The present disclosure is directed to novel functionalized ionic liquids (ILs) that are used, for example, for enhanced recovery and separation of rare earth elements from aqueous solutions. The liquids and processes disclosed herein lead to greater separation efficiency, increased stability of separation materials, increased selectivity, and a reduced amount of waste materials.

The present disclosure is directed to novel functionalized ionic liquids (ILs) that are used, for example, for enhanced recovery and separation of rare earth elements from aqueous solutions. The liquids and processes disclosed herein lead to greater separation efficiency, increased stability of separation materials, increased selectivity, and a reduced amount of waste materials.

Rare earth extractant compounds having the following structure:

##STR00001##

wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently selected from alkyl groups containing 1-30 carbon atoms and optionally containing an ether or thioether linkage connecting between carbon atoms, provided that the total carbon atoms in R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is at least 12; R.sup.5 and R.sup.6 are independently selected from hydrogen atom and alkyl groups containing 1-3 carbon atoms; and provided that at least one of the conditions (i)-(iv) apply as follows: presence of a distal branched group in at least one of R.sup.1-R.sup.4 (condition i), asymmetry in R.sup.1-R.sup.4 (condition ii), presence of amine-containing ring (condition iii), or presence of lactam ring (condition iv). Also described are hydrophobic water-insoluble solutions containing at least one extractant compound of Formula (1), as well as method for extracting rare earth elements from aqueous solution by contacting the aqueous solution with the water-insoluble solution.

Rare earth extractant compounds having the following structure:

##STR00001##

wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently selected from alkyl groups containing 1-30 carbon atoms and optionally containing an ether or thioether linkage connecting between carbon atoms, provided that the total carbon atoms in R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is at least 12; R.sup.5 and R.sup.6 are independently selected from hydrogen atom and alkyl groups containing 1-3 carbon atoms; and provided that at least one of the conditions (i)-(iv) apply as follows: presence of a distal branched group in at least one of R.sup.1-R.sup.4 (condition i), asymmetry in R.sup.1-R.sup.4 (condition ii), presence of amine-containing ring (condition iii), or presence of lactam ring (condition iv). Also described are hydrophobic water-insoluble solutions containing at least one extractant compound of Formula (1), as well as method for extracting rare earth elements from aqueous solution by contacting the aqueous solution with the water-insoluble solution.

A method for extracting a rare earth metal from a mixture of one or more rare earth metals, said method comprising contacting an acidic solution of the rare earth metal with a composition which comprises an ionic liquid to form an aqueous phase and a non-aqueous phase into which the rare earth metal has been selectively extracted, wherein the ionic liquid has the formula [Ca.sup.++][X′], where [X′] represents a phosphinate anion.

A method for extracting a rare earth metal from a mixture of one or more rare earth metals, said method comprising contacting an acidic solution of the rare earth metal with a composition which comprises an ionic liquid to form an aqueous phase and a non-aqueous phase into which the rare earth metal has been selectively extracted, wherein the ionic liquid has the formula [Ca.sup.++][X′], where [X′] represents a phosphinate anion.

A method for recovering scandium, by which scandium is able to be recovered from nickel oxide ore. The present invention comprises: a leaching step S1 for obtaining a leachate by leaching a nickel oxide ore containing scandium with use of sulfuric acid; a neutralization step by adding a neutralizing agent thereto; a sulfurization step by adding a sulfurizing agent to the post-neutralization solution; an ion exchange step by bringing the post-sulfurization solution into contact with a chelating resin; a dissolution step by obtaining a precipitate of scandium hydroxide by adding an alkali into the scandium eluent, and subsequently adding an acid solution to the scandium hydroxide; a solvent extraction step by bringing the scandium acid dissolution liquid into contact with a neutral extractant; and a scandium recovery step by adding oxalic acid to the extraction residue and subsequently roasting the salt of scandium oxalate.

A method for recovering scandium, by which scandium is able to be recovered from nickel oxide ore. The present invention comprises: a leaching step S1 for obtaining a leachate by leaching a nickel oxide ore containing scandium with use of sulfuric acid; a neutralization step by adding a neutralizing agent thereto; a sulfurization step by adding a sulfurizing agent to the post-neutralization solution; an ion exchange step by bringing the post-sulfurization solution into contact with a chelating resin; a dissolution step by obtaining a precipitate of scandium hydroxide by adding an alkali into the scandium eluent, and subsequently adding an acid solution to the scandium hydroxide; a solvent extraction step by bringing the scandium acid dissolution liquid into contact with a neutral extractant; and a scandium recovery step by adding oxalic acid to the extraction residue and subsequently roasting the salt of scandium oxalate.

A method is provided for separating and/or purifying different metal oxalates by mixing the different metal oxalates in an aqueous solution comprising oxalic acid and an organic base so that at least one metal oxalate is soluble and at least another metal oxalate is not soluble. Different rare earth metal oxalates and/or transition metal oxalates can be separated.

A method is provided for separating and/or purifying different metal oxalates by mixing the different metal oxalates in an aqueous solution comprising oxalic acid and an organic base so that at least one metal oxalate is soluble and at least another metal oxalate is not soluble. Different rare earth metal oxalates and/or transition metal oxalates can be separated.