Insights on the mechanism of water-alcohol separation in multilayer graphene oxide membranes: Entropic versus enthalpic factors

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 Estadual Campinas, UNICAMP, Appl Phys Dept, BR-13083959 Campinas, SP - Brazil

^[2] Univ Estadual Campinas, UNICAMP, Ctr Computat Engn & Sci, 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: Carbon; v. 127, p. 280-286, FEB 2018.
• Web of Science Citations: 15

Abstract

Experimental evidence has shown that graphene oxide (GO) can be impermeable to liquids, vapors and gases, while it allows a fast permeation of water molecules. Theoretical studies to understand the filtration mechanisms come mostly from water desalination, while very few works have been dedicated to alcohol dehydration. In this work, we have investigated the molecular level mechanism underlying the alcohol/water separation inside GO membranes. A series of Molecular Dynamics and Grand-Canonical Monte Carlo simulations were carried out to probe the ethanol/water and methanol/water separation through GO membranes composed of multiple layered graphene-based films with different interlayer distance values and number of oxygen-containing functional groups. Our results show that the size exclusion and membrane affinities are not sufficient to explain the selectivity. Besides that, the favorable water molecular arrangement inside GO 2D-channels forming a robust H-bond network and the fast water permeation are crucial for an effective separation mechanism. In other words, the separation phenomenon is not only governed by membrane affinities (enthalpic mechanisms) but mainly by the geometry and size factors (entropic mechanisms). Our findings are consistent with the available experimental data and contribute to clarify important aspects of the separation behavior of confined alcohol/ water in GO membranes. (C) 2017 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 13/08293-7 - CCES - Center for Computational Engineering and Sciences
• Grantee: Munir Salomao Skaf
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 14/24547-1 - Theoretical investigations on growth and fracture mechanisms of graphene-based nanostructures
• Grantee: Cristiano Francisco Woellner
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 15/14703-9 - Theoretical study on the structural and mechanical properties of MOFs (metal-organic frameworks)
• Grantee: Daiane Damasceno Borges
• Support Opportunities: Scholarships in Brazil - Post-Doctoral