Models for association of metal ions with heterogeneous environmental sorbents. 1. Complexation of Co(II) by leonardite humic acid as a function of pH and NaClO{sub 4} concentration
- Oregon State Univ., Corvallis, OR (United States)
- Pacific Northwest Lab., Richland, WA (United States)
A discrete log K spectrum model has been developed to represent the binding of protons and Co(II) to leonardite humic acid (LHA) over a wide variation of solution composition: pH 4.5-9.5, [NaClO{sub 4}] 0.01-0.1 M, T{sub Co} 200 nM-500 $mu@M. The model is internally self-consistent over the range indicated without an explicit electrostatic term. The LHA was represented by four acid sites (HL{sub i} = H{sup +} + L{sub i}{sup -}) with a fixed pK{sub a} spectrum: pK{sub a} = 4, 6, 8, and 10. From the acid-base titration data, total concentrations of these sites and Na{sup +} binding constants (L{sub i}{sup -} + Na{sup +} = NaL{sub i}) were obtained. From Co{sup 21} binding as a function of pH, constants for the reaction L{sub i}{sup -} + Co{sup 21} = CoL{sub i}{sup +} were obtained. Total concentrations of sites and binding constants were similar to those expected from other studies. This discrete log K approach has been selected as the easiest way to parameterize multidimensional data (i.e., data with variations in many solution chemistry parameters) for subsequent application in transport models. 37 refs., 3 figs., 6 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 41640
- Journal Information:
- Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 4 Vol. 29; ISSN ESTHAG; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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