Extraction of Soft Metals in Acidic Solution by Hydrophobic Analogs of N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethylenediamine (TPEN)

摘要

N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethylenediamine (TPEN) is a hexdentate ligand that encapsu-lates selectively soft metals classified by the Pearson’s HSAB principle. Four hydrophobic TPEN analogs, N,N,N',N'-tetrakis (2-methylpyridyl)-1, 2-phenylenediamine (TPBN), N,N,N',N'-tetrakis (2-methylpyridyl)-1, 8-naphtalenediamine0 (TPN18N), N,N,N',N'-tetrakis (2-quinlinylmethyl)-1, 2-ethylenediamine (TQEN) and N,N,N',N'- etrakis [4- (2-butyloxy)-2-pyridinyl- methyl]-1,2-ethylenediamine (TBPEN), were synthesized for in-creasing the extractability of TPEN in the acidic solution. The extraction of a soft metal, Cd(II), with these TPEN analogs was tested in the pH range of 1.0 to 4.0. TPEN, TPBN and TPN18N little extracted Cd(II) in the acidic solution. On the other hand, TQEN and TBPEN extracted Cd(II) from the highly acidic solution less than pH 2. These results suggest that the increase in the hydrophobicity of TPEN analog introducing hydrophobic groups to four pyridyl groups, such as TQEN and TBPEN, is valid for improving the extraction of Cd(II) in the acidic solu-tion. The use of TBPEN is especially effective for improving the extraction of Cd(II) and the extraction percent showed 100% even for the extraction of Cd(II) in the acidic solution at pH 1.