A Molten Salt Extraction Method for Palladium Recovery via the CaPd₂ Intermetallic Compound

Area of Science:

• Materials Science
• Metallurgical Engineering
• Inorganic Chemistry

Background:

• Palladium scarcity necessitates efficient recovery methods.
• Conventional processes (pyrometallurgical, hydrometallurgical) have limitations.
• Molten-salt extraction offers a potential alternative for metal recovery.

Purpose of the Study:

• To develop a molten-salt extraction strategy for palladium recovery.
• To investigate the CaPd2 intermetallic compound for this purpose.
• To establish an iodine-mediated recovery mechanism.

Main Methods:

• First-principles calculations to understand CaPd2 bonding.
• Synthesis and experimental verification of CaPd2 via XRD and TGA.
• Molten-salt extraction using molten CaI2 and active iodine species.

Main Results:

• CaPd2 exhibits strong ionic bonding with covalent contributions, ensuring thermal stability (<0.13% mass loss up to 1273 K).
• Iodine species in molten CaI2 selectively oxidize CaPd2, enabling metallic palladium recovery.
• Optimized conditions (1073 K, 1 hour) yielded palladium with 99.5 ± 0.3 wt.% purity.

Conclusions:

• A novel, acid-leaching-free method for rapid palladium recovery from secondary resources is established.
• The iodine-mediated molten-salt mechanism provides an efficient route for palladium extraction.
• This approach addresses palladium scarcity by offering a viable alternative to conventional methods.