US Patent 9394586 Recovery of rare earth elements and compounds from coal ash

The coal ash can be sorted into groups of substantially unburned carbon and substantially burned carbon. The substantially unburned carbon or the substantially burned carbon can be magnetically treated to cause separation into a substantially magnetic portion and a substantially non-magnetic portion. The substantially magnetic portion or the substantially non-magnetic portion can be filtered into a substantially course portion and a substantially fine portion. The substantially coarse portion or the substantially fine portion can be treated with a mineral acid to form an aqueous mineral acid solution. The aqueous mineral acid solution can be extracted to form an organic solution that includes the rare earth salts. The organic solution can be mixed with water to form an aqueous solution that includes the rare earth salts. The rare earth salts can be separated from the aqueous solution.