Question /about AP

[MarkB]

I took my boards and depopulated them. Soaked them in HCl til tin/nickel removed. Put them in a plastic tub. I added Muriatic Acid and maybe 3-5 oz of hydrogen peroxide, then filled the rest of the way with water (not distilled)(hope that wasnt a fatal error in this process) until the pieces of board were covered. I placed an air hose in the solution, and placed the bucket inside a larger bucket, and on top of a metal garbage can lid.

The reason for the large quantity of water was to keep the process going when my air hose cut off. It routinely does after a few hours, and then I need to let it cool and start again. Anyways, on about the 5th day, the solution turned from a perfect light green color into a 'dark green', but more accurately described as very dark brown/almost black solution. I am assuming theoxygen from the water I put in initially is depleted, and the air hose off all night caused the process to stop.

My question is, Do I need to decant and whip up a new batch of AP, or can I add an ounce of peroxide to 'restart' the process, a little more water, and get a second air hose to rotate in when the first one stops?

Is my solution eating my gold?

If I don't see a definitive answer shortly, I plan on decanting & filtering the ap solution, then storing and labeling it. I am going to rinse off the board pieces and collect all loose gold. The board pieces will go in a bag until later, especially if I can visually see the gold. If there is a large enough amount of gold in the original, I will proceed with that in AR and return to the remainder of the project later.

The reason for the detailed explanation is so people don't assume I just came here and posted a topic without reading. I have been reading here for over a year, and have fully recovered and refined gold by myself on several occasions using several different processes. I feel I have a decent understanding of the science, but there are still a few holes to fill in the gaps.

thank you for your time.

 

[butcher]

MarkB,
I would gain a better understanding of the process, how it works, what makes it work, what problems involved in dealing with the cupric chloride leach, and how to rejuvenate and reuse it to dissolve copper and other base metals leaving gold untouched...

You can rejuvenate the solution you have now and continue the process.

Note if you do get heavy-handed on the oxidizer you will put gold into solution.

Whole boards have places that metal ions like gold can plate out onto that then you and your leach cannot reach, many circuit boards have embedded copper traces...

The blue is copper in a dilute solution, the green is your cupric chloride CuCl2 as it dissolves copper or other base metals into the solution it becomes the dark green (dark green to brown to blackish looking) cuprous chloride CuCl if concentrated or overly saturated the CuCl will precipitate out as a white salt of copper.

Adding a bit of HCl and air (or a splash of 3% H2O2) will change the brown CuCl back into CuCl2.

Gold will not dissolve to any extent with this leach as long as you do not get overly generous with hydrogen peroxide or other oxidizers, using only 3% H2O2 in a small dose, to begin with, and then using air to complete the process, you will not put gold into the solution to much of any extent.

Too much oxidizer and doing this with whole circuit boards, it would not surprise me to lose most. if not all of the gold.

Again keep studying so you gain a better understanding, but then you also need have to practice and experience of working, well now that you have practiced and things do not always work the way thought, and you see you miss something in the understanding, then go back and study, now that you have practiced and gained some experience, you will gain more understanding of what you read or studied the first time, and studying more after gaining hands-on experience you will fill the gaps, after a time of doing this the wholes in our understanding get smaller and smaller, and our skills grow.

 

[MarkB]

butcher: thank you for the very detailed reply. After I posted, I thought "maybe its very simple, and I just need to add more muriatic acid," but usually the easy fix is the wrong one, at least in my personal experience so far. I am very aware of the solution eating the gold, and I assume I will lose some to the solution. I absolutely intend to save all the solution and go through every step thoroughly. I feel I've made enough mistakes that I shouldn't be making anymore by now. I've been reading and researching for about a year off and on. Have tried a few different processes. Dropped 1.3 grams from some k6 ceramics (.03 per i believe was accepted ratio) after processing in concentrated sulfuric and poor man's nitric. Tested with 22k solution, it's above. Got a few other projects all the way to the point of denoxed AR, just never tried to drop yet. I need to get stannous chloride before I go any further so I can decide what to do with the 'waste', and if it is waste."

Anyways, before I ramble too much, if anyone on this site has some good source material heavily focused on the science, I would love to have an opportunity to read it.

Thanks again butcher, the response was better than anything i expected

 

[MarkB]

a side thought: When you say you assume I will lose most of the gold, if not all, you just mean to the extent that I can force it out if I saturate the solution with copper? Or it's a more fatal error?

 

[Yggdrasil]

If the gold has been dissolved, due to accidental or intentional adding too much oxidizer, it will plate out as Butcher said.
And then the gold won't be in solution anymore, since it has cemented out inside the tracings of copper inside the PCBs and any and all accessible surface of less noble metal.

It is still there, if you would be able to dissolve all the copper (less noble metals) completely and the add AR HCl/Cl-H₂O₂.

If not, there will be gold hiding inside all kinds crevices, given that it has been dissolved in the first place.

 

[MarkB]

your prompt response appreciated! Glad to hear that. As i sort of mentioned earlier, I have a tendency to fear the worst possible outcome no matter how slight an error I made. I'm still reading through Butcher's response. I figure he provided that much content, I need to make sure I comprehend everything.

 

[Yggdrasil]

No worry.
As long as you haven't thrown away anything, you still have what was there.
It may be harder or even impractical to get hold of, but it is still there

 

[MarkB]

So, this hit me...and I am guessing it is an exercise in futility, but this is my thought:

Why not just intentionally add too much oxidizer? That way, you know all your gold is going into solution. Let the AP sit while it eats all the gold, copper, and other pm's. Before your solution is completely saturated*, pull out all board, pin remnants, etc. that are now deplated. Rinse them off and set them aside for further examination at a later time. If done correctly, you should see no gold on any of the matter you removed. Filter the fluid to ensure all small bits of debris removed. Any copper/gold in filter needs to go back in AP for digestion or placed to the side for further recovery/refining. Once all debris is removed and all metal particles are dissolved, place copper in the solution to finish saturating the solution and force out the gold.

A few questions arose.

before your solution is completely saturated* : Use a healthy amount of HCl per material to prevent premature saturation. I believe I heard 1 gallon muriatic acid 32% per 2 pounds of basemetals.

When intentionally saturating the solution by placing copper in the bucket, will the process stop once it forces out all metals below it on the reactivity chart (tungsten, mercury, silver, gold, platinum); or will it continue to displace copper to make room for the new copper? My brain tells me there is nothing to displace when trying to get a solution fully saturated with copper to digest more copper, so the reaction will cease, but I am not positive. If it doesn't cease, then you'll start getting copper mixed in with your gold that has been cemented out, and this is futile.

Anyways, my thought was you can use your recovery process to also do a large portion of the refining. Ultimately, your gold will be mixed with whatever platinum was there so further refining is still necessary, but I thought this may save a few irritating steps, I.E. rinsing gold flakes off every single piece of material placed inside (i know alot of you place in a container and shake).

I ADVISE NO ONE TO ATTEMPT THIS AS THESE ARE JUST MY THOUGHTS AND I CANNOT GUARANTEE YOUR SAFETY OR YOUR GOLD'S AT THIS POINT. However, I would love to hear the in's and out's from more experienced refiners

 

[Yggdrasil]

The challenge is that the moment gold is dissolved it will cement/plate ot on any exposed surface of basemetal.
Visible or deep inside the PCB no matter where it is.
It will inevitable "steal" some of your gold, how much is dependent of the area of the basemetal available to it.
So in the end you will have moved some/all of your gold to inside the PCB where it is much harder to get to.

 

[MarkB]

The challenge is that the moment gold is dissolved it will cement/plate ot on any exposed surface of basemetal.
Visible or deep inside the PCB no matter where it is.
It will inevitable "steal" some of your gold, how much is dependent of the area of the basemetal available to it.
So in the end you will have moved some/all of your gold to inside the PCB where it is much harder to get to.

ok, makes perfect sense. So in this situation (i know I said 'boards', but it was about 2 kilos of PCB, 400 g or so of depopulated ram sticks and other trimmed portions of boards with gold surface plating. I didn't take a whole board, cut it into strips and put it in AP. I understand your point is still valid) so let's pretend we apply what I said to a batch of pins, or some other source material without nooks and crannies. Still no real benefit derived?

As a side note, I took about 5 little strips out, 66% of the gold is removed after almost two weeks. I momentarily set them in a stainless strainer, and when I put lifted the pieces out to put them back in the AP bucket, the little liquid that gathered up in a small dime sized puddle was loaded with gold flakes. That's where I stand. I am guessing my solution is saturated but not positive. I am going to go ahead with decanting so I can visually see where I am at. I intend to sort out the boards and restart the process. If a stannous test shows positive for gold, I gather i shouldn't separate anything out, as there is no telling if gold cemented out and is hiding in an inconspicuous location.

p.s. anyone know a good source of pure tin scrappers come into contact with on a normal basis that can be used to make a stannous test?

 

[Yggdrasil]

The solution will not show gold unless it is dissolved.
If you have put gold into solution and it has cemented out, it is in metallic form and stannous will not react.
Second if you dissolve pins, other all metal objects or surface only plating without other base metals
one can easy dissolve all metals and then it won't create problems with dissolving the gold alongside it.
Foils is what we like as a result from AP here :wink:
It is wise to shake it vigorously from time to time to loosen the foils.

As long as you bubble air through the solution you will basically have an everlasting process going.
If it gets saturated with copper, it will drop the surplus as CuCl.
As long as there are enough air and HCl the solution will for the most part be green and effective.
The white CuCl will instanty dissolve in HCl and or water.

Tin for stannous can be most anything: pewter, fishing weights and so on.

 

[MarkB]

The solution will not show gold unless it is dissolved.
If you have put gold into solution and it has cemented out, it is in metallic form and stannous will not react.

I must be explaining something incorrectly. I am aware a stannous test will not show gold in a solution if the gold has been cemented out or never dissolved in the first place.

Second if you dissolve pins, other all metal objects or surface only plating without other base metals
one can easy dissolve all metals and then it won't create problems with dissolving the gold alongside it.
Foils is what we like as a result from AP here :wink:
It is wise to shake it vigorously from time to time to loosen the foils.

this aspect was just a side thought I had, but that was essentially what I was asking. I was trying to weigh the pro's and con's of purposely dissolving the gold into solution as a means to avoid having to collect all the foils from an AP solution where PCB or other foreign material remains at the end of the process.

I understand that with the current process, the foils is the end result you are after. I was just trying to brainstorm if in certain situations it may be prudent to dissolve your gold.

As long as you bubble air through the solution you will basically have an everlasting process going.
If it gets saturated with copper, it will drop the surplus as CuCl.
As long as there are enough air and HCl the solution will for the most part be green and effective.
The white CuCl will instanty dissolve in HCl and or water.

Thank you for the explanation. I really struggle with the chemistry, and I think that's just because I don't have sufficient source material.

I have processed ceramic cpu's, processed some gold pins in nitric, etc. When i stopped using actual nitric acid and switched to nitric salts, I felt like I reverted back to square 1. I decided to do this on a whim, as it required to nitric acid up front. Then my pump issues started. Oh well. I'll get there.

Thanks for taking the time to respond. It makes a world of difference.

I took about 2000 ml out and filtered that, storing it in labeled mason jars. Some foils floating, but most were dissolved I am sure. For a visual on the liquid, think making instant coffee. But put in so much, it goes past black and starts to have an almost yellowish color. That's my solution. I Plan on decanting completely, and restarting the process from scratch as a lot of the PCB still has visible gold. I'm not seeing any cemented out material as of now.

Am I glossing over some much needed advice, or just being wreckless? If anyone is available to speak to throughout this, I would be very grateful. I'm not expecting someone to tell me what to do, I'd just like someone to bounce ideas off that can tell me 'yes' or 'no' based on the chemistry and their experience, and occasionally point me in the right direction. Thanks for everyone's time and input.

 

[Yggdrasil]

I'm away on a family visit now and will not be able to give comprehensive replies for the next month or so.
Sorry about that, but there are scores of more competent people than me in here so I'm sure there will be some nuggets of wisdom appearing.

 

[MarkB]

I'm away on a family visit now and will not be able to give comprehensive replies for the next month or so.
Sorry about that, but there are scores of more competent people than me in here so I'm sure there will be some nuggets of wisdom appearing.

I appreciate the time you took already.

I filtered out another 500ml or so. The filter seemed caked with foils, but the majority seemed to be copper foils with some gold mixed in (85/15 roughly). When I opened the filter up once dry to look at it, almost all the foils disappeared. Only trace seems to be a black color, mixed with the filter now. (acid on filter dissolved foils? would that imply the solution was not fully saturated?

Of the filtered solution, I put about 5 grams of copper into 500 ml. No reaction. I looked an hour or two later, copper still untouched. I've got maybe 500 ml more still in the original bucket with all the pcb strips, many with visible gold yet. Some boards seem to have a black char on them. Is that my cemented out gold? I just need to get back to square one on this. I can't tell if my solution is fully saturated or not, as I (most likely erroneously) believe I have signs telling me both ways.

Just flat out lost on this particular project.

 

[DylanDownright84]

Give me some more info. Do you actually have some stannous chloride made up? In a pinch you can scrape some solder off one of your boards and make some with that. What vessels are you using to do this process in? What kind of filters are you using? Coffee filters can and will allow most of the small gold foils to pass right through into the vessel you're filtering into. What does the stannous test show you? What is the Color when a drop of stannous is added to a few drops of your A/P solution? If your A/P solution is too dark for stannous to be effective, put a few drops of your AP in a white, disposable, plastic spoon, add a couple drops of water to lighten it up, give it a light swirl, then add the stannous and watch for a color change. White cotton Q-tips work as well. The white background allows for easier visual inspection of any possible color changes.

I'll try and help you, but I need some more information. I would very much try and avoid putting the gold you're after into the AP solution because it will create much more work and needless headaches for a new member. If you have a couple empty 5 gallon buckets we can use them to try and sort out the issues you're having. A couple decent sized, acid resistant vessels will help. 5 gallon buckets are my default storage for my AP solution among other things.

I'm still learning about more and more myself, but I do have some experience with the AP/ copper II chloride method and will help with what I can.