifouling properties. We found that the morphology of PEG-modified membranes showed the membrane surface crystal spherulite remarkably decreased, whilst surface pore size increased with increasing porogen MW. Similarly, the increase in membrane pore size correlated very well with porogen MW and concentration exponentially and linearly respectively. Furthermore, the PEG-MW membrane series showed a flux and rejection trade-off, whereas the PEG-concentration membrane series can produce a high BSA rejection and improve the flux owing to the presence of a dense active layer. Overall, the optimized membrane with the best protein separation properties was produced by using 6 wt% PEG with 600 g⋅mol−1, which reached a competitive permeate flux of ~60 LMH⋅bar−1, with excellent flux recovery rate of >90%, and a high BSA rejection rate of 90% at the end of the three test cycle. The results in this study have elucidated and advanced the fundamental knowledge of the interrelationship between porogen and membrane property-performance.

Improved Performance of Polysulfone Ultrafiltration Membrane Using TCPP by Post-Modification Method.

Ultrafiltration (UF) membranes have found great application in sewage purification and desalination due to their high permeation flux and high rejection rate for contaminants under low-pressure conditions, but the flux and antifouling ability of UF membranes needs to be improved. Tetrakis (4-carboxyphenyl) porphyrin (TCPP) has good hydrophilicity, and it is protonated under strongly acidic conditions and then forms strong hydrogen bonds with N, O and S, so that the TCPP would be well anchored in the membrane. In this work, NaHCO3 was used to dissolve TCPP and TMC (trimesoyl chloride) was used to produce a strong acid. Then, TCPP was modified in a membrane with a different rejection rate by a method similar to interfacial polymerization. Performance tests of TCPP/polysulfone (PSf) membranes show that for the membrane with a high BSA (bovine serum albumin) rejection, when the ratio of NaHCO3 to TCPP is 16:1 (wt.%), the pure water flux of membrane Z1 16:1 is increased by 34% (from 455 to 614 Lm−2h−1bar−1) while the membrane retention was maintained above 95%. As for the membrane with a low BSA rejection, when the ratio of NaHCO3 to TCPP was 32:1, the rejection of membrane B2 32:1 was found to increase from 81% to 96%. Although the flux of membrane B2 32:1 decreased, it remained at 638 Lm−2h−1bar−1, which is comparable to the reported polymer ultrafiltration membrane. The above dual results are thought to be attributed to the synergistic effect of protonated TCPP and NaHCO3, where the former increases membrane flux and the latter increases the membrane rejection rate. This work provides a way for the application of porphyrin and porphyrin framework materials in membrane separation.

Polysulfone Membranes Embedded with Halloysites Nanotubes: Preparation and Properties.

In the present study, nanocomposite ultrafiltration membranes were prepared by incorporating nanotubes clay halloysite (HNTs) into polysulfone (PSF) and PSF/polyvinylpyrrolidone (PVP) dope solutions followed by membrane casting using phase inversion method. Characterization of HNTs were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermogravimetric (TGA) analysis. The pore structure, morphology, hydrophilicity and mechanical properties of the composite membranes were characterized by using SEM, water contact angle (WCA) measurements, and dynamic mechanical analysis. It was shown that the incorporation of HNTs enhanced hydrophilicity and mechanical properties of the prepared PSF membranes. Compared to the pristine PSF membrane, results show that the total porosity and pore size of PSF/HNTs composite membranes increased when HNTs loadings were more than 0.5 wt % and 1.0 wt %, respectively. These findings correlate well with changes in water flux of the prepared membranes. It was observed that HNTs were homogenously dispersed within the PSF membrane matrix at HNTs content of 0.1 to 0.5 wt % and the PSF/HNTs membranes prepared by incorporating 0.2 wt % HNTs loading possess the optimal mechanical properties in terms of elastic modulus and yield stress. In the case of the PSF/PVP matrix, the optimal mechanical properties were obtained with 0.3 wt % of HNTs because PVP enhances the HNTs distribution. Results of bovine serum albumin (BSA) filtration tests indicated that PSF/0.2 wt % HNTs membrane exhibited high BSA rejection and notable anti-fouling properties.

Fabrication of a Novel Antifouling Polysulfone Membrane with in Situ Embedment of Mxene Nanosheets.

Membrane fouling is still a critical issue for the application of ultrafiltration, which has been widely used in water treatment due to its efficiency and simplicity. In order to improve the antifouling property, a new 2D material MXene was used to fabricate composite ultrafiltration membrane with the approach of in situ embedment during the phase inversion process in this study. Scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), water contact angle, bovine serum albumin rejection and porosity measurements were utilized to characterize the prepared membranes. Due to the hydrophilicity of the MXene, the composite membranes obtained higher hydrophilicity, confirmed by the decreased water contact angle. All the modified membranes had a high bovine serum albumin rejection above 90% while that of the pristine polysulfone membrane was 77.48%. The flux recovery ratio and the reversible fouling ratio of the membranes were also improved along with the increasing content of the MXene. Furthermore, the highest flux recovery ratio could also reach 76.1%. These indicated the good antifouling properties of MXene composite membranes. The enhanced water permeability and protein rejection and excellent antifouling properties make MXene a promising material for antifouling membrane modification.

ANOVA Design for the Optimization of TiO2 Coating on Polyether Sulfone Membranes.

There have been developments in the optimization of polyethersulfone (PES) membranes, to provide antifouling and mechanically stable surfaces which are vital to water purification applications. There is a variety of approaches to prepare nanocomposite PES membranes. However, an optimized condition for making such membranes is in high demand. Using experimental design and statistical analysis (one-half fractional factorial design), this study investigates the effect of different parameters featured in the fabrication of membranes, as well as on the performance of a nanocomposite PES/TiO2 membrane. The optimized parameters obtained in this study are: exposure time of 60 s, immersion time above 10 h, glycerol time of 4 h, and a nonsolvent volumetric ratio (isopropanol/water) of 30/70 for PES and dimethylacetamide (PES-DMAc) membrane and 70/30 for PES and N-methyl-2-pyrrolidone (PES-NMP) membrane. A comparison of the contributory factors for different templating agents along with a nanocomposite membrane control revealed that F127 triblock copolymer resulted in an excellent antifouling membrane with a higher bovine serum albumin rejection and flux recovery of 83.33%.

Preparation And Characterizations Of Poly(vinyl butyral)/Caprolactam/Polyethylene Glycols Hydrophilic Flat‐sheet Membrane Through Thermally Induced Phase Separation

AbstractPoly(vinyl butyral)/caprolactam/polyethylene glycols hydrophilic flat‐sheet membranes were prepared via thermally induced phase separation (TIPS) for the first time. Poly(vinyl butyral) (PVB) was used as polymers,caprolactam (CPL) and polyethylene glycols (PEG) were used as mixed diluent. In all situations, the system occurs liquid‐liquid (L−L) phase separation to obtain asymmetric honeycomb structures. The effects of PVB concentration and molecular weight of PEG on the structure and performance of the flat‐sheet membranes were investigated in detail. Herein, the obtained PVB/CPL/PEG microporous membrane has some hydrophilicity and high BSA rejection ratio. Particularly, when the PVB concentration was 30 wt%, the PVB/CPL/PEG200 membrane achieved the highest bovine serum albumin (BSA) rejection of 85.36%. The prepared membrane had good antipollution performance, and the minimum adsorption amount of BSA was 4.94 g/m2. Those results show the PVB microporous membrane has great application prospects in the field of water treatment.

Low band-gap energy photocatalytic membrane based on SrTiO3–Cr and PVDF substrate: BSA protein degradation and separation application

A series of ultrafiltration (UF) membranes based on mixed matrix of chromium-doped strontium titanate (SrTiO3–Cr) photocatalyst and polyvinylidene difluoride (PVDF) were systematically prepared by non-solvent induced phase inversion technique. Porous PVDF membrane and mixed matrix membranes (MMMs) incorporated with 3–10 wt% SrTiO3–Cr were produced in the UF range using polyethylene glycol as a porogen additive. The crystal morphology and electronic property of as-synthesized Cr-doped SrTiO3 nanoparticles were characterized by XRD and UV–Vis DRS. We found that the SrTiO3–Cr nanoparticles are cubic perovskite structure of approximately 30–40 nm in size with a low band gap energy of 2.05 eV. The morphology, surface roughness, hydrophilicity and textural properties of SrTiO3–Cr/PVDF MMMs were comprehensively characterized using field emission-scanning electron microscope with energy-dispersive X-ray spectroscopy, atomic force microscope, sessile drop technique, and capillary flow porometer. The SrTiO3–Cr was observed to be homogeneously dispersed in all the MMMs and provided additional anti-fouling properties from Bovine Serum Albumin (BSA) protein. The membrane UF property and tri-cycling performance were evaluated under three distinct protocols in (1) Dark, (2) constant UVA exposure, and (3) UVA during post-treatment clean only. By increasing the SrTiO3–Cr concentration, the MMMs displayed an improved homogeneity and macropore distribution with enhanced water permeability given by 51–110 LMH bar−1 pure water flux and 37 to 45 LMH bar−1 BSA water flux in the Dark. A consistently high BSA rejection of 95% and an improved anti-fouling property under constant UVA irradiation were achieved due to a combination of photo-induced hydrophilic and photocatalytic effect. Also, a significant improvement in UF performance in terms of membrane flux recovery was observed in the 3rd protocol signifying that the effect of protein fouling on membrane filtration was further reduced due to a lower degree of BSA fragment deposition in the membrane pores. The findings in this study dramatically lower the operational constraints (transmembrane pressure, membrane cleaning, use of UVA) in the protein filtration process and offer an innovative membrane material for the research of photo-induced, anti-fouling membranes for protein separation applications.

The role of pre-evaporation in the preparation process of EVOH ultrafiltration membranes via TIPS

The poly(ethylene-co-vinyl alcohol) (EVOH) ultrafiltration membrane is prepared via pre-evaporation combined thermally induced phase separation (TIPS), using a novel co-solvent that is a mixture of sulfolane and 1,3-propanediol. The porous surface is mainly caused by the low cooling rate of pre-evaporation stage. Based on the shorter pre-evaporation time, the evaporation of 1,3-propanediol provides a foundation for asymmetric structure. Subsequently, the quenching effect of water bath forms a dense layer below the porous surface. The compact degree of dense layer increases first and then decreases with the increase of pre-evaporation time (τ) or pre-evaporation temperature (T) or the mass fraction of 1,3-propanediol in co-solvent (β). Therefore, the rejection of bovine serum albumin (BSA) increases first and then decreases as τ or T or β increases. Meanwhile, the connectivity of membrane structure can also be adjusted by changing β. Finally, the EVOH ultrafiltration membrane prepared from τ = 20 s, T = 25 °C and β = 15% achieves relatively high BSA rejection of 98% and relatively large pure water flux of 302 L m−2 h−1 bar−1.