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Experimental data, along with theoretical modelling, are combined to explore the potential for the separation of an azeotropic polar/non-polar solvent mixture through an OSN membrane. A mixture of toluene/butanol was used for the model development, and then applied to toluene/ethanol, and toluene/heptane mixtures. Experimental data was obtained at various testing conditions to validate simulation results from a non-ideal solution diffusion transport model incorporating the Flory–Huggins ternary equations. Accounting for the effects of non-ideality in the feed and permeate solutions generated a better fit to the experimental data. The system of equations was solved using parameters obtained from mono component membrane data only. The model developed can be used as a pre screening check for the separation of a potential solvent mixture that an OSN membrane can offer prior to embarking upon an extensive experimental program. • Siloxane membranes fabricated and applied to separation of azeotropic mixture of toluene/butanol. • Flory Huggins ternary equations integrated into solution diffusion model and solved to aid in understanding of membrane transport. • Separation performance went through distinct maximum, and appeared governed by non-ideality of the system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic solvent nanofiltration membranes are reviewed. • Discussed the role of functionalization and covalent crosslinking in membrane. • Covalent incorporation of organic, inorganic, and hybrid materials is described. • New OSN membranes incorporating 2D nanomaterials are discussed. • The challenges and prospects around OSN membranes are discussed. Organic solvent nanofiltration (OSN) membranes have gained significant attention owing to their pivotal role in various industrial applications, including pharmaceuticals, fine chemicals, and manufacturing. This review provides a comprehensive overview of the recent advances in OSN membrane technology, focusing on membrane materials, fabrication techniques, and strategies for tuning the chemistry, structure, and performance of OSN membranes. Initially, the fundamental principles underlying OSN are described, highlighting the critical parameters influencing membrane selectivity, permeability, and stability in organic solvents. It also focuses on the importance of covalent crosslinking in the design and fabrication of dense polyamide membranes. Subsequently, the design and synthesis of novel membrane materials are discussed, including polymeric, inorganic, and hybrid membranes. The use of 2D nanomaterials is summarized, with an emphasis on their structural characteristics and tailored properties for solvent separation applications. We further explored the innovative fabrication strategies, such as interfacial polymerization, modification of ultrafiltration supports, and tuning of the active layer chemistry by incorporating the membrane structure with porous nanofillers. This review also discusses the inhomogeneity issues between inorganic nanofillers and organic matrices of membranes as well as the strategies to overcome these limitations through proper functionalization. Finally, we identified emerging trends and prospects in OSN membrane research, encompassing sustainability, scalability, and integration with other membrane processes, to address existing challenges and discover new opportunities for efficient solvent separation in diverse industrial sectors. [ABSTRACT FROM AUTHOR]

Experimental data, along with theoretical modelling, are combined to explore the potential for the separation of an azeotropic polar/non-polar solvent mixture through an OSN membrane. A mixture of toluene/butanol was used for the model development, and then applied to toluene/ethanol, and toluene/heptane mixtures. Experimental data was obtained at various testing conditions to validate simulation results from a non-ideal solution diffusion transport model incorporating the Flory–Huggins ternary equations. Accounting for the effects of non-ideality in the feed and permeate solutions generated a better fit to the experimental data. The system of equations was solved using parameters obtained from mono component membrane data only. The model developed can be used as a pre screening check for the separation of a potential solvent mixture that an OSN membrane can offer prior to embarking upon an extensive experimental program. • Siloxane membranes fabricated and applied to separation of azeotropic mixture of toluene/butanol. • Flory Huggins ternary equations integrated into solution diffusion model and solved to aid in understanding of membrane transport. • Separation performance went through distinct maximum, and appeared governed by non-ideality of the system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic solvent nanofiltration membranes are reviewed. • Discussed the role of functionalization and covalent crosslinking in membrane. • Covalent incorporation of organic, inorganic, and hybrid materials is described. • New OSN membranes incorporating 2D nanomaterials are discussed. • The challenges and prospects around OSN membranes are discussed. Organic solvent nanofiltration (OSN) membranes have gained significant attention owing to their pivotal role in various industrial applications, including pharmaceuticals, fine chemicals, and manufacturing. This review provides a comprehensive overview of the recent advances in OSN membrane technology, focusing on membrane materials, fabrication techniques, and strategies for tuning the chemistry, structure, and performance of OSN membranes. Initially, the fundamental principles underlying OSN are described, highlighting the critical parameters influencing membrane selectivity, permeability, and stability in organic solvents. It also focuses on the importance of covalent crosslinking in the design and fabrication of dense polyamide membranes. Subsequently, the design and synthesis of novel membrane materials are discussed, including polymeric, inorganic, and hybrid membranes. The use of 2D nanomaterials is summarized, with an emphasis on their structural characteristics and tailored properties for solvent separation applications. We further explored the innovative fabrication strategies, such as interfacial polymerization, modification of ultrafiltration supports, and tuning of the active layer chemistry by incorporating the membrane structure with porous nanofillers. This review also discusses the inhomogeneity issues between inorganic nanofillers and organic matrices of membranes as well as the strategies to overcome these limitations through proper functionalization. Finally, we identified emerging trends and prospects in OSN membrane research, encompassing sustainability, scalability, and integration with other membrane processes, to address existing challenges and discover new opportunities for efficient solvent separation in diverse industrial sectors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of gel membrane by bridging TA to SA. • The double network enhanced the solvent resistance of the gel membrane. • Gel membrane had higher porosity and mechanical properties. • Gel membrane had high dye anti-fouling and self-cleaning ability. It is necessary to prepare a nanofiltration membrane with high permeation flux that can be used in the field of organic solvents. Gel membranes have a high solvent permeation flux, but their chained macromolecular structure is often unstable. In this study, tannic acid-bridged sodium alginate (TA x -Ca/FeSA) organic solvent nanofiltration (OSN) membranes were prepared by the phase transition method using aqueous Ca2+ and Fe3+ solutions as cross-linking agents. TA can interact with SA through hydrogen bonding hydrophobic bonding and other interactions to form an interpenetrating three-dimensional network structure. Compared with Ca/FeSA membrane, the average pore size of TA 0.125 -Ca/FeSA membrane was reduced from 1.03 nm to 0.74 nm, and the porosity was increased from 47.62 to 59.2 %. In addition, the TA 0.125 -Ca/FeSA membrane has the characteristics of a negative charge, super hydrophilicity, and high mechanical properties, exhibits a high permeation flux of 48.97 L·m−2·h−1·bar−1 with a rejection of 96.25 % for Congo red ethanol solution, has excellent solvent resistance, stain resistance, and self-cleaning ability. The TA 0.125 -Ca/FeSA membrane was demonstrated to have great potential for application in the fields of purification and solvent recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel nanocomposite MMM has been developed using CAU-10-H, PEI, and P84 co-polyimide. • Addition of CAU-10-H improved hydrophilicity and solvent permeance. • Crosslinking by PEI improved resistance to aggressive solvents. • The optimized membrane possesses good rejection and solvent permeance. • The CAU-10-H based OSN MMM exhibited good antifouling and long-term stability. The advancement of organic solvent nanofiltration (OSN) is often hindered by the inherent trade-off between permeance and rejection. In this study, we present a novel nanocomposite mixed matrix membrane (MMM) fabricated by integrating a compatible metal–organic framework (CAU-10-H) into a co-polyimide (P84) matrix. The resulting P84/CAU-10-H membrane was cross-linked using branched polyethyleneimine (PEI) to produce a P84/CAU-10-H/PEI MMM with robust resistance to harsh organic solvents, making it suitable for OSN applications. The integration of CAU-10-H, PEI, and P84 significantly enhanced the OSN performance, improving sieving efficiency and reducing fouling tendencies. The fabricated membrane exhibited outstanding permeance across various solvents, with values of 42.4, 45.4, 24.5, and 27.1 LMH/bar for methanol, acetone, N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO), respectively. Besides, the P84/CAU-10-H/PEI MMM demonstrated excellent rejection (Brilliant yellow (BY) > 90 %, Congo red (CR), Methyl blue (MB), Evans blue (EB), and Alcian blue (AB) > 99 %, respectively). In a 96-hour long-term test, the membrane demonstrated excellent stability and anti-fouling properties. This study presents a facile and viable approach for designing and constructing novel OSN MMMs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three new poly(ether-ether-ketone) copolymers with backbones having sulfonyl moieties were synthesized. • The monomer ratio for copolymerization varied between 0.25 and 0.75 for CH 3 and SO 2 containing monomers. • PEEK-based solvent-resistant membranes were prepared using TamiSolve via phase inversion and crosslinking. • Correlation between the copolymer composition, dope solution and membrane performance were established. • Molecular dynamics revealed the interactions between polymers and solvents. Poly(ether-ether-ketone) (PEEK) is an attractive material for membrane fabrication due to its exceptional thermal and chemical stability. However, traditional PEEK processing necessitates the use of harsh chemicals, such as sulfuric acid because of its limited solubility in organic solvents. To overcome this limitation, copolymers offer a solution by enhancing solubility and subsequently improving membrane characteristics such as permeability and selectivity. Herein, three novel copolymers – PEEK with various contents of SO 2 and CH 3 – were developed and used in membranes for the separation of polar and non-polar solvents. The chemical structure of the copolymers was tailored by varying the monomer ratio between 0.25 and 0.75 for CH 3 and SO 2 containing monomers. Diamine–crosslinked PEEK copolymer membranes were prepared using a green solvent (TamiSolve). The effects of the polymer structure, the dope solution rheology, and membrane properties together with separation performance were studied. The resulting membranes demonstrated a permeance for acetonitrile ranging from 7.4 to 8.2 L m−2 h−1 bar−1 with molecular weight cutoffs of 839–915 g mol−1. Molecular dynamic simulations were conducted to explore the interaction between the copolymers and nine different organic solvents. Our findings underscore the significance of copolymer design in achieving tailored membrane properties for diverse separations. [ABSTRACT FROM AUTHOR]

• 7,7′-OH-BINOL and diacyl chloride were used to prepare TFC OSN membranes. • The formed polyarylate layer show thin and high microporosity characters. • Two oil phase cross-linker result in nanofilms with diverse microstructures. • The optimal membrane shows methanol flux of 5.81 LMH/bar and MWCO of 288 Da. In recent years, OSN technology has gained great attention for its environmental friendly nature, energy efficiency, and small carbon footprint. Herein, we prepared TFC OSN membranes BINOL-TPC and BINOL-IPC with higher selectivity by employing a contorted molecule 7,7′-dihydroxy-2,2′-binaphthol (7,7′-OH-BINOL) with four functional groups and diacyl chloride (TPC/IPC) via interfacial polymerization (IP) method compared to with trimesoyl chloride (TMC). The use of monomer 7,7′-OH-BINOL with rigid, twisted and multiple reaction sites endow the resulted polyarylate layer with high microporosity and cross-linking density. Notably, the BINOL-TPC and BINOL-IPC membranes exhibited good performance in retaining small molecular solutes, with MWCO values of 288 and 344 Da, respectively. Meanwhile, the methanol permeance of the two composite membranes reach 5.81 and 7.06 LMH/bar, respectively. In addition, the membrane BINOL-TPC could achieve precise separation of mixed dyes with similar molecular weight but opposite charge. As can be seen, by designing and utilizing IP monomers with different structures and functionalities, it is possible to fabricate membranes with diverse microstructures and properties, ultimately leading to varied separation performances. This research offers some new insights in the view of molecular-level tailoring for the fabrication of high performance OSN membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface dynamics was utilized to generate a selective layer on ISA membranes. • The thermally treated polyimide ISA membranes evolved from UF to NF. • Relationships between the formed skin and the initial pore structure were studied. • The developed polyimide membranes were competitive in OSN. Integrally-skinned asymmetric (ISA) polymer membranes show enormous potential in efficiently energy-saving organic solvent nanofiltration (OSN) due to their excellent structural stability. However, the control of their microstructures at the nanoscale is technically challenging, making it difficult to simultaneously achieve high separation resolution and high solvent permeance. In this work, we report the in-situ evolution of polyimide ISA membranes from ultrafiltration to nanofiltration through thermal-induced densification of the surfaces. This process was attributed to the surface dynamics of polymers — i.e., the polymer segments on surface are more freely movable than that in bulk. The optimum treatment temperature was located between the glass transition temperatures of surface and bulk, which were measured based on porosity changes. The as-prepared ISA membranes with thin and dense skin layers exhibited high solvent permeance (e.g., over 5 L m−2 h−1 bar−1 for ethanol) and favorable molecular weight cut-off of around 300 Da. The membranes rivaled the state-of-the-art thin film composite membranes, demonstrating great potential in fast and precise molecular separation in OSN. [ABSTRACT FROM AUTHOR]

[Display omitted] • The nanoscale ordered "Turing-like" structure of PA/PPy composite membrane was achieved by PA interlayer assistance of CVD method. • PA/PPy composite membrane still showed excellent tolerant at high temperature (80 ℃) and organic solvent (DMAc). • The excellent stability was obtained due to hydrogen bond and electrostatic interaction between PA and PPy. • The membrane presented excellent permselectivity performances with MWCO as low as 185 Da. Organic solvent nanofiltration (OSN) is a green, energy-saving, and highly efficient emerging membrane separation technology, and there is an urgent need for robust, easy-to-process OSN membranes with high permeance and small solute selectivity for industrial applications. Herein, we propose a new strategy for accurately designing novel OSN membranes. Specifically, a polyamide (PA) interlayer was synthesized in-situ on the surface of homogeneous reinforced poly(p-phenylene terephthamide) (PPTA) hollow fiber membrane by interfacial polymerization (IP) using both ultra-low concentrations piperazine (PIP, 0.05 wt%) and trimesoyl chloride (TMC, 0.005 wt%), and then a defect-free and dense PPy layer was deposited on top of the hydrophilic PA interlayer by chemical vapor deposition (CVD) process to prepare PA/PPy composite membranes with spherical cluster or strip cluster "Turing-like" structure. The resulting PA/PPy composite membranes presented an excellent high selective permeability, the dimethylacetamide (DMAc) permeability was 21.1 L·m−2·h−1·MPa−1, and the molecular weight cut-off (MWCO) was as low as 185 Da. A 30-hour OSN test at elevated temperatures (80 °C) and in organic solvent (DMAc), as well as a one-month immersion test in ethanol and DMAc at room temperature, demonstrated superior separation performance and structural stability of the membranes, indicating their application potential in harsh solvent systems. Our novel method for developing nanoscale ordered structured PA/PPy composite membranes offers great potential for the development of multilevel structural designs in the preparation of high-performance OSN membranes with potential industrial applications. [ABSTRACT FROM AUTHOR]

SYNOPSIS. We develop a novel strategy to shelter the defects existed between the adjacent MOF nanosheets through the assembly of MOF nanosheets and NH 2 -SWCNTs. [Display omitted] • NH 2 -SWCNTs can shelter the defects between the adjacent CuBDC nanosheets. • The nanochannels created by NH 2 -SWCNTs facilitate the permeation of organic solvents. • Excellent rejections of dyes with superior methanol permeance is achieved. • Outstanding stability against high-concentration feeds is obtained. Organic solvent nanofiltration (OSN) has become increasingly important in petrochemical and pharmaceutical industries, demanding superior and robust membranes. 2D MOF nanosheets hold great promise in the preparation of OSN membrane. Nevertheless, the fabrication of defect-free 2D MOF membranes with robust mechanical strength is hampered due to the weak interlamellar interactions between MOF nanosheets. Herein, 2D MOF composite membrane for high-performance OSN application is fabricated through the assembly of copper 1,4-benzene dicarboxylate (CuBDC) nanosheets and NH 2 -SWCNTs. Within this composite configuration, NH 2 -SWCNTs can shelter the defects between the adjacent CuBDC nanosheets, rendering CuBDC/CNTs composite membranes precise molecular sieving ability. Meanwhile, the nanochannels created by NH 2 -SWCNTs with low frictional coefficients on the internal surface promote the permeation of organic solvents. Moreover, the multiple interactions between CuBDC and NH 2 -SWCNTs improve the mechanical strength of composite membranes. Accordingly, the composite membranes display excellent rejections of dye molecules on the basis of size-sieving mechanism with superior methanol permeance of 1260 L m−2h−1 bar−1, as well as steady congo red rejection at high trans -membrane pressure of 5 bar, demonstrating good pressure resistance of composite membranes. Moreover, the composite membranes exhibit outstanding stability against high-concentration feeds and long-term operation for 50 h, confirming excellent practicality in the purification of dyes from organic solvents. The design approach in this work may inspire the fabrication of other nanosheet-based membranes for high-efficient OSN. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phenolic resin (PR) OSN membrane with PVA fiber skeleton was fabricated. • The novel fabrication strategy was accomplished through electrospinning. • The space between PVA fiber with PR matrix provided additional channels for solvents. As an emerging separation technology, organic solvent nanofiltration (OSN) has shown great potential in the chemical, food, and pharmaceutical industries. Considering the excellent solvent resistance of phenolic resin (PR), it has great potential to be employed for the fabrication of OSN membrane. However, the extremely low permeance due to the highly cross-linked network and limited fabrication strategies still hold back the further application of PR. Herein, we develop a novel method to fabricate PR membrane with polyvinyl alcohol (PVA) fiber skeleton for OSN. This is accomplished through the electrospinning of PVA-resol solution, followed by heating to initiate the cross-linking of resol to form PR. After the further reaction with glutaraldehyde (GA), the PR OSN membrane is finally acquired. Benefiting from the homogeneous mixing of PVA with resol in the electrospinning solution, the formed PVA fibers are uniformly embedded in the PR matrix. The space between PVA fiber skeleton with PR matrix could provide additional channels for the transportation of solvent molecules. Compared with those membranes fabricated by traditional casting methods, the permeance of PR/PVA/GA reported here is significantly improved. The molecular weight cut-off (MWCO) of PR/PVA/GA is about 803 Da based on the rejection curve. Meanwhile, the permeance of acetonitrile about 1.3 Lm-2h-1bar−1 is the highest among the studied solvents, while the values are very low for nonpolar solvents, such as hexane and toluene. Additionally, the obtained membrane exhibits excellent anti-compaction ability and long-term stability. As an alternative to phase inversion and interfacial polymerization, the strategy reported here may provide a new way for the assembly of polymers into nanofiltration membranes for diverse separation applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simultaneous Cu2+ crosslinking of polyimide substrate and polyamide layer. • Integrally-crosslinked membrane has a superior solvent resistance and performance. • The integrally-crosslinked membrane has a defect-free layer. • Slower MPD diffusion from Cu2+ crosslinked substrate of partially-crosslinked one. Thin film composite (TFC) membranes are commonly used for organic solvent nanofiltration (OSN) application. However, these membranes normally suffer from the layer delamination under harsh conditions. Chemically integral crosslinking is a common method to address this problem, but the resultant tightened polymeric chains and denser microstructure will inevitably bring the reduced solvent permeance. In this work, a facile metal integral crosslinking strategy, which has minimal adverse effect on the solvent permeance, was developed to improve the tolerance to the majority of organic solvents as well as enhance the adhesions of upper selective layers and underlying substrates simultaneously for the first time. The as-developed Cu2+ integrally-crosslinked membranes demonstrated a high permeance for organic solvents and a high rejection towards rose bengal. In comparison to the Cu2+ partially-crosslinked membranes (with substrate crosslinked only), the integrally-crosslinked ones exhibited superior solvent resistance and OSN performance. This improvement was attributed to the enhanced interactions and a defect-free PA layer. Additionally, the effects of solvent activation, crosslinking solution concentration as well as crosslinking time were also studied. It is believed that metal integral crosslinking strategy will offer a novel approach to develop promising TFC membranes with satisfactory OSN performance for practical applications. [ABSTRACT FROM AUTHOR]

• Organic solvent NF membranes were prepared using 4,4′-diaminodiphenylmethane. • Hydrophobic-modified NF membrane had the optimal performance in THF. • The permeances of organic solvents are related to the specific solvent properties. A kind of thin film composite polyamide nanofiltration (NF) membrane was synthesized via the interfacial polymerization between a new diamine monomer of 4,4′-diaminodiphenylmethane and trimesoyl chloride on the surface of cross-linked polyetherimide, and evaluated in some organic solvents including ACN, MeOH, EtOH, THF, etc. The optimal organic solvent NF membrane was selected to prepare respectively the hydrophilic membrane (Phi-NF) via grafting of Tris and the hydrophobic membrane (Pho-NF) via grafting of 2,2,2-trifluoroethylamine, combining with the characterization of ATR-FTIR, XPS, SEM, 13C NMR, AFM, etc. The permeance values of Phi-NF and Pho-NF membranes change greatly with organic solvents. Pho-NF-2 possesses the highest permeance of 66.4 L m−2 h−1 MPa−1 in THF with the erythrosin B (EB) rejection of 99.5%. Through analyzing the physiochemical properties of the organic solvents and calculating the surface energy, the correlations are deduced for the synthesized membranes, illustrating that the permeances of organic solvents are roughly proportional to the specific solvent properties for Phi-NF-2 and Pho-NF-2. The results suggest one promising method to enhance the separation performance of organic solvent NF membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • We synthesized two poly(ether-ether-ketone) (PEEK) with backbones having –CH 3 and SO 2. • PEEK membranes were prepared using a conventional (NMP) and a green (TamiSolve) solvent. • They were used for pharmaceutical purification by organic solvent nanofiltration. • The SO 2 -containing PEEK exhibited considerably higher permeance than PEEKs with –CH 3. • The crosslinked membranes demonstrated superb organic solvent stability over six months. Through polymer engineering, the membrane properties can be considerably changed and its performance can be improved. Organic solvent nanofiltration (OSN) membranes require polymers with good solution processability to facilitate membrane preparation. However, the resultant membranes should have excellent solvent resistance. Poly(ether-ether-ketone) (PEEK) is a potential polymer for OSN applications because of its high thermal stability and excellent solvent resistance. However, commercial PEEK has limited solution processability, and its fabrication requires a harsh acidic environment. Herein, two customized PEEKs were synthesized by incorporating methyl (–CH 3) and sulfonyl (SO 2) groups into the polymer backbone. The membranes were prepared by phase inversion using N -methyl-2-pyrrolidone (NMP) and TamiSolve as a green alternative. The effects of the polymer structure, green solvent, and crosslinking on the membrane morphology, chemical and mechanical stability, as well as separation performance have been examined. The molecular interaction between organic solvents and PEEKs were investigated through molecular dynamic simulations and density functional theory. The molecular weight cutoff (MWCO) values of the membranes were 540–768 g mol−1, with a high corresponding permeance of 8.2–20 L m−2 h−1 bar−1 in acetone. The long-term stability of membranes was successfully demonstrated over two weeks through a continuous crossflow filtration using acetone under a pressure of 30 bar. The membranes demonstrated excellent active pharmaceutical ingredient purification through the removal a 2-methoxyethoxymethyl chloride (125 g mol−1) carcinogenic impurity from roxithromycin (837 g mol−1). [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) performance is influenced by several factors, including the solvent, membrane, transmembrane pressure, system size, flowrate, and desired end concentration. System design and optimization of such a complex process requires a unified framework so that the effect of each influence can be compared quantitatively in a single plot. To that effect, a mathematical framework was derived by functionally relating the target quantities (solute yield and solvent recovery) interconnected by the mass balances of each species. The plot obtained indicates solute–solvent selectivity, solute yield, solvent recovery, closeness to the saturation concentration, and a comparison of system sizes; hence when plotted for varied operating conditions and solvent–membrane systems, such a plot is instructive to improved system design. In the current paper, this framework is illustrated for OSN implemented for curcumin extract concentration. Two membranes (Evonik Puramem Performance, PMP, and Evonik Puramem Selective, PMS) were compared at various pressures on a single plot. The key output values obtained are solute yield, solvent recovery, system size comparison, and permeate bulk solute concentration. It was shown using the framework that when operated at 10 bar, the PMS membrane has a higher solute yield (180%); however, it requires a larger membrane area (25%) to reach saturation, compared to PMP. Finally, the effect of concentration polarization on the separation is demonstrated using the framework. [Display omitted] • Mathematical framework for system design in organic solvent nanofiltration (OSN). • Unified analysis of influencing factors in OSN, allowing easy system design. • Key system outputs are solute retentate and solvent permeate flow rates. • Characteristic plots show key system outputs at varied conditions in a single plot. • Case study of curcumin concentration from ethanol extract analyzed and optimized. [ABSTRACT FROM AUTHOR]

[Display omitted] • A thin film nanocomposite membrane with interlayered CCN nanosheets was synthesized. • The introduction of CCN nanosheets enhanced the permeance of the TFNi membrane. • A strong chemical bonding was formed between the CCN interlayer and the PA layer. • The CCN-TFNi membrane demonstrated robust anti-swelling ability when exposed to DMF. • The CCN-TFNi-DMF membrane showed exceptional permeability and remarkable stability. The integration of a nanomaterial interlayer within a thin-film composite membrane can markedly enhance its performance in organic solvent nanofiltration (OSN). However, this enhancement often comes at the expense of membrane integrity due to differential swelling behaviors in diverse solvents. In this study, we present an interlayered thin film nanocomposite (TFNi) membrane that demonstrates both high permeance and robust stability, utilizing green, porous, and reactive crystalline carbon nitride (CCN) nanosheets as the functional interlayer. The results revealed that ascribed to the presence of the CCN interlayer, the membranes retained their rejection towards organic dyes even after 10 h of DMF exposure, while the organic solvent permeance was significantly improved by the DMF treatment. The methanol permeance of the CCN-TFNi-DMF membrane reached an impressive 8.77 L m−2 h−1 bar−1, sustaining stable performance throughout a 72 h test period under a pressure of 10 bar. We attributed this performance enhancement to the extra nanochannels introduced by the CCN nanosheets that bolstered the permeance of the TFNi membrane, as well as the formation of a stable polyamide film resulting from the reaction between the amino groups on the CCN nanosheet surface and trimesoyl chloride during the interfacial polymerization process. This work provides valuable insights into the development of structurally reinforced TFNi membranes with exceptional performance for OSN separation applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Palladium-based homogeneous catalysts are indispensable in the pharmaceutical field due to the high reaction yields and high selectivity they can reach. However, they are toxic and sensitive to oxidation. Isolating these complexes from pharmaceutical molecules at the end of the synthesis without degrading both compounds could therefore lead to major environmental and economic gains. This study focuses on the separation between a real pharmaceutical intermediate at around 600 g mol−1 and a palladium catalyst PdCl 2 (PPh 3) 2 at 701.9 g mol−1 using ceramic membranes in organic solvent phase. For improving this separation, substitute catalysts with higher molecular weights and/or higher steric hindrances had been selected, and MWCO of 1000, 750, and 250 Da had been evaluated. The interest of catalyst enlargement had been confirmed with Pd retentions from 13 % (reference) to 18 % (heavier complex), but this approach was limited by economic aspect which restricted the choice of potential substitutes. Nanofiltration membranes with lower cut-off points have led to slightly higher retentions, but membrane characterization concluded that experimental MWCO were similar between all membranes, therefore raising questions about the definition of MWCO for different manufacturers. [ABSTRACT FROM AUTHOR]

[Display omitted] • TFC membranes with PEEK support and biphenyl polyamides active layer were fabricated for the first time. • Biphenyl polyamide nanofilms exhibited enhanced nano-mechanical strength, high solvent stability and regulated morphology. • The optimized membrane exhibited a high permeability for acetonitrile of 21.6 L m-2 h-1 bar-1. • MWCOs of the membranes can be customized between 170 to 370 g·mol−1 by employing appropriate biphenyl acyl chlorides. Developing polymeric separation membranes that combine excellent solvent stability, high permeability, and customizable molecular weight interception remains a challenge. Herein, thin-film composite (TFC) polyamide (PA) membranes with poly(ether ether ketone) (PEEK) support and biphenyl-centered polyamides active layer were fabricated through interfacial polymerization technique for the first time. Enhanced solvent stability was exhibited by the fabricated membranes due to the intrinsic resistance to organic solvents possessed by PEEK and biphenyl polyamides. The separation performance of the obtained membranes was systematically studied by relating to the properties of PA nanofilms in terms of nano-mechanical strength, morphologies, and microporosity. The organic solvent nanofiltration (OSN) performance of the resultant membranes in terms of permeability and molecular weight cut-off (MWCO) could be regulated. The optimized membrane exhibited a pure solvent permeability as high as 21.6 L m−2 h−1 bar−1 for acetonitrile and 14.0 L m−2 h−1 bar−1 for methanol. It also showed excellent long-term durability with almost unchanged permeability as well as solute retention remained above 97.8 % after a cumulative OSN operation of N, N -Dimethylformamide (DMF) based feed for 240 h. In particular, OSN membrane with targeted MWCOs covering the range of 170–370 g·mol−1 could be fabricated by selecting appropriate biphenyl acyl chlorides as building blocks. This approach offers a scalable and versatile platform for the development of solvent-stable, highly permeable, and customizable MWCO membranes for process-oriented OSN. [ABSTRACT FROM AUTHOR]

Thin-film nanocomposite (TFN) membranes have attracted growing interests for improving the energy efficiency of many chemical separation processes, while well-designed microstructures are essential to acquire high permeation flux, high selectivity and high stability for different types of permeates. Herein, a novel strategy to regulate the microstructures and solvent permeation properties of TFN membranes is developed. Hydrophobic polysiloxane domains are proposed to be evenly distributed within hydrophilic polyamide matrix with the mediation of polydopamine nanoparticles (PDNPs). To be specific, PDNPs treated by 3-(triethoxysilyl)- propylamine (APTES) allow PDMS converge on its surface, so as to form nano-sized poly(dimethylsiloxane) (PDMS) domains within the active layer of TFN membranes. With polyethyleneimine (PEI) as the aqueous phase monomer during conventional interfacial polymerization (IP), trimesoyl chloride not only acts as the oil phase monomer, but also reacts with the terminal hydroxyl groups of PDMS, facilitating the uniform dispersion of the nanoparticles within the PEI matrix. By tuning the ratio of PDNPs to PDMS, PDMS could be uniformly dispersed within the active layer together with PDNPs, which effectively construct hydrophobic pathways for nonpolar solvents. A maximum permeate flux for n -heptane of 7.9 L m −2 h −1  bar −1 at 10 bar is achieved, along with moderate area swelling (3.16%) and rather low MWCOs (below 400). Meanwhile, these TFN membranes containing PDMS domains still display appropriate permeate fluxes for polar solvents due to the maintenance of hydrophilic pathways, as well as enhanced rejection ability and potential long-term operation stability than the control membranes. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) has been widely explored as a promising membrane material, but the trade-off between porosity and stability limits its widespread application in organic solvent nanofiltration (OSN). Here we present a simple approach to prepare PANI membranes with excellent chemical stability and rejection performance in OSN by employing polyacids as PANI dopants for the first time. The PANI membranes were doped with two polyacids with different molecular weights (MW) and acid dissociation constants (pKa): namely poly(4-styrenesulfonic acid) (PSSA, MW: 75000 g mol −1 , pKa: 0.94) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA, MW: 800000 g mol −1 , pKa: 0.87), and were compared with a small acid (HCl) doped PANI membrane. The polyacid doped membranes, PANI-PSSA and PANI-PAMPSA, obtained dense structures with increased hydrophilicity due to strong intermolecular interactions between the PANI and the polyacids. Stability tests showed that the PANI-PSSA and PANI-PAMPSA were stable in a wide range of polar and nonpolar solvents, while the undoped PANI and PANI-HCl had poor stability in these solvents. The swelling degree and permeance of the doped membranes decreased with the increase of the dopant MW. The PANI-PAMPSA membrane exhibited a molecular weight cut-off (MWCO) in the nanofiltration (NF) range of 400 g mol −1 in methanol and isopropanol, while the PANI-HCl and PANI-PSSA membranes were in the ultrafiltration (UF) range. This study demonstrates that polyacid doping can make stable and nanoporous PANI membranes for OSN applications without the need for crosslinking. This simple approach can be used to design new classes of OSN membranes for challenging separation processes in the future. [ABSTRACT FROM AUTHOR]

The method of McCabe-Thiele is widely used for the design of distillation columns. At a given pressure, this graphical method is only based on 3 equations: (i) the partitioning curve linking the liquid and gas phases for a given component at a given plate thanks to a unique set of thermodynamic data and (ii) two operating lines, each one describing the liquid/gas equilibrium of two consecutive plates either in the enrichment section or in the stripping one. In this paper, the method has been adapted to the membrane separation processes aiming at the easy selection of a first set of appropriate designs of cascades that fulfill given separation targets, especially in the case of a binary mixture of components having both intermediate rejections and very different concentrations. Membrane cascades involving several recyclings of the permeate and retentate streams are proposed according to a similar but more sophisticated methodology than for distillation, since for a selected membrane and for given hydrodynamic conditions (pressure, velocity, temperature), several proposals can be made for each equation mentioned above. In short, a set of operating lines is generated varying with the volume reduction ratio (VRR) either for the permeate or the retentate retreatment sections. The method is applied to the OSN separation of a final synthesis medium of a homogeneous catalyzed reaction, namely olefin hydroformylation achieved in toluene. This example is a typical one dealing with the more general case of a product to be extracted in the permeate and a catalytic system to be recovered in the retentate for further recycling in the synthesis reactor aiming at a greener production process. The initial concentration ratio of the two components to separate in OSN is 1/1000 and both compounds have intermediate rejections of 30% and 88%. Thanks to this method, the design of several membrane cascades is proposed and discussed according to different goals of separation (target product purity or recovery, enrichment of component to be recycled, energy consumption, etc.). [ABSTRACT FROM AUTHOR]

Due to the lack of efficient membranes to achieve subtle separations in a single step, membrane cascades appear as an alternative to improve the separation of solutes, especially in the case of close rejections. However, there is still a need for their rational design. In this work, a systematic study of all configurations up to seven stages is proposed through a unique and flexible simulation architecture. Different recycling modes in between stages are detailed and developed. The same VRR is imposed at each stage, ranging from 2 to 10. The case study is the olefin hydroformylation catalytic reaction, for which the simulations aim at the separation of two components, one modelling all organic products to extract in the permeate and the other one modelling the catalytic system to recover in the retentate for its further re-use in the synthesis reactor. Input data for the simulations (rejections and fluxes) are obtained from preliminary experimental studies. The separation performances are evaluated through seven criteria, amongst which the outflows extraction/recovery and the membrane area. The analysis of the simulation results allows to determine the optimal configuration that fulfills the targeted criteria or to fine tune these separation criteria according to the potentialities or the limitations of the membrane cascades. Even though focusing a priori on specific criteria, a careful attention should be paid to all parameters to ensure realistic proposals of cascades or to revise the objectives for more realistic ones. [ABSTRACT FROM AUTHOR]

By direct introducing ionic liquid into the interfacial polymerization process of β-CD, the porous monomer based thin-film composite membranes are fabricated for efficient organic solvent nanofiltration with a high ethanol permeance of 57.01 L·m−2·h−1·MPa−1 and an ideal dye rejection rate of 99.98 %. [Display omitted] • IL assists the interfacial polymerization of porous monomers into membranes. • The TFC membranes exhibit high ethanol permeance and ideal dye rejection. • The effects of IL on the membrane structure and separation property are studied. β-cyclodextrin (β-CD), with intrinsic nano-cavity, is a promising monomer to construct thin-film composite (TFC) membranes for molecular separations. Nevertheless, interfacially polymerize β-CD into continuous membranes is challenging due to the low reactivity of hydroxyl groups. To address this issue, in this work, ionic liquid (IL) has been introduced into the interfacial polymerization (IP) process of β-CD and trimesoyl chloride (TMC), forming high-quality TFC membranes for organic solvent nanofiltration (OSN). Investigations have been done into how IL effects membrane structure and separation performance. In contrast to traditional β-CD-TMC TFC membrane, the β-CD-IL-TMC TFC membrane possesses upgraded crosslinking, continuity, stability, and OSN separation property. The best β-CD-IL-TMC membrane has an ethanol permeance of up to 57.01 L m−2h−1 MPa−1 and Naphthol green B rejection rate of 99.98% and can sustain a stable separation performance within 20-hour test, indicating the fabricated β-CD-IL-TMC membranes have advantage of separating and purifying organic solvent. [ABSTRACT FROM AUTHOR]

We have fabricated mixed matrix membranes (MMMs) consisting of carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs-COOH) and P84 polyimide in this study for organic solvent nanofiltration (OSN) with the aid of chemical cross-linking by 1,6-hexanediamine (HDA). A moderate annealing is also used to manipulate the pore size for a better solute rejection. The incorporation of hydrophilic carbon nanotubes into P84 not only improves liquid sorption and transport but also increases membrane porosity and pore size. As a result, the permeances of water, ethanol, and isopropanol across the MMMs increases with an increase in MWCNTs-COOH loading up to 0.075 wt.%. However, a higher loading of MWCNTs-COOH reduces the separation performance. The cross-linked MMM comprising 0.05 wt.% MWCNTs-COOH has a rejection of 85% to rose bengal (1017.65 Da) while ethanol permeance is 9.6 LMH⋅bar −1 at 5 bar. Interestingly, the rejection of rose bengal in isopropanol solutions is higher than that in ethanol solutions (i.e., 99 vs. 85%). After thermal annealing at 150 °C in a 3/1 EG/PEG400 (weight ratio) solution, the resultant membranes (MMM comprising 0.05 wt.% MWCNTs-COOH) show superlative rejections to small dye molecules (almost 100% to Safranin O dye molecules, 350.85 Da) in ethanol solutions. There is an obvious trade-off between rejection and permeance among the fabricated membranes, in which, the permeance enhancement and rejection diminishing occurred with the addition of MWCNTs-COOH; however, a vice-versa trend was observed in annealed membranes. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration has emerged as a versatile tool for process intensification in chemical production. Due to the complex interactions between membrane, solvent and solute, the transport mechanism has not yet been clarified and it is rather difficult to identify the best membrane for a given separation problem. Currently, this is solved by time-consuming and costly membrane screening experiments. To accelerate process development an heuristic for membrane selection is required. Therefore, the rejections of different substances with varying functional groups out of a material class of specialty chemicals were measured. The most typical membrane materials (Polydimethylsiloxane and Polyimide) and a wide range of solvents were used. From these experiments, parameters were identified which influence the membrane performance. A combination of these parameters in an heuristic allows for the identification of the most suitable membrane for a given separation problem. [ABSTRACT FROM AUTHOR]

The use of OSN in the production of edible oil conserves energy making it extremely attractive, however, it should be noted that a physically and chemically stable membrane for this is required. Considering this, we selected the AF2400/PTFE composite membrane to recover hexane from the crude mixture of soybean oil and hexane via the OSN process. We carried out pure solvent permeation and rejection experiments, which verified the effectiveness of the membrane in separating and recovering hexane or other aliphatic solvents. We also conducted a comprehensive study on the effect of operational parameters, including long-term operation, transmembrane pressure, oil concentration and operational temperature. Permeate flux value varied in the range of 0.8–1.1 l m −2 h −1 bar −1 with oil rejection above 98% before or after physical aging for 1440 h in pure hexane. Experimental results confirmed the effectiveness of the AF2400/PTFE composite membrane in hexane recovery, showing high oil rejection and excellent long-term operational stability. We attributed the excellent performance of the AF2400/PTFE composite membrane to its unique surface properties, confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The study presented herein indicates that fluoropolymer based membranes are promising candidates in aliphatic solvent separation via the OSN process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pore size of the ZIF-67 was enlarged by thermal annealing treatment. • The intercrystalline cracks in ZIF-67 layer were eliminated. • The permeance of the annealed ZIF-67 membrane was enhanced by two times. • The annealed ZIF-67 membrane had high rejection for pharmaceutical molecule. • The annealed ZIF-67 membrane exhibited stable separation performance. Zeolitic imidazolate frameworks (ZIFs) have been attracting intensive attention in membrane separation fields because of their ultrahigh specific surface areas, well-defined apertures, and variable topological characteristics. However, the aperture sizes of ZIFs are smaller than the kinetic diameters of most organic solvent molecules, which impedes their applications in organic solvent separation. Herein, we develop a thermal annealing-derived methodology for defect engineering on the ZIF-67 membrane. This post-synthetic modification not only expanded the aperture size of ZIF-67 but also repaired intercrystalline cracks in the polycrystalline ZIF-67 layer. By controlling the thermal annealing conditions, the permeability of the polycrystalline ZIF-67 membrane toward organic solvent nanofiltration was enhanced by two times. Moreover, the annealed ZIF-67 membrane showed a high rejection of more than 99.6% for dyes (Evans blue) and pharmaceutical molecules (tetracycline, vitamin B12). This work provides an avenue for the controllable modification of ZIFs membranes to broaden their applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic solvent nanofiltration is a promising method for dendrimer purification. • Tight regenerated cellulose membranes are applicable in a range of organic solvents. • Effective pore size of cellulose membranes can be fine-tuned by solvent polarity. • Permeability of small solutes is affected more by their polarity than by their size. • Model assuming constant transmission shows a good agreement with experimental data. The performance of commercial cellulose membranes with pore size on the border between ultra- and nanofiltration in selected organic solvents was studied focusing on rejection of small solutes and applicability for dendrimer purification. Organic markers in the MW range 100 – 700 Da and polarity range from nonpolar to polar protic compounds (aliphatics, aromatics, ethers, esters and alcohols) were used for membrane characterization. Transmission experiments in mixtures of methanol and dichloromethane of variable ratio showed the suitability of tested membranes for intended purpose, bringing information on structural factors affecting the rejection. Besides solute molar volume, its polarity type, or affinity, most conveniently expressed by Hansen solubility parameters, was found to be a crucial factor; with increasing size of solute molecule the spatial arrangement becomes also important. Solvent composition influences not only the behavior of solutes, but it also affects the membrane structure: poor solvation of cellulose by less polar solvents causes partial pore collapse, resulting in a decrease of membrane molecular weight cutoff. This effect can be used to improve the retention of a target product, as was shown for the first generation amphiphilic dendron. In addition, a simple mathematical model, allowing to estimate the course of nanofiltration and to optimize its conditions in a semicontinuous dead-end setup, is presented. [ABSTRACT FROM AUTHOR]

[Display omitted] • Machine learning was used to form prediction models for TFN-OSN membrane performance evaluation. • 20 references including 9252 data points were collected to form four different models: linear, SVM, BT, and ANN. • BT exhibited optimal prediction accuracy for membrane RP and RS performance prediction. • Partial dependence analysis provided the optimal conditions for TFN-OSN membrane fabrication. • Membrane with super-hydrophilic or super-hydrophobic surface property exhibited higher RP performance based on different feed solvent types. In this study, machine learning was used to form prediction models for thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane performance evaluation in terms of relative permeability (RP) and relative selectivity (RS). Twenty references including 9252 data points were collected to form four different models: linear, support vector machine (SVM), boosted tree (BT), and artificial neural network (ANN). Among the four models, BT exhibited optimal prediction accuracy in terms of root mean square error (RMSE) and coefficient of determination (R2) values for membrane RP (RMSE: 0.295, R2: 0.918) and RS (RMSE: 0.053, R2: 0.849) performance prediction. Parameter contribution analysis indicated that nanoparticle loading, amine concentration, chloride concentration, water contact angle, solvent viscosity, and molar volume are the main parameters influencing RP performance. For RS performance, nanoparticle loading, amine concentration, chloride concentration, and solute molecular weight play important roles. Partial dependence analysis indicated that the optimal conditions for TFN-OSN membrane fabrication are nanoparticle loading less than 5 wt%, the amine concentration around 2 wt%, and the chloride concentration around 0.15 wt%. In addition, membrane with super-hydrophilic or super-hydrophobic surface property exhibited higher RP performance based on different feed solvent types. Overall, this work introduces new ways both for TFN-OSN membrane performance prediction and for higher performance membrane design and development. [ABSTRACT FROM AUTHOR]

[Display omitted] • A polyimide aerogel was applied as a versatile support for TFC and COF nanofiltration membranes. • Solvents and temperature affected the performance of the COF@aerogel membrane. • The pore flow model described the separation performance of the COF@aerogel membrane. • Stable performance was achieved under continuous, crossflow filtration for more than 9 days. • The polyimide aerogel support exhibited superior solvent resistance up to 6 months. Organic solvent nanofiltration (OSN) membranes require robust selective layers and support materials. In this study, polyamide and polyester thin-film composites (TFCs) and covalent organic frameworks (COFs) were fabricated as selective layers on a polyimide aerogel support. The ultrapermeable support was stable in various organic solvents including harsh polar aprotic solvents such as N , N -dimethylformamide (DMF), dimethylsulfoxide, N , N -dimethylacetamide, and N -methyl-2-pyrrolidone for more than six months. The support enabled fabricating both amorphous and crystalline selective layers at both room and higher temperatures. Moreover, the polyimide aerogel support had 85% porosity, facilitating high solvent flux. The compatibility of the selective layers and support was excellent, and as low molecular weight cutoff values (MWCO) as 356 and as high as 591 g mol−1 were obtained in methanol at 10 bar for the COFs and polyester TFC membranes, respectively. Both experimental MWCO and permeance values of the COF membrane agreed with those predicted using the pore flow model. The effect of the operating temperature on the OSN performance was examined in DMF at 20 and 100 °C. Both membranes demonstrated constant permeance and rejection for more than nine days of continuous filtration. [ABSTRACT FROM AUTHOR]

• The nanofilm with high microporosity was prepared from a novel Tris-Phenol monomer. • Surfactant DTAC addition improved the selectivity of the Tris-Phenol OSN membrane. • The MWCO of Tris-Phenol membrane was as low as 295 Da in solvent methanol. • It showed not only size selective mechanisum but also a charge selective behavior. As an emerging membrane separation technology, organic solvent nanofiltration (OSN) has shown great application potential in the field of pharmaceutical and chemical industries referring to organic media. Herein, we prepared a novel microporous thin-film composite (TFC) OSN membrane with superior perm-selective performances, which was fabricated by applying 4,4′,4″-trihydroxytriphenylmethane (Tris-Phenol) to react with trimesoyl chloride (TMC) by interfacial polymerization (IP) technique. The rigid, non-planar and multifunctional nature of Tris-Phenol endowed the polyarylate nanofilm with enhanced microporosity. Of note, the prepared composite membrane showed good selectivity to small organic solutes with molecular weight cut-off (MWCO) as low as ∼295 Da, meanwhile had medium methanol permeance up to 5.86 LMH/bar, by the help of surfactant dodecyl trimethyl ammonium chloridea (DTAC) during the IP reaction. The experiments showed that the Tris-Phenol membrane exhibited extraordinary long-term operation stability. In addition, the Tris-Phenol membrane could achieve separation of solutes with similar molecular weights but different charges. This research well illustrated the novel IP monomer design strategy to fabricate new TFC OSN membrane with high perm-selectivity. [ABSTRACT FROM AUTHOR]

For the first time, the non-ionic surfactant Marlipal 24/70 was removed from 1-dodecene using organic solvent nanofiltration. Fluxes of up to 40 Lm −2 h −1 and retentions of more than 90% were achieved. The flux increase with increasing pressure was non-linear, whilst the retention increase appeared to be almost linear over the observed range. Both effects could be attributed to membrane swelling and compaction which influence the morphology of the membrane. Retention decreased with increasing temperature whilst the flux increased. It could be shown that the temperature influence on the pure solvent flux might be due to a decrease in solvent viscosity, additional to the increased membrane swelling at higher temperatures, which strongly influences the retention of surfactant solutions (retention is reduced). Higher surfactant concentrations led to lower fluxes but to substantially higher retentions due to a decreased membrane swelling degree, surfactant aggregation into micelles, or increased adsorption onto the membrane. The characteristic membrane behaviour seen in this study can be coherently explained but additional effects have been carefully considered. Additionally, the experimental data were compiled to allow, firstly, predictions of the number of batch filtration steps needed to achieve a certain surfactant concentration in the permeate and, secondly, the determination of the characteristic membrane performance. [ABSTRACT FROM AUTHOR]

A concept is demonstrated for the separation of two organic solutes from a common solvent by solvent swing adsorption (SSA), coupled with organic solvent nanofiltration (OSN) for solvent recycling. The polymer of intrinsic microporosity PIM-1 was utilized both for the adsorbent and for the nanofiltration membrane. For adsorption from solution in ethanol or water–ethanol (30/70) mixture, PIM-1 showed high affinity for a neutral solute (Oil Red O) with negligible uptake of an anionic solute (Remazol Brilliant Blue R). The obtained equilibrium values of distribution coefficient K revealed that Oil Red O can be concentrated in PIM-1 by 4300 times from its ethanol solution, and this value can be significantly improved up to 53,000 times in the case of water/ethanol (30/70) binary mixture. Such difference in the affinity of neutral solute to PIM-1 was explained by means of competitive sorption between solute and solvent molecules, and a clear relationship between distribution coefficient K and solvent solubility parameter was observed. The adsorbent could be regenerated by washing with a less polar solvent (toluene), which gave almost quantitative desorption of the neutral solute ( K = 6). PIM-1 membranes as cast and after cross-linking were also successfully utilized for solvent recovery. It was demonstrated that PIM-1 membranes can possess either solvent-selective transport or solute-selective transport in OSN, depending on the nature of the solvent. [ABSTRACT FROM AUTHOR]

A new generation of membranes modified by using Grignard reactions was recently introduced. These alkyl modified membranes have an enhanced hydrophobicity, and a potential for organic solvent nanofiltration (OSN). In this work, the solvent filtration performance and application potential of these Grignard functionalized membranes were further explored. To this purpose, the retention of model solutes using a variety of grafted and ungrafted membranes was investigated in 5 different solvent/solute test mixtures. Experiments were performed with two different solvents, acetone with intermediate polarity and toluene as an apolar solvent, and 3 different solute classes, namely polyethylene glycol, polystyrene and a well-known catalyst ligand. The varying retention behavior can be explained by the changing affinity of solvents and solutes for the modified and unmodified membrane surfaces. Results of sorption tests confirm this conclusion. Subsequently, filtration of a phosphine mixture in isopropanol containing different solutes with similar size but varying polarity, showed the clear potential of affinity-based separations with Grignard modified membranes. A filtration test during four days revealed that the grafted groups are sufficiently stable. As a conclusion, Grignard functionalization of ceramic membranes allows to tune solvent–membrane–solute interactions in OSN in a controlled way for specific separations, without the extra complexity of swelling. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile method of crosslinking polybenzimidazole membranes using KMnO 4. • Crosslinking is quick and performed under relatively green and mild conditions. • Membrane shows superior separation performance and solvent stability. • No significant change in the membrane with either polar or nonpolar solvents. • Applications in petrochemical and pharmaceutical industries. Herein, a facile method for crosslinking polybenzimidazole membranes applied in organic solvent nanofiltration (OSN) using an aqueous potassium permanganate (KMnO 4) solution is presented. The membranes were crosslinked under mild water-based conditions at room temperature for less than 4 h. The crosslinked polybenzimidazole OSN membrane exhibited superior separation performance and enhanced stability in various solvents, including dimethylformamide and N -methyl-2-pyrrolidone. The crosslinked membranes exhibited greater than 90% rejection rate for dyes with molecular weights in the range of 327 to 1017 Da, and they were compatible with various common organic solvents such as ethanol, isopropyl alcohol, acetone, and dimethylformamide. Furthermore, no significant change in the membrane performance was observed when polar and nonpolar solvents were used in filtration experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous covalent organic polymer (COP) selective layer was synthesised on polybenzimidazole (PBI) supports. • Positively charged composite membranes with high salt retentions. • Composite COP membranes demonstrated excellent solvent and pH stabilities. • COP is further crosslinked to reduce the molecular weight cut off (MWCO) Here we present the preparation of a novel positively charged covalent organic polymer (COP) based nanofiltration membrane. The porous COP selective layer grows on top of a polybenzimidazole (PBI) support from coupling reaction of 1,3,5-tris(bromomethyl)benzene and 4,4′−dipyridyl in alkaline conditions. Chemical and morphological analyses confirm the formation of a thin layer of COP (less than 50 nm), which is also evidenced by its high water permeance and salt retentions. Moreover, it is shown that COP membranes can form hydrogen bonds with HNO 3 , leading to a tighter membrane pore size that increases the NaCl retention from 46% to 75% without significantly losing its permeance. Further, the composite membranes demonstrated exceptional solvent and pH stabilities. The COP membranes showed a molecular weight cut off between 400 and 1000 g mol−1 together with pure solvent permeances of 0.91, 2.4, 3.3, 7.1 and 9.5 Lm−2h−1bar−1 toward dimethylformamide (DMF), ethanol, acetone, methanol an acetonitrile, respectively. The remarkable performance together with the stability in harsh environments make the newly developed COP membranes an attractive candidate for extreme nanofiltration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thin TiO 2 -ZrO 2 -DTBC composite membranes were fabricated. • Pore sizes and surface properties were controlled by changing the firing conditions. • Surface free energy was calculated to consider the membrane-solvent interactions. • Membrane-solvent interactions, viscosity, and solvent size affected the solvent permeance. TiO 2 -ZrO 2 -(3,5-di- tert -butylcatechol, DTBC) composite membranes were fabricated via the sol–gel method under four different firing conditions: 300 °C (N 2), 300 °C (Air), 350 °C (Air), and 500 °C (Air). The chemical structure of the DTBC originated organic material in the composite was controlled by setting the firing temperature. The average pore sizes of the membranes were 1.0–1.1 nm when fired at 300 °C, 1.4 nm at 350 °C, and 2.1 nm at 500 °C. The molecular weight cut-off of the membranes (in daltons) in water ranged from 480 to 535 when fired at 300 °C, 890 at 350 °C, and 1,680 at 500 °C, whose corresponding molecular diameter was in good agreement with the average pore size measured via nanopermporometery. Permeation tests of the organic solvents showed that the membrane-solvent interaction affected the permeation mechanism in addition to the solvent viscosity and the occupied area of the solvent molecules. The surface free energy difference between the membrane and the solvent expressed the interaction between the membrane and the solvent molecule. The proposed solvent permeation model was examined and showed better agreement with the experimental results compared with the model based on the solubility parameters of a solvent. The organic solvent permeation mechanism of the ceramic NF membrane was greatly affected by the membrane-solvent intermolecular interaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Systematic investigation of dissolved gas on solvent flux. • Gas flux is correlated with gas solubility in the solvent. • Gas solubility needs to be considered for membrane testing and process design. The first step in quantifying the performance of organic solvent nanofiltration membranes are usually lab-scale experiments with respect to flux and rejection. The necessary pressurization of the feed is either realized mechanically by a high-pressure pump or by means of a pressurized inert gas. While the latter option is most frequently applied, the gas may dissolve in the feed mixture and permeate through the membrane, affecting the transport of the other components. This potential effect is commonly neglected, inherently assuming that the gas solubility is negligible. The current study provides a systematic experimental investigation and analysis of the impact of dissolved gases on solvent flux for a hydrophilic DuraMem membrane, with gas solubilities assessed through PC-SAFT. The results prove that a gas with low solubility has a negligible effect on the solvent flux. In contrast, an increasing gas solubility may result in significant gas flux through the membrane with a considerable effect on the solvent flux. Furthermore, the correlation of the solvent flux with the gas solubility in the feed mixture is strongly non-linear. Therefore, gas solubility is recommended to be critically evaluated when conducting OSN experiments, specifically considering the final application. In that context, the permeation of dissolved gas has to be actively accounted for in OSN experiments for gas–liquid systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] Different solutes fractionation was proposed and realized by OSN. [•] Practical application of negative retention in OSN for solute separation. [•] Membranes made of PTMSP can be successfully applied for dyes fractionation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultra-low concentration for both MPD and TMC used during the interfacial polymerization process. • Ultra-low content Tannic acid functionalized MoS 2 nanosheets regulate the interfacial polymerization process. • Ultra-thin, ultra-smooth (2 nm in roughness) and hydrophilic TFN OSN membrane was obtained. • The TFN OSN membrane achieves a much higher pure DMF permeance of 219 L m−2h−1 MPa−1. • The TFN OSN membrane tolerates DMF at 80 ℃ for greater than 144 h and remains greater than 98% RDB (479 Da) rejection. Organic solvent nanofiltration (OSN) membranes are the key factors for the treatment of organic solution via OSN technology. In this work, we fabricated a kind of ultra-thin and ultra-smooth thin-film nanocomposite (TFN) OSN membrane using interfacial polymerization (IP) process with ultra-low concentration for both the aqueous and the organic monomers, together with doped tannic acid (TA) functionalized Molybdenum disulfide (MoS 2) nanosheets of ultra-low content in the aqueous monomer solution, and followed by post-IP chemical crosslinking and solvent activation procedures. The results demonstrated that the incorporated TA-MoS 2 nanosheets not only help to promote the solvent permeation, but also help to increase the solvent resistance and fouling resistance of the fabricated membrane. The optimal TFN OSN membrane fabricated using 0.05 wt% aqueous m -phenylenediamine (MPD) solution doped with TA-MoS 2 nanosheets content of 50 mg L−1 and 0.0025 wt% trimesoyl chloride (TMC) / n -hexane solution has an ultra-thin barrier layer, with an average thickness of about 15 nm. This endows it a much higher pure DMF permeance of 219.1 L m−2 h−1 MPa−1, which is much superior over most of literature works. Meanwhile, the fabricated TFN OSN membrane achieves a rejection of 99.1 % for rhodamine B (RDB, 479 Dalton), which is about 10.1 % increment compared with that of the baseline thin-film composite (TFC) membrane. The TFN OSN membrane also features an ultra-smooth skin layer, with a surface roughness of merely about 2.0 nm, which is quite beneficial for its fouling resistance performance. Moreover, the TFN OSN membrane features outstanding high solvent resistance. It remained a nearly constant and extremely high rejection for Rose Begal (RB, 1017 Dalton), about 99.9 %, and a much higher DMF permeance, 101 ± 2 L m−2 h−1 MPa−1, after cross-flow filtration for more than 200 h using 100 mg L−1 RB / DMF solution as feed, which is seldomly reported in literature. Even being immersed in DMF at 80 °C for more than 144 h, it remained a rejection of higher than 98 % for Rhodamine B (479 Dalton), indicating its superior solvent resistance and promising industrial application prospect. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel n-TFC membrane was developed by IP method on PEI/modified SiO2 support. [•] The amino-functionalized silica was blended with PEI to prepare solvent resistant support. [•] Effect of modified nanosilica on chemical and physical stability of support was studied. [•] Support morphology influenced the performance of resultant n-TFC membrane. [•] n-TFC membrane has proper lube oil rejection even at high pressure for OSN process. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simplified membrane cascade process that overcomes previous control problems is proposed. [•] The process operates using a single high-pressure pump and without any buffer tank between membrane stages. [•] The process was experimentally validated by increasing the process yield from 59% to 94%. [•] It has been shown that recycle ratio and operating pressure affects the yield and purity significantly. [•] A mathematical model to predict the cascade performance is developed. [Copyright &y& Elsevier]

Highlights: [•] Organic solvent nanofiltration in toluene. [•] Retention of organometallic pre-catalyst is better than 99.5% at 40bar. [•] Ring closing metathesis achieved in a semi-continuous membrane reactor at 40bar. [•] Ring closing metathesis achieved in a continuous membrane reactor at 40 and 10bar. [•] Comparison of the two membrane reactors. [Copyright &y& Elsevier]

Highlights: [•] Purification of an API intermediate via Organic solvent nanofiltration. [•] Change in the rejection profile on addition of an acid. [•] The type and quantity of acid was investigated. [•] The requirement for some water in the solvent was shown. [•] Effect of aqueous acid on membrane stability. [Copyright &y& Elsevier]

Abstract: Two new solute fractionating membrane cascade configurations have been proposed, with the aim of introducing a flexible solute fractionation system that can be modified rapidly. Solute fractionation, using a cascade where the more permeable solute is stripped, has been simulated. It was shown that the separation performance was driven by the relative permeability of solutes through the membrane. This cascade can reduce solvent usage significantly and increase separation yield with minimal stages added. Furthermore, the cascade is more productive and effective in solute fractionation than constant volume diafiltration. The development of a fractionation strategy for the separation of a developmental active pharmaceutical ingredient (API) from an excess reagent is described and was demonstrated using a 3-stage permeable stripping cascade. A binary feed solution, containing the API and the excess reagent, was stripped of the reagent to produce a product stream enriched in the API. This product stream could be further polished using a single crystallisation step, which was otherwise impossible with the original feed solution. The proposed process model was shown to be in general agreement with experimental data. [Copyright &y& Elsevier]

Abstract: The present study evaluates the adequacy of different approaches for the removal of 1,3-diisopropylurea (IPU), a potentially genotoxic impurity (GTI) from active pharmaceutical ingredients (APIs). The use of Organic solvent nanofiltration (OSN) to separate APIs and IPU, based on their molecular size difference was first evaluated using different membranes and solvents, and GMT-oNF-2 membrane was tested in diafiltration mode for the removal of IPU when dissolved in dichloromethane (DCM). A diafiltration dilution ratio of 3 was found as optimum to achieve 90% removal of IPU with a 2.5% loss of the model API. A novel IPU-selective Molecularly Imprinted Polymer (MIP) was then used for final polishing to remove remaining IPU. Hence, below 100ppm IPU, IPU removal of 83% was achieved in one single stage. A selective elution system was also developed, consisting of the use of methyl isobutyl ketone (MIBK) in the first steps to recover virtually all the API that binds non-specifically to the MIP scavenger and methanol on the later steps to remove IPU and recover the MIP. The selectivity and stability of the MIP scavenger was validated over 18 independent operations using the same MIP sorbent. The combination of OSN with a diafiltration dilution ratio of 3 and a single MIP polishing stage allows reducing the IPU contamination from 100mgIPU/gAPI to 2mgIPU/gAPI with an API loss, mostly at the OSN stage, of about 3%. The results obtained using the hybrid OSN–MIP process were compared to those using MIP scavengers or OSN alone. The MIP–OSN hybrid approach, combining the advantages of both techniques, offers an attractive new approach for API purification. [Copyright &y& Elsevier]

Abstract: Due to their excellent resistance to a range of solvents, integrally skinned polyimide membranes have been used to achieve selective separations in a range of solvent-based industrial and lab-scale chemical operations. These include: homogeneous catalyst recycle, petrochemical dewaxing, solvent exchange and chiral resolutions. However, despite the widening scope of use of these membranes, there is still little understanding of how the microstructure defines their separation performance. As a first step towards determining this, integrally skinned nanofiltration membranes were fabricated by phase inversion using Lenzing P84 polyimide. The microstructures of these membranes, dry and wetted in solvent, were investigated by SEM, TEM and ESEM (where appropriate). SEM and TEM imaging of dry membranes revealed that this type of polyimide membrane has three microstructurally distinct polyimide layers, not the two indicated in prior literature. Furthermore, TEM images reveal nano-sized pore-like features in the polyimide structure, which indicate that the transport mechanism is probably neither only solution-diffusion nor only pore flow. ESEM imaging showed that when saturated in ethanol at the working pressure of the ESEM (5.50Torr), the microstructure of the membranes changes; it is wispy and thus quite different to the more solid polymer nodules and interconnected polymer network observed in the dry membranes. Thus, transport and separation mechanisms based on the structure of the dry membranes may not be accurate. Overall, these results indicate that the current theory used to describe polyimide membrane mass transfer and separation performance (where it is based on dry membrane microstructures), most likely needs to be rethought. [Copyright &y& Elsevier]

[Display omitted] • Crosslinked polydimethylsiloxane (PDMS) composite membranes were developed. • The influence of PDMS molecular weight on solvent separation was evaluated. • Various solvent mixtures containing hexane and alcohols were separated. • Low molecular weight PDMS membranes showed less swelling and higher selectivity. • Solvent permeation and separation were due to membrane swelling and solvent dissolution. • Interaction of alcohol and hexane with PDMS determined the separation coefficient. Membrane processes have proven to be energy-efficient technologies for separation of various substances, including organic solvents. In this study, crosslinked polydimethylsiloxane (PDMS) composite membranes were developed for organic solvent separation. Precursor solutions containing double-ended vinyl PDMS with four different molecular weights were spin-coated onto a polyethersulfone membrane substrate, and the crosslinking reaction was accelerated by heat treatment to produce PDMS composite membranes. The influence of the PDMS molecular weight and crosslinking on the membrane properties and performance was tested. It was shown that less swelling, more selective hexane absorption, and increased separation coefficient was observed with decreasing PDMS molecular weight. The trade-off relationship between the permeance and the separation coefficient was observed as the membranes prepared with lower molecular weights of PDMS showed lower permeability and higher separation coefficient. The separation coefficient showed a maximum value at a supplied ethanol concentration of 50 wt%. In addition, various solvent mixtures containing hexane and alcohols were used for organic solvent separation performance test using the PDMS composite membranes. A correlation was observed between the separation coefficient and the difference of χ parameters between alcohol/PDMS and hexane/PDMS. The mechanisms for solvent permeation and separation were discussed based on the interaction parameters, membrane swelling and solvent dissolution. The results of this study could be used as guidelines for the development of solvent-resistant PDMS composite membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four porphyrin-based MOFs were synthesized as nanofillers for membrane fabrication. • 2D porphyrin–based MOFs have high compatibility with the P84 polymeric matrix. • The optimal MMMs exhibited 3-folds enhancement in permeance without rejection loss. • Ultrasonic treatment of Cu-TCPP further increased dispersion and OSN performance. • Stable OSN performance (36 h) was observed for separating VB12/ethanol solutions. Mixed matrix membranes (MMMs) are promising candidates for organic solvent nanofiltration (OSN), but the thick separation layer and poor compatibility between polymer and fillers are two critical challenges needed to be solved. Herein, a series of tetrakis(4-carboxyphenyl)porphyrin (abbreviation: TCPP) based metal–organic frameworks (MOFs, M−TCPP (M=Zn, Cu, Co, Ni)) have been synthesized in the form of two–dimensional nanosheets, which were then used as thin fillers in P84 matrix to fabricate M−TCPP/P84 MMMs for the OSN application. The effects of the types of M−TCPP and loading contents in the resultant MMMs on the OSN performance were systematically investigated. All the obtained MMMs exhibited higher permeance and slightly declined rejection of brilliant blue R (BBR) as compared with the pristine P84 membranes, among which Zn-TCPP/P84 MMM showed the greatest permeance improvement due to its flower-like structure assembled by wrinkled nanosheets as building blocks. Moreover, the permeance of MMMs showed volcanic type curves as increasing the MOFs loading content, while the rejection did not sacrifice too much. The optimum loading contents for Cu-TCPP/P84 and Zn-TCPP/P84 MMMs were 1 wt% and 1.5 wt%, respectively. In addition, the water-stable Cu-TCPP MOF can be further disassembled by an ultrasonic probe to achieve monodispersed Cu-TCPP nanosheets. It is interesting to find that the permeance of the MMM incorporating 1.5 wt% of the monodispersed Cu-TCPP nanosheets was enhanced nearly 2-fold as compared with the MMM with the untreated Cu-TCPP MOFs and the rejection to BBR only slightly decreased (94.7 vs. 95.7%). Besides, the general applications of Cu-TCPP/P84 membranes for other organic solvents (methanol, isopropanol, acetone, acetonitrile, hexane, etc.), diverse organic dye/ethanol separation, vitamins B12/ethanol long-term separation test (36 h) indicated that the M−TCPP−based MMMs have great potentials in the field of organic solvent-related separation. [ABSTRACT FROM AUTHOR]