Saturday, August 11, 2012

Hydrometallurgy

Some metals like gold and silver are extracted from their concentrated ores by leaching. They are dissolved in suitable reagents like acids or bases leaving behind insoluble impurities. The metal is recovered from the solution by crystallization. For Example, Silver ore is leached with dilute solution of sodium cyanide. Silver dissolves forming a complex, Sodium Argento Cyanide. The solution is further treated with scrap zinc to get the precipitate of silver.
Similarly, native gold is leached with potassium cyanide solution and it is recovered from the solution by addition of scrap zinc.

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