Filtration of Ultrafine Aerosols: Small Particles, Many Questions
Advancing the chemical engineering fundamentals
Filtration - I (T2-11a)
Keywords: nanoparticles, aerosol filtration, filtration efficiency, fibrous filters
Offering very attractive perspectives in many industrial sectors, nanoscience and nanotechnologies currently know a development like no other before it. In the meanwhile, scientific community, toxicologists in particular, wonders and warns us about the environmental and health impacts of nanoparticles (diameter less than 100 nm) [1], all the more since we are unsure to be able to efficiently collect, and so protect ourselves against these tiny particles. Indeed, nanoparticles had been expected for a long time to be capted by fibrous filters thanks to Brownian diffusion [2], but in 1991, Wang and Kasper [3] challenged the classical filtration theories with the thermal rebound effect: according to them, filtration efficiency could decrease below 10 nanometers. Wang then validated this theory from Ichitsubo’s experimental results [4] on the penetration of ultrafine particles through wire screens. In 1995, Otani and al. [5] also observed an increase in penetration of particles smaller than 2 nm through circular tubes. However, recent studies [6-7] explained these latter results as the consequence of unreliable measurements and showed that particles down to 2 nm in diameter would behave the way the classical filtration theories predict.
All these results can be controversial since the generation and characterization of nanoparticles are both very complex. Thus, we have carried out experiments on a specific setup to contribute to the research led in this domain. Results are compared to the theory and pre-cited works.
[1] Borm P.J.A., Robbins D., Haubold S., Kuhlbusch T., Fissan H., Donaldson K., Schins R.P.F., Stone V., Kreyling W., Lademann J., Krutmann J., Warheit D. et Oberdorster E. (2006) - The Potential Risks of Nanomaterials : a review carried out for ECETOC, Particle and Fibre Toxicology, 3, 11
[2] Brown R.C. (1993) - Air Filtration : an Integrated Approach to the Theory and Applications of Fibrous Filters. Oxford, Pergamon Press
[3] Wang H.C., Kasper G. (1991) – Filtration Efficiency of Nanometer-Size Aerosol Particles, J. Aerosol. Sci, 22, pp. 31-41
[4] Ichitsubo H., Hashimoto T., Alonso M., Kousaka Y. (1996) – Penetration of Ultrafine Particles and Ion Clusters through Wire Screens, Aerosol Sci. Technol., 24, pp. 119-127
[5] Otani Y., Emi H., Cho S.-J. et Namiki N. (1995) - Generation of Nanometer Size Particles and their Removal from Air, Advanced Powder Technology, 6, 4, pp.271-281
[6] Alonso M., Kousaka Y., Hashimoto T. et Hashimoto N. (1997) - Penetration of Nanometer-Sized Aerosol Particles through Wire Screen and Laminar Flow Tube, Aerosol Science and Technology, 27, pp.471-480
[7] Heim M., Mullins B.J., Wild M., Meyer J. et Kasper G. (2005) - Filtration Efficiency of Aerosol Particles below 20 Nanometers, Aerosol Science and Technology, 39, pp.782-789
Presented Monday 17, 11:15 to 11:33, in session Filtration - I (T2-11a).
