The extraction of perrhenate ion (ReO4-) with a podand-type nitrogen donor ligand, N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethylenediamine (TPEN), and its analogs were investigated. For the extraction of ReO4-with TPEN, the distribution ratio of Re increased with increasing the acidity of the aqueous solution in the pH(eq) range above 3.5 and decreased in the pH(eq) range below 3.5. These results indicate that ReO4- is extracted with protonated TPEN in the lower acidic solution; but the extraction of ReO4- is reduced by the increase in the solubility of multi-protonated TPEN into the highly acidic solution. Two hydrophobic TPEN analogs introducing alkyl groups, N,N,N',N'-tetrakis(2-pyridylmethyl)-dibutylethylenediamine (TPDBEN) and N,N,N',N'-tetrakis[4-(2-butyloxy)-2-pyridylmethyl] ethylenediamine (TBPEN), were synthesized in order to suppress the dissolution of TPEN into acidic solution. The distribution ratios of Re for hydrophobic TPEN analogs increased with increasing the acidity of the aqueous solution even in the pH(eq) range below 3.5 and achieved two order of magnitude higher than that for TPEN at about pH(eq) 2. (c) 2009 Elsevier B.V. All rights reserved.