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A trade‐off behavior is noteworthy between protein rejection and pure water flux (PWF) for ultrafiltration membranes; it is recommendable to increase flux without reducing selectivity. The poly (meta‐phenylene isophthalamide) (PMIA) ultrafiltration membrane was modified via incorporating 1,3,5‐benzene tricarboxylic chloride (TMC) to optimize the performance for the first time. Molecular dynamics (MD) simulation was applied to probe the mechanism of the effects of the concentrations of cosolvent LiCl and addition TMC on the dissolving process. It was turned out that a suitable concentration of TMC in the dope solution markedly enhanced the PWF (from 276.22 to 566.20 m−2 h−1 bar−1) with an increasing bovine serum albumin rejection (from 92.05% to 94.64%). Besides, the optimized membrane also possesses excellent anti‐fouling and mechanical performance. These improvements can be due to the crosslinking between PMIA and TMC and enlarged average pore diameter. This work broadens the application of PMIA and TMC in ultrafiltration and provides a novel methodology for PMIA modification. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) membranes with both high permeability and salt rejection are in dire need for water treatment. Generally, heat treatment is an essential step for fabricating polyamide NF membranes. Conventional heat treatment in an oven causes membrane pore shrinkage and over cross-linking, which often leads to a severe loss of permeation performance. Herein, we report a single-step method by heat-treating membranes in non-neutral solutions to avoid pore shrinkage and generate graded hydrolysis in membrane selective layer. As confirmed by the XPS result, the polyamide NF membrane fabricated via controlled hydrolysis possesses a gradient cross-linking degree vertically along the membrane surface. This optimal polyamide NF membrane had a superior pure water permeability (PWP) of 27.5 L m−2 h−1 bar−1 and high Na 2 SO 4 rejection of 98.5%. Such controlled hydrolysis approach provides novel strategy for fabricating high performance polyamide membranes. • Heat treatment in water was employed to avoid pore shrink and over cross-linking of the polyamide active layer. • The performance of NF membrane with gradient cross-linked structure can be easily tuned by adjusting the pH value of water. • The optimal membrane owns a superior pure water permeability of 27.5 L m−2 h−1 bar−1 and a high Na 2 SO 4 rejection of 98.5%. [ABSTRACT FROM AUTHOR]

In this study, the impacts of heat curing conditions on the morphology and permeability of polyamide nanofiltration (NF) membranes were comprehensively investigated. The surface chemical composition, morphology, charge property, hydrophilicity and NF performance of the resulting membranes were studied. In order to preserve the instantaneous polyamide layer morphology, freeze drying process was employed after heat curing. Results showed that the surface roughness of the polyamide selective layer increased first and then decreased with curing time. The tunable morphology of polyamide NF membranes can be acquired by adjusting the curing temperature and time. The nascent membrane without heat curing exhibited excellent pure water permeability of 16.7 L m−2 h−1 bar−1 and maintained Na 2 SO 4 rejection of 97.4%. Increasing the curing time, the permeability of the NF membranes was greatly diminished. This work provided novel viewpoint about the effects of heat curing on morphology and permeability for high-performance polyamide NF membrane. • Interfacial polymerization is terminated by liquid nitrogen to preserve the instantaneous polyamide layer morphology. • Polyamide layer roughness increases first and then decreases as a function of the heat curing time. • The nascent membrane exhibited excellent pure water permeability of 16.7 L m−2 h−1 bar−1 and Na 2 SO 4 rejection of 97.4%. [ABSTRACT FROM AUTHOR]

• A novel TFC NF membrane was fabricated by incorporation of β-CD into polyamide backbone. • The effect of β-CD on the NF membrane performance was studied thoroughly. • Such NF membrane showed a high permselectivity performance. Based on the Freeman theory, tailoring polymer backbone stiffness can improve membrane performance. Therefore, a rigid monomer—bisphenol F—to enhance the backbone stiffness of polyester/polyamide was utilized to prepare high performance nanofiltration (NF) membranes in the previous work. Here, the three-dimensional (3D) hollow-bowl-structure monomer—beta cyclodextrin (β-CD)—is added into the polyester/polyamide backbone to fabricate a 3D-microstructure NF membrane. With the incorporation of β-CD, the pure water flux (PWF) increases by 68% (up to 152 L m−2 h−1, 0.6 MPa), while the rejection of Na 2 SO 4 remains high (96.8%). Surprisingly, such NF membrane exhibits a very low rejection of NaCl (1.1%) and high rejection of Na 2 SO 4 (up to 95.8%) when dealing with a Na 2 SO 4 /NaCl mixed solution. The fabricated 3D-microstructure NF membrane shows the potential to be applied in the monovalent/divalent anion separation field. [ABSTRACT FROM AUTHOR]