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Post-combustion carbon capture (PCC), which can be retrofitted to existing units in power plants worldwide, is regarded as the first technologically feasible and effective way to combat human-induced climate change. The membrane contactor is an emerging and promising membrane technology for PCC as it integrates the benefits of both liquid absorption (high selectivity) and membrane separation (modularity and compactness). This review aims to provide a state-of-the-art assessment of the research work carried out so far on membrane contactor technology in PCC. It details common aspects of membrane contactors, such as technological advantages, membrane wetting, mass transfer and module design, as well as new advances (e.g., new membranes and absorbents used in absorption processes) and novel applications (e.g., direct CO 2 stripping and integrated heat recovery in desorption processes). Moreover, the difference in performance between membrane absorption and conventional absorption is also compared and discussed. Lastly, we discuss the status and progress of membrane contactors in PCC and offer some recommendations for future work. This paper provides a clear overview on the recent developments of membrane contactor technology in PCC. [ABSTRACT FROM AUTHOR]

Over the past decades, water scarcity and security have significantly stimulated the advances of reverse osmosis (RO) technology, which dominates the global desalination market. However, deterioration of membrane separation performance caused by inevitable fouling, including organic fouling, inorganic fouling, colloidal fouling and biofouling, calls for improved RO membranes with more durable antifouling properties. In this review, we analyze the correlations between membrane properties (e.g. surface chemistry, morphology, hydrophilicity, and charge) to antifouling performance. We evaluate the three key strategies for engineering fouling resistant thin film composite RO membranes, namely: (1) substrate modification before interfacial polymerization, (2) incorporating (hydrophilic/biocidal/antifouling) additives into the selective layer during interfacial polymerization, and (3) post (surface) modification after interfacial polymerization. Finally, we offer some insights and future outlooks on the strategies for engineering next generation of high performance RO membranes with durable fouling resistance. This review provides a comprehensive, state-of-the-art assessment of the previous efforts and strategies as well as future research directions for engineering antifouling RO membranes. Unlabelled Image • We analyze the correlations between membrane properties to antifouling performance; • Key strategies for engineering antifouling RO membranes are evaluated; • We rank various materials and methods for antifouling RO membranes; • We offer insightful perspectives on engineering antifouling RO membranes; • We provide guidelines and outlooks for engineering future antifouling RO membranes. [ABSTRACT FROM AUTHOR]

• Durable face mask synthesized through electrospinning. • Low packing density and low pressure drop for comfortable face mask. • Control of morphology properties based on electrospinning conditions. • Excellent air filtration efficiency promising for reusable face masks. Airborne contaminants, including particulate matters (PM), pathogens, and gases are presenting serious health challenges. Electrospinning has emerged as a facile technique for synthesizing nanofiber membranes to be used to separate airborne contaminants. Herein, nanofiber membranes were formed from polyvinylidene fluoride (PVDF) by systematic optimization of the electrospinning process to generate highly efficient face masks. A scalable and comfort (low pressure drop) PVDF nanofiber membrane with high filtration efficiency was achieved through controlling operation parameters of electrospinning process, allowing for controlled inter-fiber spacing and fiber density, and enhanced air filtration performance, durability and comfort of wearing. The PVDF nanofiber membranes exhibited smaller fiber diameter and higher mechanical strength as compared with commercial surgical face masks. The PVDF nanofiber membranes also revealed air filtration efficiencies in the range of 95.8 to 99.7 % for the most penetration particle size (MPPS) 300 nm based on basis weight, higher than commercial surgical mask and the respiratory filter media standards. The quality factor (QF) of PVDF nanofiber membranes is double that of the commercial surgical mask. The PVDF membranes also yielded excellent water vapour transmission (WVT), water contact angle up to 138.6˚, thus supporting the designing of durable and washable membranes. This strategy opens opportunities to be used as environmentally friendly reusable face masks for the removal of ultrafine airborne contaminants, including PM, toxic gases, and pathogens. [ABSTRACT FROM AUTHOR]

[Display omitted] • A densified flexible, free-standing, all carbon nanotube (CNT) membrane is developed. • The densified CNT membrane shows an extremely high tensile strength up to 330 MPa. • The densified CNT membrane exhibits superior antifouling performance. • The densified CNT membrane enables efficient separation of two different dyes. • This study paves the way for large-scale application of all CNT separation membranes. Carbon nanotube (CNT) based membranes have shown tremendous promise for water purification. However, fabricating free-standing all CNT membranes with excellent separation and antifouling properties remains challenging. Here, a densified flexible, ultra-strong, free-standing papery all CNT membrane with excellent separation and antifouling properties is reported. The chemically densified free-standing CNT membrane has an extremely high tensile strength up to 330 MPa, four times higher than the original CNT membrane and one order of magnitude higher than most polymeric membranes. The negatively charged surface of the densified CNT membrane enables efficient separation of two dyes even with similar molecular sizes. Meanwhile, the densified CNT membrane exhibits superior antifouling performance during the filtration of dyes, humic acid and bovine serum albumin solutions, and oil-in-water emulsions due to its reinforced hydration layer induced by the hydrophilic functional groups resulting from chemical densification. The chemically densified CNT membrane shows not only excellent separation and antifouling performance, but also superior long-term stability and regeneration performance in the filtration of foulant-containing solutions. This study may pave the way for large-scale application of densified free-standing all CNT membranes in the realm of water treatment. [ABSTRACT FROM AUTHOR]

Interlayered thin-film composite (TFC) membranes are promising in overcoming the permeability-selectivity tradeoff of conventional membranes. However, fabricating high-performance TFC membranes with tunable interlayer spacing and antifouling properties remains challenging. Here we develop a high-performance self-cleaning TFC graphene oxide (GO) membrane by employing multifunctional bismuthyl bromide (BiOBr) nanosheets to construct a unique photocatalytic GO@BiOBr interlayer. BiOBr has multiple functions, including regulating the GO nanosheet spacing (i.e., the channel size), mediating the surface properties of the interlayer to enable a desirable selective layer during interfacial polymerization, and imparting photocatalytic properties to the TFC membrane. Because of the dimensional difference between GO and BiOBr nanosheets, the spacing of the dual 2D nanosheets (GO and BiOBr) can be finely tailored by adjusting BiOBr loading. Coupling of the 2D nanosheets enables tunable interlayer properties and a highly thin and selective rejection layer, leading to significantly enhanced separation performance of the TFC membrane. The GO@BiOBr interlayered TFC membrane shows a water permeability of 29.9 L·m−2·h−1·bar−1, which is six times higher than the TFC membrane without an interlayer. The GO@BiOBr interlayered TFC membrane displays 100% rejections to various small molecules (e.g., Rhodamine B, Basic Blue 26 and Ofloxacin). The rise of BiOBr loading in the GO@BiOBr composite increases the interlayer spacing of the dual 2D nanosheets, likely leading to more monomer diffusion and eruptive interfacial polymerization. As a result, thicker and rougher polyamide layers are formed, resulting in decreased water permeability of the TFC membrane. This study presents a viable approach for engineering the next generation of high-performance self-cleaning TFC membranes for reverse osmosis, forward osmosis and nanofiltration within the realm of water treatment. [Display omitted] • We developed a high-performance self-cleaning TFC membrane. • 2D GO interlayer spacing was tailored by multifunctional 2D BiOBr. • Dual 2D nanosheets enables tunable interlayer and selectivity layer properties. • Mechanism on how BiOBr affects TFC membrane structure-property relationship is elucidated. • This study sheds light on the development of the next generation of TFC membranes. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is an emerging membrane separation technology with great potential for desalination, wastewater treatment and volatile resource recovery. It becomes even more attractive as it can utilize low-grade heat or renewable energy, and treat high-salinity waste liquids towards zero liquid discharge. However, the performance of MD is often limited by the wetting of hydrophobic porous membranes during operation, leading to reduced flux and efficiency. To overcome this challenge, the development of antiwetting hydrophobic MD membranes has gained increasing attention in recent years. In this review, we examine the liquid entry pressure (LEP) and its influencing factors (e.g. the maximum pore size, surface chemistry/free energy and surface roughness/architecture) of an MD membrane, which determine the antiwetting performance of the porous MD membrane. From enhancing the LEP point of view, we propose two key strategies for engineering antiwetting surfaces: (1) reducing the membrane pore size, and (2) increasing the liquid contact angle by minimizing the surface free energy and the liquid/solid contact area through enhancing the surface roughness and/or creating hierarchical/re-entrant structures. These strategies include various specific fabrication techniques, such as surface coating, vapor deposition, layer-by-layer assembly, surface fluorination, and surface functionalization. Green surface modification materials and methods are also discussed to reduce the application of less environmentally friendly fluoride-containing compounds. Furthermore, we provide insights and future directions for the design and engineering of high-performance antiwetting hydrophobic MD membranes. Overall, this review offers a comprehensive analysis of the current state-of-the-art research in engineering antiwetting hydrophobic MD membranes, and highlights the potential for the development of next-generation MD membranes with improved performance and efficiency. [Display omitted] • We analyze the correlation between membrane properties and antiwetting performance. • Key strategies for engineering antiwetting MD membranes are evaluated. • Different methods and materials for antiwetting MD membranes are discussed. • We offer insightful perspectives on engineering antiwetting MD membranes. • This review offers comprehensive analysis and guidelines for MD membrane development. [ABSTRACT FROM AUTHOR]

Abstract Nanofiltration (NF) has attracted increasing interest for dye and NaCl fractionation in textile industry. However, it typically shows high rejections to divalent salts (i.e., Na 2 SO 4), compromising to effectively purify dye from dye/Na 2 SO 4 mixtures, which is crucial in digital ink-jet printing. This study used a tight ceramic ultrafiltration (UF) membrane (MWCO of 2410 Da) to desalinate diverse reactive dye species with molecular weights from 626.6 to 1205.4 Da. The UF membrane showed considerably high rejections to all the reactive dyes (> 98.12%) and nearly complete salt transmission (rejections < 0.1% and < 1.5% with 60 g L−1 NaCl and Na 2 SO 4 , respectively). Operational conditions, i.e., dye concentration, applied pressure and salt addition, have insignificant impacts on the dye rejection, due to dye aggregation. An integrated UF-diafiltration process, including pre-concentration, diafiltration and post-concentration, was designed to fractionate reactive dyes and Na 2 SO 4. The model dye, reactive blue 19, can be concentrated to 142.60 g L−1 with a purity of 99.83% in the process, since low salt rejection and high dye retention of the membrane allows for 99.88% salt removal and 2.3% dye loss after ca. 9 diavolumes. These results indicate that tight ceramic UF membranes have high potential as a state-of-the-art technology in reactive dyes and Na 2 SO 4 fractionation for digital ink-jet printing applications. Graphical abstract fx1 Highlights • Tight UF membrane is used in efficient dye purification for digital printing. • Tight UF membrane has consistently high rejection (> 98.12%) for 7 reactive dyes. • Integrated UF-diafiltration process removes 99.88% of Na 2 SO 4 with ~9 diavolumes. • Reactive blue 19 is concentrated to 142.60 g L−1 with 99.83% purity in diafiltration. • Complete flux recovery for UF membrane is obtained after NaOH/HCl cleaning. [ABSTRACT FROM AUTHOR]

Arsenic-contaminated water has significant adverse impacts on human health and ecosystems. We developed a new adsorptive membrane by modifying the porous support layer of a phase inversion formed membrane for arsenic removal. Iron oxide (Fe 3 O 4 ) microspheres were immobilized in the support layer of the membrane by reverse filtration, followed by dopamine polymerization. The prepared adsorptive membrane was compared with a virgin membrane without Fe 3 O 4 microspheres and a Fe 3 O 4 blended membrane in terms of membrane structures and separation performance. The adsorptive membrane prepared by our new method had comparable water permeability and rejection performance with the virgin membrane without Fe 3 O 4 microspheres, but higher rejection performance and dynamic adsorption capacity than the membrane prepared by the conventional blending method. Both static and dynamic adsorption modes were used to evaluate the adsorption performance of the membranes. Our new adsorptive membrane also had excellent regeneration performance. After three regeneration cycles, the membrane was still capable of treating more than 2 tons of As-contaminated water/m 2 . The adsorptive membrane of 1 m 2 could treat over 7 tons of water to the drinking water standard in terms of arsenic concentration during three regeneration cycles. Therefore, our adsorptive membrane may pave a new way for arsenic removal from water and ensuring drinking water security. [ABSTRACT FROM AUTHOR]

Pd-doped organosilica (POS) membranes are calcined in N 2 and steam atmospheres for hydrogen separation. Chemical compositions and microstructures of the membranes are characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and N 2 absorption-desorption measurement. Gas separation performances and hydrothermal stabilities of the membranes are also evaluated and compared. The membrane calcined in steam atmosphere (i.e. POS-S membrane) shows a high H 2 permeance (2.5 × 10 −7 mol·m −2 ·s −1 ·Pa −1 ) and H 2 /CO 2 permselectivity (9.2, doubles the Knudsen diffusion factor 4.69). Notably, compared with the POS membrane calcined in N 2 , the POS-S membrane displays more excellent hydrothermal stability throughout a 190-h test, which is superior to most silica-derived membranes reported. The significantly enhanced hydrothermal stability is mainly attributed to the low content of unstable moieties in the POS network after steam calcination. Steam conditions make unstable intermediate Pd oxide transfer into stable PdO and reduce content of inorganic moieties during the calcination, leading to high hydrothermal stability of the membrane. Therefore, calcination in steam atmosphere may offer an effective strategy to develop desirable POS membranes with high separation performances and excellent hydrothermal stabilities for practical hydrogen separation. [ABSTRACT FROM AUTHOR]

Using a tubular ceramic membrane as the transport membrane condenser for simultaneous water and heat recovery from gaseous streams is experimentally investigated in the current study. The effects of several important operational parameters (e.g. gas flow rate, coolant flow rate, transmembrane pressure and inlet gas temperature) on the process performance in terms of mass and heat transfer across the membrane are systematically studied. It is found that mass and heat transfer rates can be enhanced by increasing the gas flow rate, coolant water flow rate and the temperature of the inlet gas stream. To improve the water and heat recovery, a low gas flow rate but a high coolant flow rate should be maintained. Increasing the transmembrane pressure difference decreases the mass and heat transfer mainly due to the reduced inlet gas humidity, enthalpy and flow rate. However, water and heat recovery does not change significantly with the change in transmembrane pressure. 20–60% water recovery and 33–85% heat recovery are achievable when using cold water as the coolant. The mass transfer mechanism in membrane condensation is complex and needs further exploration. These findings offer significant implications in using transport membrane condensers for water and heat recovery from gas streams with high moisture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Superhydrophilic g-C 3 N 4 /SiO 2 composite membrane is prepared by vacuum filtration. • The g-C 3 N 4 /SiO 2 composite membrane has effective oil/water separation performance. • Incorporation of g-C 3 N 4 endows the composite membrane with photocatalytic self-cleaning property. • g-C 3 N 4 /SiO 2 composite membrane effectively retains and inactivates the bacteria. Conventional membrane processes, e.g., microfiltration and ultrafiltration, suffer from severe permeation flux decline and fouling during the oily wastewater treatment. The superhydrophilic surface decoration provides an important and effective strategy to address this challenge. Herein, a surperhydrophilic/underwater superoleophobic nanocomposite surface with the photocatalytic properties was constructed via one-step facile vacuum-assisted filtration of a g-C 3 N 4 nanosheet/SiO 2 nanoparticle dispersion onto a microfiltration membrane substrate. Specifically, with the intercalation of 20 mg∙L−1 SiO 2 nanoparticles into the g-C 3 N 4 nanosheets, the g-C 3 N 4 /SiO 2 composite membrane showed the superhydrophilic/underwater superoleophobic properties with an underwater oil contact angle of 170.0 ± 0.3°. Such a g-C 3 N 4 /SiO 2 composite membrane yielded a permeation flux of >1290 LMH·bar−1 with an oil rejection of >99.91% during the vacuum filtration of oil-in-water emulsions. The g-C 3 N 4 /SiO 2 composite membrane significantly outperformed the pristine microfiltration substrate that had severe fouling caused by oil blockage. Additionally, the g-C 3 N 4 /SiO 2 composite membrane not only effectively retained the E. coli bacteria through size exclusion effect, but also promoted the inactivation of bacteria via visible-light photocatalysis. Therefore, our membrane has a great promise in practical oily wastewater treatment due to its excellent separation performance and biofouling resistance. [ABSTRACT FROM AUTHOR]

• Removal mechanisms of PFCs by loose and tight NF membranes were analyzed. • Interactions between membrane and typical PFCs were quantified. • DFT was used to validate the interactions between PFCs and membrane surface. Perfluorinated compounds (PFCs)-membrane interactions play important roles in the removal of PFCs by membrane separation, especially in their adsorption onto membrane interfaces and membrane rejection. In this work, a loose nanofiltration (NF) membrane and a tight NF membrane were used to remove six PFCs that have different head groups and different C-F chains. The roles of typical PFCs-membrane interactions, including electrostatic repulsion, hydrophobic interactions and hydrogen bonding, on membrane adsorption and rejection were quantitatively evaluated. The membrane adsorption capacities to the six PFCs were determined by static adsorption experiments. Influences of the PFCs-membrane interactions mentioned above were quantified with six negatively charged PFCs by comparing the adsorption and rejection at neutral pH with those at the isoelectric points (IEPs) of the two membranes. Results showed that electrostatic repulsion caused that the rejections by the loose membrane and tight membrane increased by 2.2%–36.0%, and 0.8%–7.4%, respectively. Non-electrostatic interactions (hydrophobic interactions and hydrogen bonding) decreased rejections of the tight membrane and the loose membrane by 9.5%–23.6% and 1.2%–10.3%, respectively. Interactions between the PFCs and the membranes were further calculated by density functional theory (DFT). DFT analysis and Gibbs free energy changes suggest that PFCs could interact with membranes in thermodynamics. The head groups are away from the membrane surface because of electrostatic repulsion and the tail groups close to the membrane surface due to hydrophobic interactions and hydrogen bonding. [ABSTRACT FROM AUTHOR]

• A catalytic PVDF membrane functionalized with zero valent iron was fabricated. • Membrane active surfaces generate much •OH radicals through decomposition of H 2 O 2. • The membrane exhibits excellent degradation performance for toxic organics. • Our catalytic membrane shows high regeneration ability after four consecutive cycles. A hierarchical polyvinylidene fluoride (PVDF) membrane functionalized with catalytic zero valent iron nanoparticles via polydopamine/polyethyleneimine was successfully fabricated. The catalytic membrane exhibited excellent degradation performance for toxic 4-nitrophenol (4-NP), Rhodamine B (RB), and 2,4-dichlorophenol (2-CP). With a trace amount of H 2 O 2 flowing over the surface of the catalytic membrane, highly active sites were monitored. The active surfaces generated a large amount of •OH radicals via decomposition of H 2 O 2. The radicals unselectively oxidized a wide range of recalcitrant organic pollutants. Specifically, ~ 80% RB and almost 100% 4-NP and 2-CP were degraded within 30 min in aqueous solutions. Furthermore, total organic carbon analysis revealed that recalcitrant RB, 4-NP and 2-CP molecules could be partially mineralized into carbon dioxide and water inside the membrane. The degradation mechanism was related to a Fenton-like reaction. The catalytic membrane showed high regeneration ability with approximately 100% activity retention after four consecutive use cycles. [ABSTRACT FROM AUTHOR]