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Leaching is the process of a solute becoming detached or extracted from its carrier substance by way of a solvent. [1] Leaching is a naturally occurring process which scientists have adapted for a variety of applications with a variety of methods.
Leaching is a process widely used in extractive metallurgy where ore is treated with chemicals to convert the valuable metals within the ore, into soluble salts while the impurity remains insoluble. These can then be washed out and processed to give the pure metal; the materials left over are commonly known as tailings .
After leaching, the leach liquor must normally undergo concentration of the metal ions that are to be recovered. Additionally, undesirable metal ions sometimes require removal. [1] Precipitation is the selective removal of a compound of the targeted metal or removal of a major impurity by precipitation of one of its compounds.
It is the most commonly used leaching process for gold extraction. [1] Cyanidation is also widely used in silver extraction, usually after froth flotation. [2] Production of reagents for mineral processing to recover gold represents 70% of cyanide consumption globally.
Solvent extraction and electrowinning (SX/EW) is a two-stage hydrometallurgical process that first extracts and upgrades copper ions from low-grade leach solutions into a solvent containing a chemical that selectively reacts with and binds the copper in the solvent.
Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent), and may refer to: Leaching (agriculture) , the loss of water-soluble plant nutrients from the soil; or applying a small amount of excess irrigation to avoid soil salinity
In 2011 leaching, both heap leaching and in-situ leaching, produced 3.4 million metric tons of copper, 22 percent of world production. [8] The largest copper heap leach operations are in Chile, Peru, and the southwestern United States. Although heap leaching is a low cost-process, it normally has recovery rates of 60-70%.
This is achieved in practice through a process called double leaching. The calcine is first leached in a neutral or slightly acidic solution (of sulfuric acid) in order to leach the zinc out of the zinc oxide. The remaining calcine is then leached in strong sulfuric acid to leach the rest of the zinc out of the zinc oxide and zinc ferrite.