Cyanide process is used in the extraction of: (a) \(\mathrm{Cu}\) (b) \(\mathrm{Al}\) (c) \(\mathrm{Zn}\) (d) \(\mathrm{Ag}\)

Metallurgy refers to the science and technology of extracting metals from their ores and refining them for use. Among the various metallurgical techniques, the Cyanide process stands out for its effectiveness in extracting precious metals like gold and silver from low-grade ores. This process involves several steps, including preparation of the ore, cyanidation where the metal is leached from the ore using a cyanide solution, separation of the metal-cyanide complex from the ore slurry, and finally, recovery of the metal.

The Cyanide process, also known as gold cyanidation or the MacArthur-Forrest process, revolutionized the metal extraction industry by allowing for the economic recovery of gold from very low-grade ore. It made the mining of previously uneconomical ores feasible, thereby vastly increasing the potential supply of gold and impacting the gold industry on a global scale.

Gold extraction is the focus of many metallurgical processes because of its value and rarity. The Cyanide process is particularly significant in the context of gold extraction. Here's how it works:

The finely ground gold ore is mixed with a dilute cyanide solution, which allows gold to form a soluble coordination complex known as gold cyanide. Oxygen is essential in this process to dissolve the gold. The resulting solution contains a gold-cyanide complex, which can then be filtered off and treated to reclaim the gold.

Key factors ensuring the efficiency of gold extraction using the Cyanide process include the pH level of the solution, the presence of oxygen, and the concentration of cyanide. Upon completion of the process, gold is precipitated from the gold cyanide solution, typically by adding zinc or by electrolysis, leading to the retrieval of pure gold.

Similar to gold, silver can also be extracted through the Cyanide process owing to its ability to form coordination complexes. The process for silver is somewhat alike to that of gold extraction and involves creating a silver-cyanide solution. Silver reacts with the cyanide solution to form a water-soluble argentocyanide complex, which can then be processed to extract pure silver.

It is important for silver extraction that the concentrations of cyanide and oxygen are carefully controlled to optimize the dissolution of silver and limit the dissolution of other metals. After the argentocyanide complex is separated from the leached pulp, it's reduced back to metallic silver by various methods, including precipitation with zinc dust or by electro-winning, ensuring the recovery of high-purity silver.

A coordination complex occurs when central metal atoms or ions are surrounded by molecules or anions, known as ligands. In the context of the Cyanide process, the gold and silver become central ions, and the cyanide ions act as ligands, forming coordination complexes.

The ability to form stable, water-soluble complexes with cyanide is a unique property of certain metals, and this attribute is leveraged in the cyanidation process. The metal-cyanide complexes, such as gold-cyanide \(\text{Au(CN)_2}^-\) for gold and argentocyanide \(\text{Ag(CN)_2}^-\) for silver, are relatively stable and can be separated easily from the ore. Understanding the chemical principles underlying coordination complexes is integral to improving and optimizing the Cyanide process for metal extraction.