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Freeze casting liquid dispersions of solid particles is an effective method for preparing porous composites, thus creating strong and lightweight materials with “designed” microstructures for various applications. This work illuminates that tert-butyl alcohol (TBA)/water (H 2 O) mutually miscible system can be used as template to prepare aligned porous silicate cement supports with unique pore structures via directional freezing. The resulting pore morphology of porous cement substrates changes from prismatic to needle-like, dendritic, coralline, graininess and lamellar structure with the increasing of TBA-H 2 O ratio in cement slurry. Pore size distributions (macropores and mesopores) demonstrate the hierarchical pore structure of porous cement. The BET surface area ( S BET ) of porous cement support increases with the decreasing TBA content in cement slurry, until the pore forming agent was pure water. Porous cement that are fabricated from mixed slurries with relatively high TBA-H 2 O ratio show better mechanical strength. Porous cement support prepared from cement slurry with 90 wt% TBA exhibits the best permeation performance due to its well-distributed and oriented pore structure. These findings demonstrate how an aligned and hierarchical porous inorganic support with desirable properties can be prepared, under mild conditions, with the combination of advanced casting technique and most ancient construction material on earth. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) membranes have been developed by stacking the nanosheets together for using as molecular sieve due to its two-dimensional (2D) capillaries. However, this technology is still far from being ready for large-scale production. Specifically, pure GO membranes exhibit poor resistance to cross-flow process, and the commonly used preparation techniques pose scale-up difficulties. Here, we report a durable membrane developed using dip-coating polydopamine (PDA), followed by spray-coating multi-layered GO (MLGO). The fast preparation speed of ~0.2 s cm−2 and large preparation area of 1400 cm2 per preparing cycle demonstrated the scalability of the method. Acting as a binder and stabilizer, PDA developed MLGO-substrate interaction and crosslinked the MLGO sheets. The modified oriented MLGO layer contributed up to 95.0% retention of Na 2 SO 4 and showed enhanced stability in a 263-days soaking test and a nearly 800-h cross-flow test with the test area of 29.2 cm2. This work expands the possibilities for the GO membranes in practical applications. [Display omitted] • Multi-layered graphene oxide membrane was obtained by a fast and scalable method. • Modified MLGO membrane showed 95% retention of Na 2 SO 4. • Modified MLGO membrane exhibited high performance stability in long-term tests. [ABSTRACT FROM AUTHOR]

In this study, a facile and novel strategy for constructing tunable antimicrobial NF membrane surface was developed by a simple electrostatic assembly of polycation–copper(II) complex on the polyacrylonitrile substrate surface followed by cross-linking. Polycation–copper(II) complex with high stability and charge density, using polyethyleneimine (PEI) as a capping ligand, was formed by exquisitely manipulating the pH and Cu 2+ concentration for strong assembly on the surface. We confirmed that PEI–copper(II) complex assembly was a good way to significantly improve the Cu 2+ loading efficiency in terms of loading time and loading amount with AAS and EDS measurements. We also demonstrated that cross-linking had a significant influence not only on the strong assembly of PEI–Cu(II) complex to the substrate surface but also on the controllable Cu 2+ release, which was confirmed by SEM, EDS and AAS measurements after exposing the NF membrane to bath sonication and real seawater. The NF membrane exhibited significant antimicrobial activity with antibacterial efficiency of more than 95% and prevented effectively the formation of biofilms for up to 6-month test. For real seawater softening, the NF membrane achieved approximately 32.3 L/m 2 h flux and 43.5%, 68.3%, 98.1%, 19.1% and 18.7% rejection of salt, SO 4 2− , Mg 2+ , Na + and Cl − , respectively, with a high softening efficiency (low S value) compared to other commercial NF membranes. We hope that the present method can be developed as a competitive technology for the fabrication of robust and versatile antimicrobial membrane, leading to the high efficiency of seawater softening. [ABSTRACT FROM AUTHOR]

The cosolvent-assisted interfacial polymerization (CAIP) has garnered significant attention due to its capacity to easily and effectively modify the performance of polyamide (PA) reverse osmosis (RO) membranes. To gain deeper understanding of the mechanism of a specific type of cosolvents on the IP reaction, namely N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N,N-dimethylpropionamide (DMPr) were used as aqueous-phase cosolvents to systematically investigate their effects on the membrane structures and properties under different conditions. Amide cosolvents in the aqueous phase facilitated the diffusion of the amine monomer and the formation of nanovoids within the PA layer as the C-chain length of amides increased. When 1,2-dichloroethane was also included in the organic phase, the extent of the two-phase miscible zone was further increased with its assistance, which contributed to generating the larger nanovoids within the layer, thicker PA layer and extensive exterior PA layers, as well as significantly enhancing the water permeability and selectivity of membranes. Importantly, this study successfully prepared high-performance RO membranes with multilayer nanovoid structures in situ by introducing cosolvents in the IP reaction with permeability up to 2.26 L·m−2·h−1·bar−1, providing theoretical and experimental bases for further enrichment of CAIP. [Display omitted] • Exploring the effects of different amides on the diffusion of amine monomers. • Longer chain DMPr contributes to the formation of multilayered nanovoid structures. • Correlating amine monomer diffusion rate with PA layer evolution. • TFC a-o -DMPr shows water permeability of 2.26 LMH/bar and NaCl rejection of 98.38 %. [ABSTRACT FROM AUTHOR]

The robust correlation between the performance of thin-film composite (TFC) reverse osmosis membranes and the polyamide (PA) active layer determines the necessity of precise design of the PA layer, and this regulation primarily involves the surface morphology and internal characteristics of the PA layer. In this study, we fabricated honeycomb Turing structure or nanovoid-rich TFC series membranes using polar/nonpolar organic phase additives. Characterization and simulation results confirmed that the enhancement of membrane performance relied more on the abundant nanovoids within the PA layer rather than the ordered honeycomb lattice surface. Notably, the TFC-nDCE membrane with multilayer nanovoids exhibited an approximately 89 % improvement in water permeability while maintaining satisfactory salt rejection (98.29 %). We emphasized the significant role of nanovoids in the diffusion process of amine monomers and investigated the potential relationship between nanovoids and the degree of surface cross-linking. Building upon this, a new insight into the formation of nanovoids induced by PA anisotropic growth was presented through a careful analysis of the amine monomer diffusion rate and the morphological evolution of nanovoids. The structure-property relationship between internal structures, surface morphologies, and performances was systematically and thoroughly investigated, pointing out the direction for the rational design of TFC membranes. [Display omitted] • Revealed effects of nanovoids on the water/salt flow in honeycomb Turing PA layer. • Impacts of nanovoids on the physicochemical structure of PA layer were emphasized. • New insights on the anisotropic growth of PA were provided. [ABSTRACT FROM AUTHOR]

Embedding nanomaterials in thin film composite membranes to overcome the dynamic balance between salt rejection and permeability has become a research hotspot. Apparently, the filling positions of nanomaterials in membranes have a significant influence on membrane properties. In this work, GO@CS core-shell nanomaterials was firstly successfully synthesized, with good hydrophilicity and fast water transmission channels. Then the influences of addition amounts and loading positions of GO@CS on membrane performance were explored. Results demonstrated that embedding GO@CS with 0.01 wt% in the polyamide layer could give full play to the advantages of core-shell nanomaterials and improve the water flux and salt rejection (water flux increased by 115%, salt rejection increased to 99.10%), as well as the performance stability. Compared with TFN membrane with GO@CS embedded between the polyamide layer and supporting layer, the TFN membrane with GO@CS embedded in the polyamide layer could make full use of advantages provided by GO@CS that fast water transmission channels and the interlayer spacing assisting in salt rejection. This work provided guidances for the effect of nanomaterials with hierarchical pores embedding position on membrane performance. Image 1 • GO@CS core-shell nanomaterials were synthesized. • TFN membranes with different loading positions of GO@CS were prepared. • TFN-M membranes showed higher water flux and NaCl rejection. [ABSTRACT FROM AUTHOR]

Thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane with improved separation performance was fabricated via interfacial polymerization reaction between amine-functionalized graphene quantum dots (af-GQDs) doped aqueous monomer solution of m -phenylenediamine (MPD) and n -hexane solution containing trimesoyl chloride (TMC) monomer. We emphasize the employment of extra-low content for both af-GQDs and MPD, so that we could maximize the function of these nanomaterials and eliminate their aggregation at the same time. The af-GQDs nanomaterials could regulate the interfacial polymerization process and could be strongly anchored in the polyamide film via covalent bonding, hence could prevent their loss while providing more channels for faster solvent penetration. As a result, the optimized OSN membrane, TFN-50, shows a super-smooth surface, with a surface roughness as low as 4.3 ± 0.2 nm, and excellent pure solvent permeances which reach 135.8, 112.7, and 69.8 L m−2 h−1 MPa−1 for methanol, DMF and ethanol, respectively, as well as a very high Rhodamine B (RDB, 479 Da) rejection of up to 99.2%, and an ethanol permeance of 61.4 L m−2 h−1 MPa−1. Furthermore, the TFN-50 OSN membrane still shows excellent filtration performance after being submerged in DMF for 336 h or continuous crossflow filtration with Rose bengal (RB, 1017 Da)/DMF solution for 136 h, demonstrating its excellent solvent resistance. [Display omitted] • TFN OSN membrane incorporated with af-GQDs nanomaterials is prepared via interfacial polymerization method. • Ultra-low content for af-GQDs and MPD is used in the aqueous phase during the interfacial polymerization process. • Af-GQDs effectively manipulate the interfacial polymerization process and help to form a selectivity layer with ultra-smooth surface. • Higher solvent permeance and excellent dye rejection performance are achieved with the aid of af-GQDs. • The af-GQDs doped OSN membrane has excellent durability performance in harsh strong polar solvents. [ABSTRACT FROM AUTHOR]

In this study, a kind of thin film composite (TFC) membrane with two-dimensional (2D) covalent organic frameworks (COFs) as interlayer, termed as iTFC, which has integrally covalent bonding structure, ultra-thin and ultra-smooth surface, as well as high separation performance was fabricated via interfacial polymerization (IP) and subsequent chemical cross-linking and solvent activation for organic solvent nanofiltration (OSN). The COFs interlayer was in situ constructed using 1,3,5-triformylphloroglucinol (Tp) and hydrazine (Hz) on polyimide (PI) substrate prior to the IP. The optimization of the membrane fabrication process shows that very low concentration for both the COFs aqueous monomer Hz and the IP aqueous monomer m-phenylenediamine (MPD) was conducive to the formation of very smooth (roughness of 2.4 nm), very thin and defect-free cortex, thus improving the organic solvent permeation while remaining the dye rejection. Under optimal conditions, the prepared iTFC OSN membrane has an ethanol permeance of 63.4 L m−2 h−1 MPa−1, a Rhodamine B (RDB) rejection of greater than 99 %, and a molecular weight cut-off (MWCO) of as low as 380 Da. In addition, after filtration of 100 mg L−1 RB/DMF solution for 408 h, the optimized iTFC OSN membrane remained Rose Bengal (RB) rejection above 97 %, which proves its excellent solvent resistance performance. [Display omitted] • Ultra-low content Tp and Hz monomers are used for in situ construction of ultra-thin TpHz COFs interlayer. • Ultra-low content MPD, TMC monomer are used during the interfacial polymerization process. • Integrally covalent bonding forms between the adjacent layers of substrate, COFs interlayer and skin layer. • The iTFC OSN membrane achieves a much higher ethanol permeance of 63 L m−2 h−1 MPa−1 and 99 % high RDB rejection. • The integrally covalent bonding TFN OSN membrane achieves superior solvent resistance. [ABSTRACT FROM AUTHOR]

The separation performance of current organic solvent nanofiltration (OSN) membranes are still not satisfied. In this work, an ultra-thin TpHz covalent organic frameworks (COFs) interlayer was in situ constructed in advance on polyimide substrate, then an ultra-thin polyamide separation layer incorporated with amino-functionalized graphene quantum dots (af-GQDs) was constructed via interfacial polymerization (IP). A high performance interlayered thin-film nanocomposite (iTFN) OSN membrane with integrally covalent bonding structure, ultra-thin and ultra-smooth surface was obtained after post crosslinking and activation. The effect of ultra-low concentrations for the polyamide reaction monomers, the COFs monomer Tp and the doped af-GQDs nanoparticle reveals that they could help to form a very thin (7–8 nm in thickness) and defect-free skin layer with very smooth surface (about 2.7 nm in roughness). The iTFN OSN membrane shows excellent solvent permeance and solute selectivity, with an ethanol permeance reaching 97.6 L m−2 h−1 MPa−1 and an RDB rejection higher than 99%. After a 180 h long-term filtration with 100 mg L−1 RB/DMF solution, it remained an RB rejection of higher than 99%, demonstrating its superior resistance to strong polar solvent. Our work paves a unique way for the fabrication of novel OSN membrane with both in situ constructed nanomaterials interlayer and nanomaterials incorporated in skin layer. [Display omitted] • Integrally covalent iTFN OSN membrane has COFs interlayer and af-GQDs incorporated. • Ultra-thin TpHz COFs layer constructed in situ with ultra-low content of Tp and Hz. • Ultra-thin polyamide skin formed using ultra-low content for MPD, TMC and af-GQDs. • Ethanol permeance reaches 97.6 L m−2 h−1 MPa−1 with RDB rejection of above 99%. • The integrally covalent iTFN OSN membrane achieves superior solvent resistance. [ABSTRACT FROM AUTHOR]

Aiming at enhancing the permeability of reverse osmosis (RO) membranes, polyaniline-co-polypyrrole hollow mesoporous nanospheres (PPHMNs) were synthesized with aniline and pyrrole monomers via a simple and rapid one-step method, and then added to the aqueous phase of interfacial polymerization to fabricate thin-film nanocomposite (TFN) membranes. Hollow cores of the PPHMNs embedded in polyamide layers could reduce the interior transfer resistance of the membrane and shorten the transmission pathway of water molecules. Mesoporous shell of PPHMNs provided more channels for rapid transmission of water molecules. Moreover, amino groups in PPHMNs originated from the monomer of aniline could not only be bonded to polyamide (PA) layer by reacting with acyl chloride groups to prevent the leakage but also improve hydrophilicity of the membrane. Water flux of TFN membrane doped with PPHMNs (TFN-Ps) of 0.005 wt% addition concentration was 34.1 L·m−2·h−1 which is 76.7% higher than that of thin-film composite (TFC) membrane, and the NaCl rejection all kept over 99.0%. The TFN-Ps also showed excellent long-term stability, chlorine resistance and anti-fouling performance. This work opens an avenue for application of mesoporous hollow nanospheres with amino groups synthesized by simple and time-saving methods in developing TFN membranes with improved water flux. [Display omitted] • Mesoporous hollow nanosphere with amino groups was synthesized via a one-step method. • Nanospheres have uniform sizes of 130 nm and spherical shell ranges from 21 to 35 nm. • Water flux of RO membranes raised from 19.3 to 34.1 LMH with NaCl rejection over 99%. • TFN membrane showed long-term stability, chlorine-resistant and antifouling property. [ABSTRACT FROM AUTHOR]

A novel nanofiltration (NF) membrane is developed via polyethyleneimine (PEI) deposition on a hydrolyzed polyacrylonitrile (PAN) substrate enhanced by an electric field and chemical cross-linking to achieve improved desalting properties. Compared to the PEI static-deposition process, dramatic increase in salt rejection and substantial reductions of deposition time and PEI concentration are achieved for the membranes prepared by electro-deposition. What's more, the resulting membrane exhibited both stable flux and salt rejection in filtrating seawater for a relatively long term due to a significant membrane stability attributed to the electro-deposition. Desalting properties in terms of salt rejection and flux were found to be strongly affected by both hydrolysis and electro-deposition conditions. Under the optimal fabricating conditions, the resulting NF membrane exhibited a high flux of 24 L/m 2 h, excellent MgCl 2 rejection of ∼92% and low NaCl rejection of ∼39% when filtrating 2000 mg/L salt solution at 0.5 MPa. Under filtration of raw seawater at 1.8 MPa, the resulting membrane exhibited a high flux of 30.2 L/m 2 h and a significant improvement in seawater softening efficiency compared to various commercial NF membranes, which is attributed to its excellent separation efficiency between divalent and univalent ions. The current investigation demonstrated that polyelectrolyte NF membranes fabricated by electro-deposition and cross-linking led to excellent separation performance and satisfactory stability and durability that can be used in seawater softening for a relatively long time. [ABSTRACT FROM AUTHOR]

We successfully fabricated a kind of novel sandwich-like thin-film nanocomposite (TFN) polyamide (PA) membranes via interfacial polymerization (IP) method on polyimide (PI) support surface which was modified by a layer of nanosized amine-modified zeolitic imidazolate framework - 8 (mZIF-8) nanoparticles for organic solvent nanofiltration (OSN). Uniform distribution of the nanoparticles was obtained via directly immersing the PI support membrane in aqueous mZIF-8 suspension prior to the IP. A post-IP cross-linking procedure was conducted to enhance further the solvent resistance of the fabricated TFN OSN membranes. Ultra-smooth (average surface roughness of 13.7 nm) and ultra-thin (average thickness of about 33 nm) skin layer was achieved, together with high Rhodamine B (RDB, 479 Da) rejection (99.1%) and reasonable ethanol permeance (~28 L m−2 h−1 MPa−1), as well as nearly unchanged RDB rejection after being submerged in DMF at high temperature (80 °C) for 120 h, indicating their very good resistance in very harsh strong polar solvent circumstance and the promising aspect of their industrial application. • The OSN membrane was fabricated with covalent bonding between layers. • The mZIF-8 interlayer helped to form an ultra-smooth and ultra-thin skin layer. • OSN membrane permeance was effectively increased without sacrificing rejection. • The OSN membrane kept super stability in DMF at 80 °C for 120 h. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have emerged as promising candidate for the construction of advanced separation membranes due to their well-defined pore structure and highly ordered porous channels. Nevertheless, the implementation of high-efficient COFs-incorporated membranes still suffers from harsh synthetic conditions and possible agglomeration of COFs. Herein, a kind of sandwich-like thin film composite reverse osmosis (RO) membranes was fabricated to overcome such challenges via interfacial assembly of a COFs interlayer on polysulfone substrate, then followed by the formation of a polyamide skin layer via traditional interfacial polymerization (IP) process. The COFs interlayer not only tailored the pore structure and interfacial properties of the substrate, but also manipulated the uptake and release of the amine monomer during the IP process, which would contribute to forming a more ordered polyamide separation layer. The resultant COFs-interlayered RO membrane exhibited a nearly 33.8% higher water permeance (16.78 L m−2 h−1 MPa−1) along with a slightly increased NaCl rejection (99.2%) compared with the pristine RO membrane. More importantly, the emerging RO membrane presented a superior chemical (critic acid and NaOH) resistance and desirable long-term filtration stability, which paved a new pathway to construct high-performance RO membranes for desalination. Image 1 • The RO membranes were prepared on interfacial assembled COFs interlayer. • COFs interlayer optimized physicochemical and interfacial properties of substrate. • The COFs-modulated IP procedure enabled a thinner, denser and smoother PA layer. • The PA/COFs/PSf membrane enhanced the optimal water permeance by up to 33.8%. • The COFs-interlayered RO membrane exhibited a satisfying long-term stability. [ABSTRACT FROM AUTHOR]

This study describes the preparation and characterisation of MIL-53(Fe) and its effect on the performance of forward osmosis (FO) membranes. The cellulose acetate (CA)/MIL-53(Fe) hybrid membranes were fabricated using the method of phase inversion by dispersing MIL-53(Fe) in a CA casting solution. To improve the selectivity and permeability performance of FO membranes, the effects of MIL-53(Fe) content, casting solution temperature, coagulation bath temperature, and annealing temperature were studied. Results from scanning electron microscopy, membrane porosity, atomic force microscopy, and water contact angle tests of all the membranes show that the structural properties of the CA/MIL-53(Fe) hybrid membranes were optimised. The results of the FO performance tests, including the values of water flux and reverse salt flux, indicate improvement in the selectivity and permeability properties of the CA/MIL-53(Fe) hybrid membranes. Under the conditions of deionised water as the feed solution and 1 M NaCl solution as the draw solution, the water flux and reverse salt flux of the CA/MIL-53(Fe) hybrid membranes reached 34.9 L/(m2·h) and 2.02 g/(m2·h), respectively, in comparison with CA membranes. This study demonstrates that MIL-53(Fe) can improve the desalination performance and structural properties of FO membranes. • MIL-53(Fe) with high porosity was used to fabricate cellulose acetate (CA)/MIL-53(Fe) hybrid membranes for the first time. • Optimal experimental conditions of CA/MIL-53(Fe) hybrid membranes were conducted. • The water flux and reverse salt flux of CA/MIL-53(Fe) hybrid membranes were improved compared to CA membranes. • Effect of MIL-53(Fe) on structural properties of CA membranes was widely discussed. [ABSTRACT FROM AUTHOR]

Solvent resistant nanofiltration (SRNF) membranes are highly demanded in processing organic solutions especially those contain large molecules with molecular weight between 200 to 2000 Da, yet they have some drawbacks such as relatively poor solvent resistance and low solvent permeance. The current work presented an innovative class of amino-functionalized graphene quantum dots (aGQDs) embedded thin film nanocomposites (TFN) for SRNF membranes which were prepared via interfacial polymerization (IP) and subsequent steps (chemical imidization, crosslinking, and solvent activation). The prepared membranes enabled covalent interactions not only between the IP skin layer and the substrate, but also between the IP layer and the embedded aGQDs. The ethanol permeance and surface porosity increased by 44% and 69%, respectively, with the embedment of aGQDs under the optimal conditions, while the Rhodamine B (RDB, 479 Da) rejection maintained essentially stable above 99%. Furthermore, our novel membranes exhibited excellent long-term stability, with a rejection of over 99% for Rose Bengal (RB, 1017 Da) during the continuous filtration of 100 mg L−1 RB/ N , N -dimethyl formamide (DMF) solution at room temperature for more than 768 h. They also exhibited good organic solvent resistance and high-temperature tolerance in both DMF and NMP solvents, with a RDB rejection of over 99% and an ethanol permeance of about 38 L m−2 h−1 MPa−1 after being immersed in DMF at 80 oC for 248 h, and a RDB rejection of over 99% and an ethanol permeance of about 41 L m−2 h−1 MPa−1 after being immersed in NMP at 80 oC for 232 h. The results demonstrated that the aGQDs-embedded TFN OSN membrane has vast potential in SRNF applications. Image 1 • (PI-aGQDs/PI) XA membrane was prepared via IP, imidization, crosslinking, activation. • The (PI-aGQDs/PI) XA SRNF membrane owns a wholly covalent bonding chemical structure. • aGQDs improve greatly the surface morphology and performance of the SRNF membrane. • The SRNF membranes kept >99% RB rejection in filtration of DMF at 25 oC for 30 days. • The SRNF membranes kept good solvent resistance in DMF and NMP at 80 oC for 10 days. [ABSTRACT FROM AUTHOR]