Determination of stability constants of U(VI)-Fe(III)-citrate complexes


KANTAR Ç., Gillow J., Harper-Arabie R., Honeyman B., Francis A.

ENVIRONMENTAL SCIENCE & TECHNOLOGY, vol.39, no.7, pp.2161-2168, 2005 (Peer-Reviewed Journal) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 39 Issue: 7
  • Publication Date: 2005
  • Doi Number: 10.1021/es048852c
  • Journal Name: ENVIRONMENTAL SCIENCE & TECHNOLOGY
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.2161-2168

Abstract

Ion-exchange experiments were performed to evaluate the formation of the uranium-citrate and uranium-iron-citrate complexes over a wide concentration range; i.e., environmentally relevant concentrations (e.g., 10(-6) M in metal and ligand) and concentrations useful for spectroscopic investigations (e.g., 10(-4) M in metal and ligand). The stability of the well-known uranium-citrate complex was determined to validate the computational and experimental methods applied to the more complex system. Values of the conditional stability constants for these species were obtained using a chemical equilibrium model in FITEQL. At a pH of 4.0, the stability constant for uranium-citrate complex (log beta(1,1)) was determined to be 8.71 +/- 0.6 at I = 0. Analysis of the results of ion-exchange experiments for the U-Fe-citric acid system indicates the formation of the 1:11:11 and 1:11:2 ternary species with stability constants (log beta) of 17.10 +/- 0.41 and 20.47 +/- 0.31, respectively, at I = 0.