Surface-Controlled Water Flow in Nanotube Membranes

Abstract

The independent effect of nanotube surface chemistry and structure on the flow of water under nanoscale confinement is demonstrated in this paper for the first time via the synthesis of novel carbon nitride nanotube (CNNT) membranes. Using a combination of experiments and high-fidelity molecular dynamics (MD) simulations, it is here shown that the hydrophilisation of the sp 2 carbon structure, induced by the presence of the C-N bonds, decreases the pure water permeance in CNNTs when compared with pristine and turbostratic carbon nanotubes (CNTs). The MD simulations are based on a model true to the chemical structure of the synthesized nanotubes, and built from material spectroscopy measurements and calibrated potentials using droplet experiments. The effect on permeance is explained in terms of solid-liquid interactions at the nanotube wall with increased water viscosity and decreased surface diffusion near the CNNT wall, when compared to CNTs. A model directly linking the solid-liquid interactions to the water permeance is presented, showing good agreement with both experiments and MD simulations. This work opens the way to tailoring surface chemistry and structure inside nanotube membranes for a wide range of transport and separation processes.

Enhanced nanoparticle rejection in aligned boron nitride nanotube membranes

“…The nanotube diameters (D p ) were calculated via statistical image analysis of FESEM micrographs using ImageJ. 13,23 A JEOL JSM-2100Plus TEM was used to assess the size of the nanoparticles used for rejection tests (Table S1 and Fig. S3, S4 †).…”

“…To obtain MD results as close to the experiments as possible, calibration studies of intermolecular potentials between water-BNNT and water-CNT were performed to match experimental contact angles. 23 Partial charges on BN atoms were calibrated using the ReaxFF force field, 28 setting an experimental surface charge density of −1.28 × 10 −20 C nm −2 for BNNT and −6.99 × 10 −21 C nm −2 for the silica particles. No charge was set on the carbon atoms in the CNT case.…”

Just how many holes…?

“…The results of these assays depicted a stark contrast between the high abundance of the proposed mPTP constituents ANT and F 1 F 0 -ATPase and the active mPTP copy number per mitoplast, which turned out to be very low: <10 mPTP at 2 mM [Ca 2+ ] and <5 mPTP at 200 µM [Ca 2+ ]. The water flux calculations on one hand were conservative by using the smallest reported pore diameter (2 nm), while on the other hand the mPTP was approximated by molecular dynamics simulations of pristine carbon nanotubes, which conduct water better than carbon nanotubes with more polar pore lining (Casanova et al, 2019). However, even after correcting to this difference, the predicted copy number is still very low, considering the estimated >10 4 copies of ANT and likely several hundred or thousand copies of ATP synthase (based on proteomic data from yeast; Morgenstern et al, 2017).…”

High‐flux PVDF/PVP nanocomposite ultrafiltration membrane incorporated with graphene oxide nanoribbones with improved antifouling properties

“…11,12 The trade-off relationship between selectivity and permeability as well as membrane fouling is critical issues in the application of polymeric membranes in water and wastewater treatment. [13][14][15] In recent years, to improve the polymeric membrane performance and fouling resistance, researchers have investigated the nanocomopsite membrane which is a heterogeneous combination of inorganic nanomaterials as nanofillers and polymer matrix. [16][17][18][19][20][21] It is expected that this combination produces membranes with better strength and enhanced hydrophilicity.…”

“…Polymeric membranes with robust chemical, mechanical and thermal stabilities and ability to effectively remove contaminants are commonly used in water and wastewater treatments 11,12 . The trade‐off relationship between selectivity and permeability as well as membrane fouling is critical issues in the application of polymeric membranes in water and wastewater treatment 13–15 . In recent years, to improve the polymeric membrane performance and fouling resistance, researchers have investigated the nanocomopsite membrane which is a heterogeneous combination of inorganic nanomaterials as nanofillers and polymer matrix 16–21 .…”