Acidic dissolution of hematite: Kinetic and thermodynamic investigations with oxalic acid

Although extensively studied, consensus on the kinetics or thermodynamics of iron oxide dissolution has not yet been achieved among scientists. The aim of this study was to investigate the applicability of twelve different kinetic models in describing the dissolution of hematite (α-Fe2O3). In this study, hematite was dissolved in 0.6 mol/L oxalic acid at 50 °C to obtain kinetic data for modeling. In addition to the kinetic data, thermodynamic data were collected at 35 and 50 °C to discuss the dissolution mechanism. The Kabai equation and the first order rate law were found most suitable in describing the dissolution. The associated reaction rate constants were 2.0·10− 5 s− 1 for both models.

► Temperature had no effect on the equilibrium concentration of dissolved iron.
► The best fit was obtained with the Kabai equation.
► The reaction rate coefficient appears to be 2.0·10− 5 s− 1.