Hyperlooping\nCarbon Nanotube-Graphene Oxide Nanoarchitectonics\nas Membranes for Ultrafast Organic Solvent Nanofiltration

Abstract

Membrane technology is a key enabler for a circular pharmaceutical\nindustry, but chemically resistant polymeric membranes for organic\nsolvent nanofiltration (OSN) often suffer from lower-than-required\nperformances. Recently, graphene-based laminated membranes using small-flake\ngraphene oxide (SFGO) nanosheets open up new avenues for high-performance\nOSN, but their permeance toward high viscosity solvents is below expectation.\nTo address this issue, we design hyperlooping channels using multiwalled\ncarbon nanotubes (MWCNTs) intercalated within lanthanum(III) (La³⁺)-cross-linked SFGO nanochannels to form a ternary nanoarchitecture\nfor low-resistant transport toward high viscosity solvents. At optimized\nMWCNT loading, the defect-free membrane exhibits 138 L m^–2 h^–1 bar^–1 ethanol permeance\nat >99% rejections toward organic dyes, outperforming state-of-the-art\ngraphene oxide (GO)-based membranes to date. Even butanolwith\ntwice the viscosity of ethanolexhibits a permeance no less\nthan 60 L m^–2 h^–1 bar^–1 at comparable rejection rates. Theoretical simulation suggests that\nLa³⁺ cross-linking is critical and can create an intact\narchitecture that brings size exclusion into play as the dominant\nseparation mechanism. Also, MWCNT nanochannel offers at least 1.5-fold\nlower ethanol transport resistance than that of the GO nanochannel,\nowing to greater bulk freedom in orientating ethanol molecules. Overall,\nthe hyperlooping architecture demonstrates ∼3-fold higher permeance\nthan neat SFGO membrane for elevating OSN performances.