Pristine Membrane Research Articles

Fouling mitigation of microcrystalline cellulose-blended poly(vinylidene fluoride) membranes in protein separation

ABSTRACT Modifications of polymeric membranes are necessary to improve the membrane characteristics. The composite membrane of Poly(vinylidene fluoride)_Microcrystalline cellulose (PVDF_MCC) was prepared using dimethylacetamide/lithium chloride (DMAc/LiCl) as co-solvent to dissolve the MCC in the casting solution. The prepared membrane was characterized by using the FTIR, SEM, contact angle, and the water permeates flux. The improvement of hydrophilicity and pore structure with the incorporation of MCC was observed which led to the increment of the water and permeate flux. Indication from the rheological study suggested that the casting solutions with MCC presented the influence on the composite membrane’s pore structure as a significant viscosity increment was observed. This can be examined from the larger pore and elongated finger-like structure of the membrane morphology compared to the pristine membrane. The rejection rate of the protein increased from 85% to 97% after the incorporation of MCC in the PVDF membrane. The utilization of a low-cost and environmentally friendly additive that MCC has to offer helps to improve the antifouling properties of PVDF membranes for the efficient removal of BSA in water.

Preparation of KH560‐UiO‐66‐NH2/Pebax mixed matrix membranes and CO2 separation

AbstractMetal–organic frame UiO‐66‐NH2 was modified by 3‐glycidyl ether oxypropyl trimethoxysilane (KH560), and KH560‐UiO‐66‐NH2 was synthetized and added to Pebax to prepare KH560‐UiO‐66‐NH2/Pebax mixed matrix membranes (MMMs). The epoxy group of KH560 had an amine‐epoxidation reaction with the NH2 in UiO‐66‐NH2, which prevented UiO‐66‐NH2 from agglutinating in the MMMs. In addition, the NH bond and OH bond of KH560‐UiO‐66‐NH2 could theoretically form hydrogen bonds with CO and NH bonds in the main chain of polymerization, respectively, so as to improve the interfacial compatibility between fillers and polymers. The structure and properties of the filler particles and MMMs were evaluated by Fourier transform infrared spectrometer, x‐ray diffraction, scanning electron microscopy, and thermogravimetric analyzer. The results showed that the filler particles were successfully synthesized, and had good crystallinity, uniform size distribution, and good thermal stability. The inorganic and organic interfaces of MMMs had no obvious interface defects. The obtained KH560‐UiO‐66‐NH2/Pebax MMMs showed CO2 permeability of 111.52 Barre and CO2/N2 selectivity of 92.16, which were 85.65% and 88.73% higher than that of pristine membranes, respectively. The gas separation performance of MMMs was significantly improved, exceeding the upper bound of 2008 Robeson.

Engineering polyvinylidene fluoride membranes using charge tunable dendrimer polyamidoamine to enable microporous membranes for protein separation

Dendrimers are structurally precise molecules, whose peripheral layer provides ample sites for anchoring functional groups of different charges and charge densities. This characteristic renders them capability of providing numerous target functional groups on the surface of filtration membranes when modified by dendrimers. Consequently, there has been a growing interest in dendrimer-modified membranes. In this study, we investigated the engineering of polyvinylidene fluoride (PVDF) membranes using polyamidoamine (PAMAM) dendrimers anchoring different functional groups to tune the charges and charge density of membranes to enable microporous membranes for separation of charged macromolecules. PVDF membranes were functionalized by grafting PAMAM-G3.0 (generation 3) dendrimers with amine groups onto their surfaces and internal surfaces of membrane pores. Subsequently, the peripheral functional groups of dendrimers on the membranes were replaced by carboxyl groups, quaternary ammonium groups, or sulfonic acid groups for charges of different nature and densities. Surface chemical properties, electrical properties, and morphology were characterized using various techniques, including attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and surface zeta potential measurement. The filtration performance of both PVDF and modified membranes was evaluated using polyethylene oxide (PEO), polyacrylic acid (PAA), and whey protein filtration. Among the modified membranes, the G3PA membranes, with carboxyl functional groups, exhibited the most effective whey protein separation performance. The whey protein rejection and permeate flux of the G3PA membranes were 79 % and 30.3 LMH, respectively. As a comparison, the whey protein rejection and permeate flux of the pristine PVDF membranes were 58.9 % and 15.3 LMH, respectively.

Comparative Analysis of the Impact of Protein on Virus Retention for Different Virus Removal Filters.

The performance of virus filters is often determined by the extent of protein fouling, which can affect both filtrate flux and virus retention. However, the mechanisms governing changes in virus retention in the presence of proteins are still not well understood. The objective of this work was to examine the effect of proteins on virus retention by both asymmetric (Viresolve® NFP and Viresolve® Pro) and relatively homogeneous (Ultipor® DV20 and PegasusTM SV4) virus filtration membranes. Experiments were performed with bacteriophage ϕX174 as a model parvovirus and human serum immunoglobulin G (hIgG) as a model protein. The virus retention in 1 g/L hIgG solutions was consistently less than that in a protein-free buffer solution by between 1 to 3 logs for the different virus filters. The virus retention profiles for the two homogeneous membranes were very similar, with the virus retention being highly correlated with the extent of flux decline. Membranes prefouled with hIgG and then challenged with phages also showed much lower virus retention, demonstrating the importance of membrane fouling; the one exception was the Viresolve® Pro membrane, which showed a similar virus retention for the prefouled and pristine membranes. Experiments in which the protein was filtered after the virus challenge demonstrated that hIgG can displace previously captured viruses from within a filter. The magnitude of these effects significantly varied for the different virus filters, likely due to differences in membrane morphology, pore size distribution, and chemistry, providing important insights into the development/application of virus filtration in bioprocessing.

Simultaneous enhanced antibiotic pollutants removal and sustained permeability of the membrane involving CoFe2O4/MoS2 catalyst initiated with simple H2O2 backwashing

Membranes for wastewater treatment should ideally exhibit sustainable high permeate production, enhanced pollutant removal, and intrinsic physical rejection. In this study, CoFe2O4/MoS2 serves as a non-homogeneous phase catalyst; it is combined with polyether sulfone membranes via liquid-induced phase separation to simultaneously sustain membrane permeability and enhance antibiotic pollutant degradation. The prepared catalytic membranes have higher pure water flux (329.34 L m−2 h−1) than pristine polyethersulfone membranes (219.03 L m−2 h−1), as well as higher mean pore size, porosity, and hydrophilicity. Under a moderate transmembrane pressure (0.05 MPa), tetracycline (TC) in synthetic and real wastewater was degraded by the optimal catalytic membrane by 72.7 % and 91.2 %, respectively. Owing to the generation of the reactive oxygen species (ROS) during the Fenton-like reaction process, the catalytic membrane could exclude the natural organics during the H2O2 backwash step and selectively promote fouling degradation in the membrane channel. The irreversible fouling ratio of the catalyzed membrane was significantly reduced, and the flux recovery rate increased by up to 91.6 %. A potential catalytic mechanism and TC degradation pathways were proposed. This study offers valuable insights for designing catalytic membranes with enhanced filtration performance.

Improved Proton Conductivity of Chitosan-Based Composite Proton Exchange Membrane Reinforced by Modified GO Inorganic Nanofillers.

Non-fluorinated chitosan-based proton exchange membranes (PEMs) have been attracting considerable interest due to their environmental friendliness and relatively low cost. However, low proton conductivity and poor physicochemical properties have limited their application in fuel cells. In this work, a reinforced nanofiller (sulfonated CS/GO, S-CS/GO) is accomplished, for the first time, via a facile amidation and sulfonation reaction. Novel chitosan-based composite PEMs are successfully constructed by the incorporation of the nanofiller into the chitosan matrix. Additionally, the effects of the type and amount of the nanofillers on physicochemical and electrochemical properties are further investigated. It is demonstrated that the chitosan-based composite PEMs incorporating an appropriate amount of the nanofillers (9 wt.%) exhibit good membrane-forming ability, physicochemical properties, improved proton conductivity, and low methanol permeability even under a high temperature and low humidity environment. When the incorporated amounts of S-CS/GO are 9 wt.%, the proton conductivity of the composite PEMs was up to 0.032 S/cm but methanol permeability was decreased to 1.42 × 10-7 cm2/s. Compared to a pristine CS membrane, the tensile strength of the composite membrane is improved by 98% and the methanol permeability is reduced by 51%.

Terminal conversion of polyamide membranes by homologous monomer vapors for chlorine-resistant desalination

Water scarcity is a global challenge and severely threatens human development. Membrane desalination shows great potential for producing freshwater from saltwater to alleviate this crisis. However, the dominating polyamide membranes suffer from the issue of poor chlorine resistance, which cause performance deterioration and shortens membrane lifespan. In this study, we report a concept of terminal conversion to design high-performance, antifouling, and especially chlorine-resistant polyamide desalination membranes. This amino-to-carboxyl conversion of commercial membranes can be simply performed by controllable and scalable chemical vapor deposition through exposure in homologous monomer vapor and hydrolysis of unreacted acyl chloride groups. We demonstrate that this conversion not only adjust the electronegativity and hydrophilicity of membranes to boost fouling resistance and reverse osmosis performance, but also tune the reactivity and electron cloud distribution of polyamide networks to restrain chlorine accessibility and substantially improve anti-chlorination property. After extreme chlorination for 240000 ppm h, the resultant membranes show limited rejection decline of only 7.2 %. For high-salinity (35000 ppm) and high-pressure (38 bar) desalination, the modified membranes before and after chlorination for 144000 ppm h still exhibit rejection of 94.5 % and 90.0 % and flux of 75.2 and 71.4 L m−2 h−1, respectively, which are much better than those of the pristine membranes (89.6 % and 63.5 %, and 64.2 and 57.5 L m−2 h−1). Our findings pave an alternative mechanism and strategy to reconstruct polyamide membranes for efficient water desalination.

Au-TiO2 nanoparticles enabled catalytic treatment of oil and gas produced water in slurry and vacuum membrane distillation systems

Produced water (PW) treatment and reuse provide a promising alternative to address freshwater scarcity and reduce the environmental impacts associated with PW disposal. Efficient treatment of PW is challenging due to its complex matrix and hypersalinity. This study developed innovative gold-doped titania (Au-TiO2) nanoparticles to enable effective treatment of PW collected from the Permian Basin with salinity of ∼118 g/L. The mechanisms of removing organics and ammonia in PW in slurry and vacuum membrane distillation (VMD) systems were investigated via thermocatalysis, photocatalysis, and photo-thermocatalysis. Photocatalysis and photo-thermocatalysis were found more effective for organic removal than thermocatalysis. A baseline study using glucose as a representative of easily degradable organic carbon showed that thermocatalysis and photocatalysis mineralized 23.2 % and 93.1 % glucose, respectively. However, photo-thermocatalysis and thermocatalysis degraded only 17.4 % and 7.5 % dissolved organic carbon (DOC), and 56.2 % and 49.2 % NH3-N in PW, respectively. Au-TiO2 coating on ceramic membranes improved the distillate flux of photo-thermocatalytic membrane distillation (PMD) compared to no catalysts coating in VMD (7.14 versus 6.75 kg per hour per m2). Both PMD and VMD rejected >99.9 % of salts and >96 % DOC, and PMD had slightly higher DOC and salt removal rates. In contrast, normalized permeate flux using pristine membranes (hydrophobically modified without catalysts coating) decreased to zero after 29 h of operation while normalized flux with TiO2-coated membranes under UV on and UV off were 57.5 % and 53.7 % on average, which is much lower than that with Au-TiO2 coated membranes in both UV on (91.3 %) and UV off (88.1 %) cases, indicating Au-TiO2 coating significantly improved membrane anti-fouling propensity and durability during treatment of complex PW. Targeted analysis of three groups of petroleum hydrocarbons and 70 volatile organic compounds showed that only 2-butanone and acetone were detected in the distillates with removal efficiencies of 80 % for 2-butanone in both PMD and VMD, and acetone was removed by 75.4 % in PMD and 69.2 % in VMD. Au-TiO2 nanoparticles demonstrated excellent catalytic performance for PW treatment in slurry and immobilized PMD systems.

Silk fibroin-graphene oxide composite membranes for selective separation of ions and molecules from water

Nanofiltration membranes with controlled pores are useful in many fields, such as pharmaceuticals, desalination, petroleum, and food processing. Recently, graphene oxide has emerged as a promising candidate for the fabrication of highly efficient and pressure-resistant nanofiltration membranes with excellent water permeability and solute rejection. However, it remains difficult to achieve increased permeability while maintaining excellent separation ability. Herein, we report a novel silk fibroin-graphene oxide (FGO) composite membrane prepared by using fibroin as a cross-link reagent, which is extracted from natural Bombyx mori silkworm cocoons. Such a FGO membrane shows a pure water permeance of ∼280 L m−2 h−1 bar−1, which is five times greater than previously reported GO-based membranes. Further, such a membrane also exhibits excellent separation efficiency (> 99 %) for different feed molecules. Additionally, these membranes exhibit high chemical stability in water, acidic and basic solutions for several days compared to pristine GO membranes.

Superhydrophobic and oleophobic Nylon, PES and PVDF membranes using plasma nanotexturing: Empowering membrane distillation and contributing to PFAS free hydrophobic membranes

As freshwater demand is constantly increasing, water purification via membrane distillation (MD) emerges as a promising water production technology, especially when combined with the use of superhydrophobic membranes. Here, following our previous work [1] we extend our universal, environmentally friendly, plasma nanotexturing and hydrophobization technology for rendering practically any type of membrane superhydrophobic and oleophobic. Thus, we render three commercial porous membranes superhydrophobic, namely, polyvinylidene (PVDF 0.45 μm) (initially hydrophobic), polyethersulfone (PES 1.20 μm) and nylon (NY 1.20 μm) (both initially hydrophilic). We demonstrate superhydrophobic, superoleophobic (down to 40mn/m surface tension) and oleophobic properties (down to 30mN/m surface tension) for PVDF, PES and Nylon membranes thus paving the way for their use with low surface tension waste streams. Moreover, the technology presented herein not only improves existing hydrophobic membranes but may lead to elimination of the use of Teflon-like fluorinated hydrophobic membranes altogether in the future, thereby contributing to the PFAS (Per and Poly Fluoro Alkyl Substances) and Teflon-like membrane use reduction. We subsequently evaluated the performance of the treated membranes in direct contact membrane distillation (DCMD) for desalination of sea-like water (35 g/L NaCl). All membranes showed enhanced water flux with an increase of >13% compared to the pristine hydrophobic PVDF membranes for at least 2 h of continuous operation, with salt rejection exciding 99.99%.

Zwitterionic nanospheres engineered co-polymer composite membrane for precise protein-protein separation via dynamic self-assembly micelle deposition

The accurate protein-protein separation is important but technically challenging. Achieving such a precise separation using membrane requires the selective channels with appropriate pore geometry structure and high anti-fouling property. In this study, polyethersulfone-b-poly(sulfobetaine methyl methacrylate) (PES-b-PSBMA) was synthesized and engineered onto polysulfone (PSF) ultrafiltration (UF) membrane to fabricate zwitterionic nanospheres engineered co-polymer (ZN-e-CoP) composite membrane via dynamic self-assembly micelle deposition. On the one hand, self-assembly zwitterionic nanospheres were used as blocks to construct hydrophilic layers with size-dependent sieving channels, endowing ZN-e-CoP composite membranes with enhanced permselectivity and protein-protein separation abilities, meanwhile zwitterionic groups from nanospheres reinforced the structure stability of nanospheres/nanospheres and nanospheres/membrane via multiple intermolecular interactions. On the other hand, zwitterionic nanospheres can induce to produce the hydration layer enveloping themselves by binding water molecules, where hydration layer acts as a protective barrier on the membrane surface, impeding the protein adhesion. Hence, ZN-e-CoP_1a composite membrane exhibited superior separation properties with Lysozyme/Bovine Serum Albumin (BSA) separation factor of 18.1 and 95.4 % rejection against BSA, 10.1 and 2.3 times, respectively, higher these of pristine PSF membrane (1.8 and 42.1 %), without obviously sacrificing water flux. Simultaneously, hydration layer enables the ZN-e-CoP_1a membrane with enhanced anti-fouling performance and durability during the long-term operations. The proposed approach opens new pathways to fabricate excellent anti-fouling membranes for precise protein-protein separation.

Boosting carbon capture with CO2-Ultrapermeable molecularly imprinted membranes

Mixed matrix membrane (MMM) is one of the most promising candidates for exceeding the gas separation upper bound, while fillers can largely determine their ultimate performance. The molecular imprinting technique was first employed to prepare a layer containing rich CO2 adsorption sites on the UiO-66-NH2 surface for fabricating highly CO2-permeable PIM-1-based MMMs with higher selectivity. Transmission electron microscopy (TEM) and element mapping confirmed the successful formation of the core-shell structure for the imprinted metal-organic frameworks (MOFs). The MMMs prepared with imprinted MOFs present enhanced CO2 permeability and CO2/N2 selectivity, higher compatibility between polymers and fillers, and better mechanical strength compared to the MMMs with the pristine UiO-66-NH2. The MMMs formed with 5 wt% imprinted MOFs showed superior CO2/N2 separation performance beyond the 2019 upper bound with an ultrahigh CO2 permeability of 13,000 barrer (increased twice compared to pristine PIM-1 membrane). Moreover, with a filler content of 13 wt%, the obtained membrane maintains good mechanical properties, which indicates the benefit of the imprinted layer for the improvement of the filler loading inside a PIM-1 matrix. The membranes showed decreased CO2 permeability and CO2/N2 selectivity under the wet conditions, but stable performances over 46 hours of dynamic testing. The results indicate the presented approach for filler modification via molecular imprinting is a promising strategy for the enhancement of the MMM separation performance.

2-Mercaptoethanesulfonic Acid as an Effective Free-Radical Scavenger in Perfluorosulfonic Acid Membrane-Based Polymer Electrolyte Membrane Fuel Cells

Ceria nanoparticle-based free-radical scavengers for the mitigation of oxidative damage in perfluorosulfonic acid (PFSA)-based polymer electrolyte membrane fuel cells (PEMFCs) suffer from the drawbacks of lowered protonic conductivity and leaching in the acidic environment of a PEMFC. As an alternative to ceria, here we demonstrate that oxidative damage can be mitigated by functionalization of Nafion with 2-Mercaptoethanesulfonic acid (MESA) in different (0.1–1.0 wt%) ratio. The spectroscopic investigation indicated successful functionalization of MESA over the Nafion chain and resulting Nafion-MESA composite membranes displayed improved hydration and swelling behavior, and thermal and mechanical properties. At ≤60 °C (95% relative humidity), the protonic conductivity of composite membranes was higher than/equivalent to that of pristine Nafion membrane; however, at ≥70 °C it was ∼6%–8% lower. At 80 °C, conductivity of Nafion-MESA-0.1 wt%, Nafion-MESA-0.25 wt%, pristine Nafion, and state-of-the-art Nafion-CeO2−1wt% membranes were 1.72 × 10−1, 1.67 × 10−1, 1.8 × 10−1, and 1.6 × 10−1 S∙cm−1, respectively. The fluoride emission rate value for the same membranes were 0.30, 0.17, 1.39, and 0.27 mg∙g−1, respectively, thus indicating that Nafion-MESA membranes can substitute the ceria-based membranes as a chemically stable membrane electrolyte in PEMFCs.

Highly sensitive electron-beam-induced X-ray detection from liquid using SiNx membrane ultra-thinned by gas cluster ion beams

We aimed to improve the detection sensitivity for liquid measurement by developing an ultrathin photoelectron transmission window (SiNx membrane) for liquid cells via X-ray photoelectron spectroscopy or X-ray photoelectron emission microscopy at an ultrahigh vacuum. The membrane using gas-cluster ion beams (GCIB) was thinned, and its burst pressure was compared with those of membranes thinned with atomic 400 eV Ar+ ions. The SiNx membranes thinned by GCIB had approximately 2.5 times higher burst pressure than Ar+ ions. In addition, the improved sensitivity of the characteristic X-ray from liquid water induced by low-energy electrons was investigated. With the use of the 4.5 nm-thick SiNx membrane etched by GCIB, the X-ray intensity became 1.6 times higher than those of the 11 nm-thick pristine membrane at the electron beam (EB) energy of 1.5 keV. This result showed a good agreement with Monte Carlo simulation results of the EB-induced X-ray emission from liquid water beneath the SiNx membrane.

Modification of PVDF membranes using polyvinyl alcohol-crosslinked functionalized nano-silica sheets: High flux and antifouling properties for efficient oil-water separation

BackgroundsOily wastewater is the leading cause of water and environmental pollution, but conventional treatments suffer from complexity and low efficiency, and explicitly deal with oil-in-water emulsions. Polyvinylidene fluoride (PVDF) membranes have shown immense potential for separation applications; however, these membranes rapidly foul during the separation of oily wastewater. MethodsA simple method is introduced to improve the hydrophilicity of PVDF membranes by decorating their surfaces with acrylic acid-modified nano-silica (NS) nanoparticles, whose surface stability is achieved by crosslinking them with polyvinyl alcohol (PVA). Three distinct oils were employed in this study for oil–water emulsion analysis: vegetable oil, diesel oil, and petroleum ether oil. The antifouling abilities and characterization were elucidated using advanced analytical techniques. Significant findingsThe membrane surface became hydrophilic, and the water contact angle reduced from 64 ± 1.45o to 24.3 ± 1.75o. The NS-PVA-PVDF membrane exhibited the oleophobic behavior underwater, with an underwater oil contact angle of 147.6 ± 2.65o. Under optimized conditions, the NS-PVA-PVDF membranes have shown excellent rejection efficiency for different oil-in-water emulsions, including vegetable oil (99.01± 0.64 %), diesel oil (94.61± 0.26 %), and petroleum ether oil-in-water (84.53 ± 0.85 %) emulsions. For a membrane with a 1:3 ratio of PVA to NS particles, organic foulants like humic acid and dye elucidated better performance with 94.79 ± 1.11 and 92.79 ± 1.41 % removal, respectively, along with the flux recovery ratio of 0.96 and 0.92 for humic acid and dye filtration with irreversible fouling of 0.03 and 0.08, respectively. However, the long-term analysis of the optimum membranes showed an overall stable rejection efficiency of >95 % compared with the pristine membrane. The specific rejection efficiency varied for oil emulsion (44.67–50.14 %), humic acid (59.55–67.75 %), and for dye filtration (61.52–73.5 %). These results verify the potential of the modified NS-PVA-PVDF membrane for oil–water separation for practical applications.

Novel ultrastable 2D MOF/MXene nanofluidic membrane with ultralow resistance for highly efficient osmotic power harvesting

Two-dimensional (2D) materials have shown great potential in harvesting osmotic power due to their high membrane selectivity, but the high resistance from tortuous pathways of 2D nanofluidic membranes still impedes the further improvement in output performance. Here, we report an innovative 2D MXCT (MXene/Cu-TCPP) lamellar membrane with ultralow resistance for highly efficient osmotic power generation. The incorporation of 2D Ti3C2Tx MXene with rich functional groups not only resolves the water-stability issue of 2D metal-organic framework (MOF) Cu-TCPP, but provides large surface charges for selective ion transport. The orderly sub-2 nm framework channels of Cu-TCPP provide much shorter permeation pathways for fast ion transport, thus endowing the MXCT membrane with ultralow resistance. Consequently, the MXCT membrane reaches an ultrahigh power output of ∼8.29 W/m2 by mixing seawater and river water, which is ∼275 % higher than that of the pristine MXene membrane. Additionally, it outperforms all the reported single-layer 2D nanosheet-based osmotic power generators under the same experimental conditions in terms of output power and internal resistance (9 kΩ). This work presents a reliable strategy for stabilizing 2D Cu-TCPP MOF in electrolytes, opening new avenues for designing promising 2D nanofluidic membranes for efficient blue energy harvesting and ionic devices.

Holey Sheets Enhance the Packing and Osmotic Energy Harvesting of Graphene Oxide Membranes.

Layered membranes assembled from two-dimensional (2D) building blocks such as graphene oxide (GO) are of significant interest in desalination and osmotic power generation because of their ability to selectively transport ions through interconnected 2D nanochannels between stacked layers. However, architectural defects in the final assembled membranes (e.g., wrinkles, voids, and folded layers), which are hard to avoid due to mechanical compliant issues of the sheets during the membrane assembly, disrupt the ionic channel pathways and degrade the stacking geometry of the sheets. This leads to degraded ionic transport performance and the overall structural integrity. In this study, we demonstrate that introducing in-plane nanopores on GO sheets is an effective way to suppress the formation of such architectural imperfections, leading to a more homogeneous membrane. Stacking of porous GO sheets becomes significantly more compact, as the presence of nanopores makes the sheets mechanically softer and more compliant. The resulting membranes exhibit ideal lamellar microstructures with well-aligned and uniform nanochannel pathways. The well-defined nanochannels afford excellent ionic conductivity with an effective transport pathway, resulting in fast, selective ion transport. When applied as a nanofluidic membrane in an osmotic power generation system, the holey GO membrane exhibits higher osmotic power density (13.15 W m-2) and conversion efficiency (46.6%) than the pristine GO membrane under a KCl concentration gradient of 1000-fold.

Surface Modification of Polyethylene Terephthalate Track-Etched Membranes by 2,2,3,3,4,4,5,5,6,6,7,7-Dodecafluoroheptyl Acrylate for Application in Water Desalination by Direct Contact Membrane Distillation.

In this work, the surfaces of poly (ethylene terephthalate) track-etched membranes (PET TeMs) with pore sizes of 670-1310 nm were hydrophobized with 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate (DFHA) by photoinitiated graft polymerization. Attenuated total reflection FTIR spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDX), and contact angle measurements were used to identify and characterize the TeMs. The optimal parameters for graft polymerization were determined as follows: polymerization time of 60 min, monomer concentration of 30%, and distance from the UV source of 7 cm. The water contact angle of the modified membranes reached 97°, which is 51° for pristine membranes. The modified membranes were tested for water desalination using direct contact membrane distillation (DCMD) method. The effects of membrane pore size, the degree of grafting, and salt concentration on the performance of membrane distillation process were investigated. According to the results obtained, it has been concluded that large pore size hydrophobic TeMs modified by using DFHA could be used for desalinating water.

Impact of membrane characteristics and chemical ageing on algal protein fouling behaviour of ultrafiltration membranes

Membrane characteristics can exacerbate the prevailing challenges associated with membrane fouling in industry. However, the combined impact of deliberate membrane modifications and the unavoidable effects of chemical ageing on fouling behaviour is still not well understood. In this study, three polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes with different pore size and surface roughness were selected and subject to chemical ageing with 5000 ppm sodium hypochlorite (NaOCl) at pH 10.5, selected to simulate accelerated ageing conditions. The impact of NaOCl on membrane characteristics was assessed for exposure times from 1.2 x 105 to 25.2 x 105 ppm·h using scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, contact angle, and clean water resistance analysis. The fouling behaviour of each pristine and aged membrane was compared using 10 mg C·L−1 dissolved organic carbon algal protein feed containing 18 % biopolymeric compounds. The membrane with intermediate pore size presented lower overall filtration resistance compared to the membrane with smaller pores that developed rapid foulant cake layers. It also displayed less susceptibility to fouling via pore blocking mechanisms compared to membranes with larger pores where greater surface area available in pore walls leads to higher foulant adhesion.

High performance lamellar structured graphene oxide nanocomposite membranes via Fe3O4-coordinated phytic acid control of interlayer spacing for organic solvent nanofiltration (OSN)

Graphene oxide (GO), a 2D nanomaterial known for its precise molecular sieving, holds potential for Organic Solvent Nanofiltration (OSN) and wastewater treatment. However, challenges such as thin interlayer spacing, extended diffusion pathways, and susceptibility to dehydration and negative charge-induced swelling limit its separation performance. To overcome these limitations, Herein, we have fabricated novel Fe3O4 coordinated PhA intercalated GO nanocomposite membranes. Impressively, these nanocomposite membranes exhibited remarkable separation efficiency for dyes, pesticides, and pharmaceutical ingredients, addressing the drawbacks associated with pristine GO membranes and enhancing their overall performance. The optimum G10(1)/P1.5-F100µL nanocomposite membrane displayed impressive solvent permeance of 40.43, 33.45, 20.70, 16.24, and 5.6 L/m2 h bar for acetone, methanol, water, ethanol, and IPA, respectively, while maintaining a rejection rate of ≥98.97 % for the MO dye (MW = 327.33 g/mol). Furthermore, the membrane exhibited outstanding efficiency in separating tetracycline (TC) in ethanol (≥97.97 %) and Pendimethalin (PM) in water (≥99.88 %). Additionally, it demonstrated high rejection capabilities for MB (≥98 %) and CR (≥98.78 %) in harsh DMF solvent. Importantly, the nanocomposite membrane displayed outstanding durability throughout continuous separation of Pendimethalin (PM) in a water solution over a period of 168 h. The PM separation remained nearly unchanged for the entire 168-h duration, demonstrating high mechanical strength and chemical stability. Additionally, the single nanocomposite membrane showcased high efficiency in feed change separation, successfully separating CR in ethanol and PM in water. These results, compared to the other GO-based nanocomposite membranes, demonstrate the exceptional stability and immense potential for real OSN applications.