Process for enhanced metal recovery from, for example, metal-containing feedstock using liquid and/or supercritical fluid carbon dioxide and a source of oxidation. The oxidation agent can be free of complexing agent. The metal-containing feedstock can be a mineral such as a refractory mineral. The mineral can be an ore with high sulfide content or an ore rich in carbonaceous material. Waste can also be used as the metal-containing feedstock. The metal-containing feedstock can be used which is not subjected to ultrafine grinding. Relatively low temperatures and pressures can be used. The metal-containing feedstock can be fed into the reactor at a temperature below the critical temperature of the carbon dioxide, and an exotherm from the oxidation reaction can provide the supercritical temperature. The oxidant can be added to the reactor at a rate to maintain isothermal conditions in the reactor. Minimal amounts of water can be used as an extractive medium.

A process (10) for the production of lithium hydroxide, the process comprising the steps of: (i) Causticising lithium chloride (12) with sodium hydroxide (16) to produce a lithium hydroxide product; (ii) Collecting the solids resulting from the causticisation of step (i) and filtering (22) same; (iii) The filtered solids from step (ii) are passed to a heating step (32) in which anhydrous lithium hydroxide is produced; (iv) Filtering (34) the anhydrous lithium hydroxide product of step (iii); and (v) Quenching the anhydrous lithium hydroxide of step (iv) with water to produce lithium hydroxide monohydrate crystals.

A process (10) for the production of lithium hydroxide, the process comprising the steps of: (i) Causticising lithium chloride (12) with sodium hydroxide (16) to produce a lithium hydroxide product; (ii) Collecting the solids resulting from the causticisation of step (i) and filtering (22) same; (iii) The filtered solids from step (ii) are passed to a heating step (32) in which anhydrous lithium hydroxide is produced; (iv) Filtering (34) the anhydrous lithium hydroxide product of step (iii); and (v) Quenching the anhydrous lithium hydroxide of step (iv) with water to produce lithium hydroxide monohydrate crystals.

Systems and methods for recovering neodymium and other related rare earth elements from permanent magnets and/or various ore compositions are presented herein. In one embodiment, a method of recovering a rare earth element (REE) from a permanent magnet material and/or a mined ore composition (collectively “work material”) is presented. The method includes converting the work material to a higher surface area form, treating the converted work material with an aqueous solution of alkaline carbonates to dissolve the REE, filtering the treated and converted work material to yield a filtrate, and treating the filtrate with at least one of a precipitating agent or a precipitating condition to form REE solids. The aqueous solution of alkaline carbonates comprises at least one of potassium carbonate, potassium bicarbonate, or dissolved carbon dioxide.

Systems and methods for recovering neodymium and other related rare earth elements from permanent magnets and/or various ore compositions are presented herein. In one embodiment, a method of recovering a rare earth element (REE) from a permanent magnet material and/or a mined ore composition (collectively “work material”) is presented. The method includes converting the work material to a higher surface area form, treating the converted work material with an aqueous solution of alkaline carbonates to dissolve the REE, filtering the treated and converted work material to yield a filtrate, and treating the filtrate with at least one of a precipitating agent or a precipitating condition to form REE solids. The aqueous solution of alkaline carbonates comprises at least one of potassium carbonate, potassium bicarbonate, or dissolved carbon dioxide.

Process for gold and/or platinum group metals heap leaching comprising irrigating a heap with an irrigation solution containing sodium cyanide for leaching gold and/or platinum group metals from a gold and/or platinum group metals containing ore. A lime reagent is added by feeding a fine particle lime suspension containing lime particles in an aqueous phase in an irrigation solution.

A system for recovering rare earth elements from coal ash includes a leaching reactor, an ash dryer downstream of the leaching reactor, and a roaster downstream of the ash dryer that is cooperatively connected to both the leaching reactor and the ash dryer. Coal ash is mixed with an acid stream such that rare earth elements present in the coal ash are dissolved in the acid stream, thereby creating (i) a leachate containing the rare earth elements and (ii) leached ash. The leachate is heated to obtain acid vapor and an acid-soluble rare earth concentrate. Mixing of the coal ash with the acid stream can occur in a leaching reactor and heating of the leachate can occur in a roaster. The acid-soluble rare earth concentrate can be fed to a hydrometallurgical process to separate and purify the rare earth elements.

A system for recovering rare earth elements from coal ash includes a leaching reactor, an ash dryer downstream of the leaching reactor, and a roaster downstream of the ash dryer that is cooperatively connected to both the leaching reactor and the ash dryer. Coal ash is mixed with an acid stream such that rare earth elements present in the coal ash are dissolved in the acid stream, thereby creating (i) a leachate containing the rare earth elements and (ii) leached ash. The leachate is heated to obtain acid vapor and an acid-soluble rare earth concentrate. Mixing of the coal ash with the acid stream can occur in a leaching reactor and heating of the leachate can occur in a roaster. The acid-soluble rare earth concentrate can be fed to a hydrometallurgical process to separate and purify the rare earth elements.

A tungsten recovery method including leaching tungsten while suppressing leaching of silicon by using a weak alkali compound with respect to a tungsten raw material containing silicon with tungsten oxide, separating most of the silicon as a residue during the leaching of the tungsten, and recovering a tungsten leachate having an extremely low silicon concentration.

A tungsten recovery method including leaching tungsten while suppressing leaching of silicon by using a weak alkali compound with respect to a tungsten raw material containing silicon with tungsten oxide, separating most of the silicon as a residue during the leaching of the tungsten, and recovering a tungsten leachate having an extremely low silicon concentration.