Low-cost selective precipitation circuit for recovery of rare earth elements from acid leachate of coal waste

A method for concentrating rare earth materials from a feed stock, the method comprising:

• a) mixing the feed stock with an acid in a solution;
• b) precipitating contaminants and removing the precipitated contaminants from the solution;
• c) subsequently precipitating rare earth metals from the solution and separating the precipitated rare earth metals from a resulting filtrate;
• d) re-dissolving the precipitated rare earth metals in a smaller volume of the filtrate;
• and
• e) transferring the re-dissolved filtrate to an acid solution.

A method for concentrating rare earth elements, comprising:

• a) mixing a feed material comprising a coal leachate and/or precipitate obtained therefrom with an acidic solution in a pH of 2.70±0.5;
• b) increasing the pH incrementally to 3.2±0.5, then 3.8±0.5 to precipitate iron when Fe3+ is dominant;
• c) adding hydrogen peroxide to completely or partially transform Fe2+ to Fe3+ prior to step (b) when Fe2+ is dominant iron species in solution;
• d) filtering iron from b);
• e) increasing the pH incrementally to 4.8±0.5 to precipitate aluminum;
• f) filtering aluminum from e);
• g) increasing the pH incrementally to 8.5±0.5 to precipitate rare earth elements;
• and
• h) filtering the rare earth elements to obtain a sequential rare earth precipitate and retaining the subsequent filtrate.