Gold loss removing solder mask?? HELP PLEASE a NEWBE

[butcher]

Gold will not dissolve in the copper chloride leach (called acid peroxide), the gold is too un-reactive, unless you oxidize the gold with the use of too much oxidizer in the copper chloride leach (such as too concentrated hydrogen peroxide solution), now the oxidized gold can form a gold chloride in solution, adding more copper to the copper chloride leach will dissolve more copper and solution will begin to change from a copper II chloride (green) to a copper I chloride solution (brown), once saturated the copper I chloride salt will begin precipitate (white powder), also if you did have any gold chloride in solution it would plate out to any copper that the copper II chloride leach was trying to dissolve (Gold would look like brown powder) or if the solution was converted to a copper I chloride (brown) the gold would precipitate as brown powder, most likely mixed with the white copper I chloride salts.

I see no need for the use of SMB in the copper chloride leach, control the amount of oxidizer used, and if you use too much just add more copper to the solution to push your gold out of solution.

Using SMB would make your copper chloride leach useless, if you do not use the SMB you can rejuvenate and reuse the solution as a leach.

Laser Steve Has an excellent document of this leach and treating the solution on his web site.

 

[golddigger2]

Hot sodium hydroxide will remove solder mask. Warm it slowly to boiling, put in your boards, boil for 5 mins, remove and wipe off the green goop. Wash well with fresh water. Job done. Wear gloves, eye protection and avoid breathing the steam

 

[dan63]

this post is to follow up on my last post and to plead for help I'm sure not having beginners luck:

I processed all my boards using the AP process and collected 15.3 grams of gold flakes. I ran a small batch of this in HCL/CL this formed the typical clear yellow solution. I then heated the auric chloride to drive off excess Cl, and let it sit over night. the next day I added SMB and precipitated the gold, after 24 hrs I had a thin layer of gold on the bottom bottom of the beaker. I siphoned off most of the liquid and am drying it... good so far!!

Everything seemed to go OK with this test batch. So I decided to proceed with the bulk of my gold fingers/traces (about 14 grams). It was a disaster. when I added then Cl to the HCl a large amount of white precipitate formed?? from the reading I've done I decided it was a copper chloride salt. I filtered it off and was left with about a gallon of Auric Chloride. I separated this into 3 smaller containers(beakers) to process it further.

This is where things went real bad!! While heating one of the beakers of Auric Chloride, the beaker broke! I was working over concrete and was able to mop it up, but I have a real mess. My first thought was to toss it, but I think it would be a very good learning experience for me to try to recover it. (once all the Cl has dissipated I plan to add water to the area of the spill and used a clean wet vac to pick what I didn't get while moping) I now have about 2.5-3 gallons of dirty water with what I HOPE is still about 5 grams of gold in it.

I've done a little more reading and here is what I think I need to do: HCl reacts with concrete and I saw some brown color form while I was moping it up... also there was a large amount of Cl liberated at the time it spilled. So some if not all the Gold came out of solution... However I DON'T think it is safe to assume that ALL the Gold precipitated out. (it is too dirty to tell by the color) so I'll test with stannous chloride but I have to assume that I picked up so much junk that it may not be an accurate test???? At this point If i'm way off base can someone please direct me. I think to proceed I have to have all the gold either in solution or as a solid, but not both. and I think it would be easier to manage the contamination if the gold was NOT in solution.... after I have all the Gold back out of solution from my reading I think the next steps would be:

1. Let the "slop" settle and siphon off as much liquid as possible. this assumes that there is no gold in solution (I'll test with stannous-chloride) If gold colloids have formed I'm at a loss.... Please help!! (I just read the thread "Tin in AP" and that was helpful with dealing with gold colloids)
2. I have to assume that I have every kind of contamination possible. I know there is a bit of sand/small rocks, dirt, bits of organic material + metal filings of different types etc. once I have all the liquid removed from the solids I thought to incinerate/roast using a torch (I have a propane torch) to oxidize any additional base metal and burn off any organic material I picked up.
3. next I think I need to wash/boil with HCl (and maybe a bit of sulphuric acid?) after boiling with acid. I should also add water to the solids and boil. this should remove the base metals
4. after removing base metals is it OK to mix the entire mass of solids with HCl+Cl and filter out all the solids? or when the HCl reacted with the concrete did I pick up minerals that I also need to deal with???? I'm sure I now have some CaCl in solution. I found the following reaction of HCl and Concrete. 2 HCl + Ca(OH)2 -> CaCl2 + 2 H2O. this would neutralize the acid when it spilled and the gold would precipitate right??? but are there other contaminants I'm not considering????


I'll keep reading and between that and any experience others may have had I hope to recover the majority of this Gold... but more importantly it will prove to be a very valuable lesson/learning experience. The beaker was new and I was using a small backpacking stove but clearly It heated unevenly as the bottom popped out. I've never seen this happen before???? and did not think it possible???? next time I'll heat more slowly.

OK If I'm way out of line and I missed reading something that deals with this already I'm sorry. I'm truly doing my best to learn and not use people as a crutch. thanks everyone for your help so far!

 

[Harold_V]

To begin with, you you're heating beakers with direct contact with flame, you got what you should expect. They don't tolerate that well. You should have an isolating pad between the two. I used to use asbestos, which is now pretty hard to find. There are other substances, but get something before you try heating again.

The solutions.

Allow the fluids to settle well. Assuming they test positive for gold, siphon them off, and precipitate what ever gold is contained within. Properly discard the solution after testing, to ensure you have recovered all of the values.

You now have solids remaining. Get them all in a filter. Don't be concerned about what is contained within. The resulting filtrate is likely to contain traces of gold in solution. Precipitate and wash properly, and discard the solution, as you did with the large volume. Be certain to test the solutions with stannous chloride, known to work.

You now should incinerate the solids. Filter paper and all. Incinerate until there is no carbon remaining. Screen, to remove large objects, none of which should be gold. You would then subject the resulting solids to a hard boil in HCl. Add water, allow to settle, then siphon off the solution, leaving behind ALL of the solids, even fine particles. Rinse well, allow to settle, and siphon once again.

If the rinse was free of color, proceed to dissolve the values. You have now eliminated the large volume of solution and have concentrated the bulk of your values. Examine the concrete. If it was subjected to light, it will likely turn purple. That represents gold lost. It may or may not be much.

You have leaned a valuable lesson. Do not heat lab ware directly, with the exceptions of, perhaps, test tubes. Beakers do not enjoy the uneven, rapid heating, although they will tolerate heat well if it is applied slowly and uniformly.

Harold

 

[yar]

Harold you mentioned using an isolating pad like asbestos between the lab glass and heat source so as not to cause the glass to break or shatter. I have pieces of tempered glass from microwaves that I was thinking of using for this purpose on my hot plate. Do you think that would work ?



Edited to use proper terminology

 

[kkmonte]

I'm surprised no one has responded with the "Put everything away and read more, read hoke, etc. etc. etc.".

Dan63, not trying to be offensive, however it doesn't seem that you accept any answers you are given. You ask your questions looking for an answer and when someone (from page 1) posts a response, you dismiss it by saying "Nope, I know it's not that!", or something similar. Have you read all of Hokes book? Have you performed the getting acquainted exercises? Seems to me if you keep going the way you are going, you are only going to hurt yourself or possibly someone else.

 

[FrugalRefiner]

Uh, guys, This is an old thread.

Yar, I wouldn't advise using that piece of glass on your hotplate. Find yourself a Corningware Pyroceram dish.

kkmonte, Dan63 hasn't been on the forum since Sept 13, 2012.

Dave

 

[kkmonte]

ARG ! I didn't even look at the dates! LOL, i just saw it at the top of the new posts.. haha It's all Yar's fault!

 

[yar]

Yes it was an old thread which is what us newbies should be reading through, just wanted to see if my idea would be feasible. I figured if tempered glass can withstand breaking in a microwave it could be used on a hotplate. Thank you for the response Frugal...now back to the books for me.