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Abstract In this study, loose nanofiltration membranes made of polysulfone dissolved in co-solvents PolarClean and gamma-Valerolactone were prepared via slot die coating (SDC) on a roll-to-roll (R2R) system by directly coating them onto a support layer or free standing. A solution flow rate of 20 mL/min, substrate speed of 17.1 mm/s, and coating gap of 0.1 mm resulted in the formation of membranes without structural defects. Pre-wetting the support layer with dope solution minimized shrinkage of membrane layer thickness and improved interfacial adhesion. Membrane samples produced using SDC exhibited properties and performance consistent with bench-scale doctor blade extruded samples; pre-wetted and uncompressed samples (SDC-3) exhibited the highest rejection of bovine serum albumin (99.20% ± 1.31%) and along with adequate mean permeability during filtration (70.5 ± 8.33 LMH/bar). This study shows that combining sustainable materials development with SDC provides a holistic approach to membrane separations to bridge materials discovery and membrane formation. 

Next-generation polymeric membranes must be derived from more environmentally friendly materials that have similar solubility and miscibility properties as their predecessors to form permeable and selective membranes. Bio-derived polymers, recycled plastics, and eco-friendly solvents have been demonstrated to produce membranes with similar permeability and selectivity as conventional counterparts, though matching membrane durability and cost-effectiveness remain as future research challenges. Slot die coating and 3D printing have been demonstrated to show the scalability of membrane fabrication. Life cycle assessments have become valuable tools in estimating the total environmental impacts of the manufacturing process and characterizing the sustainability of new materials. Recent advances have shortened the gap between materials innovation research and commercial application.