Effect of Dissolved Oxygen on the Rate of Pyrite Oxidation with Ferric Sulfate

Kinetics of pyrite oxidation in acidic ferric sulfate solution in the presence of dissolved oxygen was studied in the ternperature range of 313-333K. The effects of concentration of Fe2+, Fe3+, H+ and dissolved oxygen on oxidation rate were examined. All experiments were carried out isothermally in a batch reactor. The results are as follows:(1) The oxidation of pyrite with dissolved oxygen hardly occur under the experimental conditons studied.(2) The oxidation of ferrous ions with dissolved oxygen heterogeneously proceeds at the surface of pyrite, and the reaction orders for Fe2+, Fe3+ and dissolved oxygen are found to be 1, -1 and 1.2 respectively.(3) The reaction mechanism of pyrite oxidation with ferric ions in the presence of dissolved oxygen is as follows: Ferric ions react with pyrite to form ferrous ions, ferrous ions thus formed are oxidized to ferric ions with dissolved oxygen.(4) A reaction model consisting of the pyrite oxidation with ferric ions and the ferrous ions oxidation with dissolved oxygen was proposed and this model fits satisfactory with the experimental results.