Synthesis of Magnetite in Presence of Cu2+ or Cr3+

The effects of Cu or Cr ions on the formation of magnetite, which were prepared by two different methods, were studied by 57Fe Mössbauer spectrometry. The first synthesis procedure consisted in an alkaline hydrolysis of ferrous chloride solution in accordance with literature reports. The second method, which was a variation of a reported synthetic route, consisted of a reaction of a 2:1 Fe(II)/Fe(III) solution under alkaline conditions in the presence of an oxidant agent. The samples were also prepared in the presence of chromium or copper chloride solutions. Our results showed that the magnetites obtained via the first procedure exhibits a higher degree of stoichiometry and a better crystalline quality than those prepared by the second route. It seems that the presence of chromium helped the formation of goethite, whereas the presence of copper interfered with it in agreement with other works. We observed that the magnetites obtained in the presence of copper were of poorer crystallinity than the ones obtained with chromium. Finally, the influence of Cu or Cr upon the magnetic and crystalline properties of the two series of magnetites is also presented and discussed.