| Summary: | The conditions under which copper was retained and re-distributed in a test heap of pyrrhotite-rich, copper-nickel sulfide ore were investigated in abiotic column leaching tests. It was determined that acidity plays a key role in maximising copper recovery. During passage through the ore bed, when the leachate pH rose to >2.3, copper ions previously released to solution through the oxidation of chalcopyrite were retained by adsorption on, or reaction with, ore minerals. Lack of aeration (limited oxygen) had only a small impact on copper recovery, in association with a favourable pH environment. Possible reaction mechanisms are discussed. The results indicated the need for careful acid management in the operation of heaps of pyrrhotite-rich ores such as complex copper-nickel sulfide ores.
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