Study on kinetics of Fe (II) oxidized by air in FeSO4-H2SO4 solutions

The oxidation of Fe2+ in acidic aqueous sulphate solutions with dissolved molecular oxygen is commonly employed in many hydrometallurgical processes such as the leaching of metal sulphides or the purification of leach solutions. Due to the action of the ferric-ferrous redox couple, the process of leaching metal sulphides is transformed from gas-solid reaction to liquid-solid reaction. In the present work, experiments were performed to assess the effects of temperature, ferrous concentration, air flow rate (QAir), and sulfuric acid concentration on the kinetics of oxidation of ferrous ions. The reaction order with respect to the concentrations of Fe2+, air flow rate and H2SO4 was investigated. The activation energy determined from these k values is 31.67 kJ/mol, and this suggests that the oxidation of Fe2+ is chemically controlled. Considering the relationship between the saturation point of air flow (QAirS) and solution volume, an overall equation to describe the rate of ferrous oxidation was proposed.-d[Fe2+]/dt=1.48[Fe2+]2QAir0.42[H2SO4]-0.36exp(-31670/RT)QAir⩽QAirS1.48[Fe2+]2QAirS0.42[H2SO4]-0.36exp(-31670/RT)QAir>QAirS