Mixed fiber CPUs in AP

[cejohnsonsr]

Disclaimer: My computer died, so I don't have access to my copy of Hoke & only limited access to the computer I'm using right now. Otherwise I could probably do a better job of looking some of this up for myself. I promise, as soon as I can afford a new hard drive I'll get my computer up & restored. Until then.....

I had a mixed bunch of very low yield fiber CPUs that I wasn't sure what to do with. I read another thread, which I can't find now (of course), where (I think) lazersteve said he just puts them in AP & lets them soak a long time. That's what I did. The AP had already been used on 2 batches of unpopulated board material. After about 2 or 3 weeks of soaking with a swish whenever I walked by (no bubbler) I decided to see what I had.

The 1st pic shows the CPUs after a light rinse to remove gold flakes & foils. I was surprised to see that AP will digest/dissolve steel & copper. The heatsinks were partially consumed & most of them came off easily, though some were still firmly attached & required a screwdriver for removal. The ones that required a screwdriver can be seen at the top of the pic. I can see what I think is gold that didn't either dissolve or come free.

The 2nd shows the AP filter after rinsing & drying. The AP had become VERY black & had a lot of sediment in it. You can see some gold lying in a bunch of grey mud. I'm not sure what this grey stuff is. Anyone care to hazard a guess or ever seen it before? I also noticed that the filter turned green again after drying even though I rinsed it thoroughly with my spray bottle.

The 3rd pic shows my mash after a 2nd VERY thorough rinse. I can see plenty of gold, but I can also see about as much copper. The sediment varies from brown to a rusty red color. I'm guessing the rust would be from the iron/steel content of the heat spreaders & the kovar in the pins. I'm not sure about the brown, but under magnification I can see very tiny specs of gold that aren't visible to the naked eye.

The 4th pic shows the rinse water from the mash in the 3rd pic. It's very rusty looking & has some more sediment that made it through the filter.

I haven't done any further processing yet. I also haven't tested either the AP or the rinse water for gold content, but I will before the end of the day. I'm making a fresh batch of stannous & a small amount of known gold bearing solution to test it with before I proceed. (Been meaning to do that for a while.)

So, my thought is that maybe I could proceed as I normally would & dissolve the mash in HCl/Cl. What I'm not sure of is the solubility of the other metals in the mash. I'm also not sure how I should go about getting the gold out of that grey stuff. I don't have enough Nitric Acid on hand to dissolve the base metals 1st. What little I do have is already dedicated to another batch of ceramic chips that are in progress. Also I think I'd have to incinerate before going from AP to Nitric & I'm not prepared to do that yet. If it turns out I am able to dissolve in HCl/Cl, I think I'll carefully lower the filter into a beaker so that all the trapped gold specs get dissolved too, then slowly, carefully raise it so that the AuCl gets filtered. Then I guess I'll have to rinse the filter too. No problem. That part I can figure out on my own (though I am open to suggestions if anyone has a favorite technique for that kind of thing).

As always, I appreciate any input. And thanks for all the help I've received along the way.

Ed

 

[butcher]

. I say do not skip the important steps, incinerate the powders.

It can be done easily, I normally do this and the rest of the process in a corning casserole dish on a hot plate, using the propane torch to bring the powders to a glowing red hot, while keeping powders crushed and stirred to get good exposure to air, let cool.

You can also do it in a small stainless steel pan using the torch.

This important step will help, as you will have solder, the tin and lead involved, as well as organics and oils, that will give you trouble later if not removed.

After incineration, cool and bring to a boil in HCl, lower the heat, but keep as hot as possible to allow fine powder plenty of time to settle, taking up solution with a little water, after powders settle well, the water rinses should be as hot as possible also decanting only after gold settles.

The HCl after incineration will help to remove tin and other base metals, the hot water rinses will help to remove lead chloride, if there is any copper metal left after this, (usually is indicated by the strong color of HCl solution) you could dissolve remaining copper in the copper chloride leach (acid peroxide).

 

[cejohnsonsr]

Hello again, butcher. I'm going to be out of town for a few days so I won't see any response until Mon or Tue. I don't have a Corningware Pyroceram dish (yet) but I do have a stainless steel frying pan. My hotplate isn't really equal to the task of incineration but I have a Coleman camp stove that I know will heat the pan up hot enough. I also have a regular small propane torch & a MAPP torch. I want to make sure we're on the same page. At this point, I don't have powders. I have foils, flakes & specks of gold mixed in with all the other stuff (lead, tin, steel, iron, copper, grease, trash....). Still, incineration should remove anything that's NOT METAL. Is that correct?

When I do the HCl boil, some (most?) of the base metals should dissolve into solution & gold will settle to the bottom? I can use the camp stove to keep hot water on hand for the rinses. Would it do any good to add a drop or 2 of Sulphuric Acid at this point to help get rid of tin & lead?

I'll check back here when I'm able. Looking forward to seeing how this works out.

Happy Easter,

Ed

 

[butcher]

I have foils, flakes & specks of gold mixed in with all the other stuff (lead, tin, steel, iron, copper, grease, trash....). Still, incineration should remove anything that's NOT METAL. Is that correct?

Correct, some very reactive metals may go up in smoke as oxides, but as long as these powders are free of chlorides no gold or silver would go up in smoke, Heating from below can help to keep from blowing powers out of the dish, (I normally heat from below and above with careful use of the torch).

If the powders are base metal or silver chloride salts or contain salts of chlorides (from previous use of HCl) I will give them a rinse in a NaOH solution, this can help to convert base metal chlorides to hydroxides making sodium chloride solution (salt water) which can be rinsed out with plenty of water, rinsing out the chlorides will help to keep silver and gold powders from being volatile, (chlorides at these red hot temperatures will form chlorine gas that could make the gold or silver volatile).

When you do the boil in HCl it will dissolve many of the base metals, note it will dissolve copper oxides but will not dissolve elemental copper metal, it will also dissolve the troublesome tin (oxide) as a chloride (stannous in solution), it will not dissolve gold, or silver, silver and lead form insoluble chlorides with your gold, which can be removed later, lead chloride is soluble in boiling hot water silver chloride is not, silver and gold can be separated at later stages.

 

[FrugalRefiner]

Still, incineration should remove anything that's NOT METAL. Is that correct?

Anything organic, yes. Not necessarily anything that's not metal. Ceramics, silica, etc. are not metals but they are not eliminated.

They're not usually a problem, but when you dissolve your values you could find undissolved bits of non-metallic material remaining. That's why you filter your solution before precipitating your values.

Dave

 

[cejohnsonsr]

Finally got a chance to try incineration for the 1st time yesterday. I learned a few things. My pan is too shallow. After heating from below, I used my torch to heat from above as well. I got it to glow red but a little bit went over the side at 1st. Also, a breeze came up & a little more was lost. Probably (hopefully) mostly just ash. What's left doesn't look like gold at all any more. Mostly black ash in the shape of the pins & the rest very fine powder. A little bit of grey too. The weather is getting better, but health & finances aren't allowing me to do as much as I'd like lately. Or as often. I'm hoping to be able to finish processing per butcher's instructions this weekend. I'll post an update when I'm able.

Thanks,

Ed

 

[cejohnsonsr]

Just thought I'd post an update.

I incinerated the filter with the gold, copper, rust, etc... When it was all done I boiled in HCl & rinsed with hot water. Then I boiled in HCl again (this time no discoloration) & rinsed in much hotter water. That removed almost everything except some grey mud & non organic trash. After I dissolved in HCl/Cl (with a little heat) I filtered the AuCl as usual. It's looking pretty good. Nice golden color. There really isn't that much gold, but I didn't expect much from these CPUs. I'm evaporating the excess Cl & water now. I'll drop with SMB later this evening & post my results after the powder is washed, rinsed & dried.

Thanks again for the help & advice, butcher & FrugalRefiner. This has been a good experience for me. Maybe the last I get to do for a little while. I'm about out of chemicals & really short on cash. I suppose I could try to depopulate some boards & try incinerating flat packs. That would keep me busy while I wait until Uncle Sam pays me what I'm owed.

Ed

 

[FrugalRefiner]

Ed,

Let me add 2 more fine points to your process. They're not necessary every time, but it helps to know why they're used when they're used.

First, once you have your gold in solution, it's a good idea to chill and dilute you solution before you filter it. The reason is that a small amount of silver can exist in a strong, hot solution of AR. By diluting and cooling your solution, you can force silver out of solution as silver chloride. By doing this before filtering, you can prevent this tiny bit of silver from reporting in your precipitated gold. Unless you've diluted your solution by more than a few times its original volume, there's no need to evaporate prior to precipitation. Gold will drop from a dilute solution. PGMs, on the other hand, need to be concentrated prior to precipitation.

Second is to add a small amount of sulfuric acid to your solution, again before filtering. If any lead has made its way this far, it will be precipitated out of solution as lead sulfate. It doesn't take much H₂SO₄. A few drops to a few milliliters depending on the volume of solution.

Doing both of these steps before you filter will give you a cleaner precipitation of your gold.

Dave

 

[cejohnsonsr]

Thank you, Dave. I'll remember that. Itried to drop last night while it was still warm & did have some problems. I wound up with about .38 g which was not very clean. I think I probably had silver in the powder. I'm pretty sure there's quite a bit (relatively speaking) in the original material. I'll probably try to rework that again at some point, but for now it's not enough to bother with & I have some other material I need to try to finish up. I have a thread for that batch at http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=17545 if anyone feels like offering a little more advice.

Thanks,

Ed