Quick question before I make a mess

[siddharta]

Hi,

I have around 900g of CPU pins. When I desoldered them, SMD's were droped in my pins batch also.
I have plan to leach pins in 50/50 nitric to dissolve base metals. Can I leach whole batch and cement palladium later (with copper), or should I separate pins from SMD's?
Please tell me you can...

B.

 

[Marcel]

I would always prefer to seperate metals at an early and easy stage, than later with unknown results and additional problems. Just my general thought.

 

[butcher]

I agree mechanical separation is very important, and can help to eliminate trouble in the chemical separation stages.

 

[siddharta]

Yes I agree with you and I am trying to separate as much as I can. But it is what it is. I am still hoping that I can leach them mixed together.
Oh and is it normal when droping gold with SMB it develops strong sulphur smell?

 

[Geo]

try this. place the pins in a container and add hcl to cover them completely. warm and wait for all the action to stop. this is the solder dissolving. it will discolor the pins and they will be a dull grey when its done. dont worry, the gold is still there. remove the solution and drain the pins.rinse well and remove any sediment from under the pins. the pins now needs to be incinerated before the nitric acid bath. bring them to 400 degrees F and keep them there for a few minutes making sure they are all heated (roll them over so the top pins get hot too). let them cool and rinse with clean water. now you can send them through a nitric acid bath without making metastannic acid that will trap your foils and keep you from filtering your solutions. it may save you from losing some hair (if your like me, you want to keep all you have now :lol: ).

 

[siddharta]

lol Geo I am afraid that I'm heading your way...

This is my very first attempt to recover gold from CPU pins, so please be patiend with me... What happens with HCl that was used for solder removal?
I am such a idiot. I have monolithic capacitors (MLCC's) mixed with pins not SMD's...
So the question still remains unanswered... Can I treat them together or will I create a mess?

 

[Geo]

test the solution from the hcl bath with stannous chloride. if it is negative, treat and discard. if the MLCC's dissolve in the hcl, it may test positive for Pd. any sediment from the hcl bath will contain silver. if the MLCC's and resistors survive through the hcl bath, the nitric bath will extract any remaining values. after dissolution of the base metal in the pins, filter the solution to remove the foils.rinse the foils lightly and add the rinse to you nitric acid bath. finish rinsing the foils for processing. your nitric acid bath with have some values dissolved in it. you can selectively remove these if you know how. you can precipitate the Pd first and then cement any silver out as elemental silver using clean copper or you can precipitate the silver first using salt as silver chloride and then evaporate the solution to make the recovery of Pd easier.

someone else that does this on a regular basis may can help you more than i can. i seldom go the route you are taking.

 

[siddharta]

Geo thank you.

Btw today I droped gold from 810 grams of fingers (RAM and VGA, PCI). Yield was around 2 grams of raw gold.

This I believe is realistic yield? Around 0,25% from mass of fingers...

 

[siddharta]

Here is the update. And of course I managed to make a big mess... Here is what I did...

I had cca 600g batch (pins+mllc). I covered it with HCl and let it soke over night. I rinsed it well, incinerate and put into 50/50 nitric leach. However pins were undissolved, but there were fine gold foils and some gold dust. Should I re soke pins or leave them since I believe that most of the gold was recovered?
Color of the solution was like muddy water. Maybe Pd? I recovered foils and use HCl/cl method. Dropped the gold. All went fine.

Now I am stuck what to do next. I poured acid and wash water in a container (almost 2 liters)... My stannous test showed nothing. Even when I tested HCl/cl solution. I will make fresh one and test again. I will take some pictures also.

If test is positive to the Pd. Should I drop Pd with Al or Zn?

Any help would be much appreciated.

 

[Geo]

when you move from one chemical to the next, you must incinerate the material to avoid creating a weak AR solution. you can not rinse hcl nor nitric acid from material once it has been introduced. if you put the material through a hcl bath and then went to nitric acid without heating the material to over 250 degrees F for as long as it smokes rolling the material to insure all the material is heated, you did make a weak AR solution that more than likely dissolved some of the gold. this would have cemented back out on the remaining pins. any powder or dust should be collected and dissolved to test for values.once you start a dissolution, you should keep adding the active chemical until all base metal is dissolved.if you do it the way you did it this time again you will be sure to lose some of your gold.