Regarding gold pin recovery..

[Melancholy]

Hi forum,

I've been a long time trawler of the forum, or whatever threads I had access to without an account, and would love to know if my thoughts are on the right track/viable.

Living in Australia, coming across chemicals can be a hassle, in particular strong acids (sulphuric and nitric), as well as nitrate salts. I have stacks of mobos and e-scrap that are slowly getting processed in my spare time, but I'm a little stumped with recovering gold from the pins. Digesting the plating substrate on the pins with a bubbled AP solution won't work anywhere near as well as it does for fingers, and having no access to sulphuric acid above ~32%, an electrolytic cell currently looks prohibitive, especially on a student's budget :roll:

I have access to HCl/Cl, SMB, a basic distillation/filtration set-ups, an appreciable amount of various other salts, solvents, equipment & tools - I've also become familiar with the chemistry and what's going on by processing the small batches of gold teeth and CPUs. I was thinking that a way I could get around electrochemical method for the pins is to chuck the pins into HCl/Cl, which should dissolve the gold and most of, if not all, the other metals the pins are made of. I could then cement out the gold and (I think) the Fe, Ni, using copper metal as the cementing substrate. At that point, I should be able to place the solid product into an AP or CuCl bath to remove the trash metals, leaving me with the gold I'm after, yes?

This method is definitely makework compared to the sulphuric cell, but it allows me to get the gold off of the pins without needing a sulphuric cell, nitric acid, or having to wait a millennium for an AP bath to peel the plating off itself. I was just wanting to bounce it off of some of the seasoned minds here before I go wasting all my pins. Does the method work as I'm thinking it would, or is there anything I could/should do to make obtaining the gold easier?

Thanks in advance

 

[GotTheBug]

You might find this thread helpful.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=53&t=1746&hilit=dallasgoldbug#p14972

I've built and have been tinkering with a similar rig, and results so far are decent. It does strip gold, even from sim cards, along with everything else.
So far in testing I've used it on ram cards and other pcb parts that have gold traces. It will even remove the solder mask and start on the copper after a bit.

Might be a good idea for you though.

Good luck and let us know how it goes.

 

[Geo]

Perhaps you don't understand copper chloride well enough. It will dissolve pin base metal as well as the base metals in finger boards. Keeping in mind that by converting a gallon of hcl to copper chloride and thereby dissolving the pins, it takes about 1 gallon of hcl as copper chloride to dissolve the base metal in two pounds of pins. Since the solution can be re-used, keep it healthy with additions of fresh hcl as the volume of solution drops.

 

[FrugalRefiner]

I was thinking that a way I could get around electrochemical method for the pins is to chuck the pins into HCl/Cl, which should dissolve the gold and most of, if not all, the other metals the pins are made of. I could then cement out the gold and (I think) the Fe, Ni, using copper metal as the cementing substrate.

When you cement with a metal, only the metals below it in the reactivity series are cemented. Iron and nickel are above copper, so copper will not cement them. Having said that, it would take a LOT of HCl/Cl to digest pins completely.

Dave

 

[Shark]

Couple of options as I see it:
1-Concentrate the 32% sulfuric and run it in a cell.
2-Keep using AP.

Both have advantages and disadvantages. If the pins are high grade and I had several of them a small cell would be good. If they come from computer motherboards and other lower grades, AP. I use AP because I find very few of the higher grade pins. With sunshine and an air supply it does a pretty good job. AP also has fewer hazards than concentrating sulfuric. Hot sulfuric is viciously aggressive stuff. I like my small cell on plated stuff, but low grades pins just don't warrant using it, I save it for jewelry and heavier plated stuff. AP, be sure to use a large enough volume for the amount of materials you have, keep it warm, mine sits in the sun all day, and run an air source into it. I use a large fish aquarium pump with dual outlets, and I can use it in two tanks at the same time when needed. I usually don't have to rush mine but normally a week in warm weather is enough to do the job.

Plus something along these lines can add a bit more safety if that is a concern.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=17396

 

[necromancer]

or this

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=20744

 

[Melancholy]

Thanks for the replies, wasn't expecting them this quickly!

I really like the idea of that NaOH system for dealing with the evolved AP gas, Shark!.. and it's crossed my mind, but I'm very reluctant to concentrate sulphuric acid. I'm quite (most probably overly) environmentally conscious, and from a few of my labs at uni, it'd probably be wisest, for my safety especially, not to be overconfident, or to underestimate SOx gases, especially being an amateur.

From what you've all posted, I'm thinking that simply putting the gold pins in HCl/Cl wouldn't work too well as any gold digested would simply be cemented back onto the remaining metal as quickly as it's dissolved; so the longer process of an AP bath (keeping it's acid levels topped up ofc) seems to be my best bet? Forgive me if I'm not quite on the right train of thought. :S

 

[Shark]

I admit to having problems with HCL/CL and contaminated materials. For finger foils and fine, clean powders it seems to work somewhat better. My preference is AP, and give it enough time to work. A simple, basic scrubber goes along way toward cleaning the fumes. There are several more good ideas for a scrubber in the section dealing with building you own equipment as well. Based on where I live, the amount of time it takes AP to remove base metals is faster than the time it would take for me to recover an equal amount of gold from the ground, so I see it as being fairly quick compared to digging up the back yard. Early on I thought AP was slow as well. Over time and with more use I find myself liking it more and more. It is easy to use and cleaner than most other methods. I kind of like to keep it as simple as possible, I use AP, then on to AR or HCl/Cl depending on what is available at the time, preferring AR or Poor man's AR for the first refine.