Rapid extraction of europium from spent fluorescent lamps
ethz.ch
ethz.ch
I don't think that's really "profitable" in any way besides theft being profitable. People who do that typically cause orders of magnitude more damage than the money they get for the scrap.
IIRC, it's already profitable to "mine" copper from pre-1982 pennies. IIRC, those contain something like 2-3 cents worth of copper, at current prices. I saw a machine once, online, that would automatically sort out copper pennies from zinc ones.
I think it's mostly a cute story rather than a real business opportunity. The costs of operations and storage add up, even if you can wave away the time-value-of-money costs by holding them in an institution that is required to keep $X in cash.
[0] https://www.cnbc.com/2011/10/05/kyle-basss-nickel-collection...