Preparation And Properties Of Sugar Beet Pulp Cellulose Nanofibrils

Sugar beet pulp(SBP), a byproduct of sugar industry, is abundant, low cost and renewable. The thin cell wall of SBP contains a lot of natural polymer such as pectin,cellulose and hemicellulose.SBP is mainly used as cattle fodder or the raw material to extract pectin currently.The added value of fodder is so low and the gelation ability of pectin is so poor.After extracting pectin, lots of cellulose is discarded,causing huge waste of resources.The cellulose originates mostly from the sugar beet thin walled parenchymal tissues. The cellulose nanofibrils(CNF) are loosely organized network and embedded into pectin, hemicellulose.and lignin.So it’s easier to individualize CNF compared with other woody fibers.In this paper, SBP was pretreated by clean and effective steam explosion.The technological conditions of steam explosion was discussed.The effect of steam treatment and explosion treatment on the chemical composition and structures of SBP were also analyzed. After treated with steam under high temperature and high pressure,the pectin in the cell wall become watersoluble,hemicellulose hydrolysis into polysaccharide.When the pressure was released,pectin migrated from inner cell wall to outside.Then the CNF network appeared on the surface.In order to fully utilize SBP source, pectin can be recovered with ethanol from the steam explosion liquid.The chemical structure,thermal properties, crystallization behavior and morphology were characterized by Fourier transform infrared spectroscopy(FTIR), Thermo gravimetric analysis(TG), X-ray diffraction(XRD) and Field emission Scanning electron microscopy(FESEM).The optimal pretreatment condition was selected to prepare CNF, namely temperature 220℃, heating time 35 min, steam explosion for twice.Cellulose nanofibrils were successfully fabricated from SBP using two different method,fully mechanical method or H2O2 bleaching. The morphology, chemical structure, crystallization and thermal properties of two kinds of nanofiber were characterized.In the mechanical method, steam exploded SBP was treated with high-shear homogenization and high-intensity ultrasonication.The whole preparation process is free of chemical reagents, which can alleviate the environmental pollution.The MFC obtained from this method formed a reticular structure.Large amounts of bundles were existed in the brown suspension.The diameters of MFC was 40 ~ 50 nm.The crystallinity and thermal degradation temperature of MFC reached 57.43% and 353.1℃,respectively. The H2O2 bleaching is free of chlorine.The preparation method is environmentally friendly because the resulting product is water. The CNF displayed a monodisperse diameter distribution.The diameters were concentrated in 10 ~ 20 nm. The crystallinity and thermal degradation temperature of CNF reached 62.30% and 346.4℃,respectively.The cellulose nanofibrils films were prepared by vacuum filtration, the wet gels were placed into the glass plate and dried in a pressurized molding. The surface and cross section morphology, optical and mechanical properties of cellulose nanofibrils films were characterized by Field emission Scanning electron microscopy(FE-SEM), UV-visible spectroscopy(UV-Vis) and Mechanics performance Testing. Then the comparison between cellulose nanofibrils films and ordinary A4 paper was carried out to explore more applications in the field of nanopaper.