Native
cellulose nanofibers (CNF) constitute an abundant resource
for pyrolysis leading to char materials offering a wide range of properties
and application possibilities. With the aim to produce chars having
large surface area and pore volume for dyes adsorption and oil absorption,
respectively, we herein explore the slow pyrolysis process of cellulose
nanofibers from wood, Cladophora algae
and bacteria that were subjected to various drying routes. Whereas
algae CNF with their large crystallites lead to high surface area
(S
BET) substrates using conventional drying
from aqueous suspension, CNF from wood having smaller crystallites
requires drying from solvents to reach high S
BET substrates, which results in chars with a good adsorption
capacity for both anionic and cationic dyes. Moreover, the porosity
of the CNF substrate can be tuned via an ice-templating freeze-drying
procedure reaching values as high as 99.7% and corresponding chars
capable of absorbing 64–120 g g–1 of various
oils and organic solvents. Besides the absorption/adsorption properties
of the chars, we report effects of CNF source and structure on the
thermal properties assessed by thermogravimetric and thermomechanical
analyses, differential scanning calorimetry, and mass spectrometry,
and we identified over 20 decomposition products and 3 expansion events
occurring during CNF pyrolysis.
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