Polystyrene microplastics (PS) are emerging contaminants of increasing environmental concern owing to their persistence and widespread distribution in aquatic ecosystems. In this study, the adsorption behavior of PS on graphene nanosheets functionalized with hydroxyl (–OH), carboxyl (–COOH), and trifluoromethyl (–CF₃) groups was systematically investigated using a multiscale computational approach combining density functional theory (DFT), grand canonical Monte Carlo (GCMC), and molecular dynamics (MD) simulations. The results demonstrate that surface functionalization markedly affects PS adsorption by modifying the electronic characteristics of the graphene surface and the nature of adsorbate–surface interactions. DFT calculations revealed that COOH-functionalized graphene exhibits the strongest intrinsic affinity toward PS. However, GCMC simulations showed that its adsorption capacity is significantly diminished in aqueous environments because of competitive water adsorption and hydration-layer formation. In contrast, the hydrophobic CF₃-functionalized surface achieved the highest PS uptake by minimizing water competition and maximizing the availability of adsorption sites. “MD simulations further indicated that PS diffusion is highest in the CF₃-functionalized AC model, whereas lower mobility was observed particularly in the OH-functionalized system, demonstrating that surface functionalization and structural accessibility influence PS dynamics within the modeled porous structures .These findings highlight the critical role of water-mediated effects in governing microplastic adsorption and identify CF₃ functionalization as an effective strategy for enhancing PS removal. The study provides molecular-level insights that can guide the rational design of advanced carbon-based adsorbents for water purification applications.
