title: Potentiometric and electrokinetic signatures of iron(II) interactions with (α,γ)-Fe2O3.
abstract: The electrochemical signatures of Fe(II) interactions with iron(III) oxides are poorly understood, despite their importance in controlling the amount of mobilized iron. Here, we report the potentiometric titration of α,γ-Fe2O3 oxides exposed to Fe(II) ions. We monitored in situ surface and ζ potentials, the ratio of mobilized ferric to ferrous, and the periodically analyzed nanoparticle crystal structure using X-ray diffraction. Electrokinetic potential reveals weak but still noticeable specific sorption of Fe(II) to the oxide surface under acidic conditions, and pronounced adsorption under alkaline conditions that results in a surface potential reversal. By monitoring the aqueous iron(II/III) fraction, we found that the addition of Fe(II) ions produces platinum electrode response consistent with the iron solubility-activity curve. Although, XRD analysis showed no evidence of γ-Fe2O3 transformations along the titration pathway despite iron cycling between aqueous and solid reservoirs, the magnetite formation cannot be ruled out.
authors.affiliation: Institute of Physical Chemistry, 44/52 Kasprzaka, Warsaw, Poland. kkedrakrolik@ichf.edu.pl zarzycki.piotrek@gmail.com.
authors.forename: Diana
authors.initials: D
authors.lastname: Toczydłowska
authors.forename: Karolina
authors.initials: K
authors.lastname: Kędra-Królik
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Nejbert
authors.forename: Tajana
authors.initials: T
authors.lastname: Preočanin
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Rosso
authors.forename: Piotr
authors.initials: P
authors.lastname: Zarzycki