Water/Alcohol Separation in Graphene Oxide Membranes: Insights from Molecular Dynamics and Monte Carlo Simulations

Author(s)

Borges, Daiane Damasceno ^{[1, 2]} ; Woellner, Cristiano F. ^{[1, 2]} ; Autreto, Pedro A. S. ^[3] ; Galvao, Douglas S. ^{[1, 2]}

Affiliation

^[1] Univ Campinas UNICAMP, Ctr Computat Engn & Sci, BR-13083959 Campinas, SP - Brazil

^[2] Univ Campinas UNICAMP, Dept Appl Phys, BR-13083959 Campinas, SP - Brazil

^[3] Fed Univ ABC UFABC, Ctr Nat & Human Sci, BR-09210580 Santo Andre, SP - Brazil

• Document type: Journal article
• Source: MRS ADVANCES; v. 3, n. 1-2, p. 109-114, 2018.
• Web of Science Citations: 1

Abstract

Graphene-based membranes have been investigated as promising candidates for water filtration and gas separation applications. Experimental evidences have shown that graphene oxide can be impermeable to liquids, vapors and gases, while allowing a fast permeation of water molecules. This phenomenon has been attributed to the formation of a network of nano capillaries that allow nearly frictionless water flow while blocking other molecules by steric hindrance effects. It is supposed that water molecules are transported through the percolated two-dimensional channels formed between graphene-based sheets. Although these channels allow fast water permeation in such materials, the flow rates are strongly dependent on how the membranes are fabricated. Also, some fundamental issues regarding the nanoscale mechanisms of water permeation are still not fully understood and their interpretation remains controversial. In this work, we have investigated the dynamics of water permeation through pristine graphene and graphene oxide model membranes that have strong impact on water/alcohol separation. We have carried out fully atomistic classical molecular dynamics simulations of systems composed of multiple layered graphene-based sheets into contact with a pure water reservoir under controlled thermodynamics conditions (e.g., by varying temperature and pressure values). We have systematically analysed how the transport dynamics of the confined nanofluids depend on the interlayer distances and the role of the oxide functional groups. Our results show the water flux is much more effective for graphene than for graphene oxide membranes. These results can be attributed to the H-bonds formation between oxide functional groups and water, which traps the water molecules and precludes ultrafast water transport through the nanochannels. (AU)

• FAPESP's process: 16/12340-9 - Structural and mechanical properties of carbon-based foams
• Grantee: Cristiano Francisco Woellner
• Support type: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 15/14703-9 - Theoretical study on the structural and mechanical properties of MOFs (metal-organic frameworks)
• Grantee: Daiane Damasceno Borges
• Support type: Scholarships in Brazil - Post-Doctorate
• FAPESP's process: 13/08293-7 - CCES - Center for Computational Engineering and Sciences
• Grantee: Munir Salomao Skaf
• Support type: Research Grants - Research, Innovation and Dissemination Centers - RIDC