Development status of precious metal extraction process and equipment

Precious metals mainly refer to metal elements such as gold, silver, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, platinum). Most of these metals are beautiful in color and lustre, are resistant to chemicals, and generally do not cause chemical reactions. Materials containing precious metals are roughly divided into two categories: the first category is mineral resources, that is, primary resources; the other category is renewable resources, which mainly exist in precious metal products scrapped during use. From a few ten thousandths to almost pure metal, it is a secondary resource. This paper summarizes the development status of precious metal extraction technology and equipment according to the characteristics of precious metals and other resources.

Precious Metal Refining Machine Craft Diagram

In recent years, the smelting technology of precious metals has been continuously improved. In the industrial production process, the traditional process of extracting precious metals gold, platinum and palladium is repeated melting crystallization and repeated reduction and purification, but the operation is complicated and the extraction efficiency is low. The new extraction process is divided into three parts: enrichment-separation-refining. Dissolve gold, platinum and palladium ore by chlorination method in aqueous solution, reduce with sulfur dioxide or sodium sulfate after dissolving, control the reduction potential (increase the potential to control the molarity) to reduce the gold, make coarse gold powder, and use it to smelt gold. The platinum, palladium, zinc, bismuth and other metal elements in the remaining liquid adopt the method of ammonium, add ammonium chloride, the palladium enters the liquid phase, and the platinum arrives in the solid phase to complete the rough separation of platinum and palladium. Then it is dissolved into a liquid with aqueous chlorination, and the palladium is extracted with a target. The loaded organic phase after extraction is washed with hydrochloric acid and then back-extracted with pure water or sodium hydroxide, and the raffinate after palladium extraction is adjusted to extract platinum with N235. The extraction agent has a high extraction rate of platinum (99.95%). , the extraction rate of base metals such as copper, iron, nickel and cobalt is very small. The raffinate after extraction of platinum is extracted with p204 for base metals, and the rhodium-iridium solution extracted by gold, palladium and platinum is precipitated with ammonium chloride, burned into platinum powder and smelted into platinum ingots.

Combined with the actual operation process, the extraction of metal ions from precious metal solutions is related to their valence configuration and the properties of the solution. The study of extraction mechanism and extraction process showed that the valence and state of chlorine complex anions in solution were dominated by central ions and solution properties, and their changes would lead to significant changes in extraction behavior.

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