Recovering palladium and gold by peroxydisulfate-based advanced oxidation process

Area of Science:

• Materials Science
• Environmental Chemistry
• Chemical Engineering

Background:

• Palladium (Pd) and gold (Au) are critical precious metals (PMs) in industry, but their recycling from spent catalysts is challenging.
• Developing sustainable and efficient methods for PM recovery is essential due to resource limitations and environmental concerns.

Purpose of the Study:

• To develop a green and selective process for recovering Pd and Au from spent catalysts.
• To investigate the mechanism of oxidative dissolution using peroxydisulfate (PDS)-based advanced oxidation processes (AOPs).

Main Methods:

• Utilized a peroxydisulfate (PDS)/NaCl photochemical system and a Fenton-like system (PDS/FeCl2·4H2O) for metal dissolution.
• Employed electron paramagnetic resonance (EPR), 18O isotope tracing, and density functional theory (DFT) for mechanistic studies.
• Recovered high-purity Pd and Au via lixiviant leaching and one-step electrodeposition.

Main Results:

• Achieved complete dissolution of Pd and Au using the PDS/NaCl photochemical system.
• Demonstrated enhanced leaching efficiency with the PDS/FeCl2·4H2O Fenton-like system without Xe lamp irradiation.
• Identified reactive species (SO4·−, ·OH, Fe(IV)═O) responsible for oxidative dissolution.
• Successfully recovered high-purity Pd and Au through electrodeposition.

Conclusions:

• The PDS-based AOPs offer an efficient and sustainable approach for precious metal recovery.
• The developed method avoids strong acids, cyanide, and volatile organic solvents, aligning with green chemistry principles.
• Encourages the adoption of AOP technology for secondary resource recycling.