| Summary: | The objective of this study was to obtain information on the role of iron in the oxidation of sulfide minerals. Activated carbon, a catalyst for the oxidation of iron (II), was used as a tool. Activated carbon was an effective catalyst for the oxidation of iron (II) using percolators. The catalytic action increased at decreasing pH. The optimum amount of carbon to be used in the percolator was 0.5 g. The bubbling rate of the percolator was not critical. The presence of activated carbon increased the rate of oxidation of copper (II) sulfide. Increasing the iron concentration increased this rate, but not linearly. The bacteria had an optimum iron concentration in the oxidation of copper (II) sulfide. The activated carbon had little effect upon the biological activity. Iron (III) was not as effective in oxidizing copper (II) sulfide as iron (II) and carbon. Cuprite was rapidly oxidized by air at pH 1.0. The rate was increased by the presence of activated carbon and iron (II). Iron (III) had a greater effect on the oxidation of pyrite than iron (II) and carbon. The oxygen in the air was essential to the oxidation of pyrite. The bacteria produced the greatest rate of oxidation of the pyrite. Bornite, covellite, and chalcocite were all oxidized by iron (III). Chalcopyrite showed very limited oxidation by iron (II) and iron (III) solutions but gave very rapid oxidation with an iron (II) solution and carbon at pH 1,0. Varying the temperature on runs with covellite gave a biological optimum when the bacteria were present. The sterile run gave the effect of air oxidation with an iron (II) solution. The state of the soluble iron in these runs demonstrated biological activity, the reduction of iron (III) by the mineral, and the air oxidation of the iron at various temperatures.
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