Molecular simulation of adsorption behavior for phenol aqueous solution into layered graphene oxides

Abstract

Graphene oxide (GO) adsorbents possess layered structures with nanoscale interlayer channels, which have been proposed as effective adsorbents for the removal of harmful phenol from aqueous solutions. However, the relevant adsorption process and behavior remain largely unexplored, and, particularly, the interlayer insertion and interaction mechanism need to be clarified. Herein, molecular dynamics simulation was performed to comprehensively investigate the dynamics process and interaction for phenol adsorption into GO interlayers. It is theoretically demonstrated that the adsorption process is thermodynamically spontaneous. The time evolution of molecular insertion amounts and interaction energy were applied to describe the dynamics process, in which different adsorption stages were revealed. Our simulation findings show that the interlayer phenol movement is the rate-limiting step in the adsorption process. Furthermore, by analyzing the interlayer structure and morphology, it is illustrated that the phenol molecules are discretely and disorderly scattered with a lying-down conformation within the GO interlayer. The adsorption interaction is the combination of the π–π and hydrogen-bonding interactions, in which the π-π interaction provides a dominant contribution. The effects of interlayer widths and surface oxidization degrees were thoroughly investigated. Our simulations provide new insight and useful guidance for the development of GO adsorbents.