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The SUZ-4 zeolite membrane was prepared on the hollow fiber ceramic membrane via the secondary growth method modified by the dynamic hydrothermal process. The surface morphology and pervaporation (PV) performance of zeolite membranes fabricated by dynamic and static hydrothermal processes were studied. The surface of the zeolite membrane prepared by the dynamic hydrothermal process was covered with rod-shaped crystals, while the static one was full of crystal clusters fabricated by small-sized crystals. Besides, the separation factor of the SUZ-4 zeolite membrane made via dynamic hydrothermal method for separating 10 wt% methanol (MeOH)/methyl methacrylate (MMA) mixture at 50 °C exceed 10000 with a flux of 3.83 kg·m−2·h−1, which was better than the static one and showed excellent long-term stability. This work provided the important assistance for the preparation of SUZ-4 zeolite membranes in the separation of MeOH/MMA and MeOH/dimethyl carbonate (DMC) organic mixtures and demonstrated the great potential of dynamic process in promoting the membrane properties. SUZ-4 zeolite membrane with rod-shaped crystals on the surface was obtained by dynamic hydrothermal crystallization. Meanwhile, the SUZ-4 zeolite membrane fabricated by dynamic crystallization exhibited excellent pervaporation performance for separating the methanol and methyl methacrylate mixtures. [Display omitted] • SUZ-4 zeolite membranes were successfully fabricated on the α-Al 2 O 3 hollow fiber ceramic membrane. • The zeolite membranes with rod-shaped crystals on the surface were acquired by the optimization of dynamic crystallization. • These membranes exhibited excellent pervaporation performance on separating the methanol and methyl methacrylate mixtures. [ABSTRACT FROM AUTHOR]

The SUZ-4 zeolite membrane was prepared on the hollow fiber ceramic membrane via the secondary growth method modified by the dynamic hydrothermal process. The surface morphology and pervaporation (PV) performance of zeolite membranes fabricated by dynamic and static hydrothermal processes were studied. The surface of the zeolite membrane prepared by the dynamic hydrothermal process was covered with rod-shaped crystals, while the static one was full of crystal clusters fabricated by small-sized crystals. Besides, the separation factor of the SUZ-4 zeolite membrane made via dynamic hydrothermal method for separating 10 wt% methanol (MeOH)/methyl methacrylate (MMA) mixture at 50 °C exceed 10000 with a flux of 3.83 kg·m−2·h−1, which was better than the static one and showed excellent long-term stability. This work provided the important assistance for the preparation of SUZ-4 zeolite membranes in the separation of MeOH/MMA and MeOH/dimethyl carbonate (DMC) organic mixtures and demonstrated the great potential of dynamic process in promoting the membrane properties. SUZ-4 zeolite membrane with rod-shaped crystals on the surface was obtained by dynamic hydrothermal crystallization. Meanwhile, the SUZ-4 zeolite membrane fabricated by dynamic crystallization exhibited excellent pervaporation performance for separating the methanol and methyl methacrylate mixtures. [Display omitted] • SUZ-4 zeolite membranes were successfully fabricated on the α-Al 2 O 3 hollow fiber ceramic membrane. • The zeolite membranes with rod-shaped crystals on the surface were acquired by the optimization of dynamic crystallization. • These membranes exhibited excellent pervaporation performance on separating the methanol and methyl methacrylate mixtures. [ABSTRACT FROM AUTHOR]

Surface modification is an efficient post-treatment method to optimize the properties of nanofiltration (NF) membranes. Here, we report a facile surface modification strategy coupling with heat curing for grafting monoethanolamine (MEA), a monomer containing both a primary amine and a primary alcohol group, onto a nascent polyamide NF membrane. With grafting 0.5 wt% MEA at 50 °C, the pure water permeability of the polyamide NF membranes was improved from 7.9 to 19.5 L m−2 h−1 bar−1 due to their enhanced physicochemical property, such as superior hydrophilicity, rough surface morphology, and enlarged membrane pores. Meanwhile, the rejection of Na 2 SO 4 remained above 97.5%. More importantly, the optimal membrane modified with 0.5 wt% MEA exhibited a high Na 2 SO 4 rejection of 99.1% and a negative NaCl rejection of −20.1% when treating a mixed salt solution containing 2 g/L Na 2 SO 4 and 2 g/L NaCl. Our study provides a novel insight for the fabrication of high permselectivity NF membranes via surface modification. Image 1 • Surface grafting was creatively coupled with heat curing in water. • Monoethanolamine molecule was successfully grafted onto the nascent membrane, rendering a better hydrophilic nanofiltration membrane. • The modified membrane exhibited enhanced pure water permeability of 19.5 L m−2 h−1 bar−1. • The modified membrane owned superior Cl−/SO 4 2− selectivity. [ABSTRACT FROM AUTHOR]

In this study, we utilized the NaOH solution as a heat-treating medium to replace the conventional oven-heating process after interfacial polymerization for the RO membrane fabrication. XPS result confirmed that the nascent RO membrane possessed a gradient cross-linking density along the polyamide layer depth, which is relatively loose on top and dense facing the substrate. The top loose polyamide could be exfoliated under NaOH treatment. The TFC membrane treated in a 1.5 mol L-1 NaOH solution exhibited a pure water flux nearly 3 times higher than that heat-treated in a water bath and also maintained a high NaCl rejection. In consideration of the practical operation process, membrane stability was evaluated, and the results showed that the membrane heat-treated by 1.5 mol L-1 NaOH solution possessed good long-term and pH stability. Thus, the facile heat-treating strategy provides a new path for fabricating high flux TFC-RO membranes. • Novel heat-treating medium of NaOH solution was utilized to fabricate the novel RO membrane. • The top loose layer of the nascent polyamide membrane could be exfoliated under NaOH treatment. • The modified heat-treating strategy showed great superiority over traditional oven-heating process. [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]

[Display omitted] • TFN(O) membrane exhibits a high flux of 30.4 L∙m−2∙h−1∙bar−1 with 96% rejection for TCE. • The molecular orientation of n-hexane is affected by UiO-66. • The asymmetric distribution of UiO-66 in PA layer has been studied. • The tandem model of dissolution and diffusion in NF is applied to the MD simulation. Chlorinated hydrocarbons (CHC) are highly toxic to human health and the ecological environment. In this study, thin-film nanocomposite (TFN) membranes doping with UiO-66 were prepared and applied to the CHC removal in groundwater. TFN membranes with UiO-66 asymmetrically distributed in the polyamide (PA) layer were prepared by incorporating UiO-66 in the aqueous phase and the organic phase, respectively. Molecular dynamics (MD) simulation was applied to do further mechanism research. The water boundary layer surrounding UiO-66 induces a wrinkled phase interface when UiO-66 is dispersed in the aqueous phase. Also, the dissolution-diffusion model was used for investigating nanofiltration (NF) process. Water molecules show a faster dissolution rate and a higher dissolution equilibrium on the UiO-66 surface. UiO-66 exhibits twice the water number density relative to the PA due to super-hydrophilicity, which provides a greater driving force for the mass transfer of water. In addition, the diffusion coefficient of water in the UiO-66 pore is about 1.5 times that in PA. As a result, TFN(O) membrane exhibits a high pure water flux of 30.4 L∙m−2∙h−1∙bar−1 with the trichloroethylene (TCE) and trichlorobenzene (TCB) rejection above 96%. This work provides a solution for CHC removal of groundwater and a mechanistic explanation for the interfacial polymerization (IP) and separation process of doped nanoparticles. [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]