Effects of Modified Activated Carbon on Microwave-Accelerated Organosolv Fractionation of Rice Husk

Abstract

Organosolv fractionation is a promising approach for the separation of lignocellulosic components in integrated biorefineries where each component can be fully valorized into valuable platform chemicals and biofuels. In this study, microwave-accelerated organosolv fractionation was developed for the modification of lignocellulosic fractionation of rice husk. The fractionation condition was optimized for 1 h with the microwave irradiation at 300 W using a ternary solvent mixture composed of 24%:32%:44% water/ethanol/methyl isobutyl ketone. The effects of mineral acids (HCl, H3PO4, and H2SO4) and heterogeneous acid promoters (HCl, H3PO4, and H2SO4 impregnated over activated carbon) on the efficiency and selectivity of product yields (i.e., glucan, hemicellulose-derived products, and lignin) were also investigated. It was found that the use of H3PO4-activated carbon as the promoter showed superior performance on the fractionation of rice husk components, resulting in 88.8% recovery of cellulose, with 63.8% purity in the solid phase, whereas the recovery of hemicellulose (66.4%) with the lowest formation of furan and 5-hydroxymethyl furfural and lignin (81.0%) without sugar cross-contamination was obtained in the aqueous ethanol phase and organic phase, respectively. In addition, the morphology structure of fractionated rice husk presented 2.6-fold higher surface area (5.4 m2/g) of cellulose-enriched fraction in comparison with the native rice husk (2.1 m2/g), indicating the improvement of enzyme accessibility. Besides, the chemical changes of isolated lignin were also investigated by Fourier-transform infrared spectroscopy. This work gives pieces of information into the efficiencies of the microwave strategy as a climate neighborly elective fractionation method for this serious starting material in the biotreatment facility business. ©