In one aspect, the present disclosure pertains to methods of making various noble metal nanoprisms, e.g., gold nanoprisms. In various aspects, the methods can comprise incubating, under dark conditions, a growth solution comprising: (a) a plurality of gold seed structures; (b) a gold precursor, and (c) a photocatalytic intermediary, such that during the incubating step multiply-twinned gold seed structures in the growth solution are preferentially enlarged. The disclosed methods can comprise separating the multiply-twinned gold seed structures from the growth solution based upon the size of the gold seed structures to produce an enriched growth solution. In some aspects, the methods comprise irradiating the enriched growth solution to produce the gold nanoprisms. In some aspects, the disclosed nanoprisms comprise silver.

An environmentally friendly (e.g. no acid, base, or cyanide) system and process for large scale extraction of metal ion into aerobic molten salt (or ionic liquid) and the electrodeposition of metal (e.g. copper, gold, silver, etc.) from the metal ion dissolved in the molten salt. The non-volatile low vapor pressure liquid salt is reusable, and heat from the molten slag can heat the molten salts or ionic liquids. Another embodiment comprises a one-pot apparatus for the extraction of metal (e.g. copper) from metal earths and electrodepositing the metal using a low melting (209° C.) aerated Na—K—Zn chloride salt in which copper metal oxidizes and is converted to soluble copper chloride. When an electrical power supply is connected to the graphite vessel (cathode) and to copper rods in the melt (anodes), then the copper chloride is deposited as copper metal by electroreduction on the bottom of the graphite reaction vessel.

The present application relates to methods for leaching and extraction of precious metals. For example, the present application relates to methods of leaching gold, palladium and/or platinum from a substance comprising gold, palladium and/or platinum (such as a gold-containing ore or a platinum group metal (PGM) concentrate) using an organic solvent that is water-miscible or partially water-miscible.

A method, and systems in which such method may be practiced, allow for the separation of elemental metals from metal alloy. A metal alloy is atomized to form metal alloy particulates. The metal alloy particulates are exposed to an oxidizing agent, such as chlorine gas in the presence of a salt, such as NaCl, an acid, such as HCl, and water. The resulting solution may be filtered to remove particulates, reduced, filtered, reduced, filtered, and so on. In aspects, the method is used to refine gold alloy by oxidation of elemental sponge gold to gold chloride followed by reduction to pure elemental gold.

A method for extracting and enriching gold with a selenide includes: mixing an isocyanate and a selenium-containing compound of a formula of HO—R—Se—R—OH in a solvent to obtain a mixture system, where R is selected from linear or branched C.sub.2 to C.sub.11 alkylene groups; adding a tin-based catalyst into the mixture system to activate a reaction, drying the mixture system after the reaction, and obtaining a powdery selenium-containing polymer by grinding; immersing the selenium-containing polymer in an aqueous solution containing gold ions to allow gold to be extracted from the aqueous solution; and removing the selenium-containing polymer attached to a surface of extracted gold, thereby obtaining an extracted and enriched gold.

Liquid treatment apparatus comprises at least two chambers being first and second chambers through which a fluid can flow. The two chambers are separated by at least one choke nozzle which has an entrance in the first chamber and an exit in the second chamber. The choke nozzle comprises a converging section at its entrance, a throat section, a backward-facing step immediately after the throat section, and an exit section at its exit wherein the exit section diverges from the step. Similarly constructed mixing nozzles may be included in the apparatus. The apparatus is especially useful in processes requiring a gas to be entrained in a fluid so that the gas is in the form of very small bubbles that do not tend to coalesce and flash off such as in the dissolution of gold and other precious metals from ore and in the removal of arsenic from an ore.

The present disclosure broadly relates to a process for recovering gold and/or silver values from various feedstocks. More specifically, but not exclusively, the present disclosure relates to a process for the selective recovery of gold and/or silver values from a feedstock, the process comprising: leaching the feedstock in a sulfuric acid solution comprising thiourea while simultaneously sonicating the sulfuric acid solution thereby producing a pregnant solution; and selectively removing gold and/or silver compounds from the pregnant solution using a solvent extraction process or an ion exchange extraction process.

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

A process for the winning of at least one of gold, silver, and at least one platinum metal includes introducing at least one starting material containing at least one of gold, silver, and at least one platinum metal into an aqueous solution containing at least one nitrile, and producing hydroxyl radicals in the aqueous solution.

A process for reducing arsenic content from arsenic-bearing gold concentrate or other arsenic-bearing gold materials to produce a low arsenic-bearing gold concentrate. The process may comprise adding oxygen, water, and/or acid to an acidulated arsenic-bearing gold concentrate slurry and reacting them together in an autoclave at an elevated pressure and temperature in a pressure oxidation step. In one or more examples, the process may further comprise processing the oxidized concentrate slurry in an arsenic re-dissolution step to dissolve unstable solid arsenic compounds, and applying a first solid/liquid separation and wash step to form a first washed slurry/solid and first acid-containing solutions. The process may further comprise reacting the first washed slurry/solid with sulfur dioxide in a reductive leach step, and applying a second solid/liquid separation and wash step to form a second washed slurry/solid and second acid-containing solutions. The second washed slurry/solid may be a low arsenic-bearing gold concentrate.