Methods for liquid extraction of rare earth metals using ionic liquids

A method for extracting a rare earth element from a rare earth-containing substance, the method comprising mixing the rare earth-containing substance with a protic ionic liquid having the following formula:

• wherein R1 is selected from the group consisting of hydrogen and hydrocarbon groups containing at least 1 and up to 12 carbon atoms;
• R2 and R3 are independently selected from the group consisting of hydrocarbon groups containing at least 1 and up to 12 carbon atoms;
• and X− is an anionic species;
• wherein said mixing results in a solution comprising a rare earth composition of the formula (RE)(amide)yXz at least partially dissolved in said protic ionic liquid, wherein RE is at least one rare earth element having an atomic number selected from the group consisting of 39, 57-71, and 90-103 and having a positive oxidation state;
• y is 2-6;
• z is a number that charge balances the total positive charge of the at least one rare earth element (RE);
• X is equivalent to X− in the ionic liquid of Formula (1);
• and said amide is the conjugate base of the cationic portion of the protic ionic liquid of Formula (1) and has the following formula: