Extraction and characterization of cellulose nanowhiskers from Mandacaru (Cereus jamacaru DC.) spines

Cellulose nanowhiskers were extracted from the spines of Mandacaru (Cereus jamacaru DC.), a cactus native to the Caatinga biome of northeastern Brazil, using sulfuric acid hydrolysis preceded by alkaline treatment and bleaching. Results showed that three bleaching steps were required to remove most of the non-cellulosic constituents of the spines that yielded 77.4% cellulose. Nanowhiskers size decreased from about 400 to 260 nm when extraction time varied from 60 to 120 min, this was also evidenced by X-ray diffraction. Alkaline treated and bleached samples had lower thermal stability as compared to untreated spines due to removal of lignin and increased surface area. The amount of time samples were treated with sulfuric acid influenced the thermal stability and consequently the degree of crystallinity of the nanowhiskers. Cellulose nanowhiskers were obtained from Mandacaru spines providing a new renewable source of reinforcement with potential applications in nanocomposites.