Spent automotive catalyst (SAC) is currently the main solid waste for platinum group metals (PGMs) recycling. The dissolution behavior of Pd in the CaO–SiO2–Al2O3–MgO–ZrO2–CeO2 slag system is crucial for efficient PGM recovery from SACs during smelting, yet few studies have been conducted on this subject. To minimize PGMs loss to slag by controlling process conditions during high-temperature recovery, the dissolution mechanism of Pd in the CaO–SiO2–Al2O3–MgO–ZrO2–CeO2 slag system was investigated in this study at temperatures ranging from 1723 K to 1823 K. The results indicate that increasing oxygen partial pressure significantly enhances Pd solubility in the slags, and maintaining the <InlineEquation ID="IEq1"> <EquationSource Format="TEX">${p}_{{\text{O}}_{2}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <msub> <mtext>O</mtext> <mn>2</mn> </msub> </msub> </math></EquationSource> </InlineEquation> below 10−2 atm effectively inhibits Pd dissolution into the slag. If at a relatively high partial pressure of oxygen, such as a fixed <InlineEquation ID="IEq2"> <EquationSource Format="TEX">${p}_{{\text{O}}_{2}}=0.21 \text{atm}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>p</mi> <msub> <mtext>O</mtext> <mn>2</mn> </msub> </msub> <mo>=</mo> <mn>0.21</mn> <mtext>atm</mtext> </mrow> </math></EquationSource> </InlineEquation>, when the mass ratio of CaO to (SiO2+Al2O3) in the final slags acted as the main variable, the solubility of Pd first decreased and then gradually increased with rising the corrected optical basicity, and reached its minimum value when the corrected optical basicity is approximately 0.59. Additionally, Pd solubility is also influenced by ZrO2 and CeO2. Increasing the concentrations of ZrO2 and CeO2 enhances Pd solubility, with CeO2 showing a more pronounced effect. Finally, practical recommendations for the recovery of Pd from SACs are provided, aimed at improving the theoretical recovery ratio based on the findings of this study. Graphical Abstract

Dissolution Behavior of Palladium in the CaO–SiO₂–Al₂O₃–MgO–ZrO₂–CeO₂ Slag for Recycling Spent Automotive Catalyst

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发表日期：

2026年4月28日

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Jiao Chen,
Sen Luo,
Yun Lei,
Yongsheng Ren,
Dongfang Yang,
Yuefei Hu,
Wenhui Ma

摘要

Spent automotive catalyst (SAC) is currently the main solid waste for platinum group metals (PGMs) recycling. The dissolution behavior of Pd in the CaO–SiO₂–Al₂O₃–MgO–ZrO₂–CeO₂ slag system is crucial for efficient PGM recovery from SACs during smelting, yet few studies have been conducted on this subject. To minimize PGMs loss to slag by controlling process conditions during high-temperature recovery, the dissolution mechanism of Pd in the CaO–SiO₂–Al₂O₃–MgO–ZrO₂–CeO₂ slag system was investigated in this study at temperatures ranging from 1723 K to 1823 K. The results indicate that increasing oxygen partial pressure significantly enhances Pd solubility in the slags, and maintaining the ${p}_{{\text{O}}_{2}}$ $p_{O_{2}}$ below 10⁻² atm effectively inhibits Pd dissolution into the slag. If at a relatively high partial pressure of oxygen, such as a fixed ${p}_{{\text{O}}_{2}}=0.21 \text{atm}$ $p_{O_{2}} = 0.21 atm$ , when the mass ratio of CaO to (SiO₂+Al₂O₃) in the final slags acted as the main variable, the solubility of Pd first decreased and then gradually increased with rising the corrected optical basicity, and reached its minimum value when the corrected optical basicity is approximately 0.59. Additionally, Pd solubility is also influenced by ZrO₂ and CeO₂. Increasing the concentrations of ZrO₂ and CeO₂ enhances Pd solubility, with CeO₂ showing a more pronounced effect. Finally, practical recommendations for the recovery of Pd from SACs are provided, aimed at improving the theoretical recovery ratio based on the findings of this study.

Graphical Abstract

Dissolution Behavior of Palladium in the CaO–SiO2–Al2O3–MgO–ZrO2–CeO2 Slag for Recycling Spent Automotive Catalyst

摘要

Dissolution Behavior of Palladium in the CaO–SiO₂–Al₂O₃–MgO–ZrO₂–CeO₂ Slag for Recycling Spent Automotive Catalyst