Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

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Zinc dissolution in Merrill Crowe (1 reply)

J
John R
6 years ago
John R 6 years ago

I am compiling some data on Merrill Crowe circuits and are interested in how much zinc dissolves.  

I would expect zinc to go into solution as gold and silver are precipitated stoichiometrically, but generally a large excess of zinc is added.  Generally greater than 5 times stoichiometric zinc is added in the MC.  Does this excess zinc dissolve in the barren as a zinc cyanide complex or does it remain as zinc metal and report with the precipitated gold and silver?

Residual oxygen could oxidise the zinc as could the reduction of water to hydrogen.  This means that most of the zinc could potentially end up in solution.

Does any body have any plant data on zinc deportment in Merrill Crowe or perhaps a good understanding of what normally happens?

R
Richard S
6 years ago
Richard S 6 years ago

It has been my experience that there will be excess zinc in your precipitate.  While some zinc will dissolve and form a zinc cyanide complex and deplete free cyanide content in the barren leach solution, zinc will remain.  Adding sulfuric acid to the precipitate will remove much of the excess zinc from the precipitate and simplify smelting.  Alternatively or in addition, the precipitate after acid  treatment or before can be calcined to render remaining zinc as an oxide which will help in smelting to remove the zinc from the reduced metal and into the silicate slag.


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