Synthesis and characterization of cellulose nanocrystals extracted from sago (Methoxylon sagu) pulp

Sago (Metroxylon sagu) pulp is a common agricultural product; however, its pulp (from the main plant part and bark) finds no essential use and is considered agricultural waste. In this study, cellulose nanocrystals (CNCs) were isolated from the main pulp and bark pulp of sago through bleaching, alkali treatment, and acid hydrolysis. The hydrolysis was performed with 64% (w/w) sulfuric acid. A considerable yield was obtained for the extracted CNCs, 65.36% for sago main pulp (SMP), and 77.43% for sago bark pulp (SBP), which are comparable to other previous reported protocol. FTIR analysis of the resulting CNCs showed similar vibration frequencies with α-cellulose. Concerning the spherulites, considerable size reduction was revealed in the Scanning Electron Microscopy (SEM) analysis after acid hydrolysis of α-cellulose to obtain CNCs. Importantly, an image from the Transmission Electron Microscope (TEM) showed bundles of the needle-like structure of the extracted CNCs, which is a characteristic image of the CNCs after hydrolysis. Thermogravimetric analysis (TGA) also revealed the stability of the CNCs. Elemental analysis via EDX showed that the two forms of nanocellulose from the derived CNCs possessed mostly carbon and oxygen. The small amount of α-cellulose obtained (3-8%) was attributed to the degradation of α-cellulose, which may have been caused by the alternative bleaching process employed. Despite this, a reasonably good percent yield for CNCs was extracted, demonstrating sago pulp's potential as a useful source of this cellulosic nanomaterial.