Water-methanol mixture confined in a graphene slit-pore

TL;DR

This study uses molecular dynamics simulations to investigate how a graphene slit-pore influences the separation of water-methanol mixtures, revealing optimal pore sizes for efficient separation based on component distribution and diffusivity.

Contribution

It introduces a detailed simulation analysis of water-methanol separation in graphene slit-pores, identifying pore size effects on component distribution and diffusivity for potential membrane design.

Findings

Water tends to occupy the center of the pore, methanol near the walls.

Diffusivity of water is consistently higher than methanol.

A pore size of 12.5 Å is optimal and mechanically stable.

Abstract

Efficient and sustainable techniques for separating water-methanol mixtures are in high demand in the industry. Recent studies have revealed that membranes and 2D materials could achieve such separation. In our research, we explore the impact of a nanoconfining graphene slit-pore on the dynamics and structure of water-methanol mixtures. By Molecular Dynamics simulations of a coarse-grained model for water mixtures containing up to 25% methanol, we show that, for appropriate pore sizes, water tends to occupy the center of the pore. In contrast, methanol's apolar moiety accumulates near the hydrophobic walls. Additionally, modifying the pore's width leads to a non-monotonic change in the diffusivity of each component. However, water always diffuses faster than methanol, implying that it should be possible to identify an optimal configuration for water-methanol separation based on physical mechanisms. Our calculations indicate that one of the more effective pore sizes, 12.5{\AA}, is also mechanically stable, minimizing the energy cost of a possible filtering membrane.