Analysis of current status of precious metal extraction and refining technology

Precious metals mainly refer to eight metal elements including gold, silver and platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, platinum). Most of these metals have beautiful colors, are quite resistant to chemicals, and are not prone to chemical reactions under normal conditions. Materials containing precious metals are divided into two categories: one is mineral resources, called primary resources; the other is renewable resources, which are precious metal products that are scrapped during use. These resources are of various types and shapes, ranging from a few ten thousandths. to almost pure metals, called secondary resources. The smelting technology of precious metals has made significant progress in recent years. The effective extraction of precious metals is divided into three parts: enrichment-separation-refining. Industrial applications of solvent extraction techniques are commonly used to extract precious metals from solutions containing polymetallic components. In recent years, there have been continuous innovations and developments in extraction and separation processes and extraction equipment. The existing precious metal extraction equipment has the disadvantages of being unable to perform multiple extractions, slow extraction speed, and poor extraction effect. The extraction equipment also consists of traditional mixing and clarification methods. The tank was developed into the modern CWL-M new centrifugal extractor. The equipment has good energy saving effect and low power consumption. In terms of corrosion resistance, for highly corrosive systems, polymer composite materials are used instead of traditional metal materials to solve the corrosion problem of the equipment. In terms of stable performance, it adopts a top-suspension structure, eliminates the bearings and mechanical seals at the bottom of the equipment, simplifies the equipment structure, and fundamentally solves the problems of easy leakage, frequent mechanical failures, and short service life of traditional centrifugal extractors. The equipment adopts a variety of mixing structures, with good separation effect and small liquid holding capacity. Due to the strong continuity of process operations and high degree of automation, the cycle is greatly shortened, the recovery rate and product purity are improved, and great technical and economic benefits are obtained. It has become an important equipment and method for the separation and refining of precious metals.

The traditional process of smelting precious metals gold, platinum and palladium is repeated melting and crystallization and repeated reduction and purification. The new extraction process is used to extract gold, platinum and palladium. The gold, platinum and palladium ore is first chlorinated with aqueous solution to melt the platinum and palladium gold ore. After dissolution, it is reduced with reduced sulfur dioxide or sodium sulfate to control the reduction potential (increase the potential to control mol degree) to reduce the gold and make it into coarse gold powder, which is used to refine gold. The remaining liquid contains other metals such as platinum, palladium, zinc, and bismuth. These metals are made in the form of ammonium. Ammonium chloride is added, and the palladium is added. In the liquid phase, the platinum reaches the solid phase, which forms a rough separation of platinum and palladium. After that, the aqueous solution is chlorinated and dissolved into a liquid, and the palladium is extracted with targeted extraction. After extraction, the organic phase is loaded and the impurities are washed with hydrochloric acid and then back-extracted with pure water or sodium hydroxide. The raffinate after the palladium extraction is adjusted and extracted with N235. Platinum, this extraction agent has a high extraction rate of platinum (99.95%) and a very low extraction rate of base metals such as copper, iron, nickel, and cobalt. It has a novel process, good front-to-back connection, and wide adaptability. Use p204 to extract the base metal from the platinum raffinate. In the rhodium-iridium solution extracted from gold, palladium and platinum, precipitate it with ammonium chloride for chemical industry, burn it into platinum powder and smelt it into platinum ingots.

The extraction of metal ions from precious metal solutions is related to their valence configuration and the properties of the solution. Many extraction mechanism and extraction process research results show that the valence and state of the chloride anion in the solution are dominated by the central ion and the properties of the solution, and its changes lead to Significant changes in extraction behavior.