Isolation and Characterization of Cellulose from Sweet Sorghum Bagasse

Sweet sorghum bagasse represents a potential low-cost biomass which can be valorized to produce different value-added lignocellulosic platform chemicals of economic importance. The focus of the present study is the pretreatment of sweet sorghum bagasse for efficient delignification, separation of pure cellulose and its structural characterization. Sweet sorghum bagasse was subjected to mechanical commutation followed by steam washing, organosolv extraction (methanol and toluene, 1:2) and alkaline hydrogen peroxide treatment for efficient delignification. Chemical analysis revealed that cellulose, hemicellulose and lignin content (per cent recovered) after different pretreatment was 720 g (98 %), 6 g (1.1 %) and 20 g (0.9 %), respectively. Structural characterization of untreated sweet sorghum bagasse and recovered cellulose was performed using FT-IR, CP-MAS 13C NMR spectroscopy, XRD, and thermogravimetric analyses. The cellulose preparation obtained after chemical pretreatments had typical cellulose structure with high crystallinity as compared to the untreated substrate. SEM micrographs revealed the surface topography wherein the waxy layer on the surface of this material disappeared and the texture became thinner and striated. The pretreatment methods employed were able to produce cellulose of high purity with >98 % lignin removal.