DISSOLUTION OF HEMATITE IN ACIDIC OXALATE SOLUTIONS - THE EFFECT OF FERROUS-IONS ADDITION

Studies on the dissolution of hematite in acidic oxalate solutions hav e shown that there is a strong relationship between dissolution rates and ferrous ion generation in the solution, The effects of temperature , pH of the solution, oxalate and ferrous ions concentration on the di ssolution of hematite in acidic oxalate solutions containing ferrous i ons were studied, It was found that the pH of the solution is very imp ortant for the dissolution as it affects: (1) the activation of hemati te surface with adsorbed hydrogen ions; (2) the adsorption of [Fe(C2O4 )(2)](2-) complex ions on surface active sites and (3) the speciation in oxalate solutions containing ferrous ions, Iron dissolution is high ly dependent on temperature and ferrous ion concentration, while it is practically independent of the total oxalate concentration. The disso lution of hematite in oxalate solutions comprises three stags: (1) act ivation of the solid surface; (2) generation of ferrous ions in the so lution (induction period); and (3) an autocatalytic dissolution period , When ferrous ions are added, the induction period is eliminated and dissolution proceeds through the autocatalytic pathway.