Crown ethers as synergists in the extraction of trivalent lanthanoids with 3-phenyl-4-(4-fluorobenzoyl)-5-isoxazolone

Abstract

Summary This paper highlights the results of investigations carried out on the extraction of lanthanoids such as Nd(III), Eu(III) and Tm(III) from nitrate solutions into chloroform with 3-phenyl-4-(4-fluorobenzoyl)-5-isoxazolone (HFBPI) in the presence and absence of various crown ethers (CE); 18-crown-6 (18C6), dicyclohexano-18-crown-6 (DC18C6), benzo-18-crown-6 (B18C6) and dibenzo-18-crown-6 (DB18C6). The results demonstrated that these trivalent metal ions were extracted into chloroform as Ln(FBPI)3 with HFBPI alone and as Ln(FBPI)3·CE in the presence of a CE. The equilibrium constants of the above extracted complexes deduced by a non-linear regression analysis were found to increase monotonically with a decrease in ionic radii of these metal ions. The addition of a CE to the metal chelate system significantly improves the extraction efficiency of these metal ions. The complexation strength of trivalent lanthanoids with various CEs follows the order: DC18C6 > 18C6 > B18C6 > DB18C6. Solid complexes of Eu(III) with HFBPI alone and with mixtures of HFBPI and various crown ethers have been isolated and characterised by IR and 1H NMR spectral data to further clarify the nature of the extracted complexes.