Facile preparation of polyacrylonitrile-co-methylacrylate based integrally skinned asymmetric nanofiltration membranes for sustainable molecular separation: An one-step method

While polyacrylonitrile (PAN) has been widely used to prepare membranes, it is still not handy to prepare PAN integrally skinned asymmetric (ISA) nanofiltration (NF) membrane via direct immersion precipitation phase inversion method. Herein, a low-cost and commercial polyacrylonitrile-co-methylacrylate, P(AN-co-MA), was demonstrated to prepare ISA NF membranes via a one-step immersion precipitation phase inversion process. It was found that increasing P(AN-co-MA) concentration in NMP can shift the membranes from ultrafiltration (UF) to NF range. The addition of a co-solvent in dope could further improve dye rejection. Effects of solvent (NMP or DMF)/co-solvent (THF and 1,4-dioxane) type and mass ratio in dope solution on membrane separation performance were further investigated. The membrane prepared from a 20% polymer concentration and a NMP/1,4-dioxane ratio of 3:1 showed 87.4% methyl orange (MO) rejection and 98.3% rose bengal (RB) rejection, and simultaneously a relatively high water permeance of 55.22 L m−2 h−1 bar−1. Increase in the content of co-solvent in solvent/co-solvent mixture would depress the formation of macrovoids, lead to a dense top layer and contribute to high dye rejections. The low-cost and one-step process to prepare P(AN-co-MA) ISA NF membranes disclosed in this study paved a new way for sustainable molecular separation.