Potential Siderophore-Enhanced Platinum-Group Element Mobility: The Rold of Siderophores on the Fate of Catalytic Converter Emissions

Automobile catalytic converters (CCs) use platinum-group elements (PGEs) to reduce the emission of harmful gasses; however, these devices concurrently emit particles containing Pt, Pd, and Rh. The fate of these metals in the environment and their toxicological effects are not well understood. This research focused on the effect of a siderophore, desferrioxamine-B (DFO-B), on the dissolution of catalytic converter metals. Batch experiments with pure metallic and oxide forms of the PGEs showed that Pd- and Pt-DFO-B aqueous complexes formed with estimated minimum stability constants on the order of 1020-24 and 1017-18, respectively. Additional batch experiments with powdered CC materials confirmed the relatively higher stability constant for Pd(II)-DFO-B versus that for Pt(II)- or Rh(III)-DFO-B and provided evidence to support a Pd(II)-DFO-B stability constant that is higher than the estimated 1020-24. Therefore Pd emitted from CCs has potential to be readily mobilized by DFO-B-like siderophores.