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Owing to their extraordinary thermal, mechanical, optical, and electrical properties, boron nitride nanotubes (BNNTs) have been attracting considerable attention in various scientific fields, making it more promising as a nanomaterial compared to other nanotubes. Recent studies reported that BNNTs exhibit better properties than carbon nanotubes, which have been extensively investigated for most environment-energy applications. Irrespective of its chirality, BNNT is a constant wide-bandgap insulator, exhibiting thermal oxidation resistance, piezoelectric properties, high hydrogen adsorption, ultraviolet luminescence, cytocompatibility, and stability. These unique properties of BNNT render it an exceptional material for separation applications, e.g., membranes. Recent studies reported that water filtration, gas separation, sensing, and battery separator membranes can considerably benefit from these properties. That is, flux, rejection, anti-fouling, sensing, structural, thermal, electrical, and optical properties of membranes can be enhanced by the contribution of BNNTs. Thus far, a majority of studies have focused on molecular simulation. Hence, the requirement of an extensive review has emerged. In this perspective article, advanced properties of BNNTs are analyzed, followed by a discussion on the advantages of these properties for membrane science with an overview of the current literature. We hope to provide insights into BNNT materials and accelerate research for environment-energy applications. [ABSTRACT FROM AUTHOR]

In molecular separation using membranes, enhanced parameters, such as an increased flux and selectivity, are required for efficiency. Additionally, in molecular separation using solvents, solvent resistance is critical in preventing solvent-induced damage. However, most membranes lack resistances to specific harsh solvents, and simultaneously enhancing solvent flux and selectivity performance, which exhibit a trade-off relationship, is challenging. In this study, a high-performance solvent-resistant polybenzimidazole (PBI) membrane is fabricated via chemical crosslinking with divinyl sulfone (DVS). The membrane consists of porous finger-like support and dense skin layers, and the uniform DVS crosslinking of the PBI membrane is confirmed via chemical analysis. The DVS-crosslinked PBI membrane exhibits a superior solvent stability and separation performance, with an ethanol permeance and molecular weight cut-off of 5.88 L m−2 h−1 bar−1 and 483 g mol−1, respectively. These values represent an enhanced permeance and rejection performance compared to those of the pristine membrane. The DVS-crosslinked PBI membrane also displays a long-term stability in mepenzolate bromide separation over 72 h. [Display omitted] • Solvent-resistant and high-performance PBI membranes for enhanced molecular separation are fabricated by DVS crosslinking. • Owing to the well-organized structure and uniform DVS crosslinking, the membrane exhibits improved rejection and stability. • The enhanced performance is investigated based on the surface energy of each solvent and membrane. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) process using a thin-film composite (TFC) membrane is a current leading technology for water desalination. The polyamide permselective layer of the TFC membrane enables salt retention and water permeation, with the ultimate goal of minimizing the permselective layer thickness for maximum energy efficiency. Yet this drive towards reducing the permselective layer thickness is greatly handicapped by the interfacial polymerization (IP) approach used to fabricate TFC membranes. We present layered interfacial polymerization (LIP) as a new paradigm for fabricating TFC membranes with unprecedented nanoscale control in the permselective layer thickness and smoothness, coupled with the advantage of industrial scale manufacturability. Membranes fabricated using LIP demonstrated high NaCl rejection necessary for water desalination, with water permeance ≈ 86% and permselectivity ≈ 450% greater than that of the membranes prepared using conventional IP and comparable water permeance and permselectivity ≈ 17% higher than that of commercial RO membranes. In addition, the unique smooth morphology of the LIP-assembled membrane surface enabled to mitigate the membrane fouling compared to the characteristic rough surface of the conventional IP-assembled membrane. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) is a membrane-based organic solution separation process that has emerged as a viable alternative to energy- and solvent-intensive separation processes. Polymers of intrinsic microporosity (PIMs) are the targets of recent active research on OSN membrane materials because of their unique physicochemical properties, such as solution processability, chemical tunability, robust porosity, and high thermal stability. However, applying PIMs-based membranes in practical OSN applications is still challenging because of their limited organic solvent stability and inevitable decrease in performance. Meanwhile, despite the potential of thin-film composite hollow fiber membranes for OSN, only a few studies have been reported to date. In this study, we fabricated a PIMs-based thin-film composite hollow fiber membrane by dip-coating and improved its organic solvent stability by intermolecular cross-linking. The membrane exhibited pure ethanol permeance of 10.9 LMH/bar and a molecular weight cut-off of 952 g/mol in ethanol. The membrane displayed stable dye rejection performance (>95%) even after immersion in ethanol, acetone, and toluene for seven days. This study demonstrates that intermolecular cross-linking between PIMs polymer chains can improve the organic solvent stability of PIMs-based membranes and provides a desirable strategy to fabricate feasible organic solvent stable PIMs-based thin-film composite hollow fiber membranes for OSN applications. [Display omitted] • An intermolecular cross-linked PIM-1 (XPIM) TFC hollow fiber (HF) membrane was developed for OSN. • The XPIM TFC HF membrane exhibited remarkable organic solvent filtration performance. • The XPIM TFC HF membrane showed stable rejection performance after immersion in organic solvents for seven days. • Intermolecular cross-linking can improve the organic solvent stability of PIMs-based membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Cr(VI)-adsorptive membrane was prepared via IP using an amine-based star polymer. • The membrane rejects Cr(VI) via a combination of adsorption and membrane filtration. • The membrane exhibits higher Cr(VI) rejection (∼99.5%) than a RO membrane at pH < 7. • The membrane exhibits similar Cr(VI) rejection to a RO membrane at pH > 7. • The membrane displays excellent oxidation resistance and regeneration ability. There is a strong demand for materials that can effectively remove highly toxic hexavalent chromium (Cr(VI)) ions from wastewater. Herein, we present a new class of Cr(VI)-adsorptive membranes assembled with a Cr(VI)-adsorptive and cross-linkable star polymer. The poly(acryloyl hydrazide)-branched star polymer (PAH-SP) with numerous amine groups enabled rapid and high-capacity Cr(VI) adsorption and was suitable for assembly into a selective layer via interfacial polymerization (IP). The IP-assembled PAH-SP (PAH-TFC) membrane synergistically rejected Cr(VI) over the entire pH range via a combination of adsorption (under acidic conditions) and membrane filtration (under basic conditions). Furthermore, the PAH-TFC membrane was more resistant to oxidation by acidic Cr(VI) than commercial reverse osmosis (RO) and nanofiltration membranes because of the self-sacrificing effect of its abundant amine groups. Consequently, PAH-TFC exhibited significantly higher Cr(VI) rejection (∼99.5% at pH 3) under acidic conditions than a representative commercial RO membrane (Cr(VI) rejection of ∼55% at pH 3) with similar water permeance, while demonstrating comparable Cr(VI) rejection under basic conditions. Furthermore, PAH-TFC displayed excellent regeneration ability, maintaining its Cr(VI) rejection above the commercial RO level by proper base/acid rinsing. [ABSTRACT FROM AUTHOR]

We report on a new technique that incorporates silver nanoparticles (AgNPs) onto polyamide (PA) thin film composite (TFC) reverse osmosis membranes via arc plasma deposition (APD) to impart antibacterial properties and simultaneously improve membrane performance. APD allows the direct deposition of AgNPs under vacuum dry condition, overcoming the drawbacks of the conventional wet-chemical methods. AgNPs (~7.6 nm in diameter) were uniformly distributed without aggregation throughout the PA selective layer with some partially implanted into the PA matrix. Ag loading could be tuned by simply adjusting the number of APD purse shots. The deposited AgNPs exhibited good leaching stability, presumably due to the strong Ag-PA chemical interaction and partially buried AgNP morphology. The resulting Ag-incorporated TFC (Ag-TFC) membrane showed the strong and long-lasting antibacterial properties for both gram-negative and -positive bacteria. Simultaneously, the Ag-TFC membrane exhibited an enhancement in water flux of approximately 40% without deterioration in NaCl rejection. These performance changes were tentatively attributed to the partial destruction of the PA layer under the high energetic APD condition along with the increased membrane hydrophilicity. Hence, the APD process provides a simple and effective route to modify membranes with functional NPs. [ABSTRACT FROM AUTHOR]

To enable the wide application of nanofiltration (NF) membranes to increase the fresh water supply, the development of new membrane materials and preparation techniques are still highly desired. In this work, thin-film composite (TFC) NF membranes were fabricated via interfacial polymerization (IP) using three different kinds of biomonomers with trimesoyl chloride (TMC) on a polysulfone (PSf) substrate. Biomonomers such as dopamine hydrochloride (PDA), norepinephrine (PNE), and tannic acid (TA) are highly hydrophilic and environmentally friendly. Moreover, these materials can not only strongly adhere to substrates but can also form chemically stable cross-linked networks. The influence of these monomers on the formation of the selective layer was systematically investigated. Furthermore, a series of characterization techniques, including attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), zeta potential measurement, molecular weight cutoff (MWCO), X-ray photoelectron spectroscopy (XPS) and separation performance experiments, were used to study the properties of the TFC NF membranes. Biomonomer-based TFC NF membrane exhibited a higher water permeability of 8.14 L/m2 h bar with a high rejection for divalent ions (Na 2 SO 4) of 93% compared to TFC NF membranes. [Display omitted] • A nanofiltration membrane was developed using three biomonomers as aqueous phase with trimesoyl chloride (TMC). • High performance TFC NF membrane with relatively higher flux with fixed rejection rate (Na 2 SO 4 ~93%) than other membranes. • The reaction chemistries to form the TFC PA layers between three types of biomonomers and TMC were thoroughly investigated. [ABSTRACT FROM AUTHOR]

In this study, we report a facile and straightforward graphene oxide pre-coating method to prepare defect-free, ultrathin film composite ceramic hollow fiber membranes. By coating a graphene oxide (GO) interlayer, the defect-free thin alumina active layer with sub-micrometer thicknesses was successfully coated on highly porous substrates without thick interlayers. The GO interlayer not only prevents the pore-clogging of the substrate by boehmite nanoparticles but also helps the thin and uniform formation of active layers. Since the ultrathin GO interlayer was naturally removed during the calcination process of the active layer over 400 °C, the ceramic thin-film composite (TFC) membranes with controllable active layer thickness and pore size were obtained. Prepared ceramic TFC membranes showed outstanding separation performance, which was 2–8 times higher water flux at the same MWCO, compared to commercial multilayered ceramic ultrafiltration membranes. The results demonstrate the superior separation properties of ceramic TFC membranes, and the potential of cost-effective GO interlayer pre-coating methods for fabricating inorganic based membranes for various molecular separation applications. • Highly permeable ceramic thin film composite membranes were successfully prepared. • Sacrificial graphene oxide interlayer was applied to prevent defects and pore-clogging. • Graphene oxide interlayer was removed during calcination of ceramic active layers. • The separation performances were varied with thickness and pore size of active layers. • 2–8 times higher water fluxes were achieved compared to commercial ceramic membranes. [ABSTRACT FROM AUTHOR]