|Title||Magnetite synthesis from ferrous iron solution at pH 6.8 in a continuous stirred tank reactor|
|Author(s)||Mos, Yvonne M.; Bertens Zorzano, Karin; Buisman, Cees J.N.; Weijma, Jan|
|Source||Water Science and Technology 77 (2018)7. - ISSN 0273-1223 - p. 1870 - 1878.|
Sub-department of Environmental Technology
|Publication type||Refereed Article in a scientific journal|
|Keyword(s)||CSTR - Groundwater - Iron removal - Magnetite - Nitrate - Oxygen|
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.