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The oxygen pressure leaching of pyrite in sulfuric acid

University of British Columbia

The oxygen pressure leaching of pyrite in sulfuric acid has been studied at pressures up to 976 psi O₂ and temperatures from 85 to 130°C. The dissolution has been found to follow linear shrinking 1 /3 core kinetics (1 - (1 - ∞)[sup ⅓]). The dependence of the reaction rate on oxygen pressure has been modelled using a Langmuir Adsorption Isotherm. A limiting dissolution rate for total adsorption of 0.624 moles/m² hr. has been obtained for the conditions tested. Factors studied for the reaction include: geologic differences in pyrite, acid concentration, pulp density, the presence of neutral salts and other sulfide minerals, and particle size, along with the dependence on temperature and pressure. An overall equation for pyrite dissolution has been tested and found to correlate well with the experimental data. The distribution of reaction products between sulfate and elemental sulfur, and ferric or ferrous iron has been examined. Higher yields of elemental sulfur were found with lower acid concentration and reduced oxygen pressure. The ferric/ferrous ratio was found to be most affected by the extent of pyrite dissolution. Increases in the ratio were also found when neutral salts were added to the system and when oxygen pressure was increased. The dissolution reaction was found to be an acid-consumer for initial acid concentrations above 0.4MH₂SO₄. For concentrations below this Level, the reaction produces acid. An activation energy of 12.7 ± 0.7 kcal/mole was observed for the dissolution reaction.

Text

2010-01-29

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http://hdl.handle.net/2429/19356

Metals and Materials Engineering

University of British Columbia

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