Process and mechanism of enhanced HCl leaching of platinum group metals from waste three-way catalysts by Li2CO3 calcination pretreatment

Shiqiang Sun; Chenxi Jin; Wenting Zhao; Wenzhi He; Guangming Li; Haochen Zhu; Juwen Huang

doi:10.1016/j.jhazmat.2023.131348

Process and mechanism of enhanced HCl leaching of platinum group metals from waste three-way catalysts by Li₂CO₃ calcination pretreatment

J Hazard Mater. 2023 Jun 15:452:131348. doi: 10.1016/j.jhazmat.2023.131348. Epub 2023 Apr 3.

Authors

Shiqiang Sun¹, Chenxi Jin¹, Wenting Zhao¹, Wenzhi He², Guangming Li¹, Haochen Zhu¹, Juwen Huang¹

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, Shanghai, PR China; School of Environmental Science and Engineering, Tongji University, Shanghai, PR China.
² State Key Laboratory of Pollution Control and Resource Reuse, Shanghai, PR China; School of Environmental Science and Engineering, Tongji University, Shanghai, PR China. Electronic address: hithwz@163.com.

PMID: 37027921
DOI: 10.1016/j.jhazmat.2023.131348

Abstract

Recovery of platinum group metals (PGMs) from waste three-way catalysts (TWCs) was usually achieved by dissolving them in an acid solution. However, their dissolution requires the addition of oxidizing agents such as Cl₂ and aqua regia, which could cause high environmental risks. Therefore, the development of new methods without the addition of oxidant agents will contribute to the green recovery of PGMs. In this paper, the process and mechanism of PGMs recovery from waste TWCs by Li₂CO₃ calcination pretreatment-HCl leaching were studied in detail, and molecular dynamics calculations were performed for the formation processes of Pt, Pd, and Rh complex oxides. The results showed that the leaching rates of Pt, Pd, and Rh could reach about 95%, 98%, and 97%, respectively, under the optimal conditions. Li₂CO₃ calcination pretreatment cannot only oxidize Pt, Pd, and Rh metals to HCl-soluble Li₂PtO₃, Li₂PdO₂, and Li₂RhO₃, but also remove the carbon accumulation in waste TWCs and open the wrapping of PGMs by the substrate and Al₂O₃ coating. The embedding of Li and O atoms in metallic Pt, Pd, and Rh is an interacting embedding process. Although the Li atoms are faster than O, O will accumulate on the metal surface first before embedding.

Keywords: Complex oxides; Molecular dynamics calculation; Open the wrapping; Spent automotive catalysts.