Metal Oxide (Core)/Graphene Oxide (Shell) Nanocomposites Show Enhanced Organic Adsorption in Aqueous Solution

The presence of organic contaminants (OCs) in aquatic systems is a growing threat to ecological/human health. Adsorption via graphene-based adsorbents is promising and we have previously fabricated 3D crumpled graphene balls (CGBs) that show robust performance due to their high affinity surface for OC adsorption. Since CGBs contain non-accessible surface due to the stacking of 2D graphene during synthesis, the goal of this research was to investigate the efficacy of maximizing the accessible surface by synthesizing a core (metal oxide)-shell (graphene oxide) composite (CSC) with various metal oxides. Metal Oxides reduce graphene stacking, expand the internal surface area, and boost the adsorptive function of CSCs. Particularly, with fumed SiO 2 or SiO 2 nanoparticles as the core, CSCs exhibit an enhanced Langmuir adsorption capacity (q m, normalized by % carbon) for an OC model, methylene blue (MB), achieving improvements of 60-86% compared to CGB, 3-4 fold compared to powder activated carbon (PAC) and 6-7 fold compared to granular activated carbon (GAC).  Furthermore, CSCs display rapid adsorption reaching equilibrium after 9-12 minutes of contact and remaining stable in wastewater effluent/surface water. A cost-efficiency comparison reveals CSCs achieve one ton of MB removal at similar or lower costs than that of PAC/GAC.