D2EHPAによる種々の金属イオンの溶媒抽出におよぼす非水溶媒の影響

Abstract

Extraction of metal ions from the aqueous phase containing non-aqueous solvents such as dimethyl formamide (DMF), dimethyl sulfoxide (DMSO) and acetonitrile (AN) was investigated by using di-2-ethylhexylphosphoric acid (D2EHPA) as an extractant. The organic phase was a binary solution of D2EHPA and n-hexane, or D2EHPA and toluene, while the aqueous phase was a three-component solution of metal salt, non-aqueous solvent and water. Metal ions used for this purpose were Cr(III), Fe(III), Al, Cu, Ni, Co, Mg and Ag.The extraction of metal ions is strongly affected by the addition of non-aqueous solvent. The effect is dependent on the kinds of non-aqueous solvent, the amounts of non-aqueous solvent and the kinds of metal ion. The extraction behavior in the presence of non-aqueous solvents are classified into the following three groups: (1) extraction of Cu, Ni and Co increases by adding DMSO and DMF less than 50 vol% and then decreases by the addition more than 50 vol%, (2) extraction of Ag, Cr and Fe decreases with an increasing addition of DMSO and DMF, irrespective of its amount and (3) extraction of Mg and Al increases with an increasing addition of DMSO and DMF, regardless of its amount. The addition of AN does not cause a great change in the extraction of metal ions except Al and Ag, but the extraction of Ag is remarkably decreased by the addition of AN. The above extraction behavior may be explained by the complexing ability of non-aqueous solvents, the increase in the distribution amount of the extractant and extract in the aqueous phase, and the interaction between the extractant and non-aqueous solvents in the organic phase due to the dissolution of non-aqueous solvents in the organic phase.