Bioleaching of a Mixed Copper Sulfide Ore Containing Enargite and Luzonite

摘要

The Nena deposit of the currently undeveloped Frieda River copper project in Papua New Guinea contains the copper minerals chalcocite (Cu_2S), covellite (CuS), enargite (Cu_3AsS_4), and luzonite (a dimorph of enargite), along with significant amounts of pyrite (FeS_2). This study was done to determine if the ore and a flotation concentrate could be bioleached and if copper was extracted selectively from certain of the minerals. Shake flask tests were done at 25℃ with Acidithiobacillus-Leptospirillum-type bacteria and at 50℃ with mixed, moderately thermophilic sulfide-oxidizing bacteria. Copper extraction by Acidithiobacillus-Leptospirillum bacteria was 56% from the ore (particle size minus 10 mesh) and 47% from the concentrate (P_(80) 20um). Thermophilic bacteria extracted somewhat more copper, amounting to 65% from the ore and 62% from the concentrate. About 20% to 25% of the arsenic in the ore and in the concentrate was extracted when pyrite was oxidized at high solution redox potential. However, it does not appear that arsenic was released from the enargite/luzonite, based on microscopy of polished sections and because arsenic was extracted into solution in the absence of copper extraction. Bioleaching of Frieda River ore and concentrate, especially with thermophilic bacteria, extracted most of the chalcocite and covellite but extracted little of the enargite/luzonite. The source of the extracted arsenic remains uncertain and requires further investigation. Some deposits of enargite may be refractory to bioleaching.