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[Display omitted] • TFC-PA NF membrane with in-situ formed cellulose nanofibers as interlayer is prepared via interfacial polymerization. • The membrane exhibits a pure water permeance up to 35.7 Lm−2 h−1 bar−1 and a high Na 2 SO 4 rejection >97%. • The membrane shows a high stability to applied pressure and long filtration time. • The membrane shows an obvious improvement of antifouling performance. Improving the water permeance of polyamide nanofiltration (NF) membranes without the simultaneous loss of rejection is highly desired but remains a challenge. In this work, we prepared an ultrapermeable polyamide NF membrane containing an in-situ -formed cellulose nanofibre (CN) interconnected network film between a polyamide active layer and ultrafiltration (UF) membrane support through direct addition of the CN to a piperazine aqueous solution for interfacial polymerization. Such in-situ -formed CN interlayer with high porosity can provide a large number of channels for water transport. Compared with the polyamide active layer directly supported by the UF support, the polyamide active layer supported by the CN interlayer can contribute a more effective area for water permeation. Consequently, the polyamide NF membrane exhibited a pure water permeance up to 35.7 L m−2 h−1 bar−1 while maintaining salt rejection to Na 2 SO 4 of >97%. This permeance is 2.5 times greater than that of the membrane without the CN interlayer. [ABSTRACT FROM AUTHOR]

Regulating the monomer diffusion during interfacial polymerization (IP) process is the key for tailoring the pore structure and desalination performance of thin‐film composite polyamide nanofiltration (NF) membrane. Recently a surfactant‐assembly strategy to regulate IP process and NF membranes with sub‐Å separation precision is proposed. However, little is known for the role of the molecular structure of surfactant on IP process and membrane performance. In this work, five sulfate surfactants with different length of alkyl chains are used to construct surfactant monolayer assembly at the water/hexane interface to regulate IP process. The results show that for the sulfate surfactants, the longer the alkyl chain, the more uniform the pore size distribution of polyamide active layer is and the higher the ion separation selectivity of NF membrane is. Among them, the NF membrane prepared from sodium n‐hexadecyl sulfate (SHS) exhibits the highest separation performance with the rejection of Na2SO4, MgSO4, MgCl2, and CaCl2 up to 99.39%, 99.12%, 98.09%, and 97.38%, respectively. Overall, this study further confirms the regulatory role of surfactant‐assembled monolayer during IP process and provides important insights into how the polyamide structure and the resulting NF membranes are influenced by the alkyl chain length of the surfactants. [ABSTRACT FROM AUTHOR]

Designing a nanofiltration (NF) membrane with distinguished high permeability and ion selectivity is attractive for handling hypersaline wastewater. In this work, we used zwitterionic nanogels (ZNGs) as aqueous additives to prepare NF membranes by interfacial polymerization (IP), and comprehensively investigated the chemical composition of the nanogels on the performance of NF membranes. The outcome of characterizations demonstrated that the nanogels mainly exist as an interlayer between the polyethersulfone (PES) substrate and polyamide (PA) layer, which elevated the hydrophilicity and electronegativity of the membrane surface. In addition, due to the stronger steric hindrance, electrostatic interaction and interlayer-promoted gutter effect, the optimized NF membrane prepared with the addition of 0.015 wt% amine functionalized PSB (SBMA-AH) in aqueous solution exhibited an exceptional water permeability of 20.6 L m−2 h−1 bar−1 and high Na 2 SO 4 rejection of up to 99.5 %, as well as high selectivity of 160.1 for separating Cl−/SO 4 2−. The membrane also displayed superior performance stability under different salt concentrations and pressures. The outstanding desalination performance of the as-prepared NF membrane enables it a promising candidate for hypersaline wastewater treatment. [Display omitted] • A nanofiltration membrane with enhanced perm-selectivity performance is prepared. • The effect of adding zwitterionic nanogels on membrane performance is demonstrated. • The nanogels act as an interlayer after interfacial polymerization is proposed. [ABSTRACT FROM AUTHOR]

Designing and preparing nanofiltration (NF) membrane with distinguished property of acidic tolerance is attractive for handling acidic saline wastewater. In this work, we used a new monomer of 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoro-propane (bisAPAF) to prepare NF membrane by interfacial polymerization for removing dyes from acidic saline solution. Interestingly, the resulted NF membrane derived from bisAPAF and 1,3,5-trimesyol chloride (TMC) exhibits an exceptional structure stability under strong acid condition. Specifically, after exposed to H 2 SO 4 aqueous solution with concentration of 20% (w/v) for 720 h, the NF maintains a Na 2 SO 4 rejection of ∼87% , showing little change as compared with the membrane without acidic treatment. In addition, the membrane shows a high selectivity for differentiating Direct Red 23/NaCl or Congo Red/NaCl in the pH range of 2–9, the rejection of dyes maintains at higher than 98% while the NaCl rejection is lower that ∼10%. The outstanding acid tolerance property of NF membrane makes it a great promise candidate for acid wastewater remediation. [Display omitted] • A Fully aromatic polyamide TFC NF membrane is fabricated by interfacial polymerization. • The membrane exhibits extremely structure stability in strong acid. • The membrane shows a long-term stability of separation performance in strong acid for 720 h. • The membrane possesses a high selectivity of dye/NaCl in the pH range of 2–9. [ABSTRACT FROM AUTHOR]

[Display omitted] • A GO/PB-modified NF membrane was fabricated to remove radionuclides Cs+ and Sr2+. • PEG is conducive to disperse PB in membrane casting solution. • A conceptual model of the effect of substrate on the polyamide layer was proposed. • The modified membrane can be efficiently regenerated using KCl solution. • Cs+ and Sr2+ can be removed by steric effect, Donnan effect and two-step adsorption. In this study, a novel modified nanofiltration (NF) membrane was fabricated to treat radionuclide-contaminated water by incorporation of Prussian blue (PB), graphene oxide (GO) and polyethylene glycol (PEG) into polysulfone (PSf) substrate. In this work, PB provided a large number of adsorption sites for the membrane, GO improved the Donnan effect of the polyamide (PA) layer by enhancing the negative charge, and PEG promoted the uniform dispersion of PB through interparticle electrostatic interaction and steric hindrance while increasing the adsorption sites on the surface of channels in the substrate by adjusting the pore structure. A conceptual model for the role of substrate in interfacial polymerization was then proposed. The modified membrane achieved efficient rejection of cesium (Cs+, 99.5%) and strontium (Sr2+, 97.5%). Its Cs+ rejection rate still remained high (about 96%) even in the treatment of natural surface water containing various inorganic salts and organic matters. What's more, the modified membrane exhibited excellent stability in both strong acid solutions and long-term operation. Then, potassium chloride (KCl) solution was applied to regenerate the modified membrane, which achieved high generation rate as compared to traditional acid regenerants. The excellent filtration performance inferred that the novel GO/PB-modified NF membrane holds great application potential for the application of simultaneous removal of radioactive Cs+ and Sr2+ from contaminated water. [ABSTRACT FROM AUTHOR]

Fabricating membranes with homogenous pore size at sub-nanometer scale is highly demanded for precise separation but remains a challenge. Herein, we propose a new strategy for preparing polyamide (PA) nanofiltration membranes with high solute-solute selectivity via a pre-diffusion interfacial polymerization (PDIP) process. The enrichment of amine monomers on the organic phase side of the oil-water interface facilitates a stoichiometric interfacial polymerization reaction with acyl chloride and endows the PA active layer more uniform pores with sub-Angstrom separation precision. The nanofiltration membrane prepared by PDIP strategy has lower surface roughness and higher degree of polymerization reaction inside the PA active layer compared with the membrane prepared by the traditional method. The pre-diffusion process enables PA nanofiltration membranes to have a 99.7% rejection rate of Na 2 SO 4 and 98.7% of MgCl 2 with no loss of flux while the rejection of that is 96.7% and 62.4% for traditional IP. Most importantly, the membrane exhibits fairly high mono/divalent salt selectivity of both cations and anions (e.g. 246 for NaCl/Na 2 SO 4 and 51 for NaCl/MgCl 2), which is one of the highest mono/divalent salt selectivity among all the reported polymer membranes. The PDIP process with improved ion selectivity is expected to change the traditional manufacturing mode of PA thin film composite (TFC) membranes, including nanofiltration and reverse osmosis membranes those are the most important members in the family of filtration membranes for water purification. [Display omitted] • Polyamide nanofiltration membrane with homogeneous pores is prepared via pre-diffusion interfacial polymerization. • The membrane exhibits high salt rejection and mono/divalent salt selectivity with flux no loss compared to conventional nanofiltration membrane. • The nanofiltration membrane possesses the potential of precise separation at sub-Angstrom level. • Minimal alteration of the established techniques for conventional membranes makes it promising for mass production. [ABSTRACT FROM AUTHOR]

Membranes with excellent water permeance and high dye removal efficiency are highly desired for textile industry wastewater treatment. However, the high acidity and salinity in such wastewater impose great challenges in dye removal efficiency for conventional polyamide-based membranes. This study presents a type of acid-tolerant polyarylate (PAR) nanofiltration (NF) membrane that tackles such challenges. The PAR active layer is produced via interfacial polymerization using 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) and isophthaloyl dichloride (IPC) as monomers, and formed on top of a single-walled carbon nanotube (SWCNT) nanofilm. The supporting SWCNT layer contributes to the ultrathin thickness of the PAR active layer and the extremely high membrane permeating flux of ~210 L m−2 h−1 bar−1, while the inclusion of TTSBI monomer grants the PAR active layer surface negatively charged that makes a high dye rejection of >99% at a wide range of feed solution pH and salinity possible. Furthermore, a high selectivity for dye and NaCl was observed with a stable NaCl retention of ~10%, when the membrane is tested at a pH ranging from 2 to 9 and feed NaCl concentration ranging from 1000 to 5000 ppm. The PAR NF membrane is therefore a promising tool for the highly efficient treatment of acidic and high salinity textile dye wastewaters. • An acid-tolerant PAR NF membrane is prepared via TTSBI-based interfacial polymerization. • The membrane exhibits extremely high permeating flux and high rejection to dyes. • The membrane possesses high selectivity for dye/NaCl fractionation. • The membrane shows long-term stability to acidic and high salinity feed solutions. [ABSTRACT FROM AUTHOR]

In this work, ultrasmall metal-organic frameworks (MOFs) nanoparticles, UIO-66-NH 2 nanoparticles were synthesized and embedded in an ultrathin polyamide (PA) active layer via the interfacial polymerization reaction on a polydopamine-wrapped single-walled carbon nanotube film. A thin-film nanocomposite nanofiltration (TFN NF) membrane with a PA/UIO-66-NH 2 active layer as thin as 20 ± 3 nm was thus fabricated. The loading mass of the nanoparticles in the TFN NF membrane could be tuned by controlling the nanoparticles concentration in aqueous phase. Benefiting from the ultrathin thickness of active layer and the high loading mass of the MOFs nanoparticles, water permeability up to 46 L m−2 h−1 bar−1 along with a Na 2 SO 4 rejection of 97.1% was achieved, which is 53% increase of the TFC NF membrane without the addition of UIO-66-NH 2 nanoparticles. Our membrane owns the thinnest active layer in the category of TFN NF membranes reported so far and exhibits outstanding desalination performance. Image 1 • A TFN NF membrane with an ultrathin PA/UIO-66-NH 2 active layer of 20 ± 3 nm was fabricated. • The nanoparticles are uniformly embedded in the ultrathin active layer. • The membrane exhibits a high water permeability up to 46 L m−2 h−1 bar−1 along with a high Na 2 SO 4 rejection of 97.1%. • The membrane performance outperforms all of the other TFN NF membranes reported previously. [ABSTRACT FROM AUTHOR]