A novel green solvent alternative for polymeric membrane preparation via nonsolvent-induced phase separation (NIPS)

Abstract

The membrane market has grown rapidly over the past several decades, supported by continuous improvements in membrane performance, module and process design, and fouling control. However, such growth will be unsustainable with current membrane fabrication methods that employ significant amounts of toxic solvents (e.g., N-methylpyrrolidone, dimethylacetamide, and dimethylformamide), thereby producing billions of liters of contaminated wastewater each year. A possible solution is to identify greener alternatives with appropriate properties that are compatible with conventional polymers. In this work, we employed a novel green solvent, Rhodiasolv PolarClean®, that is less toxic than current solvents and eco-friendly, while exhibiting the necessary properties to be employed as a solvent for membrane preparation via the nonsolvent-induced phase separation (NIPS) method. Rhodiasolv PolarClean® has been successfully applied to membrane preparation for water desalination and reclamation by ultrafiltration (UF) and nanofiltration (NF) with conventional polymers, including polysulfone (PSF), polyethersulfone (PES), and cellulose acetate (CA). The UF membranes prepared from PES/Pluronic F127 and PSF/polyvinylpyrrolidone exhibited pure water permeabilities greater than 314.5 ± 57.8 L m−2 h−1 bar−1 and tensile strength 3.78 ± 0.12 MPa with BSA rejection of 98.1 ± 0.4%. Cellulose acetate membrane used for NF applications demonstrated pure water permeability of 1.5 ± 0.25 L m−2 h−1 bar−1 with NaCl and MgCl2 rejection of 85.1 ± 5.7% and 93.2 ± 4.7%, respectively. The performance of the prepared membranes was competitive with current state-of-the-art membranes across all applications, indicating immediate applicability to improving the sustainability of membrane fabrication processes.