Reconciling kinetic and equilibrium observations of iron(III) solubility in aqueous solutions with a polymer-based model

Formation, reactivity, and aging of ferric oxide particles formed from Fe(II) and Fe(III) sources: Implications for iron bioavailability in the marine environment

“…A dissolution-precipitation mechanism leading to greater coordination of Fe centres and stronger bonding (conversion of hydroxo-to oxo-bridges between Fe centres) was proposed to account for these experimental results (Rose and Waite, 2007). However, in a high ionic strength medium such as seawater, aggregation of AFO is expected to be rapid due to charge shielding effects, especially immediately after formation when particle numbers are maximal, and the loss of accessible surface area accompanying aggregation is also potentially a significant cause of declining dissolution rate.…”

“…Aging of iron oxides has been described previously in terms of a decrease in the apparent dissolution rate constant k d * (Kuma and Matsunaga, 1995;Yoshida et al, 2006) and has been conceptualised in terms of two simultaneous processes -(1) increased coordination of iron centres by bridging groups, and (2) conversion of hydroxo-bridges to oxo-bridges (Rose and Waite, 2007). The former of these processes is rapid while the latter occurs over a much longer time scale.…”

“…The formulation of this conceptual aging model by Rose and Waite (2007) has been rearranged in Eq. (4) in order to more concisely reflect the underlying mechanisms such that the depolymerisation/polymerisation process is described as the transfer of iron from a labile pool with a dissolution rate constant k d0 * , quantified as the value of k d * at time zero, to a more stable pool with a dissolution rate constant k d0 * a, where a is the reduction factor for the dissolution rate constant on transfer from the labile to the stable pool, and is a function of the change in coordination environment of repolymerised iron.…”

“…Also shown are the parameter values for the model (Eq. (4)) developed by Rose and Waite (2007) for AFO(III) reactivity changes measured using a variation of LPD.…”

Effect of phosphate, silicate, and Ca on the morphology, structure and elemental composition of Fe(III)-precipitates formed in aerated Fe(II) and As(III) containing water

“…Due to the extremely low solubility of Fe(III)-precipitates, the onset of Fe(II) oxidation at pH 7 will result in rapid oversaturation of Fe(III). Thus, Fe(III) will readily polymerize and precipitate from solution (Rose and Waite, 2007). In this work, we focused on the structure and morphology of Fe(III)-precipitates after Fe(II) oxidation was completed.…”