Organic-organic interfacial polymerization for the ultrathin polyamide organic solvent nanofiltration membranes

There is an increasing demand for advanced membranes that exhibit both high perm-selectivity and good stability in organic solvents , particularly for organic solvent nanofiltration (OSN). Traditional methods of synthesizing thin films using conventional interfacial polymerization (CIP) have been limited by the use of water-soluble monomers , which has hindered the development of high-performance membranes. To address this issue, a new method called organic-organic interfacial polymerization (OOIP) has been proposed. This method allows for the use of aromatic amines that are not water-soluble in the fabrication of ultrathin polyamide (PA) (<40 nm) thin film composite (TFC) membranes. By investigating five different organic solvents (tetrahydrofuran, acetone, N , N -dimethylformamide, N , N -dimethylacetamide, dimethyl sulfoxide) with varying water content as the organic phase for a water-insoluble benzidine monomer, two diffusion models of monomers were identified that resulted in different membrane structures and degrees of network crosslinking. The ultrathin PA membranes produced using tetrahydrofuran-H 2 O and N , N -dimethylformamide-H 2 O, along with solvent activation, demonstrated high methanol permeances of 11.4 L m −2  h −1 bar −1 and 6.0 L m −2  h −1 bar −1 , respectively, while maintaining exceptional rejections of over 99.0 % for small molecules with molecular weights greater than 452 g mol −1 . The OOIP method is scalable and reproducible, making it suitable for large-scale membrane production. This innovative approach shows great potential for advancing OSN technology and providing efficient and cost-effective separation solutions for various industries.