Modulating interfacial polymerization dynamics in nanostructured thin-film composite membranes: The role of polyvinylpyrrolidone and NaCl

Optimizing the performance of thin-film composite polyamide (TFC-PA) membranes is crucial for enhancing filtration efficiency across diverse applications. This study investigated the role of polyvinylpyrrolidone (PVP) in modulating the diffusion kinetics of piperazine (PIP) during the interfacial polymerization (IP) process, essential for membrane fabrication. By incorporating PVP into the aqueous phase, and combining it with selected inorganic salts such as sodium chloride (NaCl), the formation of a more controlled Turing-like nanostructure within the PA layer was achieved, significantly improving membrane permeability and structural uniformity. Employing molecular simulations alongside diverse characterization techniques, the mechanisms by which PVP and NaCl additives influence the diffusion of PIP monomers at the water-oil interface were elucidated. The optimized membranes demonstrated a substantial increase in water permeability, achieving 16.2 ± 0.9 L m⁻² h⁻¹ bar⁻¹, and an impressive sodium sulfate (Na₂SO₄) rejection rate of 97.5 ± 0.6 %, outperforming untreated nanofiltration (NF) membranes. The findings provide a deeper understanding of the molecular interactions during IP and open avenues for the development of advanced filtration membranes with tailored properties.