Leeching (Electro-winning)

Leaching and electrowinning are critical processes in gold mining used to extract and purify gold from its ores or concentrates. Here’s an explanation of each:

1. Leaching

Leaching involves using chemical solutions to dissolve gold from ore. The most common leaching method is the cyanidation process, where a cyanide solution is used to extract gold. The steps include:

• Crushing and grinding: The ore is crushed and ground to increase surface area for chemical reactions.
• Leaching process: The ore is mixed with a cyanide solution in tanks, heap leach pads, or vat leaching systems.
• Gold dissolution: Cyanide binds with gold to form a soluble complex, usually gold-cyanide (Au(CN)₂⁻), allowing the gold to be dissolved into the solution.

2. Electrowinning

Electrowinning is a purification step that follows leaching. It uses an electrochemical process to recover gold from the cyanide solution:

• The gold-laden solution from leaching is transferred to an electrowinning cell.
• A current is applied through electrodes in the cell, causing gold ions in the solution to deposit onto the cathode (usually made of steel wool or a similar material).
• Gold accumulates on the cathode, while impurities remain in the solution.
• The cathodes are later processed to extract the purified gold.

Combined Process:

• Together, leaching and electrowinning form a system to efficiently extract and recover gold.
• Cyanidation dissolves the gold, and electrowinning retrieves it in a concentrated, solid form ready for smelting or further refining.

These processes are popular because they allow for the recovery of gold from low-grade ores and complex mineral deposits that would otherwise be uneconomical to process. However, environmental concerns, particularly related to cyanide use, require strict controls and regulations.