Recent Developments on Processes for Recovery of Rhodium Metal from Spent Catalysts

Rhodium (Rh) catalyst has played an indispensable role in many important industrial and technological applications due to its unique valuable properties. Currently, Rh is considered as a strategic or critical metal the scarce high-quality purity can only be supplemented by refining coarse ores with low content (2–10 ppm) far from meeting fast-growing market demand. Nowadays, exploring new prospects already become urgent issue because of gradual depletion resources, incidental pressure on environmental protection, high prices. Since waste materials, equipment, electronic instruments contain higher concentration than that natural minerals, recovering scrap not offers additional source satisfy demand but also reduces risk ore over-exploitation. Therefore, recovery Rh-based catalysts great significance. This review provides overview spent catalysts. The characteristics, advantages disadvantages several current processes, including pyrometallurgy, hydrometallurgy, biosorption technology, are presented compared. Among them, hydrometallurgical process commonly used for auto simplicity, cost, short processing time, overall rate remnant within insoluble residue unstable leaching. In contrast, less effluent discharge ensured pyrometallurgical which therefore widely employed industry extract precious metals However, related procedure quite complex, leading expensive hardware investment, energy consumption, long cycles, inevitable difficulties controlling contamination practice. Compared conventional methods, cost-effective biological route owing intrinsic merits, e.g., operation costs, small volume, amount chemicals sludge treated. Finally, we summarize challenges prospect these three processes hope community gain more meaningful comprehensive insights into recovery.