Resource Recovery of Cerium from Spent Catalytic Converter Using Aqueous Metallurgy

Cerium recovery from a secondary waste stream generated after the extraction of Pt-group metals from spent catalytic converter has been investigated. Different mineral acids alone used as lixiviant could leach only 33% cerium; however, HF added acid mixture showed an increased leaching up to 96%. The determined value of activation energy 31.8 kJ/mol revealed that leaching progressed via diffusion-controlled mechanism. Subsequently, cerium from leach liquor was extracted using 4 tri-alkyl phosphine oxides in kerosene, which indicated the formation of extracted species to be [Ce(SO4)(2)center dot 2L center dot HSO4-](org). The loaded organic was quantitatively stripped back into the H2SO4 solution by adding an H2O2 dosage as a reducing agent. Thus, obtained Ce-bearing stripped solution was treated with oxalic acid to precipitate high-purity Ce-2(C2O4)(3). The process is simple and potentially dealt to recycle the critical metal values which remained less attractive until now.

Automated summary

This study investigated the recovery of cerium from a secondary waste stream generated after extracting Pt-group metals from spent catalytic converters. By using acid mixtures for leaching and extraction processes, high efficiency in recovering cerium was achieved, providing a new pathway for recycling critical metal values from waste materials.