A process for recovering gold from a gold-containing raw material, comprising leaching the gold-containing material with an aqueous solution comprising elemental bromine and bromide source to form a pregnant leach solution with the gold dissolved therein; separating said pregnant leach solution from the gold-depleted raw material, removing elemental bromine from said pregnant leach solution, extracting the gold from the pregnant leach solution in an acidic environment into an organic extractant, to form a gold-loaded extract and bromide-containing raffmate, stripping the extract with an alkaline aqueous solution to form a gold-bearing aqueous solution, generating gold (Au.sup.0) and treating bromide-containing stream(s) to produce recyclable elemental bromine.

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 extracting a rare earth metal from a mixture of one or more rare earth metals, said method comprising countercurrently 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.

A method for extracting a rare earth metal from a mixture of one or more rare earth metals, said method comprising countercurrently 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.

A method for processing lithium ion battery scrap includes a leaching step of leaching lithium ion battery scrap and subjecting the resulting leached solution to solid-liquid separation to obtain a first separated solution; an iron removal step of adding an oxidizing agent to the first separated solution and adjusting a pH of the first separated solution in a range of from 3.0 to 4.0, then performing solid-liquid separation and removing iron in the first separated solution to obtain a second separated solution; and an aluminum removal step of neutralizing the second separated solution to a pH range of from 4.0 to 6.0, then performing solid-liquid separation and removing aluminum in the second separated solution to obtain a third separated solution.

Provided is a method of recovering rare-earth elements by performing slight pH adjustment of a leachate, which does not require such significant pH adjustment as in conventional methods, reduces cost and effort, and can efficiently recover rare-earth elements in a bauxite residue in a good yield. The method of recovering rare-earth elements is a method of recovering rare-earth elements, the method including: a leaching step of bringing a raw material bauxite residue, which is produced as a by-product in a Bayer process, into contact with a liquid leaching agent to recover a leachate containing rare-earth elements; an extraction step of bringing the leachate into contact with an extraction treatment liquid containing a phosphoric acid ester-based extractant to recover an extract liquid containing the rare-earth elements; and a back extraction step of bringing the extract liquid into contact with a back extraction treatment liquid to recover the rare-earth elements, the leaching step including recovering a leachate having a pH of 0.5 or more and 1.2 or less by using an acidic liquid leaching agent, the extraction step including adjusting the pH of the leachate to 1.0 or more and 1.7 or less and then bringing the leachate into contact with the extraction treatment liquid.

A method for processing lithium ion battery scrap according to this invention includes a leaching step of leaching lithium ion battery scrap to obtain a leached solution; an aluminum removal step of neutralizing the leached solution to a pH range of from 4.0 to 6.0, then performing solid-liquid separation and removing aluminum in the leached solution to obtain a first separated solution; and an iron removal step of adding an oxidizing agent to the first separated solution and adjusting the pH in a range of from 3.0 to 5.0, then performing solid-liquid separation and removing iron in the first separated solution to obtain a second separated solution.

A method for producing an aqueous solution containing nickel, cobalt and manganese, includes: a leaching process including a pressure-leaching process of leaching a raw material under pressure to form a leachate containing nickel, cobalt, manganese and impurities; an impurity removal process of removing the impurities from the leachate; a target substance precipitation process of precipitating a mixed hydroxide precipitate containing nickel, cobalt and manganese by introducing a neutralizing agent into a filtrate from which the impurities are removed; and a dissolution process. The pressure-leaching process includes a first-stage pressure-leaching process and a second-stage pressure-leaching process of pressure-leaching a residue of the first-stage pressure-leaching process with an acidity higher than an acidity in the first-stage pressure-leaching process. The impurity removal process includes a first-stage solvent extraction process of selectively extracting zinc from the impurities and a second-stage solvent extraction process of selectively extracting magnesium from the impurities.

The use of a synergistic mixture of extractants for extracting at least one rare earth element from an aqueous medium comprising phosphoric acid. The mixture comprises: a first extractant of formula (I): ##STR00001##
wherein R.sub.1 and R.sub.2, which are identical or different, represent a linear or branched, saturated or unsaturated hydrocarbon group, comprising from 6 to 12 carbon atoms, or a phenyl group optionally substituted by a linear or branched, saturated or unsaturated hydrocarbon group, comprising from 1 to 10 carbon atoms; anda second extractant of formula (II): ##STR00002##
in which R.sub.3 represents a linear or branched alkyl group, comprising from 6 to 12 carbon atoms. Use of the synergistic mixture in the treatment of phosphate minerals with a view to recovering the rare earth elements contained in the minerals.

The invention provides a method for extracting transition metals, the method comprising supplying a feedstream containing transition metal, mixing the feedstream with nitric acid for a time and at a concentration sufficient to form an aqueous phase containing the transition metal, combining the aqueous phase with organic extractant phase for a time and at a concentration sufficient to cause the transition metal to reside within the organic extractant phase, and combining the transition metal-containing organic extractant phase with an hydroxamic acid-containing aqueous phase at a concentration and for a time sufficient to cause the transition metal to reside in the hydroxamic acid-containing aqueous phase.