Leaching (metallurgy)

Leaching is a process widely used in <a href="/facts/Extractive_metallurgy/TkszJ19Y">extractive metallurgy</a> where <a href="/facts/Ore/kgc9DssX">ore</a> is treated with chemicals to convert the valuable metals within the ore, into soluble <a href="/facts/Salts/lsSKwGpn">salts</a> while the <a href="/facts/Impurity/FfPvIRoB">impurity</a> remains <a href="/facts/Insoluble/kLE9h3Jb">insoluble</a>. These can then be washed out and processed to give the pure metal; the materials left over are commonly known as <a href="/facts/Tailings/g7TtDIJR">tailings</a>. 
Compared to <a href="/facts/Pyrometallurgy/VuhDQhUj">pyrometallurgy</a>, leaching is easier to perform, requires less energy and is potentially less harmful as no <a href="/facts/Gas/hVVAoodV">gaseous</a> <a href="/facts/Pollution/JRagxumQ">pollution</a> occurs. Drawbacks of leaching include its lower efficiency and the often significant quantities of waste effluent and tailings produced, which are usually either highly acidic or alkali as well as toxic (e.g. <a href="/facts/Bauxite_tailings/vPz9k55M">bauxite tailings</a>).
There are four types of leaching:[not verified in body]

<ol><li><a href="/facts/Cyanide/t0o8FMKI">Cyanide</a> leaching (e.g. gold ore)</li>
<li><a href="/facts/Ammonia/MtLtJFtz">Ammonia</a> leaching (e.g. crushed ore)</li>
<li><a href="/facts/Alkali/s6NqPGSP">Alkali</a> leaching (e.g. <a href="/facts/Bauxite/CJ10QPc6">bauxite</a> ore)</li>
<li><a href="/facts/Acid/FySU18n1">Acid</a> leaching (e.g. <a href="/facts/Sulfide/d8YMjLeu">sulfide</a> ore)</li></ol>
Leaching is also notable in the extraction of rare earth elements, which consists of <a href="/facts/Lanthanide/rt3XIRCl">lanthanides</a>, yttrium and scandium.

Leaching (metallurgy) open-in-new

Leaching (metallurgy)