Conflict in results of cyanidation and aqua regia leaching of gold

[aghilhaghdadi]

Hi
I am a graduate student in mineral processing.
I have a gold ore that gold does not desolve in cyanidation, but it desolves (at about 1 ppm Au) in aqua regia (analyses by AAS)
I am not sure if the sample contains any gold because Fire assay does not show any gold too.
I would appreciate if any one can tell me if the result obtained from aqua regia is correct or the one from cyanidation. and why?

Thanks in advance.

 

 

[anachronism]

Are you asking us to complete your final dissertation or are you actually doing this to get gold?

 

[aghilhaghdadi]

Are you asking us to complete your final dissertation or are you actually doing this to get gold?

my project is to make sure there is no gold in this sample and this is not an academic work.

 

[anachronism]

OK, are you therefore attempting to obtain a 100% effective leach?

 

[aghilhaghdadi]

OK, are you therefore attempting to obtain a 100% effective leach?

Well, I'm just trying to figure out if there is any gold in this sample at all. And after making sure that there is some gold contained in the sample, try to exploit the gold in a suitable and affordable manner.

 

[anachronism]

I assume that you ran your cyanide leach solution through the AA and got zero?

 

[snoman701]

At 1 ppm aren’t you near the limits of detection?

Either way, read deanos posts. There are ores that are not well smelted or leached with cn because of refractory base metal oxides.

What methods of fire assay have you tried?




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[rickzeien]

At 1ppm the sample equates to 1 gram of gold in 2200 pounds of ore. (Metric ton)

I would be rrally surprised if there is cost effective recovery meathod.

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[aghilhaghdadi]

I assume that you ran your cyanide leach solution through the AA and got zero?

If you mean by AA ,atomic absorption, then yes, exactly, other wise I am not sure what AA means.

Is it possible that presence of sodium or iron in ore caused different Results in determination of gold by atomic absorption in cyanidation and aqua regia leaching?

 

[aghilhaghdadi]

At 1 ppm aren’t you near the limits of detection?

Either way, read deanos posts. There are ores that are not well smelted or leached with cn because of refractory base metal oxides.

What methods of fire assay have you tried?

I'm not sure. I think the gold grade is about 0.5 ppm
I used sodium carbonate and lead oxide for fire assay because the ore has Silica .

 

[Lino1406]

The gold is generally trapped in sulfides. To free it, incinerate at 800C or rinse with concentrated H2O2 (a deep boiling should result)

 

[aghilhaghdadi]

The gold is generally trapped in sulfides. To free it, incinerate at 800C or rinse with concentrated H2O2 (a deep boiling should result)

Thanks for responding, but:
I've already done diagnostic leaching using HCl, H2SO4, HNO3, and HF, sequentially; and the results gave no gold at all! but the result of aqua regia leaching was different (1 ppm of gold). The challenge here is how this is possible and what do make these results to come up?

 

[anachronism]

The gold is generally trapped in sulfides. To free it, incinerate at 800C or rinse with concentrated H2O2 (a deep boiling should result)

Thanks for responding, but:
I've already done diagnostic leaching using HCl, H2SO4, HNO3, and HF, sequentially; and the results gave no gold at all! but the result of aqua regia leaching was different (1 ppm of gold). The challenge here is how this is possible and what do make these results to come up?

The basic chemistry of a CN leach vs an AR leach should tell you that. I'm not being cryptic, but if you think about your raw material and the way both processes work you should be able to see why.

Go on- work through the chemistry and let me know your thoughts. 8) 8)

Jon

 

[Deano]

When using AAS to determine the gold level in an ore from an aqua regia leach you must always perform an organic extraction first and then analyse the organic fraction.

Usually the aqua regia will dissolve iron from the ore which will read as gold in a direct aspiration liquor sample even when background correction is used.

This is important when you are looking for low levels of gold.

The usual organic extractant used is DIBK / 1% aliquat 336 and the gold is extracted at a ratio of 10:1 liquorrganic.

The extraction is done in an 50 ml extraction tube, usually 50ml liquor to 5ml DIBK and run for 100 shakes.

Pure DIBK/aliquat solution is used for the zero reading and read against standards made up in the same organic solution.

You treat AAS gold readings of less than 0.010 abs with great suspicion. Always use background correction even on organic samples.

Deano