Carbonate Complexation of Yttrium and the Rare Earth Elements in Natural Waters

Authors

Yu-Ran Luo, University of South Florida
Robert H. Byrne, University of South FloridaFollow

Document Type

Article

Publication Date

2004

Digital Object Identifier (DOI)

https://doi.org/10.1016/S0016-7037(03)00495-2

Abstract

Potentiometric measurements of Yttrium and Rare Earth Element (YREE) complexation by carbonate and bicarbonate indicate that the quality of carbonate complexation constants previously obtained via solvent exchange analyses are superior to characterizations obtained using solubility and adsorptive exchange analyses. The results of our analyses at 25°C are combined with the results of previous solvent exchange analyses to obtain YREE carbonate complexation constants over a wide range of ionic strength (0 ≤ I ≤3 molal). YREE carbonate complexation constants are reported for the following equilibria, M³⁺+nHCO₃⁻⇌M(CO₃)_n³⁻²ⁿ+nH⁺, where n = 1 or 2. Formation constants written in terms of HCO₃⁻ concentrations require only minor corrections for ion pairing relative to the corrections required for constants expressed in terms of CO₃²⁻ concentrations. Formation constants for the above complexation equilibria, _CO3^Hβ₁=[MCO₃⁺][H⁺][M³⁺]⁻¹[HCO₃⁻]⁻¹ and _CO3^Hβ₂=[M(CO₃)₂⁻][H⁺]²[M³⁺]⁻¹[HCO₃⁻]⁻², have very similar dependencies on ionic strength because the reaction MCO₃⁺+HCO₃⁻⇌M(CO₃)₂⁻+H⁺ is isocoulombic. Potentiometric analyses indicate that the dependence of log_CO3^Hβ₁ and log_CO3^Hβ₂ on ionic strength at 25°C is given as (A)logCO3Hβn=logCO3Hβn0−4.088I0.5/(1+3.033I0.5)+0.042I">logCO3Hβn=logCO3Hβn0−4.088I0.5/(1+3.033I0.5)+0.042I where _CO3^Hβ_n⁰ denotes a formation constant at 25°C and zero ionic strength. Recommended values for log_CO3^Hβ₁ and log_CO3^Hβ₂⁰, expressed in the form (element, −log_CO3^Hβ₁⁰, −log_CO3^Hβ₂⁰), are as follows: (Y, 2.85, 8.03), (La, 3.60, 9.36), (Ce, 3.27, 8.90), (Pr, 3.10, 8.58), (Nd, 3.05, 8.49), (Sm, 2.87, 8.13), (Eu, 2.85, 8.03), (Gd, 2.94, 8.18), (Tb, 2.87, 7.88), (Dy, 2.77, 7.75), (Ho, 2.78, 7.66), (Er, 2.72, 7.54), (Tm, 2.65, 7.39), (Yb, 2.53, 7.36), (Lu, 2.58, 7.29).

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Geochimica et Cosmochimica Acta, v. 68, issue 4, p. 691-699

Scholar Commons Citation

Luo, Yu-Ran and Byrne, Robert H., "Carbonate Complexation of Yttrium and the Rare Earth Elements in Natural Waters" (2004). Marine Science Faculty Publications. 1739.
https://digitalcommons.usf.edu/msc_facpub/1739