Levitt, Nicholas Paul (2007-05). Heterogeneous organic acid uptake on soot surfaces. Master's Thesis. Thesis uri icon

abstract

  • Atmospheric particulates have been known to act as cloud condensation nuclei (CCN) and therefore their presence can indirectly affect important processes such as global radiation balance through cloud formation. Soot particles are well known to be atmospheric constituents, but the hydrophobic nature of fresh soot likely prohibits them from encouraging cloud development. Soot aged through contact with oxygenated organic compounds may become hydrophilic enough to promote water uptake. In this study I have observed the interaction between a number of carboxylic acids and soot from different fuel sources and formation mechanisms. A low pressure fast flow reactor was used to control the contact between the solid phase soot and gas phase organics, while chemical ionization-mass spectrometry was utilized to monitor concentrations of gas phase organics. Most acids irreversibly deposited on the soot surfaces, and the uptake coefficient was measured in the wide range of 9.0 x 10-4 to 1.0 x 10-1. The Brunauer, Emmett, and Teller (BET) surface areas of the soots were measured and the soot bulk and surface chemical compositions were investigated with Fourier transform infrared (FTIR) spectroscopy and attenuated total reflection (ATR) spectroscopy to help explain differences in uptake. By comparing the mono and dicarboxylic acids and the information gathered from soot physiochemical properties I have discussed possible uptake mechanisms.
  • Atmospheric particulates have been known to act as cloud condensation nuclei
    (CCN) and therefore their presence can indirectly affect important processes such as
    global radiation balance through cloud formation. Soot particles are well known to be
    atmospheric constituents, but the hydrophobic nature of fresh soot likely prohibits them
    from encouraging cloud development. Soot aged through contact with oxygenated
    organic compounds may become hydrophilic enough to promote water uptake. In this
    study I have observed the interaction between a number of carboxylic acids and soot from
    different fuel sources and formation mechanisms. A low pressure fast flow reactor was
    used to control the contact between the solid phase soot and gas phase organics, while
    chemical ionization-mass spectrometry was utilized to monitor concentrations of gas
    phase organics. Most acids irreversibly deposited on the soot surfaces, and the uptake
    coefficient was measured in the wide range of 9.0 x 10-4 to 1.0 x 10-1. The Brunauer,
    Emmett, and Teller (BET) surface areas of the soots were measured and the soot bulk and
    surface chemical compositions were investigated with Fourier transform infrared (FTIR)
    spectroscopy and attenuated total reflection (ATR) spectroscopy to help explain
    differences in uptake. By comparing the mono and dicarboxylic acids and the
    information gathered from soot physiochemical properties I have discussed possible
    uptake mechanisms.

ETD Chair

publication date

  • May 2007