Use this URL to cite or link to this record in EThOS:
Title: Understanding the mechanism of permeation through graphene-based membranes using molecular dynamics simulations
Author: Dix, James
ISNI:       0000 0004 7656 3870
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2017
Availability of Full Text:
Access from EThOS:
Access from Institution:
The UN predicts that by 2050 there will water shortages throughout the globe. Current sources for safe, clean drinking water are being over mined and exhausted. Seawater provides an alternative water source, but a high salt content makes it unsuitable for the majority of applications. However, reverse osmosis lowers the salt content producing water that is safe for human consumption. Reverse osmosis uses a semi-permeable membrane to prevent the transport of salt but allows for the transport of water. Currently these membranes are susceptible to fouling and contamination, which reduces their efficiency. Graphene-oxide membranes offer a new material for reserves osmosis membranes. Sheets of graphene-oxide are stacked in a layered structure. The separation between the sheets can be controlled using physical confinement, resulting in limited ion permeation of abundant cations in seawater, like Na+ and K+. This is believed to be due to the separation of 0.76 nm between the graphene sheets, forcing the ions to lose its surrounding water molecules, making it unfavourable for the ion to travel through the membrane. Molecular dynamics simulations can give an atomic level insight into the molecular processes within GO membranes. Recent simulations have shown that charged species are attracted to graphene surfaces due to polarisation of the pi-electron system. This work has managed to incorporate these ion-pi interactions into molecular dynamics simulations. Including ion-pi interactions caused some ions, like Na+ and K+, to prefer to lose water molecules and reside at a graphene surface. This work observed the same phenomena when ions were confined to graphene channel ranging from 1.3 nm - 0.7 nm. This observation could have a large impact on whether dehydration is limiting the permeation of these two ions, or if there are additional processes that limit their molecular transport.
Supervisor: Raveendran Nair, Rahul ; Carbone, Paola Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: water confinement ; ion confinement ; ion water structure ; molecular dynamics ; desalination ; ion transport ; ion permeation ; Graphene ; molecular modelling ; cation-pi