Work

Enhanced selectivity of water-alcohol with cross-linked polybenzimidazole (PBI) membrane: Insight from molecular dynamics simulation

Year: 2025

Type: article

Abstract: Designing advanced cross-linked membranes with selective solute rejection and high water permeability remains challenging due to complex molecular-level diffusion. In this study, we leverage systematic molecular dynamics (MD) simulations to engineer polybenzimidazole (PBI) membranes through controlled cross-linking using α, α'-Dichloro-p-xylene (DCX) at four distinct cross-linking densities. We also investigate the diffusion and dissolution processes of water-alcohol molecules within these cross-linked PBI membranes. The influence of the target structure on separation performance is estimated using parameters such as fractional free volume (FFV), end-to-end distance, pore size distribution (PSD), and radial distribution function (RDF). As the degree of cross-linking increased, the fractional free volume dropped from 16.33 % to 10.76 %, and the pore size distribution decreased from 3.42 Å to 2.48 Å. These changes reduced defects, potentially enhancing molecular screening performance compared to the pristine PBI. Water-ethanol selectivity increases from 8.82 to 57.34, while water-isopropanol selectivity surges by two orders of magnitude. The study also investigated the solubility coefficients of water-alcohol in the membrane. The results indicated that the cross-linked PBI membrane has a significantly higher affinity for water molecules compared to alcohol molecules. Cross-linked PBI membranes preferentially sorb water by occupying hydrogen-bonding sites, sterically restricting alcohol permeation and enabling high water/alcohol selectivity. This provides theoretical evidence that cross-linked PBI membranes can enhance selective water-alcohol separation.

Source: Journal of Water Process Engineering

DOI: 10.1016/j.jwpe.2025.108784

Authors: Zhiwei Lv, Shujuan Jia, Zehui Zhang

Institutions: Hebei University of Engineering, Nanjing University of Science and Technology

Language: English

Topic: Membrane Separation and Gas Transport

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

SDG: Clean water and sanitation

Open Access status: hybrid

Estimated APC paid: $3,350