Iron Chloride Vapor Treatment for Leaching Platinum Group Metals from Spent Catalysts

Abstract

An efficient and environmentally friendly recovery of platinum group metals (PGMs) from secondary sources is necessary to ensure a sustainable supply of PGMs. In this study, contact with FeCl₂ vapor in the presence of metallic Fe was investigated as a useful pretreatment for leaching PGMs from spent automobile catalysts. Fe-PGM alloys were efficiently formed when Pt, Pd, and Rh wires and Rh₂O₃ powder were subjected to FeCl₂ vapor treatment at 1050 K (777 °C) for approximately 40 min. Further, the leachability of the PGMs in spent automobile catalyst samples increased after a similar vapor treatment was applied. When the pulverized spent catalyst sample without pretreatment was leached with aqua regia at 333 K (60 °C) for 60 min, 88% of Pt, 91% of Pd, and 37% of Rh were extracted. Meanwhile, after vapor treatment at 1050 K, 98% of Pt, 97% of Pd, and 87% of Rh were extracted under the same leaching conditions. Thus, the pretreatment with FeCl₂ vapor, followed by leaching, is a feasible and effective technique for recovering PGMs from spent catalysts.

Graphical Abstract