Problem dropping gold

[chrisv]

HI all, its been a while since I've been on here as I found a full time job since which has consumed large amounts of time but things seems to be settling a bit and I've found time for my hobby again

Any way, need some advice plz.
After not refining for over 18months I've managed to make time again.
I processed some 14lbs of sim cards which have seem to have gone wrong.
I was advised to process them as whole cards which I did after spending large amounts of time peeling off the foils
from at least half the 14lbs. Anyway, I went in with straight AR as suggested by a fellow member as I had never dome sims before.
After digesting the gold from the cards, I denoxxed and then went onto dropping with sodium by nothing dropped and there is a chance I might
not have denoxxed properly?
The solution is really dark in color from the which I think may be the copper?

My process in short was as follows.
14lbs of cards in a 50/50 mix water and hcl and then 1-4th nitric.
Boiled untill I saw no green fumes.
Filtered solution
cooled down solution
Added 25grams sodium to boiling water and added to my solution
Nothing dropped after 1 day but solution still dark
Boiled solution down to half then added 50/50 mix of water and hcl
Boiled down half then added some 10grams sodium and water mix.
Still nothing.
Have been boiling solution down to half and then topping up with 50/50 mix water and hcl for the past week but still no joy.

 

[Palladium]

Try adding a piece of copper and give it a couple of days to cement anything out. Filter and catch all solids and run that through ar to recover your values.
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=52&t=15397

 

[martyn111]

stannous chloride?
you also make mention of adding sodium to your solution, do you mean sodium metabisulphite or did you use sodium?

 

[lazersteve]

Where did you get green fumes from? Sounds like you are using AR, so the fumes should be red.

Steve

 

[chrisv]

Thanks for all the assistance. I'll try chucking in some copper today once I return from work.

Yes, its def sodium metabisulphite, its got the pungent smell that I remember very cleary. Its knocked my breath away a few times before and
its something I will never forget

Steve, you right, the fumes may be red but I'm color blind lol! Hence the reason I got George with me at all times to assist when needed.

 

[nickvc]

Chris good to see you back on the forum.
To be sure that you have processed your material correctly I'm going to make a few obvious points.
Have all the metallics dissolved in your AR, if not the gold could have cemented back onto them.
If you have a large volume of solution the gold precipitation could take some time and if you still have free nitric it won't happen at all and then Palladiums suggestion would be the ideal route to follow, if you get vigorous fuming when you add your copper bar then there's your answer, you have excess nitric.
I wish you luck and look forward to seeing your results.

 

[butcher]

It sounds like you have a solution, full of base metals and free nitric acid, cementing on copper is very good advice.

When you say you boil it down to half and add back the water or HCl you are just re-diluting the free nitric acid in solution.( really not doing any good)

Evaporating it down to about half will not do much except maybe remove some water, but then you are just adding it right back, it does not sound like you are evaporating it down far enough to do any good at all.

You should never boil a solution with gold, you just want to heat it to slowly evaporate it, just to the point you see fumes but not to where the solution produces boiling bubbles.

Just heat it till fumes vapor off the solution so it will concentrate, as it concentrates the more volatile gases escape from solution, they are removed from solutions in order water first, then nitric, then HCl, they do not come off pure and the gas can be a mixture of these, (with aqua regia other volatile gases which form from mixtures of the acids and these can also escape if they have not already reacted with metals in solution), at first mostly water evaporates, and the other acids concentrate when these acids concentrate they azeotrope then the fumes will be the same concentration of that acid, in aqua regia we can vapor off the water, then the nitric as we azeotrope HCl (we use excess HCl to keep our gold in solution), (and not cook it to chloride salts) this way we can concentrate the solution down to a point to drive off most all of the free nitric, and still have enough HCl to keep our gold in solution, we will lose some HCl in this evaporation process, we want to concentrate the solution down far enough to drive as much nitric acid out as possible without cooking out our gold, at this point we have most of the nitric evaporated but not all, at this point we really do not want to add water as we would just dilute the remaining nitric. Making it harder to finish removing from solution, we add HCl to re-wet solution, if nitrates formed the acid can make these back to nitric (we may see a red NOx cloud at this point), the HCl added is 68% water so this also dilutes the solution and any remaining nitric in solution, so we do not want to add much, this way our solution is still fairly concentrated (has HCl to keep or gold in solution), so we again evaporate the water we added with this acid, since the HCl was close to azeotrope it does not take long to remove water, and more of the nitric acid with it, as the HCl and our gold chloride concentrate, we do this for a third time to insure we have remove all of the free nitric acid.

Nitric acid should only be added as needed when dissolving gold, the best way its to calculate how much acid is needed and add the HCl and then add nitric in very small proportions, with heat, and stop adding nitric acid before all of the gold finishes dissolving, then concentrate solution (which will dissolve more gold as the nitric in solution concentrates.

Sulfamic acid will remove nitric acid from solution.

Another option is adding gold, which can also use up free nitric acid from solution.


You really need to get Hokes book back out and read it again, and get caught back up on your reading of the forum.