Biological Pretreatment of Refractory Gold Ore by the Fungus, Phanerochaete Chrysosporium

In this research, fungus Phanerochaete chrysosporium has been used to effectively reduce the gold adsorption ability of carbonaceous matter on one hand, and decompose metal sulfides on the other, to ultimately enhance the gold extraction. Two ranks of coal (ordinary and anthracite) were used as substitutes to investigate the ability of fungus to reduce the gold adsorption by carbonaceous matter. The results showed that the ability of anthracite coal in gold adsorbing is 5 times more than ability of ordinary one. Phanerochaete chrysosporium reduced the ability of anthracite by over 85% for a 21 days culturing period under processing in PBD (Potato Dextrose Broth) medium and 95% for the same period in MWB (Millet and Wheat Bran) medium. Phanerochaete chrysosporium has also ability to oxidize the sulfide existing in refractory gold ores. The pyrite initial weight decreased by 35% for pH equal 7 and 30% for pH equal 4 in 21 days
of processing. Pretreatment was performed for Zarshouran refractory gold ore with different percentage of orpiment and gold. After a 14 days of processing, the amount of gold extraction by cyanidation of samples (1) (-2210 µm fraction containing less orpiment than natural samples),(2) (similar to natural samples from the amount of orpiment point of view), and (3) (� µm fraction containing enriched over 85% orpiment) increased to 30%, 25% and 1% respectively and sulfide mineral existing in samples (1) and (2) both decreased by over 50%. According to the results, Phanerochaete chrysosporium is a microorganism with high potential for oxidizing the sulfide minerals and neutralizing the carbonaceous matter existing in refractory gold ore simultaneously and totally, it has a high potential for increasing the gold recovery in cyanidation of refractory gold ore.