Alkali metal and alkaline earth metal cyanides are cyanidation of a solvent. Commonly used in the industry are sodium cyanide, potassium cyanide, ammonium cyanide, calcium cyanide and the like. The choice of cyanide in the industry mainly considers the relative solubility of the solvent to gold, the stability, the effect of impurities contained on the dissolution of gold, and their price. The relative solubility of several cyanides to gold is shown in the table below. The ability of cyanide to dissolve gold relatively Molecular formula Molecular weight Metal valence Relative consumption when equal solvency Relative solubility of KCN (in 100% KCN) NH 4 CN NaCN KCN Ca(CN) 2 44 49 65 92 1 1 1 2 44 49 65 46 147.7 132.6 100.0 141.3 The relative solubility of these cyanides to gold is determined by the amount of cyanide per unit weight of cyanide and also by the valence of the metal in cyanide and the molecular weight of cyanide. W Shape Crystallizer,Vacuum Crystallizer Working,Pharmaceutical Crystallization,Continuous Crystallization Equipment WUXI ZHANGHUA PHARMACEUTICAL EQUIPMENT CO., LTD. , https://www.filterdryer1976.com
These four cyanides can be arranged in a stable size in the air containing CO 2 :. But in terms of price, it is the most expensive, the second, and the cheapest.
The most commonly used in the industry is sodium cyanide.
In recent years, an industrial agent of cyanide has also been used. It is prepared by melting a mixture of calcium cyanide, salt and coke in an electric furnace. When a cyanide melt is used, the consumption is 2 to 2.5 times that of sodium cyanide, but the price is low, which can offset the cost of consumption and storage. Cyanide melts typically contain about 45% calcium cyanide and contain impurities that are detrimental to the cyanidation process, such as soluble sulfides, carbon, and insoluble impurities. In order to remove these impurities prior to use, shall melt cyanide solution strongly inflated to destroy soluble sulfide, or added to the solution and turn it into a soluble lead salt Mei be lead sulphide precipitate, then, the lead sulfide, carbon and other Insoluble impurities are separated by clarification. The clarified solution was used for cyanide leaching.
The sodium cyanide commonly used in production contains less impurities and the purity can reach about 94-98%. Theoretical consumption of sodium cyanide is 0.49 grams for 1 gram of pure gold, but industrial production is often used in amounts up to 20 to 200 times the theoretical amount, mainly due to mechanical losses, decomposition and volatilization and other impurities.
Cyanide commonly used in cyanide gold extraction and their applications