Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200–35,000 g/mol). This alteration facilitated the formation of a thin polyamide layer on the PSf surface during the interfacial polymerization reaction involving an aqueous solution of piperazine containing 4-aminobenzoic acid and an organic solution of trimesoyl chloride. Attenuated total reflectance-Fourier transform infrared validated the presence of PEG in the membrane support. Scanning electron microscopy and atomic force microscopy illustrated that the thin-film polyamide layer morphology transformed from a rough to a smooth surface. A cross-flow filtration test indicated that a thin-film composite polyamide membrane comprising a PSf support (TFC-PEG20k) with a low surface porosity, small pore size, and suitable hydrophilicity delivered the highest water flux and separation efficiency (J = 81.1 ± 6.4 L·m⁻²·h⁻¹, R_Na2SO4 = 91.1% ± 1.8%, and R_NaCl = 35.7% ± 3.1% at 0.60 MPa). This membrane had a molecular weight cutoff of 292 g/mol and also a high rejection for negatively charged dyes. Therefore, a PSf support exhibiting suitable physicochemical properties endowed a thin-film composite polyamide membrane with high performance.

In the face of serious environmental pollution and water scarcity problems, the membrane separation technique, especially high efficiency, low energy consumption, and environmental friendly nanofiltration, has been quickly developed. Separation membranes with high permeability, good selectivity, and strong antifouling properties are critical for water treatment and green chemical processing. In recent years, researchers have paid more and more attention to the development of high performance nanofiltration membranes containing “ion pairs”. In this review, the effects of “ion pairs” characteristics, such as the super-hydrophilicity, controllable charge character, and antifouling property, on nanofiltration performances are discussed. A systematic survey was carried out on the various approaches and multiple regulation factors in the fabrication of polyelectrolyte complex membranes, zwitterionic membranes, and charged mosaic membranes, respectively. The mass transport behavior and antifouling mechanism of the membranes with “ion pairs” are also discussed. Finally, we present a brief perspective on the future development of advanced nanofiltration membranes with “ion pairs”.

In this work, a novel semi-aromatic polyamide RO membrane was fabricated by using a new self-made dendritic molecule trimesoylamidoamine (TMAAM) as a key functional amine monomer that combined 1,3-diamino-2-propanol (DAP) to react with trimesoyl chloride (TMC) through interfacial polymerization technology. By adjusting the TMAAM concentration and amine-immersion mode, this new TMAAM-based semi-aromatic polyamide RO membrane exhibits simultaneously improved water permeability, antifouling and chlorine-tolerant properties. The introduced TMAAM units in polyamide chains can enhance the TMAAM-based membrane's water flux due to its dendritic structure as well as rich hydrophilic groups, and the DAP–TMAAM–TMC membrane prepared via the new two-step amine-immersion mode has 1.9 times more water flux without loss of salt rejection than the pristine DAP–TMC membrane and also shows higher water flux than the hand-cast conventional aromatic polyamide MPD–TMC membrane, respectively. At the same time, the regularly distributed hydroxyl groups and aliphatic amide bonds in TMAAM units contribute to the improved hydrophilicity and chlorine-tolerant property of the resultant DAP–TMAAM–TMC membrane, respectively. It is also demonstrated that the new two-step amine-immersion mode leads to a much smoother surface which endows the resultant DAP–TMAAM–TMC membrane with a favorable antifouling ability. This research provides us with a promising functional amine monomer and a new membrane formation method to fabricate a high performance RO membrane.

Porous organic polymer (POP) membranes show great promise for the precise separation of organic molecules and salt ions due to their high porosity, tunable pore aperture, and robust porous structure. However, their application is hindered by the poor processability of POPs and complicated and uncontrollable membrane preparation. Herein, we report a nanoparticle-polymer reticulation (NPR) strategy by bridging POP nanoparticles for the fabrication of POP nanochannel membranes with a relatively large area (>700 cm²). A new type of water dispersible and processible triazine porous organic polymer (TPOP) nanoparticles was synthesized via the facile and straightforward Debus–Radziszewski reaction. Chitosan (CS) macromolecules as the bridge tied the self-assembled TPOP nanoparticles into a thin film via in situ chemical cross-linking on a polymeric porous substrate, wherein the resultant film thickness, pore size and separation performance could be conveniently tuned. The NPR strategy enabled the construction of an ultrathin and continuous nanochannel TPOP-CSM membrane, presenting both a high water permeance of ∼130 L m⁻² h⁻¹ bar⁻¹ and dye/salt selectivity of ∼35, which is one order of magnitude higher than that of conventional polymeric nanofiltration membranes. Meanwhile, the membrane exhibited good fouling resistance and antibacterial properties in an aqueous environment. Our strategy may provide a paradigm shift in engineering POP nanomaterials and constructing next-generation advanced separation membranes.

Distinct Mg²⁺ and Li⁺ passage mechanisms in ZIF-8: Mg²⁺via window expansion and Li⁺via window expansion and partial dehydration.