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Originally Posted by pixeljedi /img/forum/go_quote.gif
What molarity are you thinking of trying this with? The other downside of course, is burning a hole through your hand or other body part - and then having to toothbrush scrub the wound with baking soda to stop the acid from eating through more organic material (horror stories from University). Might not be worth the PCB But I'd be willing to try it in a lab where I could control all the variables.
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1-6? Also needs nitric acid and potassium chloride. Definitely not thinking about trying it. It's easier to get all the excess copper out, so it can be more environmentally friendly, but there's more fumes than with the other methods, and the fumes are a lot more dangerous. (Mutters something about needing a gas mask.) It's just that I've been reading about all the methods and how to use them safely over the long term, including storage and disposal. The second to last thing I want to do (next to die a quick but painful death) is dump copper down the drain.
Been looking around since seeing this thread. There's plenty of stuff on the web about regenerating cupric chloride (CuCl). I haven't looked in enough detail, but it looks like you can regenerate FeCl easier and safer than CuCl, and without having excess poisonous etchant grow over time. The FeCl bath would grow, but iron's not nearly the problem to get rid of.
You can recover the copper from FeCl through electro-whatever the word is. It might even be possible without electricity, just a steel spoon. The iron displaces copper in solution and you get a coating of copper on the spoon. The same thing that makes it hard to precipitate the copper makes the iron displace the copper. Aluminum would work, too, but you don't want to make the bath too complicated.
If you try to do something like this in a CuCl solution, you'd give off chlorine gas, which you'd have to replenish with hydrochloric acid (HCl) and just end up diluting the solution or making more of it.
You can also reduce the sludge by using acid and by bubbling with air. Look up Edinburgh Etch. It uses citric acid--vitamin C. Most any acid would probably do, but I'd probably only substitute HCl for safety.
The main reason I don't like FeCl is that you're forced to dispose of copper into the environment. Neutralizing it with baking soda or lime and then bricking it in concrete isn't safe at all. It's a lot more complicated than that. If you could really neutralize the copper, you could precipitate it or something, and dispose of it properly, but it's more difficult to do this in FeCl than almost any other etchant.
Maybe there's hope here. Will keep looking into it. I'm sure there's something missing or people would be doing it.
