Efficient extraction of metals (and materials that can be broken down to useful precursors) from landfills and 'e-waste'. My PhD supervisor worked for years before he retired, on, among other things, magnetic separation using inhomogeneous magnetic fields. It would be a great pity if such work were forgotten.
Disclaimer (does it really need one?): On the first link above: I shared responsibility for the menial editing, checking and manual indexing of the entire book volume.
Not sure. I know that the conglomerate Outokumpu once had a pilot plant with high-Tc superconducting magnets deployed in the Amazon region somewhere ('Ice in the jungle'? Hah, hold my beer, try liquid-helium cooled superconducting magnets in the jungle).
I know because a colleague joined the company, and one of his first assignments was to diagnose unexpectedly large helium losses. A quick FFT later of the recorded Dewar flask levels revealed a 24-hour periodicity, and further analysis found that for a couple of hours every day, the full heat of the tropical sun was finding its way to the tin roof of the mine shed housing the superconducting magnet systems.
I haven't heard anything more about the technology or its economics/scaling since then. But I also certainly haven't heard anything more about its use with landfill-derived feedstocks, which seems like a reasonable move.
