Adsorption of Nitrogen and Xylene by Light-Duty Diesel Exhaust Samples

• Published in: Aerosol science and technology 1985-01, Vol.4 (4), p.383-400
• Main Authors: Rothenberg, S. J., Kittelson, D. B., Cheng, Y. S., McClellan, R. O.
• Format: Article
• Language: English
• Subjects: Air pollution caused by fuel industries; Applied sciences; Atmospheric pollution; Characteristics of pollutants and their action; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution
• ISSN: 0278-6826; 1521-7388
• DOI: 10.1080/02786828508959065

Specific surface areas, desorption half-times, and weight loss curves were determined for three samples of diesel exhaust particles from light-duty vehicles. Data were obtained at the 25°C-600°C temperature range. More than 15% of each sample was volatilized at 250 °C and 10 −6 Torr. Desorption half-times exceeded 5 min for all samples. The apparent specific surface areas were strongly dependent on the outgassing temperature, ranging from ≃ 60 m 2 g −1 at 50°C to ≃ 120 m 2 g −1 or more at 450 °C. The specific surface area of a sample stored in nitrogen from the time of sampling to the time of analysis exceeded that of air-stored samples by ≃ 50%. Adsorption of m-Xylene by the heat-treated samples was studied over the P/P° range 0.03-0.9. M-Xylene adsorption isotherms demonstrated sharp "knee-points" at P/P° < 0.05, corresponding to heats of adsorption of ≃ 13 kcal. M-Xylene adsorption half-times at P/P° < 0.5 exceeded 2 min, and samples adsorbed more than 50% of their own weight at P/P° < 0.7. Scanning electron microscopy demonstrated that the particles were short branch-chained aggregates of primary particles (aciniform carbon), but that these formed sponge-like structures when collected in bulk. The interstices in these structures filled with m-Xylene at P/P° < 0.7. The high specific surface areas and strong interaction with m-Xylene demonstrate that diesel exhaust particles are stronger adsorbents than most anthropogenic emissions.