Vehicle catalytic converters (VCCs) have been an essential application of nanotechnology since the 1970s, dramatically improving air quality by converting harmful engine emissions to more benign gases. The active components in VCCs are platinum group element (PGE) nanoparticles of palladium (Pd), platinum (Pt), and rhodium (Rh) as well as nanoparticles of oxides including ceria, alumina, and zirconia. Rising use of VCCs from increasing vehicle ownership continues to increase the input of PGEs to the environment. The fate of these solids is unknown, but one possibility of concern is dissolution of the PGE particles coupled to the formation of stable coordination complexes. We report results of our investigation into this possibility. Batch leaching studies were conducted mixing commercially-available VCC materials with solutions containing varying levels and combinations of environmentally-common ligands including chloride and ammonia, as well as cyanide (sourced from ferrocyanide in road deicing salt). Powdered VCC materials were exposed to varying concentrations of chloride (0, 1000, 4000, and 10000 ppm as NaCl), ammonia (0, 0.1, 1 and 2147 ppm as NH4NO3) and ferrocyanide (0, 1, 2 and 10 ppm as Na4Fe(CN)6) at pH 8 for 48 hours. Elemental analysis of leachates revealed a synergistic increase in Pd release when chloride was present at lower concentrations of ferrocyanide and ammonia but not at the highest concentrations. Platinum release followed trends similar to those of Pd but was limited. The results will be discussed in the context of coordination chemistry equilibria and a materials characterization included.

Palladium and platinum release from vehicle catalytic converter materials exposed to common environmental ligands

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.