10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Selective Collection in Particle Harvesting
MENG-DAWN CHENG, Oak Ridge National Laboratory
Abstract Number: 1057 Working Group: Instrumentation
Abstract Application of magnetic collection has a long history to atmospheric source identification[1],[2],[3],[4],[5] and as the marker for indoor air pollution[6]. In fact, most elements in the periodic table and their oxide forms are paramagnetic. Thus, magnetic collection could provide an effective means of environmental sampling of aerosol particles that consist of magnetic materials. This would in essence enhance the analyte signal by selectively collect particles consisting of only relevant composition at the time of collection. To trigger selective magnetic material harvesting from airborne particulate matter, first the magnetic circuit needs to generate high-gradient magnetic field density on the order of a few Tesla (T) per meter. The recent advance in additive manufacturing of permanent magnets enable the design of such a circuit with the magnetic field density around 16 T/m, which makes selective collection of aerosol particles by their magnetic property in a small footprint and with a low-power consumption mode possible.
In this presentation, we will report the development of a particle selective collector based on a HGPMS circuit using NdFeB permanent magnets. The collector has a small footprint of the size 12”x3”x6” and ran on a battery pack. The collector built on the HGPMS principle is highly selective toward particles comprising of paramagnetic and ferromagnetic composition[7], which eliminates significant downstream effort in preparing the same for composition analysis. Results from detailed model analysis and experimental measurement on the magnetic circuit reveal the existence of localized structures in the magnetic field density distribution. Time-resolved fluorescence data show that aerosol particles were rapidly captured by the structures, not by the peripherals of the magnetic circuit. For ferromagnetic particles of 50 nm or larger in size, the HGPMS technology would collect the particles with nearly 100% efficiency. The efficiency decreases following the decrease of particle size. The harvesting efficiency of the HGPMS technology appears to be primarily dependent on the particle magnetic moment instead of particle mixing. The internal instead of external makeup of the aerosol particle population determines the separation efficiency of the HGPMS collector.