The invention relates to a hydrometallurgical process which makes it possible to selectively recover at least one heavy rare earth metal, i.e. a rare earth metal with an atomic number at least equal to 62, that is in an acidic aqueous phase resulting from the treatment of spent or scrapped permanent magnets. It also relates to a hydrometallurgical process which makes it possible to selectively recover, on the one hand, at least one heavy rare earth metal present in an acidic aqueous phase resulting from the treatment of spent or scrapped permanent magnets and, on the other hand, at least one light rare earth metal, i.e. a rare earth metal with an atomic number at most equal to 61, that is also in this acidic aqueous phase. The invention has in particular an application in the recycling of rare earth metals present in spent or scrapped permanent magnets of the type Neodymium-Iron-Boron (or NdFeB) and, in particular, dysprosium, praseodymium and neodymium, and also in the recycling of samarium present in spent or scrapped permanent magnets of the type samarium-cobalt (or SmCo).

The invention relates to the ROANEX method, which extracts actinides from used nuclear fuel in a single purification cycle. The used nuclear fuel contains actinides, U, Am, Pu, Np. and Cm, and fission products, Cs, Sr and Tc. The fission products are separated first from the used nuclear fuel. The actinides are reduced to their lowest oxidation states and then oxidized to their highest oxidations states. Uranium, Pu and Np move to an organic phase solution and Am and Cm move to a nitrate solution. Uranium, Pu, and Np are stripped from the organic phase solution, and then treated with an oxalic acid to form a precipitate. Americium and Cm are treated with a potassium carbonate solution and Am precipitates. Actinides Am, U, Pu, and Np precipitates are heated in an oven and then blended together to form a mixed oxide fuel of UO.sub.2, PuO.sub.2, NpO.sub.2 and AmO.sub.2.

Novel dissymmetric N,N-dialkylamides which meet the following formula (I): ##STR00001##
where R represents a linear or branched alkyl group at C.sub.8 to C.sub.15. A method for synthesizing these N,N-dialkylamides, and to the uses of same as extractants, alone or in admixture, in order to extract uranium and/or plutonium from an aqueous acid solution, or to totally or separate uranium from plutonium from an aqueous acid solution and, in particular, an aqueous solution resulting from dissolving spent nuclear fuel in nitric acid. Further, a method for processing an aqueous solution resulting from the dissolution of a spent nuclear fuel in nitric acid, allowing the uranium and plutonium contained in the solution to be extracted, separated and decontaminated in a single cycle, without requiring any plutonium reduction operation, and in which one of the aforementioned N,N-dialkylamides or a mixture of same is used as extractant. Applications for the method include the processing of spent nuclear fuels, in particular comprising uranium (e.g. UOX) or uranium and plutonium (e.g. MOX).

The invention relates to compounds which correspond to the general formula (I) below: ##STR00001## in which: R.sup.1 and R.sup.2 represent, independently of one another, a C.sub.4 to C.sub.12 acyclic hydrocarbon group; R.sup.3 represents H; a C.sub.1 to C.sub.12 acyclic hydrocarbon group with optionally one or more heteroatoms; a C.sub.5 or C.sub.6 cyclic hydrocarbon group; or a 5- or 6-membered heterocyclic group; R.sup.4 represents H or a C.sub.1 to C.sub.12 acyclic hydrocarbon group with optionally one or more heteroatoms; R.sup.5 and R.sup.6 represent, independently of one another, H; a C.sub.1 to C.sub.12 acyclic hydrocarbon group with optionally one or more heteroatoms; a C.sub.5 or C.sub.6 cyclic hydrocarbon group; or a 5- or 6-membered heterocyclic group; on the condition however that R.sup.5 and R.sup.6 do not each represent H. The invention also relates to the uses of these compounds as uranium(VI) ligands, in particular for extracting uranium(VI) from an aqueous solution of sulphuric acid, and also to a method that makes it possible to recover the uranium(VI) present in an aqueous solution of sulphuric acid resulting from the attack of a uranium ore by sulphuric acid and using said the compounds.

Nanofiltration can be used to improve a hydrometallurgical process in which valuable metal is extracted from ore or tailings by leaching with a suitable lixiviant. The process requires at least two nanofiltration subsystems in which raffinate from a solvent extraction process is treated in a nanofiltration subsystem, after which permeate therefrom is combined with a pregnant solution stream and is treated in a second nanofiltration subsystem. This arrangement can lead to advantages in the amount of lixiviant recovered, in the raw materials required, in the effluent produced, in the size of plant, and in overall cost.

Novel dissymmetric N,N-dialkylamides which meet the following formula (I):

##STR00001##

where R represents a linear or branched alkyl group at C.sub.8 to C.sub.15. A method for synthesizing these N,N-dialkylamides, and to the uses of same as extractants, alone or in admixture, in order to extract uranium and/or plutonium from an aqueous acid solution, or to totally or separate uranium from plutonium from an aqueous acid solution and, in particular, an aqueous solution resulting from dissolving spent nuclear fuel in nitric acid. Further, a method for processing an aqueous solution resulting from the dissolution of a spent nuclear fuel in nitric acid, allowing the uranium and plutonium contained in the solution to be extracted, separated and decontaminated in a single cycle, without requiring any plutonium reduction operation, and in which one of the aforementioned N,N-dialkylamides or a mixture of same is used as extractant. Applications for the method include the processing of spent nuclear fuels, in particular comprising uranium (e.g. UOX) or uranium and plutonium (e.g. MOX).

A method for the treatment of an aqueous solution resulting from the dissolution of a spent nuclear fuel in nitric acid, allowing the uranium and plutonium contained in the solution to be extracted, separated and decontaminated in a single cycle, without requiring any operation involving a reductive stripping of plutonium. Applications for the method include the processing of uranium-based and/or plutonium-based spent nuclear fuels.

The application relates to a method for separating iron from an initial liquid organic phase containing uranium and iron, wherein the initial liquid organic phase is contacted with an aqueous solution referred to as aqueous de-ironing solution, whereby the iron passes into the aqueous solution to form a final liquid aqueous phase, and uranium remains in the initial liquid organic phase to form a final liquid organic phase referred to as de-ironed organic phase. The method is characterised in that the aqueous de-ironing solution contains an inorganic acid and uranium, and does not contain iron. The application also relates to a method for extracting uranium from an aqueous solution of an inorganic acid containing uranium and iron.

Protactinium, actinium, radium, radiolanthanides and other radionuclide fission products were separated and recovered from a proton-irradiated thorium target. The target was dissolved in concentrated HCl, which formed anionic complexes of protactinium but not with thorium, actinium, radium, or radiolanthanides. Protactinium was separated from soluble thorium by loading a concentrated HCl solution of the target onto a column of strongly basic anion exchanger resin and eluting with concentrated HCl. Actinium, radium and radiolanthanides elute with thorium. The protactinium that is retained on the column, along with other radionuclides, is eluted may subsequently treated to remove radionuclide impurities to afford a fraction of substantially pure protactinium. The eluate with the soluble thorium, actinium, radium and radiolanthanides may be subjected to treatment with citric acid to form anionic thorium, loaded onto a cationic exchanger resin, and eluted. Actinium, radium and radiolanthanides that are retained can be subjected to extraction chromatography to separate the actinium from the radium and from the radio lanthanides.

The invention relates to compounds which correspond to the general formula (I) below:

##STR00001##

in which: R.sup.1 and R.sup.2 represent, independently of one another, a C.sub.4 to C.sub.12 acyclic hydrocarbon group; R.sup.3 represents H; a C.sub.1 to C.sub.12 acyclic hydrocarbon group with optionally one or more heteroatoms; a C.sub.5 or C.sub.6 cyclic hydrocarbon group; or a 5- or 6-membered heterocyclic group; R.sup.4 represents H or a C.sub.1 to C.sub.12 acyclic hydrocarbon group with optionally one or more heteroatoms; R.sup.5 and R.sup.6 represent, independently of one another, H; a C.sub.1 to C.sub.12 acyclic hydrocarbon group with optionally one or more heteroatoms; a C.sub.5 or C.sub.6 cyclic hydrocarbon group; or a 5- or 6-membered heterocyclic group; on the condition however that R.sup.5 and R.sup.6 do not each represent H.