Adsorption of nanoparticles with sub-10 nm sizes close to gases on porous materials has been a long-existed and unrevealed issue in the gas separation field. Large adsorbates up to nanometers, such as proteins, dyes and aggregations, can be found in aqueous adsorption processes but in gaseous cases where they, if exist, are habitually subsumed into low-volatile and nano-sized nanoparticles. It has been gradually found the intrinsic adsorption mechanism of trapping airborne nanoparticles by porous filters embodies great scientific significance. Recent studies dealing with PM<sub>2.5</sub> using activated carbons, nanofiber-coated window screens, and MOFs-coated filters have shown great functions of porous structure in trapping particles, and its lack of being considered in conventional prediction of filtration efficiency at nanometer range. On the other hand, tiny nanoparticles behaving like gas molecules could easily diffuse deep into porous networks, which influences adsorbent characteristics in practical gas separations and thus needs theoretical directions for protections.  Herein, we demonstrate the adsorption phenomena of nanoparticles by conducting the removal efficiency test on conventional FAU zeolites with different ion-exchanged cations, and mesoporous adsorbents with different morphologies including CMK-3, CMK-5, KIT-6, and SBA-15 with primary pore sizes ranging from 5.8 to 17.8 nm. The results show the difference between efficiency data and those predicted by Brownian diffusion theory, and the variation rule of efficiency curves with adsorbent properties. The effects of morphologies, pore size distributions and ion exchange properties on nanoparticle capture are explored in details based on material characterizations, adsorption theories and molecular simulations. A discussion on the bridge between gas adsorption and aerosol filtration at a transition size range is also given.

Adsorption phenomena and related mechanisms of airborne nanoparticles on porous materials

256th National Meeting (2018)

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