Recovery of Platinum Group Metals from Spent Automotive Catalyst Leachate using Activated Carbon Fiber Cloth through Electrodeposition

Abstract Description: Palladium (Pd) and Platinum (Pt), precious metals known for their high catalytic activity and chemical inertness, play a crucial role in industrial catalysts and the electronics industry. Their significant application in automotive catalysts is vital for reducing harmful emissions from exhaust gases. However, with their rarity and increasing demand, the development of effective technologies for recovering these metals from spent automotive catalysts (SACs) is essential to mitigate reliance on mining and promote a circular economy.

Adsorption is a widely used method in hydrometallurgy for recovering Pt and Pd; however, its practical applications are limited by slow kinetics and the need for high dosages of adsorbents. In contrast, electrochemical recovery methods offer advantages such as lower consumption of chemical reagents and fast reaction kinetics. Recent studies suggested the materials with nitrogen functional groups enhance the recovery efficiency of precious metals through adsorption and also improve electrochemical performance.
This study focused on the use of activated carbon fiber cloth (ACFC) for the electrodeposition of Pd and Pt from SAC leachates due to its good conductivity and enrichment with nitrogen-containing functional groups. Key variables such as pH, applied potential, and chloride ion concentration were examined to identify optimal electrodeposition conditions. Additionally, batch adsorption experiments were performed without electrical charging for comparison. The selectivity of ACFC was also assessed in multi-metal systems involving Pt, Pd, aluminum (Al), cerium (Ce), and magnesium (Mg).
Preliminary results show that under a constant potential of −0.2 V, using ACFC as the cathode to recover Pd and Pt through electrodeposition significantly enhances reaction rates compared to batch adsorption conditions. Under specific solution parameters (20 mg/L concentration of Pd(II) or Pt(IV), pH 2), ACFC achieved over 98% and 90% recovery efficiency for Pd and Pt within 3 and 6 hours, respectively. It also demonstrated high selectivity for Pd and Pt, achieving recoveries roughly ten times greater than those for other metals like Al, Ce, and Mg. This research highlights the promising application of ACFC for efficiently recovering low concentrations of precious metals, characterized by enhanced kinetics, lower material usage, and high selectivity.