Temperature effect on the synergic extraction of europium by thenoyltrifluoroacetone in the presence of heterocyclic bidentate amines from acetate buffer solutions

Abstract

Temperature effect on the synergic extraction of Eu(III) by thenoyltrifluoroacetone (HTTA) in the presence of 2,2-bipyridyl(bipyr) and 1,10-phenanthroline (phen) from sodium acetate buffer solution at pH 4.20 has been investigated. Extractions were carried out at 15, 25, and 35°C. It was observed that the increasing temperature favours the extraction of Eu(III) by HTTA alone while the reverse is true for synergic extractions. The extraction data indicate the formation of synergic adducts containing only one molecule of the bidentate amine i.e. Eu(TTA)3. B where B=bipyr or phen. The synergic reaction is favoured by the enthalpy changes alone. Thermodynamic parameters suggest a mechanism for the synergic extraction which involves complex formation with an increase or expansion of the coordination number of the central metal atom. Larger synergic and enthalpy changes observed for phen as compared to bipyr are probably due to the cis position of its N-atoms readily available for chelate ring formation.