The use of carbamides as extractants for fully or partially separating uranium(VI) from plutonium(IV) in an aqueous solution obtained by dissolving a spent nuclear fuel in nitric acid, by method of liquid-liquid extraction, without carrying out any reduction of the plutonium(IV) to plutonium(III). The invention also relates to new carbamides. Uses are the processing of spent nuclear fuels based on uranium (especially uranium oxides—UOX) or uranium and plutonium (especially mixed uranium and plutonium oxides—MOX).

An extractant which makes it possible to extract both light rare earths and heavy rare earths from an aqueous phosphoric acid solution, likely to be present in this solution, and which is characterised in that it comprises: a compound of formula (I) below: ##STR00001##
wherein R1 and R2, identical or different, are a hydrocarbon group, saturated or unsaturated, linear or branched, in C6 to C12; R3 is a hydrocarbon group, in C1 to C6, or a hydrocarbon group, saturated or unsaturated, monocyclic, in C3 to C8; R4 and R5, identical or different, are a hydrogen atom or a hydrocarbonate group, saturated or unsaturated, linear or branched, in C2 to C8; and a surfactant. Applications of this extractant include treatment of aqueous solutions from the leaching of natural phosphates by sulphuric acid and aqueous solutions from the leaching of urban minerals by phosphoric acid, in view of making profitable use of the rare earths present in these solutions.

The-use of carbamides as extractants for fully or partially separating uranium(VI) from plutonium(IV) in an aqueous solution obtained by dissolving a spent nuclear fuel in nitric acid, by method of liquid-liquid extraction, without carrying out any reduction of the plutonium(IV) to plutonium(III). The invention also relates to new carbamides. Uses are the processing of spent nuclear fuels based on uranium (especially uranium oxides—UOX) or uranium and plutonium (especially mixed uranium and plutonium oxides—MOX).

Described herein is a process for stepwise leaching of all rare earth elements capable of forming peroxide and superoxide compounds, in particular cerium, lanthanum, neodymium, europium, from minerals containing these elements, namely from bastnaesites, orthites, chevkinites, and britholites.

A new extractant which makes it possible to extract both light rare earths and heavy rare earths from an aqueous phosphoric acid solution, likely to be present in this solution, and which is characterised in that it comprises: a compound of formula (I) below: wherein R1 and R2, identical or different, are a hydrocarbon group, saturated or unsaturated, linear or branched, in C6 to C12; R3 is a hydrocarbon group, in C1 to C6, or a hydrocarbon group, saturated or unsaturated, monocyclic, in C3 to C8; R4 and R5, identical or different, are a hydrogen atom or a hydrocarbonate group, saturated or unsaturated, linear or branched, in C2 to C8; anda surfactant. It also relates to the applications of this new extractant: treatment of aqueous solutions from the leaching of natural phosphates by sulphuric acid and aqueous solutions from the leaching of urban minerals by phosphoric acid, in view of making profitable use of the rare earths present in these solutions.

A method for recovering hafnium and impurity metals from a hafnium-containing waste residue, comprises dissolving the waste residue in sulfuric acid and ammonium sulfate to obtain an acidic solution, adjusting acidity of the acidic solution, and adding a complexing agent to obtain a material solution; conducting extraction to obtain a hafnium-loaded organic phase and an impurity metal ions-containing aqueous phase; subjecting the hafnium-loaded organic phase to purification, stripping, precipitation, and filtration, and washing and burning to obtain hafnium oxide; precipitating the impurity metal ions-containing aqueous phase, washing a resulting precipitate to remove the complexing agent; dissolving a resulting precipitates of the impurity metal ions in sulfuric acid, and adjusting acidity of a resulting solution to obtain a solution of the impurity metal ions; extracting the solution of the impurity metal ions to obtain an impurity metal ions-loaded organic phase, purifying and stripping to obtain oxides of the impurity metals.

In one aspect, the disclosure relates to oxalic acid-based extraction methods for the preparation of a pregnant leach solution obtained from a loaded organic phase obtained from a solvent extraction system, i.e., a LOPSES, wherein the loaded organic phase comprises an organic solvent and at least one REE and/or CM, as well as pregnant leach solution products or compositions obtained by the disclosed methods. The disclosure further relates to methods for preparing a loaded organic phase using a solvent extraction system. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.