Selectivity of novel PAMAM dendrimers modified with salicylaldehyde and their extraction/separation performance on Zr(Ⅳ) and Hf(Ⅳ)

To design some excellent extractants for the separation of Zr(Ⅳ) and Hf(Ⅳ), a novel set of polyamidoamine dendrimers peripherally modified with salicylaldehyde (Abbreviated as PAMAM-SA) have been synthesized. UV-vis absorption and fluorescent spectrometry were used to study the selectivity of G.1.0, G2.0, G3.0 and G4.0 PAMAM-SA on Zr(Ⅳ) and Hf(Ⅳ) compared with other metal ions, and their extraction/separation performance on Zr(Ⅳ) and Hf(Ⅳ) was also investigated under different pH solutions. The results show that these dendrimers have superior selectivity on Zr(Ⅳ) and Hf(Ⅳ) as compared with Ca2+, Mg2+, Fe3+and Ni2+ ions. The binding stoichiometry of G1.0, G2.0, G3.0 and G4.0 PAMAM-SA dendrimers with Zr(Ⅳ) is 1:4, 1:8, 1:10, 1:16 molar ratio determined by fluorescent titration respectively and the molar ratio of these dendrimers with hafnium is similar to that of zirconium. Both of the maximum extraction efficiency (EE%) on Zr(Ⅳ) and the separation coefficient (βZr/Hf) are following the order of G2.0-PAMAM-SA > G1.0-PAMAM-SA > G3.0-PAMAM-SA > G4.0-PAMAM-SA, and the maximum EE% on Zr(Ⅳ) is up to 98.9% and furthermore the βZr/Hf is 1.52 for G2.0-PAMAM-SA at lower acid concentration compared with the reported extractants. The favorable higher EE% and βZr/Hf indicate that G2.0-PAMAM-SA may be potentially employed as a highly selective and efficient extractant to enhance separating zirconium from hafnium.