Silver extraction by cyanidation
Cyanidation is a method of extracting silver from ores, in which metallic silver is leached from ground ore, usually with a combination of sodium cyanide and lime. This method is the most economical way to extract silver from ore because it involves little to no energy expenditure.
The gold cyanidation process involves leaching the ore in a sodium cyanide solution which acts as an oxidizing agent. The metallic silver reacts with the cyanide solution in a series of reactions which produce silver ions and sodium ions. The reactions between silver and cyanide are similar to those for gold; however, in the case of silver it is a much weaker leach.
In the second step of the process, these silver ions will be converted to silver metal. The basic process involves the addition of a reducing agent such as zinc, iron, or copper to the leached ore. This reduces the silver ions to silver metal which is removed by either a filtration or precipitation process.
The next step involves recovering the silver from the solution and concentrating it. This is done by either electrolysis or, more commonly, fractional crystallization. The crystallization process involves the precipitation of silver compound solids from the solution which can then be filtered and the remaining silver is collected.
Finally, the concentrated silver is obtained in a stable form. Depending on the process used, the sludge produced may be smelted and cast as a metal bullion or otherwise processed further to obtain silver particles or crystals.
The cyanidation process is relatively simple, cost-effective, and versatile for extracting silver from low-grade ores. It is also known to be lack environmental footprint due to its lower water consumption and lack of significant wastewater treatment requirements.
The cyanidation process of silver extraction from ore has a long history, with useful applications extending from the 19th century up to the present day. In the 21st century, modern advances in the process have helped to make it even more efficient and effective. The process is still widely used for extracting silver for a variety of industrial and practical uses, including jewelry and electronics.
