Layered graphene oxide membrane for heavy metal separation via molecular dynamics simulation

Purification of water and industrial wastewater, especially those containing toxic metals, is a critical challenge for developing societies. Nano membranes, including two-dimensional graphene oxide nanomaterials, have recently gained prominence as an alternative to traditional polymer membranes. However, the efficacy of these membranes for the removal of heavy metals has not been extensively studied. In this work, molecular dynamics simulation is used to investigate the performance of graphene oxide membranes, with the oxidation ratio of 20 %, for the removal of mercury and arsenic ions at a concentration of 0.5 M, via reverse osmosis at 200 Mpa pressure. Results demonstrate that graphene oxide membranes are effective for separating heavy metal ions while maintaining good water flow. The mechanism of water molecule passage through the graphene oxide membrane is also investigated by analyzing the structural images of water molecules between the layers, water density diagrams in the nanochannel, and the number of hydrogen bonds at various channel inter-layer distances. In addition, raising the temperature of the aqueous solution from 300 to 340 K increases the water flux and decreases ion rejection. Increasing the concentration of mercury and arsenic ions from 0.5 to 1 M in the feed water leads to decrease in water flux with the least impact on ion rejection. Furthermore, the influence of membrane geometry on its performance is also investigated. By comparing the cross-flow and dead-end geometries, it is found that the cross-flow geometry performs better than the dead-end geometry both in water flux and the removal efficiency of mercury and arsenic ions. The potential of graphene oxide membranes in the treatment of wastewater containing heavy metals is highlighted by these findings, which provide insights into optimizing their design and operational parameters. © 2024 Elsevier B.V.