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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]

Thin-film nanocomposite (TFN) membrane based on polyamide (PA) chemistry was widely applied for water purification and desalination process due to the improved water permeance. It remains a great challenge to significantly enhance rejection because of the non-selective defects caused by the aggregation of nanomaterials in the PA layer. Novel interlayer-based TFN (iTFN) membrane containing nanomaterial interlayer between the porous substrate and PA layer is the promising candidate to improve PA integrity and thus overcome the ubiquitous trade-off between permeability and selectivity. The nanomaterial interlayer not only promotes the subsequent interfacial polymerization (IP) but also provides improved pathways for water transport, which leads to simultaneous improvement in membrane permeability and selectivity. This review systematically categorizes nanomaterial interlayers into three types according to construction methods, namely, direct deposition, in situ growth and functional group-anchored in situ assembly (FAISA). The mechanism of interlayer modulating IP process and PA structure, as well as the effects on water transport, are comprehensively analyzed. Encouraging results reveal that using MOFs interlayer prepared by FAISA is the most promising way to break the trade-off in manufacturing reverse osmosis membranes. Finally, challenges and future efforts are presented for advancing iTFN membranes. [Display omitted] • Recent advances in the porous nanomaterial interlayer enhanced iTFN membranes have been summarized. • Nanomaterial interlayers are categorized into three types according to the construction methods. • The effects of nanomaterial interlayer on interfacial polymerization and separation performance have been explored. • Functional group-anchored in situ assembly MOFs interlayer is a promising candidate to overcome the trade-off between membrane permeability and selectivity. • Challenges and future efforts of promoting nanomaterial interlayer-based iTFN membranes are proposed. [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]

In recent years, the global demand for lithium resources has grown substantially due to the rapid development of the new energy industry. The nanofiltration (NF) technique is a feasible method to extract lithium from salt-lake brine, and the high Mg2+/Li+ separation selectivity of the NF membrane is the crucial factor in the NF separation process. In this work, the polyamide (PA) layer was prepared on the polyphenol/PEI interlayer-modified polysulfone (PSF) substrate to endow the NF membrane with decreased pore size and weakened electronegativity. Enhanced steric hindrance effect and reduced electrostatic attraction between Mg2+ and PA layer increased the Mg2+ rejection, thereby improving the Mg2+/Li+ separation factor of the NF membrane. Furthermore, the positively charged polyphenol/PEI interlayer hindered the permeation of Mg2+ through the Donnan effect, further enhancing the Mg2+/Li + separation factor. A separation factor up to 50.7 for Mg2+/Li+ was achieved by extracting lithium from simulated brine using the obtained NF membrane. In addition, the NF membrane exhibited a permeability of 18.6 L m−2 h−1·bar−1 and excellent long-term stability, which greatly improved the Mg2+/Li+ separation efficiency and reduced energy consumption. Therefore, this work provides a simple strategy for preparing NF membranes with high Mg2+/Li+ separation factor and permeability. [Display omitted] • Dual-electric layer NF membranes with positively charged interlayer and negatively charged separation layer. • The high Mg2+/Li+ separation selectivity is attributed to the synergy between the steric hindrance effect and Donnan exclusion. • The Mg2+/Li+ selectivity of NF membranes can be adjusted by changing the preparation conditions of the interlayer. • Permeability - selectivity trade-off was well addressed. [ABSTRACT FROM AUTHOR]