Europium is also used in Euro banknotes as an anti-counterfeiting measure, again as a phosphor that glows under UV light (in physical terms it's the same application as a fluorescent tube)
Now I wonder how much inflation would be necessary to make "mining" europium from low denomination Euro banknotes profitable. There's places were "mining" copper from street poles is already profitable, and wire theft is a huge problem.
> There's places were "mining" copper from street poles is already profitable, and wire theft is a huge problem.
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.
It's currently illegal to melt down pennies for scrap metal. Every so often there are stories about hedge funds who have millions of them and are waiting or lobbying for the laws to change [0]
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.
Mercury isn't mentioned in the paper (1). Keep in mind this is less about cleaning up than finding an economical way to recover and recycle rare earth metals
