Ultra-smooth and ultra-thin polyamide thin film nanocomposite membranes incorporated with functionalized MoS2 nanosheets for high performance organic solvent nanofiltration

Abstract

Organic solvent nanofiltration (OSN) membranes are the key factors for the treatment of organic solution via OSN technology. In this work, we fabricated a kind of ultra-thin and ultra-smooth thin-film nanocomposite (TFN) OSN membrane using interfacial polymerization (IP) process with ultra-low concentration for both the aqueous and the organic monomers, together with doped tannic acid (TA) functionalized Molybdenum disulfide (MoS2) nanosheets of ultra-low content in the aqueous monomer solution, and followed by post-IP chemical crosslinking and solvent activation procedures. The results demonstrated that the incorporated TA-MoS2 nanosheets not only help to promote the solvent permeation, but also help to increase the solvent resistance and fouling resistance of the fabricated membrane. The optimal TFN OSN membrane fabricated using 0.05 wt% aqueous m-phenylenediamine (MPD) solution doped with TA-MoS2 nanosheets content of 50 mg L−1 and 0.0025 wt% trimesoyl chloride (TMC) / n-hexane solution has an ultra-thin barrier layer, with an average thickness of about 15 nm. This endows it a much higher pure DMF permeance of 219.1 L m−2 h−1 MPa−1, which is much superior over most of literature works. Meanwhile, the fabricated TFN OSN membrane achieves a rejection of 99.1 % for rhodamine B (RDB, 479 Dalton), which is about 10.1 % increment compared with that of the baseline thin-film composite (TFC) membrane. The TFN OSN membrane also features an ultra-smooth skin layer, with a surface roughness of merely about 2.0 nm, which is quite beneficial for its fouling resistance performance. Moreover, the TFN OSN membrane features outstanding high solvent resistance. It remained a nearly constant and extremely high rejection for Rose Begal (RB, 1017 Dalton), about 99.9 %, and a much higher DMF permeance, 101 ± 2 L m−2 h−1 MPa−1, after cross-flow filtration for more than 200 h using 100 mg L−1 RB / DMF solution as feed, which is seldomly reported in literature. Even being immersed in DMF at 80 °C for more than 144 h, it remained a rejection of higher than 98 % for Rhodamine B (479 Dalton), indicating its superior solvent resistance and promising industrial application prospect.