Graphene-Based Nanomaterials for the Remediation of Neonicotinoid Pesticides and Their Transformation Products: Mechanistic Insights and Solvent-Driven Behavior

The persistence of neonicotinoids in the aquatic environment and their complex transformation processes pose a major challenge for water treatment. In this study, advanced computational modeling is used to evaluate the adsorption mechanisms and thermodynamics of the five most commonly used neonicotinoids (acetamiprid, imidacloprid, clothianidin, thiacloprid and thiamethoxam) and 19 of their transformation products on graphene-based nanomaterials. While pristine graphene effectively removes neonicotinoids via electrostatic interactions and the solvophobic effect, the oxygen functional groups of graphene oxide enable hydrogen bond-driven uptake, albeit with reduced stability. Crucially, we find a material-dependent trade-off between toxicity and adsorption, i.e. structural changes in the transformation products (e.g., the loss of electron-withdrawing nitro/cyano groups) simultaneously reduce the affinity of the nanomaterial and increase toxicity to vertebrates. The solvent environment proves to be a critical technical parameter, with n-octanol reducing adsorption stability compared to water. This finding enables sustainable regeneration of adsorbents, but requires protective measures to prevent desorption from spent adsorbents in organic-rich environments. The adsorption data set generated and the molecular insights gained promote the rational design of nanomaterial-based adsorbents and support the development of hybrid treatment technologies technologies that can address complex contaminant mixtures.