Formation Process of Magnetite by Application. of Hydrolysis of Urea

Abstract

Magnetite was synthesized from the mixed solution of urea and iron(II) and iron(III) chlorides at about 100°C for 5h, and the intermediate precipitates were examined by X-ray diffraction and EM observation. Brownish-yellow β-FeOOH suspension was initially formed by the hydrolysis of iron(III) ion with a consequent decrease in pH to about 1.1. The hydrolysis of urea due to heating resulted in the pH increase and hence the formation of Fe₃O₄ at about pH 5.0. In the hydrolysis process of iron(II) and iron(III) ions, α-FeOOH was seemed to be formed temporalily as well as α-FeOOH, but they changed to Fe₃O₄ by the reaction with iron(II) ion. Similarly, heating of α- or α-FeOOH suspension containing urea and iron(II) ion resulted in the formation of Fe₃O₄.