Asymmetric polyamide nanofilm with coordinated charge and nanopore, tuned by azlactone-based monomer to facilitate ion separation

Self-assembled dendrimer polyamide nanofilms with enhanced effective pore area for ion separation

Membrane technology using well-defined pore structure can achieve high ion purity and recovery. However, fine-tuning the inner pore structure of the separation nanofilm to be uniform and enhance the effective pore area is still challenging. Here, we report dendrimers with different peripheral groups that preferentially self-assemble in aqueous-phase amine solution to facilitate the formation of polyamide nanofilms with a well-defined effective pore range and uniform pore structure. The high permeabilities are maintained by forming asymmetric hollow nanostripe nanofilms, and their well-designed ion effective separation pore ranges show an enhancement, rationalized by molecular simulation. The self-assembled dendrimer polyamide membrane provides Cl-/SO42- selectivity more than 17 times that of its pristine polyamide counterparts, increasing from 167.9 to 2883.0. Furthermore, the designed membranes achieve higher Li purity and Li recovery compared to current state-of-the-art membranes. Such an approach provides a scalable strategy to fine-tune subnanometre structures in ion separation nanofilms.

Quantitatively Unveiling the Structure-Activity Relationship of Polyamide Nanofiltration Membranes with Complex Structures

Nanofiltration polyamide (NF PA) membranes are widely used in seawater desalination and wastewater treatment due to their excellent permeability. The structure-activity relationship of PA membranes has attracted extensive attention in decades. In this work, NF PA membranes with planar structure, nodular structure, and peak-valley structure were constructed, and the pure water permeance was calculated by nonequilibrium molecular dynamics simulation to quantitatively investigate the structure-activity relationship between the microstructure and water permeance. Results showed that the peak-valley structure had the highest effective utilization rate of the membrane surface, which had the highest number of water molecules that passed through membranes per unit cross-sectional area (7.09). Furthermore, with the increase of the specific surface area ratio, the water permeance of the NF PA with peak-valley increased at a rate about 2.5 times than that of the planar NF PA. Therefore, some molecular scale insights were supplied about the structure-activity relationship of NF PA membranes, which is helpful for the fabrication of high-performance NF PA membranes.