This Small Business Innovation Research Phase I project will investigate the feasibility of developing a biohydrometallurgical process for extracting gold and silver from bio-oxidized ore by means of leaching that does not incorporate use of cyanide, thiourea, thiosulfate, or other conventional lixiviants. Gold and silver mines are often located in pristine environments that are highly susceptible to pollution by mining and metals recovery activities. While biotechnologies have been developed for freeing precious metals from refractory ores, cyanidation is still the process of choice for extracting gold and silver values. Whereas the ultimate goal of the research is to develop a heap leach process, a simplified working model will be used to study the process during Phase I. The working model will comprise a continuous stirred tank reactor (CSTR) containing a slurry of ore particles to minimize mass transfer limitations. The project includes using mathematical models to infer optimum processing conditions, designing an experimental working model of the process, fabricating the working model and developing experimental techniques, conducting proof-of-concept experiments, and analyzing the data from those experiments. A significant change in the basic technology of gold and silver extraction is proposed that will reduce mining-associated pollution at its source.
