Quantized Water Transport: Ideal Desalination through Graphyne-4 Membrane

Abstract

Graphyne sheet exhibits promising potential for nanoscale desalination to achieve both high water permeability and salt rejection rate. Extensive molecular dynamics simulations on pore-size effects suggest that γ-graphyne-4, with 4 acetylene bonds between two adjacent phenyl rings, has the best performance with 100% salt rejection and an unprecedented water permeability, to our knowledge, of ~13 L/cm2/day/MPa, 3 orders of magnitude higher than prevailing commercial membranes based on reverse osmosis, and ~10 times higher than the state-of-the-art nanoporous graphene. Strikingly, water permeability across graphyne exhibits unexpected nonlinear dependence on the pore size. This counter-intuitive behavior is attributed to the quantized nature of water flow at the nanoscale, which has wide implications in controlling nanoscale water transport and designing highly effective membranes.

Nanoporous two-dimensional MoS2 membranes for fast saline solution purification

“…Similar methods were used successfully in studying the water purification 10,22 and the water transport. 6,15,25,26 Two ways are compared and significant difference is not found (see Fig. 6,15,25,26 Two ways are compared and significant difference is not found (see Fig.…”

“…4,5,6,7 As an example, both actual experiments and molecular dynamics (MD) simulations have demonstrated that carbon nanotube membranes with proper diameter have a high solute rejection and superb water transport rate which is three to five orders of magnitude faster than that predicted from conventional fluid-flow theory. 14,15,16,17,18,19,20,21,22,23,24,25,26 Such 2D nanoporous membranes may be ideal for water purification because the pore scales at the molecular level can be tailored to allow the passage of small molecules (such as water molecules), but block the passage of larger particles such as ions. 14,15,16,17,18,19,20,21,22,23,24,25,26 Such 2D nanoporous membranes may be ideal for water purification because the pore scales at the molecular level can be tailored to allow the passage of small molecules (such as water molecules), but block the passage of larger particles such as ions.…”

Single-layer graphyne membranes for super-excellent brine separation in forward osmosis

“…Several researchers have shown the feasibility of using single-layer porous graphene in brine separation or desalination 43-45 by experiment. Graphyne-N (N = 1, 2, 3, …) are obtained by connecting N acetylenic bonds among the adjacent six-membered rings of graphene [46][47][48][49][50][51][52][53][54][55][56] and the effective Van der Waals pore diameter of graphyne-N increases with the increase of N. 48,49 Researches by molecular simulation show that single-layer graphyne-N (N = 3, 4, 5, 6) membrane has high mechanical strength, its Young's modulus reaches up to 365-700 GPa, the uniaxially stretched final strength reaches up to 25-100 GPa and the ultimate uniaxial tensile strain is over 6%, which are sufficient for them to withstand the stress and deformation in clamping process or the external pressure when used in RO. Nevertheless, single-layer graphene membrane is non-porous and need drilling, and it is difficult to precisely control the size and distribution of the pores in practice.…”

“…[46][47][48][49][50] Kou et al 46 reported that the net water flux through the monolayer graphyne-3 membrane was much higher than that through the CNT membrane with similar nanopore diameter and the remarkable hydraulic permeability was attributed to the hydrogen bond formation. [46][47][48][49][50] Kou et al 46 reported that the net water flux through the monolayer graphyne-3 membrane was much higher than that through the CNT membrane with similar nanopore diameter and the remarkable hydraulic permeability was attributed to the hydrogen bond formation.…”

“…Zhu et al 47 showed that water permeability through graphyne exhibited nonlinear dependence on the pore size and they attributed this counter-intuitive behavior to the quantized nature of water flow at the nanoscale. Zhu et al 47 showed that water permeability through graphyne exhibited nonlinear dependence on the pore size and they attributed this counter-intuitive behavior to the quantized nature of water flow at the nanoscale.…”