Determination of stability constants of U(VI)-Fe(III)-citrate complexes.
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 beta1,1) 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 1:1:1 and 1:1:2 ternary species with stability constants (log beta) of 17.10+/-0.41 and 20.47+/-0.31, respectively, at I= 0.
Kantar
Cetin
C
Department of Environmental Engineering, Mersin University, Ciftlikkoy, 33342 Mersin, Turkey.
Gillow
Jeff B
JB
Harper-Arabie
Ruth
R
Honeyman
Bruce D
BD
Francis
Arokiasamy J
AJ
D019343:Citric Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007475:Ion Exchange Resins / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry*; D008956:Models, Chemical; D012044:Regression Analysis; D014501:Uranium / Q000737:chemistry*
D007475:Ion Exchange Resins; D046911:Macromolecular Substances; D019343:Citric Acid; D014501:Uranium; D007501:Iron