Modulation of Acid Hydrolysis Reaction Time for the Extraction of Cellulose Nanocrystals from Posidonia oceanica Leaves

In this research, the revalorization of Posidonia oceanica leaf sea waste was studied and the acid hydrolysis processing times were modulated in order to optimize the extraction of cellulose nanocrystals (CNCs). The obtained CNCs were deeply investigated. A two-step treatment was applied to extract cellulose nanocrystals from Posidonia oceanica leaves. First, a chemical treatment leads to the removal of lignin and production of holocellulose, while the second chemical process of acid hydrolysis allows the obtainment of cellulose nanocrystals in aqueous suspension. The unbleached and bleached leaves and cellulose nanocrystals were characterized by using thermogravimetric analysis, infrared spectroscopy and morphological investigation; the birefringence properties were also studied in order to determine the efficiency of the acid hydrolysis treatment. Cellulose nanocrystals were successfully obtained from Posidonia oceanica leaves and they showed a monocrystalline rod-shaped acicular structure with a 5–10 nm diameter and 200–450 nm length.