DISSOLUTION OF METAL FERRITES AND IRON-OXIDES BY HCL UNDER OXIDIZING AND REDUCING CONDITIONS

A study has been carried out on the relative rates of dissolution of copper, zinc, and nickel ferrites in HCI solutions and on the effect of various oxidant and reductant species in solution. The results are compared with the rates of dissolution of hematite, magnetite, and nickel oxide and correlated with their electrochemical behavior. Cyclic voltammograms of the metal ferrites and oxides show oxidation or reduction peaks corresponding to changes in the oxidation state of the metal in the lattice. It is shown that the relative reactivity in 1 M HCl at 25 ° is in the order Fe3 O4ZnFe2O4>CuFe2O4>Fe2O3 >NiFe2O4. The leaching of the metal ferrites and iron oxides is enhanced by the presence of 0.01 M Cu(I) or Sn (II) but the leaching of NiO is enhanced by oxidants such as 0.01 M Cu(II) in chloride media.