The removal of iron and various heavy-metal ions by their incorporation into stable ferrite-type precipitates at 25 °C is a promising alternative to clean up large volumes of polluted effluents. As a first step, the present work investigated the conditions to produce the iron ferrite magnetite by the aerial oxidation and neutralization of ferrous sulfate solutions under well-controlled conditions and at low temperatures. The formation of the solids was followed by monitoring the oxidation-reduction potential (ORP) and the release of protons associated with the progress of the oxidation of Fe(II) ions and subsequent hydrolysis of produced Fe(III) species. The parameters studied were: contact time at constant pH, air flow-rate, stirring intensity, aging of the solids and precipitation temperatures below 60 °C. It was found that a moderate oxidation rate of ferrous entities, represented by all ORP of -120 mV and a rate of proton release of 1.60×10-4 mol H+/l min. favored the formation of intermediate green rust-II and its conversion into magnetite at a temperature as low as 25 °C, even without aging. In contrast, an extremely fast oxidation reaction favored by the enhancement of the air flow-rate and stirring intensity deteriorated or even destroyed incipient ferrite frameworks. When the formation of magnetite was incomplete, aging of the sludges in contact with their mother liquors promoted the crystallinity of the precipitates. Furthermore, the beneficial effect of stirring intensity and the only slight influence of temperature on the oxidation rate, at a level of 21 kJ/mol (5 kcal/mol), suggested that a mass-transfer step would control the oxidation of ferrous entities at low temperature. This mass-transfer step could be attributed to the transfer of oxygen into the aqueous phase. A discussion on the magnetite-forming reaction at ambient temperature is also presented.