Asymmetric polyethersulfone ultrafiltration membranes with high perm-selectivity of nitrate ions for energy-efficient water treatment

This study presents the fabrication and evaluation of asymmetric polyethersulfone (PES) ultrafiltration membranes designed for high perm-selectivity of nitrate ions from mixed-ion solutions. Polyvinylpyrrolidone (PVP) was employed as a pore-forming agent to modify the porous structure of the membranes, particularly affecting the characteristics of the surface skin layer. These structural modifications play a crucial role in determining the physical properties and water permeation flux of the designer membranes. Additionally, the membrane comprising 16 wt% PES and 5 wt% PVP exhibits superior performance in the selective separation of nitrate (NO₃^–) ions from fluoride (F⁻) and sulfate (SO₄²⁻) ions during electrolysis. At a constant potential of 1 V, the P16K5 membrane delivers a perm-selectivity of 1.6 and 2.6 for NO₃^–/F⁻ and NO₃^–/SO₄²⁻, respectively. Additionally, nearly 100 % of NO₃^– removal can be achieved at an applied potential of 5 V. Furthermore, the energy consumption analysis suggests that the proposed asymmetric PES membrane serves as a promising ion-selective material for energy-efficient water treatment applications in a cost-effective manner.