Dissolution studies of chromium substituted iron oxides in reductive-complexing agent mixtures

The dissolution behaviour of 0-20 at.% Cr-substituted hematites and magnetites in Citric acid-EDTA-Ascorbic acid (CEA) mixtures at 353 +/- 2 K are reported. The dissolution rate coefficients are determined as a function of the Cr content of the oxide and reagent concentration of the CEA mixture, using a general kinetic equation. The dissolution rate coefficients are found to decrease with increase in chromium content of hematite and magnetites. The Cr-substitution in the hematite lattice has hindered the dissolution to a greater extent than in the magnetite lattice. The reductive action of Fe(II)-EDTA occurring in the dissolution of simple hematite and Cr-substituted magnetites was not found to be applicable in the case of Cr-substituted hematites, In 11-44-0 CEA medium, 10 metal at.% Cr-substituted magnetite dissolves to the extent of 83% (with respect to Fe) while 20 metal at.% Cr-substituted magnetite dissolves to the extent of 45%. Corresponding Cr-substituted hematites and simple hematite (alpha -Fe2O3) do not show any dissolution in this medium. (C) 2001 Elsevier Science B.V. All rights reserved.