Mycohydrometallurgy: Biotransformation of double refractory gold ores by the fungus, Phanerochaete chrysosporium

Double refractory gold ores (DRGO) contain organic carbonaceous matter (CM) and sulfide minerals, and thus require pretreatment before cyanidation for gold extraction. Though there have been several studies into microbial pretreatment of DRGO, available literature indicates that microbial degradation of both sulfides and CM in a single-stage process has not achieved much success. In an on-going research, the fungus Phanerochaete chrysosporium, has been used to effectively reduce the gold adsorption (preg-robbing) nature of surrogate CM on one hand, and decompose sulfides (pyrite and arsenopyrite) on the other. Such an application of fungi in hydrometallurgy has been termed 'mycohydrometallurgy'. The present research focused on assessing the possibility of using the fungus to simultaneously decompose sulfides and deactivate carbonaceous matter in refractory gold ores so as to liberate locked-up gold and reduce preg-robbing. Flotation concentrate (FC) of DRGO and bacterial-oxidized FC (BFC) were utilized in this investigation. After 21 days of fungal-treatment, overall sulfide sulfur decomposition of 57% in FC led to increase in gold extraction from 41% to 78%. Similarly, fungal-treatment of BFC led to 13% increase in gold extraction over the as-received (81%). The results demonstrate a novel alternative pretreatment process for DRGO.