These are some of the substances to be found in used potlinings from aluminium reduction cells. They were at one time disposed of by ground burial. This was not a good idea since as well as various fluorides and carbides, they also contain substantial amounts of cyanide
Under a US Bureau of Mines, I led an investigation into finding the best way of treating these materials, which was the subject of one of the cover mentioned stories in the Journal of Metals. My recommended approach was to pressure cook the old potlining in hot water, and then recover the carbon to be recycled into new potlinings.There would still be some residue,but it would be safe to dump. I believe ALCOA now does something along these lines .
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