Ultrasonic Delignification and Microstructural Characterization of Switchgrass

Abstract

This present study was undertaken to investigate the ultrasonic delignification of switchgrass (Panicum virgatum L.) and the effects of ultrasonic irradiation on the molecular and microstructure of switchgrass. We investigated this question using response surface methodology (RSM) featuring a four-factor, three-level Box–Behnken experimental design with acoustic power (120, 180, and 240 W), solid–solvent ratio (1/25, 1/20, and 1/15 g/mL), hammer mill screen size (1.6, 3.2, and 6.4 mm), and sonication time (10, 30, and 50 min) as factors, while delignification (%) was the response variable. The native and treated switchgrass samples were further characterized through crystallinity measurements and electron microscopy. The results of lignin analysis show that the percent delignification ranged between 1.86% and 20.11%. The multivariate quadratic regression model developed was statistically significant at p < 0.05. SEM and TEM micrographs of the treated switchgrass grinds resulted in cell wall disruption at the micro- and nano-scales. XRD analysis revealed a reduction in the mean crystallite size and crystallinity index from 15.39 to 13.13 Å and 48.86% to 47.49%, respectively, while no significant change occurred in the d-spacings. The results of this investigation show that ultrasonic irradiation induces chemical and structural changes in switchgrass, which could enhance its use for biofuel and bioproducts applications.

Efficiency of ultrasonic pretreatment on improving biodegradability of tomato wastes: A hypothetical analysis of waste conversion to biohydrogen

“…As found, term 𝑥𝑥 1 𝑥𝑥 2 𝑥𝑥 4 2 in the equation had the largest coefficient, indicating that a high ultrasonic power was suitable to increase bio-H2 production. These results were in line with those reported in the literature (Gadhe et al 2014;Arun and Sivashanmugam 20018;Olughu et al 2021). They reported that the ultrasonic pretreatment effectively enhances the biodegradability of complex materials, and thus, favors increased biohydrogen recovery.…”

Intensification of alkaline delignification of sugarcane bagasse using ultrasound assisted approach

“… Pretreatment Method Lignocellulosic biomass Optimized reaction Conditions Delignification (%) Reference Ultrasound + alkali Sugarcane bagasse 400 W power, 24 kHz Frequency, 100% duty cycle, time 50 min, 70˚C temperature, 1 M alkali concentration 92 [5] Only US switchgrass Power 180 W, Frequency 24 kHz, time 50 min, Solvent used as distilled water, 90% duty cycle. 21 [54] Only Alkaline Pretreatment Sugarcane bagasse 1 N alkali concentration, 100˚C temperature, 1 bar pressure, Time 45 min. 58 [55] US + Alkali pretreatment News paper 100 W power, 20 kHz frequency, 1 alkali concentration, 80% Duty cycle, 70 min time, 80 ˚C temperature.…”

Comparative Study on Quality of Fuel Pellets from Switchgrass Treated with Different White-Rot Fungi

“…Among the independent variables considered in this study, the hammer mill screen size showed no significant impact on any of the response variables. This could be connected to the slight differences in the geometric mean diameter of the switchgrass grind milled with the different hammer mill screen sizes selected in this study, as reported in a previous study [29]. However, the interaction effect of the hammer mill screen size and inoculum concentration on the pellet unit density and tensile strength of pellets from PC-and TV52J-pretreated switchgrass was statistically significant.…”

“…The switchgrass samples collected were pre-chopped and stored in plastic bags. The switchgrass samples were comminuted using a hammer mill to three different screen sizes (6.4, 3.2 and 1.6 mm) and then stored in air-tight polyethylene bags as described in our previous study [29].…”

“…The variation in the cellulose and hemicellulose content of the m4D-and PC-treated samples could be related to their inherent enzymes. The deficiency in cellobiose dehydrogenase in m4D reduced its ability to hydrolyze the holocellulose [22,29], and the apparent increase in cellulose content upon treatment with m4D could be due to the release of glucose from the fungal cell wall upon acid treatment. In contrast, PC simultaneously degraded lignin and holocellulose; while apparent cellulose content decreased with PC treatment, it is likely that even more of the cellulose was actually degraded by the fungus because of the release of glucose from the fungal cell wall upon acid treatment.…”