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[4] [11] The leaching is typically described by solute transport models, such as Darcy's Law, mass flow expressions, and diffusion-dispersion understandings. [4] Leaching is controlled largely by the hydraulic conductivity of the soil, which is dependent on particle size and relative density that the soil has been consolidated to via stress. [4]
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.
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 .
It is the most commonly used leaching process for gold extraction. [1] Cyanidation is also widely used silver in extraction, usually after froth flotation. [2] Production of reagents for mineral processing to recover gold represents 70% of cyanide consumption globally.
The origin is the word lixiviate, meaning to leach or to dissolve out, deriving from the Latin lixivium. [4] A lixiviant assists in rapid and complete leaching, for example during in situ leaching. The metal can be recovered from it in a concentrated form after leaching.
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%.
In-situ leaching (ISL), also called in-situ recovery (ISR) or solution mining, is a mining process used to recover minerals such as copper and uranium through boreholes drilled into a deposit, in situ. In-situ leach works by artificially dissolving minerals occurring naturally in the solid state.
Podsolisation is an extreme form of leaching which causes the eluviation of iron and aluminium sesquioxides. [1] The process generally occurs in areas where precipitation is greater than evapotranspiration. The minerals are removed by a process known as leaching.