Engineering a separation membrane containing a gel layer with backbone support effect and bionic-inspired capillary effect for the efficient separation of dyes/salts

Inspired by the capillary phenomenon in nature and the structure of siliceous sponges, a gel layer with backbone support effect and capillary force was constructed on the membrane surface, which endowed the membrane with high permeate flux and at the same time made the membrane have excellent dye/salt separation performance. [Display omitted] •Special structured gel separation layer was constructed on the membrane surface.•The gel layer possessed a skeleton support structure and capillary effect.•The introduction of Ag NPs avoided the collapse of the gel layer under pressure.•Microchannels between Ag NPs provide capillary force to the membrane.•The membrane realized efficient dye/salt separation with ultra-high flux. Accurate separation of dyes/salts is a crucial step in the treatment of dye-containing wastewater. Therefore, separation membranes with high permeability and high dye/salt selectivity are urgently required. In this study, an ultrathin gel layer of carboxymethyl cellulose was constructed on a poly(vinylidene fluoride) membrane surface. This gel layer contains a backbone support structure and provides the bionic-inspired capillary effect, which endows the membrane with the capability to realize the efficient separation of dyes and salts. The introduction of silver nanoparticles (Ag NPs) into the gel layer provides a skeleton support structure, which prevents the collapse of the gel layer, reduces the actual separation layer thickness, and decreases the mass transfer resistance. Moreover, the formation of capillaries between the numerous Ag NPs facilitates the rapid penetration of water molecules. Interestingly, this membrane exhibited excellent selectivity for dye/salt separation (dye removal >99.5 %, salt removal