Physicochemical characteristics of cellulose nanocrystals isolated from seaweed biomass

Cellulose nanocrystals (CNCs) were successfully isolated from marine biomass of brown, red, and green seaweeds by a four step process of de-polymerization, bleaching, acid hydrolysis, and mechanical dispersion. Chemical composition, yield, and density were determined for each seaweed group and compared to other cellulose sources. Morphological analysis was performed by transmission electronic microscopy (TEM) and showed that CNCs from seaweed showed rod shape particles 21–248 nm length and 4.8–41 nm width. The obtained aspect ratio was varied from 2.5 to 15. Fourier transform infrared spectroscopy (FTIR) analysis was performed to investigate chemical structure of CNCs from seaweeds, which revealed obtained crystalline cellulosic from the extraction process. X-ray diffraction (XRD) data showed the main crystalline structure of CNCs was cellulose I in all cases. The crystalline index increased about 21.5% going from cellulose to CNCs. The thermal properties of untreated seaweeds, extracted cellulose, and CNCs were compared by thermogravimetric analysis (TGA). The onset thermal decomposition (T_on) increased in all cases and weight loss changes significantly decreased during the extraction process except Sargassum fluitans, indicating the thermal stability of CNCs.