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 preparing gold metal nanoparticles, e.g., nanospheres and nanoprisms, includes combining an extract of red algae with chloroauric acid (HAuCl.sub.4). The red algae can be Laurencia papillosa. The extract can include a water solvent extract. The chloroauric acid (HAuCl.sub.4) can be in an aqueous solution. The method can include providing chloroauric acid

(HAuCl.sub.4), providing a red algae extract, and combining the chloroauric acid (HAuCl.sub.4) and the red algae extract to produce gold nanoparticles.

A method and system are provided in which a gold and/or silver-collecting resin-in-leach circuit comprises both co-current and counter-current sections.

In an activated carbon for adsorbing a noble metal from an aqueous solution containing the noble metal, the difference (absolute value) between a zeta-potential in a 10 mmol/L aqueous solution of sodium tetraborate and a zeta-potential in a 0.01 mmol/L aqueous solution of sodium tetraborate is adjusted to not more than 18 mV and the pore volume of pores with a pore radius of not more than 1 nm is adjusted to 150 to 500 mm.sup.3/g. The activated carbon of the present invention may have a carbohydrate solution decolorizing performance of not less than 30%. The aqueous solution containing the noble metal may be a plating wastewater. According to the present invention, a noble metal can efficiently be adsorbed (or recovered) from a solution containing the noble metal.

The present invention provides a silver nano-particle production method which is safe and simple also in terms of scaled-up industrial-level production, in a so-called thermal decomposition method in which a silver-amine complex compound is thermally decomposed to form silver nano-particles. A method for producing silver nano-particles comprising: mixing an aliphatic hydrocarbon amine and a silver compound in the presence of an alcohol solvent having 3 or more carbon atoms to form a complex compound comprising the silver compound and the amine; and thermally decomposing the complex compound by heating to form silver nano-particles.

Provided is a process for recovery of gold from gold-bearing raw materials comprising (a) leaching said gold-bearing raw material in a chloride containing leaching solution containing a total concentration of less than 120 g/L of halide ions, whereby the total concentration of chloride ions is less than 120 g/L of to dissolve gold and to obtain a leach solution comprising gold in solution; and simultaneously contacting the leach solution comprising gold in solution with a re-sorptive material to obtain a leach solution comprising gold-bearing re-sorptive material; and (b) recovering gold and optionally silver from the said gold-bearing re-sorptive material.

Disclosed herein is a method for extracting precious metals from supported catalysts. The precious metal in one embodiment is rhodium. The supported catalyst may be from equipment, such as a used catalytic converter. The method is carried out at low temperature, and does not require harsh conditions, such as the use of a strong acid. The method involves contacting the catalytic material with a polar molecule and a reactive gas.

A process for the extraction of gold from a gold-bearing ore or concentrate, comprising the steps of leaching the gold-bearing ore or concentrate with a lixiviant of hydrochloric acid and magnesium chloride at atmospheric pressure at a temperature of at least 90° C. and an Eh of at least 900 mV. After a liquid/solids separation step, the solution obtained is subjected to an organic solvent extraction step using an oxime to obtain a solution of organic solvent containing gold, which is stripped with sodium thiosulphate to recover gold. The extraction may be operated to extract gold with or without iron. Materials used in the process may be recycled. The process avoids environmental and other hazards associated with the use of cyanide to extract gold.

A method for leaching one or more target metals from a sulfide ore and/or concentrate containing such, the method comprising the steps of: (a) Exposing the ore and/or concentrate to an aqueous solution of chlorine-based oxidising species in which the hypochlorous acid comprises at least 10 mol % of the chlorine-based oxidising species; (b) Allowing and/or facilitating the oxidation of the target metals by the hypochlorous acid, thereby decreasing the pH such that the predominant chlorine-based oxidising species becomes chlorine; (c) Allowing and/or facilitating the oxidation of the target metals by the chlorine; (d) Allowing and/or facilitating the dissolution of the target metals by the solution species formed during the oxidation by hypochlorous acid and/or chlorine; and (e) Passing the pregnant solution produced thereby to a means for metal recovery.

The present invention disclosed use of lactam as a solvent in the preparation of nanomaterials by precipitation method, sol-gel method or high temperature pyrolysis. These methods are able to recycle lactam solvent, which meet requirements of environmental protection.