Influence of Solvent Content in the Coagulation Bath and of Polyvinylpyrrolidone on the Properties of PSF/PES Blend Membranes For Water/Oil Separation

The use of a coagulation bath and the inclusion of polyvinylpyrrolidone (PVP) are key in influencing the structural features and operational behavior of polymeric membranes. Previous investigations involving polysulfone (PSf) and polyethersulfone (PES) membranes emphasize the importance of these elements. This study investigates the effect of solvent content in the coagulation bath and the addition of PVP on the properties of flat-sheet PSf/PES blend membranes in water/oil separation applications. This research examines how varying the solvent concentration in the coagulation bath, combined with PVP incorporation, influences the characteristics of PSf/PES blend flat membranes applied to water/oil separation. Membranes were prepared using both pure polymers and PSf/PES blends and characterized through scanning electron microscopy (SEM), permeation evaluations, and separation performance analyses. The incorporation of PVP enhanced the hydrophilic nature of the membrane, evidenced by a decrease in water contact angle (WCA). In addition, the oil contact angle (OCA) of membranes with elevated PVP content demonstrated greater underwater oleophobicity. SEM analysis revealed structural modifications, including variations in pore size and density, as well as changes in finger-like structures and macropores. Membranes containing PVP exhibited greater pore uniformity compared to the pure membrane, resulting in a more pronounced enlargement of the average pore size, which contributed to higher fluxes while maintaining oil removal performance. Furthermore, a connection between viscosity, pore structure, and flux outcomes was explored, correlating these factors with demixing kinetics. Membranes containing PVP exhibited higher fluxes, confirming its positive impact on separation efficiency.