Provided are an extraction agent and extraction method that selectively extract and, at a low cost, recover gallium from an acidic solution containing gallium and zinc. The gallium extraction agent comprises an amide derivative represented by general formula (I). In the formula, R.sup.1 and R.sup.2 each indicate the same or different alkyl group, R.sup.3 indicates a hydrogen atom or an alkyl group, and R.sup.4 indicates a hydrogen atom or any given group, other than an amino group, bonded to the α-carbon as an amino acid. The general formula preferably has a glycine unit, a histidine unit, a lysine unit, an aspartic acid unit, or an N-methylglycine unit. By extracting gallium from an acidic solution containing gallium and zinc by means of solvent extraction using the extraction agent, it is possible to selectively extract gallium.

A method of selectively removing impurities from a scandium-containing feed solution includes contacting an aqueous scandium-containing solution with an organic solvent stream containing an extractant, thereby forming a loaded organic solvent stream containing the impurity or impurities while leaving the scandium in the raffinate. The aqueous stream containing the scandium is washed, diluted and has inorganic salts added before being contacted with a second organic solvent stream to extract the scandium selectively, and followed by stripping the scandium from the scandium-containing loaded organic extractant stream by adding oxalic acid to the loaded organic extractant stream to form scandium oxalate.

The present disclosure relates to a method for separating yttrium oxide from a high-yttrium rare earth ore by a grouping manner and a method for separating yttrium oxide from a medium-yttrium and europium-rich rare earth ore by a grouping manner, and belongs to the technical field of rare earth extraction and separation. The separating method by a grouping manner according to the present disclosure have advantages such as being advanced and reasonable, short process, low production cost, good adaptability, and easy operation and control. The method has better overall technical and economic indicator performance than the naphthenic acid process and has the value of practical application.

Provided is a method for leaching nickel from a nickel oxide ore that enables a nickel sulfate production method which is easily carried out with a small amount of waste generation. The method for leaching nickel into an organic phase disclosed here includes the step of bringing a nickel ore into contact with an organic phase. The organic phase contains a hydrophobic deep eutectic solvent including a hydrogen bond donor and a hydrogen bond acceptor, and an organic acid. The hydrogen bond donor is an acidic hydrogen bond donor. The organic acid is a strong acid.

The extraction system contains secondary amides and alkyl alcohols which are separately used as the extractants for extracting lithium and boron and consist of a single compound or a mixture of two or more compounds, and the total number of carbon atoms in their molecules are 12˜18 and 8˜20 respectively; the extraction system has a freezing point less than 0° C. With a volume ratio of an organic phase and a brine phase being 1˜10:1, at a brine density of 1.25˜1.38 g/cm.sup.3, at a brine pH value of 0˜7 and at a temperature of 0˜50° C., a single-stage or multi-stage countercurrent extraction and a stripping are conducted to obtain a water phase with a low magnesium-lithium ratio, which is subjected to concentration, impurity removal and preparation to get lithium chloride, lithium carbonate, lithium hydroxide and boric acid respectively. Water is used for stripping, greatly reducing the consumption of acid and base.

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; and —a 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.

A method for extracting rare earth elements from aqueous solution, comprising: (i) acidifying an aqueous solution containing said rare earth elements with an inorganic acid to result in an acidified aqueous solution containing said rare earth elements and containing the inorganic acid in a concentration of 1-12 M, wherein said rare earth elements are selected from lanthanides, actinides, or combination thereof, and (ii) contacting the acidified aqueous solution with an aqueous-insoluble hydrophobic solution comprising a rare earth extractant compound dissolved in an aqueous-insoluble hydrophobic solvent to result in extraction of one or more of the rare earth elements into the aqueous-insoluble hydrophobic solution by binding of the rare earth extractant compound to the one or more rare earth elements, wherein the rare earth extractant compound has the following structure:

##STR00001##

provided that at least one of the conditions (a)-(d) applies.

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 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 raffinate, 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 method of selectively removing impurities from a scandium-containing feed solution includes contacting an aqueous scandium-containing solution with an organic solvent stream containing an extractant, thereby forming a loaded organic solvent stream containing the impurity or impurities while leaving the scandium in the raffinate. The aqueous stream containing the scandium is washed, diluted and has inorganic salts added before being contacted with a second organic solvent stream to extract the scandium selectively, and followed by stripping the scandium from the scandium-containing loaded organic extractant stream by adding oxalic acid to the loaded organic extractant stream to form scandium oxalate.