Patent ID: 11866804
Assignee: PURDUE RESEARCH FOUNDATION
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  Y | IPC C

Claim 11:
12. A process for preparing pure chemicals from coal ash, the process comprising:
a. extracting coal ash with a caustic solution at a temperature elevated above ambient;
b. separating undissolved solid residue from said caustic extraction solution and washing said undissolved solid residue with water;
c. treating the water washed solid residue with an acid at a mass ratio of solid to acid about 1:10 and then separating leftover solid to afford an acidic extraction solution;
d. loading the acidic extraction solution to a cation exchange column and collecting the pass-through eluent;
e. treating the pass-through eluent with a base to pH about 3, at which point iron hydroxide precipitates out and is isolated; then bringing the pH of the solution up to about 8 whereby aluminum hydroxide precipitates out and is isolated; and
f. eluting the loaded cation exchange column first with a solution of sodium chloride to afford fractions containing aluminum and iron, and then with a solution of a chelating ligand to afford fractions of enriched REEs;
wherein the caustic extraction solution includes both sodium hydroxide and potassium hydroxide.