High Pressure Oxidation of
Refractory Gold Minerals

A lot of researches deem this process as the best option to the treatment of refractory material that contains gold and silver, primarily when the precious metals are encapsulated into pyrite and arsenopyrite. The process works to high temperatures of 160 to 220 degrees C, high pressures of 12 to 30 atmospheres, and dwelling time of 1 to 4 hours. At the creation, this process was utilized productively in the treatment of sulphide ores and concentrates.

Oxidation can be done under acid or alkaline conditions devoid of air contamination with SO₂ or arsenic compounds. Nonetheless, throughout the process the formation of sulphur and jarosites needs to be avoided for the reason that gold particles can be occluded with some sulphide particles creating a high consumption of cyanide throughout the leaching stage. In most cases, It is included a hot-lime step with the intention of destroying jarosites and develop dissolution of the precious metals. Pyrite and arsenopyrite oxidation has to do with a number of reactions with formations of ferrous sulphate, ferric sulphate, sulphate ions, sulphur, and arsenates.