10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Aerosolization and Characterization of Cellulose Nanomaterials
BON KI KU, M. Eileen Birch, G.J. Deye, Centers for Disease Control and Prevention, NIOSH
Abstract Number: 223 Working Group: Health Related Aerosols
Abstract Cellulose nanomaterials (CN) are emerging materials of interest for the forestry, paper, and pulp industry. The various forms, including cellulose nanofibers (CNF), micro fibrillated cellulose, and cellulose nanocrystals (CNC), can be produced from wood pulp and other biomass. While potential applications for these promising nanomaterials are emerging, particularly in the fields of sustainable materials and nanocomposites, the health and safety aspects of these varied products have not been fully studied, mainly due to the lack of relevant exposure data for workers. Microscopy analyses are useful for characterization of morphology and structure of CN, but they are not quantitative, and other methods have not been established/evaluated for monitoring worker exposure to these materials. Thus, method development, for both sampling and measurement, is needed to fill this knowledge gap. As part of this research effort, it is important to investigate a variety of bulk CN, including the CNC form, to determine: 1) the potential for aerosolization, 2) particle residence time in air, and 3) particle size distributions of the generated aerosols. We are, therefore, in the process of characterizing a number of CN to assess these properties. In this study, we investigated the aerodynamic characteristics of aerosolized CN powders.
Aerosols from bulk CN (i.e., CNC form, provided by Forest Products Laboratory, Madison, WI) are being generated in a controlled manner, to produce target concentrations and examine particle size distributions. Dry dispersion of CNC bulk powders is accomplished using an acoustic generator (AG) [Ku and Birch, 2015] and/or a vortex shaking technique (Ku et al., 2013). Airborne particle properties such as mobility and aerodynamic diameters were measured using mobility particle and aerodynamic particle sizers, and particle morphology was examined using optical or electron microscopy.
Preliminary results showed that aerosolized CNC particles have aerodynamic size distributions with a geometric mean diameter of about 1.5 µm and size range up to about 8 µm. In addition, the CNC particles were found to have a geometric mean mobility diameter of about 450 nm. The results indicate that the potential for aerosolization and a long residence time in air are expected to be high, calling for further characterization and development of reliable monitoring methods for these materials.
Acknowledgments We thank Dr. Alan Rudie at Forest Products Laboratory for kindly providing cellulose nanomaterial samples for our research. This work was funded by the National Institute for Occupational Safety and Health through the Nanotechnology Research Center (NTRC) program (CAN 93908N0).
References Ku, B.K. and M. Eileen Birch (2015). Aerosolization of Carbon Nanotubes Using an Acoustic Generator: Particle Generation and Properties. The 2015 Nanotech Conference, June 14-17, 2015, Washington, DC. http://www.techconnectworld.com/Nanotech2015/sym/Sustainable_Nanotechnology_Environmental_Apps_EHS_Implications.html Ku, B.K., Deye, G., and Turkevich, L.A (2013). Characterization of a Vortex Shaking Method for Aerosolizing Fibers. Aerosol Science and Technology, 47:12, 1293-1301, https://doi.org/10.1080/02786826.2013.836588.
Disclaimer The mention of any company or product does not constitute an endorsement by the Centers for Disease Control and Prevention. The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.