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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Gold recovery from calcined tailings (4 replies and 1 comment)

T
Scotman
7 years ago
Scotman 7 years ago

Does anyone have experience with the recovery of gold from calcined tailings? The material is the waste product from an Edwards roaster. The host ore is arsenopyrite - very refractory. Normal cyanidation (at elevated temperature levels) only recovers 30% of the gold. Biox does not work. All help will be greatly appreciated.

 

P
Pabloski
7 years ago
Pabloski 7 years ago

Maybe passivation coatings?

M
Mike Rockandel
7 years ago
Mike Rockandel 7 years ago
1 like by David

After POX or  roasting the goal is to produce a porous iron oxide offering free passage for CN.  Maybe the calcining conditions for this reject material induced hematite densification and shrinkage reducing the porosity.  I would think that a look at surface morphology (SEM) may provide some information. If the above is correct, there are no really attractive options, not much different than gold encapsulated by silica.

R
sbccbalaji
7 years ago
sbccbalaji 7 years ago

You From Where and how much quantity of tailings you have and what is the assay balance?

T
Scotman
5 years ago

you can contact me at afmin@mail.com

G
GeoffC
7 years ago
GeoffC 7 years ago
1 like by David

There could be a number of reasons for low cyanide recoverable gold in Edwards roaster calcine. One of these could be associated with insufficient roasting. The Edwards roaster relies on having sufficient sulphur present to roast properly. If there is insufficient sulphur additional heat is required. If the concentrate was not roasted properly then the original arsenopyrite may still be present and prevent cyanidation of the contained gold. Re-roasting to remove the sulphur would overcome this but arsenic fume generated means this  is rarely done in modern times. POX or BIOX methods are more typically used or if you are lucky enough Ultra fine grinding (UFG) may liberate enough gold for cyanidation to work. 

Conversely too much sulphur in the concentrate can lead to high temperatures during the roast and if there is insufficient oxygen present (controlled by the ports along the side of the roaster) hematite can form as mentioned above. Typically these calcines are grey in colour not a more normal rusty red colour. Fine grinding can over come this to some extent if the gold can be exposed to the cyanide solution. 

Another potential cause of the low recovery could have been high temperatures and a "dirty" concentrate resulting in sintering with quartz minerals fusing to form an impervious calcine. There are a number of these calcines around the world that still contain high gold values as they do not respond to UFG and so cyanide recovery is limited.

You will have to do a bit more investigation to determine what the actual cause of the low recovery is.

 


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