title: Dissolution kinetics of Pd and Pt from automobile catalysts by naturally occurring complexing agents.
abstract: Powder samples prepared from gasoline (Pt, Pd, Rh, new GN/old GO) and diesel (Pt, new DN/old DO) catalysts and recycled catalyst NIST 2556 were tested using kinetic leaching experiments following 1, 12, 24, 48, 168, 360, 720 and 1440-h interactions with solutions of 20mM citric acid (CA), 20 mM Na(2)P(4)O(7) (NaPyr), 1 g L(-1) NaCl (NaCl), a fulvic acid solution (FA-DOC 50 mg L(-1)) and 20 mM CA at pH 3, 4, 5, 6, 7, 8 and 9. The mobilisation of platinum group elements (PGEs) was fastest in solutions of CA and NaPyr. In the other interactions (NaCl, FA), the release of PGEs was probably followed by immobilisation processes, and the interactions were not found to correspond to the simple release of PGEs into solution. Because of their low concentrations, the individual complexing agents did not have any effect on the speciation of Pd and Pt in the extracts; both metals are present in solution as the complexes Me(OH)(2), Me(OH)(+). Immobilisation can take place through the adsorption of the positively charged hydroxyl complexes or flocculation of fulvic acid, complexing the PGEs on the surface of the extracted catalysts. The calculated normalised bulk released NRi values are similar to the reaction rate highest in the solutions of CA and NaPyr.
authors.affiliation: Laboratories of the Geological Institutes, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
authors.forename: Ondřej
authors.initials: O
authors.lastname: Sebek
authors.forename: Martin
authors.initials: M
authors.lastname: Mihaljevič
authors.forename: Ladislav
authors.initials: L
authors.lastname: Strnad
authors.forename: Vojtěch
authors.initials: V
authors.lastname: Ettler
authors.forename: Josef
authors.initials: J
authors.lastname: Ježek
authors.forename: Robin
authors.initials: R
authors.lastname: Stědrý
authors.forename: Petr
authors.initials: P
authors.lastname: Drahota
authors.forename: Lukáš
authors.initials: L
authors.lastname: Ackerman
authors.forename: Vladimír
authors.initials: V
authors.lastname: Adamec
mesh_terms: D001336:Automobiles; D002384:Catalysis; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D010165:Palladium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D012995:Solubility; D001335:Vehicle Emissions
chemical_list: D001335:Vehicle Emissions; D010984:Platinum; D010165:Palladium