For coarse grain size of gold after crushing and grinding by flotation, gravity concentration, cyanide leaching process or several process combined treatment will be able to complete the separation of gold and gangue minerals, but there are some curing refractory gold ores due to coarse size or thin and gangue minerals symbiosis relations complex factors through the above process unable to complete the separation process, before the separation must be certain pretreatment. The common pretreatment methods for gold sulfide gold deposit are oxidizing roasting method, curing method, acid pressure oxidation, bacterial oxidation method, nitric acid oxidation method, etc.
Gold ore which is difficult to concentrate often referred to gold or refractory gold ore, which use conventional cyanide process cannot effectively extract most of the gold ore. Therefore, it is commonly said that the treatment of gold is the case of the cyanide method. Part of refractory gold ores of gold particles with fine gold or submicroscopic gold a parcel or disseminated exist in sulfide ore and the sulfide is usually pyrite, arsenopyrite, pyrrhotite, even in some mineral deposits, most of the gold can enter the crystal lattice of pyrite, arsenopyrite, in the state of super micro gold. Even if the ore is very thin, it cannot make gold, the gold leaching effect is very poor. It can be said that this is the most difficult to deal with the gold in the refractory gold ore. Thiobacillus ferrooxidans was to autotrophic bacteria that it to sulfide, elemental sulfur, ferrous sulfate, thiosulfate and other low sulfur compound oxidation in the process of releasing energy for energy, and carbon dioxide in the air for nutrients to synthesize bacterial reproduction. These characteristics of Thiobacillus ferrooxidans makes it become the oxidative decomposition of pyrite and arsenopyrite, exposed the Au coated ideal bacteria.
Some of the plant refractory gold ore cyaniding leaching before containing ferrous oxide coli acid bacteria liquid of ore processing, since Thiobacillus ferrooxidans for aerobic bacteria and sulfide oxidation is exothermic reaction, so in this strain to treat refractory gold ore must note oxygen and temperature control. Bacterial leaching with decomposition of pyrite and arsenopyrite sulfide ability strong, gold and silver recovery rate is high, no environmental pollution, infrastructure investment and production cost advantages of bacterial oxidation pre-treatment package containing gold ore is becoming a clean technology and energy saving by the attention of the countries all over the world, recognize bacterial pre oxidation treatment process is likely to replace in the industry to obtain application of oxidizing roasting and pressure oxidation process.