| Mineral: |
Ferrihydrite |
| Reference: |
WDPWX94 |
| SCM Type: |
DDL - Diffuse Double Layer |
| Ligand: |
CO3<2->
- carbonate
|
| Site Type: |
»Fe-OH |
| Equation: |
»Fe-OH + 2 CO3<2-> + 2 H<1+> ⇔ »Fe-HCO3 + H2O |
| LogK: |
19.595 LogK°I=0 (Conversion to I = 0): 20.67
LogK2.31 nm−2 (SSD-normalized): 21.59
|
| Experiment: |
Potentiometric Titration |
| Ionic Strength: |
0.1 mol/L
NaNO3
|
| pH Range: |
3.5-9 |
| Ligand Concentration Range: |
4.6E-6M C. 8.7E-4M Fe mol/L |
| Fit Method: |
FITEQL |
| Comment: |
raw data from [ZGSR87]; closed system; reaction constants for weak and strong surface sites assumed to be equaextrapolation to infinite dilution leaves log K unchanged, pCO2: air - 1%; original reaction equation in the study: »Fe-OH + H2CO3 = »Fe-HCO3 + H2O with logK = 2.9, formation constants: logK1 = -6.366 for the reaction H2CO3 = H<1+> + HCO3<1->[FNK96], logK2 = -10.329 for HCO3<1-> = H<1+> + CO3<2-> [GFFGN03] --> so for H2CO3 = 2H<1+> + CO3<2-> the logK = -16.695 |
| |
