Performance enhancement of thin-film nanocomposite nanofiltration membranes via embedment of novel polydopamine-sulfobetaine methacrylate nanoparticles

Novel poly(dopamine-sulfobetaine methacrylate) [P(DA-SBMA)] nanoparticles were synthesized through oxidative polymerization and aza-Michael addition. By means of interfacial polymerization (IP), they were embedded in the selective polyamide (PA) layers of thin-film nanocomposite (NF) membranes with the intention of improving membrane separation efficiency and hydrophilicity. The organic solution, trimesoyl chloride (TMC) in n-hexane, was chosen as the dispersing medium for the nanoparticles in preference to the aqueous solution, piperazine (PIP) in water, to ensure their effective entrapment within the two layers. This was supported by data from Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, and X-Ray Photoelectron Spectroscopy. The optimal performance was demonstrated by TFN membranes with a weight ratio [g P(DA-SBMA)/g TMC] of 0.55 [TFNP(DA-SBMA)-0.55], delivering a pure water flux of 73.11 ± 6.78 L·m−2 ·h−1 and salt rejections of 98%, 95%, 54%, and 42% for Na2SO4, MgSO4, MgCl2, and NaCl, respectively, at 30 °C, 6.0 bar. Furthermore, TFNP(DA-SBMA)-0.55 membranes exhibited excellent antifouling properties against bovine serum albumin (BSA), indicating that exposure to proteins does not heavily affect the performance of P(DA-SBMA)-embedded nanofiltration membranes.