Extraction of Platinum Group Metals from the Acidic Leaching Solutions of Secondary Resources by Hydrometallurgical Methods: A Review.

The increasing demand for platinum group metals (PGMs) across various industries indicates the importance of recovering these noble metals from secondary resources. Typically, after pretreatment, PGMs are dissolved using hydrochloric acid solutions containing strong oxidant by virtue of the chemical stability of their anionic chloro-complexes. Several separation techniques, including cementation, precipitation, ion exchange, and solvent extraction, are employed to separate PGMs from leaching solutions. Each method has distinct advantages and limitations concerning efficiency and product purity. Cementation proves effective for concentrating PGMs in solutions containing base metal ions. However, ion exchange and solvent extraction are more commonly used for the separation of PGMs present in hydrochloric acid leaching solutions. Especially, solvent extraction processes employing commercial extractants, ionic liquids, and deep eutectic solvents have been extensively investigated. While deep eutectic solvents show promising as ‘green’ extractants, further research is required to overcome their limitations for industrial applications. A combined process integrating leaching, solvent extraction, and precipitation could offer an efficient solution for recovering high-purity PGMs from the solution containing diverse metal ions. [ABSTRACT FROM AUTHOR]