wAbstract
@The oxygenation kinetics of nanomolar concentrations of Fe(II)
in aqueous solutions have been studied in the absence and presence
of millimolar concentrations of phosphate over the pH range 6.0-7.8.
At each phosphate concentration investigated, the overall oxidation
rate constant varied linearly with pH, and increased with increasing
phosphate concentration. A model based on equilibrium speciation
of Fe(II) was found to satisfactorily explain the results obtained.
From this model, the rate constants for oxygenation of the Fe(II)-phosphate
species FeH2PO4+,
FeHPO4 and FePO4-
have been determined for the first time. FePO4-
was found to be the most kinetically reactive species at circumneutral
pH with an estimated oxygenation rate constant of (2.2}0.2)~10
M-1 s-1. FeH2PO4+ and FeHPO4
were found to be less reactive with oxygen, with rate constants
of (3.2}2)~10-2 M-1 s-1 and
(1.2}0.8)~10-1 M-1 s-1, respectively.x
1. Introduction
2. Materials and methods
@2.1. Reagent preparation
@2.2. Fe(II) analysis
@2.3. Fe(II) oxidation experiments
@2.4. Fe(II) speciation calculations
@2.5. Estimation of individual oxidation rate constants
3. Results and discussion
@3.1. Overall Fe(II) oxidation rate constants
@3.2. The speciation model
@3.3. Evaluation of rate constants in the context of Marcus Theory
4. Conclusions
Acknowledgments
Appendix A. Supplementary data
References