Graphene Quantum Dots in Two-Dimensional Confined and Hydrophobic Space for Enhanced Adsorption of Nonionic Organic Adsorbates

Graphene quantum dots (GQDs) should be expected to become an alternative material for removal of several pollutants from water due to their lager specific surface areas, abundant functional groups, and excellent biocompatibility. However, very little effort focused on adsorption behavior as higher water solubility of GQDs. Here we not only showed highly efficient adsorption of GQDs confined in two-dimensional (2D) hydrophobic space for nonionic organic adsorbates but also systematically explored the interaction between adsorbents and adsorbates. The cointercalation of citrate and dodecyl sulfate (SDS) into interlayer of layered double hydroxides (LDHs) was prepared by hydrothermal method to obtain GQDs confined in 2D hydrophobic space. The adsorption efficiency of (GQDs+SDS)-LDHs for 2,4,6-trichlorophenol is 80%, which is higher than that of GQDs-LDHs (15%) and SDS-LDHs (40%). Adsorption mechanism showed the synergistic effects of hydrophobic, hydrogen bond, and pp interaction were responsible for adsorption of nonionic organic adsorbates by (GQDs+SDS)-LDHs. As a result, this work not only solved the problems of high water solubility and aggregation of GQDs by immobilizing and dispersing GQDs in 2D confined and hydrophobic interlayer of LDHs but realized highly efficient adsorption of GQDs-based complex for nonionic organic adsorbates. Therefore, this strategy might be expanded to adsorb a wide variety of adsorbates by employing the structure designable ability of GQDs-LDHs-based composites.