Heap leaching is an industrial mining process used to extract precious metals such as gold and silver from ore. In this process, ore is crushed and placed on a leaching pad. A cyanide solution is then introduced to the pad in order to extract the metals into solution form, which can then be recovered.
Heap leaching has been around for quite some time, but has greatly increased in popularity in the last few decades due to its low cost, effective production, and environmentally-friendly nature. It is now used in around two-thirds of gold and silver production worldwide.
The most common ore used in heap leaching is gold ore, but other metal ores can also be successfully processed. The process begins with the crushing of the ore, which is necessary in order to increase the surface area available for leaching. This crushing is usually done using a jaw crusher or a cone crusher, although there are other types of crushers that can be used, such as impact and roll crushers.
After crushing, the ore is placed on a liner and then onto the heap leach pad. Once on the pad, the ore is sprayed with a cyanide-containing solution. The solution will percolate through the ore, dissolving the metal as it makes its way through. The leached solution is then collected and treated with a dilute acid or in some cases, a neutralizing agent.
The cyanide solution works by dissolving the metal, which is then drawn away into a separate pool. This pool is referred to as a pregnant solution, and the metal is separated out of the pregnant solution through a desorption process. Once separated, the metal can then be taken away and used in other applications.
Heap leaching is used to extract precious metals due to its low cost. It is considered to be one of the most cost effective methods because it requires minimal infrastructure and its environmentally friendly nature. It is also very effective, with some of the richest gold grades being processed through the heap leach method.
Despite its cost efficiency and effectiveness, there are some drawbacks to the heap leach method. One of the main drawbacks is that it is a slow process, with the rate of release of metals from the ore being much slower than other methods of extraction. It is also not suitable for all types of ore, and can be ineffective in processing certain types of ore. Additionally, due to it being an open process, there is a greater risk of environmental contamination, as chemicals can be released into the atmosphere as the ore is processed.
Heap leaching is an effective process for extracting precious metals, and is growing in popularity due to its cost efficiency and environmentally-friendly nature. However, it is important to be aware of the potential drawbacks which can arise when utilizing this method, as the risks of environmental contamination can be high.
