TY - JOUR
T1 - Palladium release from catalytic converter materials induced by road de-icer components chloride and ferrocyanide
AU - Aruguete, Deborah M.
AU - Wallace, Adam
AU - Blakney, Terry
AU - Kerr, Rose
AU - Gerber, Galen
AU - Ferko, Jacob
PY - 2020/4
Y1 - 2020/4
N2 - Environmental levels of platinum group elements (PGEs) are rising due to emissions of vehicle catalytic converter (VCC) materials containing palladium, platinum and rhodium. When these PGE-containing VCC materials are exposed to soil and water, coordination complex formation with ligands present in the environment may mobilize PGEs into solution, particularly Pd. Road de-icing salt contains two ligands with high affinities for Pd2+: chloride (Cl−) from NaCl and cyanide (CN−) from ferrocyanide (Fe(CN)64−) anti-caking agents. Batch leaching studies of VCC materials were conducted with solutions representative of de-icer-contaminated road runoff at pH 8 and room temperature for 48 h. Ferrocyanide (FC) concentrations of 0 μM, 1 μM, 2 μM and 10 μM were tested with background electrolyte concentrations of 0.028 M NaCl (1000 mg/L Cl−) or 0.028 M NaClO4. Palladium release increased with FC concentration, ranging from 0.014 ± 0.002 μM Pd without FC to 5.013 ± 0.002 μM Pd at 10 μM FC. At 0 μM, 1 μM and 2 μM FC, chloride induced further Pd release, but had no effect at 10 μM FC. PHREEQC modeling predicted that the predominant species present in equilibrium with Pd(OH)2(s) were Pd(OH)20 and Pd(CN)42−, and that PdClx2−x complexes had only a minor effect on the total concentration of dissolved palladium. The effect of FC on Pd release was predicted but not the effect of Cl−, indicating possible kinetic control. Platinum was measured above limits of detection (LODs) only at 10 μM FC, and rhodium levels were below LODs, consistent with their slower complexation kinetics.
AB - Environmental levels of platinum group elements (PGEs) are rising due to emissions of vehicle catalytic converter (VCC) materials containing palladium, platinum and rhodium. When these PGE-containing VCC materials are exposed to soil and water, coordination complex formation with ligands present in the environment may mobilize PGEs into solution, particularly Pd. Road de-icing salt contains two ligands with high affinities for Pd2+: chloride (Cl−) from NaCl and cyanide (CN−) from ferrocyanide (Fe(CN)64−) anti-caking agents. Batch leaching studies of VCC materials were conducted with solutions representative of de-icer-contaminated road runoff at pH 8 and room temperature for 48 h. Ferrocyanide (FC) concentrations of 0 μM, 1 μM, 2 μM and 10 μM were tested with background electrolyte concentrations of 0.028 M NaCl (1000 mg/L Cl−) or 0.028 M NaClO4. Palladium release increased with FC concentration, ranging from 0.014 ± 0.002 μM Pd without FC to 5.013 ± 0.002 μM Pd at 10 μM FC. At 0 μM, 1 μM and 2 μM FC, chloride induced further Pd release, but had no effect at 10 μM FC. PHREEQC modeling predicted that the predominant species present in equilibrium with Pd(OH)2(s) were Pd(OH)20 and Pd(CN)42−, and that PdClx2−x complexes had only a minor effect on the total concentration of dissolved palladium. The effect of FC on Pd release was predicted but not the effect of Cl−, indicating possible kinetic control. Platinum was measured above limits of detection (LODs) only at 10 μM FC, and rhodium levels were below LODs, consistent with their slower complexation kinetics.
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U2 - 10.1016/j.chemosphere.2019.125578
DO - 10.1016/j.chemosphere.2019.125578
M3 - Article
C2 - 31864058
AN - SCOPUS:85076530380
VL - 245
JO - Chemosphere
JF - Chemosphere
SN - 0045-6535
M1 - 125578
ER -