Acid/alkali durable loose nanofiltration membrane with self-limited polyester selective layer for efficient separation of salts from dyes

The diversity of industrial wastewater has put forward increasing demand, such as acid/alkali resistance and effective separation of salts from dyes, for loose nanofiltration (LNF) membranes, promoting modification and functionalization of selective layer. However, traditional polyamide or polyester selective layer of LNF membranes are constructed by connection between functional group in monomers, showing less potential for further modification and functionalization. In this regard, we introduced interfacial radical polymerization, through which the selective layer was constructed by C C bond, leaving functional groups for modification and functionalization. Moreover, trifunctional cross-linker was introduced to enhance the self-limiting growth of selective layer. The thickness of selective layer formed through interfacial radical polymerization was ∼110 nm, which was almost the same as commercial polyamide or polyester selective layer. Consequently, the as formed selective layer exhibited outstanding permeability of ∼102 LMH/bar and excellent selective factor up to 646 of Na 2 SO 4 over CR. In addition to strong resistance to acid/base in the pH range between 1 and 14, the LNF membrane demonstrated great potential for directly treating industrial dyeing wastewater. After a two-stage filtration, the removal rates of color, turbidity, and COD were 96.6 %, 99.9 %, and 92.3 %, respectively, and the recovery of membrane performance could reach 99 % even after six filtration cycles. The application of interfacial radical polymerization in membrane fabrication endows diverse modification and functionalization of membranes, which paves a new way for general application of membrane process in treating industrial wastewater.