Thermodynamic Analysis of Silicon–Platinum Group Metal (Pt, Pd, and Rh) Interactions in Iron-Based Solutions
Year: 2026
Type: article
Abstract: Platinum group metals (Pt, Pd, Rh), valuable secondary resources from spent automotive three-way catalysts, are generally recovered by high-temperature pyrometallurgical iron-collection processes. The cordierite support (2MgO·2Al2O3·5SiO2) releases Si into the iron melt, yet how Si affects Pt, Pd and Rh capture by liquid Fe remains poorly understood due to insufficient thermodynamic data. This work is the first to systematically calculate the temperature-dependent activity interaction coefficients between Si and PGMs in the Fe–Pt/Pd/Rh–Si ternary system. Using the Molecular Interaction Volume Model (MIVM) and the Wagner model, the activity interaction coefficients between Si and the PGMs were calculated over the temperature range of 1773–1973 K. The results indicate that, within this temperature range, the activity interaction coefficient between Si and Pd (εPdSi) is negative, indicating that the addition of Si reduces the activity coefficient of Pd; the activity interaction coefficients between Si and Pt and Rh (εPtSi and εRhSi) are positive, indicating that the addition of Si increases the activity coefficients of Pt and Rh. Furthermore, the temperature rose from 1773 K to 1973 K, and εPdSi and εRhSi increase with rising temperature, with εPdSi ranging from −1.016 to −0.880; εRhSi increases from 0.051 to 0.075, while εPtSi decreases with rising temperature, with εPtSi decreasing from 0.536 to 0.497. Electron probe microanalysis (EPMA) results confirmed the above calculations: Pd forms an enriched phase of an intermetallic compound with Si, while Pt and Rh are uniformly solid-solved in the iron matrix. These findings provide theoretical guidance for optimizing pyrometallurgical recovery processes of platinum group metals from silicon-containing secondary resources (particularly waste automotive catalysts).
Source: Separations
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,137
OpenAlex ID: W7224107952