Two mathematical models were used to evaluate the reductive dissolution kinetics of goethite and hematite. The Kabai’s model described dissolution as a single linear segment, not discriminating the dissolution of different phases of the same iron oxide or different iron oxides in a sample. Consequently, this model can only compare crystal stability between distinct samples. The Avrami-Erofejev’s model described dissolution as a set of linear segments for most of the samples. This model discriminated different phases of the same iron oxide and allowed classification of the degree of stability of these minerals in each sample. Both models indicated that hematite is less stable than goethite against reductive dissolution, mainly when goethite combines low Al+3 substitution and high specific surface area. The evaluation of these mineralogical parameters on the crystal stability in the reductive dissolution showed dependecy of the model used for determining the dissolutive kinetic.
iron oxides; differential stability; crystallinity; Al3+-substitution
