Cross-linked nanosheets constructed as selective layers for the preparation of polyphenylene sulfide loose nanofiltration membranes for efficient separation of dyes and salts

Due to their high porosity, many scholars have utilized two-dimensional (2D) materials for molecular separation. However, they need stability by relying only on the interactions between the 2D materials. Meanwhile, to promote the application of membrane separation technology in salt-containing printing and dyeing wastewater treatment, here we prepared a lamellar selective-layer crosslinked Cu-TCPP loose nanofiltration membrane. This membrane consists of a polyphenylene sulfide membrane as a substrate, which is loaded by tannic acid-modified and auxiliary-dispersed Cu-TCPP and stabilized by crosslinking by TMC. The crosslinking structure of polyester plays a critical role in the crosslinking and stabilization of the interlayer structure of two-dimensional nanosheets, and the retention rate of RhB dye can reach 99.8 %, with a lower retention rate for monovalent salt NaCl (<10 %) and divalent salt (<20 %). The original pore structure is also retained, and the maximum permeation flux could reach 27 L m −2  h −1  bar −1 . It possesses a high separation factor (α > 380) for NaCl/RhB mixed solution. In addition, the presence of a crosslinked structure gives the membrane better acid resistance, and it still has high selectivity for 16 h of continuous operation, achieving >98 % for methylene blue dye. This study provides a novel strategy to address nanosheet stability with potential applications in efficient salt/dye separation.