Solvent extraction with di(2-ethylhexyl)phosphoric acid; A correlation between selectivity and the structure of the complex |
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| Affiliation: | 1. Scientific Research Institute of Heart Surgery and Organ Transplantation, Bishkek, Kyrgyzstan;2. National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan;3. Research–Clinical Center of Cardiac Surgery and Transplantation, Taraz, Kazakhstan |
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| Abstract: | Distribution coefficients for a number of divalent transition metal ions and for iron (III) between aqueous phases of constant ionic strength and an organic phase containing 30% sodium di-(2-ethylhexyl)phosphate (D2ENa) have been measured with variable temperature. Three distinct types of extraction have been observed and have been correlated with the structures of the complexes and the predictions of ligand field theory. For cobalt(II) a 6-coordinate derivative Co(D2E)2(H2O)2 has been postulated to explain the thermochromism observed in the cobalt extraction at low cobalt concentrations. This reaction has been studied at temperatures between 20°C and 100°C and values of 48·3 kJ mol−1 and 148 J mol−1°C−1 for ΔH and ΔS respectively have been estimated for the octahedral → tetrahedral conversion. The importance of the entropy effect for the extraction of manganese(II), iron(II) and cobalt(II) is stressed. |
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