Utilizing Solid Phase Sorbents with Various Functional Groups Based on the HASAB Principle for Recovering Platinum Group Metals from Secondary Sources

Abstract

The study investigates the recovery of platinum-group metals (PGMs), Pd, Pt, and Rh, from secondary sources - spent catalytic converters, waste from a chemical industry, and a PGM refinery. Aquaregia was used to create leaching liquors and solid-phase extraction sorbents with different functional groups - DiOctyl Sulfide (DOS), Cyano (CN), Di-Ethylene Tetra-Amine (DETA), and strong anion exchanger (SAX) - were employed based on the "hard and soft acid and base (HASAB)" principles. The SAX-sorbent demonstrated the ability to retain PGMs in the presence of accompanying base metals selectively. In contrast, the DOS and CN sorbents were selective only for Pd, and the DETA sorbent displayed selectivity solely for Rh. Desorption experiments revealed that 3M HCl could effectively recover the PGMs from loaded solid-phase sorbents with significant HSE advantages. The study also noted the high stability of the sorbents, although improvements are needed, particularly in enhancing the reusability of the DETA-sorbent.