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To expand industrial utilizations, membranes with fast transport of organic solvents and precision molecular separation, along with strong chemical stability, have great potential for minimizing energy consumption in separation processes. In this study, novel amino-cyclodextrin organic solvent nanofiltration (OSN) membranes containing P84 polymer were successfully fabricated using amino-cyclodextrin and amino-5-guanidinopentanoic acid (DL-A) as monomers through a two-step green modification process. The resulting membranes exhibit high stability in harsh organic solvents, such as dimethylsulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP), with a weight loss of less than 5 % after 30 days of immersion. These membranes also demonstrate rapid solvent transport for both polar solvents, such as methanol (86.56 L m−2 h−1 bar−1), and nonpolar solvents, such as n-hexane (48.97 L m−2 h−1 bar−1), along with high dye rejections. Additionally, the membranes possess rigid nanopores structures and consistent rejections across different pressures and solute concentrations. Most importantly, the newly synthesized amino-cyclodextrin OSN membranes are capable of separating molecules based on their 3D structures, particularly those with relatively similar molecular weights. Comparing to those reported cyclodextrin-based membranes, the newly developed amino-cyclodextrin OSN membranes show significant improvements in permeance for both polar and nonpolar organic solvents, while maintaining comparable dye rejection capabilities. The combination of fast solvent transport, excellent chemical stability, and shape selectivity makes these membranes highly promising for high-performance molecular separation in various industrial applications. [Display omitted] • A novel P84 co-polyimide organic solvent nanofiltration (OSN) membrane incorporated with amino-beta-cyclodextrin, was prepared. • The amino-β-cyclodextrin-based membrane has faster solvent transport for both polar and nonpolar solvents. • The amino-β-cyclodextrin-based membrane exhibits excellent stability in harsh organic solvents. • The newly synthesized amino-cyclodextrin OSN membrane demonstrates excellent shape selectivity to solutes with similar molecular weights. [ABSTRACT FROM AUTHOR]

This study explores the potential use of sulfolane, a green and sustainable solvent, as an alternative to toxic solvents in the fabrication of high-performance nanofiltration membranes. A comparison of Hansen solubility parameter (HSP) with N -methyl-2-pyrrolidone (NMP) indicates that sulfolane is a "poor" solvent for the sulfonated polyphenylenesulfone (sPPSU) polymer, which results in a lower critical polymer concentration (CPC) required to produce a macrovoid-free membrane structure. Moreover, the addition of a low molecular weight hyperbranched polyethyleneimine (HPEI) of MW = 800 g/mol as a crosslinker enhances the mechanical rigidity of the membranes without affecting the pore structure required for retaining salts from dye/salt mixtures, enabling practical applications in wastewater treatment. Notably, the membranes demonstrate exceptional dye/salt separation performance with a separation factor S D y e / S a l t of up to 69.32, even for low molecular weight dyes as low as 268 g/mol (i.e., a Disperse blue 1 and Na 2 SO 4 mixture). To the best of our knowledge, this is the lowest MW dye ever tested for dye/salt separation. The membranes also show good antifouling capability over an extended period of use. Literature comparison shows that the sPPSU/sulfolane membrane crosslinked with HPEI800 for 60 min, referred to as sPSlf-c60, exhibits superior dye/salt separation performance, indicating their potential for the treatment of textile wastewater effluents. [Display omitted] • A green solvent, sulfolane, was successfully employed to substitute a toxic one. • Hansen solubility parameter (HSP) is crucial in determining polymer–solvent matrix. • HSP and critical polymer concentration analyses result in macrovoid-free membranes. • A green and simple modification process was done by using a low MW HPEI polymer. • Excellent dye/salt separation towards multiple dye and salt mixtures was achieved. [ABSTRACT FROM AUTHOR]

Novel beta-cyclodextrin (β-CD) incorporated P84 co -polyimide nanofiltration (NF) membranes were prepared via interfacial polymerization between N , N -bis(3-aminopropyl)-1,3-propanediamine (APPD) and beta-cyclodextrin (β-CD) in a green solvent. The effects of concentration and hydroxyl groups of β-CD on separation performance, surface hydrophilicity, and antifouling performance of the prepared membranes were analyzed. The results demonstrate that the 0.3β-CD/APPD/P84 membrane has a pure water permeability of 209.07 Lm−2 h−1 bar−1 at 2 bar. The membrane also shows effective dye/salt separation with a high dye rejection of 99.1 % to Congo red and a high salt permeation of 92.13 % to NaCl. The resultant membranes can also effectively separate binary dye solutions with different molecular weights because of the unique cavity structure of β-CD and inclusion complexation. In addition, the membranes exhibit excellent antifouling characteristics because the unreacted hydroxyl groups in the outer cavity of β-CD initiate strong hydrogen bonding with water molecules, which blocks the interaction between pollutants and the membrane surface. Comparing with other reported membranes, the newly developed nanofiltration (NF) membrane exhibits a higher water permeability and comparable separation performance to dye/salt mixtures. Furthermore, the membrane maintains a high dye rejection (Congo red, 98.67 %) and salt permeation (NaCl, 95.93 %) even at a high NaCl concentration of 40,000 ppm in dye/salt mixtures. Therefore, the novel β-CD incorporated NF membrane has a prominent potential for the treatment of salt-containing dye wastewater treatment with better dye/salt separation. [Display omitted] • Novel beta-cyclodextrin (β-CD) incorporated P84 co -polyimide nanofiltration (NF) membranes are prepared. • The β-CD-based membrane has high hydrophilicity and pure water permeability. • The β-CD incorporated NF membranes exhibit excellent antifouling characteristics. • The optimized membrane possesses high dye rejection and salt permeation for dye/salt mixtures. [ABSTRACT FROM AUTHOR]

We have molecularly designed negatively charged nanofiltration (NF) membranes by chemical modification of P84 flat membranes with hyperbranched polyethylenimine (HPEI) polymers and then infiltration of sulfocalix[4]arene (SCA4) to enhance their chemical stability and molecular sieving capability. The high molecular weight HPEI polymers developed a strong cross-linked network of P84 polymer chains with extraordinary chemical stability in solvents like N -methyl-2-pyrrolidone (NMP). In addition, the amine groups of HPEI ionically bonded with the electron-accepting sulfonic acid groups of SCA4, resulting in the cross-linked membranes with a proper pore dimension and enhanced size sieving capability. The NF membrane infiltrated with SCA4 in a 0.03 wt% SCA4 solution consisting of 50/50 (wt%) water and methanol for 8 h has boron rejections of 55.37 %, 67.23 %, 87.45 %, 89.95 %, and 98.24 % at pH = 4, 7, 8, 9 and 10, respectively. These performances are comparable with or superior to literature results for membranes made from thin-film interfacial polymerization. The unique SCA4 closed-loop structure not only enhances molecular sieving capability but also achieves negatively charged NF membranes that maximize the potential for removal of toxic ions. This study may provide useful insights to design NF membranes with the aid of supramolecular macrocycles for water reuse and removal of toxic ions. [Display omitted] • The P84 co-polyimide membrane is chemically and structurally modified with HPEI and SCA4. • HPEI builds a remarkable cross-linked network with polymer chains of P84. • The SCA4 incorporated membrane shows a smaller effective pore size and a sharper pore size distribution. • The unique SCA4 structure enhances the molecular sieving capability for boron removal. • The new NF membrane shows stable chemical stability in NMP and stable separation performance for boron removal. [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis and properties of new anion exchange membranes using m -polybenzimidazole (m -PBI) as polymer backbone attached with quaternary ammonium group and alkene group as side chains. These ionic m -PBIs were crosslinked by thermal thiol-ene reaction. The ion exchange capacity (IEC) values and crosslinking degrees were controlled independently by the amount of attached quaternary ammonium groups and alkene groups, respectively. m -PBI based AEMs with IEC from 1.51 to 2.50 mmol/g exhibit hydroxide conductivity of 14 to 58 mS/cm at 80 °C. With similar IEC values, crosslinked membranes absorb less water but show similar hydroxide conductivity and better dimension stability than uncrosslinked membranes. A crosslinked membrane with an IEC value of 2.46 mmol/g can retain 84% of its pristine hydroxide conductivity after being immersed in 1.0 M sodium hydroxide solution at 60 °C after 720 h. These membranes in hydrated condition also show mechanical robustness with tensile strength of 10.8 to 14.6 MPa. From the high hydroxide conductivity, enhanced alkaline stability and good mechanical properties, crosslinked ionic m -PBIs are promising candidate as anion exchange membranes for fuel cell application. Unlabelled Image • New thiol-ene reaction crosslinked m -PBI based AEMs are reported. • The crosslinked AEMs absorb less water and swell less than uncrosslinked ones. • Thiol-ene crosslinking enhances the alkaline stability and mechanical strength of AEMs. • Crosslinked AEMs with high hydroxide conductivity and low water uptake are achieved. [ABSTRACT FROM AUTHOR]

Polybenzimidazole (PBI), a polymer known for its superior chemical stability, thermal properties, and mechanical resistance has been regarded as a suitable membrane material for a wide range of applications. Herein, we took advantage of these properties and its amphoteric nature that could endow the formed membranes with capabilities to have different states and responses in different pH conditions for enhanced nanofiltration (NF) performance. Integrally skinned asymmetric flat-sheet PBI membranes were fabricated using the nonsolvent-induced phase separation (NIPS) method under various pH in a coagulant bath. For the first time, we have thoroughly investigated the effects of nonsolvent acidity and alkalinity on PBI membrane formation and their performances. It was revealed that the membrane formed under pH 12 showed a doubled MgCl 2 rejection than the one formed under pH 7. Moreover, a green modification method was employed to enhance the membranes' sieving capabilities by using hyperbranched polyethyleneimine polymers (HPEIs) with different molecular weights (MWs). The PBI membrane formed under pH 12 and then surface modified with a HPEI of MW = 25,000 g/mol (i.e., PBI 12–25K membrane) has a molecular weight cut-off (MWCO) as low as 288 Da and an MgCl 2 rejection more than 97%. The membrane also displays pH-responsive characteristics for salt separation with unequal valence ratios of co-ions and counter-ions. It is able to show a competitive S L i , M g value for Li+/Mg2+ separation surpassing the state-of-the-art performance of commercial membranes. [Display omitted] • pH-tuning of coagulant bath results in distinct membrane features and performances. • A green and simple modification process was employed by using a HPEI polymer. • Synergistic effects between the change in pH and the HPEI modification was proven. • The fabricated membrane shows a pH-responsive behavior towards different salts. • A high Li+/Mg2+ separation factor surpassing the commercial membranes was obtained. [ABSTRACT FROM AUTHOR]

The chemical, pharmaceutical, and edible oil industries have employed enormous amounts of organic solvents to produce medicines, chemicals, and other goods. In order to recycle these valuable organic solvents, organic solvent nanofiltration (OSN) is crucial. However, choosing the optimal cross-linker is vital for producing membranes with improved performance and chemical resistance. In this study, integrally skinned polybenzimidazole (PBI) flat membranes for OSN were studied through a covalent modification employing α, α′-dibromo-p-xylene (DBX), α, α′-dichloro-p-xylene (DCX) or trimesoyl chloride (TMC), followed by ionic impregnation with 4-sulfocalix [4]arene (SCA4). The nucleophilic-electrophilic reactions between PBI and cross-linkers and the ionic interactions among SCA4, PBI and cross-linkers were investigated and elucidated. Due to the two-fold modifications, the resultant PBI membranes show enhanced molecular sieving capabilities and chemical stability. Especially, the membranes modified with DBX and DCX, and then SCA4 infiltration demonstrate a wide range of stability in harsh organic solvents such as n-methyl-2-pyrrolidone (NMP) and dimethyl acetamide (DMAc). They also possess impressive rejections against low molecular weight (Mw) dyes, reconfirming their superiority in terms of structural and chemical stability to PBI for practical OSN uses. However, the dye rejection is still influenced by the physical characteristics of the solvents and dyes as well as the interactions among the solute, solvent, and membrane. This work may provide a workable plan to design membranes with precise molecular sieving capabilities for OSN. [Display omitted] • The prepared PBI membranes were covalently crosslinked and infiltrated with SCA4. • The developed membranes were characterized and the modifications were confirmed. • The developed membranes show structural integrity and chemical stability for OSN. • The double modifications greatly improve the membrane performance for OSN. • Crosslinkers' impact on membrane resistance in organic solvents was assessed. [ABSTRACT FROM AUTHOR]