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Fe2+ adsorption on iron oxide: the importance of the redox potential of the adsorption system

Authors
  • Piasecki, W.1
  • Szymanek, K.1
  • Charmas, R.2
  • 1 The Józef Piłsudski University of Physical Education in Warsaw, The Department of Chemistry and Biochemistry, Warsaw, Poland , Warsaw (Poland)
  • 2 Łomża State University of Applied Sciences, Łomża, Poland , Łomża (Poland)
Type
Published Article
Journal
Adsorption
Publisher
Springer US
Publication Date
Mar 13, 2019
Volume
25
Issue
3
Pages
613–619
Identifiers
DOI: 10.1007/s10450-019-00054-0
Source
Springer Nature
Keywords
License
Green

Abstract

We have demonstrated that the redox potential of the solution containing an inert electrolyte, ferrous ions, and metal oxide allows a much better understanding of the process of Fe(II) adsorption on oxide with the increase of pH. We tested two oxides: γ-Fe2O3 (maghemite) and TiO2 (the mixture of anatase and rutile). For both of them, we determined proton surface charge, Fe(II) uptake curves, electrokinetic potential, and redox potential in solution. The all measured quantities except the last, behaved in an almost identical manner for ferric oxide and titanium dioxide. The redox potential strongly depends on the pH of the solution and stabilizes when the adsorption process is finished (pH above 6). We observed that for the solution consisting only of 0.2 mM Fe(II) and 0.1 KCl the redox potential in the pH range 3–6 can be expressed by the formula: Eh[mV]=1120-3×59×pH-59×log(a_Fe(II))\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Eh[mV]=1120 - 3 \times 59 \times {\text{pH}} - 59 \times \log (a\_{\text{Fe}}({\text{II}}))$$\end{document}.

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