Ultrapermeable nanofiltration membranes with tunable selectivity fabricated with polyaniline nanofibers

Abstract

Ultrapermeable polyamide nanofiltration membranes with tunable salt sieving properties were prepared using polyaniline nanofibers. The structural evolution of the three-layered thin film composites enables the formation of both ultrathin and nanostructured polyamide selective layers on a macroporous microfiltration membrane for improved water permeance, while the acid doping chemistry of polyaniline endows the polyamide layer with tunable pore size and surface charge for improved ion sieving. The membrane with a confined pore size in the polyamide layer shows selectivities of 30.1 for Mg²⁺/Na⁺ and 279.0 for SO₄²⁻/Cl⁻ with a high water permeance of 39.1 L m⁻² h⁻¹ bar⁻¹. The membrane with an enlarged pore size in the polyamide layer demonstrates an ultrahigh water permeance of 49.7 L m⁻² h⁻¹ bar⁻¹ with good retention for both Na₂SO₄ and MgSO₄ which equals 98.7% and 97.9% salt rejection, respectively.