Kinetics of the Cupric Catalyzed Oxidation of Fe^II by Oxygen at High Temperature and High Pressure

ABSTRACT

The oxidation of Fe^II to Fe^III by oxygen in sulfate media plays an important role in the pressure leaching of copper sulfide concentrates because ferric ion is a more effective oxidant of copper sulfide minerals than oxygen. In this work, the cupric catalyzed oxidation of ferrous sulfate by oxygen at high temperature and high pressure has been investigated. The effects of the variables temperature (393 to 493 K)), sulfuric acid concentration (0.15 to 1.2 M), copper sulfate (0 to1.6×10^–2 M) and partial pressure of oxygen (343 to 1379 kPa) were studied. The presence of cupric ions in the solution greatly accelerated the rate of ferrous oxidation in the range of experimental conditions studied but the rate was not a function of the cupric concentration over 4×10^–3 M. The following empirical equation was found to accurately describe the rate of the cupric catalyzed oxidation of Fe^II by oxygen:

The experimental activation energy for the cupric catalyzed ferrous oxidation was 36.5 kJ/mol while in the absence of cupric ions in the solution, the oxidation of Fe^II by oxygen proceeds through a second order model with respect to Fe^II concentration with an activation energy of 78.0 kJ/mol.

KEYWORDS:

• Ferrous oxidation
• kinetics
• cupric catalyses
• pressure oxidation