Aqua regia of Lead- copper flotation concentrates

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Quwannar

Active member
Joined
May 26, 2017
Messages
35
Dear Friends;
İ prepared Aqua Regia (AR) solution of Pb-Cu rougher concentrates ( 57% Pb and % 19 Cu) to test the gold presence with stannous chloride.
Procedures as follows
- 20 gram concentrates
-250 ml of AR (62.5 ml HCL of 33 percent and 187.5 ml of nitric acid of 67 % percent strength)
- İ contiuned in 30 minutes at simmering hot until red fumes of Nitric Acid is completely driven off and white fumes of HCl appears.
- İ let solution to cool down in room temperature. There was no any fizing in AR solution.
- i did not make denoxing and i did not filter the pregnant solution.
- i picked up 2 ml of pregnant solution in white spot plate.
- when a drop stannous chloride in spot plate İ saw very dark and dense black color like a ink. A few minutes later dark color disapered ( due to excess nitric) Then once more a drop of stannous chloride and i saw again same dark and dense color.
- i diluted 2 ml of pregnant solution with 1 ml tap water..
- when first drop of SnCl2 meet with pregnant solution at first seconds İ saw dense cassius of purple with dark black color.
Can there be palladium in Pb-Cu concentrates..
Any comment would be appreciated....


-
 
Dear Lino1406;
Would you please give the reasons in detailed why İ cant expect the gold in Pb-Cu concentrate above mentioned. The raw ore has already 19 pmm of gold content. This ore is a polly metalic sulfides ore. İ am trying to test on the flotation concentrate if it has a gold or not. As İ pointed out above, SnCl2 test on Aqua Regia gives very dark black) color together with purple cassius. Could reason of colors be palladium? Could Pb-zn cause this colors on spot plate that İ saw.
Thank you very much again for your explanations.
 
I presume that you transposed the volumes of nitric and hydrochloric acid in your original post, you would usually run 1:4 rather than 1:3 ratio.

When the fumes change to white you usually give it a further 5 - 10 minutes simmering to drive off the last of the nitric.

Your final volume after cooling should be 150 - 200 ml.

The solution will contain substantial levels of divalent metals, these are what causes re-disolution of gold values, not excess nitric.

You would expect substantial bubbling reaction when adding the cons to the aqua regia.

If you want to use 20 gram samples it is better to run two 10 gram samples to ensure complete digestion and retention of the digested metals.

Nothing beats AAS for being sure of the metal grades, ICP will often have dropout of values at the dilution stage when assaying complex material such as float cons.

Deano
 
Deano said:
I presume that you transposed the volumes of nitric and hydrochloric acid in your original post, you would usually run 1:4 rather than 1:3 ratio.

When the fumes change to white you usually give it a further 5 - 10 minutes simmering to drive off the last of the nitric.

Your final volume after cooling should be 150 - 200 ml.

The solution will contain substantial levels of divalent metals, these are what causes re-disolution of gold values, not excess nitric.

You would expect substantial bubbling reaction when adding the cons to the aqua regia.

If you want to use 20 gram samples it is better to run two 10 gram samples to ensure complete digestion and retention of the digested metals.

Nothing beats AAS for being sure of the metal grades, ICP will often have dropout of values at the dilution stage when assaying complex material such as float cons.

Deano

Dear Sir Deano;
İ mistyped volume of HCl instead of H2NO3 in aqua regia.
As you pointed out your instructions at your previous post as You advised, İ prepared 250 ml full strength Aqua Regia 1 volume H2N03 and 4 volume HCl....
İn fact, İ did not make a mistake in running of experiment. Sorry for that. Now İ am understanding that Mr. lino1406 warnings.
İ sent samples of liquour to AAS. And İ will share the results of it here with you.
As for preparing of aqua regia of float concentrates, due to high metal content, Do you think that the amount of sample should be around 10 grams in terms of digestion.. When İ completed AR at around 40 minutes there was still a little bit fizzing and bubbling on surface of AR.
Meanwhile, what about AR shelf life? İf the beaker of AR expose to air in a few days what about AR strength? Does it loose its strength?
Dear Sir Deano;
İ made some experiments on thermal decomposition of sulfide concentrates at 142 C with ammonium chloride and Calcium Ammonium Nitrate (ordinary CAN fertilizer has no denotion properties) 1;2 1;3 and 1;4 ratio. At 1;4 ratio İ saw that pyrite, chalcopyrite and galena was fully decomposed. Solid molten syrup was fully and easliy dissolved both in HCL and in water. Can this liquor be re-leached with hypochlorite leach method.?
Any comments would be appreciated.
 
If you have reactions still occurring at the end of the digest then you have two options.

Either use smaller sample sizes, 5 to 10 grams, or add further nitric acid at the end of the digest and redigest.

At the end of the digest stage there should be no reactions occurring.

Always approach aqua regia as if it has no shelf life at all, make it up immediately prior to use.

Do not use old pre-made solutions.

The only way to see if the leach system has totally digested sulphides is to actually try it.

I would be very careful at the addition of the hypochlorite leach stage, there is a good chance of violent reaction with any residual nitrates.

Apart from this, if the sulphides have actually fully dissolved, then a hypochlorite leach should dissolve any gold present.

A hypochlorite leach on its own should also dissolve the sulfides, a close check on pH and an excess of hypochlorite are needed.

Deano
 
Reminder: Stannous chloride positive test ends with black/brown precipitate and not vanishing black as described
 
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