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Showing papers on "Membrane published in 2018"


Journal ArticleDOI
Tan Zhe1, Shengfu Chen1, Xinsheng Peng1, Zhang Lin1, Congjie Gao1 
04 May 2018-Science
TL;DR: This work uses a facile route based on interfacial polymerization to generate Turing-type polyamide membranes for water purification that exhibit excellent water-salt separation performance that surpasses the upper-bound line of traditional desalination membranes.
Abstract: The emergence of Turing structures is of fundamental importance, and designing these structures and developing their applications have practical effects in chemistry and biology. We use a facile route based on interfacial polymerization to generate Turing-type polyamide membranes for water purification. Manipulation of shapes by control of reaction conditions enabled the creation of membranes with bubble or tube structures. These membranes exhibit excellent water-salt separation performance that surpasses the upper-bound line of traditional desalination membranes. Furthermore, we show the existence of high water permeability sites in the Turing structures, where water transport through the membranes is enhanced.

896 citations


Journal ArticleDOI
TL;DR: L lamellar stacked MXene membranes with aligned and regular subnanometer channels are designed, taking advantage of the abundant surface-terminating groups on the MXene nanosheets, which exhibit excellent gas separation performance with H2 permeability >2200 Barrer and H2/CO2 selectivity >160, superior to the state-of-the-art membranes.
Abstract: Molecular sieving membranes with sufficient and uniform nanochannels that break the permeability-selectivity trade-off are desirable for energy-efficient gas separation, and the arising two-dimensional (2D) materials provide new routes for membrane development. However, for 2D lamellar membranes, disordered interlayer nanochannels for mass transport are usually formed between randomly stacked neighboring nanosheets, which is obstructive for highly efficient separation. Therefore, manufacturing lamellar membranes with highly ordered nanochannel structures for fast and precise molecular sieving is still challenging. Here, we report on lamellar stacked MXene membranes with aligned and regular subnanometer channels, taking advantage of the abundant surface-terminating groups on the MXene nanosheets, which exhibit excellent gas separation performance with H2 permeability >2200 Barrer and H2/CO2 selectivity >160, superior to the state-of-the-art membranes. The results of molecular dynamics simulations quantitatively support the experiments, confirming the subnanometer interlayer spacing between the neighboring MXene nanosheets as molecular sieving channels for gas separation. Two-dimensional materials show great potential for membrane technologies, but their disordered channels hinder their molecular sieving performance. Here, Wang, Gogotsi and colleagues design a MXene membrane with ordered nanochannels that exhibits an excellent H2/CO2 gas separation performance.

731 citations


Journal ArticleDOI
TL;DR: It is concluded that synthetic methods have evolved rapidly and development of fundamental knowledge on the many complex phenomena occurring in the adaptive membrane bulk and solution-interface environments is not sufficiently established, and much effort is required to combine experimental, theoretical, and simulation data for a more comprehensive and coherent understanding of these phenomena.

636 citations


Journal ArticleDOI
TL;DR: The fabrication of a TFC NF membrane with a crumpled polyamide (PA) layer via interfacial polymerization on a single-walled carbon nanotubes/polyether sulfone composite support loaded with nanoparticles as a sacrificial templating material is reported, yielding an overall desalination performance superior to state-of-the-art NF membranes reported so far.
Abstract: Nanofiltration (NF) membranes with ultrahigh permeance and high rejection are highly beneficial for efficient desalination and wastewater treatment. Improving water permeance while maintaining the high rejection of state-of-the-art thin film composite (TFC) NF membranes remains a great challenge. Herein, we report the fabrication of a TFC NF membrane with a crumpled polyamide (PA) layer via interfacial polymerization on a single-walled carbon nanotubes/polyether sulfone composite support loaded with nanoparticles as a sacrificial templating material, using metal-organic framework nanoparticles (ZIF-8) as an example. The nanoparticles, which can be removed by water dissolution after interfacial polymerization, facilitate the formation of a rough PA active layer with crumpled nanostructure. The NF membrane obtained thereby exhibits high permeance up to 53.5 l m−2h−1 bar−1 with a rejection above 95% for Na2SO4, yielding an overall desalination performance superior to state-of-the-art NF membranes reported so far. Our work provides a simple avenue to fabricate advanced PA NF membranes with outstanding performance. Nanofiltration membranes are important for water desalination technologies, but designing membranes that achieve both high permeance and high salt rejection remains challenging. Here, the authors use sacrificial nanoparticles in the membrane fabrication process, leading to crumpled structures with ultrahigh permeance.

516 citations


Journal ArticleDOI
TL;DR: The continuous two-dimensional imine-linked COF-LZU1 membrane with a thickness of only 400 nm was prepared on alumina tubes by in-situ solvothermal synthesis and shows excellent water permeance and outstanding water stability, rendering it an interesting system for water purification.
Abstract: Covalent organic frameworks (COFs) are attractive candidates for advanced water-treatment membranes owing to their high porosity and well-organized channel structures. Herein, the continuous two-dimensional imine-linked COF-LZU1 membrane with a thickness of only 400 nm was prepared on alumina tubes by in situ solvothermal synthesis. The membrane shows excellent water permeance (ca. 760 L m-2 h-1 MPa-1 ) and favorable rejection rates exceeding 90 % for water-soluble dyes larger than 1.2 nm. The water permeance through the COF-LZU1 membrane is much higher than that of most membranes with similar rejection rates. Long-time operation demonstrates the outstanding stability of the COF-LZU1 membrane. As the membrane has no selectivity for hydrated salt ions (selectivity <12 %), it is also suitable for the purification of dye products from saline solutions. The excellent performance and the outstanding water stability render the COF-LZU1 membrane an interesting system for water purification.

448 citations


Journal ArticleDOI
TL;DR: A broad review is carried out on wetting incidence in membrane distillation processes and describes the wetting mechanisms, wetting causes, and wetting detection methods, as well as hydrophobicity measurements of MD membranes.

446 citations


Journal ArticleDOI
TL;DR: In this paper, a review summarizes comprehensive recent studies on the removal of contaminants of emerging concern (CECs) by forward osmosis (FO), reverse Osmosis(RO), nanofiltration (NF), and ultrafiltration (UF) membrane treatments, and describes important information on the applications of FO, RO, NF, and UF membranes in water and wastewater (WW) treatment.

421 citations


Journal ArticleDOI
TL;DR: A new type of a two-dimensional layered-stacking COF-COF composite membrane in bilayer geometry synthesized on a porous support by successively regulating the growth of imine-based COf-LZU1 and azine- based ACOF-1 layers via a temperature-swing solvothermal approach is demonstrated.
Abstract: Covalent organic frameworks (COFs) have been proposed as alternative candidates for molecular sieving membranes due to their chemical stability. However, developing COF membranes with narrowed apertures close to the size of common gas molecules is a crucial task for selective gas separation. Herein, we demonstrate a new type of a two-dimensional layered-stacking COF–COF composite membrane in bilayer geometry synthesized on a porous support by successively regulating the growth of imine-based COF-LZU1 and azine-based ACOF-1 layers via a temperature-swing solvothermal approach. The resultant COF-LZU1–ACOF-1 bilayer membrane has much higher separation selectivity for H2/CO2, H2/N2, and H2/CH4 gas mixtures than the individual COF-LZU1 and ACOF-1 membranes due to the formation of interlaced pore networks, and the overall performance surpasses the Robeson upper bounds. The COF-LZU1–ACOF-1 bilayer membrane also shows high thermal and long-time stabilities.

403 citations


Journal ArticleDOI
TL;DR: Efficient incorporation of engineered submicrometre-sized metal–organic framework (MOF) crystals into polymers to form hybrid materials that successfully translate the excellent molecular sieving properties of face-centred cubic (fcu)-MOFs into the resultant membranes are reported on.
Abstract: Membrane-based separations can improve energy efficiency and reduce the environmental impacts associated with traditional approaches. Nevertheless, many challenges must be overcome to design membranes that can replace conventional gas separation processes. Here, we report on the incorporation of engineered submicrometre-sized metal–organic framework (MOF) crystals into polymers to form hybrid materials that successfully translate the excellent molecular sieving properties of face-centred cubic (fcu)-MOFs into the resultant membranes. We demonstrate, simultaneously, exceptionally enhanced separation performance in hybrid membranes for two challenging and economically important applications: the removal of CO2 and H2S from natural gas and the separation of butane isomers. Notably, the membrane molecular sieving properties demonstrate that the deliberately regulated and contracted MOF pore-aperture size can discriminate between molecular pairs. The improved performance results from precise control of the linkers delimiting the triangular window, which is the sole entrance to the fcu-MOF pore. This rational-design hybrid approach provides a general toolbox for enhancing the transport properties of advanced membranes bearing molecular sieve fillers with sub-nanometre-sized pore-apertures. Sub-micrometre MOF particles are incorporated into polymers to form mixed matrix membranes. Molecular sieving enables performance far beyond current limits for two applications, butane isomer separation and combined CO2/H2S removal from natural gas.

395 citations


Journal ArticleDOI
TL;DR: A class of reduced GO membranes with enlarged interlayer distance fabricated by using theanine amino acid and tannic acid as reducing agent and cross-linker with remarkably high permeability and stability in aqueous solution is reported.
Abstract: Increasing fresh water demand for drinking and agriculture is one of the grand challenges of our age. Graphene oxide (GO) membranes have shown a great potential for desalination and water purification. However, it is challenging to further improve the water permeability without sacrificing the separation efficiency, and the GO membranes are easily delaminated in aqueous solutions within few hours. Here, we report a class of reduced GO membranes with enlarged interlayer distance fabricated by using theanine amino acid and tannic acid as reducing agent and cross-linker. Such membranes show water permeance over 10,000 L m-2 h-1 bar-1, which is 10-1000 times higher than those of previously reported GO-based membranes and commercial membranes, and good separation efficiency, e.g., rhodamine B and methylene blue rejection of ~100%. Moreover, they show no damage or delamination in water, acid, and basic solutions even after months.

379 citations



Journal ArticleDOI
TL;DR: The novel Ag@MXene composite membrane with variable AgNP loadings achieved favorable rejection to organic foulants like bovine serum albumin (BSA) and methyl green (MG) in comparison to other reported membranes and makes Ag@ MXene layered nanosheets attractive candidates towards the development of nanofiltration membranes for water purification and biomedical applications.
Abstract: Low flux and fouling are critical issues in membrane based separation processes. Here we report a two-dimensional (2D) MXene (Ti3C2Tx) modified with Ag nanoparticles (Ag@MXene) as a promising alternative for ultrafast water purification membrane applications. The novel Ag@MXene composite membrane with variable AgNP loadings (between 0–35%) was produced by self-reduction of silver nitrate on the surface of MXene sheets in solution, where the MXene acted simultaneously as a membrane forming material and a reducing agent. The most suitable membrane, 21% Ag@MXene with 470 nm thickness and 2.1 nm average pore size, exhibited an outstanding water flux (∼420 L m−2 h−1 bar−1) compared to the pristine MXene membrane (∼118 L m−2 h−1 bar−1) under the same experimental conditions. The 21% Ag@MXene membrane demonstrated high rejection efficiency for organic molecules with excellent flux recovery. Moreover, the 21% Ag@MXene composite membrane demonstrated more than 99% E. coli growth inhibition, while the MXene membrane exhibited only ∼60% bacteria growth inhibition compared to the control hydrophilic polyvinylidene difluoride (PVDF) based membrane. Furthermore, the 21% Ag@MXene membrane achieved favorable rejection to organic foulants like bovine serum albumin (BSA) and methyl green (MG) in comparison to other reported membranes. This combination of controlled permeability and bactericidal properties makes Ag@MXene layered nanosheets attractive candidates towards the development of nanofiltration membranes for water purification and biomedical applications.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of thickness on the rate of water transport through polyamide nanofilm composite membranes for desalination by reverse osmosis.
Abstract: Thin-film composite membranes comprising a polyamide nanofilm separating layer on a support material are state of the art for desalination by reverse osmosis. Nanofilm thickness is thought to determine the rate of water transport through the membranes; although due to the fast and relatively uncontrolled interfacial polymerization reaction employed to form these nanofilms, they are typically crumpled and the separating layer is reported to be ≈50-200 nm thick. This crumpled structure has confounded exploration of the independent effects of thickness, permeation mechanism, and the support material. Herein, smooth sub-8 nm polyamide nanofilms are fabricated at a free aqueous-organic interface, exhibiting chemical homogeneity at both aqueous and organic facing surfaces. Transfer of these ultrathin nanofilms onto porous supports provides fast water transport through the resulting nanofilm composite membranes. Manipulating the intrinsic nanofilm thickness from ≈15 down to 8 nm reveals that water permeance increases proportionally with the thickness decrease, after which it increases nonlinearly to 2.7 L m-2 h-1 bar-1 as the thickness is further reduced to ≈6 nm.

Journal ArticleDOI
17 Aug 2018-Science
TL;DR: An additive approach is presented that uses electrospraying to deposit monomers directly onto a substrate, where they react to form polyamide, resulting in polyamide films that are smoother and thinner than conventional polyamides while still exhibiting good permselectivity relative to a commercial benchmarking membrane.
Abstract: Polyamide thickness and roughness have been identified as critical properties that affect thin-film composite membrane performance for reverse osmosis. Conventional formation methodologies lack the ability to control these properties independently with high resolution or precision. An additive approach is presented that uses electrospraying to deposit monomers directly onto a substrate, where they react to form polyamide. The small droplet size coupled with low monomer concentrations result in polyamide films that are smoother and thinner than conventional polyamides, while the additive nature of the approach allows for control of thickness and roughness. Polyamide films are formed with a thickness that is controllable down to 4-nanometer increments and a roughness as low as 2 nanometers while still exhibiting good permselectivity relative to a commercial benchmarking membrane.

Journal ArticleDOI
TL;DR: In this paper, the authors surveyed the recent progress in the development of polymeric membranes for membrane adsorption (MA) and showed that nanoparticles are potentially useful as fillers in the host membrane to enhance its performance.
Abstract: Application of polymeric membranes for the adsorption of hazardous pollutants may lead to the development of next-generation reusable and portable water purification appliances. Membranes for membrane adsorption (MA) have the dual function of membrane filtration and adsorption to be very effective to remove trace amounts of pollutants such as cationic heavy metals, anionic phosphates and nitrates. In this review article, recent progresses in the development of MA membranes are surveyed. In addition, recent progresses in the development of advanced adsorbents such as nanoparticles are summarized, since they are potentially useful as fillers in the host membrane to enhance its performance. The future directions of R&D in this field are also shown in the conclusion section.

Journal ArticleDOI
08 Feb 2018-Chem
TL;DR: In this article, the interfacial polymerization of polyfunctional amine and aldehyde monomers with a Lewis acid catalyst, Sc(OTf) 3, is described.

Journal ArticleDOI
TL;DR: Metal organic framework membranes, including ZIF-8 and UiO-66 membranes with uniform subnanometer pores consisting of angstrom-sized windows and nanometer-sized cavities for ultrafast selective transport of alkali metal ions are reported.
Abstract: Porous membranes with ultrafast ion permeation and high ion selectivity are highly desirable for efficient mineral separation, water purification, and energy conversion, but it is still a huge challenge to efficiently separate monatomic ions of the same valence and similar sizes using synthetic membranes. We report metal organic framework (MOF) membranes, including ZIF-8 and UiO-66 membranes with uniform subnanometer pores consisting of angstrom-sized windows and nanometer-sized cavities for ultrafast selective transport of alkali metal ions. The angstrom-sized windows acted as ion selectivity filters for selection of alkali metal ions, whereas the nanometer-sized cavities functioned as ion conductive pores for ultrafast ion transport. The ZIF-8 and UiO-66 membranes showed a LiCl/RbCl selectivity of ~4.6 and ~1.8, respectively, which are much greater than the LiCl/RbCl selectivity of 0.6 to 0.8 measured in traditional porous membranes. Molecular dynamics simulations suggested that ultrafast and selective ion transport in ZIF-8 was associated with partial dehydration effects. This study reveals ultrafast and selective transport of monovalent ions in subnanometer MOF pores and opens up a new avenue to develop unique MOF platforms for efficient ion separations in the future.

Journal ArticleDOI
TL;DR: The high separation performance and reusability of the membranes and the outstanding water stability of the MOFs suggested the developed membrane as a potential candidate for water treatment.
Abstract: Electrospun nanofiber composite membranes containing water-stable metal-organic frameworks (MOFs) particles (Zr-based MOF-808) supported on polyacrylonitrile (PAN) nanofiber synthesized via co-electrospinning have been prepared. MOF particles were dispersed in the organic polymer, and their subsequent presence was inferred by scanning electron microscopy. Membrane performance in heavy metal ion adsorption in batch filtration was evaluated on the basis of Cd2+ and Zn2+ ions sequestration. The adsorption capacities of the pristine MOF and the MOF composite membrane revealed that MOF particles in the membrane could be accessed for adsorption in the hydrophilic PAN membranes. The maximum adsorption capacities were 225.05 and 287.06 mg g–1 for Cd2+ and Zn2+, respectively. Conventional thermal activation of pristine MOF and composite membrane revealed a crystal downsizing, while “hydractivation” produced an expanded MOF with enhanced adsorption potentials. The PAN/MOF-808 “hydractivated” composite membrane coul...

Journal ArticleDOI
TL;DR: This work shows that a planarizable push–pull fluorescent probe called FliptR (fluorescent lipid tension reporter) can monitor changes in membrane tension by changing its fluorescence lifetime as a function of the twist between its fluorescent groups, and provides calibration curves that enable accurate measurement of membrane tension usingfluorescence lifetime imaging microscopy.
Abstract: Cells and organelles are delimited by lipid bilayers in which high deformability is essential to many cell processes, including motility, endocytosis and cell division. Membrane tension is therefore a major regulator of the cell processes that remodel membranes, albeit one that is very hard to measure in vivo. Here we show that a planarizable push-pull fluorescent probe called FliptR (fluorescent lipid tension reporter) can monitor changes in membrane tension by changing its fluorescence lifetime as a function of the twist between its fluorescent groups. The fluorescence lifetime depends linearly on membrane tension within cells, enabling an easy quantification of membrane tension by fluorescence lifetime imaging microscopy. We further show, using model membranes, that this linear dependency between lifetime of the probe and membrane tension relies on a membrane-tension-dependent lipid phase separation. We also provide calibration curves that enable accurate measurement of membrane tension using fluorescence lifetime imaging microscopy.

Journal ArticleDOI
07 Sep 2018-Science
TL;DR: In this article, the fabrication of ZIF nanocomposite membranes by means of an all-vapor-phase processing method based on atomic layer deposition (ALD) of ZnO in a porous support followed by ligand vapor treatment was demonstrated.
Abstract: Zeolitic imidazolate framework (ZIF) membranes are emerging as a promising energy-efficient separation technology However, their reliable and scalable manufacturing remains a challenge We demonstrate the fabrication of ZIF nanocomposite membranes by means of an all-vapor-phase processing method based on atomic layer deposition (ALD) of ZnO in a porous support followed by ligand-vapor treatment After ALD, the obtained nanocomposite exhibits low flux and is not selective, whereas after ligand-vapor (2-methylimidazole) treatment, it is partially transformed to ZIF and shows stable performance with high mixture separation factor for propylene over propane (an energy-intensive high-volume separation) and high propylene flux Membrane synthesis through ligand-induced permselectivation of a nonselective and impermeable deposit is shown to be simple and highly reproducible and holds promise for scalability

Journal ArticleDOI
TL;DR: Compared to conventional TFC nanofiltration membranes, the novel TFCn membrane successfully overcame the longstanding permeability and selectivity trade-off and paves a new avenue for fabricating high performance TFC membranes.
Abstract: Conventional thin-film composite (TFC) membranes suffer from the trade-off relationship between permeability and selectivity, known as the “upper bound”. In this work, we report a high performance thin-film composite membrane prepared on a tannic acid (TA)-Fe nanoscaffold (TFCn) to overcome such upper bound. Specifically, a TA-Fe nanoscaffold was first coated onto a polysulfone substrate, followed by performing an interfacial polymerization reaction between trimesoyl chloride (TMC) and piperazine (PIP). The TA-Fe nanoscaffold enhanced the uptake of amine monomers and provided a platform for their controlled release. The smaller surface pore size of the TA-Fe coated substrate further eliminated the intrusion of polyamide into the substrate pores. The resulting membrane TFCn showed a water permeability of 19.6 ± 0.5 L m2– h–1 bar–1, which was an order of magnitude higher than that of control TFC membrane (2.2 ± 0.3 L m–2 h–1 bar–1). The formation of a more order polyamide rejection layer also significantly ...

Journal ArticleDOI
TL;DR: The synthesis of a crystalline TFP-DHF 2D COF membrane constructed from two precursors of 1,3,5-triformylphloroglucinol (TFP) and 9,9-dihexylfluorene-2,7-diamine (DHF) through the Langmuir-Blodgett (LB) method is reported, for the first timed.
Abstract: Two-dimensional (2D) covalent organic framework (COF) materials have the most suitable microstructure for membrane applications in order to achieve both high flux and high selectivity. Here, we report the synthesis of a crystalline TFP-DHF 2D COF membrane constructed from two precursors of 1,3,5-triformylphloroglucinol (TFP) and 9,9-dihexylfluorene-2,7-diamine (DHF) through the Langmuir–Blodgett (LB) method, for the first timed. A single COF layer is precisely four unit cells thick and can be transferred to different support surfaces layer by layer. The TFP-DHF 2D COF membrane supported on an anodic aluminum oxide (AAO) porous support displayed remarkable permeabilities for both polar and nonpolar organic solvents, which were approximately 100 times higher than that of the amorphous membranes prepared by the same procedure and similar to that for the best of the reported polymer membranes. The transport mechanism through the TFP-DHF 2D COF membrane was found to be a viscous flow coupled with a strong slip...

Journal ArticleDOI
TL;DR: This review summarizes the properties and applications of organic and inorganic materials, antifouling mechanisms, and surface modification of pre-formed membranes.
Abstract: Membrane fouling, which arises from the nonspecific interaction between the membrane surface and foulants, significantly impedes the efficient application of membrane technology. Antifouling and antimicrobial materials are important classes of functional materials for the surface modification of reverse osmosis and nanofiltration membranes. Applications of various organic and inorganic materials having different characteristics such as size, surface charge, hydrophilicity, functionality and biocidal activity, provide protective/sacrificial layers to the membrane surface against different foulants and microorganisms. This review summarizes the properties and applications of organic and inorganic materials, antifouling mechanisms, and surface modification of pre-formed membranes. Materials such as zwitterionic polymers, neutral polymers, polyelectrolytes, amphiphilic polymers, quaternary ammonium polymers, biopolymers, hydrophilic polymers, polydopamine, inorganic salts, and nanomaterials have shown great potential in reducing foulant adhesion and/or proliferative microbial growth on membrane surfaces.

Journal ArticleDOI
TL;DR: In this review, recent advances in rapid and controllable deposition of mussels‐inspired coatings, dopamine‐assisted codeposition technology, and photoinitiated grafting directly on mussel‐ inspired coatings are presented.
Abstract: Mussel-inspired chemistry has attracted widespread interest in membrane science and technology. Demonstrating the rapid growth of this field over the past several years, substantial progress has been achieved in both mussel-inspired chemistry and membrane surface engineering based on mussel-inspired coatings. At this stage, it is valuable to summarize the most recent and distinctive developments, as well as to frame the challenges and opportunities remaining in this field. In this review, recent advances in rapid and controllable deposition of mussel-inspired coatings, dopamine-assisted codeposition technology, and photoinitiated grafting directly on mussel-inspired coatings are presented. Some of these technologies have not yet been employed directly in membrane science. Beyond discussing advances in conventional membrane processes, emerging applications of mussel-inspired coatings in membranes are discussed, including as a skin layer in nanofiltra-tion, interlayer in metal-organic framework based membranes, hydrophilic layer in Janus membranes, and protective layer in catalytic membranes. Finally, some critical unsolved challenges are raised in this field and some potential pathways are proposed to address them.

Journal ArticleDOI
TL;DR: Microporous conjugated-polymer membranes have now been fabricated through surface-initiated polymerization and are capable of ultrafast organic-solvent nanofiltration because of the high porosity and pore interconnectivity originating from the rigid skeleton.
Abstract: Conventional technology for the purification of organic solvents requires massive energy consumption, and to reduce such expending calls for efficient filtration membranes capable of high retention of large molecular solutes and high permeance for solvents. Herein, we report a surface-initiated polymerization strategy through C–C coupling reactions for preparing conjugated microporous polymer (CMP) membranes. The backbone of the membranes consists of all-rigid conjugated systems and shows high resistance to organic solvents. We show that 42-nm-thick CMP membranes supported on polyacrylonitrile substrates provide excellent retention of solutes and broad-spectrum nanofiltration in both non-polar hexane and polar methanol, the permeance for which reaches 32 and 22 l m−2 h−1 bar−1, respectively. Both experiments and simulations suggest that the performance of CMP membranes originates from substantially open and interconnected voids formed in the highly rigid networks. Membranes with high selectivity and high permeance that allows rapid passage of solvent molecules are desirable for efficient separation processes. Microporous conjugated-polymer membranes have now been fabricated through surface-initiated polymerization. These membranes are capable of ultrafast organic-solvent nanofiltration because of the high porosity and pore interconnectivity originating from the rigid skeleton.

Journal ArticleDOI
TL;DR: In this article, Fe(III) and Zr(IV) based metal-organic frameworks (MOFs) were enmeshed in polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) electro-spun nanofibers to produce NMOMs.
Abstract: Fe(III) and Zr(IV) based metal–organic frameworks (MOFs) were enmeshed in polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) electro-spun nanofibers to produce nanofibrous MOF membranes (NMOM) The pristine MOFs showed high adsorption capacity for lead ions and mercury ions from aqueous solution The Fe(III) based MOFs with PAN based NMOM exhibited a high flux of 348 L m−2 h−1 with a permeance of 870 L m−1 h−1 bar−1 At room temperature, the NMOM could treat 395 mL of 100 ppb Pb(II) solution, while maintaining a drinking water standard of <10 ppb of permeate Pb(II) concentration Due to the high compatibility between MOF and PVDF nanofibers, MOF was not detected in the permeate even after four cycles of filtration and desorption experiments and more than 90% of the NMM adsorption capacity was retained The excellent filtration performance and re-generability of the membrane coupled with the hydro-stability of the MOFs suggests that the NMOMs have potential for water treatment through the process of membrane adsorption

Journal ArticleDOI
TL;DR: In this paper, the authors present compelling evidence that these nanovoids are formed by nanosized gas bubbles generated during the interfacial polymerization process, and different strategies were used to enhance or eliminate these nanobubbles in the thin polyamide film layer to tune its morphology and separation properties.
Abstract: Recent studies have documented the existence of discrete voids in the thin polyamide selective layer of composite reverse osmosis membranes. Here we present compelling evidence that these nanovoids are formed by nanosized gas bubbles generated during the interfacial polymerization process. Different strategies were used to enhance or eliminate these nanobubbles in the thin polyamide film layer to tune its morphology and separation properties. Nanobubbles can endow the membrane with a foamed structure within the polyamide rejection layer that is approximately 100 nm in thickness. Simple nanofoaming methods, such as bicarbonate addition and ultrasound application, can result in a remarkable improvement in both membrane water permeability and salt rejection, thus overcoming the long-standing permeability–selectivity trade-off of desalination membranes.

Journal ArticleDOI
TL;DR: In this article, a facile but effective approach to improve the photothermal performance by combining 2D reduced graphene oxide (rGO) and 1D multi-walled carbon nanotubes (MWCNTs), which have different nanomorphologies.
Abstract: Solar-driven water evaporation assisted by photothermal membranes is considered as one of the sustainable and cost-effective strategies for pure water generation and wastewater treatment. Herein, we report a facile but effective approach to improve the photothermal performance by combining 2D reduced graphene oxide (rGO) and 1D multi-walled carbon nanotubes (MWCNTs), which have different nanomorphologies. The photothermal layer can be easily deposited on different substrate materials via simple vacuum assistance. Such a composite photothermal layer shows a rough surface with a controllable nano-structure, which can thus optimize solar light harvesting. On the other hand, the formation of a loose internal porous structure and suitable wettability ensure water transport inside the photothermal layer during evaporation. The surface temperature reaches as high as 78 °C even under one sun irradiation (1 kW m−2), which is 10 °C higher than the result of pure rGO membranes. When loaded on a PVDF substrate, the rGO–MWCNT based membrane is flexible and shows an obvious improvement in the evaporation rate, about 79.0% and 8.9% higher than those of pure rGO and MWCNT membranes, respectively. The solar thermal conversion efficiency can reach up to 80.4% without any extra accessory for thermal management. Based on our results, the nanocomposite strategy is facile and effective for the development of novel photothermal membranes for high-efficiency evaporation, and contributes to the widespread application in the fields of desalination and wastewater treatment.

Journal ArticleDOI
TL;DR: An amino functionalized boron nitride (FBN) based filtration membrane with a nanochannel network for molecular separation and permeation and shows high transport performance for solvents depending on the membranes’ thickness is reported.
Abstract: Pressure-driven, superfast organic solvent filtration membranes have significant practical applications. An excellent filtration membrane should exhibit high selectivity and permeation in aqueous and organic solvents to meet increasing industrial demand. Here, we report an amino functionalized boron nitride (FBN) based filtration membrane with a nanochannel network for molecular separation and permeation. This membrane is highly stable in water and in several organic solvents and shows high transport performance for solvents depending on the membranes' thickness. In addition, the FBN membrane is applicable for solute screening in water as well as in organic solvents. More importantly, the FBN membranes are very stable in acidic, alkaline and oxidative media for up to one month. The fast-flow rate and good separation performance of the FBN membranes can be attributed to their stable networks of nanochannels and thin laminar structure, which provide the membranes with beneficial properties for practical separation and purification processes.

Journal ArticleDOI
TL;DR: In this paper, the authors highlight various properties of graphene and its derivatives that are essential for improving salt rejection, flux, and antifouling, and highlight a great deal of experimental research is essential to develop efficient graphene membrane-based desalination methods for practical use.