Organic permeation through an ion exchange membrane is an urgent problem to be solved in electrodialysis (ED) processes on treating industrial wastewaters. However, how the salt, water, and organic compounds co-transport in an ED stack is still unclear. To reveal this, a series of cation exchange membranes (CEMs) were prepared in this work by using sulfonated polysulfone with different sulfonation degrees as a tool to “adjust” membrane water uptake and “control” water migration. The results showed that CEMs with a high sulfonation degree had positive correlation with desalination performance. Salt migration led to organic matter migration, while the presence of small molecule organics reduced the water flux and elevated the sodium flux, which favored the ED process. It was proven that the membrane sulfonation degree could be an important tool to adjust water permeation, and as a consequence, to improve the separation performance of salt from organic compounds in wastewater.
Thin-film composite (TFC) membranes show exceptional permeation properties of key importance for many separations. However, their design and development need ultrathin and defect-free nanofilms as the active layer to alleviate the bottleneck of permeation–rejection trade-off. Here, a 25 nm thick film is fabricated on a porous support by introducing polydopamine (PDA) as an adsorption layer, imparting a unique adsorption-assisted interfacial polymerization (IP) strategy. The PDA layer efficiently captures and enriches amine monomers even from ultradilute solution toward uniform stacking on the support, thus generating ultrathin and defect-free films after polymerization. This is superior to the defective one from conventional IP. Such an active layer features ultrafast permeation for organics, favorable solute rejection, and excellent operation stability. Particularly, the acetone permeance of this new TFC membrane reaches 96.3 L m–2 h–1 bar–1, which exceeds that from conventional IP by more than 10 times, ranking among one of the highest performances reported to date. More significantly, the pernicious permeation–rejection trade-off of the TFC membrane is thus alleviated. Besides, this strategy is facile, versatile, and easy to scale-up, giving controllable physical and chemical structures to the active layer. This study may pave a way to well-design highly efficient film materials for various transport and separation applications.
危险品化学品经营许可证（带存储）