Preparation of rare earth metals and other chemicals from industrial waste coal ash

A process for preparing pure chemicals from coal ash, the process comprising:

• a. extracting coal ash with a first caustic solution at an elevated temperature;
• b. separating undissolved solid residue from said first caustic extracting solution, wherein said first caustic solution is stored for later processing and said solid residue is washed briefly with water;
• c. treating the water washed solid residue with a first acid, wherein pH of the resulting acidic solution is maintained at about 3 and then the leftover solid is separated and washed with water;
• d. extracting the water washed solid with a second caustic solution at an elevated temperature;
• e. separating undissolved solid residue from the second caustic extracting solution, wherein said second caustic solution is stored for later processing and said undissolved solid residue is washed briefly with water;
• f. treating the undissolved solid residue with a second acid to bring the pH of the resulting acidic solution to about 3, and isolating the leftover solid as a pure iron oxide with aluminum silicate;
• g. combining the acidic extraction solutions from steps c and f, and adjusting the pH to about 5 with a base whereby pure aluminum silicate precipitates out from the solution as a product and the leftover solution contains enriched rare earth elements (REEs);
• and
• h. combining the first and the second caustic extracting solutions to recover pure sodium silicate by pH adjustment with an acid;
• wherein at least one of the first and second caustic extraction solutions contains sodium hydroxide.