https://doi.org/10.15255/KUI.2002.045
Published: Kem. Ind. 52 (7-8) (2003) 319–325
Paper reference number: KUI-45/2002
Paper type: Conference paper
Download paper:  PDF

Effect the Mole Fraction of Crown Ethers with Trioctylphosphine Oxide on Extraction of Pb(II) Ion

J. Budimir, H. Pašalić, R. Kubiček and S. Marić

Abstract

Solvent extraction represents the best of all the various separation techniques because of its simplicity, rapidity, applicability to various concentration ranges and purity of products. Moreover, in synergistic system the extracting power of the mixture exceeds the sum of the extracting powers of its components. Complexation between the crown ethers and metal cation has been studied by different methodes. It has been found that the crown ethers have a capacity to form stable stoichiometric complexes with certain metal picrates. However, distribution coefficients for metals were very low, although larger than those observed with mineral acid anions. The positive results were obtained in studies with combination of crown ethers as useful coordinative synergist, with other extractants like alkyl amines, alkyl phosphates, phosphine oxides, sulfonic and phosphoric acids. Although a recent literature has been accumulated in the last forty years, relatively small number of papers is concerned with synergistic extraction of Pb(II) ions. The solvent extraction of Pb(II) ions from aqueous solution containing picrate anion and HNO3 with various crown ethers; 18-crown-6 (18C6), dicyclohexano-18- crown-6 (DC18C6) and dibenzo-18-crown-6 (DB18C6), tri-n-octylphosphine oxide (TOPO) and their mixture in benzene has been studied in this paper. The differential anodic stripping pulse voltammetric method ( DASPV) has been used for determination of concentration of Pb(II) ions after back extraction at 25 ± 0.05 °C. The results show that extractability of Pb(II) ions decreases in the order: n18C6 > nDB18C6 > nDC18C6 = nTOPO. The effect produced by mixing TOPO with crown ether is synergetic, the distribution ratio of the mixture is greater than the sum of the distribution ratio of the individual components. The synergism of ligands mixture was explained by the means of adduct formation in the organic phase and depends on substituents on crown ether and its amount fraction. It has been found that the synergistic effects increases in the following order: nDC18C6 + nTOPO < nDB18C6 + nTOPO < n18C6 + nTOPO

This work is licensed under a Creative Commons Attribution 4.0 International License

Keywords

lead, crown ethers, trioctylphosphine oxide, DA stripping pulse voltammetry