A plurality of different metals, including precious metals, platinum group metals, rare earth elements, alkaline earth metals, etc., can be electrochemically recovered from waste materials such as ashes and e-waste, e.g., printed circuit boards. Waste feed stocks are treated with supercritical CO.sub.2 (scCO.sub.2) and acid to produce a solid delaminated waste and a liquid delaminated waste for recovery of elemental metals and metal compounds from each. Carbonation reactions can be used to convert and recover alkaline earth metals from the liquid delaminated waste. The solid delaminated waste can yield a solid gold product, and be further treated along with the liquid delaminated waste via a solvent including one or more organic ligands that bind target metals to form metal-ligand complexes. Electrochemical separation of the different metals, e.g., via stepwise variation of pH to release the metals from organic ligands having different pKa values, yields high purity metal product streams.

Recovery of noble metals (including the recovery of gold and/or silver from gold and/or silver containing material) is generally described. The gold and/or silver can be recovered selectively, in some cases, such that gold and/or silver are at least partially separated from non-silver and/or non-gold material. Gold and/or silver may be recovered from material using mixtures of acids, in some instances. In some cases, the mixture can comprise nitric acid and at least one supplemental acid, such as sulfuric acid, phosphoric acid, and/or a sulfonic acid. The amount of nitric acid within the mixture can be, in some instances, relatively small compared to the amount of sulfuric acid or phosphoric acid within the mixture. In some cases, the recovery of gold and/or silver using the acid mixtures can be enhanced by transporting an electric current between an electrode and the gold and/or silver of the material. In some cases, acid mixtures can be used to recover silver from particular types of materials, such as material comprising silver metal and cadmium oxide and/or material comprising silver metal and tungsten metal.

The present application provides a method for recovering metal from metal-containing material by leaching, the method comprising providing aqueous solution containing leaching agent precursor, providing one or more source(s) of external energy comprising a source of electric current connected to one or more non-metallic electrode(s) comprising carbon material(s) selected from graphite, graphene and derivatives thereof, and carbon nanomaterial(s) selected from carbon nanofibers, carbon nanotubes and carbon nanobuds, treating the aqueous solution with the external energy, which is electric current providing electrochemical reactions, to form hydrogen peroxide from oxygen in the aqueous solution, reacting the leaching agent precursor with the formed hydrogen peroxide to form a leaching agent and to obtain a leaching solution, providing metal-containing material, reacting the metal-containing material with the leaching solution to obtain soluble metal complexes, and recovering the soluble metal complexes. The present application also discloses a device for recovering metal from metal-containing material by leaching.

Materials and methods for precious metal recovery are disclosed. Usable leaching solutions are preferably aqueous based and include appropriate materials in sufficient quantities to solubilize and stabilize precious metal. Such materials typically include oxidant material. Some or all of the oxidant material can be, in some instances, generated in-situ. The leaching solution is typically contacted with a substrate having a target precious metal, thereby solubilizing precious metal to form a stable, pregnant solution. The precious metal can then be recovered from the pregnant solution. In some instances, components of the leaching solution can be regenerated and reused in subsequent leaching.

Disclosed herein are methods of using reactor outputs to purify materials. For example, methods of using acid and/or base produced in a reactor to purify materials (e.g., limestone, dolomite, waste streams, and/or ash) are described herein. Related systems are also described.

The invention relates to a process that allows electrolytic copper cathodes to be produced, using the pregnant leach solution (PLS) directly in the electrowinning, avoiding the step of mineral concentration by solvent extraction. Furthermore, this process has a modular structure and the full process can be mobilised depending on the requirements of the process itself. The invention also relates to the system that operates with the previously described process.

An electrochemical system and process are provided to convert an amount of chalcopyrite (CuFeS.sub.2) to a product including copper ions. In an electrochemical reactor, a potential is applied across an anode and a cathode to convert the chalcopyrite to an intermediate, chalcocite (Cu.sub.2S). The anode is covered to prevent contact with the intermediate, thus limiting subsequent conversion of the intermediate to covellite (CuS) in favor of conversion to a material more suited to chemical oxidation, cuprite (Cu.sub.2O). For example, the anode can be covered with one or more layers of filter paper. Upon application of an oxidizing agent, the cuprite is oxidized to produce a product including copper ions. The cathode and covered anode allow for efficient and inexpensive processing. The cost of this technique is comparable to industry standards, and moreover, has a much smaller environmental footprint than heat-based copper extraction.

Disclosed herein is a method of recovering lithium or sodium from an active material of a lithium or sodium ion battery. In a preferred embodiment, the method comprises a redox-targeting reaction of a used active material LiFeP04 with a redox mediator [Fe(CN).sub.6].sup.3− in a tank to produce lithium ions, circulating the reacted redox solution into a cell to regenerate said redox mediator and enabling said lithium ions to migrate through a membrane towards a cathode wherein said lithium ions are captured as LiOH through an electrochemical reaction.

A process for multi-recycling, low-energy and high-purity extraction of lithium increases the purity and the concentration of lithium ions in produced solutions gradually through steps of adsorption/desorption ion exchange, extraction, impurity separation, agent separation and concentration, during which extractive liquids are returned, recycled and processed in previous steps for fewer dosages of chemicals and fewest discharged effluents, lower manufacturing costs than existing techniques, low specific energy consumption and consumable loss, and high-purity products with lithium ions.

A process for recovering gold from a refractory gold ore, comprising the steps of: electrolyzing a mixture consisting of the ore particles and an aqueous bromide solution in an electrolytic cell having anode and cathode, wherein bromine is produced at the anode by oxidation of the bromide, thereby dissolving gold in the aqueous phase; separating the ore particles from the aqueous phase to obtain a leach liquor; adjusting the pH of the leach liquor to the alkaline range to produce a gold-containing precipitate; collecting the gold-containing precipitate and recycling a bromide-containing barren solution for reuse as an aqueous bromide feed solution.