Montedison S.p.a.

Angelo Garberi

Gian Lorenzo Marziano

Agostino Geddo

Bruno Viviani

A process is disclosed for preparing magnetite having an equiaxial morphology and a narrow particle size dispersion by precipitation from a ferrous sulphate solution, characterized in that: A. during a first step, at a temperature between 15.degree. and 40.degree. C, alkali is added to the ferrous sulphate solution, in a stoichiometric amount adapted to precipitate, in the form of ferrous hydroxide, 2/3 of the Fe.sup.+.sup.+ ion, and then, at the conclusion of said precipitation, air is blown thereinto thus oxidizing ferrous hydroxide to goethite .alpha.FeO(OH); and B. during a second step, alkali is added to the slurry obtained in the first step, the remaining Fe.sup.+.sup.+ is precipitated in the form of ferrous hydroxide, and the slurry is heated to a temperature between 70.degree. and 100.degree. C, thus causing the formation of magnetite which is then separated from the solution.

Process for preparing magnetite starting from ferrous sulphate solutions

A method is disclosed for controlling the particle size of equiaxial magnetite obtained by a process for preparing same starting from ferrous sulphate solutions, characterized in that the reaction forming the magnetite is conducted in a suspension to which .gamma. FeO(OH) has been added in such an amount that Fe of the .gamma. FeO(OH) is 0.1-10% of the Fe.sup.+.sup.+ initially present in the solution.

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Cilavegna (Pavia), Italy

Angelo Garberi