Novel approach for synergistic capturing of platinum group metals from spent automotive catalysts with Pb-Bi alloy

Abstract

Considering the substantial environmental and economic benefits, the extraction of platinum group metals (PGMs) from spent automotive catalysts (SAC) attracted significant interest. In this paper, a novel method to extract PGMs by Pb-Bi alloy was proposed. In this process, PbO and Bi₂O₃ are initially employed as collectors to extract PGMs. Subsequently, the Pb-Bi-PGMs alloy undergoes oxidative cupellation to enrich PGMs. The feasibility of Pb-Bi for capturing PGMs was confirmed by calculating the Gibbs free energy. A low-temperature slag system comprising CaO-(SiO₂)_0.66(Al₂O₃)_0.34-FeO was designed. Additionally, the parameters affecting the capture process were systematically investigated. The optimized conditions were: m(CaO)/m(SiO₂) of 1.0, m(SiO₂)/m(Al₂O₃) of 3.00, m(FeO)/m(SiO₂) of 0.8, $N_{C/(PbO+B{i}_2{O}_3)}$ of 1.0, 1275 °C for 120 min, collector dosage of 100 wt% with m(PbO)/m(Bi₂O₃) of 1/1. Under these conditions, 99.3 % of Pt, 99.19 % of Pd and 98.8 % of Rh were recovered. Furthermore, the capture process of Pb-Bi alloy for PGMs was analyzed, encompassing metal reduction, metal migration and synergistic capture, as well as alloy settlement. Eventually, oxidative cupellation effectively concentrated the PGMs, resulting in an alloy with maximum concentrations of 7.16 % Pt, 13.69 % Pd, and 3.32 % Rh. In summary, this study presents a novel and efficient strategy for extracting PGMs from SAC, addressing the limitations of traditional methods and offering significant potential for industrial application.