Functionalization of Mesoporous Carbon Materials for Selective Separation of Lanthanides under Acidic Conditions.

New functional mesoporous carbon sorbents were successfully synthesized to overcome some issues of solid-liquid extraction (e.g., selectivity, extraction capacity, and reusability under acidic conditions) in production of pure lanthanides (Ln). Wet-oxidation technique was performed to increase the surface reactivity of pristine ordered mesoporous carbon (OMC), and, in a second step, a surface modification using diglycolamide-based (DGA-based) selective ligands toward Ln was performed. Two types of ligands were tested: the first contains a long spacer (e.g., between carbon support and chelating function), and the second has a shorter one. These materials have been characterized by X-ray photoelectron spectroscopy (XPS), low-angle X-ray diffraction (XRD), thermogravimetric analysis, nitrogen sorption, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). These analyses confirmed that the carbon mesostructure was maintained after organo-functionalization of the surface and showed the covalent attachment of selective ligands. These new materials, and especially the system with a short spacer between the ligand and the surface, reveal unique Ln selectivity profiles with improved extraction performances for the recovery of lanthanides, in terms of both selectivity and adsorption capacity, and unprecedented stability under acidic conditions.