Nitrogen Plasma‐Engineered Hydrophilic Surface Functionalization of Polysulfone Ultrafiltration Membranes for Enhanced Functional, Structural, and Filtration Efficiency

ABSTRACT This study investigates the effect of low‐pressure direct current (DC) nitrogen plasma treatment on the surface modification and filtration performance of polysulfone (PSF) ultrafiltration membranes. Plasma treatment significantly enhances membrane hydrophilicity, as evidenced by reduced water and hexadecane contact angles and increased surface energy. Surface characterization through SEM and AFM reveals pore enlargement, macrovoid formation, and increased surface roughness. Surface chemical analysis using XPS, FTIR, and NMR confirms the incorporation of nitrogen‐containing functional groups in plasma‐treated membrane. A surface chemical reaction mechanism induced by plasma treatment is proposed and validated through surface chemistry data and Optical Emission Spectroscopy. Mechanical testing indicates that the bulk integrity of the membrane remains uncompromised. Plasma‐treated membranes exhibit enhanced porosity, water flux and rejection efficiency, as supported by Barrett–Joyner–Halenda (BJH) analysis. Ageing studies reveal an initial phase of hydrophobic recovery within the first week, followed by stabilization, consistent with a diffusion‐based ageing model. XPS further validates the reorientation and diffusion behavior of functional groups over time. The cake filtration model is used to describe the dominant fouling mechanisms observed. Overall, the results highlight the potential of nitrogen plasma‐treated PSF membranes for wastewater treatment applications, offering improved performance and long‐term stability.