Abstract: A method for selectively removing sodium or potassium from an alkaline lithium-containing aqueous solution, the method comprising: (i) contacting the alkaline lithium-containing aqueous solution with a hydrophobic solution comprising: (a) an aqueous-insoluble hydrophobic solvent, (b) a protic ionic liquid of the formula X?Y+, wherein X? is a conjugate base of a superacid and Y+ is a protonated cation, and (c) at least one of lipophilic sodium-selective and potassium-selective complexing ligands, wherein the contacting step results in selective complexation with and removal of sodium and/or potassium ions from the lithium-containing aqueous solution into the hydrophobic solution along with simultaneous abstraction of a proton from Y+ to form Y; and (ii) separating the aqueous solution from the hydrophobic solution, wherein, in some embodiments, X? is a bis(sulfonyl)imide and Y+ is a protic ammonium species.