Professor National Taiwan University, Taipei, Taiwan (Republic of China)
Abstract Description: Platinum group metals (PGMs) play a crucial role in modern technology and various industrial applications due to their high melting points, exceptional corrosion and oxidation resistance, stability, and outstanding catalytic activity. Among them, platinum (Pt), palladium (Pd), and rhodium (Rh) are predominantly demanded by the automotive industry as irreplaceable components of catalytic converters. However, the scarcity, uneven distribution, high cost, and environmental impact of PGMs necessitate their recovery from secondary sources. Recycling spent automotive catalysts (SACs) has emerged as a key solution, with pyrometallurgy, hydrometallurgy, and biohydrometallurgy being the primary recovery methods. Compared to pyrometallurgy, hydrometallurgy offers higher purification efficiency, scalability, lower energy consumption, and improved recovery rates, whereas biohydrometallurgy remains largely at the experimental stage due to its complex operational conditions and sensitivity to factors such as pH, temperature, and ionic strength.
Adsorption has garnered significant attention due to its high efficiency, cost-effectiveness, and operational flexibility. Metal-organic frameworks (MOFs), characterized by high specific surface areas, excellent thermal and mechanical stability, high porosity, and tunable pore structures, have emerged as promising adsorbents. Among them, MIL-53(Fe) exhibits good structural stability and strong light absorption capabilities, though its relatively low surface area limits its adsorption performance. In contrast, MIL-53(Al) possesses a higher specific surface area and a unique breathing effect, making it a more suitable candidate for adsorption applications. Studies have shown that introducing a secondary metal into MOFs can preserve the advantages of the core framework while further enhancing adsorption performance.
In this study, NH₂-MIL-53(Fe, Al) bimetallic MOFs were synthesized via the solvothermal method, with amine functionalization and Fe/Al ratio modulation aimed at optimizing electronic properties and increasing adsorption sites for Pt and Pd ions. The effects of metal composition on adsorption performance and physicochemical properties were evaluated, alongside assessments of material stability, operational conditions, and reusability. Preliminary results indicate that NH₂-MIL-53(Fe, Al) exhibits significantly enhanced Pt and Pd adsorption capacity compared to monometallic NH₂-MIL-53. Under optimal conditions (24-hour contact time, 0.26 g/L adsorbent dosage, 10 mg/L initial Pt and Pd concentrations, and pH 3), NH₂-MIL-53(Fe:Al = 3:2) achieved a Pd adsorption efficiency of 99.9% and a Pt adsorption efficiency of 98%. Furthermore, selective adsorption experiments demonstrated a high specificity for Pt and Pd, highlighting the material’s potential for efficient PGM recovery and providing a promising direction for future advancements in precious metal recycling technologies.
