Preparation of a Novel Macroporous Silica-based Diglycolamide Derivative-impregnated Polymeric Composite and its Adsorption Mechanism for Rare Earth Metal Ions

摘要

Diethylenetriaminepentaacetic acid (DTPA), a multi-dentate acidic chelating agent containing five carboxyl and three amine groups all capable of protonation, is a pentabasic acid. To separate minor actinide [MA(III)] and rare earth [RE(III)] elements effectively from a HNO 3 solution containing DTPA generated in the MAREC process, a functional polymeric composite impregnated with a novel macroporous silica-based diglycolamide compound, N,N,N′,N′ -tetraoctyl-3-oxapentane-1,5-diamide (TODGA), was prepared. Thus, the impregnated functional polymeric composite (TODGA/SiO 2 -P) was obtained by impregnating and immobilizing TODGA molecules in the pores of the SiO 2 -polymer (SiO 2 -P) particles (ca. 50 μm diameter) via a vacuum sucking technique. The effects of H + ions within the concentration range 0.01–3.0 M and of NO 3 − ions within the range 0.1–3.115 M on the adsorption of RE(III) ions onto TODGA/SiO 2 -P were investigated at 298 K. It was found that in the presence of 0.05 M DTPA, the DTPA species strongly affected the adsorption of RE(III) ions. The adsorption capability of TODGA/SiO 2 -P depended on the competitive reactions of RE(III) ions with two species, viz. H 4 DTPA − and H 2 DTPA 3− . The distribution coefficient (K d ) for RE(III) ions increased with increasing NO 3 − concentration, with one RE(III) ion reacting with two NO 3 − ions. The adsorption mechanism of RE(III) ions towards the TODGA/SiO 2 -P polymeric composite in HNO 3 solution containing 0.05 M DTPA was suggested as: RE 3 + + H 4 DTPA - + 2 NO 3 - + 3 TODGA / SiO 2 - P ⇋ RE ( H 4 DTPA ) ( NO 3 ) 2 ⋅ 3 TODGA / SiO 2 - P The formation of H 4 DTPA − and RE(H 4 DTPA)(NO 3 ) 2 which are both capable of adsorbing with TODGA/SiO 2 -P was the main reason why RE(III) ions exhibited such significant adsorption in the presence of 0.05 M DTPA.