Redox dynamics of mixed metal (mn, cr, and fe) ultrafine particles

Peter S. Nico, Benjamin M. Kumfer, Ian M. Kennedy, Cort Anastasio

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O3, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e., greater than ∼8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging, implying that Mn can mediate oxidation by removal of electrons from other particulate metals.

Original languageEnglish (US)
Pages (from-to)60-70
Number of pages11
JournalAerosol Science and Technology
Volume43
Issue number1
DOIs
Publication statusPublished - Jan 1 2009

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ASJC Scopus subject areas

  • Environmental Chemistry
  • Materials Science(all)
  • Pollution

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