High-hydrophilic and salt rejecting PA-g/co-PVP RO membrane via bionic sand-fixing grass for pharmaceutical wastewater treatment

In this study, a novel PA-g/co-PVP reverse osmosis (RO) composite membrane with high-hydrophilic, antifouling, high salt rejection properties, was prepared according to the principle of sand-fixing grass effect for pharmaceutical wastewater treatment. N-vinyl-2-pyrrolidone (NVP) was used as a “seed agent” that was seeped into a low cross-linked polyamide (PA) film. A hydrophilic molecular brush of polyvinylpyrrolidone (PVP) grafted on the PA surface (PA-g-PVP) similar to grass growing on sand and a cross-linked copolymer layer of PA and NVP (PA-co-NVP) similar to grass roots distributed in sand, as well as an interlayer cross-linking between PA separation layer and PES ultrafiltration membrane with a highly stable interfacial structure, synchronously occurred through γ-ray radiation. Upon incorporation of 1.0% of NVP, the resultant PA-g/co-PVP membrane achieved 18.8° water contact angle and high flux recovery ratio (FRR) values of 91.23%, 96.28%, and 93.67% for the foulants of bovine serum albumin (BSA), sodium alginate (SA), and sodium dodecyl sulfate (SDS), respectively. The FRR value of pharmaceutical wastewater-polluted membrane after cleaning was 94.30%. The PA-g/co-PVP RO membrane showed outstanding separation stability due to the radiation cross-linking reactions, which limit matrix swelling and interface delamination similar to the action principle of sand-fixing grass. These merits prove that the RO membrane developed in this study can be used in many applications, including small organic molecular wastewater separation.