Extracting soluble lignin from poplar sawdust via ternary cetyltrimethylammonium bromide-based deep eutectic solvent pretreatment for the fabrication of biodegradable films

The multi-component deep eutectic solvents (DES) have emerged as indispensable tools in the lignocellulosic pretreatment process, facilitating the efficient biotransformation of biomass sugars into valuable products. In this investigation, FeCl 3 was ingeniously incorporated to amplify the pretreatment efficacy of a DES synthesized from cetyltrimethylammonium bromide (CTAB) and lactic acid (LA), specifically targeting poplar sawdust (PS). Remarkably, under the meticulously optimized molar ratio of 1: 4:1, this innovative ternary DES achieved an unprecedented removal of 68.2 % lignin and 99.9 % xylan from PS, thereby elevating the enzymatic hydrolysis efficiency from a modest 16.8 % to an impressive 78.9 %. Structural characterization unveiled that the strategic introduction of FeCl 3 into the CTAB:LA system not only enhanced the accessibility and crystallinity index of PS but also diminished the surface area occupied by lignin, effectively dismantling the intricate linkages and structural units of dissolved lignin. As a result, high-performance films imbued with UV resistance and antioxidant properties were successfully fabricated through the judicious blending of dissolved lignin with polylactic acid. This pioneering research not only underscores the unparalleled delignification prowess of CTAB as the most efficacious hydrogen bond acceptor in DES but also establishes a robust theoretical framework for the high-value utilization of ternary DES in biorefinery applications.