Targeted Functionalization of Waste Lignocellulosic Biomass to Produce Sound Absorbing Materials

Abstract Among the most abundantly available bioresources, lignocellulosic biomass offers a ‘green renewable’ alternative resource for producing high-value biomaterials suitable for acoustical applications. In this study, a systemic process is developed to fabricate sound absorbing material using refined cellulosic microfibrils generated from natural deep eutectic solvent (NADES) pretreated rice straw. Physico-chemical characterization using FTIR and FESEM analysis confirmed substantial removal of the hemicellulose and lignin from the extracted cellulosic microfibrils. Moreover, the surface area after NADES pretreatment increased to 12.55 m2/g from 2.18 m2/g of raw rice straw, suggesting the enhanced potential of sound dissipation within the biomaterial. The noise reduction coefficient (NRC) of the NADES pretreated rice straw is increased to 0.55 compared to 0.41 with untreated rice straw. Sound absorption performance shows an increasing trend with the increase in sample thickness (25 mm to 50 mm); however, no significant improvement in sound absorption is observed with an air gap of more than 20 mm. Overall, the tested biomaterial shows comparable NRC to commercially available synthetic sound absorbing materials.