Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal

Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal2017-04-04T06:57:46-04:00
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Will Hypochlorite in Cyanide Detox results in gold precipitation - lost (5 replies and 3 comments)

2 years ago
Subhash-Kumar-Roy 2 years ago

There is an issue with the CN ppm in the tailings pond, two camels got into the pond area with one camel dying from drinking the water (gate to pond was left open) it is now at 100ppm where the environmental limit is only 10ppm, we currently sprinkle powered Hypochlorite onto the tailings filter cake discharge, currently there is 1.5 g of Au in the solution in the pond, there is a reluctance to dose the solution in the pond to lower the levels of CN for fear of losing the Au.
Currently we are pumping the tailing clear solution back from the pond to be processed in the Merrill Crowe (MC). Long term with the Merrill Crowe now recovering as per design most days the losses to tailings should be lower going forward and doing some CN destruction as it is filtered may be the best option, if the tails are truly tails this should not present an issue.

Installing a tank or two at the plant to dose the pond with a Hypochlorite solution will slowly lower the pond ppm, there is presently a pump at the pond that returns water to the plant it could be used to pump to the future dosing tank and have the discharge return to the opposite side of the pond this would slowly dose the pond and start to lower the ppm over time, even if a small amount was taken from the water being pumped into the plant for Au recovery and this returned it would slowly lower the ppm.
Each time the plant is down the focus should be to pump as much as is possible to the Merrill Crowe from the pond and return the barren treated back to the pond.
Currently the leach tanks are running at 1000ppm CN which is in the 800 to 1000 range normally seen in Merrill Crowe plants.

QUESTION: Will the addition of Hypochlorite to the tailings pond to destroy cyanide cause the gold already in solution to precipitate?  

I think not.  Looking for confirmation.  Thank you.

Javier Ramirez
2 years ago
Javier Ramirez 2 years ago

Dear Subnash,

Most probably your process lacks the CCD component.

If interested, I can send you a process flowsheet and mass balance of a suitable system that we are offering to the gold/silver industry.

Please send me your email address and we can do it for your benefit.


Javier Ramirez

Richard S
2 years ago
Richard S 2 years ago
1 like by David

Hypochlorite will destroy free cyanide.  The gold cyanide complex is a strong complex so should survive mild hypochlorite treatment.  You do not mention the Ag content of the tailings solution.  Usually Merrill-Crowe is employed where there is more silver in the ore to be leached.  Recycling free cyanide back to your plant is economically beneficial so destroying free cyanide in the bond has both a cost for hypochlorite and for replacing the lost free cyanide.  Increasing your recycle of pond solution would be beneficial.  Another thought, if your silver content in your tailing solution is fairly low, you could consider putting some carbon columns on the tailing dam and recycle tailings solution though them to deplete the gold and silver content of the pond solution.  You could put a couple of CIP colums on the tailings output to capture the precious metal content prior to release to the pond.  Periodically changing the carbon as it becomes loaded would be required, but you don't need to strip the carbon as you could send it to a custom stripper on your behalf.  If warranted, you could later install your own stripping system.  You should be able to test the dosing of hypochlorite and monitor the remaining gold cyanide content in the lab prior to doing it on the pond.  It should be a pretty simple lab test to do that, which I would recommend prior to doing it on the pond in any event so you can establish results and dosing parameters beforehand.


2 years ago
Subhash-Kumar-Roy 2 years ago

There is no Ag in this plant. It is a very high grade gold feed ie: Merrill Crowe.

Thank you so  much.

Richard S
2 years ago

The commentary about using carbon to recover the remaining gold content and setting up a test in the laboratory are still pertinent. Carbon will give you a better barren than a CCD wash circuit with the pregnant solution going to Merrill-Crowe.

2 years ago

Yes, i really like the CIT idea Carbon-in-Tails

Peter J
2 years ago
Peter J 2 years ago

Don't know where you are operating but in most countries not locking a gate around a cyanide recovery pond would be a criminal offence.  Where such dams are normally used not only must there be a double fence with all gates locked but also a spillage catchment area in case heavy rainfall causes the dam to overflow.

2 years ago

Thanks Peter. We are in a 4th World area.

2 years ago
Subhash-Kumar-Roy 2 years ago

Hi, we assayed a sample of the Pond solution and then add Hypochlorite and re-assay for Au content.
Results from test show that there is no drop in the Au values, several doses were tested after starting Au assay was taken over two-time periods ultimately with the CN ppm being at 0 with no change in gold assay.


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