Effects of Entrained Biomass of Phanerochaete Chrysosporium on Carbon-In-Leach Operations

Carbon-In-Leach (CIL) is one of the conventional methods employed in the hydrometallurgical recovery of gold from its ores, especially where the ore contains natural carbonaceous matter that preg-robs dissolved gold. CIL is also employed in the recovery of gold from refractory ores that have undergone oxidative pretreatment. Oxidative pretreatment may be achieved using fungi, which biotransforms carbonaceous matter to reduce its ability to preg-rob gold. Such biotreated materials may be entrained with fungal-biomass, which can affect the activity of activated carbon introduced purposefully to adsorb dissolved gold. Previous works using cell-free extracts of Phanerochaete chrysosporium to treat activated carbon reported a decrease in its ability to adsorb gold, and a general improvement in the adsorption process when the treated carbon was washed before it was contacted with standard gold solution. This paper presents the findings of a follow-up research, in which an oxide ore was contacted with cell-free extract of P. chrysosporium for 24 hours to mimic fungaltreated refractory gold ore. The as-received ore and fungal-treated ore were each leached with and without activated carbon to ascertain the effect of entrained fungal biomass on oxidised gold ores, and the rippling effect on activated carbon during the CIL process. This paper reports that, at the end of the 24-h cyanidation process, the activated carbon in the as-received sample adsorbed an average of 20% more auro-cyanide than the activated carbon in the sample treated with the cell-free extract. In the absence of activated carbon, both the as-received sample and the treated sample recorded almost the same gold in solution. It can be concluded that transportation of fungal extracts into CIL operations can reduce the adsorption capacity of activated carbon, and such treated ores require proper water-washing prior to CIL.