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.

A major object is to provide a method of producing a cathode active material having a high average discharge potential, and a high degree of stability at high potential. The method includes: a step of preparing a Na-doped precursor of making a sodium-containing transition metal oxide having the P2 structure belonging to a space group of P6.sub.3/mmc; and an ion exchange step of substituting lithium for at least part of sodium contained in the sodium-containing transition metal oxide by the ion exchange method, wherein in the ion exchange step, at least lithium iodide is used as a Li ion source.

Method of separation of a radiometal ion from a target metal ion, comprising a first liquid-liquid extraction step in which an organic phase comprising an extractant and an interfacial tension modifier is mixed with an aqueous phase comprising the radiometal ion and the target metal ion in order that the radiometal ion is at least partially transferred to the organic phase, followed by a first phase separation step, wherein the phase separation is carried out in flow comprising the use of a microfiltration membrane to separate the phases based on the interfacial tension between the phases such that a permeate phase passes through the membrane and a retentate phase does not.

A method for recovering NiSO.sub.4.6H.sub.2O crystals from a nickel rich organic phase is provided. The method includes contacting a nickel rich organic phase with an aqueous strip solution of sufficient H.sub.2SO.sub.4 concentration to extract nickel from the organic phase and of sufficient Ni.sup.2+ concentration to precipitate NiSO.sub.4.6H.sub.2O crystals and form a nickel lean organic phase. Also provided are methods for recovering NiSO.sub.4.6H.sub.2O crystals that include preceding processing steps, including low temperature pressure oxidation (LTPOX) autoclaving of a nickel sulphide concentrate to afford a pregnant leach solution (PLS).

Disclosed in the present invention is a method for preparing nickel sulfate from a nickel-iron-copper alloy. The method comprises: in a high-pressure oxygen environment, mixing a nickel-iron-copper alloy crushed material, aqueous ammonia, ammonium sulphate, and a corrosion assisting agent, leaching, then performing solid-liquid separation on the leached slurry, adding a precipitant into a filtrate, and performing ammonia distillation to obtain a nickel-containing leachate; then adding an extractant into the nickel-containing leachate to extract nickel so as to obtain a nickel-containing extraction organic phase; and then adding sulfuric acid into the nickel-containing extraction organic phase to perform back extraction of nickel so as to obtain a nickel sulfate solution. According to the present invention, the nickel-iron-copper alloy is separated by using different properties of nickel and iron, nickel is dissolved in a hexamine complex of nickel, iron cannot be dissolved and then continues to be remained in a solid, after the filtrate is collected, the precipitant is added and ammonia distillation is performed to remove copper, the aqueous ammonia is recycled, and the copper ions react with the precipitant to generate a copper sulfide precipitate, and thus, copper in the filtrate is removed, and the purity of nickel sulfate is further improved.

A novel process for treating pickling acid residue and recovering sulfates and nickel therefrom has been developed. By lowering the pH of a magnesium compound slurry to 4-5.5 with sulfuric acid containing pickling acid residue in the presence of ammonium sulfate, both magnesium sulfate and nickel sulfate are solubilized. Magnesium sulfate and nickel sulfate solution is separated from the solids by filtration and an iron hydroxide and chromium hydroxide residue is obtained as a precipitate. Magnesium sulfate and nickel sulfate are then separated from the solution.

A major object is to provide a method of producing a cathode active material having a high average discharge potential, and a high degree of stability at high potential. The method includes: a step of preparing a Na-doped precursor of making a sodium-containing transition metal oxide having the P2 structure belonging to a space group of P6.sub.3/mmc; and an ion exchange step of substituting lithium for at least part of sodium contained in the sodium-containing transition metal oxide by the ion exchange method, wherein in the ion exchange step, at least lithium iodide is used as a Li ion source.

This application pertains to methods of recovering metals from metal sulfides that involve contacting the metal sulfide with an acidic sulfate solution containing ferric sulfate and a reagent that has a thiocarbonyl functional group, wherein the concentration of reagent in the acidic sulfate solution is sufficient to increase the rate of metal ion extraction relative to an acidic sulfate solution that does not contain the reagent, to produce a pregnant solution containing the metal ions.

Provided is a method for inhibiting extractant degradation in the DSX process through the metal extraction control, the method comprising steps of: (a) adding limestone to a copper solvent extraction-raffinate to precipitate iron (Fe) and aluminum (Al) as a slurry, recovering a clarifying liquid; and (b) adding sulfuric acid to the recovered clarifying liquid to adjust the pH thereof.

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.