▎ 摘　　要

Herein we present a sustainable and costeffective approach for the preparation of functionalized graphene nanosheets (GNs) directly from seaweed and deep eutectic solvents (DESs). The seaweed granules remained after the recovery of juice from fresh brown seaweed, Sargassum tenerrimum, was utilized as a raw material and DESs generated by the complexation of choline chloride and metal salts were employed as solvent and catalyst for the large scale and facile production of metal oxide functionalized GNs. Moreover considering the biological application of such GNs, where nontoxic nature of substrates is desirable, we have also evaluated the cytotoxicity of the functionalized GNs (Fe3O4/ Fe, Sno(2)/SnO/Sn, or ZnO/Zn-functionalized GNs), and most of them were found to be nontoxic against human lung carcinoma cells (A549). Thereafter, efficiency of these GNs was assessed for the removal of F- from fluoride contaminated groundwater (2.72-6.71 mg L-1) used for drinking purposes. After treatment with GNs, the concentration of fluoride was found to reduce to 0.36-1.69 mg L-1 (75-87% removal efficiency). Moreover, after recovery of GNs from the water, no significant contamination of metal ions was found in the remaining water. Thus, seaweed-derived nontoxic GNs can be utilized to produce safe drinking water with permissible fluoride content as per World Health Organization (WHO) norms.