Sulfide ore biooxidation is under the action of autotrophic bacteria (e.g. bite Thiobacillus, Thiobacillus iron oxide), and the ore pre-treatment, the gold oxide and dissociated out, and then using a conventional cyanidation (or other methods) reacting Gold recycling.
For pyrite, the resulting reaction can be expressed as follows: At the beginning, pyrite is oxidized by Thiobacillus ferrooxidans to form ferrous sulfate and sulfuric acid:
4FeS 2 + 14O 2 + 4H 2 O → 4FeSO 4 +4H 2 SO 4
Soluble ferrous iron is quickly oxidized by bacteria to produce high-sulfur sulfate:
4FeSO 4 +O 2 +2H 2 SO 4 → 2Fe 2 ( SO 4 ) 3 +2H 2 O
Therefore, the total reaction is a reaction of a pure acid production process:
4FeS 2 +15O 2 +2H 2 O → 2Fe 2 ( SO 4 ) 3 +2H 2 SO 4
The high-iron sulfate may be hydrolyzed and precipitated as iron hydroxide, basic ferric sulfate or potassium ferro- vanadium . In the treatment of pyrite concentrates, sufficient sulfuric acid is usually produced to lower the pH and minimize hydrolysis, with most of the iron remaining in the solution. The production of a low pH solution requires a solution exchange system to maintain an environment conducive to bioleaching.
Tests on the bioleaching of two pyrite concentrates show that bacterial leaching can highly oxidize refractory pyrite concentrates, and the results of pre-oxidation increase the cyanide leaching rate in the next step, and the gold recovery and bacterial oxidation are found. The degree is proportional. When the pyrite oxidation rate is 87%, the gold recovery rate is 81%, and if the concentrate is directly cyanated, the gold recovery rate is only 24%. When the concentrate contains a large amount of non-ferrous metal sulfides, the bacteria are simultaneously oxidized during the leaching process, and the valuable metals can be recovered from the leachate, and the leaching residue is subjected to cyanidation recovery by adjusting the pH and adjusting the pH of the lime. Since bacterial leaching can dissolve cyanide-depleting constituents in the concentrate, the consumption of cyanide can be reduced.
Bacterial leaching is also suitable for the treatment of other sulphide ores containing gold, such as arsenic pyrite, which is better than pyrite in bacterial leaching. It is also suitable for heap leaching or percolating leaching of ore to recover gold and silver from low grade ore or waste.
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