(751a) Filtration of Multi-Component Aerosols Using Polymeric Nanofiber Membranes

Aerosols are known to pose a threat to both human health and the environment. Submicron aerosols are abundant, hazardous, and difficult to remove. Among various particle control technologies, filtration is the most economical method for removing submicron aerosols. Most real-life aerosols, including tobacco smoke, coal gas, and combustion products, are complex in composition and exhibit compositional heterogeneity. For example, the distribution of toxic components in cigarette smoke has been shown to vary with particle size. Despite the ubiquity of multi-component aerosols, model filtration studies tend to be performed on single-component aerosols. These studies give meaningful insights into the effects of filtration on aerosol concentration and size distribution, but do not address whether or how the filtration process affects the composition of the aerosol stream. In our work, we aim to understand the effects of filtration on the chemical composition of submicron liquid aerosols and to explore the possibility of achieving chemical selectivity through filtration. We have performed filtration tests on binary liquid aerosols using polymeric nanofiber filters of different fiber sizes, and our results demonstrate that preferential filtration of specific components can be achieved through adjusting the structure and properties of the nanofiber filters.

The filters used in this work were fabricated using the electrospinning technique. Nanofiber membranes have low basis weights, large surface to volume ratios, and are thus great candidates for submicron aerosol filtration. Filters comprising fibers with diameters ranging from 300 nm to 1 μm were produced and tested in filtration experiments.

Binary liquid aerosols consisting of bis(2-ethylhexyl) sebacate (DEHS) and bis(2-ethylhexyl) phthalate (DEHP) were generated and used as model bi-component aerosols. The size and compositions of these aerosols were controlled by adjusting conditions in the condensation monodisperse aerosol generator (CMAG). The size distribution of aerosols was measured with a differential mobility analyzer (DMA) paired with a condensation particle counter (CPC). The chemical composition was obtained from GC-MS measurements.

Results of our filtration experiments show that the both the particle size distribution and the composition of the aerosol stream change from upstream to downstream of the filtration process, and that the magnitude of these changes depends on the average fiber diameter in the filter. The magnitude of the compositional change also correlates with that of the change in size distribution of the aerosols. Our results demonstrate that, for compositionally heterogeneous aerosols, filtration serves not only as means for removing particles from a gas stream, but can also be used as a chemical separation process, resulting in the selective removal of certain chemical components. This study provides valuable insights into both the filtration mechanism of submicron particles and the possibility of designing chemical separation processes for aerosols through filtration with nanofiber membranes.