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°C; pO2, 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°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.
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