Application of deep eutectic solvent for conjugation of magnetic nanoparticles onto graphene oxide for lead(II) and methylene blue removal

Deep eutectic solvents (DESs) have emerged as a substitute for ionic liquids with lower cost and enhanced biodegradability. The most common class of DES refers to a mixture of a quaternary ammonium or phosphonium salt and a hydrogen bond donor (e.g., carboxylic acid) with a melting point lower than that of individual components. DESs have recently shown promise for surface modification of graphene oxide (GO) nanosheets with different functional groups. We hypothesize that such surface functionalization of GO (and other carbon nanomaterials) with DESs can provide a new route to conjugate metallic nanoparticles onto GO surfaces (and similar). Here, we used a typical DES, based on choline chloride and urea, for the conjugation of pre-synthesized Fe3O4 nanoparticles onto GO nanosheets at different GO:Fe3O4 ratios. Physicochemical characterization not only confirmed the ability of DES to prepare DES/GO-Fe3O4 nanohybrids successfully, but also evidenced the influence of DES on the homogeneity and size distribution of Fe3O4 nanoparticles in these nanohybrids. DES/GO-Fe3O4 nanohybrids can perform better than both GO and Fe3O4 as adsorbents for organic dyes (methylene blue, MB) and heavy metals (Lead (II)). However, depending on the contaminant type, the contaminant removal performance varied differently for DES/GO-Fe3O4 nanohybrids with different ratios.