Polyethylenimine functionalized and scaffolded graphene aerogel and the application in the highly selective separation of thorium from rare earth

A polyethylenimine (PEI)-scaffolded and functionalized graphene aerogel, PEI-GO-AG, was prepared and utilized as a highly selective adsorbent for the extraction of thorium (Th) (IV) from three lanthanides (Ln) (III) elements. The three dimensional (3D)-porous structure of the adsorbent was established by the cross-linking effect of PEI via a one-step hydrothermal strategy and preserved by a freeze-drying treatment to avoid the collapse of the structure. The extractive efficiency of PEI-GO-AG displayed a sensitive dependence on the beginning mass ratio of PEI/graphene oxide (GO) in the hydrothermal step because of its significant influence on the hydrophilicity and the amounts of introduced binding sites of the adsorbent.. Besides, a density function theory (DFT)-based theoretical calculation was performed, confirming the higher stability of Th (IV)-PEI-GO-AG than that of Ln (III)-PEI-GO-AG. Ascribed to these contributions, the as-prepared adsorbent showed high selectivity towards Th (IV) among three Ln (III) elements. The separation factor ( SF ) values of Th (IV) to lanthanum (La) (III), europium (Eu) (III), and lutetium (Lu) (III) were SF Th/La  = 114.41, SF Th/Eu  = 52.75, and SF Th/Lu  = 107.81, respectively.