Extraction and characterization of cellulose nanocrystals from agro-industrial residue – Soy hulls

Soy hulls are an agro-industrial residue available in huge quantities throughout the world whose application deserves more attention than simply as cattle feed. This work evaluates the use of soy hulls as a source of cellulose to obtain nanocrystals by acid hydrolysis. The hydrolysis was performed at 40 °C for 30 or 40 min, using 30 mL of H2SO4 64% for each gram of cellulose. The resulting nanocrystals were characterized by crystallinity index, morphology, surface charge and thermal stability. The results showed that the more drastic hydrolysis conditions (40 min) resulted in a shorter length of nanocrystals and caused some damage on the crystalline structure of the cellulose. At an extraction time of 30 min, the nanocrystals presented a high crystallinity (73.5%), an average length of 122.66 ± 39.40 nm, a diameter of 2.77 ± 0.67 nm and an aspect ratio around 44, therefore presenting a great potential as reinforcement in nanocomposite preparations.

► Cellulose nanocrystals (CWs) can be isolated from soy hulls.
► Longer extraction time resulted in a shorter length of CWs.
► CWs presented a needle-shaped nature, with high crystallinity, good thermal stability, giving an aspect ratio (L/D) around 44.
► CWs obtained from soy hulls have great potential to be used as reinforcement agents for the manufacture of nanocomposites.