Simple freeze-drying of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) dispersions in water/tert-butyl alcohol (TBA) mixtures was conducted to prepare TOCN aerogels as high-performance air filter components. The dispersibility of the TOCNs in the water/TBA mixtures, and the specific surface area (SSA) of the resulting TOCN aerogels, was investigated as a function of the TBA concentration in the mixtures. The TOCNs were homogeneously dispersed in the water/TBA mixtures at TBA concentrations up to 40% w/w. The SSAs of the TOCN aerogels exceeded 300 m2/g when the TBA concentration in the aqueous mixtures was in the range from 20% to 50% w/w. When a commercially available, high-efficiency particulate air (HEPA) filter was combined with TOCN/water/TBA dispersions prepared using 30% TBA, and the product was freeze-dried, the resulting TOCN aerogel-containing filters showed superior filtration properties. This was because nanoscale, spider-web-like networks of the TOCNs with large SSAs were formed within the filter.

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All-cellulosic materials called vulcanized fibers, in which cellulose fibers are gelatinized and adhered to each other by zinc chloride, have been known for more than 150 years. However, the swelling and adhesion mechanisms have not yet been clarified. In this study, X-ray diffraction, scanning electron microscopy (SEM) ，and specific surface area(SSA)analyses of cellulose sheets treated with different concentrations of aqueous zinc chloride solutions were performed to elucidate the behavior and mechanism of cellulose fibers adhering to one another during ZnCl 2 treatment. The X-ray diffraction analysis revealed that the ZnCl 2 treatment caused swelling of intercrystalline regions but did not significantly change the original crystal structure of cellulose I. The SEM observation of the freeze-dried sheets revealed less aggregated structures of the fine fibers and the existence of three-dimensionally entangled cellulose nanofibrils(CNFs)between the cellulose microfibers. The increased SSA values of the freeze-dried sheets supported the formation of CNFs during the ZnCl 2 treatment. These results indicate that in these all-cellulosic materials, CNFs are entangled and form dense networks that are not completely detached in water. In addition, the presence of moisture leads to more viscoelastic behavior as a result of slip between the CNFs during tensile testing.