Moisture-coupled aerosol filtration in moss-based porous media: enhanced particle capture and aerodynamic resistance trade-off

초록

This study investigated moisture-coupled submicron aerosol filtration in moss-based porous media under dry and wet conditions. Four moss filter configurations composed of Sphagnum and Hypnum plumaeforme were evaluated using NaCl aerosols with particle diameters of 22–540 nm at face velocities of 1.2, 1.5, and 1.8 m s⁻1. The dry moss filters exhibited characteristic U-shaped efficiency curves with MPPS values in the approximately 200–300 nm range, indicating size-selective filtration behavior similar to conventional porous fibrous filters. Among the tested configurations, the dry Sphagnum-based filter showed the highest performance, achieving an average filtration efficiency of 59.1% at 1.2 m s⁻1. Retained moisture enhanced particle capture in all moss filters by modifying effective collector geometry, particle–surface adhesion, and internal flow pathways. However, this enhancement was accompanied by a substantial increase in pressure drop, leading to lower quality factor values under wet conditions. Benchmarking against commercial filters showed that the dry Sphagnum filter achieved an average efficiency comparable to MERV 13, but with a much higher pressure drop. These results demonstrate that moss-based media can provide competitive submicron particle capture, while their practical performance is constrained by an efficiency–resistance trade-off arising from moisture-coupled transport in a heterogeneous biological porous medium. The results represent the initial performance of freshly prepared media, while the limitations regarding structural characterization, long-term loading, and biological stability are discussed to guide future development.

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