Synergistic Extraction of Copper(II) and Zinc(II) with Tributyl Phosphate and Crown Ether

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Abstract
The solvent extraction of copper(II) and zinc(II) with 12-crown-4 (12C4) or 15-crown-5 (15C5) as picrates into chloroform containing tributyl phosphate (TBP) has been studied. The following conclusions have been reached. i) Even in the presence of TBP which is more basic than crown ether, either copper(II) or zinc(II) is extracted in association with 2 moles of 12C4 or 15C5. ii) The crown ether complex of either copper(II) or zinc(II) forms 1 : 1 : 1 (metal(II): crown ether: TBP) stoichiometric adducts in chloroform. iii) The 12C4 complex of either copper(II) or zinc(II) forms more stable adducts with TBP than the 15C5 complex. iv) The extraction of the metal (II) with 15C5 and TBP is better than that of 12C4 and TBP. v) The copper(II) complex with 12C4 or 15C5 forms more stable TBP adducts than those from zinc(II) complex.