Impact of eco-friendly chemical pretreatment on physicochemical and surface mechanical properties of sustainable lignocellulosic agricultural waste

Abstract

This research aimed to investigate the impact of glycerol (Gly) and choline chloride (ChCl) pretreatments on physico-chemical and mechanical properties of rice husk (RH) at a submicron scale. Gly (75 wt%) and ChCl (25 wt%) were used to pretreat RH at 110 °C for 4 h in a water bath (150 rpm). Physico-chemical and surface mechanical (elastic modulus and hardness) properties of treated RH were determined and compared with untreated ones. The impacts of Gly and ChCl pretreatments on RH, surface morphology, structure, thermal stability, elastic modulus, and hardness were investigated using scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), x-rays diffractometry (XRD), thermogravimetric analysis (TGA) and nanoindentation technique, respectively. Experimental results depicted that pretreatment of RH with Gly and ChCl produced cellulosic-rich fiber, increase crystallinity, and enhanced thermal stability. In contrast to the untreated (35 %) RH, the ChCl and Gly-treated RH had cellulose contents of 49 % and 45 %, respectively. The degree of crystallinity was increased after the treatment of RH with 37 % and 35 % in ChCl RH, respectively, as compared to the untreated one. Elastic modulus and hardness of ChCl-treated RH were decreased by 67 % and 70 %, respectively, compared to the untreated one. Similarly, reductions in elastic modulus and hardness were noted in the case of Gly treatment. According to current research, lignocellulosic biomass can be pretreated with green solvents to produce cellulosic-rich fiber for engineered composite applications.