I don't know why you think I have been doing anything but studying, & a HARD crash course at that! With all due respect brother, I bet that there isn't one person who has done this gold recovery stuff in all of history who hasn't had to learn thru trial and error... Every single one of us has had questions throughout... But that's the joy of a site like this! It gives us a chance to come together, when we normally would have to struggle alone the whole way, and help each other through our mistakes... So I don't think you have any business judging me or telling me I shouldn't be using chemicals, who are you to make such a call? Then insult me more by telling me Merry Xmas? Wow! Thanks for welcoming a new person into the wonderful hobby, you really made me feel welcome!
It was an educated view on what you have done
we make mistakes, but point of all of you consider "insults" is to focus you more on learning basic principles and consequences of certain chemical reactions. Part with resolving mess created by going with first idea that come to your mind could be practically completely skipped, if you focus on research.
Almost everything we do about refining was done before. You should think about it everytime you are going to process some boards, CPUs, pins, MLCCs etc... Best thing about this forum = you can search key words and find immense quantity of suggestions on how to do it the best and how to certainly not.
With so much available knowledge on the internet (also visualized like YT videos) and espetially here on GRF, you dont need to go through trial and error. It could take few hours of learning, but it can save you whole lot of frustration and money/time.
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Moralizing aside. I dont exactly know how cheaply you could access nitric acid, but to dissolve huge ammounts of base metals, you will need a good bit of it. Pieces of aluminium and iron could be hard to dissolve and you will end up with bunch of crap at the end.
If the foils are relatively "attached" to the boards (still), take them out of the soup and carefully wash them with water. You can throughly wash the boards from nitric (like immersing in the bucket of water) and continue with HCl/air or AP to remove the rest of base metals - much more advised.
If too much foils fell from the boards, it would be more painful. Try not to shake and stirr the container too much, or you will crush the foils to small pieces. Foils could be separated to some extent by pouring the metastannic goo through fine sieve/strainer (not made of metal ofc) - the white goo should pass, foils will rest. If there are too many small golden pieces still after several "strainings", then you will need to filter the metastannic anyway...
With simple gravity filtration it would took ages, but it is what it is. If you have vacuum pump and vacuum filtration setup, it would be easier. As the gold is not leached and is in form of foils, you dont necessarily need filter paper. Some old cloth or non-wowen texile could also help speed it up if used instead of paper (but acid could eat/disintegrate it when soaked for too long).
When you retrieve the foils, cover the goo with HCl and add minute nitric, heat it till all foils dissolve and filter. Should work to make gold go into the solution.