When increasing the acid-to-pulp ratio from 8.5 ml/g to 9.5 ml/g,
the mean particle size of NCC samples obtained was 5.1 nm
smaller. It was reported that larger volume of acid used tend
to hydrolyze a given amount of pulp faster and thus yielded
shorter rods in a given hydrolysis time, probably because some
imperfect crystalline region was hydrolyzed at higher acid-topulp
ratio. It should be noticed that, when the acid-to-pulp ratio
increased further to 10.5 ml/g, the shape of the NCC samples
turned to be spherical, with a very small diameter of 3.38 nm.
Nadanathangam and Satyamurthy [29] obtained spherical nanocellulose
from microcrystalline cellulose by controlled hydrolysis
using anaerobic microbial consortium, which diameter was several
hundred nanometers. It was also reported that a process, including
a pretreatment with NaOH and dimethyl sulfoxide (DMSO), and
then hydrolysis with HCl and H2SO4, could gave spherical cellulose
nanoparticles [30].