2.2.2. Extraction of cellulose nanocrystals
After the chemical treatment was completed, the TCC was milled
with a blender and passed through a 35-mesh screen and then
used for the extraction of nanocrystals by acid hydrolysis. The
hydrolysis was performed at 45 ◦C for 30 min or 60 min or 90 min
under vigorous and constant stirring. For each gram of TCC, we
used 15 mL of H2SO4 9.17 M. Immediately following the hydrolysis,
the suspension was diluted 10-fold with cold water to stop
the hydrolysis reaction, and centrifuged for 10 min at 7500 rpm to
remove the acid excess. The precipitate was then dialyzed with
tap water to remove non-reactive sulfate groups, salts and soluble
sugars, until the neutral pH (∼4 days) was reached. Subsequently,
the resulting suspension of dialysis process was ultrasonicated for
10 min and stored in a refrigerator at 4 ◦C. Some drops of chloroform
were added as protectant to the CNC suspension. The cellulose
nanocrystals of the corncob were labeled CNC30 or CNC60 or CNC90,
depending on the time of extraction.