Rare earth element (REE) is a strategic metal resource, heavy REE owns higher economic and strategic value compared with light rare earth elements. However, it is a great challenge for the separation of heavy rare earth ion efficiently in the solution with mixed rare earth ions due to the similar physicochemical properties of heavy and light REE. In this paper, the diglycolamide (DGA) modified silica adsorbents were prepared and applied to the selective adsorption of heavy earth ion Dy 3+ . The structure of DGA on the silica surface was regulated during the modifying processes to obtain DGA b -SiO 2 and DGA s -SiO 2 adsorbent, which was verified by FTIR and NMR characterization results. The adsorption results showed that the DGA b -SiO 2 adsorbent owned a much higher distribution coefficient ( K d ) value for the selective adsorption of Dy 3+ than the DGA s -SiO 2 adsorbent. The higher adsorption selectivity is likely due to the fixed carbon chain of the DGA group on the surface of DGA b -SiO 2 adsorbent formed rigid spatial structures of the oxygen atoms, which will be favorable for the selective coordination of Dy 3+ . Besides its effectiveness in adsorption behavior, the DGA b -SiO 2 adsorbent displayed excellent stability. The K d value of DGA b -SiO 2 for Dy 3+ selective adsorption maintained a high level after four successive recycling runs. The adsorption kinetics results displayed that the adsorption of Dy 3+ followed pseudo-second-order kinetic, and the adsorption process fitted the Langmuir isotherm model. Additionally, the same adsorption rules for the rare earth ions were observed over DGA-KIT-6 adsorbent, indicating the high universality of the surface modification to the adsorbent support, which will provide an intentional reference for the surface modification to other adsorbent support.
Yi Wu,Anqi He,Da Li,Limin Yang,Yizhuang Xu,Yukihiro Ozaki,Isao Noda
This study investigates single-crystal structures of Lu3+/erythritol and nine rare earth–glycerol complexes, revealing deprotonation of normally inert OH groups via μ2-bridging (so-called DIOμ2 phenomenon). The pH drops upon alditol addition correlate with the deprotonation extent, showing increased deprotonation with decreasing lanthanide ionic radius (lanthanide contraction) and exceptionally high deprotonation for Sc3+. In all the rare earth/alditol complexes with the DIOμ2 phenomenon, two μ2-bridges merge into an M2O2 cluster (M is a rare earth ion) that is not very stable due to the Coulombic repulsion between two M3+ and between two O–. To stabilize the M2O2 cluster, the formation of more auxiliary five- and six-membered chelating rings between rare earth ions and alditol ligands is needed. Increment of the number of auxiliary five- and six-membered chelating rings favors the DIOμ2 reaction. This is the reason why the DIOμ2 reaction shows a progressively enhanced tendency when the alditol ligands change from myo-inositol to glycerol to erythritol and galactitol. The reaction is endothermic, as an increased temperature enhances deprotonation. The above results may be useful in the rational design of catalysts that efficiently activate inert OH bonds and facilitate related chemical processes.
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