Rates of Reaction of Galena, Sphalerite, Chalcopyrite, and Arsenopyrite with Fe(III) in Acidic Solutions

We measured the rates of reaction of Fe(III) with galena, sphalerite, chalcopyrite, and arsenopyrite at 25°C and pH values near two and found: Where r Fe 3+ is the rate of reduction of Fe(III) to Fe(II) (mol sec -1 ), m Fe 3+ is the concentration of Fe(III) (mol kg -1 ), and A is the surface area of the solid (m 2 ) exposed to the solution. These results show that the reaction rates, the reaction orders and the activation energies vary substantially from mineral to mineral indicating that the details of the reaction mechanism differ among the various sulfide minerals. This means that pyrite cannot be used as a proxy for these other sulfide minerals when studying the details of sulfide mineral oxidation.