title: The pH-dependent release of platinum group elements (PGEs) from gasoline and diesel fuel catalysts: Implication for weathering in soils.
abstract: Powdered samples of new and old gasoline catalysts (Pt, Pd, Rh) and new and old diesel (Pt) catalysts were subjected to a pH-static leaching procedure (pH 2-9) coupled with thermodynamic modeling using PHREEQC-3 to verify the release and mobility of PGEs (platinum group elements). PGEs were released under acidic conditions, mostly exhibiting L-shaped leaching patterns: diesel old: 5.47, 0.005, 0.02; diesel new: 68.5, 0.23, 0.11; gasoline old: 0.1, 11.8, 4.79; gasoline new 2.6, 25.2, 35.9 in mg kg(-1) for Pt, Pd and Rh, respectively. Only the new diesel catalyst had a strikingly different leaching pattern with elevated concentrations at pH 4, probably influenced by the dissolution of the catalyst carrier and washcoat. The pH-static experiment coupled with thermodynamic modeling was found to be an effective instrument for understanding the leaching behavior of PGEs under various environmental conditions, and indicated that charged Pt and Rh species may be adsorbed on the negatively charged surface of kaolinite or Mn oxides in the soil system, whereas uncharged Pd and Rh species may remain mobile in soil solutions.
authors.affiliation: Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, CZ - 128 43 Prague 2, Czech Republic.
authors.forename: Veronika
authors.initials: V
authors.lastname: Suchá
authors.affiliation: Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, CZ - 128 43 Prague 2, Czech Republic. Electronic address: mihal@natur.cuni.cz.
authors.forename: Martin
authors.initials: M
authors.lastname: Mihaljevič
authors.affiliation: Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University, Albertov 6, CZ - 128 43 Prague 2, Czech Republic.
authors.forename: Vojtěch
authors.initials: V
authors.lastname: Ettler
authors.affiliation: Laboratories of Geological Institutes, Faculty of Science, Charles University, Albertov 6, CZ - 128 43 Prague 2, Czech Republic.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Strnad
mesh_terms: D002384:Catalysis; D005742:Gasoline; D006863:Hydrogen-Ion Concentration; D010165:Palladium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D012238:Rhodium / Q000737:chemistry*; D012987:Soil / Q000737:chemistry
chemical_list: D005742:Gasoline; D012987:Soil; D010984:Platinum; D010165:Palladium; D012238:Rhodium
keywords: Automobile catalysts; Platinum group elements; Speciation; pH-static experiment