METHOD AND APPARATUS FOR EXTRACTING PRECIOUS METALS FROM THEIR ORES AND THE PRODUCT THEREOF

摘要

A method and apparatus (4) for extraction of precious metals from their ores and the product (26) thereof. Oxidized ore comprising precious metals is exposed to a leaching solution (lixiviant) (254) comprising a relatively high concentration (activity) of dissolved hydrogen sulfide gas, a relatively high concentration (activity) of bisulfide ions, and a relatively low concentration (fugacity) of dissolved hydrogen gas. The hydrogen sulfide gas and bisulfide ions are preferably added to the solution by sulfate-reducing bacteria growing in a medium comprising dissolved sulfate ions and dissolved nitrate ions, but abiotic sources may also be used. Examples of such bacteria include mesophilic, fresh-water species such as Desulfobacterium catecholicum DSM 3882 and Desulfovibrio simplex DSM 4141; mesophilic, salt-water species such as Desulfovibrio salexigens DSM 2638; and thermophilic, fresh-water species such as Desulfomaculum kuznetsovii VKM B-1805.