Recovery of Platinum-Group Metals from an Unconventional Source of Catalytic Converter Using Pressure Cyanide Leaching and Ionic Liquid Extraction

The fast depletion of critical metals in natural reserves against their increasing demands in advanced technology application presents the necessity to exploit the end-of-life/waste materials as unconventional resources. Due to a higher accumulation of platinum-group metals (PGMs) in exhausted autocatalytic converters, their recycling through an integrative bio-solvo-chemical technique has been studied. PGMs were efficiently dissolved in bio-cyanide solution produced by Chromobacterium violaceum. The autoclave leaching was optimized in the conditions of temperature, 150 degrees C; pO(2), 200 psi; and time, 120 min, yielding > 90% PGMs' dissolution. PGMs' separation from cyanide leach liquor was performed using an ionic liquid, Cyphos IL101. Under optimum conditions (i.e., ionic liquid concentration, 0.15 mol/L; extraction pH, 10.4; and temperature, 25 degrees C), Pt and Pd were selectively stripping with > 99% efficiency in 0.1 mol/L (acidic) thiourea and 1.0 mol/L HNO3 solution, respectively, leaving Rh in the raffinate.

Automated summary

The depletion of critical metals in natural reserves and the increasing demands in advanced technology application highlight the need to explore end-of-life/waste materials as unconventional resources. A study found that an integrative bio-solvo-chemical technique could efficiently recycle platinum-group metals (PGMs) from exhausted autocatalytic converters.