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

Abstract

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 <10 %) while maintaining an exceptionally high water permeate flux (244.5 L/m2h). Moreover, the membrane exhibited excellent stability. This study demonstrates that the construction of organic/inorganic three-dimensional structures with capillary and skeletal support effects show promise potential for modification of dye/salt separation membranes.