Solvent Extraction of Several Divalent Metal Ions with 4-Isopropyltropolone into Chloroform in the Absence and Presence of Trioctylphosphine Oxide

Abstract

Abstract The solvent extraction of divalent metal ions, manganese(II), cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) in aqueous 0.1 mol dm−3 sodium nitrate solutions with 2-hydroxy-4-(1-methylethyl)-2,4,6-cycloheptatrien-1-one (4-isopropyltropolone; Hipt) into chloroform was studied in the absence and presence of trioctylphosphine oxide (TOPO). When the concentration of metal ions (M2+) was 1 × 10−5 to 1 × 10−4 mol dm−3 in the initial aqueous solutions, the extracted species of the metal ions in the absence of TOPO were only the mononuclear complex, M(ipt)2, with copper(II); these species were both the mononuclear complex, M(ipt)2, and the mononuclear self-adduct complex, M(ipt)2·Hipt, with zinc(II); they were both the mononuclear complex, M(ipt)2, and the dinuclear complex, M2(ipt)4, with cobalt(II) and cadmium(II); and they were predominantly the dinuclear complex, M2(ipt)4, with nickel(II) and manganese(II). It was also found that the extraction of manganese(II), cobalt(II), nickel(II), zinc(II), and cadmiun(II) was enhanced when TOPO was added into the organic phase. This was explained in terms of the formation of mononuclear adduct complex, M(ipt)2TOPO, from M(ipt)2, M(ipt)2·Hipt, and/or M2(ipt)4. The extraction constants for those species were determined. The extractability and the tendency to form dinuclear complexes are discussed.