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[Display omitted] • The interfacial polymerization is regulated by the inverse diffusible organic phase additive polypyrrole nanoparticles (PPYN). • The modified reverse osmosis (RO) separation layer features abundant free volume. • The flux of the modified RO membrane increases nearly 3 times compared with the pristine RO membrane without sacrificing separation selectivity. • The modified RO membrane exhibits excellent anti-biofouling property. Highly permeable thin film composite (TFC) reverse osmosis (RO) membranes with abundant free volume are desirable for water treatment. However, the strategy of controlling the microstructure of the separation layer with high free volume rate is still a challenge. In this work, a modified strategy for the preparation of high-performance TFC RO membrane with inverse diffusible polypyrrole nanoparticles (PPYN) as organic phase additive was developed. The combination of PPYN and trimesoyl chloride (TMC) would diffuse backwards from the organic phase into the aqueous phase during the reaction process to disrupt the normal interfacial polymerization (IP) and thus introduce more free volume in the RO membrane due to the nanobubbles from violent reactions. Moreover, the thickness of the modified membrane decreased and the hydrophilicity increased based on the modulation of IP by PPYN, which facilitated the water molecules to transport. The prepared RO-PPYN membranes showed nearly three times the flux compared with the pristine RO membrane without sacrificing separation selectivity. Furthermore, the anti-biofouling property of the modified membrane was also improved. This work successfully demonstrated the potential use of PPYN as an organic filler to enhance the performance of seawater desalination in RO membranes. Our modification strategy provides an efficient and convenient way to prepare novel RO membranes with high permeability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Monomers developed in recent years for preparation of TFC membranes is summarized. • The relationship between monomer structure and membrane properties is established. • The application problems of the IP monomers are summarized. • The outlook for future development of the monomer is also discussed. The thin-film composite (TFC) membranes fabricated by interfacial polymerization (IP) can be applied in the fields of nanofiltration (NF) and reverse osmosis (RO), which has the unparalleled advantages, such as high selectivity and permeability, small capital investment and low energy consumption, thus attracting great research interest in industry and academia field. The performance of TFC membranes is determined by their microstructure and physicochemical properties while IP monomer plays a decisive role regarding both. Over the past few decades, the researchers have paid intensive and sustained efforts to develop new IP monomers. This paper reviews these monomers and the corresponding membranes developed in recent years with the aim of establishing an intrinsic relationship between monomer structure and membrane properties. The excellent performances based on new monomers in enhancing the permeability, selectivity, anti-fouling and chemical stability of NF and RO membranes for liquid treatment are highlighted. Finally, various problems in the monomer development are summarized and the outlook for future development is also discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel polyamide loose NF membrane was prepared from aqueous monomer (piperazine-2-carboxylic acid). • The loose NF membrane formation mechanism was clarified. • The loose NF membrane exhibited high water permeance and outstanding separation selectivity of dye/salt. • The loose NF membrane demonstrated excellent antifouling performance. Dye effluent is regarded as one of the most hazardous industrial effluents. Although loose nanofiltration (NF) membranes have been considered as an effective alternative technique for treating dye effluent, their development is still constrained by subpar permeance, separation efficiency and anti-fouling performance. In this work, a novel loose polyamide (PA) NF membrane was designed employing a conventional interfacial polymerization process using piperazine-2-carboxylic acid (PIP-COOH) and trimesoyl chloride as aqueous and organic phase monomers, respectively. The presence of unique electron-absorbing carboxyl groups on the PIP-COOH monomer not only provided abundant negative charge on the membrane surface, but also greatly reduced the reactivity, diffusion rate and solubility in n-hexane of the aqueous monomer, allowing for the formation of a more relaxed and smoother active layer. The balanced combination of pore size screening and Donnan effect achieved precise separations with high permeability. Moreover, the interaction of the carboxyl groups with the backbone structure increased the free volume of the PA layer and improved permeability significantly. The PIP-COOH/TMC membrane prepared under the optimal conditions exhibited high water permeance of 598.1 L·m−2·h−1·MPa−1, high reactive red rejection (99.3%) and low NaCl rejection (5.4%). Furthermore, the membrane possessed exceptional anti-fouling performance thanks to the ultra-smooth surface with crucial antifouling index flux recovery ratio as high as about 99%, which showed unexpected application possibilities. In conclusion, this study offers a potential novel membrane material for the development and application of loose NF membranes in the treatment of colored effluent. [ABSTRACT FROM AUTHOR]

The regulation of interfacial polymerization (IP) is the critical procedure for the preparation and industrialization of thin film composite (TFC) nanofiltration (NF) membranes. However, the IP control is still a huge challenge based on the extremely rapid reaction rate during the fabrication of the membrane. Herein, a new strategy was developed to modulate the IP process to increase the NF membrane performance. The aldehyde oxidized dextran (ODex) interlayer was deposited on the polysulfone ultrafiltration substrate, and the enamine would form between the secondary amines of aqueous phase monomer piperazine (PIP) and aldehyde groups of the ODex. Based on the by-products of IP, the enamine gradually decomposed reversibly in a hydrogen ion environment and the immobilized PIP was released and continued to react with organic phase monomer trimesoyl chloride (TMC). Accordingly, a thinner and exhibiting nanowire structures separation layer with fewer defects was obtained. The permeance of the optimal NF membrane with 0.7 wt% ODex interlayer deposition concentration could reach up to 208 ± 10.4 Lm−2h−1MPa−1, which was more than 2.5 times permeance of the ordinary NF membrane, and the rejection rate for Na 2 SO 4 could reach 99.3 ± 0.3%. In addition, the mono- and divalent ion selectivity of the modified membrane was also greatly improved (α NaCl/Na2SO4 = 115). This study provides a new idea for the regulation of IP process, thereby suggesting a reasonable proposal for improving the performance of TFC NF membranes. [Display omitted] •The enamine was formed between the secondary amines of piperazine and the aldehyde group on the oxidized dextran interlayer. •The interfacial polymerization procedure was effectively regulated by a reversible enamine reaction. •The effect of enamine reversible reaction on the structure of nanofiltration membrane was discussed in detail. •The performance of modified NF membranes for monovalent/divalent salts selectivity was significantly improved. [ABSTRACT FROM AUTHOR]

Conventional interfacial polymerization (IP) requires excessive amounts of reactive monomers and solvents due to the dip-coating method. Herein, we report a rod-coating assisted IP process to prepare nanofiltration (NF) membranes. The results demonstrate that a perfect PA layer can be fabricated by using low monomer dosages of PIP (0.08 g/m2) and TMC (0.016 g/m2). This can significantly reduce the consumption of monomers and organic solvents, and effectively avoid the waste of hazardous and expensive chemicals. Thanks to the fewer monomer dosages, the prepared NF membranes were much thinner and looser, which significantly improved the membrane permeability. The highest permeance of the rod-coated membranes reached 204.0 L/(m2 h MPa), which was increased by ∼251% compared to the dip-coated NF membrane. More importantly, the rod-coated membranes possessed excellent Na 2 SO 4 rejections (>99.0%) and ultralow NaCl rejections (<14.4%). And the maximum NaCl/Na 2 SO 4 selective efficiency reached 125.7, which was about 7 folds to that of the dip-coated NF membrane. This study suggests that the rod-coating method is highly feasible for the preparation of polyamide NF membranes with high performance. It is reasonable to expect that this rod-coating assisted IP process offers a new approach to fabricating NF membranes. [Display omitted] • High performance PA-NF membranes fabricated by rod-coated assisted IP process. • The rod-coating method significantly reduce the consumption of the monomers. • The rod-coated membrane possesses an excellent permeate flux of 204.0 L/(m2 h MPa). [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanofiltration membranes with strong negative charge were prepared by a new aqueous monomer 2,4,6-trimethyl-3,5-diaminobenzenesulfonamide (TMDBSA) through the traditional interfacial polymerization process without any post-treatment. • The membrane has high water permeability (19.6 L m−2 h−1 bar−1) and >98.3% methyl blue rejection. • It owns separation stability for the removal of MB in a harsh acid environment. • It has excellent antifouling performance and long-term stability during the filtration tests. • It demonstrates great practical application potential for treating acidic anionic dyes solutions. Nanofiltration (NF) membranes with negative surface charge are of critical significance for the efficient removal of anionic dyes from wastewater. In this work, a novel negatively charged NF membrane was prepared from a new sulfonamide monomer, 2,4,6-trimethyl-3,5-diaminobenzenesulfonamide (TMDBSA) and trimesoyl chloride (TMC) via interfacial polymerization. The unique diamino-sulfonamide structure of TMDBSA would be conducive to the formation of a poly (amide-sulfonamide) (PASA) layer with enhanced negative charge while maintaining the appropriate degree of crosslinking. The TMDBSA-TMC membrane prepared at optimized condition exhibits both high water permeability (19.6 L m−2h−1 bar−1) and superior rejections of anionic dyes with different molecular weights (e.g. 98.3% rejection for methyl blue), reveals that Donnan exclusion dominates the rejection mechanism. More importantly, benefiting from the strong negatively charged surface and PASA structure, the TMDBSA-TMC membrane shows separation stability for the removal of methyl blue in a broad pH range, even under a harsh acid environment. Meanwhile, the membrane has excellent antifouling performance and long-term stability during the filtration tests. The newly developed negatively charged NF membrane demonstrates great practical application potential for the removal of anionic dyes with small molecular weights. [ABSTRACT FROM AUTHOR]