Dissolution of Iron from Oxides in Solutions of Citric Acid and Sodium Thiosulfate

In this work, the dissolution of iron from a kaolinitic mineral (Veracruz, México) is compared with that from an iron ore (Michoacán, México), a specular hematite (México), a magnetite (southeastern Utah, USA) and a hematite (from Arizona, USA), using sodium thiosulfate and citric acid, as the reducing and complexing agents, respectively. The minerals were dry sieved to obtain particle sizes between-100 +250 mesh. The minerals were then characterized by X-ray diffraction (XRD), energy dispersive spectroscopy EDS and atomic absorption (AA). Leaching experiments were using 0.5 M of both reactants at temperature of 363.15 K and pH = 3; this one last parameter was controlled with ammonium hydroxide. The experimental results showed removal of dissolved iron above 99% in the kaolinitic clay and the magnetite, but only 79% for the iron ore, 46% for the hematite and 30% for the hematite, in 180 minutes.