Wet process for recovering platinum group metals from waste catalysts

The recovery technology of waste catalysts containing platinum group metals can be divided into two categories: pyrometallurgy and wet process. Pyrometallurgy includes smelting enrichment method, chlorination volatilization method and incineration method. The commercially applied smelting enrichment method involves the formation of alloys of platinum group metals and collectors (lead, copper, iron and arsenic, etc.) in an ion furnace, but the silicon-iron alloy formed by it has extremely strong acid resistance. When the slag and alloy are separated during repeated dissolution and refining at high temperature, platinum group metals are inevitably lost.

The chlorination volatilization method selectively converts platinum group metals into volatile chlorides under high temperature conditions (600~1200°C), which are enriched and separated after condensation and adsorption on activated carbon bed. The required temperature is relatively high, and chlorine is highly corrosive. These problems prevent its commercial application.

The incineration method collects ash after destroying the carbon-based carrier to achieve PGMs recovery. It is suitable for waste catalysts loaded with a single carbonaceous carrier, and it is necessary to consider the use of additives to increase the incineration rate and the environmental pollution of black smoke.

Compared with the pyrometallurgical process, the wet process has the advantages of low investment cost, low temperature and high recovery rate, and is suitable for small-scale applications. These advantages have promoted the development of hydrometallurgical recovery processes for precious metals.”