Suppression of preg-robbing activity in carbonaceous gold ores by the fungus trametes versicolor

Abstract

Carbonaceous matter in gold ores adsorbs dissolved gold during leaching and reduces extraction; a phenomenon known as preg-robbing. Microbial suppression of preg robbing activity in a carbonaceous sulphidic gold ore was investigated using a white rot fungus, Trametes versicolor (ATTC 20869) with the aim of enhancing gold extraction. A study was conducted to monitor the effect of microbial-ore interactions on preg-robbing and the process variables were pulp density, temperature, pH and processing time. In addition, both biotic and abiotic investigations were performed to ascertain the effects of fungal culture and culture medium alone on reduction of preg-robbing. Analysis of ore carbon content after microbial contact indicated that Trametes versicolor reduced preg robbing activity by passivation of carbonaceous matter and not degradation; as preg robbing activity significantly decreased from 18.1% to below 1.0 % with insignificant changes in carbon content. Three (3) days of microbial-ore interaction at pH 4.5 and 30oC temperature were the established optimum conditions for passivation. Various types of coal samples were utilized as surrogates and the study showed that the characteristics of the carbon material influenced the ability of Trametes versicolor to reduce preg-robbing. This novel application of Trametes versicolor to process carbonaceous gold ore resulted in significant suppression of preg-robbing activity.