Recovery of Platinum and Ruthenium from PEM Electrodes via Hydrometallurgical Approach

The recovery of platinum group metals (PGMs) from secondary sources is becoming increasingly relevant from an economic and environmental perspective. This study aims to explore a hydrometallurgical approach for recycling platinum (Pt) and ruthenium (Ru) from proton exchange membrane (PEM) electrodes. The methodology includes a comprehensive recycling scheme comprising pre-treatment, leaching, volatilization, and precipitation processes. A parametric study was conducted to examine various factors influencing the recovery yields, such as reagent concentration, leaching temperature, and solid-to-liquid ratio. The results showed high recovery rates, achieving 90% for Pt and 82% for Ru after 4 hours of leaching at 75 °C in 4 M HCl with the addition of 1.5 M AlCl3. Two methods were implemented for Pt/Ru separation: Ru volatilization and selective Pt precipitation. The use of 1 M Na2S2O8 for Ru volatilization resulted in a complete recovery (up to 100%) in just 1.5 hours. Moreover, selective precipitation of Pt was accomplished with 5 M NH4Cl, resulting in up to 96% Pt recovery within 30 minutes while only minimal Ru precipitation occurred. This efficient recycling procedure allows for the reuse of obtained PGM salts as precursors for manufacturing new electrocatalysts.