Flower-like MnO2 nanoparticles modified thin film nanocomposite membranes for efficient organic solvent nanofiltration

Abstract

Novel thin film nanocomposite (TFN) membranes comprised of polyimide (PI) supporting layer and polyamide (PA) skin layer were prepared for efficient organic solvent nanofiltration (OSN) by doping flower-like MnO2 nanomaterials in PA skin layer through interfacial polymerization (IP). The OSN performance of TFN membranes doped with flower-like MnO2 nanomaterials was significantly improved compared to pristine thin film composite (TFC) and spherical MnO2 nanoparticle-doped (TFN-S) membranes. The synthesized optimal sample (TFN-0.50 membrane) exhibits the optimum methanol permeability of 11.88 L m−2 h−1 bar−1 (1.54 times more than the TFC membrane and 1.20 times more than the TFN-S membrane). This excellent OSN performance is due to the large spatial site resistance effect present in the flower-like MnO2 nanoparticles themselves which make the diffusion rate of MPD monomer from the aqueous phase to the oil phase unstable, resulting in unstable interfacial polymerization reactions. The unstable interfacial polymerization confers a ridge-valley surface morphology that allows the TFN membrane to have an increased contact area with the solvent. Meanwhile, the special flower-like structure of MnO2 nanomaterials provides additional transport channels for solvent transport. In addition, the prepared TFN-0.50 membrane has good long-term operability and organic solvent nanofiltration even after immersion in strongly polar DMF solvent at 80 °C for 5 days.