Leaching is the process of extracting metal from the ore for refinement. Leaching is also referred to as the metallurgical process. It is also simply called metallurgy.
The leaching process of extracting metal from the ore will depend on both the ore’s nature and the metal. There are no universal techniques used for extracting metal.
Generally, ores are found deep within the earth. There are a few that occur within the first few meters under the surface. Mining is the term that is used to describe the process of removing the ores from the earth. Ores that are near the surface of the earth can be dug out directly. This process is referred to as open pit mining. Deep mining is defined as removing ores that are located at greater depths.
Typically the ore that is extracted will be in a large lump, which makes it necessary to break it into smaller pieces. This is done by hammering or using some type of jaw crusher. After the ore is broken into smaller pieces it is then pulverized until it reaches a powdered state.
Types of Processes to Remove Impurities
There are several different processes that can be used to separate the undesired parts of the ore. Leaching is just one of the many processes. Some of the other types of process include:Hand Picking: this is used for removing large impurities, but is extremely slowGravity Method: this method is commonly used for oxide ores and uses a running stream of water to wash away the impurities.Magnetic Separation: This type of separation is typically used with hematite ore. It is done by dropping the powdered ore onto a conveyer belt that has a magnetic roller. The ore will stick to the magnet and the impurities will fall away.Froth Floatation: the ore is mixed with water and pine oil. The mixture is shaken and the froth will carry the particles to the surface.Leaching Process
The leaching process is used with many different types of ore. Leaching uses chemicals to treat the ore. The chemicals react with the ore and dissolve the active component. There are several reagents that are used for this process, depending on the type of ore. Typically, oxide or sulfide is used as feed for the leaching process.
For example, to recover some precious metals such as silver, the leaching process is used. Using a cyanide process, the silver can be extracted from its ore. The powdered form of the ore is treated with a solution of sodium cyanide. An air current is sent through the solution. The silver in the ore will be dissolved because of the formation of soluble sodium. This solution is then treated with a zinc scrap that is used to recover the silver from the solution.
Gold ore is extracted using a leaching process as well. The solution KCN is used to dissolve the ore and then the gold is recovered from the solution using electrolytic or precipitation methods.