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This study explored the impact of eco-friendly polydopamine (PDA) coated ZnFe2O4 nanocomposites (PDA@ZnFe2O4 NCs) as nanofillers to fabricate a new class of polyethersulfone (PES) hybrid ultrafiltration (UF) membranes for wastewater treatment applications. The hybrid UF membrane was prepared by incorporating PDA@ZnFe2O4 NCs into PES via the non-solvent induced phase separation (NIPS) process. The PDA@ZnFe2O4 NC was characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Additionally, the morphology and performance of the prepared hybrid membranes were characterized by SEM, contact angle, surface charge, and thermogravimetric analysis (TGA). The incorporation of PDA@ZnFe2O4 NC into the PES membrane affects the porosity, mean pore radius, hydrophilicity, and thermal stability of the developed hybrid membranes. The pure water flux of the PES hybrid membrane with 4 wt% PDA@ZnFe2O4 reached ∼687 L/m2 h, which is about 188% higher than that of the pristine PES membrane. The performance of the PES/ PDA@ZnFe2O4ultrafiltration hybrid membrane was also investigated using humic acid (HA) foulant and oil/water emulsion individually. Compared to the pristine PES and PES/ZnFe2O4 membranes, the developed hybrid membranes showed enhanced permeability and HA foulant removal. HA's removal efficiency has improved from ∼65% in the pristine PES membrane to ∼94% in the 4 wt% PDA@ZnFe2O4 hybrid membrane. The abundant functional groups on the PDA@ZnFe2O4 NC surface also enhanced the separation of the oil/water emulsion (96%). In both the HA and oil/water emulsion separation tests, the flux recovery ratio (FRR) and reversible fouling ratio (Rr) were also significantly improved, suggesting that the PES/PDA@ZnFe2O4 membrane was a very promising candidate for HA removal and treatment of oily wastewater.

Introduction Self-forming dynamic membrane (SFDM) technology has been gaining significant interest due to its potential advantages, notably lower capital and operational cost and easier fouling con...

The concept of nanomaterials membranes (NMs) promises to be a sustainable route to improve the membrane characteristics and enhance the performance of membrane bioreactors (MBRs) treating wastewater. This paper provided a critical review of recent studies on the use of membranes incorporating nanomaterials in membrane bioreactor (NMs-MBR) applications for wastewater treatment. Novel types of nanomaterials membranes were identified and discussed based on their structural morphologies. For each type, their design and fabrication, advances and potentialities were presented. The performance of NMs-MBR system has been summarized in terms of removal efficiencies of common pollutants and membrane fouling. The review also highlighted the sustainability and cost viability aspects of NMs-MBR technology that can enhance their widespread use in wastewater treatment applications.

This research aimed at synthesizing polyethersulfone/α-zirconium phosphate (PES/ α-ZrP) flat-sheet nanocomposite ultrafiltration (UF) membranes. The impact of α-ZrP nanoparticle (NP) addition on the morphology, functionalities, hydrophilicity, and surface charge of the membrane, among others, were investigated. Different concentrations of α-ZrP NPs (0.25, 0.50, 0.75, and 1.00 wt.%) were tested. Membranes surface morphology was investigated by Fourier-transform infrared (FT-IR), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Microscopic analyses affirmed that the α-ZrP NPs were successfully incorporated into the PES membranes. Also, the composite membranes were hydrophilic reporting increased mechanical strength, porosity, and thermal stability than the pristine PES membrane. An overall removal efficiency of 70.2 ± 1.0, 99.7 ± 0.2, 81.7 ± 1.1, 74.4 ± 1.5, and 91.5 ± 2.0% for Cd2+, Cu2+, Ni2+, Pb2+, and Zn2+ was reported, respectively when 0.25 wt.% of α-ZrP NPs was added. The enhanced capabilities of the composite membranes in the heavy metal removal was ascribed to the increased electrostatic attraction forces with the metal ions in the solution and the surface of the PES/α-ZrP composite membrane. Lastly, the developed membranes demonstrated less fouling with self-cleaning properties which can be very beneficial in the field of industrial wastewater treatment.

BACKGROUND: Reverse osmosis (RO) is becoming the predominant technology for the future of desalinated of seawater Nonetheless, operational challenges such as membrane biofouling in RO desalination plants result in membrane deterioration and high energy costs In this regard, pre-treatment technologies, such as microfiltration (MF) membranes, are proven to reduce the impact of membrane biofouling in RO systems Hence, surface modifications of commercial cellulose MF membranes with graphene oxide nanosheets (GONSs) at different concentrations were carried out in this research study The new membranes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy amongst other methods of analysis A continuous cross-flow MF system was used to investigate the performance of the new cellulose/GONS membranes with regards to total bacteria count (TBC) removal, water flux, and biofouling resistance RESULTS: TBC removal efficiency of 93 6 ± 2 4% and 27 4 ± 12 5% was achieved using the new cellulose/GONS membranes and control pristine cellulose membranes, respectively This higher removal efficiency was achieved at a water flux of 334 7 ± 10 4 L/(m2 h) Furthermore, a dramatic 55% increase in the transmembrane pressure (TMP) of the pristine cellulose membrane was observed after 24 h operation compared to only a 6% increase in the newly fabricated cellulose/GONS membranes, reflecting their strong anti-fouling properties CONCLUSION: Surface modification of MF membranes with anti-fouling nanomaterials such as GONS has the potential to be implemented in the pretreatment of seawater to improve the RO performance and lower the energy consumption © 2020 Society of Chemical Industry

In this study, commercial cellulose membranes were surface coated with alpha‑zirconium phosphate nanoparticles (α-ZrP-n) to study their impact on the overall removal efficiency of heavy metals from synthetic metal mixture wastewater solution. A total of four homogeneous solutions (0.25, 0.50, 0.75, and 1.00 wt%) of α-ZrP-n were prepared by sonicating the nanoparticles in deionized water. These solutions were used to surface coat the commercial cellulose membranes. The Scanning Electron Microscopy (SEM) along with Energy Dispersive Spectroscopy (EDS) were used to confirm the attachment of α-ZrP-n on the cellulose membrane surface. Furthermore, the structural characteristics of the α-ZrP-n modified cellulose membranes were also studied. The water contact angle results showed that all coated membranes remained super-hydrophilic. The porosity of the membranes decreased to 48% with the addition of 1.00 wt% α-ZrP-n compared to 65% for the pristine membrane. The mechanical strength has improved from 3.4 MPa for the pristine membrane to about 4 MPa for the 1.00 wt% α-ZrP-n membrane. Similarly, the thermal stability was found to be slightly enhanced as evidenced by the increase in decomposition temperature to 280 and 285 °C in the 0.75 and 1.00 wt% α-ZrP-n membranes, respectively. Furthermore, a removal efficiency of 97.0 ± 0.6, 98.0 ± 0.5, 99.5 ± 0.2, and 91.5 ± 2.0% for Cu (II), Zn (II), Ni (II), and Pb (II), respectively, was observed with the 0.50 wt% α-ZrP-n membrane. This removal was achieved at a flux of 41.85 ± 0.87 × 103 LMH. Increasing the α-ZrP-n concentration further did not show any improvement in the overall removal efficiency. However, it led to 46% flux reduction in the 1.00 wt% α-ZrP-n membrane. The mechanism of removal of the heavy metal ions was postulated to be a combination of ion exchange and electrostatic attraction of the strong negatively charged α-ZrP-n membranes and the free metal ions in the wastewater solution.

A two-stage treatment for efficient removal of organic matter, heavy metal ions, and other contaminants from raw wastewater is presented in this manuscript. The two stages include electrically-enhanced membrane bioreactor (eMBR) and filtration using titanium dioxide (TiO2) aerogel membrane. The aerogel membrane was highly porous (with 90% porosity), superhydrophilic, highly permeable (with water permeability of 850 LMH/bar), and contained networks of interconnected nanowires with nano-sized pores. The combined system removed 100% bacteria, 97.8% COD, 96.9% Zn2+, 99.3% Cr6+, and 84.1% Cd2+ from raw municipal wastewater sampled from Masdar City Wastewater Treatment Plant, Abu Dhabi, United Arab Emirates. Residual contaminants were removed from eMBR effluent by the aerogel membrane through surface charge interactions, nano-sized pores, and photodegradation. The aerogel membrane was characterized before and after filtration through Scanning Electron Microscopy, X-ray Diffraction, Fourier-Transforms Infrared Spectroscopy, Raman Spectroscopy, and Energy Dispersive X-ray spectroscopy. After filtration and chemical cleaning of the aerogel membrane, ˜90% flux recovery was shown. The cost of water production was US$1.03/m3, which was less than the cost of water production using seawater desalination and industrial wastewater treatment. The final effluent is suitable for advanced applications such as agricultural irrigation and industrial process heating/cooling, based on the pollutants measured.

Deformable oil drops of two interfacial tensions (namely, 4 and 30 mN m−1) were filtered through a slotted-pore membrane (with pore dimensions of 4 × 400 μm) at four vibrational shear rates (namely, 0, 1200, 3200 and 8000 s−1) and two permeate fluxes (namely, 200 and 1000 l m−2 h−1). The membrane material was made of nickel. The membrane surface was modified with Poly tetra fluoroethylene (PTFE)F for better performance in-terms of higher flux rate rejection. The oil with the lower interfacial tension was more deformable, because the increase in TMP was less due to the passage of even larger drops to the slot opening, also the permeate quality was lower as a result of the higher concentration of the oil in the permeate. The impact of interfacial tension was more significant under the following conditions; first at lower shear rates, the particle back-transport effects become more dominant than the deformability effects at higher shear rates, and secondly at the higher permeate flux, the higher permeate drag enhances the deformability effects. Discrepancies were observed between experimental results and model predictions based on circular membrane pores and non-deformable foulants. In the future, it is expected that a better agreement of the experimental results and the analytical model could be obtained if the model is modified for the slotted pore membrane.

In recent years, bimetallic oxide nanoparticles have garnered significant attention owing to their salient advantages over monometallic nanoparticles. In this study, Fe2O3–Mn2O3 nanoparticles were synthesized and used as nanomodifiers for polyethersulfone (PES) ultrafiltration membranes. A NIPS was used to fabricate asymmetric membranes. The effect of nanoparticle concentration (0–1 wt.%) on the morphology, roughness, wettability, porosity, permeability, and protein filtration performance of the membranes was investigated. The membrane containing 0.25 wt% nanoparticles exhibited the lowest water contact angle (67°) and surface roughness (10.4 ± 2.8 nm) compared to the other membranes. Moreover, this membrane exhibited the highest porosity (74%) and the highest pure water flux (398 L/m2 h), which was 16% and 1.9 times higher than that of the pristine PES membrane. The modified PES membranes showed an improved antifouling ability, especially against irreversible fouling. Bovine serum albumin protein-based dynamic five-cycle filtration tests showed a maximum flux recovery ratio of 77% (cycle-1), 67% (cycle-2), and 65.8% (cycle-5) for the PES membrane containing 0.25 wt% nanoparticles. Overall, the biphasic Fe2O3–Mn2O3 nanoparticles were found to be an effective nanomodifier for improving the permeability and antifouling ability of PES membranes in protein separation and water treatment applications.

Hydroxyapatite-decorated activated carbon (HAp/AC) nanocomposite was synthesized and utilized as a nanofiller to fabricate a novel type of polyethersulfone (PES) nanocomposite ultrafiltration (UF) membranes. Activated carbon (AC) derived from orange peel was synthesized by low-temperature pyrolysis at 400 °C. A hydroxyapatite/AC (HAp/AC) nanocomposite was developed by a simple one-pot hydrothermal synthesis method. The UF membrane was fabricated by intercalating HAp/AC fillers into PES casting solution by the non-solvent induced phase separation (NIPS) process. The prepared membranes exhibited a lower water contact angle than the pristine PES membrane. The hybrid membrane with 4 wt% HAp/AC nanocomposite displayed 4.6 times higher pure water flux (~660 L/m2 h) than that of the pristine membrane (143 L/m2 h). In static adsorption experiments, it was found that the amount of humic acid (HA) and bovine serum albumin (BSA) adsorbed by the HAp/AC-PES hybrid membrane was much lower than that of the original membrane due to the electrostatic repulsive forces between them and the surface of the membrane. Irreversible fouling was reduced from 33 to 6 % for HA and from 46 to 8 % for BSA after HAp/AC was incorporated into the PES matrix. After 7 cycles of water-BSA-water, the HAp/AC-PES hybrid membrane maintained a high pure water flux of 540 L/m2 h with an excellent flux recovery ratio (FRR), demonstrating the long-term stability of the membranes. The developed UF membranes outperformed the original PES membranes in terms of permeability, selectivity, and antifouling.

Produced water, a by-product generated from the oil and gas extraction processes, represents a major challenge in the oil and gas industry as it is generally characterized with a very high salinity and oil content. Currently used ceramic membranes for oil-water separation suffer from the low water flux in spite of their several distinctive advantages. To overcome this limitation and to increase the water flux and oil rejection, commercial ceramic TiO2 membranes were dip coated with silica (SiO2) nanoparticles at different concentrations of 0.25, 0.50, 0.75, and 1.0 wt %. Coated membranes were characterized using scanning electron microscopy (SEM), energy-dispersive x-ray sSpectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR) and Raman Spectroscopy and contact angle. Results showed that SiO2 nanoparticles were successfully deposited on the surface of the ceramic membranes confirming the dip coating approach. Furthermore, water flux of 817, 2724, 3636, 627, and 1292 L m−2 h−1 (LMH) was reported at control, 0.25, 0.50, 0.75 and 1.0 wt%; respectively. Also, contact angle reported 75°, 50°, 40°, 24°, 0° at control, 0.25, 0.50, 0.75 and 1.0 wt%; respectively. Finally, total organic carbon (TOC) in the treated water samples reported 100, 28, 11, 9, 10, 13 mg L−1 at control, 0.25, 0.50, 0.75 and 1.0 wt%, respectively. This study can be a preliminary to further studies that accommodate industry-like conditions to help decrease the gap between ideal laboratory setups and harsh real life conditions to fully optimize and exploit the advantages of ceramic membranes in oil-water separation.

The removal of heavy metal ions from industrial wastewater is essential as they pose serious threats to human health and the environment. In this study, novel poly(vinylidene fluoride) (PVDF)-alpha-zirconium phosphate (PVDF-α-ZrP) mixed matrix membranes (MMM) were prepared via the phase inversion method. Membranes with different α-ZrP nanoparticles (NPs) loadings (0.25, 0.50, 0.75, or 1.00 wt%) were fabricated. The impacts of α-ZrP NP loading on the membrane’s morphology, functionality, surface charge, and hydrophilicity were evaluated. Fourier-transform infrared and the energy-dispersive X-ray spectroscopy were performed to verify the presence of α-ZrP NPs in the fabricated membranes. The PVDF membranes became more hydrophilic after incorporating the α-ZrP NPs. The thermal and mechanical stability and porosity of the PVDF-α-ZrP MMM were higher than those of the pristine PVDF membrane. The increased hydrophilicity, pore size and porosity and reduced surface roughness of the PVDF-α-ZrP membrane led to significant flux increase and reduced fouling propensity. The PVDF-α-ZrP membrane containing 1.00 wt% α-ZrP was capable of removing 42.8% (Cd2+), 93.1% (Cu2+), 44.4% (Ni2+), 91.2% (Pb2+), and 44.2% (Zn2+) from an aqueous solution at neutral pH during filtration.

© 2020 Elsevier B.V. Polybenzimidazole (PBI) is a chemically and thermally stable polymer, which is being considered for forward osmosis (FO) seawater desalination in regions with high seawater temperatures and salinities. In this work, FO flat sheet membranes were fabricated using non-solvent induced phase separation (NIPS) method from PBI dope solution incorporated with silica nanoparticles (SNPs) at different concentrations (0, 0.5, 1 and 2 wt%). The influence of draw solution concentration, cross-flow velocity and membrane cell orientation on the performance of pristine PBI and PBI/SNP membranes was examined. Results showed that the performance of the PBI/SNP membranes improved compared to the pristine PBI membrane. Addition of 0.5 wt% of SNPs to PBI membranes (S0.5) reduced the membrane's structural parameter (809.4 μm vs. 1193.2 μm), augmented the tensile strength (31.9 MPa vs. 27.3 MPa), and increased water flux by two folds (16.9 Lm−2 h−1 vs. 7.4 Lm−2 h−1) compared to the pristine PBI membrane (S0). Given the thermal stability of the PBI/SNP membrane along with its improved water permeation performance, the modified membrane offers a promising option for the FO process in hot and arid zones.

Nanomodification of ultrafiltration (UF) membranes has been shown to be a simple and efficient technique for the preparation of high-performance membranes. In this work, an iron oxide functionalized halloysite nanoclay (Fe-HNC) nanocomposite was prepared and used as a nanofiller for polyethersulfone (PES) membranes. The effect of Fe-HNC concentration on the filtration performance of the membrane was investigated by varying the nanocomposite dosage (0–0.5 wt. %) in the casting dope. Various characterization studies showed that the incorporation of Fe-HNC nanocomposites improved the membrane morphology and enhanced the surface properties, thermal stability, mechanical strength, hydrophilicity, and porosity. The permeability to pure water and filtration of humic acid (HA) were significantly improved by incorporating Fe-HNC into the PES membranes. The membrane with Fe-HNC loading of 0.1 wt. % exhibited the highest pure water permeability (174.3 L/m2 h bar) and removal of HA (90.1 %), which were 1.8 times and 29 % higher, respectively than the pristine PES membrane. Moreover, fouling studies showed the enhanced antifouling ability of the Fe-HNC nanocomposites modified PES membranes, especially against irreversible fouling. Continuous membrane regeneration-based fouling removal studies from HA showed that the PES/0.1 wt. % Fe-HNC membrane exhibited a high fouling recovery of 70.4 % with very low reversible and irreversible fouling resistance of 9.61 % and 14.78 %, respectively, compared to the pristine PES membrane (fouling recovery: 40.4 %; reversible fouling: 21.7 %; irreversible fouling: 20.1 %). Overall, the Fe-HNC nanocomposite proved to be an effective nanomodifier for improving the permeability of PES membranes and the antifouling ability to treat HA polluted aqueous streams.

Nanocomposite membranes consisting of functionalized β-cyclodextrin (fβ-CD) and polyethersulfone (PES) were fabricated, characterized, and used for low-pressure wastewater post-treatment. The impact of nucleophilic functionalization of β-CD on the performance of these membranes was evaluated via three substitution routes: Crosslinking with nucleophilic dicarboxyl groups (M1) in maleic acid; co-polymerization with excess amino group (M2) in hyperbranched polyethyleneimine (HPEI); and nucleophilic modification with amino and hydroxyl groups (M3) in chitosan. All fβ-CD-incorporated membranes were hydrophilic as a result of the highly populated –OH groups at the exterior of β-CD. Although there are higher-energy intermolecular C–O bonds in M1 membrane, less degree of nucleophilic crosslinking restricted kinetic hindrance and led to an increase in the mean pore size of M1 membrane to 52 nm. A dense structure, the lowest mean pore size of 22 nm, and the highest porosity of 45% was imparted to M2 membrane by the flexible C–N linkages provided by HPEI. Nucleophilic attack by the abundant N–H groups in HPEI also improved the tensile strength of M2 membrane reaching 20 MPa. Consequently, the water permeability of M2 membrane was significantly enhanced via β-CD's solution-diffusion property. M1, M2, and M3 membrane water permeability were 61, 239, and 167 LMH bar−1, respectively. M3 membrane showed the highest removal efficiencies for heavy metal ions (92% of Cr6+, 90% of Zn2+, 82% of Fe2+, and 87% of Cd2+) since it is the most hydrophilic membrane with abundant –OH groups in chitosan. However, M2 membrane displayed the highest removal efficiencies for residual organics, i.e. 67% chemical oxygen demand (COD) and 84% bacteria due to the hydrophobic interior of its dense fβ-CD.

In this research study, a direct contact membrane distillation (DCMD) system was used in the concentration of raw brine from a full-scale reverse osmosis desalination plant for further zero-liquid discharge (ZLD) applications. Several operating conditions such as feed inlet temperature (Tf), feed (Qf) and permeate (Qp) flow rate, and feed concentration (Cf) were tested to obtain the optimum permeate flux across the membrane, salt rejection and specific thermal energy consumption (STEC). The highest flux of 16.7 LMH, salt rejection of 99.5% and STEC of 152 kWh/m3 were achieved at Tf, Qf, Qp, and Cf of 85 °C, 75 L/h, 48 L/h and 57,500 ppm, respectively. Furthermore, this study was carried out for a long term operation of 77 h in which the membrane was found to be prone to significant fouling thereby resulting in a flux decline across the membrane of 69%. To mitigate fouling, novel membranes were prepared through the surface coating of commercial membranes with graphene nanoplatelets (GNPs) at 0.08, 0.16 and 0.2 wt%. Over a 10 h operation, membranes coated with 0.08 and 0.16 wt% GNP reduced membrane fouling by 59 and 78%, respectively.

Membrane-based technologies are vital in water purification processes such as desalination and wastewater recycling. Polymeric membranes dominate the membrane market; however, they still suffer from issues related to their chemical, mechanical, and thermal stability, and more importantly, membrane fouling. However, these membranes are associated with various environmental problems that occur during their production and disposal. In this work, an eco-friendly and biodegradable membrane composed of polylactic acid (PLA), hydroxyapatite (HAp) as filler, and polydopamine (PDA) as surface coating was proposed. This unique combination and synergic effect of HAp and PDA were found to enhance the PLA membrane's permeation notably. The fabricated PLA/HAp/PDA membrane resulted in an increase in water permeability of the pristine PLA membrane from 359 ± 76 L/m2.h.bar to 788 ± 58 L/m2.h.bar for the membrane coated with 2 wt.% HAp/1-hour PDA (PLA-H/PDA-1). Similarly, the flux recovery ratio (FRR) increased from 20% for the pristine PLA membrane to 54% for the PLA-H/PDA-1 membrane after 3 cycles. These properties were found to be due to the enhanced membrane characteristics. For instance, the contact angle dropped by 5% (i.e., the membrane became more hydrophilic) and the porosity increased from 55 to 60%. The pore size was also increased from 97 to 133 nm as a result. The modified membranes retained up to 87% of the normal organic matter (NOM), and no deterioration in the thermal properties of the membranes was observed. These membranes open a new route to a circular economy in membrane technology by reducing environmental costs while allowing continuous operation of the membranes.

In this work, electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofiber membranes were loaded with tungsten oxide (WO3) nanoparticles, surface coated with polydopamine (PDA) hierarchical structures, and tested in oil/water separation, photothermal water evaporation, and degradation of ampicillin. The electrospun nanofiber membranes (ENMs) consisted of three layers and the WO3 nanoparticles were incorporated into the top layer to increase their surface exposure. These layers were then heat-pressed for dimensional stability and surface coated with PDA hierarchical structures. Characterization was conducted using microscopic, goniometric, gravimetric, and spectroscopic methods. All ENMs displayed randomly oriented, smooth microporous structure and EDS mapping revealed a uniform distribution of WO3 nanoparticles on the nanofiber matrix. WO3-blended ENMs showed improved mechanical strength, higher UV/Vis absorption, and similar thickness as pristine ENM. PDA deposition has reduced the water contact angle of pristine PVDF-HFP membrane from 130.3 to 0°, whereas, the underwater oil contact angle has increased from 55.8 to 159.7°. The PDA-coated ENMs exhibited enhanced oil/water separation with 384.3 L m−2h−1 (LMH) of flux and 97.6% oil rejection when filtered under gravity. Photothermal interfacial evaporation and ampicillin degradation tests also demonstrated the multifunctionality and exciting features of the fabricated membranes for a wide range of applications.

This study presents the synthesis of a novel graphene oxide-manganese oxide (GO-MnO2) nanohybrid and its incorporation into sulfonated polyethersulfone (SPES) ultrafiltration (UF) membranes for wastewater treatment applications. The nanohybrid was first prepared by grafting ethylenediamine (ED) onto the edge of GO followed by direct mixing with the MnO2 nanosheets. The composite membranes were prepared via the phase inversion method and optimized by varying the concentration of the GO-MnO2 nanohybrid (0–6 wt%). The membranes were characterized using scanning electron microscopy, surface zeta potential, water flux, porosity, among others. The results showed that the pure water flux increased from 59.5 ± 2.5 L·m−2·h−1 in the pristine SPES membrane to 129.7 ± 4.1 L·m−2·h−1 in the SPGM4 (4 wt% GO-MnO2). Furthermore, the heavy metal ions rejection improved from 70.1, 49.1, and 55.8% for Cu2+, Zn2+, and Ni2+ ions, respectively, in the pristine SPES membrane to 81.1, 64.0, and 67.4% in the SPGM4 membrane. Also, the composite membranes revealed improvement in the anti-fouling properties over the pristine SPES membrane. For example, the SPGM4 membrane recovered 90.5 ± 2.9% of its initial flux compared to only 72.6 ± 3.1% in the pristine membrane after 4 cycles of heavy metal filtration and simple acid cleaning steps. Overall, the addition of GO-MnO2 nanohybrid enhanced the properties of the pristine SPES, creating new potential for such composite membranes in the wastewater treatment industry.

Due to the continuing growth of reverse osmosis (RO) water treatment plants worldwide, the amount of discarded end-of-life (EoL) RO membrane modules is expected to increase drastically in coming years. One of the approaches to address this problem is to transform the EoL membranes for other purposes. In this study, a new approach based on sonication was studied to convert the EoL RO membrane from RO properties into microfiltration (MF) properties, offering a transformation process that was much faster (15 min) than that of typical chemical treatment process (ranging from hours to days) using oxidizing agent solution. Our results indicated that with only 15-min ultrasonication, the properties of EoL RO membrane could be significantly altered, reaching pure water permeability of 172.6 L/m2.h.bar (70-fold increment) with NaCl rejection reduced from ~80% to less than 2%. This is attributed to the deterioration of the polyamide thin selective layer atop the EoL RO membrane. As a comparison, the chemical treatment using 5000-ppm potassium permanganate (KMnO4) solution requires at least 168 h to achieve similar membrane properties. It was also found that the presence of KMnO4 during ultrasonication process could accelerate the rate of polymeric degradation, resulting in even higher pure water permeation. As a conclusion, our work demonstrated a rapid and new approach that is capable of transforming the EoL RO membrane for the filtration process of macromolecules, thus offering a practical solution to address the disposal issues of EoL RO membrane modules.

The fabrication of polyvinylidene fluoride (PVDF) membranes was studied using chitosan as a hydrophilic additive for flux enhancement and stability. Chitosan (CS) was blended with PVDF at 0.5, 1.0, 1.5, 2.0 and 2.5% (w/w) concentration, to prepare mixed matrix membrane using the phase inversion method. CS presence within the polymer matrix was confirmed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The fabricated membranes were also analyzed for their structural and surface characteristics, including pore size distribution, porosity, contact angle, wettability and surface roughness. The water contact angle of the membranes has decreased upon the addition of CS. However, the wettability of the membranes was affected more profoundly due to an increase in their pore size. Microfiltration tests showed that the addition of CS was helpful in the reduction of fouling by bovine serum albumin (BSA). However, membranes with CS content higher than 1.0% endured surface micro-ruptures during the filtration tests due to swelling resulting from high water uptake. This simple method of fabrication of PVDF/CS membranes is a potential solution for the low flux and fouling of common PVDF microfiltration membranes. Furthermore, understanding the impact of CS on the fabricated membranes can facilitate the fine tuning of the membrane properties to achieve higher efficiencies.

Oily wastewater is the largest liquid waste generated, mainly resulting from oil and gas production. It consists of hazardous materials, salts, toxic chemicals, surfactants and crude oil content. Therefore, it is considered a huge threat for the environment and marine life, and hence needs to be adequately treated before discharge into the sea. Among all technologies used for oily wastewater treatment, membrane technology has been found to be effective in handling emulsified oil droplets with a particle size of less than 40 μm. However, one of the major obstacles associated with the membrane technology is the deposition of foulants onto the membrane surface, a phenomenon referred to as membrane fouling, which severely reduces the treatment efficiency. Oily wastewater is an aggressive environment; hence membrane fouling could hugely and adversely impact the membrane performance. Recently, membrane fouling mitigation has been a main focus for researchers working in the area. In this review, various membrane fouling mitigation techniques in the treatment of oily wastewater were assessed. Membrane oscillation and pore structure, for example, play an important role in membrane fouling mitigation and have not been reviewed in the literature. The present study is mainly focused on the latest published literature in the field of fouling mitigation techniques for oily wastewater. It was found that membrane surface modification, chemical cleaning, membrane oscillation, pore structure, back flushing, and ultrasound are among the most common methods used for fouling mitigation. Therefore, these technologies were studied in detail and their limitations were reflected upon. Finally, the current status of these technologies was studied, and future trends were drawn out.

The aim of this study was to explore the impact of thermally rolled polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN) electrospun nanofibers (ESNF) as substrates to produce thin-film composite (TFC) forward osmosis (FO) membranes with better characteristics. Different loadings of PAN (0–10 wt%) were used to prepare PVDF/PAN ESNF substrates, and their surface morphology and structural properties were systematically studied. Before the deposition of the polyamide layer by interfacial polymerization, the ESNF substrates were subjected to continuous thermal rolling pretreatment to improve their mechanical stability. The water flux of 33.3 L/m2h and 42.3 L/m2h was achieved for the TFC-10 membrane with 10 wt% PAN blended PVDF ENSF substrate under FO and PRO modes, which was ~191% and ~188% higher than that of the TFC-0 membrane under FO and PRO orientations, respectively, using DI water as feed and 1 M NaCl as the draw solution. Moreover, the TFC-10 FO membrane showed improved selectivity, as indicated by the decrease in specific salt flux values (from 0.33 g/L of TFC-0–0.23 g/L for TFC-10), and a smaller structural parameter (221 µm) than the TFC-0 membrane, indicating that the influence of ICP can be reduced by the addition of PAN into PVDF ESNF substrate.

Hollow fiber membranes consisting of polyethersulfone (PES) reformed with high proportions of OH, aryl-N and alkyl-F groups in nonsolvent additives were compared for the removal of residual Cr (VI), COD, and bacteria from treated wastewater effluent by studying the underlying functional and molecular interactions during dope preparation and phase separation. These interactions were also studied and compared in the context of dope and membrane characteristics such as dope viscosity, membrane morphology, water contact angle, functionalities in the fabricated membranes, pure water permeability and rejection of residual solute. The membranes were characterized via Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FT-IR) spectroscopy and Raman spectroscopy. For nonsolvent additives with OH group, molecular weights and dope viscosity exhibited more impact on phase separation whereas for those with aryl-N and alkyl-F groups, phase separation was influenced by thermodynamic instability. Functional interactions also influenced the lumen shapes and membrane thickness. The lumens changed from spherical to elliptical-type shapes when aryl-amide and fluoroalkyl groups were added. Additives containing –OH group provided the highest contaminant rejection and the least flux whereas those containing aryl amide and fluoroalkyl groups enhanced the water permeability across the PES-based membranes but reduced the contaminant rejection. The PES membrane modified with OH group was able to reduce residual contaminant concentrations from 14 ppb Cr(VI), 36.9 ppm COD, and 18,300 ppm total bacterial counts (TBC) to 8.3 ppb Cr(VI), 20.3 ppm COD, and 8601 ppm TBC with an intrinsic water permeability of 22.94 LMH/bar.

A novel estimation of membrane specie permeability coefficient ( K s i ) in a polycomposite electro-membrane bioreactor (eMBR) was carried out in this study. The susceptibility of the eMBR to membrane fouling was assessed via the estimation of the temporal variations of K s i and specific cake resistance (α). These membrane fouling parameters and unit cost of treated water produced from the eMBR are being reported for the first time. The increasing order of K s i for individual measured contaminants was PO43−-P K s i obtained for COD, NH4+-N, PO43−-P, Ni, Fe and Cr were 20, 33, 1.0, 58, 70, and 102 mg/d.m2, respectively. The peak value of α obtained was 33.7 × 109 m/kg. This means that heavy metals were more permeable through the membrane than COD and nutrients and the specific cake filtration was much lower than the typical range. These results were also confirmed by a reduction in the rate of membrane fouling, as established by the peaks and troughs of the transmembrane pressure. With an operational life time of 15 years, the unit cost of treated water obtained was $0.86/m3. This assessment presents the studied method as more cost-competitive than many wastewater treatment approaches.

Electrokinetic cells with three different electrode arrangements were supplied with raw seawater collected from the Gulf. The electrode arrangements included anode-cathode (A-C), anode-cathode-cathode-anode (A-C-C-A), and cylindrical (three cathodes surrounded by an anode) configurations. The electrokinetic cells were tested at different current densities ranging from 0.05 to 0.2 mA/cm2 for 6 h. The results showed that inorganic ions and bacteria removal increased with increasing current density. For example, at a current density of 0.2 mA/cm2, 78, 76, and 91% of the Mg2 + ions were removed by the A-C, A-C-C-A, and cylindrical configurations, respectively, whereas these cells removed 64, 63, and 51% of the Mg2 + ions, respectively, at a current density of 0.1 mA/cm2. In addition, the A-C, A-C-C-A, and cylindrical cells removed 21, 40, and 44% of the Ca2 + ions, respectively, and 47, 79, and 79% of the SO42 − ions, respectively, at a current density of 0.2 mA/cm2. The removal efficiencies obtained with the A-C, A-C-C-A, and cylindrical cells were 15, 18, and 13%, respectively, for Ca2 + and 47, 26, and 22%, respectively, for SO42 − at a current density of 0.1 mA/cm2. Furthermore, nearly all of the bacteria were removed under the tested operating conditions (total bacteria count (TBC) was zero).

TiO2-based commercial membranes were coated with SiO2 nanoparticles using solgel dip coating. Membranes were characterized using FTIR, SEM, contact angle and were also tested for the COD removal efficiency. Membrane coating was confirmed from FTIR spectra. SiO2 coating enhanced membranes hydrophilicity.

eMBR is recently developed technology for wastewater treatment. Nanoporous hollow fiber PES membranes were fabricated and tested for eMBR post-treatment. α-MnO2/TiO2 inorganic membranes were fabricated, characterized, and tested for eMBR post-treatment. PES-fβCD mixed matrix membranes were fabricated, characterized, and tested for eMBR post-treatment.

PES/GO mixed matrix membranes were fabricated and characterized. Water permeability tests, hydrophilicity, and surface morphology characterizations were conducted. A max of 2870 L/m2 h water flux and contact angle of 64.5° were achieved.

Developing hybrid ultrafiltration (UF) membranes with high permeability and low fouling tendency is important for a wide range of wastewater treatment applications. Herein, we report the synthesis of novel environmental-friendly sulfonated functionalized polydopamine (SPDA) nanocomposite as a nanofiller for UF membranes. Firstly, mussel-inspired PDA nanoparticles (NPs) were synthesized based on oxidation and self-polymerization of dopamine monomer. PDA NPs were subsequently sulfonated with 3-mercapto-1-propane sulfonic acid (a thiol with –SO3H group) through Michael's addition reaction to produce the SPDA nanofiller. Fourier transform infrared spectroscopy and zeta potential measurements verified the functionalization of the PDA. Hybrid UF membranes were then fabricated via the non-solvent-induced phase separation process (NIPS), using polyethersulfone (PES) as a matrix and SPDA nanofiller at different loading levels (0–4 wt%). The water contact angle values showed an increase in the hydrophilicity of the fabricated UF membranes. The water permeability and antifouling capability of the hybrid UF membranes were dependent on the nanofiller's loading quantity. At 1 bar feed pressure, the pure water flux of the 2 percent SPDA nanofiller membrane was 2.7 times higher than that of the pristine membrane. Foulant solutions have been used to determine the antifouling efficiency of the hybrid membranes using sodium alginate (SA), humic acid (HA) and bovine serum albumin (BSA). The antifouling properties of the PES membranes have been significantly improved by incorporating the SPDA nanofillers in accordance with the foulant rejection and flow recovery ratios. The results indicated that SPDA nanofillers have great potential to improve the permeability and antifouling properties of PES membranes. Capsule: High-flux and antifouling PES hybrid membranes fabricated using environmentally-friendly sulfonated functionalized polydopamine nanofillers.

Wastewater produced from oil and gas industries contains high levels of organic and inorganic pollutants in the form of emulsions sized below 10 μm. The beneficial reuse of oily wastewater requires advanced treatment methods to remove these emulsions and promote cleaner production. This work has attempted to investigate the hybridization of electrocoagulation (EC) process, ceramic microfiltration membrane, and ozonation as a one-pot solution for the treatment of oily wastewater. The variables in this study included hydraulic retention time (HRT), aeration, current density (CD), mode of power supply, and initial pH of the sample. Aerated electro-membrane reactor contributed to a maximum COD reduction of 18.0% as opposed to 53.1% for the ozonated reactor. The effectiveness of the novel hybrid reactor could be attributed to the enhancement of electrocoagulation process by the ozone, which facilitated size-exclusion by the submerged membrane. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) were performed to characterize the generated foam, electrodes, and sludge. The present findings indicate that the ozonation-assisted electro-membrane hybrid method has the potential to be employed for the treatment of oily wastewater.

In this work, a new configuration of an electrically-enhanced membrane bioreactor has been introduced to treat medium strength wastewater at Masdar City, Abu Dhabi, United Arab Emirates (UAE). The integrated setup enhanced the reduction of wastewater contaminant concentrations. The investigated components in this study were chemical oxygen demand (COD), orthophosphates (PO 4 3− -P) and ammonium (NH 4 + -N). The percentages of COD, PO 4 3− -P, and NH 4 + -N removal obtained were 98, 99, and 98%, respectively. Variation in environmental compositions such as mixed liquor dissolved oxygen (DO), volatile suspended solids (MLVSS), pH, and electrical conductivity influenced the effluent concentration of wastewater components. Artificial neural networks (ANNs) based ensemble model was used to model the experimental findings of COD, PO 4 3− -P and NH 4 + -N removal given the initial mixed liquor compositions. Comparison between the model results and experimental data set gave high correlation coefficients for COD ( r = 0.9942), PO 4 3− -P ( r = 0.9998) and NH 4 + -N ( r = 0.9955).

Conventional water-induced polyvinylidene fluoride (PVDF) hydrophobic membranes for membrane distillation (MD) are highly prone to fouling and wetting by the different foulant constituents present in seawater. This research study was aimed at investigating the effect of various foulants on the performance of intrinsically superhydrophobic PVDF (Super H-PVDF) membrane fabricated by ethanol induced phase inversion. The fouling resistance of three types of PVDF membranes including superhydrophobic PVDF, conventional water-induced PVDF (Conv-PVDF), and commercial PVDF (Com-PVDF) membrane were compared. The effects of organic, inorganic, and bio-foulants were investigated using synthetic and raw seawater in direct contact membrane distillation (DCMD) system. Different membrane characterization tools such as scanning electron microscopy (SEM), atomic force microscope (AFM) and energy-dispersive X-ray (EDX) spectroscopy were used. Results showed that the rate of membrane fouling was insignificant in the Super H-PVDF membrane when compared to both Conv-PVDF and Com-PVDF membranes. Despite the thick layer of silica which was observed on the surface of the Super H-PVDF membrane, higher water flux was reported. The permeate quality remained high, reporting 99.9% rejection with the presence of four foulants when compared to both Conv-PVDF (94–98%) and Com-PVDF (93–97%) membranes. The unique property of intrinsically Super H-PVDF owing to its interconnected fibrous structure along with 80% porosity has resulted in anti-wetting and anti-fouling capacity. The outcomes of this research study demonstrate a great potential for membrane fouling reduction in the field of seawater desalination using MD systems.

In this study, commercial hydrophobic polyethylene (PE) membranes were impregnated with 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]) hydrophilic ionic liquid (IL) and tested for the rejection of metals ions. Three homogenous mixtures containing ethanol and IL with ethanol: IL volume ratio of 15:5 (M-IL1), 12:8 (M-IL2), and 10:10 (M-IL3) were prepared. The impregnation of the IL was ascertained using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Structural and surface characteristics of the membranes, including porosity, water contact angle, tensile strength, and surface charge, were studied. Results showed that the IL impregnation has led to remarkable changes in the surface properties of the PE membrane. For instance, the water contact angle and surface porosity of the membranes have decreased from 130.1 ± 1.5° to 94.5 ± 6.7°, and from 85% to 10% in the PE and M-IL3 membranes; respectively. The heavy metal ions Cd2+, Ni2+, and Zn2+ rejection percentage has increased from 35.73 ± 4.41, 39.40 ± 1.23, and 52.89 ± 3.08% in the pristine PE membrane to 52.87 ± 1.82, 51.47 ± 0.61, and 68.05 ± 1.27%; respectively in the M-IL3 membrane. This removal was reported at pure water flux of 22.12 ± 1.22 L m−2 h−1. The enhanced removal was attributed to the ability of the IL DCA- anion to form stable complexes with the heavy metal cations through ion exchange, the formation of hydroxides species, and electrostatic attraction forces. The new membranes have great potential for their application in the remediation of industrial wastewater containing heavy metal ions.

Global consideration has been growing recently to tackle the toxic and carcinogenic effects of heavy metal presence in water streams. In this work, novel polyvinylidene fluoride (PVDF)/tin(IV) oxide (SnO2) ion exchange membranes were prepared via the phase inversion method and their performance and properties were analyzed. The results showed that the addition of SnO2 nanoparticles (SnNPs) led to an improvement in the pure water flux from 25.5 ± 1.5 L/m2.h in the pristine PVDF membrane to 250.5 ± 12.5 L/m2·h in the 1.00 wt% PVDF/SnNPs membranes. This was related to the increase in the overall porosity and hydrophilicity of the membranes. Additionally, the 0.25 wt% PVDF/SnNPs membrane reported the highest tensile strength equal to 21.3 ± 0.6 MPa compared to only 14.3 ± 0.4 MPa in the pristine PVDF membrane. Lastly, the maximum removal of Pb2+, Cu2+, Zn2+, Cd2+, and Ni2+ was achieved by the 0.25 wt% PVDF/SnNPs membrane with around 93.9 ± 1.7, 92.8 ± 1.3, 82.3 ± 2.0, 70.7 ± 1.1, and 63.9 ± 1.5%, respectively, compared to 93.5 ± 1.3, 92.9 ± 1.7, 68.3 ± 2.1, 50.3 ± 1.8, and 50.3 ± 1.4% in the pristine PVDF membrane. The mechanism of removal was predicted to be a combination of ion exchange/adsorption, inner-sphere complexations and electrostatic attraction between the metal ions and the SnNPs. Such a PVDF/SnNPs membranes have great potential in the field of wastewater treatment.

In this study, phase-inverted polyethersulfone (PES)-maghemite (γ-Fe2O3) composite membranes were fabricated and tested for oil-water separation. The performance of five different composite membranes with various loadings of γ-Fe2O3 (0.25, 0.50, 0.75, and 1.00 wt.%) in terms of water flux, flux recovery, and oil rejection was investigated. The surface morphology, crystallinity, and functionalities of the membranes were characterized via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR). Furthermore, the porosity, pore size, water contact angle, and underwater oil contact angle of the composite membranes were examined. Results showed that the pristine PES membrane reported a pure water flux of 1242 ± 12 L/m2h (LMH) compared to 1323 ± 27 LMH for the 0.25 wt.% PES/γ-Fe2O3 membrane. Additionally, 56 and 23 % flux recovery ratio (FRR) were reported for the PES/γ-Fe2O3 and the pristine PES membrane, respectively. Also, the removal efficiency has increased from 39.2 % in the PES membrane to 81.7 % in the 1.00 wt.% PES/γ-Fe2O3 composite membrane. Two phenomena played a role in the removal trends, namely size exclusion and electrostatic repulsion forces. The developed membranes exhibited significant application potential for the removal of oil from wastewater.

Thin film deposition (TFD) allows for precise tuning of the chemical and physical properties of a membrane to improve performance, including the selectivity, flux, chemical resistance, and antifouling and antimicrobial properties. TFD techniques have a unique advantage over other traditional surface modification methods (e.g., grafting) vis-a-vis their applicability to low-surface energy polymers, which usually resist modification through other techniques. TFD is also an economical approach to surface modification as inexpensive base materials can be functionalized with small amounts of more expensive active chemistries. Here, we review a range of TFD techniques and their applicability for the modification of polymeric membranes to improve durability and performance across water treatment applications. The discussed techniques include sputtering, thermal evaporation, chemical vapor deposition, atomic layer deposition, electrochemical deposition, electron beam deposition, Langmuir-Blodgett deposition, and colloidal deposition. We review how recent developments in TFD techniques have made these methods a competitive alternative to other methods of membrane modification and discuss how modified membranes lead to improved performance for water applications, including microfiltration, nanofiltration, reverse osmosis, and membrane distillation. Relative advantages of each coating process are discussed. We also discuss how process parameters for the various TFD techniques (deposition speed, versatility, conformality, thickness, bonding strength, temperature, etc.) influence the final chemical and physical properties of modified membranes. We conclude with an outlook for how further developments in TFD techniques will continue to introduce new possibilities for unique membrane properties and applications.

In this study, three routes of nucleophilic substitution of graphene oxide (GO) were compared for the fabrication of novel polyethersulfone-functionalized GO (PES-fGO) mixed matrix membranes. These routes were: crosslinking of GO with maleic acid containing nucleophilic dicarboxyl groups (M1); co-polymerization of GO with hyperbranched polyethyleneimine (HPEI) with excess amino group (M2); and nucleophilic modification of GO with naturally-derived chitosan containing amino and hydroxyl groups (M3). These membranes were then characterized and tested for the treatment of electrokinetically remediated wastewater. Membrane properties such as mechanical strength, morphology, chemical functionalities, hydrophilicity and pore structures were measured to assess the membranes in relation to their performance. M2 membrane displayed the least open and densest structure due to the abundance of nucleophilic amino groups on HPEI. The flexible N H chains increased the resistance of the active layer to water and contributed to the lowest water fluxes provided by M2 membrane. Regardless of viscous hindrance, intermolecular bonds with higher energies (C O in M1 and O H in M2) promoted thermodynamic instability which increased the pore sizes and water fluxes through M1 and M3. Therefore, the highest tensile strength and allowable load were exhibited by M2 membrane. The CO NH linkages in M2 contributed to the highest overall pollutant removal efficiencies: 97.1% Fe2+, 95.3% Zn2+, 92.7% Cd2+, 99.9% Cr6+, 99.9% bacteria, and 98% chemical oxygen demand (COD) due to stronger repulsive electrostatic force and nano-sized membrane pores.

Pharmaceutical active compounds (PhACs) have been detected at significant concentrations in various natural and artificial aquatic environments. In this study, electro membrane bioreactor (eMBR) technology was used to treat simulated municipal wastewater containing widely-used pharmaceuticals namely amoxicillin (AMX), diclofenac (DCF) and carbamazepine (CBZ). The effects of varying current density on the removal of PhACs (AMX, DCF and CBZ) and conventional pollutants (chemical oxygen demand (COD), dissolved organic carbon (DOC), humic substances, ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N) and orthophosphate (PO4-P) species) were examined. High COD and DOC removal efficiencies (~100%) were obtained in all the experimental runs regardless of applied current density. In contrast, enhanced removal efficiencies for AMX, DCF and CBZ were achieved at high current densities. Membrane fouling rate in eMBR with respect to conventional MBR was reduced by 24, 44 and 45% at current densities of 0.3, 0.5 and 1.15 mA/cm2, respectively. The mechanism for pharmaceutical removal in this study proceeded by: (1) charge neutralization between negatively-charged pharmaceutical compounds and positive electro-generated aluminium coagulants to form larger particles and (2) size exclusion by membrane filtration.

The treatment of oily wastewater continues to pose a challenge in industries worldwide. Membranes have been investigated recently for their use in oily wastewater treatment due to their efficiency and relatively facile operational process. Graphene oxide (GO) and silica (SiO2) nanoparticles have been found to improve membrane properties. In this study, a polyethersulfone (PES) based GO-SiO2 mixed matrix membrane (MMM) was fabricated, using the phase inversion technique, for the treatment of oil refinery wastewater. The PES/GO-SiO2 membrane exhibited the highest water flux (2,561 LMH) and a 38% increase in oil removal efficiency by comparison to a PES membrane. Compared to PES/GO and PES/SiO2 membranes, the PES/GO-SiO2 MMM also displayed the best overall properties in terms of tensile strength, water permeability, and hydrophilicity.

Polymers are sometimes preferred for membrane filtration because they are more flexible, easier to handle, and less expensive than inorganic membranes fabricated from oxides, metals, and ceramics. The polymers are used as the membrane active layer and porous support in reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), microfiltration (MF) processes. However, the application of polymers for filtration suffers critical drawbacks, such as the chemical attack of polymers, membrane fouling, and hydrophobicity of most polymers. In this chapter, the polymers used for membrane filtration in recent studies and their fabrication procedures are presented and discussed. The polymers used in recent applications include cellulose acetate (CA), polyamide (PA), polyvinylidene fluoride (PVDF), polysulfone (PSF), polyethersulfone (PES), polyvinyl chloride (PVC), polyimide (PI), polyacrylonitrile (PAN), polyethylene glycol (PEG), polyvinyl alcohol (PVA), poly(methacrylic acid) (PMAA), poly(arylene ether ketone) (PAEK), poly(ether imide) (PEI), and polyaniline nanoparticles (PANI). A new polymeric material named polyethersulfone amide (PESA) has also been presented recently. Most of the recent studies have focused on improving the specific energy consumption, salt rejection, water flux, chemical resistance and antifouling properties of polymeric membranes and nanocomposites through blending and surface modification techniques. These techniques involve the use of zwitterionic coatings, sulfonated poly(arylene ether sulfone) (SPAES), perfluorophenyl azide (PFPA), carbon nanotubes (CNTs) and graphene oxide (GO) as nanofillers, polyether ether ketone (PEEK), and nanoparticles such as titanium dioxide (TiO2), and mesoporous silica. The use of polymers for filtration is still gaining tremendous attention, and further improvements of polymeric characteristics for enhanced membrane performance are expected in the coming years.

Polyvinylidene fluoride (PVDF) membranes are widely used in membrane industry, especially for membrane bioreactors (MBRs). Many PVDF membranes contain residual polyvinyl pyrrolidone (PVP) that acts as a pore-forming additive. The presence of residual PVP in some commercial PVDF membranes is often not specified and, therefore, its impact is mostly overlooked in the literature. In this study, we investigated the effect of PVP leaching on membrane structure and its implication on membrane fouling in a lab-scale MBR. PVP leaching can occur in two ways: (1) over the course of filtration from PVDF/PVP blend membranes or (2) prior filtration operation by treating the aforementioned membrane. We prepared PVDF, PVDF/PVP blend, and PVDF/PVP blend post-treated with sodium hypochlorite (NaClO), then assessed their performance. Leaching of PVP prior to the filtration operation significantly enlarged membrane pore size and thus reduced the membrane resistance. However, this advantage was dismissed during operation in MBR because PVP leaching also induced surface hydrophobicity that promoted membrane fouling, suggesting the detrimental effect of post-treatment. For PVDF/PVP blend sample, two counter-acting phenomena occurred: (1) slow leaching of PVP which gradually enlarged the membrane pores and rendered the membrane surface more hydrophobic and (2) adsorption of foulants that formed a secondary layer atop of membrane surface, restricted the pore mouth, and rendered the surface hydrophilic. The findings are significant since the change of membrane morphology over the course of filtration, as demonstrated in this study, is often overlooked when assessing membrane performance.

In this paper, current and recent advances in polymeric and nano-enhanced membrane development for reverse osmosis have been reported in terms of membrane performance and fouling. Graphene, zeolites, carbon nanotubes, silica, silver, and titanium dioxide are the predominantly tested nanoparticles in current and recent investigations. Membranes from graphene, zeolites, and carbon nanotubes have all been shown to enhance membrane water permeability. Silica has been observed to exhibit high affinity for water and improve the hydrophilicity of RO membranes. Silver and titanium dioxide have strong antimicrobial properties and can be included in RO membranes to reduce biofouling. However, the use of nanomembranes for commercial and industrial RO applications is still under development as their scalability is still a challenge. Polymeric membranes, such as cellulose acetate and polyamide, and their integration with other polymers or nanoparticles have also been presented in this paper. Overall, the choice of membrane materials for future RO processes would depend largely on the required permselectivity and the targeted foulants. However, membrane performance and antifouling features would have to be taken into consideration for sustainability of the type of RO membrane desired for a specific application.

In this paper, a numerical model of an electrically enhanced membrane bioreactor (MBER) was developed. MBER is a reactor that combines biological decomposition, membrane filtration and electrocoagulation of wastewater pollutants in a hybrid unit. To assess its design, the final contents and removal efficiencies of organics, nutrients, and metals were carried out using varying influent compositions. In a 60-day test of a laboratory-scale MBER, experimental results were used to calibrate and validate the model. The modeling results were in agreement with the experimental data and showed that the MBER can remove 99% of total phosphorus (TP), 99.9% of chemical oxygen demand (COD), 91% of total nitrogen (TN), 79% of nickel (Ni), 89% of iron (Fe), and 80% of chromium (Cr), using a current density of 15 A/m(2) intermittently supplied in a cycle of 5 min ON and 15 min OFF.

Forward osmosis (FO) is one of the evolving membrane technologies in desalination with recent expanded new interest as a low energy process. The most significant parts of FO process are the membrane and draw solution since both play a substantial role in its performance. Hence, the selection of an appropriate membrane and draw solution is crucial for the process efficiency. Improvements in the development of membranes and draw solutes have been recorded recently. However, limitations such as fouling of FO membranes, reverse solute flux, concentration polarization, and low permeate flux in standalone FO systems. This work targets the review of recent progress in FO, aiming on the prospects and challenges. It starts with addressing the advantages of the FO process. The crucial part of this review is a thorough discussion of hybrid FO systems, different FO membranes, and draw solutes available coupled with their effects on FO performance. Finally, the future of FO for sustainable desalination is also discussed.

Given their unique structural and morphological features, nanomaterials have gained considerable attention for their applications in membrane desalination. Recent advances in nanomaterial-incorporated membranes have resulted in membranes with very high water flux and salt rejection, both being sought after in membrane desalination. Nevertheless, the economic feasibility of scaling up such membranes remains questionable. The present paper surveyed the recent published literatures and current studies on nanomaterials and their applications in membrane desalination. The goal of this work was to reveal, through reviewing experimental and computational studies, the potential of nanomaterials in desalination. The paper reviewed three of the most studied nanomaterials in membrane desalination namely; carbon nanotubes, zeolites, and graphene. The investigation included preparation and synthesis of nanomaterial membranes, their properties with respect to desalination, and their applications in membrane desalination. This includes different membrane processes, and opportunities and challenges of those materials in desalination applications. The environmental and economic sustainability of nanomaterials in desalination for future prospects has also been presented.