Advice on Leaching 1 AT

[rbgold]

I am leaching 1 AT of ore with a 1/2 clorox 1/2 vinegar solution. I have been using activated charcoal to capture the gold. So far the results have been from .5 to 2.5 grams per ton AU. I was wondering if removing the magnetics before doing the leach would help? Also would soaking the ore sample in Hydrogen Peroxide before leaching help? Would these two things or anything else help increase my gold level?.

 

[Deano]

Your leaching assay method must be the same as what you are looking to use in larger scale, if it is not then you might as well just get a fire assay or aqua regia digest done.
In larger scale on ores you really only have the method of cyanidation, chloride leaches on an ore will chew up your oxidant and acid at a great rate and be uneconomical.
If you cannot get permitted for cyanide you have the option of using ferro/i cyanide leaches until such time as this loophole is closed.
Most present day ores have the precious metal values associated with sulfides, it is possible to concentrate these sulfides by gravity or preferably by flotation.
These concentrates can be either sold or carted away for toll treating at a facility which is cyanide permitted or approved for smelting.
The gold grade in these concentrates will usually permit high haulage costs so you do not just have to find an operation locally.
Deano

 

[rbgold]

Thank You for taking the time to answer. I sent duplicate samples for cyanide testing, they showed .03 ppm, and samples for aqua regia testing showed single digit ppb. Fire assays have shown .10 to .20 oz/ton AU. I believe that I am working with micron gold. I have a small testing Wave Table, however any gold seems to go with the water. So I believe flotation is the answer, and I will contact the lab I am using and see what they can do for me. Also can froth flotation be done on site? Rich

 

[Deano]

If the gold was in sulfides, aqua regia testing should have shown numbers near the fire assay numbers.
I suspect that you have a re-adsorption problem in that the solubilised gold complexes are back loading on to a component of the ore.
What points to this is the gold cyanide numbers being higher than the gold chloride numbers.
Gold cyanide is slower to re-adsorb than gold chloride.
The most likely culprit is carbon in the ore.
Test for this by running the cyanide leaches in bottle roll as CIP, make sure that the carbon used is fresh and has all of the carbon dust rinsed off.
At the end of the leach the liquor is analysed and the carbon is ashed and analysed separately.
Usually you run several such leaches at 1, 3, 6 and 24 hours to see when the gold is actually leached.
If your results show an increase in gold recovered then you have a different problem requiring further testing to optimise the carbon levels in the leach at the time of maximum recovery in the timed leaches.
Deano

 

[rbgold]

Deano, Thanks for your help. I will let you know how it works out.