Probe sonication assisted ionic liquid treatment for rapid dissolution of lignocellulosic biomass

Abstract

The dependence on fossil fuel in recent years has accentuated the importance of renewable resources such as biomass. Lignocellulosic biomass consisting mainly of cellulose, hemicellulose, and lignin, can be potentially converted into biochemicals and biofuels. Ionic liquid (IL) has been proven as an efficient and green solvent for biomass dissolution and further processing. Nonetheless, conventionally employed IL treatment requires a longer time and higher temperature making the overall process cost-intensive and time-consuming. The aim of the current research work is to develop a direct probe sonication assisted IL method for rapid biomass dissolution without any external heating. The effect of several experimental parameters on biomass dissolution such as acoustic power (20–60%), sonication time (10–70 min), biomass particle size (500–125 µm), initial sample loading (5, 7.5 and 10%), volume of sample (3, 6 and 9 mL), and types of IL were investigated and optimized. The lignocellulosic biomass and regenerated biomaterials were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, Fourier electron scanning electron microscope, and powder x-ray diffraction to study the effect of probe sonication assisted IL treatment. The ultrasonic cavitation had significantly shortened the time for complete lignocellulose dissolution and considerably altered the thermophysical properties of regenerated cellulose-rich materials. The acetate-based IL showed the best performance, able to fully dissolved bamboo biomass in just 40 min in the probe sonication. In conclusion, probe sonication is an efficient method at lab scale which might need further development in technology to make the process economical at the industrial level for lignocellulosic biomass treatment.