Abstract: The present invention relates to a method for treating lithium ion battery scrap containing Li, Ni, Co, Mn, Al, Cu and Fe, the method comprising carrying out a calcination step, a crushing step and a sieving step in this order, and after the steps, the method comprising: a leaching step of leaching the lithium ion battery scrap by adding it to an acidic solution to leave at least a part of Cu as a solid; a Fe/Al removal step comprising allowing a leached solution obtained in the leaching step to pass through a Fe removal process for separating and removing Fe by addition of an oxidizing agent and an Al removal process for separating and removing a part of Al by neutralization in any order; an Al/Mn extraction step of extracting and removing a residue of Al and Mn from a separated solution obtained in the Fe/Al removal step by solvent extraction; a Co recovery step of extracting and back-extracting Co from a first extracted solution obtained in the Al/Mn extraction step by solvent extraction and recovering the

Abstract: Disclosed is a method for producing battery-grade nickel sulfate by using laterite nickel ore comprising the following steps: sorting the laterite nickel ore to obtain lump ore and sediment ore; crushing the lump ore, and then performing heap leaching, to obtain a crude nickel sulfate solution A; separating the sediment ore to obtain high chromium ore, low iron, high magnesium ore, and high iron, low magnesium ore, and drying, roasting, reducing, and sulfurating the low iron, high magnesium ore to obtain low nickel matte; blowing and performing water extraction on the low nickel matte, and then performing oxygen pressure leaching, to obtain a crude nickel sulfate solution B; performing pressure leaching on the high iron, low magnesium ore to obtain a crude nickel sulfate solution C; and performing extraction on the crude nickel sulfate solutions A, B, and C, and then evaporating and crystallizing, to obtain battery-grade nickel sulfate.

Abstract: A method of controlling the acid balance in a high chloride heap leach process tomaximise the copper dissolution in a cure step and to increase overall copper recovery which include an agglomeration stage in which acid and process solutions are combined with the ore prior to stacking to form a heap followed by a cure phase to leach a portion of the copper in the ore in the heap followed by an irrigated leach phase in which the remaining copper minerals are leached and copper is recovered from a pregnant leach solution by a solvent extraction step followed by an electrowinning step wherein the acid concentration in the pregnant leach solution which reports to the solvent extraction step is less than 10 g/L to allow effective copper recovery from the pregnant leach solution in the solvent extraction step.

Abstract: The method may comprise receiving historical data (e.g., mineralogy data, irrigation data, raffinate data, heat data, lift height data, geographic data on ore placement and/or blower data); training a predictive model using the historical data to create a trained predictive model; adding future assumption data to the trained predictive model; running the forecast engine for a plurality of parameters to obtain forecast data for a mining production target; comparing the forecast data for the mining production target to the actual data for the mining production target; determining deviations between the forecast data and the actual data, based on the comparing; and changing each of the plurality of parameters from the forecast data to the actual data to determine a contribution to the deviations for each of the plurality of parameters.

Abstract: The present invention relates an indicator system for assessing a reduction state of unconsolidated material that includes a delivery tube defining an interior chamber, and a substrate disposed within the interior chamber and including a reactive coating thereon. The reactive coating is at least partially removable from the substrate upon exposure to a reducing condition of unconsolidated material over a period of time. An indicator device including a reactive coating comprising a manganese oxide is also disclosed.

Abstract: An integrated two-phase anaerobic dry fermentation reactor based on a biomimetic principle of rumen includes a reactor body; wherein the reactor body includes a dry fermentation chamber, a secondary fermentation chamber, and a liquid storage chamber. The dry fermentation chamber is arranged at an upper portion of the reactor body. The liquid storage chamber is arranged at a bottom of the reactor body. The secondary fermentation chamber is arranged between the dry fermentation chamber and the liquid storage chamber in the reactor body. The dry fermentation chamber is connected to the secondary fermentation chamber by a porous structure.

Abstract: An integrated pressure leaching, heap leaching process for recovering copper from sulphidic feed containing iron, arsenic, and copper. Aqueous feed slurry of the sulphidic feed is pressure oxidized to form a liquid phase containing free sulphuric acid and aqueous copper sulphate, and to precipitate arsenic as solid iron arsenic compounds. Treated slurry is withdrawn from the pressure vessel and the liquid phase is separated from the solids. Copper is recovered from the separated liquid phase and generates a solution enriched in acid and depleted in copper. At least a portion of this solution is neutralized in a copper heap leach to produce a PLS containing copper and reduced in acid. At least a portion of the heap leach PLS is neutralized to produce a solution further reduced in acid, and solids containing copper precipitates, followed by a liquid solid separation.

Abstract: The present invention relates to a method for recovering metals using an adsorbent, which comprises preparing a leachate comprising metal ions and cyanides, wherein the metal ions comprise gold ions and copper ions; and in a state where the leachate has a cyanide (CN) concentration of 0.1 ppm or greater, adding to the leachate an adsorbent, which has an open circuit potential value between the open circuit potential value of the gold ions and that of the copper ions; and selectively adsorbing the copper ions to the adsorbent.

Abstract: The present disclosure provides system and method embodiments for extracting and separating rare earth elements (REEs) from various starting materials and sources. The system and method embodiments disclosed herein facilitate efficient REE extraction, separation, and/or isolation, even when the REEs are present in a starting material at a relatively low level compared to undesirable metals co-present in the starting material. In at least some examples, the disclosed system and method embodiments may be used to recover one or more REEs from coal derived acid mine drainage.

Abstract: A method for treating fluorine-containing rare earth mineral particles may include mixing a first batch of the fluorine-containing rare earth mineral particles with a first sulfuric acid solution in a weight ratio in the range of 2-10:1 of the sulfuric acid in the first sulfuric acid solution to the first batch of fluorine-containing rare earth mineral particles, and heating the mixture to cause a liquid-solid reaction. The solid phase and liquid phase may be separated after the reaction to obtain an acid filtrate and an acid residue. The acid residue may be leached with water to obtain an aqueous leaching liquor that comprises a rare earth sulfate and an aqueous leaching residue. A second sulfuric acid solution may be added to the acid filtrate in an amount such that the sulfuric acid concentration of the acid filtrate is 40-85 wt %.

Abstract: A process disclosed herein is related to the isolation and purification of substantially pure chemicals, including silica gel, sodium silicate, aluminum silicate, iron oxide, and rare earth elements (or rare earth metals, REEs), from massive industrial waste coal ash. In one embodiment, the process includes a plurality of caustic extractions of coal ash at an elevated temperature, followed by an acidic treatment to dissolve aluminum silicate and REEs. The dissolved aluminum silicate is precipitated out by pH adjustment as a solid product while REEs remain in the solution. REEs are captured and enriched using an ion exchange column. Alternatively, the solution containing aluminum silicate and REEs is heated to produce silica gel, which is easily separated from the enriched REEs solution. REEs are then isolated and purified from the enriched solution to afford substantially pure individual REE by a ligand-assisted chromatography.

Abstract: Process for recovering one or both of copper and silver from a sulphidic feed containing iron, arsenic, copper and silver by pressure oxidizing an aqueous feed slurry of the sulphidic feed in a pressure vessel to form a liquid phase containing free sulphuric acid and aqueous copper sulphate, and to precipitate arsenic as solid iron arsenic compounds. The process includes operating the pressure vessel at a sufficiently low solids content to maintain a free acid level below 30 g/L in the liquid phase, and providing sufficient heat to maintain a temperature in the pressure vessel above 200° C. Copper metal is recovered from the liquid phase and/or silver may be recovered from the solids by cyanide leaching without the need for a jarosite destruction step.

Abstract: Recovery of scandium from mined red mud includes adding an acid to a quantity of red mud for converting oxides in the red mud, and roasting the quantity of red mud for decomposing compounds having low thermal stability, typically iron and titanium. Water is added to the roasted red mud for leaching the converted oxides into a leach liquor mixture including scandium and other dissolved rare earths, and the leach liquor mixture is agitated by sonication or ball milling to increase an exposed surface area of red mud particles in the leach liquor. PH of the leach liquor is adjusted to precipitate the rare earths while leaving the scandium in solution in the leach liquor, followed by precipitating the separated scandium oxalate remaining in the leach liquor by reducing the pH and adding oxalic acid. Precipitated scandium oxalate may then be filtered from the leach liquor.

Abstract: 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.

Abstract: A method is provided for separating mixtures of different rare earth metals using a ligand having a size-sensitive molecular aperture. The present invention meets the needs in the field by providing method of separating and purifying rare earth metals. The object of this invention is to separate and purify rare earth metals, e.g., the more valuable Dy away from Nd, in mixtures containing such metals using a simple chemical process without the need for countercurrent liquid-liquid separations.

Abstract: A method of leaching copper from a copper sulfide ore which includes adding a potential adjustment agent for lowering a potential of a leaching solution obtained after leaching copper from the copper sulfide ore by using iodide ion and iron (III) ion, the leaching solution being stored in a tank for storing the leaching solution.

Abstract: A process of extracting copper from copper sulphide minerals which is enhanced at solution potentials exceeding 700 mV SHE, in the absence of any microorganism, by contacting the minerals in a pre-treatment phase using an acid solution at a high chloride content containing dissolved copper.

Abstract: A hydrostatic tower whose lower part communicates with a liquid phase space within a flash vessel, and whose upper part communicates with a gas phase space within the flash vessel is provided. A rising liquid level within the hydrostatic tower is detected by at least one maximum liquid level sensor provided at a position at the same level as a predetermined maximum liquid level within the liquid phase space. A dropping liquid level within the hydrostatic tower is detected by at least one minimum liquid level sensor provided at a position at the same level as a predetermined minimum liquid level within the liquid phase space.

Abstract: Provided is a method for producing cobalt sulfate, wherein, on the occasion of separating an acidic solution containing calcium, magnesium and sodium as impurities from a cobalt chloride solution by solvent extraction, when a diluent is added to the extractant to be used to dilute the extractant by 10% to 30% by volume; in Step 1, the operational pH is maintained in the range of 4.0 to 5.0 and the liquid volume ratio of organic phase/liquid phase is maintained in the range of 5.0 to 7.0; in Step 2, the operational pH is maintained in the range of 4.0 to 4.5 and the liquid volume ratio of organic phase/liquid phase is maintained in the range of 5.0 to 10.0; and in Step 3, the pH is maintained in the range of 0.5 to 1.0.

Abstract: A method for leaching molybdenum and/or rhenium from a sulfide ore and/or concentrate containing such, the method comprising the steps of: Exposing the ore and/or concentrate to an aqueous solution of chlorine-based oxidizing species in which the sum of the concentrations of hypochlorite and hypochlorous acid is at least 10 mol % of the chlorine-based oxidizing species; Allowing and/or facilitating the oxidation of the molybdenum and/or rhenium by the hypochlorite and/or hypochlorous acid, thereby decreasing the pH such that the predominant chlorine-based oxidizing species becomes chlorine; Allowing and/or facilitating the oxidation of the molybdenum and/or rhenium by the chlorine thereby producing a pregnant leach solution; and Passing the pregnant leach solution to a means for metal recovery.

Abstract: The invention provides a recycling step in an oxidative pressure leaching process for recovery of metals using halide ions, in which a portion of the leached solids are recycled back to the feed to the autoclave, to allow two or more passes through the high temperature leaching step.

Abstract: Disclosed is a method of recovering a rare earth element from oxidized scrap of permanent magnet. The method includes leaching an oxidized scrap of a permanent magnet from a sulfuric acid solution, and recovering the rare earth element after precipitating the rare earth element contained in the oxidized scrap of the permanent magnet by adding sodium sulfate into the sulfuric acid solution.

Abstract: The invention is directed to a process and apparatus for recovering metals from bottom ash from incineration plants, such as municipal waste incineration plants. The process includes directing a feed containing ash into an oxidizing unit, wherein at least part of the metals is oxidized in the presence of one or more acids and at least one oxygen donor, thus producing a stream comprising metal ions. From this stream the metals of interest are selected and converted into metallic form.

Abstract: The present invention aims at improving a recovery rate of a positive-pole active substance and preventing a recovery loss of valuable metals when a positive-pole active substance is separated from a lithium ion battery. In the present invention, a material resulting from battery dismantling obtained by dismantling a lithium ion battery is stirred using a surfactant solution, whereby a positive-pole active substance is separated from a positive-electrode substrate. Also, it is preferable that an alkaline solution is added to a positive-electrode material of a material resulting from battery dismantling, thereby dissolving a positive-electrode substrate to which a positive-pole active substance adheres to obtain a slurry containing the positive-pole active substance, and a surfactant solution is added to the slurry to disperse the positive-pole active substance in the slurry, whereby the positive-pole active substance is separated from the alkaline solution.

Abstract: The present invention relates to a process for recovering non-ferrous metals from a solid matrix comprising the following phases: (a) leaching the solid matrix with an aqueous-based solution containing chloride ions and ammonium ions and having a pH within the range of 6.5-8.5, in the presence of oxygen, at a temperature ranging from 100° C. to 160° C. and a pressure within the range of 150 kPa-800 kPa, so as to obtain an extraction solution comprising the leached metals and a solid leaching residue; (b) separating said solid leaching residue from said extraction solution; (c) subjecting said extraction solution to at least one cementation so as to recover the metals in the elemental state.

Abstract: A method allowing production of high-purity perrhenic acid from rhenium sulfide by applying pyrometallurgical process is provided.

Abstract: A method for leaching copper and molybdenum from an ore, residue and/or concentrate containing such, in which more than 1% w/w of the total molybdenum is present as a sulfide and in which more than 1% w/w of the total copper is present as an oxide, the method comprising the steps of: exposing the ore, residue and/or concentrate to an aqueous solution of chlorine (I)-based oxidizing species of a pH of at least 3.0; oxidizing the molybdenum by the chlorine-based oxidizing species thereby providing a treated ore, residue and/or concentrate and a reduced aqueous solution of chlorine-based oxidizing species; leaching the treated ore, residue and/or concentrate by exposing the treated ore, residue and/or concentrate to an aqueous ammoniacal ammonium carbonate solution to form a pregnant leach solution containing both copper and molybdenum; and passing the pregnant leach solution containing both copper and molybdenum to a means for metal recovery.

Abstract: A method for recovering nickel and cobalt from a product liquor solution by processing the product liquor solution through a continuous ion exchange process including a plurality of ion exchange beds containing nickel selective ion exchange resin that pass through individual process zones as part of a nickel recovery circuit, wherein the method includes the following steps: (a) passing the product liquor solution through an ion exchange bed to load nickel onto the ion exchange resin and produce a cobalt-containing raffinate solution, (b) passing a sulfuric acid solution through the loaded ion exchange bed to strip nickel from the exchange resin and produce a nickel-containing eluate, (c) passing a rinse solution through the stripped ion exchange bed, (d) adjusting the pH of the cobalt-containing raffinate solution to a pH of at least 2.

Abstract: Disclosed are methods and compositions for improving metal extraction processes by introducing at least one cationically charged compound selected from a group consisting of amines, particularly quaternary amines such as alkyldimethylbenzylammonium chlorides (ADBAC compounds), polyamines and other suitable cationic organic materials, and mixtures thereof, for neutralizing and/or coagulating excess anionic organic compounds including, for example, flotation reagents, surfactants, polymers, flotation reagent by-products and/or anti-scalant additives found in metal concentrate streams, and thereby reduce the downstream fouling of the activated carbon by these compounds.

Abstract: Provided is a method of leaching copper ore which contains chalcopyrite, the method includes a first leaching stage based on an oxidative leaching reaction of copper by iron (III) ion, and a second leaching stage, in succession to the first leaching stage, using a solution containing iodide ion and iron (III) ion.

Abstract: Provided is a valuable-metal recovery method for recovering metals from lithium ion batteries using comparatively simple equipment and without using a cumbersome process. In said method, a positive electrode material from lithium ion batteries, containing lithium and a transition metal, is dissolved in an acidic solution, thereby generating lithium ions and ions of the transition metal in the acidic solution. Said acidic solution and a recovery liquid are then made to flow with an anion-permeable membrane interposed therebetween, causing the lithium ions to permeate from the acidic solution to recovery solution. Lithium ions are then recovered from the recovery liquid containing dissolved lithium ions.

Abstract: This invention relates to a process for preparing a ferric nitrate (Fe(NO3)3) reagent, capable of serving as a solvent and copper species oxidizing agent in the ore curing, heap leaching, and/or run of mine (ROM) leaching of a copper ore hydrometallurgical process located at a brown field or green field, from an aqueous copper raffinate solution from the copper ore hydrometallurgical process of copper ore containing iron (II) (Fe2+), and the reagent prepared pursuant to this process.

Abstract: A method for recovering rare earth compounds, vanadium and nickel from waste vanadium-nickel catalysts, comprising steps of: acid leaching, by soaking waste vanadium-nickel catalysts into a sulfuric acid solution and obtaining a mixture containing alumina silica slag; sedimentation, by filtering out the alumina silica slag from the mixture to obtain a filtrate, and then adding a salt into the filtrate to precipitate rare earth double salts followed by isolating a sediment of rare earth double salts and a liquid solution via filtration; and extraction, by providing and adding an alkali into the sediment of rare earth double salts followed by further soaking the rare earth double salts in an acid solution to precipitate rare earth oxalate or rare earth carbonate, and adding an oxidizer into the liquid solution to adjust the pH value thereof and then extracting vanadium and nickel from the liquid solution via an ion-exchange resin.

Abstract: A method of heap leaching including forming a heap lift, installing a horizontal solution collection system between the heap layers including a horizontal tubing with a wireline data collection tool disposed therein, providing a heap leach model for modeling the heap leach operation including a solvent formulation and a irrigation setting, obtaining collected data from the wireline data collection tool while irrigating the heap lift, the collected data including in-situ material parameters of the heap layers and in-situ solution parameters of the solution flowing in the heap layers, modeling the heap leach operation using the collected data based on the heap leach model to generate a result, and adjusting the heap leach operation based on the result.

Abstract: There are provided processes for treating fly ash. For example, the processes can comprise leaching fly ash with HCl so as to obtain a leachate comprising aluminum ions and a solid, and separating the solid from the leachate; reacting the leachate with HCl so as to obtain a liquid and a precipitate comprising the aluminum ions in the form of AlCl3, and separating the precipitate from the liquid; and heating the precipitate under conditions effective for converting AlCl3 into Al2O3 and optionally recovering gaseous HCl so-produced.

Abstract: A method for extracting and separating a rare-earth element. Cations and anions in a quaternary ammonium ionic liquid extractant, that is, 2-ethylhexyl phosphate mono-2-ethylhexyl acrylate trialkyl methyl ammonium and phosphate di(2-ethylhexyl) phthalate trialkyl methyl ammonium, react with rare-earth ions to form neutral complex molecules, also, a collaborative effect and a competitive effect are present between the cations and the anions in the quaternary ammonium ionic liquid extractant in a rare-earth element extraction process, the separation factor for the rare-earth element is thus increased. The method for extracting and separating the rare-earth element provides good interfacial phenomena in the extraction process, does not generate emulsification, obviates the need for extractant saponification, and provides increased separation factor for rare-earth elements, and particularly increased separation factor for heavy rare-earth elements.

Abstract: A method of recovering copper from a copper sulfide concentrate comprising a copper arsenic sulfosalt or a copper antimony sulfosalt, using carbon as a catalyst. The concentrate and carbon are added to an acidic sulfate leach solution. The copper is leached from the concentrate, in the presence of an oxygen-containing gas. The operating potential is maintained above a selected level. The carbon copper sulfide ratio of the carbon being added to the copper sulfide present in the concentrate being added is at least 1:20. The carbon may be maintained above a selected concentration in the leach solution. The leached copper is recovered from the solution by conventional methods.

Abstract: Valuable metals such as cobalt, nickel, manganese, and lithium can be economically recovered from various lithium secondary battery-related wastes by the inventive method which comprises liquid-phase leaching a scrap powder containing Co, Ni, Mn, and Li, and purifying and solvent-extracting the resulting leaching solution to recover each of said Co, Ni, Mn, and Li, wherein the liquid-phase leaching is performed by a two-step counter-current leaching using an inorganic acid solution or a mixed solution of an inorganic acid and hydrogen peroxide.

Abstract: A biomining enhancement method for metal sulfide ores using sulfurous acid for microbial leaching of heavy metals into solution for subsequent removal via electro winning, ion exchange, or precipitation with alkaline and nutrient reagents for filtration removal.

Abstract: A process for the production of a high grade nickel product including the steps of: a) providing at least one heap of a nickeliferous lateritic ore and leaching that heap with a suitable lixiviant, preferably sulfuric acid solution, to produce a nickel rich pregnant leach solution (PLS); b) subjecting the PLS to an impurity removal step to precipitate ferric iron, and preferably partially precipitate aluminium and chromium as hydroxides; and c) recovering a high grade nickel product from the PLS preferably by either nickel ion exchange, solvent extraction, electrowinning, conventional multi-stage neutralization, pyrohydrolysis or sulfidation.

Abstract: The present disclosure relates to processes for recovering rare earth elements from various materials. The processes can comprise leaching the at least one material with at least one acid so as to obtain a leachate comprising at least one metal ion and at least one rare earth element, and a solid, and separating the leachate from the solid. The processes can also comprise substantially selectively removing at least one of the at least one metal ion from the leachate and optionally obtaining a precipitate. The processes can also comprise substantially selectively removing the at least one rare earth element from the leachate and/or the precipitate.

Abstract: Disclosed is a method of recovering gold from an aqueous solution having a gold concentration of 10 mg/L or lower, using a plurality of extraction apparatuses for bringing the aqueous solution into contact with an extraction agent, arranged to configure a multi-stage extraction process, the method allowing the aqueous solution to continuously flow from the first-stage extraction process to the next-stage extraction process, while recycling the extraction medium used in each stage twice or more times for the extraction process of the same stage, without back extraction and reduction.

Abstract: The present invention provides a method of leaching copper from a copper sulfide ore, wherein operating costs and environmental impacts can be effectively reduced. The present invention is a method of leaching copper from a copper sulfide ore by a process of leaching a layer of stacked ores, wherein the leaching solution containing Fe (III) ion and other leaching solution containing iodide ion are fed through routes independent of each other to a layer of stacked ores containing a copper sulfide ore.

Abstract: The present invention relates to a process for the recovery of cobalt comprising: (i) providing a high tenor cobalt solution wherein the high tenor cobalt solution comprises cobalt and nickel; (ii) contacting the high tenor cobalt solution with an N-(2-hydroxypropyl)picolylamine resin to load the N-(2-hydroxypropyl)picolylamine resin with cobalt and nickel; (iii) eluting the cobalt from the loaded N-(2-hydroxypropyl)picolylamine resin; and (iv) eluting the nickel from the loaded N-(2-hydroxypropyl)picolylamine resin.

Abstract: A method for separating nickel, cobalt and a rare earth element from a material containing positive and negative electrode active materials of a nickel-metal hydride battery includes mixing a material containing positive and negative electrode active materials with a sulfuric acid solution and dissolving therein, and then separating a leachate from a residue; adding an alkali metal sulfate to the leachate to obtain a mixed precipitate of double sulfate of rare earth elements, and a rare-earth-element-free solution; and adding a sulfurizing agent to the rare-earth-element-free solution to separate a nickel and cobalt sulfide raw material and a residual solution.

Abstract: A process for producing a ferric containing solution by the controlled oxidation of a ferrous containing solution, said process including providing a solution containing at least ferrous ions; treating the solution with one or more inlet gases containing sulfur dioxide and oxygen in order to oxidize said ferrous ions to ferric ions, wherein the delivery rate of the sulfur dioxide gas is oxidation rate limiting; and controlling the concentration of dissolved oxygen in said solution at an optimum value.

Abstract: A method for leaching a sulfidic metal concentrate in hydrometallurgical production of metal in a leaching process from which hot water vapor containing off-gas is conducted out and to which an acid solution warmed up to an elevated temperature is conducted. The acid solution is warmed up to an elevated temperature by bringing off-gas of the leaching step into direct contact with the acid solution.

Abstract: Methods for recovering gold from gold-bearing materials are provided. The methods rely upon on the self-assembly of KAuBr4 and ?-cyclodextrin (?-CD) in aqueous solution to form a co-precipitate, a 1:2 complex, KAuBr4•(?-CD)2 (“?•Br”), either alone or in an extended {[K(OH2)6][AuBr4]?(?-CD)2}n chain superstructure (FIG. 1). The co-precipitation of ?•Br is selective for gold, even in the presence of other metals, including other square-planar noble metals. The method enables one to isolate gold from gold-bearing materials from diverse sources, as further described.

Abstract: A method for producing an iron (III) ion from the acidic solution containing an iodide ion and an iron (II) ion efficiently and stably is provided. The method including performing the following steps (a)-(b), repeatedly and continuously: (a) a step wherein the iron (II) ion in the acidic solution containing the iodide ion and the iron (II) ion is oxidized into iron (III) ion in a reactor using a microbes immobilizing carrier to which iron oxidizing microbes attached; (b) a step wherein sedimentation of the solution obtained in the step (a) is performed in a sedimentation tank to obtain the solution containing the iron (III) ion and concurrently the sediment of the microbes immobilizing carrier to which the iron oxidizing microbes have attached is recovered and then reintroduced into the reactor in the step (a).

Abstract: Provided is a method of recovering rare-earth elements, including causing rare-earth elements particularly including Nd and Dy to leach efficiently from a raw material for leaching which contains the rare-earth elements, and separating and recovering the rare-earth elements.