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Abstract: A new two-dimensional zeolitic imidazolate framework with leaf-shaped morphology (ZIF-L) was incorporated into polyethersulfone (PES) ultrafiltration membranes to investigate how the ZIF nanoflakes affect functional membrane properties. The membranes were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), and contact angle goniometry. The water permeability and molecular weight cut-offs (MWCO) of membranes were also determined under constant pressure filtration. Membrane fouling resistance was characterized under constant flux operation using bovine serum albumin (BSA) as foulant. The modified UF membrane with 0.5% ZIF-L loading showed around 75% increase in water flux without greatly affecting the MWCO. Also, the same membrane showed almost twice the fouling resistance improvement against BSA with more than 80% water flux recovery. The improvement was due to the combined effect of the lower zeta potential of the modified membrane, increased hydrophilicity and reduced surface roughness, which made the attachment of BSA protein on the membrane surface more difficult. These results demonstrate that the addition of 2-dimensional ZIF-L nanoflakes is effective for improving polymer membrane fouling resistance and water flux. [Copyright &y& Elsevier]

Abstract: Superhydrophobic membrane for the application in membrane distillation was generated by creating a hierarchical structure with multilevel roughness via depositing TiO2 nanoparticles on microporous PVDF membranes by means of a low temperature hydrothermal (LTH) process. The TiO2 coated membranes were then fluorosilanized using a low surface energy material H, 1H, 2H, 2H-perfluorododecyltrichlorosilane. A variety of techniques such as capillary flow porometry, TEM, SEM, XPS, KI test, liquid entry pressure (LEP) measurement and contact angle goniometry were applied to explore the effects of surface modification on the surface chemistry, structure and performance of the membranes. The anti-fouling performance of virgin and modified membranes were examined in a direct contact membrane distillation (DCMD) process using sodium chloride and humic acid solution as a model feed. Results showed that the modification was mechanically and thermally robust and photoactive. The liquid entry pressure (LEP) and water contact angle were increased from 120kPa and 125° to 190kPa and 166°, respectively. The fluorosilanization of TiO2 nanocomposite PVDF membranes did not compromise the mean pore size. It was also appeared that the TiO2 coating not only contributes in engineering the hierarchical structure but also provides sites (OH functional groups) for the hydrolyzed silane coupling agent to be anchored forming a robust uniform water repellent film. The filtration results also showed that the pure water flux of the modified membrane was lower than that of the virgin membrane particularly at higher temperatures. However, the sodium chloride DCMD test showed that the permeate conductivity of the virgin membrane was increased sharply whereas it was not changed for the modified membrane over the period of the experiment. A 20h fouling DCMD experiment with humic acid did not show a reduction in flux for virgin and modified membranes. However, a substantial reduction in flux was observed with the addition of 3.775mM CaCl2 into the solution due to the formation of complexes with humic acid and consequent particles coagulation and precipitation on the membrane surface. Although both virgin and modified membranes showed similar fouling behaviors, a significantly higher flux recovery was found for modified membrane compared to the virgin membrane. [Copyright &y& Elsevier]

Abstract: Addition of nanoparticles to polymer solution in membrane fabrication process has the potential to improve membrane separation performance. Recently, the mechanical and chemical modifications of TiO2 nanoparticles have shown to provide improvements in reducing the nanoparticles agglomeration and fouling in flat sheet membranes. In this study, hollow fiber PES membranes with 2wt.% mechanically and chemically modified TiO2 were fabricated. The effect of chemical and mechanical modifications on the titania nanoparticles was compared with the effect of mechanical modification only and membranes without nanoparticles additives. The results showed that the migration of nanoparticles toward outer layer only occurred after mechanical modifications, whereas the migration and size of agglomerations reduced significantly after both the chemical and mechanical modifications of particles. Higher thermal resistance, stiffness and lower elasticity were observed in fibers made with chemically and mechanically modified particles. Enhancement in initial pure water flux due to lower intrinsic membrane resistance and bigger pore size was also observed. While the rejection of BSA remained similar and lower overall ultrafiltration resistance was observed, the benefits of particles modifications on flux recovery after cleaning of hollow fiber membranes was not observed, possibly due to a significant change in pore structure and initial permeabilities. [Copyright &y& Elsevier]

Abstract: Thin mesoporous coatings of TiO2 nanoparticles were developed for in-house and commercial PES membranes of varying pore sizes using a low temperature hydrothermal (LTH) approach. Titania sol–gel particles were dip-coated onto membrane substrates, followed by heat and UV treatments to extract the residual organic templates. Dip-coating parameters such as drying and holding time, dipping and withdrawal velocities, and the number of coating cycles were varied to optimise the microstructure and surface properties of the coating. Coated membranes exhibit a dual level hierarchical roughness and hydrophilicity which was maintained without continuous UV illumination. The organic templating agent (Pluronics F127) enhanced adhesion of the particles; however the heat treatment collapsed some pores in the tighter ultrafiltration membranes. Results showed that the coatings were mechanically robust and photoactive. Passive protein adsorption was reduced significantly on the TiO2 coated surfaces. Filtration performance of coated and uncoated 500kDa membranes was also investigated with humic acid as a model foulant, and an increase in flux recovery was observed during multiple fouling and cleaning cycles with the titania coated membrane. The LTH approach provides a platform for further surface functionalization of polymeric membranes to generate photoactive coatings, tuneable hydrophilicity, low fouling surfaces and novel surface architecture. [Copyright &y& Elsevier]

Abstract: Recently, TiO2 nanoparticles blended within polymeric membranes have shown to provide improvements in fouling performance. However, agglomeration of nanoparticles remains as one of the major obstacles for generating a uniform surface, and also the mechanisms for improved fouling performance has yet to be elucidated. In this study, mechanical and chemical modification approaches were adapted using Degussa P25 TiO2 nanoparticles to improve their dispersion. Afterward, modified TiO2 nanoparticles were incorporated into polyethersulfone based in-house membranes and their effect on microstructure, surface chemistry, and fouling performance were investigated. Different techniques such as SEM, EDX, TGA, DSC, AFM, FTIR, contact angle goniometry, molecular weight cut-off, static protein absorption and surface free energy measurement were applied to characterize and explore the effect of different factors on fouling performance. The results showed that good dispersion of nanoparticles in the membrane was achieved after both chemical and mechanical modifications of particles, as a result of less agglomeration. The combination of chemical and mechanical modifications was found to have significant effects on surface free energy, roughness, surface pore size and protein absorption resistance as well as hydrophilicity. While previous researchers believe that the increase in hydrophilicity is the most likely reason for improvement in fouling performance, these other parameters such as changes in membrane morphology and local surface modifications may contribute just as much to greater fouling resistance when the effects of unmodified and modified titania were compared. [Copyright &y& Elsevier]

Satisfactory ultra-high biofilm formation resistant polymeric interfaces have yet to be realized. A new application of mesoporous carbon (MPC) via the loading of silver nanoparticles into its matrix was successfully introduced for the fabrication of biofouling resistant polyethersulfone ultrafiltration membranes. MPC not only solved the silver nanoparticle detachment issue, as the most significant scaling up challenge of new materials modified by silver, but it also led to an anti-adhesion interfacial layer for microorganisms. The effect of the incorporation of MPC on biofouling mitigation and the performance of the composite membranes was examined through bacterial adhesion resistance. The composite membrane containing the optimized 0.20 wt% MPC doped with an Ag ratio of 1:99 (w/w) easily dispatched microorganisms. Bacterial attachment on the membrane surface was reduced dramatically. Furthermore, the remaining attached bacterial cells were dealt with via the bactericidal properties of the silver nanoparticles, up to 93%. Rendering of the flow cytometry results showed that MPC amplified the effect of the negligible amount of Ag (0.002 wt% of the membrane) and induced apparent bacterial damage of Bacillus subtilis (92.94%) and Escherichia coli (93.21%). The polymeric mixed matrix membrane entirely mitigated biofouling over 99% by the combination of the bactericidal effect of silver and the anti-adhesion properties of MPC. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) membranes have potential for the efficient water and wastewater treatment applications. However, their development has faced significant challenges due to their fouling propensity. In this study, FO membranes modified with sulfobetaine zwitterions (i.e., [2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide) were fabricated and used for the first time to address microplastic (MP) fouling issue. Water flux, reverse salt flux (RSF), fouling, and flux recovery were evaluated for the membranes loaded with different quantities of the zwitterions ranging from 0.25 % to 2 %. The developed membranes were tested over 49 h with feed solutions containing polyethylene MPs and bovine serum albumin (BSA) to evaluate their fouling resistance. The synergistic effects of the two foulants indicated that the MPs were the primary cause of fouling. The presence of BSA effectively reduced the blocking effect of MPs and therefore lowers overall fouling. Additionally, improved water flux, structural parameter (S), and RSF were reported for the modified membranes. The zwitterion's unique structure with hydrophilic groups (C O and O S O) resulted in high flux recovery rates of over 90 % for all modified membranes within only 30 min of physical cleaning upon fouling tests. The results demonstrate the high potential of the modification method for targeting the removal of MPs in TFC-based membranes. [Display omitted] • Novel zwitterion-based forward osmosis membranes were fabricated. • The modified membranes enhanced water flux. • 99 % flux recovery rate was obtained from modified membranes. • The membranes showed excellent fouling resistance against microplastics. • The reverse salt flux significantly reduced from 4.07 to 1.35 g·m−2·h−1. [ABSTRACT FROM AUTHOR]

The recent advancements in fabricating forward osmosis (FO) membranes have shown promising results in desalination and water treatment. Different methods have been applied to improve FO performance, such as using mixed or new draw solutions, enhancing the recovery of draw solutions, membrane modification, and developing FO-hybrid systems. However, reliable methods to address the current issues, including reverse salt flux, fouling, and antibacterial activities, are still in progress. In recent decades, surface modification has been applied to different membrane processes, including FO membranes. Introducing nanochannels, bioparticles, new monomers, and hydrophilic-based materials to the surface layer of FO membranes has significantly impacted their performance and efficiency and resulted in better control over fouling and concentration polarization (CP) in these membranes. This review critically investigates the recent developments in FO membrane processes and fabrication techniques for FO surface-layer modification. In addition, this study focuses on the latest materials and structures used for the surface modification of FO membranes. Finally, the current challenges, gaps, and suggestions for future studies in this field have been discussed in detail. [Display omitted] • The existing challenges in traditional forward osmosis (FO) membranes are discussed. • Surface modification of FO membranes (e.g., surface grafting and coating) are evaluated. • Remarkable flux improvements (ranging from 17% to 80%) have been reported for surface modified FO membranes. • Novel additives and biomimetic membranes are evaluated for FO membranes' surface tailoring. • The influence of nanochannels on the performance of FO membranes is investigated. [ABSTRACT FROM AUTHOR]

With the gradual increase of microplastics (MPs) in water and wastewater streams, it is imperative to investigate their removal using tertiary treatment systems to minimize and preferably prevent their entrance into aquatic environments. Forward osmosis (FO) is a non-pressurized membrane process with potential applications in MPs removal from wastewater. However, efficient application of FO systems relies on developing high-performance FO membranes with low fouling tendency. MPs are proven as emerging foulants in membrane systems, diminishing their performance and lifetime and this highlights the need to consider MP fouling in developing sustainable membranes. The current study focuses on a novel modification of thin film composite (TFC) FO membranes by MIL-53(Fe) as a water-stable and hydrophilic metal-organic framework. Experimental results demonstrated that the optimized FO membrane (0.2 wt% MIL-53(Fe)) achieved a significantly higher water flux (90% increase) with a 23% less reverse salt flux. The modified membrane also had significantly less flux decline in fouling experiments and higher flux recovery after physical cleaning compared to the control membrane affirming its higher antifouling efficiency. MIL-53(Fe) integration in the FO substrate proved to be a practical method for developing high-performance TFC FO membranes with improved antifouling properties against MPs and organic foulants. [Display omitted] • MIL-53(Fe) incorporation into TFC FO substrate enhanced the membranes' performance. • MIL-53(Fe) improved the hydrophilicity and porosity of the FO substrate. • TFC on the developed substrate had higher water flux and lower specific salt flux. • The modified membrane showed better microplastic antifouling properties. • MIL-53 modification improved the membranes' organic fouling resistance. [ABSTRACT FROM AUTHOR]

Despite the huge contribution of membrane-based brine and wastewater purification systems in today's life, biofouling still affects sustainability of membrane engineering. Aimed at reducing membrane modules wastage, the need to study biofouling monitoring as one of contributory factors stemmed from the short time between initial attachment and irreversible biofoulant adhesion. Hence, a membrane for monitoring is introduced to determine the right cleaning time by using fluorescent sensing as a non-destructive and scalable approach. The classical solid-state emissive fluorophore, tetraphenylethylene (TPE), was introduced as a sustainable, safe and sensitive fluorescent indicator in order to show the potential of the method, and polyethersulfone (PES) and nonsolvent-induced phase separation method, the most popular material and method, are used to fabricate membrane in industry and academia. Since the employed filler has an aggregation-induced emission (AIE) characteristic, it can track the biofouling throughout the operation. The fabricated membranes have certain characterizations (i.e. morphology assessment, flux, antibiogram, flow cytometry, surface free energy, and protein adsorption) which indicate that hybrid membrane with 5 wt % of TPE has identical biofouling activity compared to neat PES membrane and its optimal luminescence properties make it an appropriate candidate for non-destructive and online biofouling monitoring. Image 1 • A multifunctional mixed matrix membrane for better understanding of biofouling is presented. • Employed filler has an aggregation-induced emission characteristic which can track the biofouling throughout the operation. • The obtained membranes revealed promising biofouling sensitivity. • The hybrid PES UF membrane with 5 wt % of TPE caused apparent biofouling detection. [ABSTRACT FROM AUTHOR]