Influence of electric fields on the efficiency of multilayer graphene membrane

Abstract

Multilayer graphene membranes could be considered as an efficient membrane in water desalination processes based on the reverse osmosis (RO) method. In this study, we designed multilayer graphene channels using the molecular dynamics (MD) simulation approach. The effects of different parameters, such as channel width and length, and the pressure on the operation of the designed channels were examined, in the absence and presence of electric fields with various amplitudes and directions. The results indicated that the ion separation and water flow through the channels were modified under the application of the electric fields. Additionally, it has been shown that salt rejection and water flow could be controlled by the channel's structural parameters mentioned above. The obtained results of this study at the molecular level can improve the knowledge of designing membranes for water purification processes. Graphical abstract Using MD method a multilayer graphene membrane was designed to separate Na and Cl ions from a NaCl solution by the aid of external electric field, which can significantly effect the membrane operation.

Coupled Transport of Water and Ions through Graphene Nanochannels

“…The experimental nanofluidic systems normally use 1−100 bars of pressure 12,16,20,23,32 and 10 −4 to 10 −3 V/nm of electric field, 4,19,26,29,32 while most of the simulations use 10 2 to 10 3 bars of pressure 5,8,15,39,41−43 and 0.1−1.0 V/nm of electric field. 7,9,10,30,31,34,40,44 Consequently, following most of the previous simulation work, the present field strength is chosen as 0.1−0.5 V/nm. The MD simulations were carried out by the Gromacs 4.6.7 simulation package 45 at constant pressure and a temperature of 300 K (Nose−Hoover coupling).…”

“…For example, the channel length in experiments is normally in micrometers, and the corresponding data can be collected in the unit of second, minute, or hour. ,,,,,,,, However, in simulations, the channel length is always several nanometers with data collection in nanoseconds. ,,,− To reduce the statistical uncertainty and collect enough transportation events during the available simulation time of ∼100 ns, a larger driving force is always necessary. The experimental nanofluidic systems normally use 1–100 bars of pressure ,,,, and 10 –4 to 10 –3 V/nm of electric field, ,,,, while most of the simulations use 10 2 to 10 3 bars of pressure ,,,,− and 0.1–1.0 V/nm of electric field. ,,,,,,, Consequently, following most of the previous simulation work, the present field strength is chosen as 0.1–0.5 V/nm.…”

“…31 In principle, the water and ionic transport should be coupled to each other in comparable confinement 32 depending on the channel wall materials. 26,33 Although a recent simulation partially reveals the water transport and ion rejection for different graphene layer spaces, 34 it is also necessary for us to further understand the channel height effect in a more wide range, 20,25 how the ions transport in the two-dimensional ice, the size effect of different ions, and the coupling transport relation between water and ions. Herein, we present a comprehensive simulation study focusing on these questions.…”

Effect of ethanol in the coagulation bath on the structure and performance of PVDF‐g‐PEGMA/PVDF membrane

“…In addition, as the ethanol content in the coagulation bath increases, the pure water flux of the modified membrane increases as well. Pure water flux of the membrane is mainly related to the, membrane thickness (separated channel), pore size, pore distribution, transmembrane pressure and hydrophilicity of the membrane surface . However, the results of the pure water flux of the membranes M 2 and M 3 do not agree with the hydrophobicity/hydrophilicity results obtained from the contact angle measurements.…”

“…Pure water flux is inversely proportional to the contaminant rejection rate. Excessive pore size of the membrane or excessive passage of water molecules increases the flux of pure water, but at the same time, it causes the retention of the membrane to deteriorate . As the membrane average pore size becomes larger, the retention effect of SA deteriorates: retention for membranes M 2 and M 3 were only 65.18 and 54.46%, respectively.…”