One dimensional building blocks for molecular separation: laminated graphitic nanoribbons

Abstract

Herein, a new carbon-based graphitic membrane composed of laminated graphitic nanoribbons with a nanometer-scale width and micrometer-scale length, the graphitic nanoribbon membrane, is reported. Compared to the existing graphitic membranes, such as those composed of graphene oxide and carbon nanotubes, the developed membrane exhibits several unique characteristics in pressure-driven systems. First, the short diffusion length through its interlayer and the free volume of its stacked nanoribbons result in high solvent flux regardless of solvent polarity (water: 25-250 L m h bar; toluene: ∼975 L m h bar; hexane: ∼240 L m h bar). The flux value for water is one order of magnitude higher, while that for nonpolar organic solvents is two to three orders of magnitude greater than the corresponding flux values obtained through commercially available nanofiltration membranes. Second, the membrane exhibits good separation performance, particularly with organic dye molecules (∼100%) and trivalent ions (∼60%), maintaining high solvent flux during extended filtration. Finally, the membrane exhibits high stability in various fluids, e.g., 1 M HCl solution, 1 M NaOH solution, toluene, ethanol, and water, as well as under hydraulic pressures of up to 50 bar. Electron microscopy observation and simulation results suggest that such distinctive features of the membrane are related to the entangled thin multilayers of the graphitic nanoribbons, which possibly originate from the high aspect ratio and narrow width of the nanoribbons.

Large-Area Ti3C2Tx-MXene Coating: Toward Industrial-Scale Fabrication and Molecular Separation

“…This reduction is evident because the filtered dye blocks channel entry on the membrane surfaces. 28,29 The rejection rates of the dye solutions (MR, MnB, BBG, EB, and RosB) were 93.2, 99.9, 98.2, 87.8, and 96.6% for the slot-die coated Ti 3 C 2 T x membranes and 77.9, 86.3, 94.2, 46.2, and 97.9% for the vacuum-filtered Ti 3 C 2 T x membranes, respectively (Figure 4B), indicating the better separation ability of the slotdie-coated membrane. The inset images show the solutions before and after filtration: F is feed, V is permeate of the vacuumfiltered membrane, S is permeate of the slot-die-coated membrane.…”

Graphene Oxide Nanoribbon Hydrogel: Viscoelastic Behavior and Use as a Molecular Separation Membrane

“…For the dried GONR, the (001) peak is observed at 11.2°, regardless of its concentration, indicating the stacking of GONRs after the removal of water. The broad XRD peak of the GONR at 2θ of 11.2° is due to its narrow width (50–75 nm) and the presence of oxygen functional groups, which hinder the narrow stacking between the basal planes of GONRs. , However, the (001) peak is not observed in the as-prepared GONR hydrogel (50 mg/mL), which only shows a peak at 27.4° owing to the multilayered structure of the GONR hydrogel (Figure S1). , Therefore, while GONRs are physically entangled in their assembled structures in the suspension, the surrounding water molecules and electrostatic repulsion by oxygen functional groups effectively prevent the physical stacking of the GONR layers.…”

“…Graphene nanoribbon (GNR), a nanostrip of graphene, has recently been used widely for energy storage, nanocoatings, fiber formation, membrane separation, sensors, etc . owing to its chemical and physical properties such as a controllable band gap, large surface area, electrical conductivity, and chemical stability and so forth. , However, there is still a lack of the understanding of the structure and viscoelastic behavior of GNR in solvents, although many studies have been reported on those of GO and CNTs. − Herein, we report the preparation of aqueous GONR (graphene oxide nanoribbon) hydrogels and a systematic study of their rheological properties.…”

“…5,6 On the other hand, CNTs are known to assemble from isotropic to nematic and columnar liquid crystalline phases with an increase in their concentration, because of their onedimensional (1D) tubelike geometry. 7 Graphene nanoribbon (GNR), a nanostrip of graphene, has recently been used widely for energy storage, 8 nanocoatings, 9 fiber formation, 10 membrane separation, 11 sensors, 12 etc. 13 owing to its chemical and physical properties such as a controllable band gap, large surface area, electrical conductivity, and chemical stability and so forth.…”

Recent Developments in Nanoporous Graphene Membranes for Organic Solvent Nanofiltration: A Short Review

“…Similar to GO nanosheets, GO nanoribbons (GONRs) are one-dimensional graphitic carbon nanosheets that can be fabricated by the oxidation of carbon nanotubes (CNTs). Kim et al first suggested the use of laminated GONR membranes for molecular separation in water and various organic solvents [78]. Regardless of membrane thickness, this membrane, prepared by simple vacuum filtration, exhibited a significantly higher water flux than the normal GO membrane, owing to the short diffusion pathway through the laminates and free volume between the entangled nanoribbons (Figure 7a).…”