DESORPTION OF PERYLENE FROM COMBUSTION, NACL, AND CARBON PARTICLES

The gas/particle distribution of perylene as a model PAH (polyaromatic hydrocarbon) is measured within a temperature range from 300 to 650 K. Perylene is adsorbed onto the core of combustion particles of different size (30-80 nm in diameter) and origin (diesel engine and oil burner), carbon particles, and NaCl particles. The adsorbed perylene consists of a fraction x, that is nonremovable at temperatures up to 650 K and a fraction that can be desorbed at temperatures below 500 K. The mean desorption temperature T50% (50% of perylene still in the particulate phase) and the fraction x are increasing with increasing diameter of the particles in the case of combustion particles and carbon particles. T50% and x of the NaCl particles show no size dependence. The desorption enthalpy E(d) is close to the evaporation enthalpy of perylene. However, to model the experimental results by a two-step adsorption model, a distribution of E(d) instead of a single value has to be assumed. The results show that carbon particles may be used as a model for combustion particles when studying the adsorption of low volatile PAHs, whereas NaCl particles show considerable differences in their sorption properties.