Tunable water desalination across graphene oxide framework membranes

Abstract

The performance of graphene oxide framework (GOF) membranes for water desalination is assessed using classical molecular dynamics (MD) simulations. The coupling between water permeability and salt rejection of GOF membranes is studied as a function of linker concentration n, thickness h and applied pressure ΔP. The simulations reveal that water permeability in GOF-(n,h) membranes can be tuned from ∼5 (n = 32 and h = 6.5 nm) to 400 L cm(-2) day(-1) MPa(-1) (n = 64 and h = 2.5 nm) and follows a Cnh(-αn) law. For a given pore size (n = 16 or 32), water permeability of GOF membranes increases when the pore spacing decreases, whereas for a given pore spacing (n = 32 or 64), water permeability increases by up to two orders of magnitude when the pore size increases. Furthermore, for linker concentrations n ≤ 32, the high water permeability corresponds to a 100% salt rejection, elevating this type of GOF membrane as an ideal candidate for water desalination. Compared to experimental performance of reverse osmosis membranes, our calculations suggest that under the same conditions of applied pressure and characteristics of membranes (ΔP ∼ 10 MPa and h ∼ 100 nm), one can expect a perfect salt rejection coupled to a water permeability two orders of magnitude higher than existing technologies, i.e., from a few cL cm(-2) day(-1) MPa(-1) to a few L cm(-2) day(-1) MPa(-1).

Graphene oxide: the new membrane material

“…2(C) is the schematic for possible water vapor transport method through GO membrane. Nair et al [1] explains that the GO laminates are made of crystallites stacked on top of each other and the hydroxyl and epoxy groups attached to the graphene sheets offers spacing between the Water transport [50] Ozonated graphene oxide membrane Proton exchange [54] Graphene oxide membrane filters Bacterial inactivation and removal [56] Graphene oxide membrane Desalination [60] membranes. According to their model and explanation, the pristine graphene capillaries are wide open to accommodate the water molecule and the capillaries becomes narrow in low humidity, which do not provide enough Vander-Waals distance to accommodate water molecules and this mechanism is shown in the Fig.…”

Separation and purification using GO and r-GO membranes

“…Nicolaï et al 116 utilized MD simulation method to demonstrate that freestanding GO membranes are possible to reject salt with 100% rejection rate in RO process. For experimental results, on the one hand, modifying conventional membranes by doping (r)GO-based materials is a widely used strategy for desalination.…”

A Short Review of the Architecture and Computational Analysis in the Design of Graphene Based Bioelectronic Devices

“…11(c). (70) In such an environment, where changes in species velocity are very sensitive to any change exerted by the forces of the medium, the transfer of momentum between ions and solvent is better explained by the Navier-Stokes equation: A nanopore introduced to a single layer of graphene for DNA sequencing, (64) and (b) catalyst-decorated 3D graphene composite electrodes for biofuel cells. (67,68) Here, the velocity of the diluted species, v, and the species density ρ are related to the pressure inside the channel, p, the viscosity of the transport medium, η, and the volume force acting on the fluid, f, in one governing equation.…”

“…9. (Color online) (a) Multilayer graphene cross-linked with graphene oxide used for water desalination, (64) (b) structured pore clusters of graphenelike organic metal membrane for drug delivery, (11) (c) binary silica layer for water transport, (66) and (d) lipid bilayer.…”

“…Taking into consideration that d x is fixed (based on the type of cross-linker), the free volume for transport is reduced in the case of a high concentration of cross-linker. (64) An example of a structured pore transport medium is the structured pore clusters of graphenelike organic metal membranes for drug delivery [ Fig. 9(b)].…”