Structure-function relationship for functional films with constructed graded channels in dye/salt separation and fouling resistance

The structural assembly of polypyrrole particle stacking, combined with polydopamine space-filling, forms composite film with a network of interconnected fluid channels. The composite films achieve high water flus, separation efficiency and ratio of organic dyes/inorganic salts (flux: >600 L m⁻² h⁻¹ bar⁻¹; dye rejection: ~100 %; salt rejection: <5 %). Simulation using different dye fouling models show that the dye only interacts at the surface, and hardly affects internal pores of the film throughout the filtration process. Owing to the patterned surface structure as constructed by microsphere arrangement and inter-structure adaptation assembly, the functional film has excellent contamination tolerance and rinsing regeneration for macromolecular pollutants. The results of computational fluid dynamics simulations further indicate that the high shear stress above the microspheres with vortex flow in the interstitial space has a positive effect on reducing contaminant deposition. In addition to the separation property, the composite film shows good structural stability and mechanical strength in various complex water environments, benefiting their future practical applications. This work unveils the structure-function relationship for composite function films with constructed graded channels in dye/salt separation, which is important for the design and future application of these functional films.