Surface modification of polyvinylidene fluoride (PVDF) membrane via radiation grafting: novel mechanisms underlying the interesting enhanced membrane performance

Effect of pH, NaCl concentration, and mAb concentration of feed solution on the filterability of Planova™ 20N and Planova™ BioEX

Virus filtration is one of the most important steps in ensuring viral safety during the purification of monoclonal antibodies (mAbs) and other biotherapeutics derived from mammalian cell cultures. Regarding the various virus retentive filters, including Planova filters, a great deal of data has been reported on the virus retention capability and its mechanism. Along with the virus retention capability, filterability is a key performance indicator for designing a robust and high-throughput virus filtration step. In order to obtain higher filterability, optimization of the feed solution conditions, and filter selection is essential; however, limited data are available regarding the filtration characteristics of Planova filters. Furthermore, for Planova 20N and Planova BioEX, the virus retention characteristics were reported to differ due to their respective membrane materials and layer structures. Whether these filters differ in their filtration characteristics is an interesting question, but no comparative evaluations have been reported. In this study, the filterability of the two filters was investigated and compared using 15 feed mAb solutions of a single mAb selected by design of experiments with different combinations of pH, NaCl concentration, and mAb concentration. The filterability of Planova 20N was affected not only by the feed solution viscosity, but also by the mAb aggregate content of the feed mAb solution and mAb-membrane electrostatic interactions. In contrast, the filterability of Planova BioEX decreased under some buffer conditions. These findings and the established design spaces of these filters provide valuable insights into the process optimization of virus filtration.

Temperature-Responsive Separation Membrane with High Antifouling Performance for Efficient Separation

Temperature-responsive separation membranes can significantly change their permeability and separation properties in response to changes in their surrounding temperature, improving efficiency and reducing membrane costs. This study focuses on the modification of polyvinylidene fluoride (PVDF) membranes with amphiphilic temperature-responsive copolymer and inorganic nanoparticles. We prepared an amphiphilic temperature-responsive copolymer in which the hydrophilic poly(N-isopropyl acrylamide) (PNIPAAm) was side-linked to a hydrophobic polyvinylidene fluoride (PVDF) skeleton. Subsequently, PVDF-g-PNIPAAm polymer and graphene oxide (GO) were blended with PVDF to prepare temperature-responsive separation membranes. The results showed that temperature-responsive polymers with different NIPAAm grafting ratios were successfully prepared by adjusting the material ratio of NIPAAm to PVDF. PVDF-g-PNIPAAm was blended with PVDF with different grafting ratios to obtain separate membranes with different temperature responses. GO and PVDF-g-PNIPAAm formed a relatively stable hydrogen bond network, which improved the internal structure and antifouling performance of the membrane without affecting the temperature response, thus extending the service life of the membrane.

Tailored PVDF Graft Copolymers via ATRP as High-Performance NCM811 Cathode Binders

High-nickel layered oxides, e.g., LiNi0.8Co0.1Mn0.1O2 (NCM811), are promising candidates for cathode materials in high-energy-density lithium-ion batteries (LIBs). Complementing the notable developments of modification of active materials, this study focused on the polymer binder materials, and a new synthetic route was developed to engineer PVDF binders by covalently grafting copolymers from poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) with multiple functionalities using atom transfer radical polymerization (ATRP). The grafted random copolymer binder provided excellent flexibility (319% elongation), adhesion strength (50 times higher than PVDF), transition metal chelation capability, and efficient ionic conductivity pathways. The NCM811 half-cells using the designed binders exhibited a remarkable rate capability of 143.4 mA h g-1 at 4C and cycling stability with 70.1% capacity retention after 230 cycles at 0.5 C, which is much higher than the 52.3% capacity retention of nonmodified PVDF. The well-retained structure of NCM811 with the designed binder was systematically studied and confirmed by post-mortem analysis.

Spin-Label Electron Paramagnetic Resonance Spectroscopy Reveals Effects of Wastewater Filter Membrane Coated with Titanium Dioxide Nanoparticles on Bovine Serum Albumin

The accumulation of proteins in filter membranes limits the efficiency of filtering technologies for cleaning wastewater. Efforts are ongoing to coat commercial filters with different materials (such as titanium dioxide, TiO2) to reduce the fouling of the membrane. Beyond monitoring the desired effect of the retention of biomolecules, it is necessary to understand what the biophysical changes are in water-soluble proteins caused by their interaction with the new coated filter membranes, an aspect that has received little attention so far. Using spin-label electron paramagnetic resonance (EPR), aided with native fluorescence spectroscopy and dynamic light scattering (DLS), here, we report the changes in the structure and dynamics of bovine serum albumin (BSA) exposed to TiO2 (P25) nanoparticles or passing through commercial polyvinylidene fluoride (PVDF) membranes coated with the same nanoparticles. We have found that the filtering process and prolonged exposure to TiO2 nanoparticles had significant effects on different regions of BSA, and denaturation of the protein was not observed, neither with the TiO2 nanoparticles nor when passing through the TiO2-coated filter membranes.

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver-graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm^-1 of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe²⁺) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10-100 mg L^-1 towards purification of groundwater for safe drinking water.

Advanced Polymeric Nanocomposite Membranes for Water and Wastewater Treatment: A Comprehensive Review

Nanomaterials have been extensively used in polymer nanocomposite membranes due to the inclusion of unique features that enhance water and wastewater treatment performance. Compared to the pristine membranes, the incorporation of nanomodifiers not only improves membrane performance (water permeability, salt rejection, contaminant removal, selectivity), but also the intrinsic properties (hydrophilicity, porosity, antifouling properties, antimicrobial properties, mechanical, thermal, and chemical stability) of these membranes. This review focuses on applications of different types of nanomaterials: zero-dimensional (metal/metal oxide nanoparticles), one-dimensional (carbon nanotubes), two-dimensional (graphene and associated structures), and three-dimensional (zeolites and associated frameworks) nanomaterials combined with polymers towards novel polymeric nanocomposites for water and wastewater treatment applications. This review will show that combinations of nanomaterials and polymers impart enhanced features into the pristine membrane; however, the underlying issues associated with the modification processes and environmental impact of these membranes are less obvious. This review also highlights the utility of computational methods toward understanding the structural and functional properties of the membranes. Here, we highlight the fabrication methods, advantages, challenges, environmental impact, and future scope of these advanced polymeric nanocomposite membrane based systems for water and wastewater treatment applications.

Antibacterial and Antifouling Efficiency of Essential Oils-Loaded Electrospun Polyvinylidene Difluoride Membranes

Nanofibers have become a promising material in many industries in recent years, mainly due to their various properties. The only disadvantage of nanofibers as a potential filtration membrane is their short life due to clogging by bacteria in water treatment. The enrichment of nanofibers with active molecules could prevent these negative effects, represented by essential oils components such as Thymol, Eugenol, Linalool, Cinnamaldehyde and Carvacrol. Our study deals with the preparation of electrospun polyvinylidene difluoride (PVDF)-based nanofibers with incorporated essential oils, their characterization, testing their antibacterial properties and the evaluation of biofilm formation on the membrane surface. The study of the nanofibers' morphology points to the nanofibers' diverse fiber diameters ranging from 570 to 900 nm. Besides that, the nanofibers were detected as hydrophobic material with wettability over 130°. The satisfactory results of PVDF membranes were observed in nanofibers enriched with Thymol and Eugenol that showed their antifouling activity against the tested bacteria Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923. Therefore, these PVDF membranes could find potential applications as filtration membranes in healthcare or the environment.

Bibliometrics of Functional Polymeric Biomaterials with Bioactive Properties Prepared by Radiation-Induced Graft Copolymerisation: A Review

Functional polymeric biomaterials (FPBMs) with bioactive characteristics obtained by radiation-induced graft copolymerisation (RIGC) have been subjected to intensive research and developed into many commercial products. Various studies have reported the development of a variety of radiation-grafted FPBMs. However, no reports dealing with the quantitative evaluations of these studies from a global bibliographic perspective have been published. Such bibliographic analysis can provide information to overcome the limitations of the databases and identify the main research trends, together with challenges and future directions. This review aims to provide an unprecedented bibliometric analysis of the published literature on the use of RIGC for the preparation of FPBMs and their applications in medical, biomedical, biotechnological, and health care fields. A total of 235 publications obtained from the Web of Science (WoS) in the period of 1985-2021 were retrieved, screened, and evaluated. The records were used to manifest the contributions to each field and underline not only the top authors, journals, citations, years of publication, and countries but also to highlight the core research topics and the hubs for research excellence on these materials. The obtained data overviews are likely to provide guides to early-career scientists and their research institutions and promote the development of new, timely needed radiation-grafted FPBMs, in addition to extending their applications.

Membranes Based on Polyvinylidene Fluoride and Radiation-Grafted Sulfonated Polystyrene and Their Performance in Proton-Exchange Membrane Fuel Cells

Proton-exchange membranes based on gamma-irradiated films of PVDF and radiation-grafted sulfonated polystyrene with an ion-exchange capacity of 1.8 meq/g and crosslinking degrees of 0 and 3% were synthesized. A solvent-free, environmentally friendly method of styrene grafting from its aqueous emulsion, with a styrene content of only 5 vol.% was used. Energy dispersive X-ray mapping analysis showed that the grafted sulfonated polystyrene is uniformly distributed throughout the membrane thickness. The obtained materials had a proton conductivity up to 132 mS/cm at 80 °C and a hydrogen permeability of up to 5.2 cm²/s at 30 °C, which significantly exceeded similar values for Nafion^®-212 membranes. The resulting membranes exhibited a H₂/O₂ fuel cell peak power density of up to 0.4 W/cm² at 65 °C. Accelerated stability tests showed that adding a crosslinking agent could significantly increase the stability of the membranes in the fuel cells. The thermal properties and crystallinity of the membranes were investigated through differential scanning calorimetry and X-ray powder diffraction methods. The conductivity, water uptake, and mechanical properties of the membranes (stress–strain curves) were also characterized.

Fouling Prevention in Polymeric Membranes by Radiation Induced Graft Copolymerization

The application of membrane processes in various fields has now undergone accelerated developments, despite the presence of some hurdles impacting the process efficiency. Fouling is arguably the main hindrance for a wider implementation of polymeric membranes, particularly in pressure-driven membrane processes, causing higher costs of energy, operation, and maintenance. Radiation induced graft copolymerization (RIGC) is a powerful versatile technique for covalently imparting selected chemical functionalities to membranes' surfaces, providing a potential solution to fouling problems. This article aims to systematically review the progress in modifications of polymeric membranes by RIGC of polar monomers onto membranes using various low- and high-energy radiation sources (UV, plasma, γ-rays, and electron beam) for fouling prevention. The feasibility of the modification method with respect to physico-chemical and antifouling properties of the membrane is discussed. Furthermore, the major challenges to the modified membranes in terms of sustainability are outlined and the future research directions are also highlighted. It is expected that this review would attract the attention of membrane developers, users, researchers, and scientists to appreciate the merits of using RIGC for modifying polymeric membranes to mitigate the fouling issue, increase membrane lifespan, and enhance the membrane system efficiency.

Non-Equilibrium Plasma Methods for Tailoring Surface Properties of Polyvinylidene Fluoride: Review and Challenges

Modification and functionalization of polymer surface properties is desired in numerous applications, and a standard technique is a treatment with non-equilibrium gaseous plasma. Fluorinated polymers exhibit specific properties and are regarded as difficult to functionalize with polar functional groups. Plasma methods for functionalization of polyvinylidene fluoride (PVDF) are reviewed and different mechanisms involved in the surface modification are presented and explained by the interaction of various reactive species and far ultraviolet radiation. Most authors used argon plasma but reported various results. The discrepancy between the reported results is explained by peculiarities of the experimental systems and illustrated by three mechanisms. More versatile reaction mechanisms were reported by authors who used oxygen plasma for surface modification of PVDF, while plasma sustained in other gases was rarely used. The results reported by various authors are analyzed, and correlations are drawn where feasible. The processing parameters reported by different authors were the gas pressure and purity, the discharge configuration and power, while the surface finish was predominantly determined by X-ray photoelectron spectroscopy (XPS) and static water contact angle (WCA). A reasonably good correlation was found between the surface wettability as probed by WCA and the oxygen concentration as probed by XPS, but there is hardly any correlation between the discharge parameters and the wettability.

In Vitro Effect of Replicated Porous Polymeric Nano-MicroStructured Biointerfaces Characteristics on Macrophages Behavior

In the last decades, optimizing implant properties in terms of materials and biointerface characteristics represents one of the main quests in biomedical research. Modifying and engineering polyvinylidene fluoride (PVDF) as scaffolds becomes more and more attractive to multiples areas of bio-applications (e.g., bone or cochlear implants). Nevertheless, the acceptance of an implant is affected by its inflammatory potency caused by surface-induced modification. Therefore, in this work, three types of nano-micro squared wells like PVDF structures (i.e., reversed pyramidal shape with depths from 0.8 to 2.5 microns) were obtained by replication, and the influence of their characteristics on the inflammatory response of human macrophages was investigated in vitro. FTIR and X-ray photoelectron spectroscopy analysis confirmed the maintaining chemical structures of the replicated surfaces, while the topographical surface characteristics were evaluated by AFM and SEM analysis. Contact angle and surface energy analysis indicated a modification from superhydrophobicity of casted materials to moderate hydrophobicity based on the structure's depth change. The effects induced by PVDF casted and micron-sized reversed pyramidal replicas on macrophages behavior were evaluated in normal and inflammatory conditions (lipopolysaccharide treatment) using colorimetric, microscopy, and ELISA methods. Our results demonstrate that the depth of the microstructured surface affects the activity of macrophages and that the modification of topography could influence both the hydrophobicity of the surface and the inflammatory response.

Activation of different C–F bonds in fluoropolymers for Cu(0)-mediated single electron transfer radical polymerization

The graft polymerization of MMA initiated from PVDF-based fluoropolymers via single electron transfer controlled radical polymerization (SET-CRP) is reported.

Efficient removal of mercury ions with MoS2-nanosheet-decorated PVDF composite adsorption membrane

The exploitation of a new adsorbent with a high adsorption performance and recyclability is of great practical significance for the treatment of wastewater containing mercury ions. In this study, a novel membrane adsorbent was fabricated by blending MoS₂ nanosheets into a PVDF polymer matrix (P-PVDF/MoS₂) followed by non-solvent-induced phase conversion. This material was able to bind mercury ions and was not affected by the solution ionic strength, co-existing anions, or interfering heavy metal ions. The optimal pH range for mercury ion elimination was 4.5-6.0, and P-PVDF/MoS₂ exhibited a maximum adsorption capacity of 578 mg g^-1. The pseudo-second-order adsorption kinetics and Langmuir isotherm models best described the adsorption process. The adsorption mechanism was mainly monolayer chemisorption, for which the S groups were the major active sites. Furthermore, the membrane could be removed from the aqueous solution easily using tweezers, and the removal efficiency of mercury ions remained over 90% after ten cycles. This study suggests that the inexpensive and recyclable P-PVDF/MoS₂ membranes can be used for the efficient removal of heavy metal ions from wastewater at a large scale.

Antifouling Membranes Prepared from Polyethersulfone Grafted with Poly(ethylene glycol) Methacrylate by Radiation-Induced Copolymerization in Homogeneous Solution

To synthesize evenly grafted copolymers, gamma radiation of homogeneous solutions was employed to graft poly(ethylene glycol) methacrylate (PEGMA) onto polyethersulfone (PES). The grafting was verified by Fourier transform infrared spectroscopy, and the degrees of grafting (DGs) were determined by elementary analysis. The PES-g-polyPEGMA copolymers with different DGs were obtained by changing the monomer concentration. Membranes were cast from pristine PES, PES/PEG blends, and PES-g-polyPEGMA with different DGs, respectively, via nonsolvent-induced phase separation. Results from water contact angle measurements and scanning electron microscopy analysis indicated that increasing DGs led to PES-g-polyPEGMA membranes with increasing hydrophilicity and porousness. Filtration experimental results showed that increasing DGs without adding pore-forming agents caused PES-g-polyPEGMA membranes with higher permeability. Compared with PES/PEG membranes with analogous permeation characteristics, in which PEG is added as a pore-forming agent, PES-g-polyPEGMA membranes exhibited superior antifouling properties.

Manipulation of cellular behaviour on surface-modified polyvinylidene difluoride using wet chemistry

The surface modification of polyvinylidene difluoride (PVDF) for various biomedical uses is notoriously hampered by the chemical inertness of the polymer. A wet chemical approach aiming at covalently grafting biomolecules was demonstrated by means of an elimination reaction of fluorine from the polymer backbone followed by subsequent modification steps. Exemplified as a possible biological application, the coupling of the peptide REDV rendered the material adhesive for endothelial cells while adhesion of thrombocytes was dramatically reduced.

Assessing the Performance of Thin-Film Nanofiltration Membranes with Embedded Montmorillonites

In this study, the basal spacing of montmorillonite (MMT) was modified through ion exchange. Two kinds of MMT were used: sodium-modified MMT (Na-MMT) and organo-modified MMT (O-MMT). These two particles were incorporated separately into the thin-film nanocomposite polyamide membrane through the interfacial polymerization of piperazine and trimesoyl chloride in n-hexane. The membrane with O-MMT (TFNO-MMT) has a more hydrophilic surface compared to that of membrane with Na-MMT (TFNNa-MMT). When various types of MMT were dispersed in the n-hexane solution with trimesoyl chloride (TMC), O-MMT was well-dispersed than Na-MMT. The poor dispersion of Na-MMT in n-hexane led to the aggregation of Na-MMT on the surface of TFNNa-MMT. TFNO-MMT displayed a uniform distribution of O-MMT on the surface, because O-MMT was well-dispersed in n-hexane. In comparison with the pristine and TFNNa-MMT membranes, TFNO-MMT delivered the highest pure water flux of 53.15 ± 3.30 L∙m-2∙h-1 at 6 bar, while its salt rejection for divalent ions remained at 95%-99%. Furthermore, it had stable performance in wide operating condition, and it exhibited a magnificent antifouling property. Therefore, a suitable type of MMT could lead to high separation efficiency.

Antifouling and antibacterial evaluation of ZnO/MWCNT dual nanofiller polyethersulfone mixed matrix membrane

The aim of this study is to evaluate the performance and antifouling properties of polyethersulfone (PES) membrane incorporated with dual nanofiller, zinc oxide (ZnO) and multi-walled carbon nanotube (MWCNT). The synergistic effect of the these nanofillers in PES membrane is studied by blending different ratio of ZnO/MWCNT nanofiller into the PES membrane. The fabricated membranes were characterized in terms of cross-section and surface morphology, surface hydrophilicity, pore size and porosity. The filtration performance of the membranes was tested using 50 mg/L humic acid (HA) solution as model solution. SEM image and gravimetric evaluation reported that the incorporation of both MWCNT and ZnO into the PES membrane improved porosity significantly up to 46.02%. Lower water contact angle of PES membrane incorporated with equal ratio of MWCNT and ZnO (PES 3) revealed that it has neat PES membrane properties and more hydrophilic membrane surface than single filler. PES 3 outperform other membranes with excellent HA permeate flux of 40.00 L/m².h and rejection of 88.51%. Due to hydrophilic membrane surface, PES 3 membrane demonstrate efficient antifouling properties with lower relative flux reduction (RFR) and higher flux recovery ratio (FRR). PES 3 also showed notable antibacterial properties with less bacterial attached to the membrane compared to neat PES membrane (PES 0).

Cleavage of the Graft Bonds in PVDF-g-St Films by Boiling Xylene Extraction and the Determination of the Molecular Weight of the Graft Chains

To determine the molecular weight of graft chains in grafted films, the polystyrene graft chains of PVDF-g-St films synthesized by a pre-irradiation graft method are cleaved and separated by boiling xylene extraction. The analysis of the extracted material and the residual films by FTIR, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) analyses indicates that most graft chains are removed from the PVDF-g-St films within 72 h of extraction time. Furthermore, the molecular weight of the residual films decreases quickly within 8 h of extraction and then remains virtually unchanged up to 72 h after extraction time. The degradation is due to the cleavage of graft bonds, which is mainly driven by the thermal degradation and the swelling of graft chains in solution. This allows determination of the molecular weight of graft chains by GPC analysis of the extracted material. The results indicate that the PVDF-g-St prepared in this study has the structure where one or two graft chains hang from each PVDF backbone.

A facile method to modify polypropylene membrane by polydopamine coating via inkjet printing technique for superior performance

Membrane surface functionalization based on mussel-inspired polydopamine (PDA) deposition for enhancing antifouling ability has attracted considerable attention. However, high cost of dopamine (DA) and long-time of reaction during self-polymerization of DA in aqueous solution remain the major problems impeding its practical application. This study provided a first report on a low-cost and facile membrane modification approach based on inkjet printing of DA and sodium periodate (SP) to rapidly deposit PDA on polypropylene (PP) membrane. Compared with the pristine PP membrane and DA printed PP membrane, the PDA-SP coated PP membrane demonstrated superior hydrophilicity (67.2°), high pure water permeability (2156.8 L·m^-2·h^-1) and antifouling property, due to the improved oxidation degree of PDA. Moreover, the modified membrane possesses good chemical stability in aqueous solution over the wide range of pH 2-9. The inkjet printing integrated oxidant-induced mussel-inspired modification proposed in this study is substrate-independent, and can be applied to various geometries and materials, showing broad application prospects in membrane fabrication.

Enhancing the Antifouling Properties of Poly(vinylidene fluoride) (PVDF) Membrane through a Novel Blending and Surface-Grafting Modification Approach

In this study, poly(vinylidene fluoride) (PVDF) membrane was modified through a novel approach by first blending an active component (poly(vinylidene fluoride-co-chlorotrifluoroethylene), P(VDF-co-CTFE)) with the PVDF base material, followed by surface grafting of the membrane on the active component to obtain a triblock copolymer functional structure. The prepared membranes were characterized by various analyses, including Fourier-transform infrared, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscope, and filtration tests. It was found that the modified membrane surface showed a much better hydrophilicity (water contact angle of 67.3°) and oleophobicity (oil contact angle of 129.7°). The modification reduced the average surface pore size (from 0.1495 to 0.1072 μm) and thus lowered the pure water flux (from 364.0 to 224.6 L m^-2 h^-1 at 0.10 MPa of transmembrane pressure), but significantly increased the relative flux recovery (RFR) and the retention efficiency of the modified membrane during the filtration of bovine serum albumin solution and oil/water emulsion. For example, the modified membranes showed 98.6% oil retention (at feed concentration of 0.4 g L^-1), 92.7% RFR by simple water flushing after filtration, and a consistently high oil removal of 96% or above during a five-cycle-continuous filtration test, as compared to 30.4% oil retention and 51.8% RFR for unmodified PVDF/P(VDF-co-CTFE) blend membrane.

Polysulfone/Polyamide-SiO₂ Composite Membrane with High Permeance for Organic Solvent Nanofiltration

To improve the filtration performance and properties of organic solvent nanofiltration (OSN) membranes, we firstly introduce nanoporous silica (SiO₂) particles into the polyamide (PA) active layer of polysulfone (PSf) membrane via an interfacial polymerization process. Results from the study revealed that introduction of SiO₂ influenced the properties of PSf/PA-SiO₂ composite membranes by changing the surface roughness and hydrophilicity. Moreover, results also indicated that nanoporous SiO₂ modified membranes showed an improved performance of alcohols solvent permeance. The PSf/PA-SiO₂ composite membrane modified by 0.025 wt % of SiO₂ reached a permeance of 3.29 L m⁻² h⁻¹ bar⁻¹ for methanol and 0.42 L m⁻² h⁻¹ bar⁻¹ for ethanol, which were 20.0% and 13.5% higher than the control PSf membrane (permeance of 2.74 L m⁻² h⁻¹ bar⁻¹ for methanol and 0.37 L m⁻² h⁻¹ bar⁻¹ for ethanol). Conclusively, we demonstrated that the increase of membrane hydrophilicity and roughness were major factors contributing to the improved alcohols solvent permeance of the membranes.

Preparation and Characterization of TiO₂/g-C₃N₄/PVDF Composite Membrane with Enhanced Physical Properties

TiO₂/g-C₃N₄/PVDF composite membranes were prepared by a phase inversion method. A comparison of the performance and morphology was carried out among pure PVDF, g-C₃N₄/PVDF, TiO₂/PVDF and TiO₂/g-C₃N₄/PVDF composite membranes. The results of permeability and instrumental analysis indicated that TiO₂ and g-C₃N₄ organic-inorganic composites obviously changed the performance and structure of the PVDF membranes. The porosity and water content of 0.75TiO₂/0.25g-C₃N₄/PVDF composite membranes were 97.3 and 188.3 L/(m²·h), respectively. The porosity and water content of the 0.75TiO₂/0.25g-C₃N₄ membranes were increased by 20.8% and 27.4%, respectively, compared with that of pure PVDF membranes. This suggested that the combination of organic-inorganic composite with PVDF could remarkably improve UTS, membrane porosity and water content.

Graphene, electrospun membranes and granular activated carbon for eliminating heavy metals, pesticides and bacteria in water and wastewater treatment processes

The availability of safe water has a significant impact on all parts of society, its growth and sustainability, both politically and socioeconomically.

Effects of fractal roughness of membrane surfaces on interfacial interactions associated with membrane fouling in a membrane bioreactor

Fractal roughness is one of the most important properties of a fractal surface. In this study, it was found that, randomly rough membrane surface was a fractal surface, which could be digitally modeled by a modified two-variable Weierstrass-Mandelbrot (WM) function. Fractal roughness of membrane surfaces has a typical power function relation with the statistical roughness of the modeled surface. Assessment of interfacial interactions showed that an increase in fractal roughness of membrane surfaces will strengthen and prolong the interfacial interactions between membranes and foulants, and under conditions in this study, will significantly increase the adhesion propensity of a foulant particle on membrane surface. This interesting result can be attributed to that increase in fractal roughness simultaneously improves separation distance and interaction surface area for adhesion of a foulant particle. This study gives deep insights into interfacial interactions and membrane fouling in MBRs.