Consecutive Organosolv and Alkaline Pretreatment: An Efficient Approach toward the Production of Cellulose from Rice Straw.

The efficient removal of silica from rice straw and separation of its major components is essential for further valorization to produce value-added products. With regard to this, the isolation of cellulose (CEL), hemicellulose (HEM), and lignin (LIG) is imperative but quite challenging. Among several pretreatments of lignocellulosic biomass, the organosolv approach is deemed as one of the promising methods. Here, we present two different two-step approaches for the removal of silica and disintegration of significant components from rice straw, especially CEL; (i) base pretreatment, followed by organosolv treatment in the presence of organic acid, and (ii) organosolv pretreatment in the presence of organic acid, followed by base treatment. After each treatment, the recovered solid components are confirmed by various characterization techniques such as Fourier-transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and thermogravimetric analysis. Method 2 demonstrates 82% total removal of HEM and LIG along with 90.4% of silica removal from rice straw to obtain CEL. Furthermore, the obtained crude CEL is found to be with a purity of 78%. Excellent removal of silica (90.4%) reflects that in a test study, the crude CEL obtained from method 2 gives a higher yield of butyl glucosides (59.6%) than rice straw, which affords 45.0% of butyl glucosides.