AR gone wrong

[samuel-a]

hi everyone.

i have preperd a dilute AR solution to process a few sloted fiber CPU's and some female side of other CPU's (the one that on the board it self).
now, i added 100 ml of water, 50 ml of HCL... then i realized that i need anuther 50 ml HCL so i added it, but' i made a mistake and insted of HCL i added 50 ml of nitric, way way more then i needed.

now, when realized my mistake (no foam over or somthing), i added some more HCL.when every thing was dissolvd i started feeding the solution with high grade pins to combat the nitric, when there was no action any more to the pins, even when hot i stoped the additions.

filterd, boild down to syrup (and large amount of crystallization) and added HCL, did that 4 times.
then tripled the volume with water, let sit for the night, filterd, and added SMB.
the SMB foamed like crazy on contact with the solution, and there was no precipitation even after a few days, only white crystallization on the bottom...

nothing seems to work, the solution is very positive for gold, and i belive that in total i have in there about 1.5-2 grams of gold.

here's what i tried so far:
i added a copper bar to the solution for a night... nothing, only thin grayish cement on the bar.
then heat the solution to near boil and added copper powder, and all i got was huge amount of copper || chloride to precipitate. gold still positive in stu.
took a sample and loaded it with SMB... nothing, still positive.
took anuther sample and boiled down/HCL anuther 3 times, SMB... nothing happend, still positive.
took a sample added stannous chloride, got some precipitation of black powder and what seems to be colloidal gold, but the solution is still positive.
took a sample and dropped everything with aluminum, cleaned the residue with HCL boil (the wash tested negative for gold), washed with water few times, forced dry on hot plate, added water and nitric, everything was gone in solution... no gold powder... solution negative...

i'm absolutely lost on that one, and i'm struggling with it for more then a week now.
i would really appreciate the help, cous i think the next step is to throw down the drain....

thank you,
SAMUEL

 

[qst42know]

now, when realized my mistake (no foam over or somthing), i added some more HCL.when every thing was dissolvd i started feeding the solution with high grade pins to combat the nitric, when there was no action any more to the pins, even when hot i stoped the additions.

Did you still have metal left in your solution at this point?

If you removed solid remains of the high grade pins at this point I would expect most of the dissolved gold would have been cemented to them.

 

[samuel-a]

no, no meatl left in there to cement the gold, the solution is positive for gold.

 

[leavemealone]

i have preperd a dilute AR solution to process a few sloted fiber CPU's and some female side of other CPU's (the one that on the board it self).

How many CPU's,how many female slots?Did you cut the fingers off of the CPU's or did you put them in whole?I want an idea of how much actual gold you may be dealing with.Stannous chloride can test positive for gold even when there are very few parts per million,and is capable of giving you a false positive.Test again,using about 5 drops of each,solution and stannous,on a white plate.This time,after adding them together tap the plate several times lightly to make sure the two are well mixed,and set the plate aside for about an hour.Is it still positive?Or is it clear now?If its clear then you precipitated the gold when you added that copper bar over night,and chances are the gold(and silver,hence the grey) is in one of your filters or still on that bar,unless you rinsed it.
If it is still positive,I would either try to precipitate using copperas,or cement with zinc and start over.I would avoid starting over because of the large amount of base metals you will have to redissolve,consuming more chemicals.
Johnny

 

[samuel-a]

thank you johnny

i'll do as you suggested.
the stannous test solution has became a prime suspect in this mess.
erilier i rememberd that it tested positive on other AR batch that the gold was dropped from and was crystal clear.
i remember i added to it more SMB just in case but didn't got anymore ppt...

thank you

 

[qst42know]

If you still get a positive result, I would try what 4metals recommended for stock pot wastes and add a fish tank air bubbler and try the copper bar for a longer amount of time. I would guess the gold in solution has to come in contact with the copper and the continuous stirring should do the job.

 

[lazersteve]

Don't forget about the false positive from sulfurous acid (excess SMB in acid), looks brown, not purple, may smell of rotten eggs when testing.

Steve

 

[samuel-a]

thank you steve.

how can one eliminate sulfurous acid ?
heat? boil?

(beside the obvious of not aading to much SMB)

 

[Harold_V]

This one may be a no-brainer. If my hunch is correct, and the reaction you are getting is due to the sulfurous acid, there is no need to eliminate. Simply dispose of the material as you normally would.

Reason?

When you started adding pins (pins made of base metal, right?), what you likely did is cement any values that were in solution, so what you are seeing now is not a reaction to gold. To prove if that is the case, or not, using a spot plate, test another drop. Allow the test to remain in the spot plate for a short interval, then pour out the solution. If you DO NOT FIND a purple stain in the cavity, you had no gold, so you were not seeing a gold reaction.

You'll find the lost gold in your filter, along with the balance of the un-dissolved materials. Recovery is simple.

Harold

 

[samuel-a]

thank you guys,
the solution is indeed barren....
the task now is to find out where is the gold then...

 

[leavemealone]

to process a few sloted fiber CPU's and some female side of other CPU's

How many CPU's,how many female slots?Did you cut the fingers off of the CPU's or did you put them in whole?I want an idea of how much actual gold you may be dealing with.

This is one question I asked that you forgot to answer bud.I fear this may be the problem.You have been on the forum to know that a "few" slots are not going to yield hardly anything,so I can't imagine you just running a "few" as you said.But please give us an idea of how much material we are talking about.
Thanks,
Johnny

 

[samuel-a]

hi johnny, you are correct, i failed to answer.

it was about 8-9 CPU's and their cores.
15 female side with the plastics casing and pcb.
and about 50-70 grams of high grade pins.

i chopped them in to small pieces to fit all in the beaker.

now, i know not to expect much, and i know how to recognize very small precipitants and dilute solution.
it's not much, but i had my share of expirience with working with small amount and dirty solutions, it's the first time i can't seems locate my gold....

thank again

 

[Harold_V]

it's the first time i can't seems locate my gold....

I told you where your gold is. It's in the solids you filtered from the solution. Incinerate the residue that's in the filter (include the filter in incineration). Assuming you have un-dissolved particles, left from the pins, treat with dilute nitric acid until they have been dissolved. Rinse well, then go after the values with the solvent of choice (AR would be my choice). If my hunch is correct, and you cemented the gold by the base metals in the pins, the gold likely won't be recognizable. Doesn't mean it's not there.

If you have a reason to think that the solution might be difficult to filter, after you've given it a wash in nitric, and rinsed it well, you are well served to incinerate yet again, then give the solids a wash in HCl. That does more to eliminate problems than any other single thing you can do. After rinsing well, go after the values.

Harold

 

[eemtek]

next time you put in copper, try to lower the ph with sulfuric acid.

i personally drop the gold in troubles solutions with adding smb then stirring in aluminum powder.. then use 2 containers and keep pouring the liquid. its hard to explain the results unless you try it with stirring compaired to pouring..