Simple Preparation of bagasse pith cellulose nanofibers and precise controlling their morphology

Abstract As one of the main by-products of the sugar industry, bagasse is widely used in pulp and paper industry because of its rich cellulose and a small amount of lignin. However, in addition to fiber cells, bagasse also contains about 30% soft, short pulp. And high silicon content in sugarcane pith will cause difficulty in black liquor recovery. Therefore, in the process of pulping and papermaking, pulp is often removed first. Obviously, this measure violates the principle of making full use of biomass resources. Under the premise of ensuring the efficient use of resources, the study of new technologies that are more environmentally friendly is an important measure to achieve the efficient use of sugarcane pulp waste. It is also highly consistent with the National Development and Reform Commission’s “14th Five-Year Plan” circular economy development plan on the “high-value utilization of agricultural and forestry biomass resources.” Based on this, this paper mainly studied the preparation of nanocellulose by low-temperature ethanol-oxygen-alkali technology of sugarcane pulp, and flexibly regulated the morphology of nanocellulose by changing the ratio of alcohol to water. The semi-liquefaction process behavior was analyzed from solid-liquid ratio, alkali pre-extraction and alcohol-water ratio. The physicochemical properties of nanocellulose and residue were analyzed by SEM, XRD and FTIR to capture the process of cellulose depolymerization. The results show that when the solid-liquid ratio is 1:8 and the alkali concentration is 60 g/L, the semi-liquefaction process of ethanol-oxygen-alkali system and the alkali pre-extraction effect are the best. The results of FTIR spectroscopy showed that with the increase of ethanol concentration, the structure of semi-liquefied solid was effectively destroyed, resulting in the degradation of lignin macromolecules and the significant increase of cellulose content. XRD analysis showed that the highest crystallinity of semi-liquefied solid was 68.75%. In addition, with the increase of ethanol concentration, the structure of the fibers gradually formed a uniformly distributed block structure. After the ultrasonic pretreatment process, the irregular aggregate fibers and block fibers were subjected to strong impact force to form granular fibers. After alkali extraction pretreatment, cellulose completed the transformation from irregular and large aggregates to small and uniformly distributed granular nanocellulose. In this paper, for the first time, the morphology of nanocellulose into flower-like, rod-like, spherical and ultrafine particles was simply and controllable regulated by ethanol-mediated method. By capturing the fibers with different morphologies in the process of cellulose depolymerization, the mechanism of preparing nanofibers from bagasse pith cellulose was inferred to achieve precise regulation of the morphology of cellulose nanofibers.