Process Intensification Technologies Assisted Deep Eutectic Solvent Pretreatment for Fractionation of Lignocellulosic Biomass: A Review

Abstract

Lignocellulosic biomass pretreatment has become a prerequisite for the efficient conversion of lignocellulosic components into high-value chemicals and materials as sustainable alternatives to fossil-based products. In recent years, deep eutectic solvents (DES) have emerged as promising green and versatile solvents for biomass fractionation. However, their relatively limited treatment efficiency and the necessity for multi-component recovery have driven the development of intensified DES pretreatment strategies. This review first briefly summarizes the performance of various DES systems when applied alone to biomass pretreatment, and then systematically highlights recent advances in intensified technologies integrated with DES processes. These intensification strategies include physical approaches, such as microwave irradiation, ultrasonic treatment, pulsed electric fields, and mechanical activation, as well as chemically driven processes, including hydrothermal treatment, steam explosion, and catalyst-assisted DES pretreatment. The advantages, limitations, processing outcomes, and underlying mechanisms of these strategies are comparatively analyzed. To reduce the overall cost and environmental footprint of DES-based processes, current developments in DES recovery technologies are comprehensively reviewed. Finally, the existing challenges and future perspectives are discussed to provide guidance toward the development of efficient and sustainable DES-based biomass pretreatment technologies.