Magnetite synthesis from ferrous iron solution at pH 6.8 in a continuous stirred tank reactor

Yvonne M. Mos, Karin Bertens Zorzano, Cees J.N. Buisman, Jan Weijma*

*Corresponding author for this work

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Abstract

Partial oxidation of defined Fe2+ solutions is a well-known method for magnetite synthesis in batch systems. The partial oxidation method could serve as basis for an iron removal process in drinking water production, yielding magnetite (Fe3O4) as a compact and valuable product. As a first step toward such a process, a series of experiments was carried out, in which magnetite was synthesized from an Fe2+ solution in a 2 L continuous stirred tank reactor (CSTR) at atmospheric pressure and 32 °C. In four experiments, elevating the pH from an initial value of 5.5 or 6.0 to a final value of 6.8, 7.0 or 7.5 caused green rust to form, eventually leading to magnetite. Formation of NH4 + in the reactor indicated that NO3 and subsequently NO2 served as the oxidant. However, mass flow analysis revealed an influx of O2 to the reactor. In a subsequent experiment, magnetite formation was achieved in the absence of added nitrate. In another experiment, seeding with magnetite particles led to additional magnetite precipitation without the need for a pH elevation step. Our results show, for the first time, that continuous magnetite formation from an Fe2+ solution is possible under mild conditions, without the need for extensive addition of chemicals.

Original languageEnglish
Pages (from-to)1870-1878
JournalWater Science and Technology
Volume77
Issue number7
DOIs
Publication statusPublished - Apr 2018

Keywords

  • CSTR
  • Groundwater
  • Iron removal
  • Magnetite
  • Nitrate
  • Oxygen

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    Mos, Y. M. (Creator), Bertens Zorzano, K. (Creator), Buisman, C. (Creator) & Weijma, J. (Creator), Wageningen University & Research, 27 Sep 2018

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