Help Needed: Pins in Acid Peroxide

[Hawas]

Hello everyone,
If you have read my first topic, you would know that I am trying to experiment with the various processes for claiming values out of escrap.
My first experiment was to treat header pins with nitric, then HCL/CL. Despite the great help from you, it failed completely. I was very clumsy, didn't have proper equipment, and made a lot of mistakes. I don't even know what exactly went wrong.
Second experiment was to claim gold from flatpacks. Incineration was a disaster, I guess heat was not enough so I got a mega smoke, but then it went well and recovered my first gram of beautiful light brown powder

This is the third.
I had around 900g of connector pins (PCI, AGP, processor slots, trimmed vga/serial connector pins) and used the AP method. So far I liked it better than the nitric, although it seems to cost more as nitric and hcl have same price where I live. Pins were mostly removed using hot air gun.
2 Notes about the solution:
* I put two complete boards into it as an experiment, they had (almost) everything removed except for the slot pins, removed plastics. They got stripped as expected.
* I put the processor slots with their plastic as I couldn't find a way to remove the pins from the housing. These was the thin black kind and didn't seem to be affected by the solution.

The starter CuCl2 solution was prepared aside using some thin copper wire from transformer, and used air pump. Only added very little peroxide into the batch near the end when it seemed to stop completely.

After it finished, it looked dark green and dirty/cloudy and didn't seem to settle after long time, and was very hard to filter. Now I know that I should have added HCl and shouldn't introduce water, good for next time. However I managed and got around 3L of clean CuCl2 that I evaporated and stored for later, 1/2L of AP that contain a small amount of powder (that will go directly into next patch), and my values with very little solution.

This solids contains:
* Small golden particles.
* Black/dark grey powder.
* White/very light grey powder that settles extremely fast, even while swirling it doesn't go up.
* Small plastic debris and a couple of very small ics (i.e. 2x3 mm).

I washed with cold HCl twice, clear improvement. Gold particles are much more visible and it settles very much faster and filtration is easy. Still have all 4 kinds of precipitate.

Now I added some HCl and boiled, and that was not a so bright idea. It foamed (removed from heat before spilling) and formed a black foam that sticked to the beaker walls. I let it cool and found light brown crystals (I assume they are CuCl), solution is light brown also, and solid settled to bottom. I knocked as much as I can form the beaker walls with spray water, and added some HCl.
It looks like it was before the boil, the white powder may have darkened a bit but I'm not sure.

I left it to settle and wrote this post. I don't know how to proceed now.
1) Do I boil in NaOH?
2) Do I just wash a couple more time with cold HCl then proceed to HCl/Cl?
3) Something else?
I appreciate your help.

PS. Sorry for all those details, it's just that I read and learned a lot from the forum that I feel the desire to share what I've done. Kinda like a student that reports his progress.

Thanks
Hawas

 

[solar_plasma]

1) no, this would only form a lot of undesired insoluble voluminous hydroxides and more, which clog the filters and it makes no sense at all
2) if it is CuCl (I guess it is), it will dissolve in HCl at room temperature / if there should be PbCl2 (if you had too much solder in it), it will dissolve in hot water washes

so, putting HCl into the filter, letting it run through, then several portions of boiling water should solve the problem, then there are only gold foils and dark powder (gold) left in the filter

 

[butcher]

Tin from solder can cause problems as the tin in this solution can be in several states of oxidation stannous and stannic chloride, this was most likely the problem with filtering.

If the solution is concentrated brown the copper II chloride is forming copper I chloride which when saturated will precipitate out of solution in a concentrated solution this can be brownish powders more dilute white powders.

Lead from solder will also precipitate as a white lead chloride powder.

If silver was involved the silver can form an insoluble silver chloride that may be present, also a white powder.

A saturate solution of copper II chloride / copper I chloride (dark brown) if diluted with water will precipitate much of the copper I chloride powders.

Diluting acid content or changing PH more basic the tin as stannous wants to form more stannic, or even the more troublesome tin hydroxides the more basic the solution gets (almost like gunk in solution).this form of tin hydroxides does not filter as well, or has more trouble settling (sometimes acidifying can help making filtering more easier, or help more tin dissolve).

Solder or tin is kept out of solutions as much as possible because of the trouble it causes, this is one of the major reason working with whole boards in acids really does not work, without a lot of headaches.


Iron or base metals lower than copper in solution will push copper out of solution as the base metal higher in the reactivity series goes into solution, with iron we can end up with a copper chloride/iron chloride solution, or just iron chloride as iron pushes out the rest of the copper from solution.

Metals higher in the reactivity series than hydrogen gas off your acid as hydrogen gas, some of the more as the metals form chloride salts or some very reactive metals like aluminum can even form hydroxides in solution as it depletes the solution of hydrogen, aluminum will also cause trouble filtering as it forms a goopy chloride or hydroxide.


So you have some insoluble white powders with gold flakes, what to do?
Well my answer, to this problem would depend much on what I had to deal with.
There can be other methods to deal with the problem


Lets assume we just have mostly copper I chloride, lead chloride, and some trash, in this case, we can add some HCl to dissolve the copper I chloride as copper II chloride, letting the lighter green solution sit until all of the insoluble powders settle, in this case lead chloride, gold flakes and our trash, we can now decant the solution from the powders, Now we can add water to the white powders and bring to a boil, lower heat to keep solution warm, but not boiling or moving, giving plenty of time to let insolubles settle well, lead chloride is very insoluble in cold water(white powders), but becomes fairly soluble in boiling hot water (clear solution), now decant the lead chloride to a cooling jar, as this solution cools you will see the lead chloride salt forming again as white powders or many times as needle like crystals (this may have something to do with how the lead chloride cools.

Now your left with gold foils and trash, personally I would make a dilute sodium hydroxide (NaOH) solution to wash the gold foils, my purpose here is to convert any remaining chlorides to water soluble NaCl salts, this wash with a little heat, again let gold and trash settle, before decanting, then a couple of water washes to remove traces of salts.
The reason for this is in preparation for the next step of incineration, gold and any metal chloride when heated to the temperature we use in incineration can vapor off some of the gold, removing the chloride can help us from losing some gold to the smoke.

Now incinerate the gold foils to burn off trash, let it cool down, add HCl and just a little water bring the heat up to almost a boil, let powders settle well and decant this wash, another hot water wash, decanted hot, if solutions are colored repeat them, now these recovered gold powders should be ready for the first refining.

The whole process described can be done in a corning ware dish on a hot plate, even the dissolving of the gold powders, leaving powders in the dish and removing solutions as needed.

 

[Hawas]

Thanks solar_plasma and butcher for you elaborate reply.
I followed butcher's advice to the letter, here is how it went.
1) Wash with HCl to remove CuCl, no problems, did it twice.
2) Boil in water to dissolve lead chloride and decant hot, this was hard, even with my hot plate on 1, solution was moving and didn't settle. I had the flask that I decant into (through filter) on the hot plate also but the lead chloride still precipitated in the filter and clogged it. Had to remove the filter and decant. Got a lot of lead chloride crystals, needle like, as expected. I don't see traces of any dark powders in the flask after 2 days, only crystals.
3) I incinerated by moving the stuff into a s-steal plate, I couldn't keep it in same vessel as advised because I was working in a beaker. I put the plate on a boiling water bath to dry it, then on a high heat plate and used a torch for around 10 min. Found out that I have a lot of trash that was not very visible. Good amount of smoke, then all trash was burned, even the small ics. Trash kept their original shape but all turned white, and it was easily crushed into white powder. Ics contained thin wafers.
4) I boiled in HCl + some water and left to settle.

That's where I am now, the solution seems dark yellow, and a little greenish. I will repeat the HCl wash and then hot water wash.
The solids are far less than before, lighter in color and contains some coarse particles that I think are trash.

After the wash I will proceed to dissolve the gold, and keep you posted.

Hawas

 

[Hawas]

Ok then,
I dissolved the gold, precipitated using smb, washed (3 boiling water, 3 boiling HCl, 3 boiling water).
Two things seemed odd:
1- I got only 0.1g gold, now I was processing rather newer boards, but still it was 900g+ of pins, some of them were very close cut from vga/serial connector. I expected 0.5-1g from that batch.
2- The gold was much darker brown than my first gold, which came from flatpacks, I repeated the dissolving and washing and still same color. The first gold powder was dissolved and precipitated only once.

Now on the whole, I processed 50 newer motherboards, and got 1.1g from them. 1g from flatpacks, 0.1g from slot pins, and 0 from header pins (I messed that up). I still have the ICs, but those are some 120g I don't expect much from them.
I understand I am bound to mess up in my first trial run, but I want to know if that's on the normal side of the scale. Considering that these boards sell for some $1.50, I seem way off.
What do you think?

Thanks
Hawas

 

[pgms4me]

Just my 2 cents worth. remember,a good percentage of the value in newer boards is the other metals. silver,Tin and copper especially. I believe that those newer boards would still be worth as much as 70-80 cents per pound with no gold in them.