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Membrane distillation (MD) is a low-grade heat-based emerging technology found viable for seawater desalination. Membrane properties such as high hydrophobicity, mechanical strength, and thermal stability are crucial in assessing the compatibility of a membrane for use in this application. In this work, multiwall carbon nanotubes (MWCNTs) were modified with oleylamine (Ol), which is an 18-carbon chain hydrocarbon. The attachment of oleylamine was confirmed via thermal gravimetric analysis (TGA). The modification resulted in an increase in the contact angle (CA) of MWCNTs from 104.0±2.1 to 140.5 ± 6.5°. Non-solvent Induced Phase Separation (NIPS) was then used to fabricate five polyvinylidene fluoride (PVDF) based composite membranes by varying nanomaterial concentration from 0 up to 15 wt% of the polymer. The incorporation of the nanomaterial in the membrane was confirmed via SEM, and fourier-transform infrared radiation. CA, porosity, liquid entry pressure (LEP), and tensile strength were utilized to investigate the membrane properties. A 5% and 15% increase in the CA and LEP, respectively, was observed. An increase in the tensile properties was also achieved, where the membrane consisting of 5.0 wt% nanomaterial exhibited maximum tensile stress of 34.0 MPa, compared to 23.6 MPa in the pristine PVDF. The developed nanomaterials were found to enhance the membrane properties and result in a stable overall flux of the MD system.

Removal of emulsified water in oil (w/o) emulsions are the most challenging compared to free water and dissolved water emulsions. Emulsified w/o cannot be removed by conventional techniques such as settling tanks, oil skimmers, floatation and magnetic technologies. Membrane technology is a highly efficient, energy saving, and pollutant free alternative. In this work, iron oxide-oleylamine nanoparticles have been synthesized and embedded into polylactic acid (PLA) to make a hydrophobic-super-oleophilic ultrafiltration membrane. The concentration of the nanoparticles was varied from 0.5 to 3% of the polymer. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Fourier-transform infrared radiation (FTIR) were utilized to confirm both the attachment of the oleylamine on the iron oxide and the loading of the prepared nanoparticles into the PLA membrane. The water contact angle was found to increase steadily as the concentration of the nanocomposites increased. This was associated with the hydrophobicity of the membranes, allowing the oil to penetrate through the membrane. Moisture removal in surfactant‐stabilized w/o emulsions reached up to 80% in the composite membranes, compared to only 52% in the pristine PLA. The maximum permeability was found to be at 2% loading, where 885 L/m2.h/bar was reported, compared to 500 L/m2.h/bar in the PLA. The abundance of iron-oxide, and the biodegradability of PLA prove the capability of the prepared membranes to be a viable and environmentally friendly alternative for w/o separation.

Heavy metals (HMs) are highly toxic water pollutants abundant in industrial wastewater. Herein, a bis[3-(trimethoxysilyl)propyl]amine (BTMSPA) cross-linked multiwalled carbon nanotube (MWCNT) nanomaterial (CQACNT) was synthesized by silanization of MWCNT-OH followed by grafting of positively charged quaternary ammonium groups (glycidyl trimethyl ammonium chloride (GTMAC)) by an epoxide ring-opening reaction. The composite membranes were prepared by the incorporation of CQACNT into the poly(ether sulfone) (PES) polymer matrix. The CQACNT-6 composite membrane exhibited a 3.5-fold increase in pure water permeability (PWP; 312.8 L m−2 h−1 bar−1) as compared to the pristine PES (CQACNT-0) membrane (89.6 L m−2 h−1 bar−1). Moreover, the CQACNT-6 composite membrane showed high HM removal rates (Pb: 89.53%; Ni: 90.42%; Cu: 91.43%; Zn: 91.86%) as compared to the CQACNT-0 membrane (Pb: 39.73%; Ni: 40.32%; Cu: 42.52%; and Zn: 43.91%). After 9 treatment cycles, the CQACNT-6 membrane retained up to 87%, and 94% of its initial PWP and initial Cu2+ rejection, respectively, compared to only 58%, and 54%, respectively for pristine CQACNT-0. The positively charged quaternary ammonium groups enhanced the surface features of PES and MWCNTS, resulting in competitive HM removal rates due to the electrostatic repulsion between the HM and the porous membranes, as well as high PWP.

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.

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.

This review paper aims to identify the main sources of carbon dioxide (CO2) emissions from wastewater treatment plants (WWTPs) and highlights the technologies developed for CO2 capture in this milieu. CO2 is emitted in all the operational units of conventional WWTPs and even after the disposal of treated effluents and sludges. CO2 emissions from wastewater can be captured or mitigated by several technologies such as the production of biochar from sludge, the application of constructed wetlands (CWs), the treatment of wastewater in microbial electrochemical processes (microbial electrosynthesis, MES; microbial electrolytic carbon capture, MECC; in microbial carbon capture, MCC), and via microalgal cultivation. Sludge-to-biochar and CW systems showed a high cost-effectiveness in the capture of CO2, while MES, MECC, MCC technologies, and microalgal cultivation offered efficient capture of CO2 with associate production of value-added by-products. At the state-of-the-art, these technologies, utilized for carbon capture and utilization from wastewater, require more research for further configuration, development and cost-effectiveness. Moreover, the integration of these technologies has a potential internal rate of return (IRR) that could equate the operation or provide additional revenue to wastewater management. In the context of circular economy, these carbon capture technologies will pave the way for new sustainable concepts of WWTPs, as an essential element for the mitigation of climate change fostering the transition to a decarbonised economy.

Waterborne enteric viruses that are commonly found in wastewater can cause several sporadic cases of diseases and outbreaks as a result of water or food contamination. Their detection, quantification, and effective removal from wastewater is of great importance. In this context, this review paper describes the different types of waterborne enteric viruses that are frequently found in wastewater and evaluated the various techniques developed for their concentration and detection. Furthermore, the review comprehensively discusses the different traditional, membrane filtration, and advanced/hybrid technologies used in the removal of these viruses. Over the past few decades, several efforts have been made to employ the membrane-based and other hybrid technologies to eliminate waterborne enteric viruses effectively. In this regard, technologies, such as microfiltration (MF), ultrafiltration (UF), membrane bioreactor (MBR) among others, have been widely applied. The major concerns related to these technologies are in the factors that would have an impact on membrane performance in terms of viruses' removal efficiency and sustainable operation. The advantages, limitations, and other related factors of the application of these technologies will be discussed in this review. Lastly, Light will be shed on the future perspectives and research opportunities for the widespread implementation of these technologies in the treatment of viruses-rich wastewater., The authors appreciate the support provided by the Center for Membranes and Advanced Water Technology (CMAT) at Khalifa University of Science and Technology (Abu Dhabi, UAE) (Award No. RC2-2018-009).

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.

Many emerging contaminants (ECs) are not currently removed by conventional water treatment methods and consequently, often reach the aquatic environment. In the absence of proper management strategies, ECs can accumulate in water bodies, which poses potential environmental and health risks. This paper critically reviews, for the first time, the reported occurrence and treatment of ECs in the Middle Eastern and North Africa (MENA) region. The paper also provides recommendations to properly manage EC risks. In the MENA region, pharmaceuticals and personal care products (PPCPs) have been detected in surface water, seawater, groundwater, and wastewater treatment plants. A focus on surface water in the published literature suggests that studies are skewed towards worldwide trends, whereas studies on ECs in seawater are of great importance in the study region. The types of PPCPs detected in the MENA region vary, but anti-inflammatories and antibiotics dominate. In comparison, microplastics have mainly been studied in surface waters and seawater with much less focus on drinking water. The majority of microplastics in the region are secondary types resulting from the degradation of larger plastic debris; polyethylene (PE) and polypropylene (PP) fibers are the most frequently detected polymers, which are indicative of local anthropogenic sources. Research progress on ECs varies between countries, having received more attention in Iran and Tunisia. Most MENA countries have now begun monitoring water bodies for ECs; however, studies are still lacking in some countries including Sudan, Djibouti, Syria, Ethiopia, and Bahrain. Based on this review, critical knowledge gaps and research needs are identified. Countries in the MENA region require further research on a broader range of EC types. Overall, water pollution due to the use and release of ECs can be tackled by improving public awareness, public campaigns, government intervention, and advanced monitoring and treatment methods.

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.

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.

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.

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.