Isotope Fractionation of Iron(III) in Chemical Exchange Reactions Using Solvent Extraction with Crown Ether

Toshiyuki Fujii (1, 2) , Frédéric Moynier (1) , Philippe Telouk , Francis Albarède (1)

1 LST - Laboratoire de Sciences de la Terre
2 Research Reactor Institute

This work reports on the chemical isotope fractionation of Fe(III) by a solvent extraction method with a crown ether of dicyclohexano-18-crown-6. The 56Fe/54Fe and 57Fe/54Fe ratios were analyzed by multiple-collector inductively coupled plasma mass spectrometry. We determined the dependence of the isotope enrichment factors () on the strength of HCl. The relative deviation of the 56Fe/54Fe ratios relative to the unprocessed material (104 56) increases from -15.3 to -6.3 with [HCl] increasing from 1.6 to 3.5 mol/L. Likewise, 104 57 increases from -22.8 to -9.6 under the same conditions. The correlation between 56 and 57 is mass dependent within the errors. The observed fractionation was broken down into the effects of competing extraction reactions and of a reaction between Fe(III) species (FeCl2+ and FeCl3) in the aqueous phase. We found that the isotope fractionation between the Fe(III) species is mass dependent, which we confirmed by calculating the reduced partition function ratios.

Domaines: Géochimie; Milieux et Changements globaux

Toshiyuki Fujii, Frédéric Moynier, Philippe Telouk, Francis Albarède. Isotope Fractionation of Iron(III) in Chemical Exchange Reactions Using Solvent Extraction with Crown Ether. The Journal of physical chemistry, 2006, pp.11108-11112. ⟨10.1021/jp063179u⟩. ⟨hal-00098305⟩