Sodium sulfide leaching
Sodium sulfide leaching is considered to be a kind of leaching method mainly applicable to oxidized gold-bearing ores. The advantages of using sodium sulfide for gold leaching are that the reaction rate is rapid, the corrosion of equipment is reduced, and the formation of gold-bearing precipitates makes gold extraction easier.
Sodium sulfide leaching can be divided into two categories: alkaline leaching and neutral leaching. Alkaline leaching refers to the leaching process in which the ore is treated with 10 - 30% sodium sulfide solution, and the alkalinity of the solution is adjusted to 10 - 13. Neutral leaching is a leaching method in which some or a small amount of sulfide is added to the solution, and the pH value of the leaching solution is 8 - 8.5.
When leaching oxidized gold-bearing ore with sodium sulfide solution, a series of reactions occur. As a result of acid-base reactions, the net reaction of cystine oxidation is that sulfur dioxide dissolved in water is converted to sulfide ions, and H+ ions are produced. The reaction of gold leaching is Au + 2Na2S + 3H2O → Au(S) + 2NaOH + 2H2S. At the same time, due to the oxidation reaction of the free cyaniding, the reaction of HCN formation includes H2S + O2 + H2O → S + 2H+ + 2OH- and 2H+ + 2HCN → HCN + H2O. When the reaction of pH adjustment is promoted, the formation is due to the fact that Na2S and H2S breakup reaction Anions formed by H2S + 2OH- → S + 2H2O.
In addition to the conventional leaching method, some new methods for the leaching of gold by sodium sulfide are also emerging. For example, micro-stirring leaching method, electrowinning leaching, etc., micro-stirring leaching method is a leaching method with the assistance of a micro-stirring device. It has the advantages of high leaching rate and uniform leaching, which can greatly accelerate the reaction under certain conditions; electrowinning leaching technology is a technology in which metallic gold is directly recovered from the leachate by electroplating.
In conclusion, sodium sulfide leaching is a kind of leaching method suitable for oxidized gold-bearing ores. It has the advantages of rapid reaction rate, low corrosion of equipment, and ease of gold extraction. In addition, some new leaching methods have also been developed, such as micro-stirring leaching and electrowinning leaching, which have better leaching and extraction effect
