Gold Recovery from PINS, How to do it?

[NobleMetalsRecovery]

I would like very much to know the current thinking, a consensus of sorts, regarding How to Recover gold from plated pins. I'm very familiar with the most common methods. I just wonder who is having good results, and with which method. I'm willing to consider most any method other than cyanide. Thanks in advance. Steve

 

[lazersteve]

Steve,

As most of us know pins are a very unique case as the variety of pins, base metal composition, and plating characteristics all affect the recovery approach.

Here's my take on the pins:

1) Plastic headers containing partially plated pins: AP.

The AP strips the foils relatively quickly due to the spacing between the individual pins in the header. The partial plating allows the foil to float free once the undercoat is dissolved. The large plastic headers are easily rinsed free of foils and removed.

2) Large fully plated milspec items classified as pins: Cell.

The large milspec pins have a thick coating which AP takes a long time to strip. The cell does a very through job and goes pretty quickly for large plated items.

3) Bulk fully plated copper based pins: FeCl3.

When the base metal is known to be copper ferric chloride does a very good job at speedily stripping the pins.

4) Other fully or partially plated pins: Dilute Nitric Acid or HCl Crock pot.

The wide variety of pins that fall into this category are notoriously the most difficult to quickly strip. For this reason nitric is usually the proper choice. When the pins are partially plated the speed of nitric can't be beat. If nitric is not accessible, the HCl crock pot method is slower, but still effective.

5) Pins containing other metal collars and pieces: Remove the collars and other metals first with an acid that selectively attacks the collar metal. Process the pins as above after the additional metals pieces are chemically removed.

The additional metal pieces can interfere with many of the acid stripping methods and need to be removed before acid processing.

6) Milspec connectors and fittings with multiple parts: Disassemble the connector and process the pieces with the cell or other method as appropriate.

Any milspec connectors with multiple pieces typically contain plastics, wires, odd metals, and more importantly are plated on all the interior surfaces. Failing to fully disassemble these items before processing will result in reduced yields due to the lack of exposure of the plated surfaces to the acid. If a gold plated surface is shielded from the acid it will not be stripped.

This list is by no means applicable to all situations but should serve as a rough guide.

The best method for each type of pin should be determined experimentally by processing a very small batch with the selected method to indentify any shortcoming and pitfalls of the method. For example, some pins contain large amounts of silver which will interfere with several of the methods.

I always perform several small scale tests on my scrap pins before I commit to large scale processing with any particular method.

Steve

 

[NobleMetalsRecovery]

Thanks, that helps. I'll do some small scale testing before committing to the whole batch. I have yet to get a yield on pins from wire wrap boards, even though I've tried as much as a pound of pins at a time. If I dissolve them in AR and the gold will not drop. I've been selling these boards rather than continue to yield nothing, wasting time and chemicals.

 

[P_CARROLL]

The fully plated mil spec pins are easily stripped in HCl. i use a 2 litre erlenmeyer flask and strip one pound a time. Takes two baths though to completly dissolve the base metals. then the plating is left and I filter it off for refining in an ar solution. Yeild is about 3grams of pure gold for every pound of pins. The larger ones are stripped in the reverse plating cell as it would be a waste of time to try and dissolve them in an acid bath.

 

[Anonymous]

I have tried the plastic header and/or connector with plated pins in AP and usually end up with a gooey plastic residue that the gold flake sticks in and will not rinse out of.
Tried dissolving the plastic goo in acetone and that didn't work.
Just stayed gooey.
I now make sure there are no stickers on anything, that helped some.
Any tricks?
I have tried AP on computer ISA slots.
Its seems like there is not much gold there to justify the expense of the chemicals.
Some are plated at the contact point only, not full length.
Ideal-Wirenut

 

[lazersteve]

Wirenut,

Different plastics react differently to AP, this is why preliminary small scale testing is important. I've processed many pounds of header pins (partially plated new old stock ribbon cable headers, 3% H2O2, 31.45% HCl, with no heat, 12 hours reaction time) with the plastic intact and had no gooey mess formed.

What reaction conditions are you using (reaction time, heat, peroxide concentration, muriatic concentration, etc.) ? What is the source of your header pins (motherboards, hard drives, new old stock ) ?

Steve

 

[Anonymous]

Steve,

This last batch was a mix of items that were all cut from mainboards using a small air chisel.
(Nice but messy-have to sweep up a lot of parts!)
The mix included ISA slots(black plastic)
Long edge card connectors from some kind of video editing system (blue plastic)
Small D-shell sockets (black plastic)
Header pins in a right angle configuration(blue plastic)
(I usually pull pins and process in my cell but these will not pull, they just break off.)

1 quart 3% peroxide for medical use.
1 gallon 32% Muriatic Acid for concrete cleaning.
No heat applied. (Aprox. 80F ambient temperature)
Bubbled with air from compressed air source for two days and there were still base metals sticking out of some of the plastic with gold flakes floating around.
Gave up and rinsed off the connectors and I think all the gold was removed.
(Some of the connectors have small holes that I can't see into easily.)

Possible mistakes are;
Chemical mixture ratio.
Excess process time.
Not sure about the air source thing yet. (Different post)
Mixed lot of materials.
(Need to check the plastic & see if there are any markings as to what kind of materials these are made of and process similar items together)

I need to step back & rethink my process.
I do like using the cell better.

Clint

 

[Absolutsecurity]

A few days ago I put about 8 to 10 pounds of various pins in a 5 gallon bucket and poured HCL over them and just let them sit and soak , aggitate them every day once or twice and about 50% of them have dissolved and I have a good amount of plate foil showing when I aggitate. I figure I will just leave them to themselves and aggitate every once in a while - I can work on other projects while the pins are dissolving the base metals out of them and in a week or two I should have some foil to filter out and refine.

I know that there isn't alot of gold on them so the sit and let them soak deal is ok with me - might not be ok if that is all you have to work on at the moment but I saved them up for a few years and totally removed all the header plastic when I got them so they are just plain pins no other plastic or debris.

What does anyone else think of this method?

I remembered reading something similar when I first started reading post on this forum so thats why I decided to go this route.

Glynn

 

[Baja Bob]

I'm pretty new at refining scrap gold, but I have been around leaching of gold ores for awhile. I know that oxygen has to be added to cyanide leaches and that its particularly important to keep excess oxygen out of chlorine based leaches. I am thinking of bottle rolling the chlorine leach and putting a bunch of pins along with it, as soon as I can find some pins. Baja Bob

 

[eagle2]

Glynn
That`s a good simple method, if your not in a hurry. Stirring adds a little oxygen, so some Copper eventually gets dissolved. This starts the Cupric leach going, which keeps on dissolving more base copper.

But you need to add about 50% water to the HCl (always add the acid to water first!), because water holds more base metals in solution than an equal volume of concd. HCl. The lower concentration of HCl will not slow down the leach. Also you will get a lot less fuming.

You can speed up the leach by adding some peroxide (H2O2), and some heat.

When the solution gets very dark the leach will stop (Too many Cuprous ions). You can convert some of the Cuprous to Cupric by adding more H2O2, or air the solution with a continuous fish bubbler. Eventually you will have to remove the used up solution and put a fresh solution in the bucket. With 10lbs of pins I would guess you need 3-4 gallons to get rid of all the base metals.

You should study LazerSteves tutorial on the AP process.

Al

 

[Palladium]

8)

 

[nickton]

What happens when you distill out the copper in solution? Can you reuse that acid?

 

[Yggdrasil]

What happens when you distill out the copper in solution? Can you reuse that acid?

I do not know what you think here?
Are you suggesting evaporating the Copper?
There will at that time be no more acids left.