Nanoparticle
and Nanofiber Filtration
Jing Wang
Particle
Technology Laboratory, Mechanical Engineering,
The
rapid development of nanotechnology brings new challenges and opportunities to
the research of filtration.
Nanoparticles have huge surface area per unit of mass and
can pose serious health risk when inhaled. There is a serious concern that nanoparticles may bounce though filters due to their high
thermal energy. We have performed filtration tests of silver particles in the range
of 3 – 20 nm in a variety of filter media, including screen filters, standard
fiberglass filters and a selection of personal protective equipment filters.
The testing results show that the penetration decreases as the particle size
decreases. Thermal rebound in the tested filter media is not detected down to 3
nm particles. Filtration tests have also been carried out for nanoparticle
agglomerates and it is found that the filtration efficiency for agglomerates is
higher than for spheres of the same mobility diameter.
Nanofiber filters have emerged as promising filters which
can provide greater filtration efficiencies and better performances than
conventional fibers. We have tested nanofiber filters
composed of nanofiber layers and a substrate made of
micrometer filters. The results show that nanofibers
can improve the filtration performance near the most penetrating particle size
but not for very small nanoparticles. We have
established a numerical model to study filtration; mechanisms for particle capture
due to interception, inertial impaction and diffusion are covered. The
numerical model is employed to simulate filtration of nanofiber
filters and the results agree well with the experimental ones for a wide range
of particle sizes. The most penetrating particle size and the minimum
efficiency are computed with satisfying accuracy.