| 摘要 |
EXTRACTION OF METAL VALUES FROM ORES OR CONCENTRATES A process is described for leaching ores or concentrates containing one or more metallic sulphides with a circulating liquor so as to solubilise desired metal values therefrom, if said metal values are capable of dissolution in an acidic ferric sulphate solution (e.g. copper), or so as to render the desired metal values (e.g. gold) more accessible to subsequent processing, in each case by effecting metallic sulphide dissolution from the ore or concentrate. In this process the ore or concentrate, for example a gold ore, is leached in a leach stage using an acidic leaching medium formed by mixing recycled liquor with a make-up stream containing bacterially generated ferric ions and sulphate ions which is produced in a generator (a) which is external to the circulation path of the liquor between the leach stage and a separation stage, (b) which contains a colony of suitable bacteria, such as Thiobacillus ferro-oxidans, and (c) which is fed, as necessary, with a pyritic material, water, nutrients, sulphuric acid and an oxygen-containing gas (e.g. air). As the presence of live bacteria in the leach stage is not essential to operation, the process can be used for leaching arsenopyritic and similar ores and with a recycle stream containing high levels of arsenic or other impurity which is potentially deleterious to bacterial viability. A mixture of leached solids and liquor is passed from the leach stage to the separation stage, which is included in the path of the circulating liquor where leached solids are separated from a ferrous sulphate-containing liquor. The leached solids can be treated for recovery of metal values (e.g. gold), if the metal values are not leached in the leach stage. Alternatively, if the desired metal values (e.g. copper) appear in the liquor, the leached solids are discarded and the liquor is subjected to metal recovery, e.g. cementation, before recycle. |
